Skip to main content
Dryad

Integrating host use and dispersal ability with species delimitation to unravel a cryptic radiation of photosynthetic sea slugs

Krug, Patrick1

Published Jan 02, 2026 on Dryad. https://doi.org/10.5061/dryad.0gb5mkmff

Data files

Abstract

Species delimitation models are important quantitative tools for facilitating the discovery of cryptic species and clarifying the boundaries between focal taxa. However, distinct evolutionary processes may promote diversification at different points in a radiation, complicating efforts to identify speciation processes and diagnostic characters. Moreover, traits like dispersal ability can have opposing effects on diversification rate versus population subdivision, which causes coalescent models to oversplit samples. In this study, we examined the effects of larval dispersal and host use on population structure and diversity in a Caribbean radiation of photosynthetic herbivores, sea slugs in the genus Elysia. We applied five species delimitation models (SDMs) to molecular datasets, and also performed phylogenetic analyses of evolutionary relationships and population-genetic structure within species. We further modeled ancestral use of host algae using Bayesian Inference methods. Datafiles archived here include input files for analyses such as DNA sequence alignments and Arlequin input files, and also output files generated by the program BayesTraits during ancestral state reconstruction of host use.

The findings broadly supported six described taxa as well as a 7th, previously unrecognized taxon. However, species with less dispersive offspring were often oversplit by SDMs based on the multispecies coalescent. Surprisingly, species that spanned a major phylogeographic break were also likely to be split into multiple taxa by coalescent models, regardless of their dispersal ability. Some host shifts may have contributed to divergence, but others predated speciation, suggesting ecological specialization can promote reproductive isolation but often acted at deeper timescales; recent speciation was more often driven by sea level fluctuations and changes in reproductive anatomy, potentially reinforced by dispersal limitation.