Evolutionary history and eco-climatic diversification in southern African Sisyphus (Coleoptera: Scarabaeidae: Scarabaeinae)

Aim: The high diversity of species in southern Africa has been attributed
to geological and palaeoclimatic factors. The timing of radiations in some
groups is held to be linked to these geoclimatic trends. Using the
Scarabaeinae dung beetle genus, Sisyphus, as a model system, we
investigate how geological uplift and climatic changes in the late
Cenozoic affected its diversification patterns in southern Africa.
Location: southern Africa. Taxon: The dung beetle genus, Sisyphus
Latreille, 1807 (Coleoptera: Scarabaeidae: Scarabaeinae). Methods: A dated
molecular phylogeny of southern African Sisyphus was compared with a
factor analysis of species distribution data that statistically defined
groups of species according to current climatic distribution. We used
these climatic clusters to estimate ancestral ranges using the
‘BioGeoBEARS’ R package. A lineage through time plot was calculated using
the R package ‘APE’. We used Bayesian diversification models (compound
Poisson process on mass extinction times) to test hypotheses on how late
Cenozoic uplift and climatic changes affected speciation and extinction of
Sisyphus. Furthermore, we implemented ecological niche modelling in MaxEnt
to predict the habitat suitability of species under present climatic
conditions. Results: Four species groups defined from factor analysis of
current climatic distribution data are primarily restricted to the moist
summer rainfall region in the northeast. These groups comprise 10 warm,
eastern lowland species; eight eastern savannah species; five cool,
eastern highland species; and just two southwestern low rainfall species.
Chronology of the phylogeny suggests that species diversification occurred
from the mid-Miocene until the Pleistocene, during which the central
southern African plateau was uplifted in tandem with the advent of winter
rainfall and arid climatic zones to the southwest. The estimation of
ancestral ranges suggests that the ancestor of Sisyphus was centred in
eastern low to mid-altitude areas. The diversification model shows no
evidence of an increase in extinction rate during the late Cenozoic uplift
and climatic changes. The speciation rates were constantly higher in the
Miocene to Pliocene, followed by a dramatic drop in speciation rates
during the transition to the Pleistocene. Modelling of habitat suitability
of current species ranges supports the eastern trends in distribution
patterns. Main conclusions: The taxonomic and eco-climatic diversification
of sisyphines is coincident with geological uplift and changes in climate
in east-central southern Africa. However, phylogenetic relationships of
southern African Sisyphus species are not homogenously distributed with
respect to geography and climate.