Phylogenetic and Geometric Morphometric Approach to Understanding Morphological Adaptations of the Major Chela in the Alpheus brevirostris Species Group

Abstract

Alpheus is a spectacularly diverse genus of snapping shrimp that demonstrate a wide range of adaptations for diverse microhabitats. Traditionally, these shrimps have been categorized into seven morphological species groups using taxonomically informative characters such as the major chelae and the rostrum. A recent phylogenetic analysis of ~65 Alpheus shrimp revealed that five of the seven morphologically defined species groups, including A. brevirostris group, are not monophyletic. Species assigned to the brevirostris group can be distinguished from other species groups by their shovel-shaped major claw. Phylogenetic results reveal that this characteristic claw shape has evolved independently in multiple lineages; the independent origins of their characteristic chelae may be due to convergent evolution for a burrowing lifestyle. Here we use an integrated approach combining geometric morphometrics and molecular phylogenetic reconstructions to test the hypothesis of convergent adaptation for microhabitat. This project will serve as a model for understanding the evolutionary factors promoting morphological diversification of hyper-diverse marine lineages.