A botanical mystery solved by phylogenetic analysis of botanical garden collections: the rediscovery of the presumed-extinct Dracaena umbraculifera

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A botanical mystery solved by phylogenetic analysis of botanical garden collections: the rediscovery of the presumed-extinct Dracaena umbraculifera
A botanical mystery solved by phylogenetic analysis
              of botanical garden collections: the rediscovery of
              the presumed-extinct Dracaena umbraculifera
                                          CHRISTINE E. EDWARDS, BURGUND BASSÜNER, CHRIS BIRKINSHAW
                                                              A N D R E W W Y A T T and P E T E R W Y S E J A C K S O N

              Abstract Extinction is the complete loss of a species, but the                         discoveries and the importance of documenting and con-
              accuracy of that status depends on the overall information                             serving the flora of Madagascar.
              about the species. Dracaena umbraculifera was described
                                                                                                     Keywords Botanical garden, Dracaena reflexa, Dracaena
              in  from a cultivated plant attributed to Mauritius, but
                                                                                                     umbraculifera, extinction, living collections, Madagascar,
              repeated surveys failed to relocate it and it was categorized as
                                                                                                     Mauritius, phylogeny reconstruction
              Extinct on the IUCN Red List. However, several individuals
              labelled as D. umbraculifera grow in botanical gardens, sug-
              gesting that the species’ IUCN status may be inaccurate. The
              goal of this study was to understand () where D. umbracu-                             Introduction
              lifera originated, () which species are its close relatives, ()
              whether it is extinct, and () the identity of the botanical
              garden accessions and whether they have conservation
              value. We sequenced a cpDNA region of Dracaena from
                                                                                                     E     xtinction is the complete and total loss of all individuals
                                                                                                           of a species. In practice, extinction can be defined as ‘the
                                                                                                     permanent absence of current and future records of a spe-
              Mauritius, botanical garden accessions labelled as D. um-                              cies’ (Ladle et al., ). Although this is a relatively straight-
              braculifera, and individuals confirmed to be D. umbraculi-                             forward concept, accurately determining and proving that a
              fera based on morphology, one of which is a living plant in a                          species is extinct is far from straightforward. Many species
              private garden. We included GenBank accessions of                                      may be presumed to be extinct, but whether this is actually
              Dracaena from Madagascar and other locations and recon-                                the case may depend on factors such as the amount and ac-
              structed the phylogeny using Bayesian and parsimony ap-                                curacy of historical data on a species’ distribution; the size of
              proaches. Phylogenies indicated that D. umbraculifera is                               its range and the density of its populations; how its range has
              more closely related to Dracaena reflexa from Madagascar                               changed over time; the ease with which it can be observed in
              than to Mauritian Dracaena. As anecdotal information in-                               the field; and the number of knowledgeable scientists
              dicated that the living D. umbraculifera originated from                               searching for it, the effort they expend in searching for it,
              Madagascar, we conducted field expeditions there and lo-                               and their overall knowledge of the biota of a region (Ladle
              cated five wild populations; the species’ IUCN status should                           et al., ; Lee et al., ). The most convincing evidence
              therefore be Critically Endangered because ,  wild indi-                             for extinction involves species that were once widespread
              viduals remain. Although the identity of many botanical                                and well known but then experienced an observable decline
              garden samples remains unresolved, this study highlights                               in range and population size, and cannot now be relocated
              the importance of living collections for facilitating new                              despite a relatively complete knowledge of the biota of the
                                                                                                     region and extensive, repeated surveys by qualified biolo-
                                                                                                     gists. If there is robust evidence for the extinction of a spe-
                                                                                                     cies, IUCN Red List working groups may determine it to be
                                                                                                     Extinct or Extinct in the Wild. A considerable number of
              CHRISTINE E. EDWARDS (Corresponding author), BURGUND BASSÜNER, PORTER
              P. LOWRY II*, JAMES S. MILLER, ANDREW WYATT and PETER WYSE JACKSON                     plant species are known to be Extinct in the Wild but still
              Missouri Botanical Garden, P. O. Box 299, St. Louis, MO 63166, USA                     persist in cultivation, mainly in botanical gardens.
              E-mail christine.edwards@mobot.org
                                                                                                         Dracaena umbraculifera (Asparagaceae sensu lato, Byng
              CHRIS BIRKINSHAW, CHRISTIAN CAMARA and ADOLPHE LEHAVANA, Missouri Botanical            et al., ) is an example of a plant species that is currently
              Garden, Madagascar Research and Conservation Program, Antananarivo,
              Madagascar                                                                             categorized as Extinct on the IUCN Red List (Strahm, ).
              *Also at: Institut de systématique, évolution, et biodiversité, Unité mixte de         To our knowledge it has never been observed by botanists in
              Recherche 7205 (Centre national de la Recherche scientifique/Muséum national           the wild and as a consequence has remained a mystery for
              d’Histoire naturelle/École pratique des Hautes études, Université Pierre et Marie      several centuries. Described in  by Nicolaus Joseph von
              Curie), Muséum national d’Histoire Naturelle, Sorbonne Universités, Paris,
              France                                                                                 Jacquin based on a plant cultivated in the greenhouses of the
              Received  June . Revision requested  September .                           botanical garden at Schönbrunn in Vienna (see Plate a for
              Accepted  October . First published online  January .                        original illustration, Jacquin, ), this species has a

