title: Evolutionary history of true crabs (Crustacea: Decapoda: Brachyura) and the origin of freshwater crabs.
abstract: Crabs of the infra-order Brachyura are one of the most diverse groups of crustaceans with approximately 7,000 described species in 98 families, occurring in marine, freshwater, and terrestrial habitats. The relationships among the brachyuran families are poorly understood due to the high morphological complexity of the group. Here, we reconstruct the most comprehensive phylogeny of Brachyura to date using sequence data of six nuclear protein-coding genes and two mitochondrial rRNA genes from more than 140 species belonging to 58 families. The gene tree confirms that the "Podotremata," are paraphyletic. Within the monophyletic Eubrachyura, the reciprocal monophyly of the two subsections, Heterotremata and Thoracotremata, is supported. Monophyly of many superfamilies, however, is not recovered, indicating the prevalence of morphological convergence and the need for further taxonomic studies. Freshwater crabs were derived early in the evolution of Eubrachyura and are shown to have at least two independent origins. Bayesian relaxed molecular methods estimate that freshwater crabs separated from their closest marine sister taxa ~135 Ma, that is, after the break up of Pangaea (∼200 Ma) and that a Gondwanan origin of these freshwater representatives is untenable. Most extant families and superfamilies arose during the late Cretaceous and early Tertiary.
authors: Institute of Marine Biology, National Taiwan Ocean University, Keelung, Taiwan.
authors: Ling Ming
authors: LM
authors: Tsang
authors: Christoph D
authors: CD
authors: Schubart
authors: Shane T
authors: ST
authors: Ahyong
authors: Joelle C Y
authors: JC
authors: Lai
authors: Eugene Y C
authors: EY
authors: Au
authors: Tin-Yam
authors: TY
authors: Chan
authors: Peter K L
authors: PK
authors: Ng
authors: Ka Hou
authors: KH
authors: Chu
mesh_terms: D000818:Animals; D001483:Base Sequence; D003386:Brachyura / Q000145:classification* / Q000235:genetics*; D004275:DNA, Ribosomal / Q000235:genetics; D019143:Evolution, Molecular; D005580:Fossils; D005618:Fresh Water; D050259:Genes, Mitochondrial; D049810:Genetic Speciation; D008957:Models, Genetic; D010802:Phylogeny; D013997:Time Factors
chemical_list: D004275:DNA, Ribosomal
keywords: Gondwana; Heterotremata; Podotremata; Thoracotremata; freshwater crabs; molecular phylogeny