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Molecular SexingDr. Susan Jarvi, Research Geneticist, PIERC/PCSU at UH ManoaDr. Paul Banko, Wildlife Biologist, PIERC Project: SIS 5001761. |
| Many factors contributing to the decline and extinction of the honeycreepers appear to be directly or indirectly associated with the introduction of non-native species. Some of these factors are predation, habitat loss, competition, and introduced diseases such as avian malaria and pox. Efforts to save remaining species are currently underway and, for some, involve the artificial manipulation of populations through captive breeding and geographic translocations. Since skewed sex ratios may influence effective population size, genetic drift and ultimately genetic erosion, there is a need for rapid, reliable methods for distinguishing between sexes for species without sexual dimorphism. PCR (polymerase chain reaction) amplification and analyses of CHD (chromodomain-helicase-DNA-binding protein) genes, one of which is W-linked (located on the W chromosome), have proven to be useful in many species of birds (Griffiths et al. 1996; 1998). Here at PIERC, we have found that these PCR tests are applicable, with a high degree of confidence, to at least four species of Hawaiian honeycreepers. |
  I'iwi Vestiaria coccinea 'Amakihi Hemignathus virens |
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  'Apapane Himatione sanguinea Palila Loxioides bailleui |
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The application of molecular techniques to conservation genetics issues can provide important guidance criteria for management of endangered species. The Palila is endangered largely due to habitat loss, threats to food resources, predation and avian disease with the remnant populations currently restricted to high-elevation dry woodlands on Mauna Kea volcano, Hawaii. Studies of the demography of Palila suggests a male bias especially within the after-second-year age group (Lindsey et al. 1995). Because the determination of sex was based on adult plumage characteristics in this study (Lindsey et al. 1995), the sex ratios of nestlings, hatch year and second year birds could only be estimated by birds that were recaptured as adults, thus the sample sizes were very small within those age groups. The PCR-based test will allow more accurate assessment of sex ratios within all age groups so as to help establish when and, perhaps more importantly, why sex ratios appear to be shifting. Another practical use of this technique is to verify the sex of helpers at Palila nests. Thus far, apparently only adult male helpers have been observed feeding nesting females, nestlings and fledglings (Pratt et al. 1997, Miller 1998). This PCR test can be used to verify the sex of helpers that have ambigous plumage characteristics. Geographic translocation of selected groups of Palila to other suitable predator-controlled habitats has shown potential as a management tool for speeding recovery of this species (Fancy et al. 1997). The PCR-based test described here is currently being used as a means for sex determination of endangered Palila using DNA extracted from either feather pulp or whole blood, with the goal of more accurately maintaining the appropriate sex ratios among founding individuals of geographically translocated populations. Literature Cited: Fancy, S.G., Snetsinger, T.J. and Jacobi, J.D. 1997. Translocation of the Palila, an endangered Hawaiian honeycreeper. Pacific Conservation Biology 3:39-46. Griffiths, R., S. Daan and Dijkstra, C., 1996. Sex identification in birds. Proc. R. Soc. Lond. B. 263:1251-1256. Griffiths,R., M.C.Double, K. Orr, and Dawson, R.J., 1998. A DNA test to sex most birds. Mol. Ecol. 7 (8), 1071-1075. Miller, L.J. 1998. Behavioral ecology of juvenile palila (Loxioides bailleui): foraging development, social dynamics, and helping behavior. MS thesis, University of Maryland, College Park, MD. Pratt, T.K., Banko, P.C., Fancy, S.G., Lindsey, G.D. and Jacobi, J.D., Status and management of the Palila, an endangered Hawaiian honeycreeper, 1987-1996. Pacific Conservation Biology vol 3:330-40. |
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