Abstract
Locally adapted ecotypes can constitute an important part of the biodiversity, especially in young floras with few endemic species. However, the origins, distinctness and conservation value of many ecotypes remain uncertain because genetic data are lacking or no common-garden study has been carried out. In the present study, we evaluated the distinctness and genetic structure of a phenotypically deviating morph of Rhinanthus angustifolius, growing in calcareous spring fens on the Baltic island of Gotland. Using data from a common-garden experiment and analyses of nuclear microsatellite variation, we compared fen populations on Gotland with conspecific populations from habitats more typical of the study species. We also included the fen specialist R. osiliensis from the Baltic island of Saaremaa in the molecular analyses to make further inferences about the origin of the Gotlandic fen morph. Our data indicate that the Gotlandic fen populations constitute a phenotypically and genetically distinct ecotype that most likely has evolved at least two times on Gotland after the last ice age. In congruence with previous studies, we also infer that fen ecotypes have evolved independently on Gotland and Saaremaa. We propose a varietal status for the Gotlandic fen ecotype and give recommendations for the conservation of this taxon.
Highlights
During the last glacial period, which lasted until about 15.000 ybp, Scandinavia was covered by the thick Weichselian ice sheet (Björck 1995)
In the discriminant function analysis (DFA) of data pooled over blocks, host environments and replicate populations, 41% of the variation in flowering time and plant morphology could be attributed to differences between morphs (1-Wilks lambda = 0.41, P < 0.001). 81% of the individuals were correctly assigned to their original morph when they were re-classified according to the discriminant functions (DFs)
We performed a common-garden experiment and obtained microsatellite data to evaluate the distinctness and taxonomic status of populations of R. angustifolius found in calcareous spring fens on the Baltic island of Gotland
Summary
During the last glacial period, which lasted until about 15.000 ybp, Scandinavia was covered by the thick Weichselian ice sheet (Björck 1995). Many plant species have adapted to local ecological conditions through the formation of phenotypically distinct ecotypes (Turesson 1922). Ecotypes constitute an important part of Scandinavian biodiversity and may be unique, to specific habitats and to the region as a whole (Jonsell 1988). It is important to consider ecotypes and other types of habitat-correlated variation (e.g. clines; Gregor 1938) in order to conserve the genetic diversity and long-term adaptive potential of species that occur in Scandinavia (Lundqvist et al 2007). This work, may be hampered by the lack of consensus regarding the taxonomic treatment of ecotypes, which can be variously treated as subspecies or varieties, or remain unnamed, depending on local traditions and other factors (Hamilton and Reichard 1992; Jonsell 2004). Distinctness and conservation value of ecotypes, it is appropriate to use a combination of molecular-genetic analyses (Lowe et al 2004; Stuessy et al 2014) and common-garden experiments (Heslop-Harrison 1964), and to apply commonly accepted principles to the taxonomic treatment of the entities recognized
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