Diet and Feeding-Related Morphometrics of the Blackstripe Topminnow, \u3ci\u3eFundulus notatus\u3c/i\u3e, in Allotropic and Syntopic Populations with the Blackspotted Topminnow, \u3ci\u3eFundulus olivaceus\u3c/i\u3e

Abstract

The Fundulus notatus species complex consists of three described species: F. notatus, F. olivaceus and F. euryzonus. Both F. notatus and F. olivaceus have broad overlapping ranges with many populations being found within and outside of contact zones. Contact zones are generally found in midreaches with F. olivaceus dominating headwaters and F. notatus in larger rivers downstream. Both species share similar ecological niches so the mechanism allowing for stable coexistence in contact zones is unknown. The purpose of this study was to examine variability in diet and feeding morphology of F. notatus in syntopic and allotopic populations across three drainages. Both Fundulus species were sampled in Pascagoula River, Pearl River and Neches River contact zones in the summer of 2008. Fish were genotyped and feeding-related morphometrics were taken (standard length, body width, body depth, head length, head width, head depth, interorbital distance, preorbital length, orbit length, postorbital length, gape width, gape height, maxillary length, and dentary length). Morphometric analyses were conducted to determine if there were ontogenetic shifts or sexual dimorphisms in allotopic and syntopic populations. Analyses were also conducted to determine if there were differences among species and syntopic-allotopic populations. Digestive tracts of the F. notatus were examined to determine prey items. There were significant differences in feeding-related morphometrics between age classes, sexes, and syntopic and allotopic populations for both Fundulus. There were also significant differences in diets of various groups of F. notatus