| Summary: | Small-scale heterogeneity of Ranunculus trichophyllus in Lake Tovel (microhabitat, morphology, phenolic compounds and molecular taxonomy) - A water buttercup (Ranunculus trichophyllus Chaix) and a stonewort (Chara aspera Detharding ex Willdenow) are forming the actual macrophyte vegetation in Lake Tovel (Prov. Trento, Italy). Both elements and their similar distribution pattern have already been recorded more than 60 years ago. The two taxa were found in patches near shore and in deep layers not falling dry at all and showed striking morphological differences between the microhabitats. The focus was set on two populations of Ranunculus: one prostrate, vivid green with many fl owers opening above the water surface, common for the shorelines around the lake; the other one, mostly soft, prostrate dark-green to brownish and sterile, found regularily at 3-4 m depth in the shallow SE basin. Potential reasons for this variability are discussed, mainly: (1) extreme environmental gradients leading to a high phenotypic plasticity of one taxon over longer periods in time and (2) hybridisation of two closely related (infraspecifi c) taxa occurring within the larger lake catchment leading to a specifi c littoral ecotype, respectively. The approach to solve this question combines classical biometry with modern chemotaxonomic and genetic analyses (ITS1 sequences documented in this paper). published published
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