              Oryx, 2018, 52(3), 427–436 © 2018 Fauna & Flora International doi:10.1017/S0030605317001570
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A botanical mystery solved by phylogenetic analysis of botanical garden collections: the rediscovery of the presumed-extinct Dracaena umbraculifera
428         C. E. Edwards et al.

                                                                                                                                                PLATE 1 (a) The original
                                                                                                                                                illustration of Dracaena
                                                                                                                                                umbraculifera from Jacquin
                                                                                                                                                (), (b) a paniculate
                                                                                                                                                inflorescence of Dracaena
                                                                                                                                                reflexa in Madagascar
                                                                                                                                                (photograph by
                                                                                                                                                P. Antilahimena, collection
                                                                                                                                                number ), (c) a diffuse
                                                                                                                                                paniculate infructescence of
                                                                                                                                                Dracaena floribunda in
                                                                                                                                                Mauritius (photograph by
                                                                                                                                                C. Edwards), (d) a young
                                                                                                                                                inflorescence of D.
                                                                                                                                                umbraculifera in Ile
                                                                                                                                                Sainte-Marie (photograph by
                                                                                                                                                Rova Malala Rakotoarivelo),
                                                                                                                                                (e) an inflorescence of D.
                                                                                                                                                umbraculifera in Ile
                                                                                                                                                Sainte-Marie in full flower
                                                                                                                                                (photograph by A. Lehavana),
                                                                                                                                                and (f) a vegetative individual
                                                                                                                                                of D. umbraculifera
                                                                                                                                                (photograph by P. Lowry).

                distinctive morphology, with tightly clustered flowers in a                            present in the current collections of the Pamplemousses
                nearly umbellate inflorescence in the centre of the leaves                             Botanical Garden (now the Sir Seewoosagur Ramgoolam
                (Plate a), differing from the diffuse, paniculate inflores-                           Botanical Garden).
                cences that characterize all other Dracaena (Plate b).                                    Dracaena umbraculifera was subsequently included in a
                Although Jacquin indicated that the cultivated plant on                                list of plants of Mauritius (Bojer, ) and described as
                which he based his description came from the island of                                 growing in the thick forests in the centre of the island and
                Mauritius (Jacquin, ), its origin is unclear. It may have                          flowering very rarely. It was also listed as a Mauritian species
                been collected during a voyage made by Franz Boos and                                  in the Flora of Mauritius and the Seychelles (Baker, ). In
                Georg Scholl, who sailed to South Africa and Mauritius dur-                            the more recent Flore des Mascareignes (Marais & Coode,
                ing – and sent back  cases of plants, assembled                             ), doubt was expressed about whether D. umbraculifera
                by M. Céré of the Pamplemousses Botanical Garden in                                    was native to Mauritius, as the main evidence that it existed
                Mauritius. However, there is no surviving documentation of                             in Mauritius was Bojer’s description. It was suggested that
                the plants contained in this shipment nor is it known whether                          Bojer may have confused D. umbraculifera with Dracaena
                they were all Mauritian natives. Dracaena umbraculifera is not                         floribunda, which still occurs in central Mauritius, and

                                                                                           Oryx, 2018, 52(3), 427–436 © 2018 Fauna & Flora International doi:10.1017/S0030605317001570
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Rediscovery of Dracaena umbraculifera                     429

