Reconstruction of intrageneric relationships within the Indo-West Pacific littoral crab genus Metopograpsus (Decapoda, Brachyura, Grapsidae): an alternative speciation order according to a 28S rDNA molecular phylogeny

Abstract

Abstract The genus Metopograpsus H. Milne Edwards, 1853 is widespread throughout the Indo-West Pacific and currently consists of seven species that can only be separated by minor morphological differences. Therefore, it represents a good example for the usefulness of genetic analyses for identification and classification. In order to obtain phylogenetic information at both lower and higher evolutionary levels, it is best to use a combination of mitochondrial and nuclear molecular markers. Here we present for the first time a molecular phylogeny based on a relative long fragment of the 28S rRNA nuclear gene for the genus Metopograpsus, after application of newly developed primers. Our data suggest an alternative intrageneric speciation order, with M. thukuhar and M. cannicci holding a basal position and a monophyletic grouping of M. frontalis, M. oceanicus and M. quadridentatus, which differs from prior phylogenetic reconstructions. Previously recognized intraspecific phylogeographic patterns in M. latifrons and M. quadridentatus could not be confirmed, due to limited variability of this conserved nuclear gene and due to an incomplete geographic coverage of the corresponding species. In contrast, the previously indicated phylogenetic subdivision within the formerly widespread species M. thukuhar, which led to the recent description of M. cannicci, is here supported.