Swengel Ann B, Swengel Scott R
909 Birch Street, Baraboo, WI 53913, USA.
Insects. 2017 Jan 10;8(1):6. doi: 10.3390/insects8010006.
The regal fritillary ("regal") () is endangered in Wisconsin, USA, and declining and at risk range-wide. During 1988-2015, we surveyed 24 known regal sites and >100 areas of potential habitat in Wisconsin. We recorded 9037 individuals in 742.7 km on the peak survey per year at occupied sites. At six sites surveyed over 5-25 years, we found regal fritillaries in only one year, mostly in the latter half of the study. The three populations in the state with more favorable trends than the median had a never-burned refugium and/or infrequent fire management. They also all had substantial amounts of grazing, haying, and/or mowing managements. Sites with trends below the regional median trend had frequent or moderate fire management, and either a diminishing never-burned refugium or none at all. Regal populations at sites with ≤15 ha of grassland have become undetectable. Nonetheless, Hogback, a slightly larger than 15 ha site, had the most favorable trend, a significant increase. Nearly all Wisconsin Regal populations known before 1990 declined to consistent non-findability, even though these were conserved sites. More favorable trends at more recently discovered populations may be attributable to species-specific habitat management protocols implemented in the 1990s. Two sites with better than median long-term trends represent the longest consistent land ownership of known Regal populations in the state. This wide range of population outcomes illustrates both the need for long-term monitoring and the challenges of explaining the outcomes. Despite evidence of increasing Regal dispersal, this species remains very localized, indicating the unsuitability of the wider landscape as regal habitat. The number of significantly declining or no longer detectable populations in Wisconsin indicates an ever more adverse landscape for this species. Sites will need to have habitat characteristics that are ever more optimal in a wide range of climatic conditions for Regal populations to persist.
帝王豹纹蝶（“帝王”）在美国威斯康星州濒临灭绝，且在整个分布范围内数量都在减少并面临风险。1988年至2015年期间，我们对威斯康星州24个已知的帝王蝶栖息地以及100多个潜在栖息地进行了调查。在每年调查高峰期，我们在已占据的栖息地中，沿着742.7公里的区域记录了9037只个体。在6个经过5至25年调查的地点，我们仅在其中一年发现了帝王豹纹蝶，且大多是在研究的后半段时间。该州趋势比中位数更有利的三个种群拥有从未被火烧过的避难所和/或不频繁的火灾管理措施。它们还都有大量的放牧、割干草和/或割草管理措施。趋势低于区域中位数趋势的地点有频繁或适度的火灾管理措施，并且要么从未被火烧过的避难所面积在减少，要么根本没有。草地面积≤15公顷的地点的帝王蝶种群已无法被发现。尽管如此，面积略大于15公顷的霍格巴克山的趋势最为有利，数量显著增加。几乎所有在1990年之前已知的威斯康星州帝王蝶种群都减少到一直无法被发现的程度，尽管这些都是受保护的地点。最近发现的种群中更有利的趋势可能归因于20世纪90年代实施的针对该物种的栖息地管理方案。两个长期趋势优于中位数的地点代表了该州已知帝王蝶种群中持续时间最长的一致土地所有权情况。这种广泛的种群结果既说明了长期监测的必要性，也说明了解释这些结果的挑战。尽管有证据表明帝王蝶的扩散在增加，但该物种仍然非常局限，这表明更广阔的景观不适宜作为帝王蝶的栖息地。威斯康星州数量显著下降或不再能被发现的种群数量表明该物种面临的生存环境日益不利。对于帝王蝶种群的持续存在而言，各个地点将需要具备在广泛气候条件下更加优化的栖息地特征。
