Data from: Exceptional levels of species discovery ameliorate inferences of the biogeography and diversification of an Afrotropical catfish family

Endeavours in species discovery, particularly the characterisation of
cryptic species, have been greatly aided by the application of DNA
molecular sequence data to phylogenetic reconstruction and inference of
evolutionary and biogeographic processes. However, the extent of cryptic
and undescribed diversity remains unclear in tropical freshwaters, where
biodiversity is declining at alarming rates. To investigate how data on
previously undiscovered biodiversity impacts inferences of biogeography
and diversification dynamics, we generated a densely sampled species-level
family tree of Afrotropical Mochokidae catfishes that was ca. 70%
complete. This was achieved through extensive continental sampling
specifically targeting the genus Chiloglanis a specialist of the
relatively unexplored fast-flowing lotic habitat. Applying multiple
species-delimitation methods, we report exceptional levels of species
discovery for a vertebrate genus, conservatively delimiting a staggering
ca. 50 putative new Chiloglanis species, resulting in a near 80% increase
in species richness for the genus. Biogeographic reconstructions of the
family identified the Congo Basin as a critical region in the generation
of mochokid diversity, and our study further revealed complex scenarios
for the build-up of continental assemblages of the two most species-rich
mochokid genera, Synodontis and Chiloglanis. While Syndontis showed most
divergence events within freshwater ecoregions consistent with largely in
situ diversification, Chiloglanis showed much less aggregation of
freshwater ecoregions, suggesting dispersal as a key diversification
process in this older group. Despite the significant increase in mochokid
diversity identified here, diversification rates were best supported by a
constant rate model consistent with patterns in many other tropical
continental radiations. While our findings highlight fast-flowing lotic
freshwaters as potential hotspots for undescribed and cryptic species
diversity, a third of all freshwater fishes are currently threatened with
extinction, signifying an urgent need to increase exploration of tropical
freshwaters to better characterise and conserve its biodiversity.