The difficulty in accurate species assignments was confounded when only one reference sequence was available; in addition to only a few sequences for closely related species for comparative inter-species purposes. It would be difficult to argue, in a legal context, with any degree of certainty that a sample be assigned to a species without the knowledge of the genetic variability of closely related taxa. Therefore, species level identification was only assigned to those samples when more than one published reference sequence was available for at least one of the two chosen genes for this study, or alternatively, when at least one published sequence was available for both 12S and Cytb genes. We chose a sequence similarity value of >98% for both genes as a requirement for assigning species identity, but acknowledge that more research needs to occur to generate gene specific cut-off values that are appropriate to the Psittaciformes. In cases where only one species reference sequence was available on GenBank, regardless of whether the sequence similarity was >98%, species level identification was not assigned, due primarily to the effects that nuclear copies of mtDNA (numts) might have. Additionally, if the only reference sequence available was from an unpublished source, species identification was not assigned, as we believe they were not deemed fit for this purpose. Genus and family level identification was allocated when search results showed close matches (<98%) to more than one species, involving taxa that were classified within the same genus or family respectively. Our criteria, through necessity, were conservative to minimise the chance of incorrect species assignment. However, it may be likely that each genetic identification needs to be handled on a case-by-case basis and may ultimately become a judgement call based on experience, available evidence, and the quality of reference collections, which are largely the same criteria that a morphological taxonomist might use to identify species. One final complicating factor is the ever-changing nature of the taxonomic framework in which the genus, species and subspecies status of avian taxa can change in response to new data.
การแปล กรุณารอสักครู่..
