, Volume 36, Issue 2, pp 147-161

Non-adaptive hypothesis of allopatric cytotype distribution inMyosotis lamottiana (Boraginaceae)

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Abstract

In order to provide insight into the possible differentiation withinMyosotis lamottiana, which is a classical example of a species with a disjunct distribution area, a morphological analysis of 12 populations and a chromosome number analysis of 15 populations were made. Conspicuous chromosomal differentiation was observed comprising diploids (2n=22) and tetraploids (2n=44). The diploid chromosome number is reported for the first time for this species. Diploid and tetraploid cytotypes differ in geographical distributions; diploids are restricted to the Massif Central and tetraploids to the Pyrenees, Mt. Picos de Europa and the Cantabrian Mountains. A detailed morphometric analysis, however, revealed no clear-cut differences in the morphology of diploids and tetraploids except for pollen size, which is a character obviously correlated with ploidy level. No obvious ecological differences were observed between the cytotypes. It was concluded that the current disjunct distribution of diploids and tetraploids ofM. lamottiana may be explained by non-adaptive processes rather than by adaptive ones. A morphological description and notes on the nomenclature ofM. lamottiana are presented as well. A lectotype is chosen and designated for the nameMyosotis lamottiana Braun-Blanq.