Ant suppression has little effect on termite activity and plant decomposition - Sarah Bonney Alan Andersen and Ben Hoffmann - SANParks
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Ant suppression has little effect on termite activity and plant decomposition Sarah Bonney Alan Andersen and Ben Hoffmann
Ecological Importance • 15,000 species described worldwide with thousands more undescribed • Occupy every terrestrial habitat except the poles • >20% terrestrial faunal biomass • Play many varied roles in the ecosystem
The little rulers
• Soil modification and nutrient cycling
• Regulation of other arthropods
Competition
Territoriality
Predation
• Mutualisms
Ant-tending
Plant defense
Seed dispersal
• Seed predation
Presence of ants and perceived
predation risk alter termite
behavior and distribution
Negative correlations of ants with termites
• Arboreal – Goncalves et al 2005 - Brazil
• Arboreal – Leponce et al 1999 – New Guinea
• Transects – Dambros et al 2016 – Amazon rainforest
Presence of ants increases time taken for termites to occupy
baits
• DeSouza et al 2009 - Brazil
Termites abandoned food resources quicker with
increased predation risk
• Korb and Lisenmair 2002 – Ivory Coast
Ant suppression increased bait consumption by termites
• Parr et al 2015 – South Africa
The little things that run the world: Ecological responses
to the removal of a dominant faunal group in an
PhD Australian tropical savanna
project: 1.How will termites respond to the removal of their most
Chapter 4 important predator?
2. How does ant suppression affect the rate of decomposition
of leaf litter, wood and grass?
Study design
Two sites with contrasting ant communities:
TWP: High abundance and diversity TERC: Low abundance and diversity
Primarily dominant species Few dominant species
Annual fire frequency Low fire frequency
Control
BACI design
3 x paired
Treatment area 50 x 50 m plots/site
30 m
Inner sampling area 30 x 30 m Treatment plot Control plot
Ant suppression and
sampling
• Baited using catfood mixed with honey and
confidor (imacalroprid).
• YR1 - Every 3 months
• YR2 - Every month
• Sampled ants using pitfall traps and catfood
lures
• Every 6 months
• Additional lure sample 2 months after
baiting ceased
Termite community and
activity
Number of Encounters
• Transect searches
• 100 minutes of active
searching/plot
• Cellulose lures
• Paper towel lures buried just under
the surface – checked ~ every 11
days
Mound growth
• Basal circumference + height = volume
Termite community and activity Attack rate and consumption Toilet paper and wood sticks buried just under the surface. Amount consumed scored 0 = 0% consumed, 1 = 1-25%, 2 = 26- 50%, …….. 5 = 100% Decomposition Wood, grass and leaf litter • Left on soil surface for 6 months
Sampling schedule
Pre-treatment YR1 YR2 YR3
Ants Oct 2015
Jan 2016 Monthly from Sep 2016 to Feb 2018
Baiting
Apr 2016 (excluding Dec 2016)
Jul 2016
Nov 2015
Nov 2014 Mar 2017
Pitfalls Apr 2016
Sep 2015 Oct 2017
Sep 2016
Oct 2015
Apr 2015 Mar 2017 Mar 2018 (TWP
Lures Feb 2016
Aug 2015 Oct 2017 only)
Sep 2016
Termites Lures May 2015 May 2016 May 2017
Transects Dec 2015 Jan 2017 Feb 2018
Consumption Mar to May 2015 Mar to May 2016 Mar to May 2017
Mounds Aug 2015 Apr 2016 Apr 2017
Decomposition Jan to June 2016 Jan to June 2017Results - Interpretation Treatment plots presented as % of control plots
Positive
Percent of control
response No
response Negative
response
Treatment = control
Pre-treatment Post treatmentAnt suppression effectiveness
pitfalls
lures
TERC
TWP
80% suppression at TWP No suppression at TERC
* pTermite encounters and species richness
