Endophytes matter: Variation of dung beetle performance across different endophyte-infected tall fescue cultivars

Abstract

Traditional tall fescue cultivar, Kentucky 31, possesses a wild-type endophyte strain that produces several bioactive compounds including the ergot alkaloid, ergovaline, known to cause cattle toxicity and effects on insects. Novel cultivars, BarOptima PLUS E34, Jesup MaxQ, and Texoma MaxQ II, possess different endophyte strains that do not have negative effects on cattle but still protect from insect grazing. Our study investigated if different cultivars have different effects on insect dung decomposers such as dung beetles and determined if ergovaline could be detected in cow dung. Ergovaline at 0.04 and 0.27 μg/g was detected only from Kentucky 31 dung samples from 2017 and 2018 collections, respectively. From the 2017 dung collection, we tested Onthophagus taurus oviposition substrate preferences for each cultivar versus dung from uninfected pasture and also larval survival and development for each dung-type. From the 2018 dung collection, O. taurus and Digitonthophagus gazella oviposition substrate preferences, larval survival and development were tested for Texoma MaxQ II versus Kentucky 31 dung-types. Among the four cultivars, for making brood-balls O. taurus preferred dung from Texoma MaxQ II while dung from Kentucky 31 and BarOptima PLUS E34 were avoided. Both beetle species preferred dung from Texoma MaxQ II versus Kentucky 31 pasture. Larval survival was not affected by dung-type with the 2017 samples. However, with the 2018 samples both beetle species had reduced larval survival on Kentucky 31 than on Texoma MaxQ II brood-balls. Development time for O. taurus was shorter for larvae from Texoma MaxQ II versus Kentucky 31 or uninfected dung brood-balls. Adult mass was not affected in the 2017 collection but was reduced in 2018 Kentucky 31 samples when compared with Texoma MaxQ II. Finally, dung beetles can differentiate dung from pastures with different tall fescue cultivars. Novel cultivar, Texoma MaxQ II, provides more benefits for dung beetles. Pasture renovations with Texoma MaxQ II may improve pasture ecology by enhancing dung beetle populations.