Outbreaks of disease in threatened species can increase the likelihood of extinction by reducing population size. Low immunogenetic diversity can increase susceptibility to, and severity of, disease outbreaks. Our study measured genetic diversity at innate immune genes the Toll-like receptors (TLRs) in a critically endangered Australian bird, the orange-bellied parrot (Neophema chrysogaster). Conservation of this species has recently been challenged by several disease outbreaks. We found low diversity at six TLR genes in both captive and wild orange-bellied parrot populations, similar to results seen in other threatened bird species. Three loci were found to be monomorphic across all samples, including birds which were recorded to have been involved in recent disease events. Phylogenetic analysis of TLR sequences from Neophema chrysogaster as well as representatives of all other species within parrot genera Neophema and Neopsephotus revealed a small number of sites under pervasive and/or episodic positive selection, and a number of sites under negative selection. This study is the first to investigate functional genetic diversity in the orange-bellied parrot.
