Friday, December 20, 2013

[Herpetology • 2014] Rigorous Approaches to Species Delimitation have Significant Implications for African crocodilian Systematics and Conservation | Seven Distinct African Crocodile Species Mecistops, Not Just Three

Profile of a Central African Mecistops, a newly recognized cryptic species of slender-snouted crocodile, from Akaka, Loango National Park, Gabon
|  Photo: Zaid Fadul
 paper by Matthew H. Shirley et al. 2014, DOI: 10.1098/rspb.2013.2483

A slender-snouted crocodile in Gabon
|  Photo: Matt Shirley


Accurate species delimitation is a central assumption of biology that, in groups such as the Crocodylia, is often hindered by highly conserved morphology and frequent introgression. In Africa, crocodilian systematics has been hampered by complex regional biogeography and confounded taxonomic history. We used rigorous molecular and morphological species delimitation methods to test the hypothesis that the slender-snouted crocodile (Mecistops cataphractus) is composed of multiple species corresponding to the Congolian and Guinean biogeographic zones. Speciation probability was assessed by using 11 mitochondrial and nuclear genes, and cranial morphology for over 100 specimens, representing the full geographical extent of the species distribution. Molecular Bayesian and phylogenetic species delimitation showed unanimous support for two Mecistops species isolated to the Upper Guinean and Congo (including Lower Guinean) biomes that were supported by 13 cranial characters capable of unambiguously diagnosing each species. Fossil-calibrated phylogenetic reconstruction estimated that the species split ± 6.5–7.5 Ma, which is congruent with intraspecies divergence within the sympatric crocodile genus Osteolaemus and the formation of the Cameroon Volcanic Line. Our results underscore the necessity of comprehensive phylogeographic analyses within currently recognized taxa to detect cryptic species within the Crocodylia. We recommend that the community of crocodilian researchers reconsider the conceptualization of crocodilian species especially in the light of the conservation ramifications for this economically and ecologically important group.

Keywords: Mecistops, Osteolaemus, African biogeography, speciation, probability phylogeography 

Seven Distinct African Crocodile Species, Not Just Three, Biologists Show
— African crocodiles, long thought of as just three known species, are among the most iconic creatures on that continent. But recent University of Florida research now finds that there are at least seven distinct African crocodile species.

 Matthew H. Shirley, Kent A. Vliet, Amanda N. Carr and James D. Austin. 2014. Rigorous Approaches to Species Delimitation have Significant Implications for African crocodilian Systematics and Conservation. Proc. R. Soc. B. 281(1776) 20132483.  doi: