1
D. scutellatus C. tricolor -18 -16 -14 -12 -10 -8 Species δ 13 C (‰) Unpaired t-test: p < 0.0001 D. scutellatus C. tricolor 3 4 5 6 7 Species δ 15 N (‰) Unpaired t-test: p = 0.0096 D. scutellatus C. tricolor 8 10 12 14 16 18 20 Species δ 34 S (‰) Unpaired t-test: p = 0.0001 Isotopic niche modeling Stable isotope ratios reveal trophic niche partitioning among hermit crabs from tropical polyspecific seagrass meadows Loïc N. MICHEL 1,* , Bruno FRÉDÉRICH 2 , Thierry LAVITRA 3 & Gilles LEPOINT 1 1 Laboratory of Oceanology, MARE Centre, University of Liege, Belgium. 2 Functional and Evolutionary Morphology Laboratory, University of Liege, Belgium. 3 Institute of Fishery and Marine Sciences (IHSM), University of Toliara, Madagascar. *E-mail: [email protected], publications available at http://goo.gl/xdxaHM Conclusions & perspectives Acknowledgements D. scutellatus C. tricolor Model-estimated standard ellipse area, SEA b (‰ 2 ) 5 4 3 2 1 0 D. scutellatus C. tricolor Species 4 4.5 5 5.5 6 δ 15 N (‰) δ 13 C (‰) -16 -9 -15 -14 -13 -12 -11 -10 Dardanus scutellatus Ciliopagurus tricolor LM is a BELSPO postdoctoral fellow. BF is a F.R.S.-FNRS postdoctoral researcher. GL is a F.R.S-FNRS research associate. LM and BF were supported by a F.R.S-FNRS travel grant. Authors would like to thank the staff of IHSM Toliara and Prof. I. Eeckhaut (UMons) for logistical support during sampling. Differences in foraging ecology of these two hermit crabs could limit interspecific competition and facilitate coexistence of D. scutellatus and C. tricolor in Malagasy seagrass beds Analysis of food items sampled at the same time and location will enable use of a mixing model and ultimately reveal which producers actually support hermit crabs populations Download this poster Context, objectives & methods Toliara Results & discussion Tropical polyspecific seagrass meadows provide many ecological and socio- economical services These ecosystems undergo multiple anthropogenic threats (eutrophication, overfishing, invertebrate overharvesting) Data about functional ecology of meadows and structure of the associated food webs are needed to understand how they could react to human impacts As part of a larger study: examination of resource segregation between two common, co-occurring, supposedly omnivore Diogenidae hermit crabs Sampling of Dardanus scutellatus (n=28) and Ciliopagurus tricolor (n=17) on the Toliara Great Reef (SW Madagascar, see map on left) in July 2014 Analysis of stable isotope ratios of C, N and S of their abdominal muscle using CF-EA-IRMS Exploration of data using statistical hypothesis testing and isotopic niche modeling (SIBER: Stable Isotope Bayesian Ellipses in R) [Jackson et al. 2011, J Anim Ecol 80: 595-602] Isotopic ratios of consumers Significant differences in the isotopic composition of all 3 elements The two species do not feed on the same items According to literature from the area: [Lepoint et al. 2008, Sci Mar 72: 109-117; Frédérich et al. 2009, Ichtyol Res 56: 10-17 ] 1. Both species are primary consumers. 2. C. tricolor mostly relies on algal production, while some D. scutellatus could assimilate seagrass -derived matter. Pelagic inputs to hermit crab diet are likely weak. No overlap of standard ellipses (solid lines on the figure on the left) of the two species they are supported by different core resources The area of the standard ellipse of D. scutellatus is larger than the one of C. tricolor in 97.46% of 10 5 model estimates D. scutellatus exploits more food items than C. tricolor.

