Low innate immune-gene diversity in the critically endangered orange-bellied parrot (Neophema chrysogaster)

ABSTRACT

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.

KEYWORDS:

• Conservation
• immunogenetics
• Pseudomonas aeruginosa
• Psittacine beak and feather disease

Acknowledgements

We thank DPIPWE OBP Program staff, in particular Shannon Troy and Judy Clarke, and David Phalen (University of Sydney) for assisting with access to OBP disease samples and disease outbreak information, and Scott Ginn (Australian Museum), Leo Joseph and Robert Palmer (Australian National Wildlife Collection) and Joanna Sumner (Museum Victoria) for assisting with access to museum specimens. We are grateful to David Alquezar-Planas for insightful comments on this project as it developed. Our research on OBP genetics is supported by The Linnean Society of NSW Joyce Vickery Research Fund, Nature Foundation SA, Birdlife Australia, the University of Sydney, and the Australian Museum. CEG acknowledges the support of San Diego Zoo Global.

Disclosure statement

No potential conflict of interest was reported by the authors.

Data Deposition

Upon acceptance, representative sequences for all species and loci will be uploaded to NCBI GenBank, and accession numbers provided here.

Ethics Statement

Blood samples used in this study were collected for management purposes, i.e. disease screening and sexing of fledglings under DPIPWE’s Standard Operating Procedures for orange-bellied parrots.

Supplementary material

Supplemental data for this article can be accessed here