Biogeography of Long-Jawed Spiders Reveals Multiple Colonization of the Caribbean

Abstract

Dispersal ability can affect levels of gene flow thereby shaping species distributions and 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. Here, we tested this prediction on long-jawed spiders (Tetragnatha) of the Caribbean archipelago using phylogenies from a total of 318 individuals delineated into 54 putative species. Our results support a Tetragnatha monophyly (within our sampling) but reject the monophyly of the Caribbean lineages, where we found low endemism yet high diversity. The reconstructed biogeographic history detects a potential early overwater colonization of the Caribbean, refuting an ancient vicariant origin of the Caribbean Tetragnatha as well as the GAARlandia land-bridge scenario. Instead, the results imply multiple colonization events to and from the Caribbean from the mid-Eocene to late-Miocene. Among arachnids, Tetragnatha uniquely comprises both excellently and poorly dispersing species. A direct test of the IDM would require consideration of three categories of dispersers; however, long-jawed spiders do not fit one of these three a priori definitions, but rather represent a more complex combination of attributes. A taxon such as Tetragnatha, one that readily undergoes evolutionary changes in dispersal propensity, can be referred to as a ‘dynamic disperser’.

Five new species of the long-jawed orb-weaving spider genus Tetragnatha (Araneae, Tetragnathidae) in South America, with a key to the species from Argentina and Brazil

“…Tetragnatha is a very speciose genus with 321 valid species/subspecies after this work and is among the most common and widespread spiders in the world (Levi 1981;Castanheira et al 2019;Čandek et al 2021;World Spider Catalog 2022). The genus includes species with characteristic cheliceral morphology, with long and numerous diagnostic teeth (see discussion on this structure in Castanheira et al 2019).…”

The seven grand challenges in arachnid science

“…One such massive sampling in the Caribbean archipelago (http://www. islandbiogeography.org/) offered reconstructed biogeographic histories of numerous arachnid clades of varying dispersal propensities (Dziki et al, 2015;Agnarsson et al, 2016;C ̌andek et al, 2019;Tong et al, 2019;C ̌andek et al, 2020a;Chamberland et al, 2020;Crews and Esposito, 2020;C ̌andek et al, 2021;Shapiro et al, 2022). Such multi-clade studies can powerfully test the ultimate biogeographic hypotheses specific to a particular archipelago.…”

Intermediate dispersal hypothesis of species diversity: New insights

“…Dispersal ability also evolves and it may qualitatively change the patterns derived from IDH (Čandek et al, 2021). For example, on oceanic islands where there are few predators, the prey organisms have less need to flee, leading to the evolution of flightless phenotypes (Waters et al, 2020; Wright et al, 2016).…”

“…Although the non‐linear dynamics of single speciation events have been well studied in evolutionary biology (Nosil et al, 2017; Yamaguchi & Iwasa, 2017b), the rate of recurrent speciation has not been considered with sufficient depth in the context of species diversity patterns. From classical to recent studies, life history traits other than dispersal propensity and clade age have been suggested as important contributors to the origin of species diversity (e.g., Čandek et al, 2021; Jablonski, 1986; Marin & Hedges, 2016). The IDH is an attractive and classical hypothesis in evolutionary ecology because it predicts biodiversity despite confounding factors and challenges.…”