Paramunida lophia, Cabezas & Macpherson & Machordom, 2009

Cabezas, Patricia, Macpherson, Enrique & Machordom, Annie, 2009, Morphological and molecular description of new species of squat lobster (Crustacea: Decapoda: Galatheidae) from the Solomon and Fiji Islands (South-West Pacific), Zoological Journal of the Linnean Society 156 (3), pp. 465-493 : 487-489

PARAMUNIDA AND PLESIONIDA

The genus Paramunida was identified with high support as a monophyletic group in all of the analyses, confirming the results of previous studies based on morphological and molecular characters ( Baba, 1988; Machordom & Macpherson, 2004). The two new species described, P. lophia sp. nov. and P. salai sp. nov., were recovered as sister lineages, and showed the lowest interspecific average divergence reported for the genus (1.9% for the 16S rRNA gene and 3.1% for the COI gene). Our morphological data support the taxonomic status of these two species, and diagnostic characters were constant in all specimens analysed. Paramunida belone appeared with high support as the sister group of the two new species, and also showed scarce divergence with respect to both species.

Low divergences seem to be a common pattern within this genus, with the exception of the species P. granulata . This last species is characterized by having a very long distomesial spine in the second article of the antennal peduncle, which is clearly shorter in the other species of the genus ( Baba, 1988). This morphological difference, along with spinulation of the dorsal surface of the carapace, supports the divergence of P. granulata from the other species. In contrast, morphological differences between the two new species and P. belone were based on the shape of the antennal peduncle, suggesting that this appendix, as in P. granulata , is of phylogenetic value in the genus.

Specimens of the species P. stichas from the Solomon Islands were compared with others collected in the region of New Caledonia. These analyses differentiated the two areas, indicating a high mean intraspecific divergence of around 1.1% for both genes. The study of the mitochondrial gene ND1 (not included in this study) revealed the same tree topology, with a lower divergence value than the divergence indicated by the two genes analysed here (P. Cabezas, A. Machordom, E. Macpherson., unpubl. data).

Such low divergence values might be explained by a recent speciation event, or by speciation accompanied by slow morphological and molecular changes. This last scenario suggests a slow DNA substitution rate for this complex of species, a phenomenon that has been previously reported in other crabs and lobsters ( Schubart et al., 2001; Groeneveld et al., 2007). A phylogeographic study of the genus in the Indo- West Pacific that is already underway, including morphological and molecular information, will help clarify the taxonomic position of P. stichas in the two regions, and the evolutionary history of the genus (P. Cabezas, A. Machordom, E. Macpherson., unpubl. data).

The genus Plesionida was analysed together with the genus Paramunida because only two of the three species described for the genus could be examined, and because previous studies ( Machordom & Macpherson, 2004) have revealed that the genera are closely related. Our molecular analysis confirmed the taxonomic status of the genus, which had been inferred on the basis of morphological characters ( Macpherson, 2004). Plesionida concava sp. nov. was compared with P. aliena , which is distributed in New Caledonia, Fiji, and Tonga. These two species were resolved with high support as a monophyletic group. A future analysis of the third species described for the genus will complete our knowledge of this group.