Sonsthagen S.A.,U.S. Geological Survey |
Coonan T.J.,Channel Islands National Park |
Latta B.C.,The Bird Group |
Sage G.K.,U.S. Geological Survey |
Talbot S.L.,U.S. Geological Survey
Gene flow can have profound effects on the genetic diversity of a founding population depending on the number and relationship among colonizers and the duration of the colonization event. Here we used data from nuclear microsatellite and mitochondrial DNA control region loci to assess genetic diversity in golden eagles of the recently colonized Channel Islands, California. Genetic diversity in the Channel Island population was low, similar to signatures observed for other recent colonizing island populations. Differences in levels of genetic diversity and structure observed between mainland California and the islands suggests that few individuals were involved in the initial founding event, and may have comprised a family group. The spatial genetic structure observed between Channel Island and mainland California golden eagle populations across marker types, and genetic signature of population decline observed for the Channel Island population, suggest a single or relatively quick colonization event. Polarity in gene flow estimates based on mtDNA confirm an initial colonization of the Channel Islands by mainland golden eagles, but estimates from microsatellite data suggest that golden eagles on the islands were dispersing more recently to the mainland, possibly after reaching the carrying capacity of the island system. These results illustrate the strength of founding events on the genetic diversity of a population, and confirm that changes to genetic diversity can occur within just a few generations. © 2011. Source
Harvey A.L.,Channel Islands National Park |
Mazurkiewicz D.M.,Sutil Conservation Ecology |
McKown M.W.,Conservation Metrics Inc. |
Barnes K.W.,Sutil Conservation Ecology |
And 2 more authors.
Ashy Storm-Petrels (ASSP) breed in a range restricted to the southern California Current, from Mendocino County in northern California, United States, to the Coronado Islands in northwest Baja California, Mexico. Approximately half the global population nests on the California Channel Islands, but nesting at one of them, Anacapa Island, had not been recorded before this study. In 2011, 10 years af ter rats were eradicated, we conducted a study to determine the breeding status of ASSP on Anacapa Island. We used habitat searches coupled with acoustic sensors to assess potential nesting areas and conducted mist netting to determine general presence. We found one active nest containing a nearly fledged ASSP chick in 2011, representing the first breeding record for the island. © 2016, Marine Ornithology. All rights reserved. Source
Crawled News Article
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Whitworth D.L.,California Institute of Environmental Studies |
Whitworth D.L.,Humboldt State University |
Harvey A.L.,Channel Islands National Park |
Carter H.R.,Carter Biological Consulting |
And 5 more authors.
The first confirmed Cassin’s Auklet Ptychoramphus aleuticus nests at Anacapa Island, California, were found on Rat Rock in May 2003, less than one year after the eradication of Black Rats Rattus rattus in November 2002. By 2012, auklet nesting had been detected in six discrete shoreline areas on the West and East Anacapa islets. We discovered a total of 42 auklet nests (i.e. sites occupied in at least one breeding season) from 2003 to 2012, including 17 confirmed nests (adults, chicks or eggs/eggshells observed) and 25 nests where breeding was inferred (fresh digging, guano streaking or strong auklet odor). Suspected breeding by auklets at Anacapa was first noted in June 1910. By the mid-20th century, rats had restricted breeding auklets to, at most, a few isolated pairs nesting on inaccessible cliffs. However, the population may have been extirpated before rat eradication, as we found no evidence of auklets nesting in any current breeding areas during surveys in 1991, 1994, 1997 and 2000. Subadult and adult auklets captured during nocturnal mist-netting at two current breeding areas in 1994 were likely offspring of isolated cliff-nesting pairs or birds from colonies on nearby islands. Once rats were removed, prospecting by subadult auklets may have facilitated initial colony growth and occupation of some previously unused breeding habitats. Continued searches and nest monitoring are needed to further document post-eradication colony growth. © 2015, Marine Ornithology. All rights reserved. Source
Ross R.M.,University of California at Santa Barbara |
Quetin L.B.,University of California at Santa Barbara |
Newberger T.,National Oceanic and Atmospheric Administration |
Shaw C.T.,Hatfield Marine Science Center |
And 3 more authors.
Marine Ecology Progress Series
The Palmer Long Term Ecological Research study region west of the Antarctic Peninsula is experiencing warming and changing seasonal sea ice dynamics. Abundance patterns of 3 species of pelagic secondary producers were analyzed for trends, cycles, range extensions or shifts in the location of highest density, and for changes in population dynamics over a 16 yr period (1993-2008). Species analyzed represented different hydrographic regimes and are known to have contrasting responses to seasonal sea ice dynamics: krill Euphausia superba, seasonal sea ice zone; tunicates Salpa thompsoni, warmer waters with minimal sea ice; and larval Antarctic silver-fish Pleuragramma antarcticum, cold continental shelf waters. Cycles were observed in grid-wide abundance and recruitment for E. superba. Maximum grid-wide densities did not decrease, but the location of highest densities shifted southward 200 km, away from Adélie penguin rookeries at the northern end. A distinct change post-1999 was apparent in the frequency of occurrence and abundance of S. thompsoni. Mixtures of krill and salps became common, but neither peak densities nor the frequency of peak years for salps increased. As with Antarctic krill, highest salp densities shifted southward alongshore. Larval P. antarcticum were abundant in the northern coastal region in the early 1990s, but virtually disappeared in that region after 1999/2000. Possible mechanisms underlying these observations include the southerly movement of the sea ice edge during spring, changes in proximity of source populations (salps), and changes in transport pathways (larval P. antarcticum). Patterns are compared to those in the SW Atlantic. © Inter-Research 2014. Source