              that if D. umbraculifera was indeed Mauritian it must be ex-                           from  botanical gardens in seven countries (Table ), as
              tinct. Following unsuccessful efforts over the previous cen-                           well as one cultivated accession of Dracaena reflexa from
              tury to locate living plants in the wild, the species was                              Missouri Botanical Garden. Individuals from botanical gar-
              categorized as Extinct in  (Strahm, ).                                         dens identified as D. umbraculifera but that are not con-
                  Despite the fact that no natural population of D. umbra-                           firmed by a flowering specimen are hereafter indicated in
              culifera has been documented in the wild in Mauritius, it                              quotes (i.e. ‘D. umbraculifera’). Although other gardens re-
              may not be extinct, as living plants labelled as D. umbracu-                           ported having individuals of D. umbraculifera, several flow-
              lifera have long been grown in botanical gardens around the                            ered recently and had diffuse-paniculate inflorescences,
              world. One such plant is growing at the Missouri Botanical                             confirming that they were incorrectly identified, and were
              Garden. This stimulated an interest in the true status of this                         not included in the study. Leaf material of a correctly iden-
              presumably extinct species and led us to initiate a study to                           tified, pressed specimen of D. umbraculifera was obtained
              try to elucidate its origins. The individual at Missouri                               from the University of Vienna herbarium (WU ;
              Botanical Garden was obtained in  from an unknown                                  Table ). It was prepared in  from a plant cultivated in
              source and, if correctly identified, the IUCN status of                                the Hortus Botanicus Vindobonensis (now known as the
              D. umbraculifera should be updated to Extinct in the                                   Botanical Garden of the University of Vienna), and has
              Wild (IUCN, ). Further research in the database of cul-                            the distinctive inflorescence of D. umbraculifera. Given
              tivated plants maintained by Botanic Gardens Conservation                              that Jacquin, who described D. umbraculifera, was the first
              International (BGCI, ) found  other gardens with living                          director of Hortus Botanicus Vindobonensis, we speculate
              individuals identified as D. umbraculifera. Communications                             that this specimen may have originated from the same
              with staff at these gardens indicated that most of these plants                        plant on which Jacquin based his description.
              have been in their collections for decades and their origins                               We also conducted fieldwork in Mauritius in January
              are unknown (other than in some cases in which they                                     to collect leaf tissue of all Dracaena species currently
              were obtained from other botanical gardens). As unequivo-                              known to be native to the island (Table ), including D. flori-
              cal morphological identification of these plants relies on the                         bunda, D. concinna and D. reflexa (including two of the
              presence of an inflorescence, yet they rarely, if ever, flower in                      three varieties of D. reflexa in Mauritius, var. reflexa and
              cultivation (the plant in Missouri Botanical Garden has not                            var. angustifolia). The collected tissue was preserved in silica
              been observed in flower for decades), the identity of these                            gel. During this trip, staff at Mauritius Herbarium informed
              specimens remains uncertain. It is important to determine                              us of an individual of D. umbraculifera growing in a private
              their identity because they may be the only remaining                                  garden on the island. This plant had flowered recently and
              individuals of a species that is otherwise extinct.                                    its identification was confirmed based on its distinctive,
                  Our goal was to unravel the mystery of D. umbraculifera                            umbel-like inflorescence. The herbarium staff provided
              and, in particular, to understand where it originated, which                           leaf tissue in silica gel, which was used as a reference for
              species it is related to, whether it is indeed extinct in the                          comparison with the samples obtained from botanical gar-
              wild, whether the living plants in botanical gardens are cor-                          dens. Although the wild origin of the plant was not indicated
              rectly identified and whether they are of conservation value.                          on the herbarium specimen, a web search found an online
              We gathered samples from living individuals labelled as D.                             posting by the plant’s owner indicating that ‘it grows in
              umbraculifera from botanical gardens throughout the world,                             N-East of Madagascar in an island called Ste Marie, Illes
              travelled to Mauritius to collect specimens of the extant spe-                         Aux Nattes’ (Dave’s Garden, ). This information as
              cies of Dracaena, and investigated phylogenetic relationships                          well as the results from preliminary phylogenetic analyses
              using this material, as well as GenBank accessions from spe-                           prompted us to visit Ile Sainte-Marie and its small outlier
              cies from other islands of the Western Indian Ocean. As our                            Ile aux Nattes, off the east coast of Madagascar, in
              initial phylogenetic reconstruction based on DNA sequence                              October , where three samples of two native Dracaena
              data indicated that living plants identified as D. umbraculifera                       species were collected (Table ).
              were more closely related to species in Madagascar than to                                 DNA was extracted from the leaf tissue samples using a
              those in Mauritius, we conducted fieldwork in Madagascar                               modified Cetyl trimethylammonium bromide (CTAB) ap-
              in an attempt to collect additional possible relatives and per-                        proach (Doyle & Doyle, ). As a recent molecular phylo-
              haps also locate the presumed-extinct D. umbraculifera.                                genetic study that investigated relationships in Malagasy D.
                                                                                                     reflexa (Buerki et al., ) employed a plastid marker span-
              Methods                                                                                ning the trnL gene and trnL-F spacer, we selected this mark-
                                                                                                     er for our study to make use of previously generated DNA
              Sample collection and molecular methods                                                sequence data. We conducted polymerase chain reactions
                                                                                                     (PCR) using the primers C and F (Taberlet et al., )
              We obtained leaf samples preserved in silica gel from living                           and previously published amplification protocols (Shaw
              collections of  accessions identified as D. umbraculifera                            et al., ). PCR products were cleaned with ExoSAP

              Oryx, 2018, 52(3), 427–436 © 2018 Fauna & Flora International doi:10.1017/S0030605317001570
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430         C. E. Edwards et al.

