Trophic analysis of two subtropical South American freshwater crabs using stable isotope ratios
- PDF / 631,330 Bytes
- 9 Pages / 547.087 x 737.008 pts Page_size
- 73 Downloads / 132 Views
PRIMARY RESEARCH PAPER
Trophic analysis of two subtropical South American freshwater crabs using stable isotope ratios Edward D. Burress • Michael M. Gangloff Lynn Siefferman
•
Received: 11 February 2012 / Revised: 4 August 2012 / Accepted: 19 August 2012 / Published online: 5 September 2012 Ó Springer Science+Business Media B.V. 2012
Abstract Crustaceans with crayfish- and crab-morphologies do not co-occur often. However, the crab families Aeglidae (crayfish morphology) and Trichodactylidae (crab morphology) are sympatric in many subtropical South American streams. We investigated the trophic status of Aegla uruguayana (Aeglidae) and Trichodactylus panoplus (Trichodactylidae) in a South American subtropical piedmont river (Cuareim River, Uruguay) using d13C and d15N ratios. We estimated the relative importance of prey items using a five-source mixing model. Stable isotope analysis revealed that the two crabs have different trophic niches. Three fractionation rates (-1, 0, and ?1 %) influenced the estimated assimilation (%) of prey items to consumers. However, the relative importance of prey items was unaffected. A. uruguayana showed an ontogenetic shift from herbivore–detritivore to omnivore. Shared morphology between crayfishes and aeglids likely facilitates similar trophic roles; however, A. uruguayana occupies a much lower trophic position than is typical for crayfishes. T. panoplus is a
Handling editor: M. Power E. D. Burress M. M. Gangloff L. Siefferman Biology Department, Appalachian State University, 572 Rivers Street, Boone, NC 28608, USA E. D. Burress (&) Department of Biological Sciences, Auburn University, 331 Funchess, Auburn, AL 36849, USA e-mail: [email protected]; [email protected]
strict herbivore–detritivore. In contrast to tropical crabs, they do not engage in carnivory or exploit terrestrial subsidies. In subtropical South American streams, aeglids may be the functional equivalent of crayfishes, whereas trichodactylids may fill a trophic role atypical for freshwater crabs. Keywords Mixing model Trophic niche Aegla Trichodactylus Crustacean
Introduction Invertebrate functional roles in stream ecosystems vary considerably across spatial and biogeographic gradients. In Northern Hemisphere streams, crayfish and caddisflies are often the major taxa driving detritivory (Wallace & Webster, 1996; Covich et al., 1999; Benke et al., 2001; Creed & Reed, 2004); however, shrimps or crabs are often the major detritivores in tropical streams (Covich & McDowell, 1996; Covich et al., 1999; Dobson et al., 2002; Zimmerman & Covich, 2003; Boulton et al., 2008; Cross et al., 2008; Lancaster et al., 2008). The trophic niches of many invertebrate taxa are well understood (reviewed in Wallace & Webster, 1996; Covich et al., 1999). However, invertebrate communities in many tropical and subtropical regions are poorly studied and information on basic ecology is lacking. Crayfish are largely restricted to temperate zones, with most diversity occurring in Nearctic and Australasian regions (Crandall & B
Data Loading...
