Central African dwarf crocodiles found in syntopy are comparably divergent to South American dwarf caimans.

Recent molecular taxonomic advancements have expanded our understanding of crocodylian diversity, revealing the existence of previously overlooked species, including the Congo dwarf crocodile (Osteolaemus osborni) in the central Congo Basin rainforests. This study explores the genomic divergence between O. osborni and its better-known relative, the true dwarf crocodile (Osteolaemus tetraspis), shedding light on their evolutionary history. Field research conducted in the northwestern Republic of the Congo uncovered a locality where both species coexist in sympatry/syntopy. Genomic analysis of sympatric individuals reveals a level of divergence comparable to that between ecologically similar South American dwarf caimans (Paleosuchus palpebrosus and Paleosuchus trigonatus), suggesting parallel speciation in the Afrotropics and Neotropics during the Middle to Late Miocene, 10-12 Ma. Comparison of the sympatric and allopatric dwarf crocodiles indicates no gene flow between the analysed sympatric individuals of O. osborni and O. tetraspis. However, a larger sample will be required to answer the question of whether or to what extent these species hybridize. This study emphasizes the need for further research on the biology and conservation status of the Congo dwarf crocodile, highlighting its significance in the unique biodiversity of the Congolian rainforests and thus its potential as a flagship species.

Monogeneans from Catfishes in Lake Tanganyika. I: Two new species of Bagrobdella (Dactylogyridae) from Auchenoglanis occidentalis (Siluriformes: Claroteidae)

In the framework of the study of Siluriform fish monogeneans of Lake Tanganyika, we described two new species of Bagrobdella Paperna, 1969 from Auchenoglanis occidentalis (Valenciennes, 1840). Bagrobdella vanhovei sp. nov. is characterized by the morphology of its MCO which is unique among its congeners, presenting a non-terminal opening, whereas the other species have a terminal opening, and Bagrobdella vansteenbergei sp. nov. characterized by the size of its hooks, which are almost all of the same size, and its male copulating organ with a unique shape: a sub-terminal opening and no membrane surrounding. The Multivariate analysis done on morphometrical characters shows that the new and already described species are well individualized, except for Bagrobdella parauchenoglanii Akoumba, Pariselle, Tombi & Bilong Bilong, 2017 and Bagrobdella fraudulenta Euzet & Le Brun, 1990 (but these two species are easily distinguishable by their morphology), and that B. vanhovei sp. nov. has a great intra-specific morphometrical variation.

Pattern and timing of diversification in the African freshwater fish genus Distichodus (Characiformes: Distichodontidae).

BACKGROUND: Distichodus is a clade of tropical freshwater fishes currently comprising 25 named species distributed continent-wide throughout the Nilo-Sudan and most Sub-Saharan drainages. This study investigates the phylogenetic relationships, timing of diversification, and biogeographic history of the genus from a taxonomically comprehensive mutilocus dataset analyzed using Maximum Likelihood and Bayesian methods of phylogenetic inference, coalescence-based species-tree estimation, divergence time estimation, and inference of geographic range evolution. RESULTS: Analyses of comparative DNA sequence data in a phylogenetic context reveal the existence of two major clades of similar species-level diversity and provide support for the monophyletic status of most sampled species. Biogeographic reconstruction on a time-scaled phylogeny suggest that the origins of the genus date back to the late Oligocene and that current geographic distributions are the result of a Congo Basin origin followed by dispersal and range expansion into adjacent ichthyofaunal provinces at different times during the evolutionary history of the group. CONCLUSIONS: We present the most comprehensive phylogenetic, chronological, and biogeographic treatment yet conducted for the genus. The few instances of species paraphyly (D. teugelsi, D. fasciolatus) revealed by the resulting phylogenies are likely a consequence of post-divergence introgressive hybridization and/or incomplete lineage sorting due to recent speciation. Historical biogeographic findings are both in agreement and conflict with previous studies of other continent-wide African freshwater fish genera, suggesting a complex scenario for the assemblage of Africa's continental ichthyofaunal communities.