Testing the “young-species” hypothesis for Alburnus heckeli Battalgil 1944 (Teleostei: Leuciscidae) inhabiting Lake Hazar, Turkey

ABSTRACT. Alburnus heckeli Battalgil 1944 is endemic to Lake Hazar in the Euphrates-Tigris River system (Persian Gulf basin) and shares morphological and molecular characters with the widespread species A. sellal Heckel 1843, except putatively for the number of gill rakers. This study compared morphometric and meristic data for A. heckeli with lentic and lotic populations of A. sellal. The only significant difference was in the number of gill rakers in lotic populations of A. sellal (10–25) vs. lentic populations of A. sellal (26–35) and A. heckeli (28–35). Although our results are consistent with the interpretation of A. heckeli and A. sellal as “young species”, the amiguity of available morphological and molecular sequence data suggest that A. heckeli is best treated as a junior synonym of A. sellal until reliable differences are found.