Local extinction of a rare plant pollinator in Southern Utah (USA) associated with invasion by Africanized honey bees

Persistence of an imperiled specialist bee and its rare host plant in a protected area

“…The native pollinator faunas of A. humilis at the Beehive Dome site in Utah (surveyed in 1988, 1989, 1993) and A. californica in Nevada (surveyed in 1995) were historically similar, with both composed of the same small specialist bee species, P. meconis, and a larger generalist; E. quadricincta in Utah (Tepedino et al ., ), and M. enceliae in Nevada (Hickerson, ). Yet the Utah fauna at Beehive Dome and other sites has collapsed, with the native bee fauna largely replaced by honey bees (Portman et al ., ). In contrast, the Nevada fauna remains essentially unchanged in 2017, at least in the relatively protected areas we surveyed on LMNRA and BLM land.…”

“…Our findings in Nevada further solidify the hypothesis that the invasion of the AHB is the proximate cause of the collapse of the pollinator guild of A. humilis in Utah (Portman et al ., ). Although, the actions of the AHB have been enabled by several other factors, including habitat loss and fragmentation driven by development and habitat degradation driven by livestock grazing.…”

“…Such boom and bust bloom cycles as seen for Arctomecon are common in desert plants (Beatley, ) yet seem not to dissuade successful specialisation by oligolectic bees whose incidence is high in deserts (Moldenke, ), perhaps because of their ability to remain in extended diapause in dry years (Danforth, ; Minckley et al ., ; Cane et al ., ; Minckley & Roulston, ). Thus, evidence from Nevada supports our earlier interpretation (Portman et al ., ) that inter‐annual variation in host plant numbers per se is an inadequate explanation of the local extinction of P. meconis in Utah.…”

“…A recent example of the import of earlier pollination studies is illustrated by the disruption of the pollinator fauna historically associated with the rare dwarf bearpoppy, Arctomecon humilis Coville (Papaveraceae) (Tepedino et al, 2014;Portman et al, 2018). A species listed as endangered under the U.S.…”

“…Recent studies of A. humilis record the simplification of its historic pollinator guild over the past three decades (Tepedino et al, 2014;Portman et al, 2018). The native species P. meconis and E. quadricincta, formerly abundant visitors of A. humilis at the Beehive Dome site, are now locally extinct or uncommon respectively.…”