Effects of increased temperature on secondary seed dispersal in dung beetles

Climate change is impacting species interactions with cascading effects on key ecosystem functions, including seed dispersal. Studies show that the behaviors of frugivores and associated seed dispersal have been altered under climate change. However, little is known about how behavioral shifts in non-frugivores, such as secondary seed dispersers, in response to climate change will impact seed fate. Dung beetles are important secondary seed dispersers in many ecosystems because they bury seed-containing dung underground as either food caches used for adult feeding or brood balls used for reproduction. We utilized field manipulations with miniature greenhouses to investigate the effects of increased temperatures on the seed dispersal behavior of two tunneling dung beetle species, Phanaeus vindex and Onthophagus taurus, in Tennessee, USA. Using beads as a proxy for seeds, we found that the larger-bodied P. vindex buried more beads than the smaller-bodied O. taurus. We also found that P. vindex food caches contained more beads and were buried at shallower depths than brood balls, suggesting that food caches, which have largely been overlooked in previous studies, may play a larger role in plant recruitment. Under the warmer conditions in greenhouse buckets, we found that P. vindex food caches were buried deeper compared to control buckets, but buried food caches experienced similar temperatures regardless of bucket type. The deeper burial depth of seeds under warmer conditions could adversely impact seed germination and emergence, but may also buffer seeds in soil seed banks from the negative effects of increased surface temperatures.