title: Fine-scale frequency differentiation along a herbivory gradient in the trichome dimorphism of a wildArabidopsis.
abstract: Geographic variation is commonly observed in plant resistance traits, where plant species might experience different selection pressure across a heterogeneous landscape.Arabidopsis hallerisubsp.gemmiferais dimorphic for trichome production, generating two morphs, trichome-producing (hairy) and trichomeless (glabrous) plants. Trichomes ofA. halleriare known to confer resistance against the white butterfly, cabbage sawfly, and brassica leaf beetle, but not against flea beetles. We combined leaf damage, microclimate, and microsatellite loci data of 26A. halleripopulations in central Japan, to explore factors responsible for fine-scale geographic variation in the morph frequency. We found that hairy plants were less damaged than glabrous plants within populations, but the among-site variation was the most significant source of variation in the individual-level damage. Fixation index (Gst″) of a putative trichome locus exhibited a significant divergence along population-level damage with an exception of an outlier population, inferring the local adaptation to herbivory. Notably, this outlier was a population wherein our previous study reported a balancing role of the brassica leaf beetlePhaedon brassicaeon the morph frequency. This differentiation of the trichome locus was unrelated to neutral genetic differentiation (evaluated by Gst″ of microsatellite loci) and meteorological factors (including temperature and solar radiation). The present findings, combined with those of our previous work, provide suggestive evidence that herbivore-driven divergence and occasional outbreak of a specific herbivore have jointly contributed to the ecogeographic pattern in the frequency of two morphs.
authors.affiliation: Center for Ecological Research Kyoto University Otsu Shiga Japan; Present address: Department of Plant Life Sciences Faculty of Agriculture Ryukoku University Yokotani 1-5, Seta Oe-cho Otsu Shiga 520-2194 Japan.
authors.forename: Yasuhiro
authors.identifier: 0000-0002-6466-723X
authors.initials: Y
authors.lastname: Sato
authors.affiliation: Center for Ecological Research Kyoto University Otsu Shiga Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kudoh
keywords: Arabidopsis halleri; ecogeographic differentiation; plant–herbivore interaction; polymorphism; trichome