Biosystematic notes on Atriplex patula L., A. hastata L., and A. littoralis L. (Chenopodiaceae)

In about 10—15 % of the cases a sharp distinction between Atriplex hastata L., patula L., littoralis L., and glabriuscula Edm. is not possible, both in the field and in the herbarium. In order to establish the status of the ‘intermediates’ a karyological examination was undertaken of 95 samples collected in the Netherlands including both typical specimens and intermediates. It appeared that the specimens clearly representing A. hastata, littoralis, or glabriuscula are diploid (n = 9), but those representing A. patula tetraploid (n = 18). The ‘intermediates’ between A. hastata and patula are either diploid or tetraploid. Hence a sharp distinction between the latter two taxa is only possible on the chromosome number. A similar result was found for the ‘intermediates’ between A. patula and littoralis. It depends on the specific concept one adheres to whether these four taxa should be ranked as species; European botanists usually give them specific rank, their American colleagues infraspecific rank. Autogamy seems to be the rule in these species. This as well as the chromosome numbers found rule out the possibility of hybridization as an explanation for the occurrence of intermediates. I have strong doubts as to the artificial hybrids reported in literature because of the technical difficulties involved and apparently not solved. Special attention has been paid to possible characters to be derived from the leaves, the phyllotaxis, and the bracts. The variation in the leaves of the four species examined is overlapping. The same holds true for the phyllotaxis and the ripe fruits and fruiting bracteoles. An account is given of some abnormalities which have been found during the chromosome countings. An attempt was made to correlate morphological characters of the leaf, especially the leaf-base and leaf-index, and the chromosomes in A. hastata and patula. The results presented in the scatter diagrams show that, though on the whole there is a marked correlation between leafshape and chromosome number, no sharp distinction can be made. Finally a provisional key is given.