Global expansion of a solitary‐social tropical spitting spider shaped by multiple long‐distance dispersals

Abstract

The spitting spider Scytodes fusca is a species complex well known for its unusual hunting technique which involves spitting a venomous sticky silken substance over its prey. Previous studies supposed that S. fusca was native to Central and South America but had expanded to the tropics of almost every continent. We aimed to test the hypothesis of a Neotropical origin for this spider followed by a secondary dispersal to other regions, and to discuss how population expansion occurring in the tropics was driven. We investigated the population structure and spatiotemporal biogeography of the species complex through the culmination of 22 years of comprehensive global sampling using the mitochondrial and nuclear loci (COI, 16S, 18S, 28S, H3 and ITS2). The S. fusca species complex is divided into two clades. One clade comprises the haplotypes from Australasian regions and a haplotype from Baja Peninsula, Mexico. The other is composed of the haplotypes from all analyzed regions including Asia, Australia, the Americas and Madagascar. Populations from the Americas and Madagascar exhibit a lower genetic diversity compared with the Australasian population, and both have different population demographic histories. The initial divergence within the species complex started during the early Miocene. Diversifications of both clades occurred during the late Miocene. One haplotype was recently and widely dispersed into Southeast Asia, South Asia, Australia, the Americas and Madagascar. Our results elucidate the history of the global spread of the S. fusca species complex, suggesting a Malay Archipelago origin, two expansion routes and its multiple dispersals into the Americas. These stem from a common native source population, as well as from Australia, Fiji, French Polynesia or Turks and Caicos bridgeheads. Our data support the view that the expansion of the S. fusca species complex from Australasia to America and Madagascar was facilitated by long‐distance jump dispersal events.