Global biogeographic structuring of tropical shallow‐water brittle stars

Abstract

Aim Biogeographic barriers emerged in the tropical oceans as continental masses moved with plate tectonics, and as the tropics contracted to lower latitudes from the late Eocene. These barriers have shaped tropical marine biodiversity. We characterize large‐scale diversity patterns for tropical brittle stars and investigate the effect of biogeographic barriers on these in space and time. Location Shallow‐water (<200 m) tropical oceans. Taxon Tropical shallow‐water brittle stars (class Ophiuroidea). Methods We integrate phylogenetic and biogeographic modelling to test and quantify the biogeographic structuring across the major ocean basins for five families of brittle stars. These are well‐sampled in our phylogenies (173 species) and represent an important component of the brittle star fauna of tropical shallow waters. We define major bioregions based on patterns of compositional and phylogenetic beta diversity. Results We find congruence between patterns of shared ancestry of regions and inferred biogeographic histories. Biogeographic reconstructions show that faunal patterns reflect the emergence of biogeographic barriers in the tropical world, with evidence of vicariant events driven by the opening of the Atlantic Ocean, the narrowing of the Tethyan Seaway and the rise of the Isthmus of Panama. Main conclusions Biogeographic barriers almost completely isolated regional faunas. However, divergence age estimates predate the onset of the different barriers, suggesting that changes associated with the gradual emergence of the barriers had a strong effect on the evolutionary history of tropical shallow‐water brittle stars. Limited, very recent, bi‐directional dispersal was detected across the East Pacific Barrier, which is otherwise an important barrier for dispersal of brittle stars.

Mitochondrial phylogeny of the brittle star genus Ophioderma

“…O. guttatum is an outgroup of O. appressum and O. hendleri . In the phylogeny of Bribiesca-Contreras et al 8 (which does not include O. hendleri ) , O. guttatum is an outgroup to a clade composed of O. squamosissimum and O. vansyoci , but the lower resolution of COI in our data did not provide support for the node joining it with O. squamosissimum . O. appressum and O. hendleri are another amphi-isthmian pair, but probably separated earlier than the completion of the Isthmus (see below).…”

“…The common ancestor of O. holmesii and O. teres split from the common ancestor of O. phoenium and O. cinereum . That O. phoenium and O. cinereum are sister to each other was also shown by Bribiesca-Contreras et al 8 , based on sequence from1462 exons and from COI, and by Christodoulou et al 9 based on the same data, plus sequence from 28S. These studies did not sample O. holmesii but reported that O. peruanum , which we did not sample, is sister to O. teres .…”

“…The members of the majority of geminate species in a variety of organisms were either separated by the protracted emergence of the central American Isthmus before the final closure, or else appear as if they have done so because of the extinction of true geminates 78 , 79 . Bribiesca-Contreras et al 8 show O. variegatum , rather than O. hendleri, as the sister species of O. appressum , but, as O. hendleri had not yet been described at the time of their publication 36 , it is not unexpected that they would assign the specimen they sequenced to O. variegatum. As Granja-Fernandez et al 36 point out, O. hendleri and O. variegatum can easily be confused, because they both have radial shields covered with granules and naked adoral shields.…”

Increase in marine provinciality over the last 250 million years governed more by climate change than plate tectonics

“…The effect of plate tectonics on biogeography is the foundation of vicariance biogeography and evident in phylogenetic patterns [43]. Our results confirm that continental fragmentation also has a direct effect on global provinciality.…”

Influence of elevation on bioregionalisation: A case study of the Sino‐Himalayan flora

“…Furthermore, bioregionalisation provides an essential tool and spatially explicit framework for conservation planning (Crisp & Cook, 2013;Ladle & Whittaker, 2011;Morrone, 2009). Recently, significant progress has been made in the field of bioregionalisation by incorporating evolutionary information from phylogenetic trees (Bribiesca-Contreras et al, 2019;Daru et al, 2020;Ye et al, 2019), instead of solely emphasising the importance of endemic taxa (e.g. Takhtajan, 1978;Wu, 1979) or using taxonomic dissimilarity (e.g.…”