Ant suppression has little effect on termite activity and ...
Transcript of Ant suppression has little effect on termite activity and ...
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 arthropodsCompetitionTerritorialityPredation
• MutualismsAnt-tendingPlant defenseSeed 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
PhD project: Chapter 4
The little things that run the world: Ecological responses to the removal of a dominant faunal group in an Australian tropical savanna
1. How will termites respond to the removal of their most important predator?
2. How does ant suppression affect the rate of decompositionof leaf litter, wood and grass?
Study design
Control
30 m
Control plotTreatment plot
Two sites with contrasting ant communities:
TWP: High abundance and diversityPrimarily dominant speciesAnnual fire frequency
BACI design
Treatment area 50 x 50 m
Inner sampling area 30 x 30 m
TERC: Low abundance and diversityFew dominant speciesLow fire frequency
3 x paired plots/site
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 catfoodlures• 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
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
Termite community and activity
Sampling schedulePre-treatment YR1 YR2 YR3
Ants
Baiting
Oct 2015
Jan 2016
Apr 2016
Jul 2016
Monthly from Sep 2016 to Feb 2018
(excluding Dec 2016)
PitfallsNov 2014
Sep 2015
Nov 2015
Apr 2016
Sep 2016
Mar 2017
Oct 2017
LuresApr 2015
Aug 2015
Oct 2015
Feb 2016
Sep 2016
Mar 2017
Oct 2017
Mar 2018 (TWP
only)
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 2017
Results - Interpretation
Treatment = control
Positive response
Negative response
Treatment plots presented as % of control plots
No response
Pre-treatment Post treatment
Perc
ent
of
con
tro
l
Ant suppression effectiveness
* p<0.05, **p<0.01, ***P<0.001
pitfalls
TWP
lures
TERC
80% suppression at TWP No suppression at TERC
Termite encounters and species richness
-50
0
50
100
150
200
250
300
Pre YR1 YR2 Pre YR1 YR2
Encounters Species richness
TWP Transects
No significant change in encounters or species richness
0
50
100
150
200
250
300
350
400
450
Pre YR1 YR2 Pre YR1 YR2
Encounters Species richness
TWP Lures
0
50
100
150
200
250
300
Pre YR1 YR2 Pre YR1 YR2
Encounters Species richness
TERC Lures
0
50
100
150
200
250
300
350
400
450
500
Pre YR1 YR2 Pre YR1 YR2
Encounters Species richness
TERC Transects
Termite encounters and species richness
No significant change in encounters or species richness
Termite encounters – feeding guilds
-100
0
100
200
300
400
500
pre YR1 YR2 pre YR1 YR2
Wood Debris
TWP Lures
-100
0
100
200
300
400
500
pre YR1 YR2 pre YR1 YR2
Wood Debris
TWP Transects
-200
0
200
400
600
800
1000
pre YR1 YR2 pre YR1 YR2
Wood Debris
TERC Lures
050
100150200250300350400
pre YR1 YR2 pre YR1 YR2
Wood Debris
TERC Transects
*
*p<0.05
Mound growthYR1 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
(± 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
(± SD) (± 297.36) (± 303.49) (± 2,306.77) (± 130.21)
NS
NS
Attack rate of lures
0
50
100
150
200
Pre YR1 YR2
no. attacked
TWP Paper
0
50
100
150
200
250
300
Pre YR1 YR2
no. attacked
TWP Wood**
0
20
40
60
80
100
120
140
Pre YR1 YR2
no. attacked
TERC Paper
-100
0
100
200
300
Pre YR1 YR2
no. attacked
TERC Wood
**p<0.01
Consumption
0
50
100
150
Pre YR1 YR2
intensity
TWP Paper
0
50
100
150
200
250
Pre YR1 YR2
intensity
TWP Wood
0
50
100
150
200
Pre YR1 YR2
intensity
TERC Paper
-100
0
100
200
300
400
Pre YR1 YR2
intensity
TERC Wood
Decomposition bags
-100
0
100
200
300
400
YR1 YR2 YR1 YR2 YR1 YR2
Wood Litter Grass
TWP
0
50
100
150
200
250
300
350
YR1 YR2 YR1 YR2 YR1 YR2
Wood Litter Grass
TERC
*
*
TWP TERC
Ant abundance Drop of 80% by YR2 No change
Termite abundance, species richness and composition
No change No change
Feeding groups Lower abundance of wood feeders in YR1 in transects
No change
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 in YR1
Higher decomposition of leaf litter in treatment plots in YR1
Results summary
Conclusion: Ant suppression has caused small and inconsistent changesContrasting results to those of previous studies
Possible 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