Subspecies identification with mtDNA and morphometrics in captive palm cockatoos, Probosciger aterrimus

Abstract

The European breeding programme (EEP) for palm cockatoos Probosciger aterrimus has managed two subspecies, P. a. goliath and P. a. aterrimus, separately since it was found that only these two subspecies were distinct genetic lineages. Until recently a captive palm cockatoo was assigned to one or the other subspecies relying solely on morphology, P. a. goliath being reputedly larger than P. a. aterrimus. This study aimed at first to determine the subspecies of 78 captive palm cockatoos – mainly members of the EEP population – by sequencing a mitochondrial marker which had proved relevant for wild specimens. We also collected several anatomical measurements in order to compare the morphology with the molecular marker and to assess the presumed link between morphology and subspecies. Ten different haplotypes were found over 54 non-related samples, which could be arranged into two groups consistent with the subspecies P. a. goliath and P. a. aterrimus. Morphometric analyses revealed significant differences between the two subspecies, although there was some overlap between values for P. a. goliath and P. a. aterrimus. A stepwise discriminant analysis, which included one criterion for females and two criteria for males, allowed a correct assignation of 95% on average for our sample. These results allowed us to confirm that the captive population of palm cockatoos consists of two distinct genetic subgroups, which overall match with morphotypes. Therefore to preserve these two different conservation units we advise that P. a. goliath and P. a. aterrimus continue to be managed as two separate breeding populations. Morphology using a recommended set of measurements gives a fairly reliable insight into the subspecies identity for a newly introduced palm cockatoo, but testing mtDNA is highly recommended to confirm the correct subspecies determination.