                TABLE 1 Cultivated accessions of Dracaena umbraculifera and Dracaena reflexa used in phylogenetic analysis of Dracaena species.

                                                                                                       Type of          ID confirmed by                                accession
                Label                     Location                    Accession number                 collection       inflorescence?          Source                 number
                D. umbraculifera          Vienna University           WU0077694 (1895)                 Herbarium        Yes                     Plant grown in         MG020508
                                          Herbarium, Vienna                                                                                     botanical gar-
                                          Austria                                                                                               den in Vienna
                D. umbraculifera          Personal garden of          Voucher deposited in             Living           Yes                     Unknown                MG020494
                                          I. Vencapah, Mont           the Herbarium of the
                                          Choisy, Mauritius           Missouri Botanical
                                                                      Garden: Vencapah
                ‘D. umbraculifera’ Wairere Nursery,                                                    Living           No                      Chiltern Seeds         MG020491
                                   Auckland, New
                D. umbraculifera Dunedin Botanic                                                       Living           No                      Chiltern Seeds         MG020492
                                   Garden, Dunedin,
                                   New Zealand
                ‘D. umbraculifera’ Toronto Zoo,                                                        Living           No                      Unknown                MG020497
                                   Toronto, Canada
                ‘D. umbraculifera’ Botanic Garden of                  6360PA                           Living           No                      Unknown                MG020493
                                   Smith College
                                   Northampton, USA
                ‘D. umbraculifera’ Conservatoire                      80-0330                          Living           No                      Jardin                 MG020505
                                   Botanique National                                                                                           Botanique
                                   de Brest, France                                                                                             Genève
                ‘D. umbraculifera’ Moscow Main                        New & old greenhouses            Living           No                      Grown from             MG020496
                                   Botanic Garden,                                                                                              seed (1968)
                                   Moscow, Russia
                ‘D. umbraculifera’ Komarov Botanical                                                   Living           No                      Pre 1917               MG020504
                                   St. Petersburg,
                ‘D. umbraculifera’ Missouri Botanical                 1980-1301                        Living           No                      Unknown                MG020495
                                   Garden, St. Louis,                                                                                           (1904)
                ‘D. umbraculifera’ Jardin Botanique                   1989.3.056, 1990.3.194           Living           No                      Jardin                 MG020506
                                   Nancy, France                                                                                                Botanique
                ‘D. umbraculifera’ Muséum national                    7460, 58406, 71595               Living           No                      Unknown                MG020507
                                   d’Histoire naturelle,
                                   Paris, France
                D. reflexa         Missouri Botanical                 1989-4416                        Living                                   Joseph Hill Co         MG020498
                                   Garden, St. Louis,                                                                                           Tropical
                                   USA                                                                                                          Foliage, Miami

                (USB Corporation, Cleveland, USA) and sequenced in both                                ‘D. umbraculifera’ from a cultivated specimen at the Waimea
                directions using BigDye Chemistry (Applied Biosystems                                  Arboretum and Botanical Garden, Haleiwa, USA (JQ,
                (ABI), Foster City, USA) on an ABI xl DNA Genetic                                  Lu & Morden, ); three sequences of Dracaena from Asia
                Analyzer at the DNA analysis facility at Science Hill at                               and the Canary Islands, D. draco (KC), D. cambodiana
                Yale University, New Haven, USA. Forward and reverse se-                               (KC), and D. cochinchinensis (KC); multiple
                quences were assembled and edited in Geneious R (Kearse                               Asparagaceae s.l. outgroups, including Convallaria majalis
                et al., ).                                                                         (EU), Maianthemum gongshanensis (EU),
                   The new sequences generated in this study were aligned                              Disporopsis aspersa (EU), Polygonatum cyrtonema
                with the following  sequences from GenBank:  Dracaena                              (EU), and Cordyline cannifolia (KC); and one
                from Madagascar (EU-EU, Buerki et al., );                              additional outgroup from another family of Asparagales,

                                                                                           Oryx, 2018, 52(3), 427–436 © 2018 Fauna & Flora International doi:10.1017/S0030605317001570
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Rediscovery of Dracaena umbraculifera                     431

              TABLE 2 Wild accessions of Dracaena species used in phylogenetic analysis. All voucher specimens are deposited in the Herbarium of the
              Missouri Botanical Garden.

