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.

Mitogenomes of two neotropical bird species and the multiple independent origin of mitochondrial gene orders in Passeriformes.

At least four mitogenome arrangements occur in Passeriformes and differences among them are derived from an initial tandem duplication involving a segment containing the control region (CR), followed by loss or reduction of some parts of this segment. However, it is still unclear how often duplication events have occurred in this bird order. In this study, the mitogenomes from two species of Neotropical passerines (Sicalis olivascens and Lepidocolaptes angustirostris) with different gene arrangements were first determined. We also estimated how often duplication events occurred in Passeriformes and if the two CR copies demonstrate a pattern of concerted evolution in Sylvioidea. One tissue sample for each species was used to obtain the mitogenomes as a byproduct using next generation sequencing. The evolutionary history of mitogenome rearrangements was reconstructed mapping these characters onto a mitogenome Bayesian phylogenetic tree of Passeriformes. Finally, we performed a Bayesian analysis for both CRs from some Sylvioidea species in order to evaluate the evolutionary process involving these two copies. Both mitogenomes described comprise 2 rRNAs, 22 tRNAs, 13 protein-codon genes and the CR. However, S. olivascens has 16,768 bp showing the ancestral avian arrangement, while L. angustirostris has 16,973 bp and the remnant CR2 arrangement. Both species showed the expected gene order compared to their closest relatives. The ancestral state reconstruction suggesting at least six independent duplication events followed by partial deletions or loss of one copy in some lineages. Our results also provide evidence that both CRs in some Sylvioidea species seem to be maintained in an apparently functional state, perhaps by concerted evolution, and that this mechanism may be important for the evolution of the bird mitogenome.