Identifying closely related species of the genus Gammarus (Crustacea, Amphipoda) using geometric morphometrics

Landmark-Based Geometric Morphometric Methods were used for the first time to quantitatively assess shape variations of the third epimeral plate (Ep۳) of six Gammarus species (G. lordeganensis, G. parthicus, G. pretzmanni, G. pseudosyriacus, Gammarus sp۱ and Gammarus sp۲.) from five different localities in Iran. Two landmarks and ۱۰ semi-landmarks on the posterior, anterior and inferior margins of the Ep۳ were digitized on ۷۸ adult male specimens. Shape diversity of samples and discrimination of all species were analyzed with Principal Components Analysis (PCA) and Canonical Variates Analysis (CVA). The results strongly supported the distinction in the posterior margin of Ep۳ shape of the six species, while the inferior margin clearly showed similar morphological structure. A remarkable separation of G. lordeganensis as a distinct group from the rest of the species was found in both CVA and PCA analyses of anterior margin of Ep۳ shape, while other species had overlaps with each other. Based on these findings, geometric morphometric data, could be used to identify diagnostic morphological traits. The shape of the Ep۳ could be used as an appropriate character for separating closely related amphipod species of the genus Gammarus.

Keywords:

Gammarus , third epimeral plate , geometric morphometric , Shape variation , Iran