title: Host specificity of two pollinating seed-consuming fly species is not related to soil moisture of host plant in the high Himalayas.
abstract: Studying the drivers of host specificity can contribute to our understanding of the origin and evolution of obligate pollination mutualisms. The preference-performance hypothesis predicts that host plant choice of female insects is related mainly to the performance of their offspring. Soil moisture is thought to be particularly important for the survival of larvae and pupae that inhabit soil. In the high Himalayas,Rheum nobileandR. alexandraediffer in their distribution in terms of soil moisture; that is,R. nobiletypically occurs in scree with well-drained soils,R. alexandraein wetlands. The two plant species are pollinated by their respective mutualistic seed-consuming flies,Bradysiasp1. andBradysiasp2. We investigated whether soil moisture is important for regulating host specificity by comparing pupation and adult emergence of the two fly species using field and laboratory experiments. Laboratory experiments revealed soil moisture did have significant effects on larval and pupal performances in both fly species, but the two fly species had similar optimal soil moisture requirements for pupation and adult emergence. Moreover, a field reciprocal transfer experiment showed that there was no significant difference in adult emergence for both fly species between their native and non-native habitats. Nevertheless,Bradysiasp1., associated withR. nobile, was more tolerant to drought stress, whileBradysiasp2., associated withR. alexandrae, was more tolerant to flooding stress. These results indicate that soil moisture is unlikely to play a determining role in regulating host specificity of the two fly species. However, their pupation and adult emergence in response to extremely wet or dry soils are habitat-specific.
authors.affiliation: Key Laboratory for Plant Diversity and Biogeography of East Asian Kunming Institute of Botany Chinese Academy of Sciences Kunming Yunnan China.
authors.forename: Bo
authors.initials: B
authors.lastname: Song
authors.affiliation: Institute of Botany University of Basel Basel Switzerland.
authors.forename: Jürg
authors.initials: J
authors.lastname: Stöcklin
authors.affiliation: Yunnan Forestry Technological College Kunming Yunnan China.
authors.forename: Yong-Qian
authors.initials: YQ
authors.lastname: Gao
authors.affiliation: Key Laboratory for Plant Diversity and Biogeography of East Asian Kunming Institute of Botany Chinese Academy of Sciences Kunming Yunnan China.
authors.forename: De-Li
authors.initials: DL
authors.lastname: Peng
authors.affiliation: Key Laboratory for Plant Diversity and Biogeography of East Asian Kunming Institute of Botany Chinese Academy of Sciences Kunming Yunnan China.
authors.forename: Hang
authors.initials: H
authors.lastname: Sun
keywords: Bradysia; Rheum; host specificity; offspring performance; soil moisture