Cytological studies on the Sino-Himalayan endemic Anisodus and four related genera from the tribe Hyoscyameae (Solanaceae) and their systematic and evolutionary implications

Abstract

Cytological studies were carried out on eight species of five genera (Anisodus, Atropanthe, Hyoscyamus, Mandragora and Przewalskia) in the tribe Hyoscyameae (Solanaceae). First chromosome counts were reported in six species: Anisodus luridus, A. acutangulus, A. tanguticus, A. carniolicoides, Atropanthe sinensis and Mandragora caulescens, all with 2n = 8x = 48. Two records, for Hyoscyamus niger (2n = 2x = 34) and Przewalskia tangutica (2n = 4x = 44), were also confirmed. All species studied showed the proximal type of mitotic prophase chromosome condensation pattern. Three types of interphase nuclei were recognized: the round prochromosome type for Anisodus, Atropanthe and Mandragora, the rod prochromosome type for Przewalskia and the complex chromocentre type for Hyoscyamus. The cytological data supported the close relationship of all four species of Anisodus. Evidence from the interphase nuclei and chromosome base numbers supported the traditional classification of Hyoscyameae into two groups, i.e. Physochlaina praealta+Hyoscyamus (complex interphase type and x = 7, 14, 17) and Przewalskia+Atropanthe+Anisodus+Scopolia+Atropa+Mandragora (prochromosome type and x = 6, 11). Polyploidy is found in most species of the tribe in the Himalayan–Hengduan Mountains, as well as in the Mediterranean region, west–central Asia and eastern Asia. It seems that it probably occurred very early in Hyoscyameae evolution, before the uplift of the Himalayan–Hengduan Mountains. The Himalayan orogeny might have played a minor role in the polyploid evolution of plants in this tribe.

chromosome base number, interphase nuclei, karyotype, prophase chromosome