Do Botanophila flies provide reproductive isolation between two species of Epichloë fungi? A field test.
Epichloë spp., fungal endophytes of cool season grasses, produce collars of mycelium (stromata) on host stems that Botanophila flies visit for egg laying. Flies transfer fungal gametes among stromata and thereby serve to cross-fertilize fungi. Hence, the interaction is analogous to insect pollination in angiosperms. While most Epichloë species are not interfertile, Epichloë typhina and Epichloë clarkii can hybridize. We investigated whether Botanophila flies play a role in the reproductive isolation of the two Epichloë species at a field site in southwestern Switzerland. We estimated the density of stromata and collected fly larvae and stromata occurring on plants. While most ascospores collected from both species indicated intraspecific mating, 9.3% of fungal fruiting bodies contained spores of hybrid origin. Two species of Botanophila larvae occurred on stromata and both preferred E. typhina. Yet, both fly species laid eggs on both fungal species. While preferences by Botanophila flies should influence reproductive isolation between the fungi, other mechanisms are likely more important. Our data, which show hybrid ascospores are produced, suggest postzygotic isolating mechanisms are an important means of reproductive isolation.
Biology Department, Hope College, Holland, MI 49423, USA.
Thomas L
TL
Bultman
Plant Ecological Genetics, Institute of Integrative Biology, ETH Zürich, Universitätstrasse 16, CH-8092 Zürich, Switzerland.
Adrian
A
Leuchtmann
Biology Department, Hope College, Holland, MI 49423, USA.
T J
TJ
Sullivan
Biology Department, Hope College, Holland, MI 49423, USA.
Austin P
AP
Dreyer
D000818:Animals; D004175:Diptera / Q000382:microbiology*; D055329:Epichloe / Q000502:physiology*; D005772:Gastrointestinal Transit / Q000502:physiology; D006790:Host-Parasite Interactions; D007814:Larva; D010802:Phylogeny; D060047:Reproductive Isolation; D013045:Species Specificity; D013172:Spores, Fungal / Q000502:physiology; D013557:Switzerland; D013997:Time Factors
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