TWP Transects TWP Lures
300
450
250 400
350
200
300
150 250
200
100 150
100
50
50
0 0
Pre YR1 YR2 Pre YR1 YR2 Pre YR1 YR2 Pre YR1 YR2
-50
Encounters Species richness Encounters Species richness
No significant change in encounters or species richnessTermite encounters and species richness
TERC Transects TERC Lures
300
500
450 250
400
200
350
300
150
250
200
100
150
100 50
50
0 0
Pre YR1 YR2 Pre YR1 YR2 Pre YR1 YR2 Pre YR1 YR2
Encounters Species richness Encounters Species richness
No significant change in encounters or species richnessTermite encounters – feeding guilds
TWP Transects TWP Lures
500
500
400 400
300 300
200 * 200
100 100
0 0
-100 pre YR1 YR2 pre YR1 YR2 -100 pre YR1 YR2 pre YR1 YR2
Wood Debris Wood Debris
TERC Transects TERC Lures
400 1000
350
300 800
250
600
200
150 400
100
50 200
0
0
pre YR1 YR2 pre YR1 YR2 pre YR1 YR2 pre YR1 YR2
-200
Wood Debris Wood Debris *pMound growth
YR1 YR2
Control Treatment Control Treatment
TWP
No. measured 18 20 14 15
No. damaged/lost 4 3 5 7
No. with no growth 6 6 3 1
No. growing 8 11 6 7
Mean growth (cm2) 1,618.14 8,484.4 333.83 58,224.38 NS
(± SD) (± 768.14) (± 12,676.91) (± 264.21) (± 96,478.63)
TERC
No. measured 35 33 29 33
No. Damaged/lost 17 18 13 18
No. with no growth 0 0 0 0
No. growing 18 15 16 15
Mean growth (cm2) 829.57 651.78 2,464.97 2,133.3 NS
(± SD) (± 297.36) (± 303.49) (± 2,306.77) (± 130.21)Attack rate of lures
TWP Paper 300
TWP Wood
200
250
**
150 200
100 150
50 100
0 50
Pre YR1 YR2 0
Pre YR1 YR2
no. attacked
no. attacked
TERC Paper TERC Wood
140 300
120
100 200
80
60
100
40
20
0 0
Pre YR1 YR2 Pre YR1 YR2
-100
no. attacked no. attacked
**pConsumption 250
TWP Paper TWP Wood
200
150 150
100 100
50 50
0 0
Pre YR1 YR2 Pre YR1 YR2
intensity intensity
TERC Paper TERC Wood
200 400
150 300
100 200
100
50
0
0
Pre YR1 YR2
Pre YR1 YR2 -100
intensity
intensityDecomposition bags
400 TWP
300
200
100
*
0
YR1 YR2 YR1 YR2 YR1 YR2
-100
Wood Litter Grass
TERC
350
300
*
250
200
150
100
50
0
YR1 YR2 YR1 YR2 YR1 YR2
Wood Litter GrassResults summary
TWP TERC
Ant abundance Drop of 80% by YR2 No change
Termite abundance, species richness and No change No change
composition
Feeding groups Lower abundance of wood feeders in YR1 in No change
transects
Mounds Higher in treatment plots but variable - NS No difference
Attack rate of lures Higher attack rate of wood lures in YR1 No difference
Consumption of lures No difference No difference
Decomposition Lower decomposition of grass in treatment plots Higher decomposition of leaf litter in treatment
in YR1 plots in YR1
Conclusion: Ant suppression has caused small and inconsistent changes
Contrasting results to those of previous studiesPossible explanations 1. Ants are not so abundant in Australia 2. Termites are not such as important dietary component of Australian ants 3. Australian termites are more resilient
Thank you! Any Questions? References • Desouza et al (2009) Trophic controls delaying foraging by termites: reasons for the ground being brown? Bulletin of Entomological research, 99, 603-609 • Dambros et al (2016) Association of ant predators and edaphic conditions with termite diversity in an Amazonian Rainforest. Biotropica 48(2), 237-245 • Leponce et al (1999) Community interactions between ants and arboreal-nesting termites in New Guinea coconut plantations. Insectes soc 46, 126-130 • Gonvalves et al (2005) Predation and interference competition between ants and arboreal termites. Sociobiology 46(2) • Parr et al (2005) Suppression of savanna ants alters invertebrate composition and influences key ecosystem processes. Ecology 97(6) 1611-1617
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