Evolutionary convergence in body shape obscures taxonomic diversity in species of the African Labeo forskalii group: Case study of L. parvus Boulenger 1902 and L. ogunensis Boulenger 1910

Hidden species diversity in the Enteromius Cope, 1867 (Teleostei: Cyprinidae) from the Aruwimi basin (Middle Congo) in the Okapi Wildlife Reserve (Democratic Republic of the Congo)

Two new African minnow species, Enteromius cerinus sp. nov. and Enteromius ruforum sp. nov., are described for science from the Angadiko River, a left-bank sub-affluent of first order of the Nepoko River, draining the north-eastern part of the Okapi Wildlife Reserve (OWR). Both new species belong to the group of Enteromius for which the last unbranched dorsal-fin ray is flexible and underrated. Within this morphological group, both are most similar to Enteromius kamolondoensis, especially in life colour pattern characteristics. However, Enteromius cerinus sp. nov. differs from E. kamolondoensis by its low number of circumpeduncular scales, 10-11 (vs. 12), low maximum body depth, 22.8%-25.7% standard length (Ls) (vs. 26.1%-30.0%), and long anterior and posterior barbel lengths, 32.6%-35.3% head length (LH) (vs. 23.6%-27.2%) and 41.6%-43.9% LH (vs. 30.3%-34.9%), respectively. Further, E. ruforum sp. nov. is also easily distinguished from E. kamolondoensis by its high maximum body depth, 30.6%-33.3% Ls (vs. 26.1%-30.0%), and small, isometric, eye diameter, 26.2%-28.0% LH (vs. 29.1%-31.9%). A barcoding study (mtDNA, cytochrome oxidase subunit I [COI]) revealed that specimens of both new species form lineages well differentiated from those of other available species. As such, (i) E. cerinus sp. nov. diverges from E. kamolondoensis by a K2P genetic distance (GD) of 10.3% and (ii) E. ruforum sp. nov. by a K2P GD of 11.2%. To the present day, the fish fauna of the left-bank sub-affluents of the Nepoko River, in general, remains poorly known or undocumented. Unfortunately, at the same time, multiple anthropogenic impacts are affecting this fauna, such as (i) the destruction of habitats along the river banks for agriculture and fishing and (ii) the use of illegal fishing practices, such as fishing with plant-based ichthyotoxins during ecopage, which is combined with dam building. As a result of the demographic growth, this ecopage results in overfishing and thus is threatening both new species in particular, but all other co-occurring fish species as well. Both new species, E. cerinus sp. nov. and E. ruforum sp. nov., should thus be considered Vulnerable (VU) according to IUCN criterion D2. It is therefore hoped that their discovery highlights the urgent need for a better protection and further in situ exploration of the reserve's freshwater (fish) biodiversity, in general, and that of those small sub-affluents, in particular.

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 (220 valid species) 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 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.