                                                                                                                                                    GenBank accession
              Species                            Location                                                                    Voucher                number
              D. floribunda                      On the west banks of the Papaya River, Henrietta, Mauritius                 Edwards 299            MG020499
              D. reflexa var. reflexa            Brise Fer Conservation Management Area, Mauritius                           Edwards 296            MG020500
              D. reflexa var. reflexa            Mondrain Reserve, Mauritius                                                 Edwards 300            MG020501
              D. concinna                        St. Martin cemetery, Baie du Cap, Mauritius                                 Edwards 301            MG020503
              D. reflexa var. angustifolia       Black River Gorges National Park, Mauritius                                 Edwards 297            MG020502
              D. umbraculifera                   Kalalao Forest, Ile Sainte-Marie, Madagascar                                Miller 10775           MG020509
              D. umbraculifera                   Kalalao Forest, Ile Sainte-Marie, Madagascar                                Miller 10776           MG020511
              D. xiphophylla                     Kalalao Forest, Ile Sainte-Marie, Madagascar                                Miller 10778           MG020510

              Crinum oliganthum (AY; Amaryllidaceae), which was                                from the wild in Mauritius and Madagascar (Table ). The
              used to root the trees. Alignments were conducted using the                            aligned length of the trnL-F data matrix was  characters,
              default settings in Muscle (Edgar, ) and were adjusted                             of which  characters were constant,  were variable but
              manually in Geneious.                                                                  parsimony-uninformative and  were parsimony-informative.
                                                                                                     Parsimony searches recovered , most-parsimonious
                                                                                                     trees with a length of  steps. Because the topologies of
              Data analysis                                                                          the trees obtained from Bayesian and parsimony phylogeny
                                                                                                     reconstruction were almost identical, we present only the
              Phylogenetic analyses were carried out using parsimony and
                                                                                                     Bayesian tree, with Bayesian posterior probabilities (PP)
              Bayesian approaches. Parsimony analysis was implemented
                                                                                                     and parsimony bootstrap support (BS) indicated on branches
              in PAUP* .a (Swofford, ) using heuristic searches,
                                                                                                     (Fig. ).
              tree bisection–reconnection branch swapping and ,
                                                                                                         Using Crinum as the outgroup, the remaining samples
              random addition replicates, saving  trees per replicate.
                                                                                                     were clustered into two well-supported clades (both with
              Bootstrap analyses (Felsenstein, ) with , replicates
                                                                                                     PP = ., BS = %), one comprising two cultivated sam-
              were employed to assess branch support, using a heuristic
                                                                                                     ples of ‘D. umbraculifera’ from New Zealand plus a sample
              search with tree bisection–reconnection branch swapping,
                                                                                                     of Cordyline, and the other containing all of the remaining
              with one random addition per replicate and saving no
                                                                                                     taxa. Within the latter clade the accession of ‘D. umbraculi-
              more than one tree per replicate. Bayesian phylogenetic ana-
                                                                                                     fera’ from the Botanic Garden of Smith College,
              lysis was conducted using MrBayes . (Ronquist et al.,
                                                                                                     Northampton, USA, and the samples of M. gongshanensis,
              ). The optimal model of evolution for the data was se-
                                                                                                     C. majalis and D. aspersa + P. cyrtonema were weakly sup-
              lected using the Akaike Information Criterion in jmodeltest
                                                                                                     ported, successive sisters to a well-supported clade (PP = .,
              (Darriba et al., ). We ran two analyses, using four chains
                                                                                                     BS = %) containing all remaining Dracaena accessions
              each, three hot and one cold, the temperature set to the de-
                                                                                                     (Fig. ). This main Dracaena clade formed an unresolved
              fault of ., flat priors, and the GTR + G model of evolution
                                                                                                     polytomy comprising seven lineages: () a single GenBank
              as selected by jmodeltest. Analyses were run for  million
                                                                                                     accession of D. reflexa var. linearifolia, () a GenBank acces-
              generations, sampling a tree every , generations. To de-
                                                                                                     sion of ‘D. umbraculifera’ from the Waimea Arboretum and
              termine the burn-in value, we used Tracer v. . (Rambaut
                                                                                                     Botanical Garden, () a clade with PP = . and BS = %
              et al., ) to examine the stabilization of the run para-
                                                                                                     containing three GenBank accessions of Dracaena from
              meters and discarded trees saved before the stabilization
                                                                                                     Asia and the Canary Islands, () a clade with PP = .
              of the scores. Posterior probabilities were calculated using
                                                                                                     and BS = % that included one GenBank accession of
              the sumt command in MrBayes. Trees were visualized by
                                                                                                     Dracaena xiphophylla and two of D. reflexa var. angustifolia
              constructing a majority-rule consensus of trees in the pos-
                                                                                                     from northern Madagascar (i.e. clade C of Buerki et al.,
              terior distribution using PAUP*.
                                                                                                     ), () a large clade with PP = . and BS = % con-
                                                                                                     taining  samples of D. reflexa from the far northern
              Results                                                                                Madagascar (i.e. clade A of Buerki et al., ), () a clade
                                                                                                     with PP = . and BS = % containing all six Dracaena ac-
              The final data set contained  sequences:  GenBank ac-                              cessions from Mauritius, and () a clade with PP = . and
              cessions and  sequences newly generated for this study,                              BS , % containing one single sample of D. xiphophylla
               of which were obtained from cultivated individuals                                  from Ile Sainte-Marie placed as the sister group to a clade
              (Table ) and eight of which were from plants collected                                with PP = . and BS , % containing an unresolved

