Interspecific interactions between burrowing dung beetles and earthworms on yak dung removal and herbage growth in an alpine meadow

Abstract

Interspecific interactions between two spatiotemporally co-occurred species sharing a single resource are considered to be either competitive or facilitative. This study examined the possible interspecific interactions between a dung-tunneling beetle species (Onthophagus yubarinus) and an earthworm species (Aporrectodea nocturna), two major detritivores responsible for dung removal in a Tibetan alpine meadow. We conducted a two-way, factorial field experiment using replicated chambers, and measured the performances of beetles and earthworms, as well as yak dung removal, soil properties and aboveground plant biomass over two months. Earthworm presence significantly decreased the body size of beetle larvae and the weight of tunnel dung that beetle larvae live on. In contrast, beetle presence did not affect the performance of earthworms. Beetles, earthworms and their interaction significantly increased dung removal and soil organic carbon concentration at the end of the experiment. Beetles alone significantly increased soil total N and P, soluble N and P concentrations, but earthworms alone had nonsignificant effects on these nutrient variables. Beetles and earthworms additively enhanced soluble N and P concentrations, and aboveground plant biomass at the end of the experiment. These results indicate 1) there was a onesided negative relationship between dung-tunneling beetles and earthworms, resulting from the consumption of earthworms on food resource of beetle larvae; and 2) the coexistence of beetles and earthworms facilitated dung removal interactively and plant growth additively by increasing nutrient availability.