Phylogeny of the shore crab family Grapsidae (Decapoda: Brachyura: Thoracotremata) based on a multilocus approach

Abstract

The Grapsidae are a thoracotreme crab family with 40 species in eight genera (in their strict definition), and possess a number of morphological and molecular synapomorphies. Previous phylogenetic studies based on mitochondrial DNA markers established the monophyly of this family, but suggested possible paraphyly or polyphyly of some of the constituent genera. To test the validity of previous hypotheses, the present study reconstructed a molecular phylogeny of the grapsid crabs based on five molecular markers, including mitochondrial DNA markers and the first use of nuclear protein-coding markers to address this issue. Monophyly of Grapsidae was confirmed, with the exception of the position of the monotypic genus Leptograpsodes. The polyphyly of the genus Pachygrapsus is consistent with previous molecular phylogenies, as members from this genus are dispersed throughout our gene tree. Grapsus and Planes were shown to be paraphyletic, with species of Pachygrapsus nested within them. Our study found incongruences between the currently adopted classification of the family, and hence taxonomic revisions will be needed. We hereby demonstrate the use of nuclear protein-coding markers for high confidence reconstruction of decapod phylogenies, resolving most of the early splits that mitochondrial DNA markers alone are unable to tackle.

Hitchhiking the high seas: Global genomics of rafting crabs

“…However, COI data provide little to no resolution of relationships between genera or within species after collapsing nodes with weak bootstrap support (<60%) (Figure ). In this analysis, Pa. laevimanus and Planes form a single clade that is distinct from other grapsid species with high bootstrap support (98%), which is consistent with the paraphyly of Planes due to the well‐supported inclusion of Pa. laevimanus as found by Schubart () and Ip et al (). All COI sequences for Pa. laevimanus and Planes are available on GenBank (Accessions MH931286‐MH931370).…”

“…Our results confirm that the genus Planes is paraphyletic due to its well‐supported relationship with Pa. laevimanus (Ip et al, ; Schubart, ), only with greater taxonomic and geographic depth. The morphological similarity between Planes , especially Pl.…”

“…marinus , and Pachygrapsus has led to taxonomic confusion in the past (Chace, ). However, Pa. laevimanus has never been linked to Planes until genetic data were analyzed (Schubart, ; Ip et al, ; this study). In a novel observation, the affinity between Pa. laevimanus and Planes is evident when comparing male gonopod morphologies: Pa. laevimanus is clearly more similar in shape to Planes (Figure in Chace, ) than to any Pachygrapsus (Figure 15 in Poupin et al, ).…”

Pachygrapsus transversus en Isla de Pascua, ¿De qué especie estamos hablando? (Decapoda, Brachyura, Grapsoidea)

“…Por los antecedentes moleculares obtenidos por Ip et al (2015) y por el análisis de los gonópodos de las especies incluidas en este estudio, se concluye que existen suficientes argumentos para que Pachygrapsus laevimanus deba ser incluido dentro del género Planes. Esto implica que la especie de Grapsidae citada para la Isla de Pascua, como Pachygapsus transversus corresponde en realidad a en realidad a Planes laevimanus el cual ha sido citado erróneamente por diferentes autores.…”

“…En un estudio reciente acerca de las relaciones filogenéticas de la familia Grapsidae, el género Pachygrapsus Randall, 1840 se muestra polifilético (Ip et al 2015), por lo que proponen restringir el género de 14 a sólo 5 especies y considerar a Pa. laevimanus como perteneciente al género Planes Bowdich, 1825 (Ip et al 2015).…”