Four new caponiids species (Araneae, Caponiidae) from the West Indies and redescription of Nops blandus (Bryant)

Binford

et al. 2018

Preprint

Organismal variation in dispersal ability can directly affect levels of gene flow amongst populations, therefore importantly shaping species distributions and species richness patterns. The intermediate dispersal model of biogeography (IDM) predicts that in island systems, species diversity of those lineages with an intermediate dispersal potential is the highest. We broadly test this prediction, focusing on 'four-jawed spiders' (genus Tetragnatha) of the Caribbean archipelago. First, we report on original sampling of this globally distributed genus with numerous widespread as well as endemic species. We then reconstruct multiple Tetragnatha phylogenies from roughly 300 individuals delineated into 54 putative species. Our results support the monophyly of the four-jawed spiders but reject the monophyly of those lineages that reach the Caribbean, where we find low levels of endemism yet high diversity within Tetragnatha. The chronogram detects a potential early overwater colonization of the Caribbean, and in combination with reconstructed biogeographic history, refutes the possibility of ancient vicariant origins of Caribbean Tetragnatha as well as the GAARlandia landbridge scenario. Instead, biogeographic results hypothesize multiple colonization events to, and from the Caribbean since mid-Eocene to late-Miocene. Tetragnatha seems unique among the arachnids explored so far in comprising some species that are excellent dispersers, and others that are not, perhaps having secondarily lost this dispersal propensity. A direct test of the IDM would require consideration of three categories of dispersers. However, four-jawed spiders do not fit one of these three a priori definitions, but rather represent a more complex combination of attributes of a 'dynamic disperser'.

Section: Discussionsupporting

confidence: 63%

Global biogeography of Tetragnatha spiders reveals multiple colonization of the Caribbean

Čandek¹,

Binford

et al. 2018

Preprint

“…While we do not claim to have thorough regional sampling, we find patterns of local endemism in regions where our sampling is particularly dense, providing the strongest test with available data. Many Caribbean spiders such as Spintharus 44 , Micrathena 125 Selenops 126 and Nops 127 , as well as other arachnid lineages such as Amblypygi 64 and Pseudoscorpiones 63 , demonstrate a similar pattern. The distribution and quantity of SIEs depends on island properties such as maximum elevation, size, isolation and geological age 128–132 .…”

Section: Discussionmentioning

confidence: 89%

Biogeography of the Caribbean Cyrtognatha spiders

Čandek

Binford

et al. 2019

Sci Rep

Island systems provide excellent arenas to test evolutionary hypotheses pertaining to gene flow and diversification of dispersal-limited organisms. Here we focus on an orbweaver spider genus Cyrtognatha (Tetragnathidae) from the Caribbean, with the aims to reconstruct its evolutionary history, examine its biogeographic history in the archipelago, and to estimate the timing and route of Caribbean colonization. Specifically, we test if Cyrtognatha biogeographic history is consistent with an ancient vicariant scenario (the GAARlandia landbridge hypothesis) or overwater dispersal. We reconstructed a species level phylogeny based on one mitochondrial (COI) and one nuclear (28S) marker. We then used this topology to constrain a time-calibrated mtDNA phylogeny, for subsequent biogeographical analyses in BioGeoBEARS of over 100 originally sampled Cyrtognatha individuals, using models with and without a founder event parameter. Our results suggest a radiation of Caribbean Cyrtognatha, containing 11 to 14 species that are exclusively single island endemics. Although biogeographic reconstructions cannot refute a vicariant origin of the Caribbean clade, possibly an artifact of sparse outgroup availability, they indicate timing of colonization that is much too recent for GAARlandia to have played a role. Instead, an overwater colonization to the Caribbean in mid-Miocene better explains the data. From Hispaniola, Cyrtognatha subsequently dispersed to, and diversified on, the other islands of the Greater, and Lesser Antilles. Within the constraints of our island system and data, a model that omits the founder event parameter from biogeographic analysis is less suitable than the equivalent model with a founder event.

“…More recent efforts are a mixture of morphological revisions, for example goblin spiders (Platnick et al, 2011(Platnick et al, , 2012, huntsman spiders (Rheims & Alayón, 2016), and Cyrtognatha (Dimitrov & Hormiga, 2009); molecular phylogeny-based revisions, for example Salticidae (Zhang & Maddison, 2012), Selenops Crews, 2011) and Modisimus (Huber, Fischer & Astrin, 2010); and smaller taxonomic amendments (e.g. Bloom et al, 2014;Sánchez-Ruiz, Brescovit & Alayón, 2015). Almost no taxonomic work on Caribbean cobweb spiders has been conducted since Levi's work in the 1960s.…”

Section: Introductionmentioning

confidence: 99%

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

Zoological Journal of the Linnean Society

Patten

Sargeant

et al. 2017

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.