Joelle C. Y. Lai

Are coral-dwelling crabs monophyletic? A phylogeny of the Trapezioidea (Crustacea : Decapoda : Brachyura)

Many brachyuran crab genera are known to be obligate symbionts on scleractinian corals in shallow tropical seas (e.g. Cymo, Tanaocheles, Domecia, Tetralia, Tetraloides and Trapezia). Most are currently placed in several families and superfamilies, the most prominent being the Trapezioidea, containing Domeciidae, Tetraliidae and Trapeziidae. The distinctness of the domeciids has long been recognised in Domecinae, and finally Domeciidae. Tetraliidae, however, has only recently been recognised when the classical coral obligate family Trapeziidae was split into two families, Trapeziidae sensu stricto and Tetraliidae. Recognition of Tetraliidae, however, has been controversial, and some workers have suggested that it should be regarded as a synonym of Trapeziidae, principally on the basis of carapace morphology and larval features. Using two gene markers, we evaluate the status of Trapezioidea and, in particular, that of Tetraliidae. Our analyses support the distinction between Tetraliidae and Trapeziidae and suggest that crabs have independently colonised hard corals several times.

Phylogeny of Dorippoidea (Crustacea:Decapoda:Brachyura) inferred from three mitochondrial genes

The phylogenetic relationships between 10 of 13 genera of crabs from the superfamily Dorippoidea were investigated using mitochondrial 16S rRNA, 12S rRNA and cytochrome c oxidase subunit I gene sequences. The resultant phylogenetic trees based on the three molecular markers support the division of Dorippidae and Ethusidae as monophyletic families within the Dorippoidea. The inferred inter-generic relationships within Dorippidae concur with groupings based on the overall morphology of the carapace and structures of the male first pleopods.

PRELIMINARY MOLECULAR AND MORPHOLOGICAL STUDY OF THE CALAPPA LOPHOS SPECIES GROUP (DECAPODA:BRACHYURA:CALAPPIDAE)

Abstract The systematics of the Calappa lophos species group is clarified using morphological and molecular data. The phylogeny of some Indo-Pacific species of Calappa is discussed. Two species, C. quadrimaculata Takeda and Shikatani, 1990, and C. guerini (Brito-Capello, 1871), previously synonymised with C. lophos (Herbst, 1782), are shown to be valid species using morphological and molecular data. A new species in the group, C. acutispina, is described from Madagascar. The usefulness of Bayesian inference in elucidating the phylogenetic relationships of some of the species of Calappa based on partial cytochrome oxidase I (COI) sequences is examined.

The systematics of land crabs of the genus Gecarcoidea and recognition of a pseudocryptic species, G. humei, from the eastern Indian Ocean (Crustacea : Decapoda : Gecarcinidae)

Abstract. The gecarcinid genus Gecarcoidea H. Milne Edwards, 1837 is currently represented by two species from the Indo-West Pacific – the widely distributed purple land crab, G. lalandii H. Milne Edwards, 1837, and the red crab endemic to Christmas Island, G. natalis (Pocock, 1889). One species, G. humei (Wood-Mason, 1874), described from the Nicobar Islands, has had a confused taxonomic history, but was treated as a junior synonym of G. lalandii by Türkay (1974) in his revision of the family. In this study, using molecular as well as morphological characters, we show that G. humei is a valid species. Gecarcoidea lalandii and G. humei have distinct non-overlapping distributions throughout much of their range, with G. lalandii occurring in most of South-east Asia and the West Pacific, while G. humei is known only from the eastern Indian Ocean. On Christmas Island, in the eastern Indian Ocean, however, all three species are present. As a result, Christmas Island is the only locality where all extant species of Gecarcoidea are found. The three species can also be separated by differences in live colours and patterns, as well as proportions of the carapace, male abdomen, ambulatory legs and third maxillipeds, and details of the orbits and male first gonopods.

Phylogeny of eriphioid crabs (Brachyura, Eriphioidea) inferred from molecular and morphological studies

The evolutionary relationships of the brachyuran crab superfamily Eriphioidea, commonly known as stone or rubble crabs, are examined. Analysis of three mitochondrial (12S, 16S and COI) and two nuclear loci (18S and Histone 3) was carried out for 51 taxa representing the Carpilioidea, Dairoidea, Eriphioidea, Goneplacoidea, Parthenopoidea, Pilumnoidea, Portunoidea, Pseudozioidea and Xanthoidea. Phylogenetic analyses of molecular data used three methods of inference that recovered similar topologies with minor differences. Maximum parsimony analysis of 20 morphological characters taken from first zoeas of 11 species yielded two equally parsimonious trees and generally supported the molecular analyses. None of the analyses recovered Eriphioidea as monophyletic, and each of the eriphioid families represented by two or more taxa was shown to be polyphyletic in both molecular and larval analyses. This study indicates that the present classification based on adult morphology is incongruent with phylogenetic relationships and that the diagnostic characters the result of convergence (particularly in feeding morphology) rather than shared ancestry.

A new genus for Chlorodiella longimana (H. Milne Edwards) supported by morphology and molecular data, with a preliminary phylogeny of the Chlorodiellinae (Crustacea:Decapoda:Xanthidae)

Abstract. Chlorodiella longimana is the only chlorodielline species presently known from the western Atlantic Ocean. Although C. longimana superficially resembles other species of the genus in general appearance of the carapace, morphological analyses revealed a suite of characters that separate it from all other known species of Chlorodiella – in particular, ambulatory legs having dactyli with a single tip and a basal antennal segment with a lateral flange that extends halfway into the orbital hiatus, excluding the antennal flagellum. In addition, a phylogenetic analysis of the Chlorodiellinae inferred from three mitochondrial markers (12S, 16S, COXI) and a nuclear marker (histone H3), confirms that C. longimana is genetically distinct from its congeners. A new genus, Ratha, is proposed to accommodate C. longimana. In addition, a phylogenetic analysis of six chlorodielline genera indicates that the subfamily is polyphyletic as presently defined.