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432         C. E. Edwards et al.

                FIG. 1 Bayesian phylogeny of wild and cultivated Indian Ocean Dracaena spp., with Bayesian posterior probabilities/parsimony
                support values indicated on the branches. Plants from Madagascar are in black font; plants from Mauritius are in turquoise; cultivated
                plants are in green, with the name of the garden; Dracaena from elsewhere (outgroups) are in yellow; and outgroups are in grey. D.
                umbraculifera individuals whose identification has not been confirmed by reproductive material are indicated by quotation marks.

                FIG. 2 Locations of D. umbraculifera populations in Madagascar from which samples were collected for phylogenetic analysis.

                                                                                           Oryx, 2018, 52(3), 427–436 © 2018 Fauna & Flora International doi:10.1017/S0030605317001570
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Rediscovery of Dracaena umbraculifera                     433

              polytomy of the two positively identified samples of D. um-                            umbraculifera and the overall phylogenetic placement of
              braculifera (from Mauritius and Vienna, respectively), two                             the species. The most likely reason that this species has re-
              samples from Ile Sainte-Marie, seven ‘D. umbraculifera’ ac-                            mained a mystery to botanists for centuries and has long
              cessions from botanical gardens (from Missouri, Moscow,                                been considered to be extinct is that it was attributed incor-
              Toronto, St. Petersburg, Paris, Brest and Nancy) and eight                             rectly to Mauritius. Records accompanying th century
              samples of D. reflexa from coastal north-eastern and north-                            material from the western Indian Ocean were often scanty
              central Madagascar (i.e. clade B of Buerki et al., ).                              at best, and it is likely that the original plant on which
                                                                                                     Jacquin based his description was obtained in a shipment
                                                                                                     of plants from the Pamplemousses Garden in Mauritius,
              Discussion                                                                             leading to its misattribution to that island. That the species
                                                                                                     was never detected in Madagascar is not particularly sur-
              The origin and closest relatives of Dracaena                                           prising given the country’s extensive botanical diversity
              umbraculifera                                                                          and endemism, the high vegetative similarity and taxonomic
                                                                                                     uncertainty of Malagasy Dracaena, and the lack of compre-
              The phylogenetic analyses presented here indicate that all                             hensive, expert knowledge of the Dracaena of the region.
              species of Dracaena currently occurring in Mauritius form                              Although it is possible that D. umbraculifera once occurred
              a well-supported clade, whereas the two samples positively                             in the wild in Mauritius and went extinct, the phylogenetic
              identified as D. umbraculifera (i.e. the herbarium sample                              analysis indicates that D. umbraculifera probably originated
              from Vienna and the living plant in the private garden,                                in Madagascar, which would require a relatively recent col-
              with an umbel-like inflorescence) are more closely related                             onization event by D. umbraculifera from Madagascar to
              to a clade comprising multiple samples of D. reflexa from                              Mauritius, followed by its extinction in Mauritius, which
              Madagascar (i.e. clade B of Buerki et al., ), suggesting                           is a less parsimonious explanation.
              that D. umbraculifera may not be a Mauritian species.
              Previous phylogenetic analysis of D. reflexa in Madagascar
              recovered three clades that were generally distributed ac-                             Current status of Dracaena umbraculifera
              cording to geography, two that included samples from far
              northern Madagascar (i.e. clades A and C of Buerki et al.,                             Surveys conducted during two field trips in  and 
              ) and one (i.e. clade B of Buerki et al., ) containing                         located a total of five wild populations of D. umbraculifera
              accessions from coastal north-eastern and north-central                                (Fig. ), all of which occur in low-elevation evergreen forest
              Madagascar, along with a few accessions from the southern                              on laterite and sandy soils. Three closely spaced populations
              portion of the country. Our analysis also showed that D. um-                           occur in partially degraded forest at Pointe à Larrée on
              braculifera formed a clade with individuals of D. reflexa be-                          mainland Madagascar (Fig. ), one inside the recently estab-
              longing to clade B (Buerki et al., ), which provided                               lished (in April ) protected area being managed jointly
              some indication of its likely geographical origin (i.e. coastal                        by the local community and Missouri Botanical Garden,
              north-eastern and north-central Madagascar). The inter-                                and two that are unprotected. A fourth population occurs
              pretation that D. umbraculifera may be of Malagasy origin                              in Ile aux Nattes (Fig. ), on private land in highly disturbed
              was consistent with the information provided by the owner                              secondary vegetation. The fifth population is located in
              of the positively identified plant in a private garden in                              largely intact, closed-canopy evergreen forest at Kalalao on
              Mauritius, which prior to this study was the only known liv-                           Ile Sainte-Marie (Fig. ). A few additional, apparently
              ing individual unambiguously attributable to the species.                              planted individuals occur on Sainte-Marie in private
              Fieldwork in Madagascar in  and  led to the discov-                            gardens.
              ery of several wild populations in Ile Sainte-Marie and Ile                                Although our findings demonstrate that D. umbraculi-
              aux Nattes, and further searches at Pointe à Larrée on the                             fera is clearly not extinct, it is nevertheless rare and faces
              mainland, directly across from Ile Sainte-Marie, found add-                            many threats. Despite being known from five populations
              itional wild populations (Fig. ).                                                     on Ile Sainte-Marie and mainland Madagascar, we estimate
                  Although D. umbraculifera has always been considered                               that no more than  mature individuals of D. umbraculifera
              to be a Mauritian species, the geographical distribution of                            remain in the wild, all of which face threats from habitat
              the wild populations indicate that it is native to                                     degradation, land clearing for agriculture and development,
              Madagascar. Phylogenies also suggest that it is more closely                           fires, and cyclones. The total number of individuals is below
              related to Malagasy species than Mauritian species, indicat-                           the threshold for Critically Endangered status under IUCN
              ing that D. umbraculifera most likely originated in                                    Red List Criterion D (IUCN, ). The species has an
              Madagascar. Because we included the herbarium sample                                   Extent of Occurrence of  km and an Area of
              from Vienna, which is probably derived from the type spe-                              Occupancy of  km, and is facing continued decline in
              cimen, we can be certain about the identification of D.                                the quality of its habitat and the number of mature

