A radiation of the ornate Caribbean ‘smiley-faced spiders’, with descriptions of 15 new species (Araneae: Theridiidae, Spintharus)

Abstract

Although the Caribbean region is recognized as a major biodiversity hotspot, many megadiverse groups remain taxonomically understudied. The ornate spiders of the genus Spintharus Hentz, 1850 (Theridiidae, Araneae) are a good example where taxonomic boundaries have remained unclear. The genus shows profuse habitus and genitalic variation in the Caribbean and has distinct colour patterns that rapidly degrade in ethanol. The leading theridiid taxonomist of the last six decades (Herbert W. Levi) therefore concluded that the morphological diversity of Caribbean Spintharus was, with the evidence available at the time, best characterized as intraspecific variation. The first molecular study, however, rejected the 'single widespread species' hypothesis, rather indicating multiple short-range endemics. This paper describes and diagnoses 15 new species based on the combination of molecular and morphological data, including S. davidattenboroughi sp. nov., S. barackobamai sp. nov., S. michelleobamaae sp. nov., S. davidbowiei sp. nov., S. leonardodicaprioi sp. nov. and S. berniesandersi sp. nov. Much Caribbean diversity may be similarly 'hidden' by existing taxonomical hypotheses; clearly, more focus is needed on the taxonomy of megadiverse groups. The implications of integrated taxonomy dramatically alter conservation biology when a single widespread species is instead found to represent multiple short-range endemics. Our goal here is thus to update Spintharus taxonomy and discuss the implications of the newly found diversity for both biodiversity research and conservation.

Evidence for Miocene overwater colonization in CaribbeanCyrtognathaspiders

“…As a means of biotic evolution on the Greater Antilles, the GAARlandia hypothesis allows for a combination of overland dispersal and subsequent vicariance and can be tested with the help of time calibrated phylogenies and fossils. While patterns of relationships that are consistent with predictions based on GAARlandia have been found in some lineages 44–48 it is not a good model for explaining the biogeographical history of others 27,29,49,50 .…”

“…Further sampling of these rarely collected spiders in continental America is needed to confirm the timing, number and source of colonization of the Caribbean and to contrast those from other Caribbean spider clades. For example, Spintharus 44,48 and Deinopis (Chamberland et al ‘in review’) patterns clearly support ancient vicariance, but Argiope 27 readily disperses among the islands. Tetragnatha , the sister lineage of Cyrtognatha , may prove to be of particular interest in comparison, because its biogeographic history on the islands may mirror their global tendency towards repeated colonization of even most remote islands.…”

New species of smiley-faced spider Spintharus (Araneae, Theridiidae) from Brazil, and comments on unobserved diversity in South America

“…Therein he redescribed S. gracilis Keyserling from Brazil, and concluded that only one other species could be recognized: S. flavidus Hentz that he characterized as an "extremely variable" and widespread species (Levi 1954: 81). As indicated by later molecular work and systematic revisions (Dziki et al 2015, Agnarsson et al 2018), the profuse variation described by Levi appears to represent a large species complex, rather than one or a few highly variable species. However, the morphological variation makes organization into species level bins challenging, and some related species are arduous to diagnose based on morphology alone.…”

“…Left male pedipalps were removed before being photographed. Diagnostic descriptions of abdominal morphological features follow (Agnarsson et al 2018). Figure 1A Diagnosis.…”

“…However, the morphological variation makes organization into species level bins challenging, and some related species are arduous to diagnose based on morphology alone. Hence, Agnarsson et al (2018) relied heavily on molecular diagnoses, utilizing DNA barcodes.…”