Monday, 27 September 2010

Great Gray Owl

Great gray owl research provides evidence that the Sierra Nevada is home to a genetically distinct population, compared to great gray owls outside of California.

Scientists, in 2010, documented Yosemite's great gray owl (Strix nebulosa Yosemitensis) as genetically distinct from the great gray owl in western North America (Strix nebulosa nebulosa). In addition to genetic differences, behavioral differences appear to exist in the Yosemite subspecies. These include differences in migration patterns, prey preference, and nest site selection. Each of these genetic and behavioral characteristics indicates the Sierra Nevada population of great gray owls has been isolated from other populations for an extensive period of time.

Yosemite, today, is the southernmost range and last sanctuary of almost all of California's great gray owls, listed as California State Endangered Species. Researchers estimate there are only about 200 to 300 individuals in California, and about 65% of the state's population resides in Yosemite. Great gray owls nest in the middle elevations of the park where forests and meadows meet. They can be active at any time of the day or night, preferring to hunt in open meadows and clearings within the forest.Then, in winter, they move downslope to snow-free areas where they can more easily access their rodent prey.

This rare and endangered owl is the largest North American owl but also can be found in Asia and Europe. It stands as tall as 2 feet with a 5-foot wingspan and has distinctive piercing yellow eyes accented by large facial disks.

To gain a greater understanding of Yosemite's great gray owl and its genetic make-up, Yosemite joined with the U.S. Forest Service's Pacific Southwest Research Station and geneticists from University of California, Davis to assess genetics, ecological-limiting factors, and immediate management needs of the Sierra-wide population. Great gray owls, restricted to montane meadows, are threatened from mounting resource use in the broader Sierra Nevada. Threats outside the park include timber harvest, grazing, and development pressures.

National parks like Yosemite that provide nearly intact ecosystems are critically important to both identify new species of plants and animals and to provide a laboratory in which to conduct scientific study. Yosemite's research aims to develop a predictive GIS-based habitat model of great gray owl distribution and habitat associations; and design a long-term monitoring plan to assess population trends.

Future genetic research on the great gray owl in Yosemite would help develop a technique to identify individual owls from their molted feathers. This non-invasive research method would allow scientists to study survival rates, reproduction patterns, and other important information through the DNA found in the collected feathers. Additionally, this research method would mitigate negative impacts on the sensitive great gray owl population in the park.
Read the 2010 citation naming the Strix nebulosa Yosemitensis:
Hull, J.M.; Keane, J.J.; Savage, W.K.; Godwin, S.A.; Shafer, J.A.; Jepsen, E.P.; Gerhardt, R.; Stermer, C.; Ernest, H.B. (2010, July). Range-wide genetic differentiation among North American great gray owls (Strix nebulosa) reveals a distinct lineage restricted to the Sierra Nevada, California. Molecular Phylogenetics and Evolution, 56(1), 212-221, DOI: 10.1016/j.ympev.2010.02.027
Mol Phylogenet Evol. 2010 Jul;56(1):212-21. Epub 2010 Mar 1.

Range-wide genetic differentiation among North American great gray owls (Strix nebulosa) reveals a distinct lineage restricted to the Sierra Nevada, California.

Hull JM, Keane JJ, Savage WK, Godwin SA, Shafer JA, Jepsen EP, Gerhardt R, Stermer C, Ernest HB.

Investigations of regional genetic differentiation are essential for describing phylogeographic patterns and informing management efforts for species of conservation concern. In this context, we investigated genetic diversity and evolutionary relationships among great gray owl (Strix nebulosa) populations in western North America, which includes an allopatric range in the southern Sierra Nevada in California. Based on a total dataset consisting of 30 nuclear microsatellite DNA loci and 1938-base pairs of mitochondrial DNA, we found that Pacific Northwest sampling groups were recovered by frequency and Bayesian analyses of microsatellite data and each population sampled, except for western Canada, showed evidence of recent population bottlenecks and low effective sizes. Bayesian and maximum likelihood phylogenetic analyses of sequence data indicated that the allopatric Sierra Nevada population is also a distinct lineage with respect to the larger species range in North America ; we suggest a subspecies designation for this lineage should be considered (Strix nebulosa yosemitensis). Our study underscores the importance of phylogeographic studies for identifying lineages of conservation concern, as well as the important role of Pleistocene glaciation events in driving genetic differentiation of avian fauna.

(Submitted by Chad Arment)

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