Chromosome survey of Podolepis (Compositae-Inuleae)

Abstract

Meiotic chromosome counts are reported for 23 populations of Podolepis representing 12 of the 18 species, as follows: P. arachnoidea (n = 9), P. auriculata (n = 11), P. canescens (n = 10), P. capillaris (n = 3), P. gardneri (n = 8), P. gracilis (n = 12), P. jaceoides (n = c. 30), P. kendallii (n =11), P. lessonii (n = 7), P. microcephala (n = c. 12), P. neglecta (n =10), and P. rugata (n = 10). The n = 3 (2n = 6) count for P. capillaris is the lowest count found to date for an Australian angiosperm; the chromosome set itself is composed of six large, seemingly identical, "i"-chromosomes. In spite of the extraordinary base series (x = 3, 7, 8, 9, 10, 11, and 12) these are not believed to be due to recent amphiploidy among the species. In general, there appeared to be no marked correlation between low or high basic numbers as regards annual habit and adaptation to xeric conditions. The only polyploid detected was that for P. jaceoides (n = c. 30), a species of more montane habitats. Additional cytophyletic observations are made for several of the species, especially P. microcephala and P. rugata.