Polyploidy is a key process in plant evolution, with the asexual formation of embryos representing a way through which polyploids can escape sterility. The association between polyploidy and polyembryony is known to occur in Bignoniaceae. In this study, we investigate polyembryony in four polyploid species of Anemopaegma: A. acutifolium, A. arvense, A. glaucum and A. scabriusculum as well as in one diploid species, A. album. Polyembryony was observed only in polyploid species. We used seed dissection and germination tests to compare the number of polyembryonic seeds. We tested how the pollen source influences the number of polyembryonic seeds and the number of embryos per seed and tested the correlation between the number of viable seeds per fruit and mean number of embryos per seed. The number of polyembryonic seeds observed by seed dissection was higher than the number of polyembryonic seeds determined by the germination test, with the number of embryos produced per seed being higher than the number of seedlings. The dissection of seeds of A. glaucum indicated that a higher number of polyembryonic seeds and a higher number of embryos were present in seeds from cross-pollination than in seeds from self-pollination. On the other hand, germination tests indicated that a higher number of polyembryonic seeds were present in fruits from self-pollination than from cross-pollination. The mean number of embryos per seed was not influenced by the number of viable seeds per fruit in fruits from open pollination. These results indicate a positive relationship between polyembryony and polyploidy in Anemopaegma.

Summary Anemopaegma (Bignonieae, Bignoniaceae) includes 45 species distributed from Mexico to Northeastern Argentina. The genus is monophyletic and well supported by morphological and molecular characters. However, the delimitation of species within Anemopaegma is complex. In this study, we determined chromosome numbers and interphase nuclei structure for 5 shrubby species of Anemopaegma, 3 of which belong to the Anemopaegma arvense species complex. While most shrubby species analyzed were polyploids (2nϭ4xϭ80), polyploidy was not encountered among the climbing members of the genus. Furthermore, interphase nuclei was shown to vary among species. In particular, A. album was the only species that presented semi-reticulate interphase nuclei, while A. glaucum and A. scabriusculum presented areticulate nuclei. Anemopaegma acutifolium and A. arvense, on the other hand, presented an interphase nuclei structure that was intermediate between the areticulate and semi-reticulate types. Overall, our findings suggest that ploidy level may have had an important role in the diversification of the Neotropical genus Anemopaegma.