A CLADISTIC ANALYSIS OF CLAWED LOBSTERS BASED ON AN EXPANDED MORPHOLOGICAL DATA SET

We constructed an expanded morphology-based matrix for the clawed lobsters (Nephropidae) and freshwater crayfish (Astacidae and Cambaridae). Characters (n=81) described the cephalothorax (1-37), antennules (38-44), maxillipeds (45-47), thelycum (48-52), pereiopods (53-60), pleonal tergites, pleurites (61-63) and sternites (64), pleopods (65-73), and telson (74-81). New characters were developed for all, but especially the antennules, thelycum, pereiopods, pleopods and telson. We ran 3 sets of unweighted and weighted (implied weighting) cladistic analyses to produce results directly comparable with: 1) Ahyong and O’Meally, 2004 (morphological and molecular trees for many decapod genera), 2) Ahyong, 2006 (morphological for clawed lobsters), and 3) Tshudy et al., 2009 (molecular for clawed lobsters). In each comparison, we used a taxon set and outgroups identical to that being compared. Implied weighting with K values 5-16 generally gave best resolution. Our morphological results (set 3 of 3) show both agreements and conflicts with the molecular results of Tshudy et al. (2009). Some sister groups are identical; e.g. both methods show Homarus and Nephrops to be closely related, and these to be sister to thaumastochelids. Noteworthy differences include that Nephrops and Metanephrops are sister taxa in this (and previous) morphological analysis, but well separated in the molecular study. Homarinus is another taxon that shows different sister group relationships in morphological and molecular analyses. Comparison (set 1 of 3) with Ahyong and O’Meally (2004) shows little agreement within the group of 4 nephropid genera. New study, instead, gives results corroborating molecular results (Homarus and Thaumastochelopsis a sister group; Metanephrops and Nephropsis a sister group). Comparison (set 2 of 3) with Ahyong (2006) is hampered by the lack of resolution in our trees. It is noteworthy, though, that, in both Ahyong’s tree and in ours, as in other previous morphological analyses, Acanthacaris is a recent branch, while a deeply rooted branch in molecular trees.