Monocotyledonous geophytes: comparison of south-western Australia with other areas of mediterranean climate

Abstract

Recent data on monocotyledonous geophytes from south-western Australia are compiled and compared with those from other areas of mainly mediterranean climate, especially California, Chile and Victoria, Australia. South-western Australia has a high monocot geophyte diversity of 496 species (7% of an estimated native flora of 7100 vascular species), like Victoria (12%) and the Cape region (14%). As in Victoria, orchids are by far the most important group, with c. 400 species, including those likely to be described once ongoing taxonomic research is completed. South-western Australia has higher geophyte numbers than Victoria in all families considered, but a lower geophyte percentage because of a much higher vascular species total. Among south-western Australian non-orchid geophytes, as in Victoria, the most common storage organ is tuberous roots, followed by corms then bulbs and rhizomes, whereas in California bulbs are by far the most common. The presence of microgeophytes with seed-like storage organs is a special feature seen in several phylogenetically unrelated lineages in the south-western Australian and Victorian geophytic flora, especially on granite outcrops. Divergent phylogenetic history is undoubtedly a major factor underlying striking differences between the monocot geophytes of mediterranean Australia, California, Chile, South Africa and Mediterranean countries. Further studies, particularly on the last two regions, will enable better elucidation of these patterns.