Translator Disclaimer
1 April 2016 Diets of Syntopic Black-knobbed Sawbacks (Graptemys nigrinoda) and Alabama Map Turtles (Graptemys pulchra) in the Alabama River
Peter V. Lindeman
Author Affiliations +
Abstract

The emydid turtle genus Graptemys is characterized by intra- and interspecific dietary diversity. Sympatric species pairs typically differ in trophic morphology and dependence on bivalve mollusks in female diets, yet there is a lack of comprehensive comparisons of the diets of sympatric species. I collected feces from 92 black-knobbed sawbacks (G. nigrinoda) and 54 Alabama map turtles (G. pulchra) from the Alabama River at a site in Autauga and Lowndes counties, Alabama. Samples were analyzed separately for unsexed juveniles, adult males, juvenile females larger than the smallest mature males, and adult females of each species. Sponges, aquatic insects (particularly caddisfly larvae), and filamentous algae were the primary foods of G. nigrinoda. Native mussels, invasive Asian clams, and aquatic insects (but few caddisfly larvae) were the primary foods of G. pulchra. Each of the four sex and size classes exhibited substantially greater similarity with conspecific classes than with classes of the other species. Intraspecific interclass similarity in diet showed size-structured patterns in both species but with opposite patterns. In G. nigrinoda the classes that were most similar in diet were the smallest-bodied classes, unsexed juveniles and adult males, which fed most heavily on sponges; the largest-bodied class, adult females, fed most heavily on filamentous algae and was least similar in diet to other classes. In G. pulchra the classes that were most similar in diet were the two largest-bodied classes, adult and juvenile females, which fed most heavily on bivalve mollusks; the smallest-bodied class, unsexed juveniles, was least similar in diet to other classes. These results reinforce the importance of body size in determining Graptemys diets and suggest dietary differentiation of sympatric Graptemys species may extend beyond differentiation in adult females more often than is generally thought.

© 2016 American Midland Naturalist
Peter V. Lindeman "Diets of Syntopic Black-knobbed Sawbacks (Graptemys nigrinoda) and Alabama Map Turtles (Graptemys pulchra) in the Alabama River," The American Midland Naturalist 175(2), 194-205, (1 April 2016). https://doi.org/10.1674/0003-0031-175.2.194
Received: 1 May 2015; Accepted: 1 December 2015; Published: 1 April 2016
JOURNAL ARTICLE
12 PAGES


Share
SHARE
ARTICLE IMPACT
RIGHTS & PERMISSIONS
Get copyright permission
Back to Top