Phylogeography of the widespread Caribbean spiny orb weaver Gasteracantha cancriformis

Background. Modern molecular analyses are often inconsistent with pre-cladistic taxonomic hypotheses, frequently indicating higher richness than morphological taxonomy estimates. Among Caribbean spiders, widespread species are relatively few compared to the prevalence of single island endemics. The taxonomic hypothesis Gasteracantha cancriformis circumscribes a species with profuse variation in size, color, and body form. Distributed throughout the Neotropics, G. cancriformis is the only morphological species of Gasteracantha in the New World in this globally distributed genus.

Methods. We inferred phylogenetic relationships across Neotropical populations of Gasteracantha using three target genes. Within the Caribbean, we estimated genetic diversity, population structure, and gene flow among island populations.

Results. Our findings revealed a single widespread species of Gasteracantha throughout the Caribbean, G. cancriformis, while suggesting two recently divergent mainland popu...