Limited divergence in the spatially subdivided population of the Hawaiian mushroom Rhodocollybia laulaha.

Here we report the first population genetic examination of a fungus in Hawaii and, to our knowledge, the only investigation of a saprotrophic fungal population distributed across an oceanic archipelago. Rhodocollybia laulaha fruits abundantly in the native rain forests of Hawaii from June through December. Its range includes the geographic extent of the Hawaiian Archipelago; however, this range is highly fragmented because of the discontinuous distribution of the native forest habitat where R. laulaha occurs. We hypothesized that significant patterns of population structure would be recovered within the geographic range of the Hawaiian mushroom R. laulaha resulting from divergence between isolated subpopulations. We tested for population structure and related inferred patterns of restricted gene flow to geographic distance, major geographic features such as mountain peaks and oceans, elevation zones, and spore morphology. We included 120 R. laulaha collections using data from the rRNA IGS1 region, two microsatellite loci, and 184 AFLP loci. Analyses of these genetic data suggest limited genetic structure among R. laulaha subpopulations in Hawaii correlated mostly with geographic distance. Patterns associated with specialization to elevation or spore morphology were not recovered. The limited geographic structure observed in R. laulaha is consistent with relatively recent population fragmentation. [ABSTRACT FROM AUTHOR]