Insights into the evolution and biogeography of the pea crab genus Austinixa Heard & Manning, 1997 (Decapoda: Brachyura: Pinnotheridae) based on molecular phylogenetics and morphology

Evolutionary and biogeographic perspectives of Austinixa are limited to few studies that focus on phylogenetic relationships. Some species, such as Austinixa leptodactyla , had not yet been included in phylogenetic hypotheses, whereas others had limited geographic sampling. The present study includes A. leptodactyla in a phylogenetic tree for the first time and increases the number of specimens of other species. A Bayesian Inference analysis along with a molecular clock calibrated with fossil and geological data were used to infer times of divergence among groups. Novelly for Austinixa , ancestral distribution and character state reconstructions were carried out. The phylogenetic relationships recovered herein resemble previously published trees and A. leptodactyla is the sister group of A. roblesi . Austinixa aidae is separated into two geographically structured clades. Austinixa and its major subclades diverged in the Miocene. Species-level divergences mostly occurred in the Pliocene. The ancestral distribution of the genus and its major lineages was recovered within the Tropical Northwestern Atlantic province, with separate dispersal events into other areas. Most diagnostic morphological characters are not phylogenetically informative for larger clades and may represent convergences. However, the cardiac ridge crossing the carapace and the morphology of the male first gonopod might be synapomorphies of the genus and its subclades respectively.