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434         C. E. Edwards et al.

                individuals. As with many threatened species in Madagascar,                            from New Zealand, which were placed among other
                efforts to conserve D. umbraculifera should focus on protect-                          Asparagaceae outgroups outside Dracaena in the phylogen-
                ing and restoring the forest fragments that harbour the wild                           etic tree. Our phylogenetic analyses did not, however, pro-
                populations. Establishing back-up collections of the species in                        vide adequate resolution to confirm the identification of the
                ex situ facilities should also be carried out to contribute to its                     remaining botanical garden accessions; their conservation
                long-term conservation.                                                                importance thus remains unresolved. Despite the fact that
                                                                                                       several botanical garden samples (from Missouri Botanical
                                                                                                       Garden, France, Russia and Toronto) were placed in the
                Taxonomic implications                                                                 clade that contained individuals confirmed to be D. umbra-
                                                                                                       culifera, this group also included accessions that belong to
                Our results indicate that D. reflexa, as currently circum-
                                                                                                       the D. reflexa clade B (Buerki et al., ), and we were un-
                scribed, is not monophyletic. Material from Mauritius as-
                                                                                                       able to determine to which group the botanical garden sam-
                signed to this species forms a clade with the two other
                                                                                                       ples belong. In the absence of flowering material, future
                Mauritian natives D. floribunda and D. concinna, indicating
                                                                                                       research using additional sampling and more informative
                that ‘D. reflexa’ in Mauritius is evolutionarily distinct from
                                                                                                       molecular markers (i.e. collected using next-generation
                populations in Madagascar and therefore should be referred
                                                                                                       DNA sequencing approaches) will be necessary to confirm
                to under a different name. Our results also show that D. re-
                                                                                                       the identity of these botanical garden samples as well as to
                flexa clade B of Buerki et al. () is more closely related to
                                                                                                       assess their genetic diversity and their value for conservation
                D. umbraculifera, which occurs in the same geographical
                                                                                                       or reintroduction.
                area, than to other populations from northern Madagascar
                                                                                                           This study highlights the value and importance of the liv-
                also assigned to D. reflexa, indicating that D. reflexa in
                                                                                                       ing collections maintained in botanical gardens, even those
                Madagascar is also not monophyletic. As currently circum-
                                                                                                       that are over a century old and lack information about their
                scribed, D. reflexa occurs throughout the islands of the
                                                                                                       origin. Genetic analysis of living collections can play an im-
                Western Indian Ocean region, including Madagascar,
                                                                                                       portant role in gaining a better understanding of poorly
                Mauritius, Rodrigues, Réunion and the Seychelles archipel-
                                                                                                       known species and making new discoveries of interest for
                ago, and also in Mozambique in continental Africa (Wright,
                                                                                                       biodiversity and conservation. In the past, plants of un-
                ; eMonocot, ). Given the geographical structuring
                                                                                                       known origin have often been regarded as being of little
                of lineages observed in Mauritius and Madagascar, it is pos-
                                                                                                       or no value for conservation purposes. However, this re-
                sible that populations currently assigned to ‘D. reflexa’ oc-
                                                                                                       search would never have been undertaken and D. umbracu-
                curring in these geographically isolated regions represent
                                                                                                       lifera would probably not have been rediscovered in
                distinct lineages and thus belong to more than one species.
                                                                                                       Madagascar if we had not used genetic analysis to elucidate
