Impacts of warmer temperatures on secondary seed dispersal by Phanaeus vindex dung beetles (Scarabaeinae)

Climate change impacts species interactions with cascading effects on ecosystem functions, including seed dispersal. Studies show that frugivore behaviors and associated seed dispersal are altered under climate change. However, little is known about how climate-induced behavioral shifts of non-frugivores, such as secondary seed dispersers, impact seed fate. Dung beetles are important secondary seed dispersers in many ecosystems because they bury seed-containing dung as either food caches for adult feeding or brood balls for reproduction. We utilized field manipulations with mini-greenhouses to investigate the effects of increased temperature on the seed dispersal behavior of a tunneling dung beetle species, Phanaeus vindex, in Tennessee, USA. Using beads as a proxy for seeds, we found that food caches contained more beads and were buried at shallower depths than brood balls. This suggests that food caches, which have largely been overlooked in previous studies, may play a key role in plant recruitment. Under warmer conditions in mini-greenhouses, we found that beetles buried food caches deeper than under control conditions, but food caches experienced similar temperatures regardless of treatment. For brood balls, we did not find a difference in burial depth or experienced temperatures between treatments. The greater burial depth of seeds in food caches under warmer conditions could adversely impact germination and emergence but could also buffer seeds in seed banks from the adverse effects of warmer surface temperatures. We conclude that climate change can alter secondary seed disperser behavior and thus plant-animal interactions, with ramifications for plant recruitment, community structure, and ecosystem functioning.