Abstract
Although Oarisma poweshiek sometimes occurred in localized abundance, its known range is centered on the highly decimated northern tallgrass prairie of North America. To aid its conservation, we analyze surveys from 1988 to 1997 of populations no longer being found. While we recorded 2403 individuals at 20 sites, five sites had 87% of individuals, while 12 sites had only 2% of individuals. Most surveys during O. poweshiek flight had zero individuals recorded. In peak vegetative characteristics for O. poweshiek, fire management had the highest mean abundance but the lowest median abundance and lowest percent occurrence compared to idling and haying. Mean abundance was by far the lowest in the first year postfire compared to longer since fire. Median abundance and percent unit surveys where O. poweshiek was found indicated higher abundances the longer since fire. Although this skipper occasionally exhibited super-recoveries after fire, the median result in fire-managed occupied sites was zero. In a few years, abundance appeared synchronized across many sites, either low (1993, 1997) or high (1994-1995). It is only through a constant focus on avoiding the worst-case scenario that the rare best-case scenario of long-term population persistence appears possible for O. poweshiek.
Highlights
Oarisma poweshiek (Poweshiek skipperling) (Lepidoptera: Hesperiidae) is specialized to native herbaceous flora, with a relatively small range centered on northern tallgrass prairie in North America from eastern Wisconsin to Iowa, Minnesota, the eastern Dakotas, and southeastern Manitoba, as well as populations in fen wetlands in the lower peninsula of Michigan [1,2,3,4,5,6]
Of the 2403 O. poweshiek individuals we formally recorded, nearly half were from one site (Table 1)
O. poweshiek illustrates a frequent scenario in butterfly conservation globally [47, 50]: a species limited in range and site occupancy much more so than its larval host plants [2, 11, 38], even when those habitat patches are as few and fragmented as tallgrass prairie
Summary
Oarisma poweshiek (Poweshiek skipperling) (Lepidoptera: Hesperiidae) is specialized to native herbaceous flora, with a relatively small range centered on northern tallgrass prairie in North America from eastern Wisconsin to Iowa, Minnesota, the eastern Dakotas, and southeastern Manitoba, as well as populations in fen wetlands in the lower peninsula of Michigan [1,2,3,4,5,6]. Since European contact in North America, tallgrass prairie has been about 99% destroyed in most central North American states and provinces, primarily for conversion to agriculture, with never-tilled prairie fragments remaining in preserves, parks, and unintensively utilized farmland [12, 13]. As a result, this skipper has been of conservation concern for decades as evidenced by [11, 14,15,16,17,18,19,20] with decades of unpublished research reports in [6, 21]. Conservation effort has increased [20, 24], but further research on the species’ requirements is hampered by the few populations known still to exist
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