Paramunida, AND

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 : 484-485

GENERA PARAMUNIDA AND PLESIONIDA

After alignment with other sequences of the genera Paramunida and Plesionida , determined in a previous study ( Machordom & Macpherson, 2004), 1197 bp were finally analysed. The 16S rRNA sequence showed a high variability region between positions 245 and 272, requiring the insertion of gaps.

The partial COI sequence data set obtained for the two new species of the genus Paramunida , and for the new species of Plesionida , consisted of 657 characters, of which 437 were constant, 24 were parsimony uninformative, and 196 were parsimony informative. For the 16S rRNA gene sequence, the resulting data set comprised 540 characters, of which 398 were constant, 36 were parsimony uninformative, and 106 were parsimony informative. Saturation tests revealed no saturation for 16S rRNA and COI when we plotted all substitutions together. Intrageneric divergences within the Paramunida genus were in the range of 1.54–12.05% for the gene 16S rRNA, and of 2.95–17.35% for the COI. The lowest divergences for 16S rRNA were observed between P. salai sp. nov. and P. belone , and the lowest values for the COI sequences were detected between P. salai sp. nov. and P. lophia sp. nov.

For the genus Plesionida , the divergence between P. aliena and P. concava sp. nov. was 5.7% for 16S rRNA, and 10.85% for COI. The ILD test indicated no significant incongruence among gene partitions (P = 0.48), and there were no strong incongruences between the tree topologies, so both genes were analysed in a single matrix, and only the results of the combined data set are provided here.

The model that best fitted this combined data set was the GTR + I + G model ( Lavane et al., 1984; Rodríguez et al., 1990), which gave an a- parameter of 1.4558 and an I-value of 0.6286. Base frequencies were A = 0.3234, C = 0.1371, G = 0.1664, and T = 0.3730, and the proportions of changes were 1.1171, 7.5925, 3.5999, 0.00001, and 17.8696.

The species Onconida alaini Baba & de Saint- Laurent, 1996 was selected as the outgroup, on the basis of previous results ( Machordom & Macpherson, 2004) that showed the genus Onconida as the closest related genus to Paramunida and Plesionida . The monophyly of the genus Paramunida was highly supported by all of the tests ( Fig. 10 ), although not all relationships within the genus were fully resolved. The phylogenetic relationship between the two new species P. salai sp. nov. and P. lophia sp. nov. was highly supported as a sister group, and these two species were in turn the sister group of the species P. belone .

The relationship between the species Paramunida stichas Macpherson, 1993 and Paramunida proxima (Henderson, 1885) was supported by all of the analyses. A comparison between samples of P. stichas from the Solomon Islands and from New Caledonia revealed two different groups separated by a mean divergence of around 1.1% for both genes ( Fig. 10 ).

The last supported cluster included all of the species of the genus, except the species Paramunida granulata (Henderson, 1885) , which always occupied a basal position. Relationships among the remaining species were not resolved.

Our analysis of two of the three species described for the genus Plesionida supported the monophyly of the group, with P. aliena as the sister group of P. concava sp. nov.

Figures

Figure 10. Neighbour-joining (NJ) tree based on the combined data set (16S rRNA and COI genes), showing phylogenetic relationships between Paramunida and Plesionida. Numbers above branches indicate bootstrap values for the NJ and maximum parsimony (MP) analyses. Numbers below branches indicate bootstrap values for the maximum likelihood (ML) analyses and Bayesian posterior probabilities (BPPs).