Stable isotope ratios reveal trophic niche partitioning ...€¦ · matter. Pelagic inputs to hermit crab diet are likely weak. No overlap of standard ellipses (solid lines on the

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Page 1: Stable isotope ratios reveal trophic niche partitioning ...€¦ · matter. Pelagic inputs to hermit crab diet are likely weak. No overlap of standard ellipses (solid lines on the

D. scutellatus C. tricolor-18

-16

-14

-12

-10

-8

Species

δ13 C

(‰)

Unpaired t-test: p < 0.0001

D. scutellatus C. tricolor3

4

5

6

7

Species

δ15 N

(‰)

Unpaired t-test: p = 0.0096

D. scutellatus C. tricolor8

10

12

14

16

18

20

Species

δ34 S

(‰)

Unpaired t-test: p = 0.0001

Isotopic niche modeling

Stable isotope ratios reveal trophic niche partitioning among hermit crabs from tropical polyspecific seagrass meadows

Loïc N. MICHEL1,*, Bruno FRÉDÉRICH2, Thierry LAVITRA3 & Gilles LEPOINT1 1Laboratory of Oceanology, MARE Centre, University of Liege, Belgium. 2Functional and Evolutionary Morphology Laboratory, University of Liege, Belgium. 3Institute of Fishery and Marine Sciences (IHSM), University of Toliara, Madagascar. *E-mail: [email protected], publications available at http://goo.gl/xdxaHM

Conclusions & perspectives Acknowledgements

01

23

45

Group

Area

(per

mil^

2)

D. scutellatus C. tricolor

Mod

el-e

stim

ated

sta

ndar

d el

lipse

are

a, S

EAb

(‰2 )

5 4

3 2

1 0

D. scutellatus C. tricolor

Species −16 −15 −14 −13 −12 −11 −10 −9

4.0

4.5

5.0

5.5

6.0

d13C

d15N

D. scutellatusC. tricolor

4 4.

5 5

5.5

6 δ1

5 N (‰

)

δ13C (‰) -16 -9 -15 -14 -13 -12 -11 -10

Dardanus scutellatus Ciliopagurus tricolor

LM is a BELSPO postdoctoral fellow. BF is a F.R.S.-FNRS postdoctoral researcher. GL is a F.R.S-FNRS research associate. LM and BF were supported by a F.R.S-FNRS travel grant. Authors would like to thank the staff of IHSM Toliara and Prof. I. Eeckhaut (UMons) for logistical support during sampling.

§  Differences in foraging ecology of these two hermit crabs è could limit interspecific competition and facilitate coexistence of D. scutellatus and C. tricolor in Malagasy seagrass beds

§  Analysis of food items sampled at the same time and location will enable use of a mixing model and ultimately reveal which producers actually support hermit crabs populations

Download this poster ➔

Context, objectives & methods

Toliara

Results & discussion

§  Tropical polyspecific seagrass meadows provide many ecological and socio-economical services

§  These ecosystems undergo multiple anthropogenic threats (eutrophication, overfishing, invertebrate overharvesting)

§  Data about functional ecology of meadows and structure of the associated food webs are needed to understand how they could react to human impacts

§  As part of a larger study: examination of resource segregation between two common, co-occurring, supposedly omnivore Diogenidae hermit crabs

⬇︎ §  Sampling of Dardanus scutellatus (n=28) and Ciliopagurus tricolor (n=17) on

the Toliara Great Reef (SW Madagascar, see map on left) in July 2014

§  Analysis of stable isotope ratios of C, N and S of their abdominal muscle using CF-EA-IRMS

§  Exploration of data using statistical hypothesis testing and isotopic niche modeling (SIBER: Stable Isotope Bayesian Ellipses in R) [Jackson et al. 2011, J Anim Ecol 80: 595-602]

Isotopic ratios of consumers

Significant differences in the isotopic composition of all 3 elements ➔ The two species do not feed on the same items

According to literature from the area: [Lepoint et al. 2008, Sci Mar 72: 109-117; Frédérich et al. 2009, Ichtyol Res 56: 10-17 ]

1 . Bo th spec ie s a re pr imary consumers.

2. C. tricolor mostly relies on algal production, while some D. scutellatus could assimilate seagrass-derived matter. Pelagic inputs to hermit crab diet are likely weak.

No overlap of standard ellipses (solid lines on the figure on the left) of the two species ➔ they are supported by different core resources

◀︎  

The area of the standard ellipse of D. scutellatus is larger than the one of C. tricolor in 97.46% of 105 model estimates ➔ D. scutellatus exploits more food items than C. tricolor.  

▶︎