Abstract
Aim: The genus Stasimopus is endemic to South Africa but has
never undergone a phylogeographic review. This study aims to unravel the
phylogeographic patterns and history of the many Stasimopus species
which occur in the greater Karoo region.
Location: The Karoo region, South Africa
Time period: 2017-2018
Major taxa studied: Cork-lid trapdoor spider, Stasimopus(15 species).
Methods: A fossil-calibrated phylogeny was produced based on
three gene regions (CO1, 16S and EF-1ɣ) for Stasimopus specimens
collected in the Karoo region, to infer dates of origin and
diversification. Demographic analyses were performed on species with
sufficient sample sizes (>4). Haplotype networks were
constructed for each gene region and plotted on a map to infer
phylogeographic patterns. Lastly, Mantel tests were performed to test
for isolation by distance.
Results: It was found that 15 species occur in the Karoo and
that the genus radiation in the area is in the early Paleocene. Most
diversification occurred between the late Eocene and the Miocene.
Several species show signals of demographic expansions. Isolation by
distance was detected, but only with a slight correlation.
Main conclusions: It is apparent that aridification has played
a vital role in the diversification of the genus in the Karoo region.
This is a shared biogeographic influence between the mygalomorph fauna
of the Karoo and arid region of western Australia. Stasimopus has
radiated from the late Eocene and through the Miocene resulting in 15
extant species in the region. The Tankwa Karoo has been identified as a
possible Pleistocene glacial cycle refugia for the species S. leipoldti.
Many of the species in the Karoo are short range endemics, making them
of high conservation concern. This study provided vital information as
the Karoo is undergoing further desertification due to factors such as
climate change, which may affect the future of short-range endemic
spiders.