The dispersal of microbes among and within flowers by butterflies

Abstract

Abstract Floral microbes, including bacteria and fungi, alter nectar quality, thus changing pollinator visitation. Conversely, pollinator visitation can change the floral microbial community. Most studies on dispersal of floral microbes have focused on bees, ants or hummingbirds, yet Lepidoptera are important pollinators. We asked (a) where are microbes present on the butterfly body, (b) do butterflies transfer microbes while foraging, and (c) how does butterfly foraging affect microbial abundance on different floret structures. The tarsi and proboscis had significantly more microbes than the thorax in wild‐caught Glaucopsyche lygdamus (Lepidoptera: Lycaenidae) and Speyeria mormonia (Lepidoptera: Nymphalidae). Glaucopsyche lygdamus, a smaller‐bodied species, had fewer microbes than S. mormonia. As a marker for microbes, we used a bacterium (Rhodococcus fascians, near NCBI Y11196) isolated from a S. mormonia that was foraging for nectar, and examined its dispersal by G. lygdamus and S. mormonia visiting florets of Pyrrocoma crocea (Asteraceae). Microbial dispersal among florets correlated positively with bacterial abundance in the donor floret. Dispersal also depended on butterfly species, age, and bacterial load carried by the butterfly. Recipient florets had less bacteria than donor florets. The nectaries had more bacteria than the anthers or the stigmas, while anthers and stigmas did not differ from each other. There was no differential transmission among floral organs. Lepidoptera thus act as vectors of floral microbes. Including Lepidoptera is thus crucial to an understanding of plant–pollinator–microbe interactions. Future studies should consider the role of vectored microbes in lepidopteran ecology and fitness.