                It is also possible that some of these lineages occurring in
                                                                                                       the true identity of the living collections of ‘D. umbraculi-
                islands in the western Indian Ocean could be close relatives
                                                                                                       fera.’ Genetic analysis of living collections will unquestion-
                of D. umbraculifera. However, this study included only a
                                                                                                       ably bring new value to undocumented living collections in
                small portion of the diversity present in Madagascar and
                                                                                                       botanical gardens and facilitate their use for conservation
                Mauritius, did not include Dracaena from other locations
                                                                                                       purposes, such as for reintroductions and augmentations
                in the Indian Ocean region, and lacked the phylogenetic
                                                                                                       of depleted gene pools of wild populations of some
                resolution needed to elucidate phylogenetic relationships
                                                                                                       Critically Endangered species.
                fully. A future study employing more informative molecular
                                                                                                           Our findings also highlight the need for additional work
                markers (i.e. those generated using next-generation DNA
                                                                                                       in Madagascar and other islands of the western Indian
                sequencing approaches, such as RAD-seq or whole chloro-
                                                                                                       Ocean. Madagascar contains an estimated , vascular
                plast genomes) and more comprehensive taxon sampling of
                                                                                                       plant species, of which nearly % are thought to be endem-
                Dracaena in Madagascar, Eastern Africa and the islands of
                                                                                                       ic (Callmander et al., ; Madagascar Catalogue, ), and
                the Western Indian Ocean is needed to clarify species
                                                                                                       many are threatened as a result of extensive and ongoing de-
                boundaries, evolutionary relationships and patterns of di-
                                                                                                       forestation. Although Madagascar has been the focus of
                versity, and identify species in need of conservation.
                                                                                                       plant taxonomic work for over  centuries, comprehensive,
                                                                                                       expert knowledge of many taxa in the region is lacking, and
                Status of the botanical garden collections                                             many endemic species are poorly known. As previously sta-
                                                                                                       ted, D. umbraculifera was overlooked by botanists in
                The phylogenetic analyses presented here have helped to re-                            Madagascar because of the extensive botanical diversity
                solve the identification of some of the sampled individuals                            and endemism there, the high vegetative similarity and
                identified as ‘D. umbraculifera’ in botanical gardens. Several                         taxonomic uncertainty of Malagasy Dracaena, and the
                are clearly misidentified, including those growing in the                              lack of comprehensive, expert knowledge of the Dracaena
                Botanical Garden at Smith College and the accessions                                   of the region. An accurate understanding of the status of a

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Rediscovery of Dracaena umbraculifera                         435

              species is necessary to devise effective conservation strat-                           BGCI (B O TA N I C G A R D E N S C O N S E R VAT I O N I N T E R N A T I O N A L ) ()
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                S WO F F O R D , D.L. () PAUP*. Phylogenetic Analysis Using                                       C A M A R A , A D O L P H E L E H A V A N A , P O R T E R P. L O W R Y II and
                    Parsimony (*and Other Methods). . beta . Sinauer Associates,                                 J A M E S M I L L E R are interested in taxonomy and conservation of the
                    Sunderland, USA.                                                                                  flora of Madagascar and Africa. A N D R E W W Y A T T and P E T E R
                T A B E R L E T , P., G I E L LY , L., P A U T O U , G. & B O U V E T , J. () Universal           W Y S E J A C K S O N are broadly interested in conservation activities in
                    primers for amplification of three non-coding regions of chloroplast                              botanical gardens, and using botanical garden living collections for
                    DNA. Plant Molecular Biology, , –.                                                      ex situ conservation of rare plant species.

                                                                                                           Oryx, 2018, 52(3), 427–436 © 2018 Fauna & Flora International doi:10.1017/S0030605317001570
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