Patterns and Processes in Population Divergence of Microlaena stipoides (Labill.) R. Br.

Abstract

Morphological, behavioral, and genotypic patterns of variation among the four populations of M. stipoides found growing in association with L. perenne [M (Lpe)], P. pratensis [M (Ppr)], D. glomerata [M (Dgl)] and P. aquatica [M (Paq)] were examined. Microlaena stipoides (Ppr) had narrower leaves than the other populations. Seeds of M (Ppr) weighed significantly less and had a faster rate of germination than the other three populations. Micro/aena stipoides (Ppr) exhibited greater shade tolerance, while M (Dgl) showed greater tolerance to full light. Microlaena stipoides (Dgl) and M (Paq) exhibited a greater tolerance to water stress than M (Ppr) and M (Lpe). Random amplified polymorphic DNA banding patterns of the four populations showed greater base sequence divergence of in M (Ppr) compared with the other three populations. It is suggested that the greater divergence of M (Ppr) from the three other populations resulted from interspecific competition with the associated naturalized perennial species, P. pratensis. