The necessity of genetic screening for proper management of captive crocodile populations based on the examples of Crocodylus schuss and C. mindorensis

Abstract

Based on sequences of mitochondrial and nuclear genes, we report on a screening of 11 presumed Nile crocodiles from various European zoos, of which five (from four facilities) turned out to be western Nile crocodiles, Crocodylus suchus, the recently resurrected name applied to the western genetic lineage of Crocodylus niloticus sensu lato. We also provide evidence for a pure species-level genetic background of six additional Crocodylus mindorensis from a European zoo facility, a species that is known to hybridise with Crocodylus porosus. Our results are based on a limited number of genetic markers and thus might miss backcrossed hybrid specimens, but they provide an important basis for the establishment of conservation breeding programmes, already in place for C. mindorensis and contemplated for C. suchus. We found evidence for possible genetic admixture between C. suchus and C. niloticus in a specimen found in Lebanon, possibly representing a released captive-bred hybrid. We reiterate the need for such basic genetic screening especially in morphologically cryptic and poorly studied species in the context of ex-situ conservation breeding, to avoid erroneous species identification and overlooking of unknown evolutionary lineages.