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Does sex make a difference? Genetic diversity and spatial genetic structure in two co-occurring species of Gagea (Liliaceae) with contrasting reproductive strategies

Research paper by Tanja Pfeiffer, Anja Klahr, Anika Heinrich, Martin Schnittler

Indexed on: 06 Feb '11Published on: 06 Feb '11Published in: Plant systematics and evolution = Entwicklungsgeschichte und Systematik der Pflanzen



Abstract

Gagea lutea and G. spathacea are spring geophytes naturally co-occurring in woodlands, characterised by contrasting reproductive strategies probably caused by divergent ploidy levels. The hexaploid G. lutea relies on vegetative reproduction by subterranean bulbils in young stages but completely switches to sexual reproduction once a certain bulb size is attained. The nonaploid G. spathacea seems to be sterile and reproduces only vegetatively; the plants continue to form bulbils even in the rare event of flowering. This study used AFLP genotyping to investigate the consequences of these reproductive strategies for genetic diversity. For 150 and 100 samples from three Western Pomeranian populations of G. lutea and G. spathacea, respectively, AFLP fingerprints were analysed for three different spatial scales, the patch, the transect, and the region. Applying a threshold for genotypic identity of <0.05 simple matching distance, 22–30 genets were detected in the three G. lutea populations, with all genets confined to single populations. Clonal genets consisted of 2–9 samples and extended over up to 28 m, but never occupied the whole length of a transect; 67–75% of all patches had different genets. Genetic distances between genets within populations were similar to those recorded between populations. Genotyping of G. spathacea revealed a single clonal genet for all three populations sampled within a distance of 30 km. The absent genetic diversity confirms the suspected sexual sterility. Gagea spathacea seems to be one of the few non-apomictic, fully clonal vascular plants able to occupy a significant range solely by dispersal of vegetative diaspores.