Facultative parthenogenesis in Cacopsylla myrtilli (Wagner) (Hemiptera: Psylloidea) in northern Sweden: possible explanations for the occurrence of males

摘要

The male of Cacopsylla myrtilli is recorded from Sweden for the first time. Systematic collecting along altitudinal transects in the Abisko area showed that populations at lower elevations within the birch forest consisted entirely of females, implying that this species reproduces parthenogenetically in these habitats. By contrast, males became frequent within the population at or beyond treeline, mirroring similar previous observations in Canada and Norway. Possible mechanisms triggering the switchfrom parthenogenetic to sexual reproduction are discussed.