The major histocompatibility complex (MHC) of the kiwi (Apteryx spp.) : a thesis submitted for the degree of Master of Science (Molecular Biosciences), Massey University, New Zealand, December 2007

Abstract

This thesis investigates the polymorphism of the Major Histocompatibility Complex (MHC) in the threatened New Zealand Kiwi {Apteryx spp.). The MHC genes are usually highly polymorphic and play a direct role in disease resistance. A lack of MHC polymorphism may affect the ability of a population to respond to continuously evolving pathogens. The Kiwi is a unique bird, endemic to New Zealand, but despite being considered taonga (a treasure) all five kiwi species are threatened and require active management to sustain current population levels. The role of infectious diseases in the kiwi's past and future survival is currently only a matter of conjecture. To analyse the kiwi MHC and its polymorphism, a PCR and primers were designed that amplified the MHC Class II B exon 2, a protein binding region (PBR) and a site where polymorphism is expected. Feather samples from three different kiwi species, the North Island Brown (Apteryx mantelli), the Little Spotted Kiwi (Apteryx owenii), and the Rowi (Apteryx rowi) were used as a non-invasive source of DNA. The MHC results for eight Little Spotted Kiwi from Red Mercury Island showed almost no variation in the form of different alleles between birds. Four putative alleles were shared by all birds, each bird having some or all of the alleles. Rowi are only found in Okarito and are a small population of 250 birds. The 18 birds tested showed a greater range of diversity than expected from a bottled necked population with 14 putative alleles and three pseudogenes. A result more consistent with a remnant population. The twelve North Island Brown birds showed a range of polymorphism: 11 putative alleles and two pseudogenes. Analysis of the Kiwi MHC supports the suggestion that avian MHC sequences evolved by concerted evolution and genetic conversion.