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Birds Evolving Tolerance to Avian Malaria in Hawai'i
Atkinson, C.T., Saili, K.S., Utzurrum, R.B. and Jarvi, S.I. 2013. Experimental evidence for evolved tolerance to avian malaria in a wild population of low elevation Hawai'i 'Amakihi (Hemignathus virens). EcoHealth 10: 366-375.

The authors write that "introduced vector-borne diseases, particularly avian malaria and avian pox virus, continue to play significant roles in the decline and extinction of native forest birds in the Hawaiian Islands." And in this regard they say that "Hawaiian honeycreepers are particularly susceptible to avian malaria and have survived into this century largely because of persistence of high elevation refugia on Kaua'I, Maui and Hawai'I Islands, where transmission is limited by cool temperatures." They note, however, that the long term stability of these refugia could be threatened by future warming. And they say that "since cost effective and practical methods of vector control in many of these remote, rugged areas are lacking, adaptation through processes of natural selection may be the best long-term hope for recovery of many of these species." But is this hope realistic?

What was done
In a study devised to probe this question, Atkinson et al. both discovered and documented what they describe as the "emergence of tolerance rather than resistance to avian malaria in a recent rapidly-expanding low-elevation population of Hawai'I 'Amakihi (Hemignathus virens) on the island of Hawai'i."

What was learned
In rather specific terms, the four researchers determined that "experimentally infected low-elevation birds had lower mortality, lower reticulocyte counts during recovery from acute infection, lower weight loss, and no declines in food consumption relative to experimentally infected high elevation Hawai'I 'Amakihi in spite of similar intensities of infection."

What it means
With respect to the implications of these findings, Atkinson et al. state that the "emergence of this population provides an exceptional opportunity for determining physiological mechanisms and genetic markers associated with malaria tolerance that can be used to evaluate whether other, more threatened species have the capacity to adapt to this disease." And in this regard, they say that their finding "opens the possibility that other native honeycreepers may also be able to adapt to this disease through processes of natural selection," which in turn suggests that this particular mode of evolution may be able to work its wonders far more rapidly than has been believed to be possible in the past.

Reviewed 28 May 2014