The phylogenetic structure and coalescent species delimitation of an endemic trapdoor spider genus, Stasimopus (Araneae, Mygalomorphae, Stasimopidae) in the Karoo region of South Africa

Abstract

The Karoo region of South Africa is a unique and sensitive ecosystem which is facing pressure for development due to economic incentives such as mining, farming and shale gas exploration. The species diversity of many taxa in the area is largely unknown. A phylogenetic analysis of the cork-lid trapdoor spider genus, Stasimopus (Stasimopidae) was undertaken in order to gain insight into the relationships between the species that may be present in the area. The species within Stasimopus are challenging to identify and define using traditional morphological methods due to a high degree of morphological conservatism within the genus. For this reason, multiple coalescent based species delimitation methods were used to attempt to determine the species present for Stasimopus in the region which was tested against the morphological identifications and genetic clades (based on CO1, 16S and EF-1ɣ). We tested single-locus methods Automatic Barcode Gap Discovery (ABGD), Bayesian implementation of Poisson Tree Processes (bPTP) and General Mixed Yule- Coalescent (GMYC), as well as multilocus Brownie. The phylogenetic analysis of Stasimopus in the Karoo showed that there is a high degree of genetic diversity within the genus. The species delimitation results proved unfruitful for the genus, as they appear to delimit population structure rather than species for most methods. Alternative methods should be investigated to aid in the identification of the species in order truly understand the species diversity of the genus.