Biosystematic studies of the Rumex acetosella complex. I. Angiocarpy and chromosome numbers in France

As a sequel to biotaxonomic studies in Belgium, about 110 random population samples of Rumex acetosella L. s.l. from a large part of France were studied. Representatives of this polyploid complex were of common occurrence everywhere except in areas with a subsoil rich in lime. Angiocarpy is wide-spread, but gymnocarpy was only recorded from the French Alps. In contrast to the situation in Belgium, no correlation between the incidence of angiocarpy and a more fertile kind of soil could be established. Diploids (2n = 14) were found in the SE: Massif Central, Montagne Noire, Massif du Maure, and Massif du Mercantour in the Alpes Maritimes (altogether 36 populations); tetraploids (2n = 28, 23 populations recorded) are almost exclusively encountered in the Pyrenees and in the NE part of the Massif Central; and hexaploids (2n = 42, in 32 populations) appeared to be scattered over the remainder of the area studied, with a certain amount of sympatric overlap with the areas of the diploid and of the tetraploid chromosomal races in the Massif Central. In the zones of overlap an appreciable number of hybrids between 2n and 4n, and between 4n and 6n plants were encountered (in 11 populations). By far the large majority of the plants bear angiocarpous fruits irrespective of the level of ploidy, so that the alleged coupling between angiocarpy and diploidy (in the pertaining literature regarded as ”R. angiocarpus Murb.”, with 2n = 14) must be rejected. In the Alpes Maritimes gymnocarpous diploids were found, which may be considered to represent a more primitive taxon among the aggregate. As far as can be ascertained, the distribution pattern of populations of the R. acetosella aggregate is, generally speaking, characteristic of a complex species differentiated during and after the last Ice Ages. In the discussion attention is paid to the possible causes underlying the differences in the distributional patterns (such as vegetative reproduction at higher ploidy levels). In order to obtain a more complete picture of the complex the investigations are being pursued.