Evolutionary divergences mirror Pleistocene paleodrainages in a rapidly-evolving complex of oasis-dwelling jumping spiders (Salticidae, Habronattus tarsalis)

We aimed to understand the diversification history of jumping spiders in
the Habronattus tarsalis species complex, with particular emphasis on how
history in this system might illuminate biogeographic patterns and
processes in deserts of the western United States. Desert populations of
H. tarsalis are now confined to highly discontinuous oasis-like habitats,
but these habitats would have been periodically more connected during
multiple pluvial periods of the Pleistocene. We estimated divergence times
using relaxed molecular clock analyses of published transcriptome
datasets. Geographic patterns of diversification history were assessed
using phylogenetic and cluster analyses of original sequence capture,
RADSeq and morphological data. Clock analyses of multiple replicate
transcriptome datasets indicate mid- to late-Pleistocene divergence dates
within the H. tarsalis group complex. Coalescent and concatenated
phylogenetic analyses indicate four early-diverging lineages (H.
mustaciata, H. ophrys, and H. tarsalis from the Lahontan and Owens
drainage basins), with remaining samples separated into larger clades from
the Mojave desert, and western populations from the California Floristic
Province of California and northern Baja California. Focusing on desert
populations, there is a strong correspondence between RAD lineages and
modern and/or paleodrainages, mirrored more finely in STRUCTURE and
machine learning results. Non-metric multidimensional scaling analysis
reveals a strong congruence between morphological clusters and genetic
lineages, whether the latter represent previously described species or
H.tarsalis RAD lineages. Here we have uncovered a system that adds to our
regional biogeographic knowledge in unique ways, using multiple types of
evidence in a broadly-distributed terrestrial taxon. At the same time, we
have discovered rapid evolution of both novel morphological forms and
diverging genetic lineages. The hierarchical nature of variation in the H.
tarsalis complex, the minute range sizes of many forms, the high
likelihood that geographic distributions have shrunk and expanded through
time, and signs of introgression all align with an ephemeral speciation
model.