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