Declines in diversity of crane flies (Diptera: Tipuloidea) indicate impact from grazing by livestock in the Hövsgöl region of Mongolia

Threats to biodiversity are not studied equally amongst taxa leaving some groups like insects typically understudied in conservation and management research. Crane flies (Diptera: Tipuloidea) are diverse and important members of the aquatic and terrestrial biotic communities. These semi-terrestrial larval habitat preferences place crane flies at risk of habitat degradation and loss particularly from grazing by livestock. Increased grazing by livestock in the Hövsgöl region of Mongolia has impacted both terrestrial and aquatic ecosystems. The purpose of this study is to document biodiversity of crane flies along the east shore of Lake Hövsgöl, Mongolia, and to test whether crane fly diversity differs between valleys with different grazing intensity. Ninety-six species of Tipuloidea were found in this study, nine of these new to Mongolia, with 21 new to the Hövsgöl region. Rarefaction curves indicate that predicted diversity is less for moderately and highly grazed valleys than for the lightly grazed valleys and an analysis of variance indicates that Shannon’s diversity index was significantly higher in the lightly grazed valleys. Finally, a parsimonious model based on multiple regression analysis indicates that plant biomass and relative humidity are the strongest significant predicators of variation in crane fly diversity across the grazing gradient. Since crane fly larvae are an important part of the soil and leaf litter community, impaired diversity may affect ecosystem services such as decomposition of leaf litter and bioturbation, potentially exacerbating the impact of grazing.