Randall Lea A, Smith Des H V, Jones Breana L, Prescott David R C, Moehrenschlager Axel
Centre for Conservation and Research, Calgary Zoological Society, Calgary, Alberta, Canada.
Centre for Conservation and Research, Calgary Zoological Society, Calgary, Alberta, Canada; Wildland Consultants Ltd., Barrington, Christchurch, New Zealand.
PLoS One. 2015 May 18;10(5):e0127059. doi: 10.1371/journal.pone.0127059. eCollection 2015.
A detailed understanding of the population dynamics of many amphibian species is lacking despite concerns about declining amphibian biodiversity and abundance. This paper explores temporal patterns of occupancy and underlying extinction and colonization dynamics in a regionally imperiled amphibian species, the Northern leopard frog (Lithobates pipiens) in Alberta. Our study contributes to elucidating regional occupancy dynamics at northern latitudes, where climate extremes likely have a profound effect on seasonal occupancy. The primary advantage of our study is its wide geographic scale (60,000 km2) and the use of repeat visual surveys each spring and summer from 2009-2013. We find that occupancy varied more dramatically between seasons than years, with low spring and higher summer occupancy. Between spring and summer, colonization was high and extinction low; inversely, colonization was low and extinction high over the winter. The dynamics of extinction and colonization are complex, making conservation management challenging. Our results reveal that Northern leopard frog occupancy was constant over the last five years and thus there is no evidence of decline or recovery within our study area. Changes to equilibrium occupancy are most sensitive to increasing colonization in the spring or declining extinction in the summer. Therefore, conservation and management efforts should target actions that are likely to increase spring colonization; this could be achieved through translocations or improving the quality or access to breeding habitat. Because summer occupancy is already high, it may be difficult to improve further. Nevertheless, summer extinction could be reduced by predator control, increasing water quality or hydroperiod of wetlands, or increasing the quality or quantity of summer habitat.
尽管人们对两栖动物生物多样性和数量的下降感到担忧，但对许多两栖动物物种的种群动态仍缺乏详细了解。本文探讨了一种在区域内濒危的两栖动物——艾伯塔省的北美豹蛙（Lithobates pipiens）的占用时间模式以及潜在的灭绝和定殖动态。我们的研究有助于阐明北纬地区的区域占用动态，在该地区极端气候可能对季节性占用产生深远影响。我们研究的主要优势在于其广阔的地理范围（60,000平方公里）以及在2009年至2013年期间每年春夏季进行的重复视觉调查。我们发现，占用率在季节之间的变化比年份之间更为显著，春季占用率低，夏季占用率高。在春季和夏季之间，定殖率高而灭绝率低；相反，在冬季定殖率低而灭绝率高。灭绝和定殖的动态很复杂，给保护管理带来了挑战。我们的结果表明，北美豹蛙的占用率在过去五年中保持稳定，因此在我们的研究区域内没有下降或恢复的迹象。平衡占用率的变化对春季定殖率增加或夏季灭绝率下降最为敏感。因此，保护和管理工作应针对可能增加春季定殖的行动；这可以通过转移或改善繁殖栖息地质量或增加其可达性来实现。由于夏季占用率已经很高，可能难以进一步提高。然而，可以通过控制捕食者、提高湿地水质或水文周期，或增加夏季栖息地质量或数量来降低夏季灭绝率。
