1. The Poweshiek skipperling [Oarisma poweshiek (Parker, 1870; Lepidoptera: Hesperiidae)] is a federally endangered butterfly that was historically common in prairies of the upper Midwestern United States and Southern Manitoba, Canada. Rapid declines over the last 20 years have reduced the population numbers to four verified extant sites. The causes of Poweshiek skipperling decline are unknown. 2. We aggregated all known Poweshiek skipperling occurrence records to examine the spatiotemporal patterns of Poweshiek skipperling decline. Ecological niche models were developed for five time frames (1985, 1990, 1995, 2000 and 2005) and three spatial extents (eastern occupied range, western occupied range and total occupied range). We used a backward elimination method to investigate the effects of climate and land use on the ecological niche of Poweshiek skipperling. 3. Predictors of occurrence changed over time and across the geographical extent of Poweshiek skipperling. Land use covariates were retained in east models. In the west and total extent, climate variables contributed the most to model predictive power for the 1985, 1990 and 1995 models; land use variables contributed the most to model predictive power in the 2000 and 2005 models. 4. During the rapid decline in Poweshiek skipperling population numbers occurring at the turn of the century, probability of Poweshiek skipperling presence was being driven by proportion of natural land cover and distance to nearest grassland/wetland. Our results suggest that these land use variables are important landscape‐level variables to consider when developing risk assessments of extant populations and potential reintroduction sites.

中文翻译：

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景观水平的环境压力导致Poweshiek per鱼（Oarisma poweshiek）的衰落

1. Poweshiek per [ Oarisma poweshiek（Parker，1870年；鳞翅目：Hesperiidae）]是一种联邦濒危蝴蝶，历史上在美国中西部上部地区和加拿大曼尼托巴南部地区普遍存在。在过去的20年中，快速下降的人口数量减少到了四个已验证的现存地点。Poweshiek跳水下降的原因尚不清楚。2.我们汇总了所有已知的Poweshiek跳船发生记录，以检查Poweshiek跳船下降的时空模式。针对五个时间框架（1985、1990、1995、2000和2005）和三个空间范围（东部被占领范围，西部被占领范围和总被占领范围）开发了生态位模型。我们使用向后消除方法研究气候和土地利用对Poweshiek per鱼生态位的影响。3。发生的预测因素随着时间的推移以及Poweshiek突击步枪的地理范围发生了变化。土地使用协变量保留在东部模型中。在西部和整个范围内，气候变量对1985、1990和1995年模型的预测能力的贡献最大。在2000年和2005年的模型中，土地利用变量对预测能力的模型贡献最大。4.在世纪之交的Poweshiek越橘种群数量迅速下降的过程中，Poweshiek越橘种群存在的可能性是由自然土地覆盖率和到最近的草地/湿地的距离所驱动。我们的结果表明，这些土地使用变量是重要的景观级变量，在制定现存种群和潜在的引种地点的风险评估时要考虑。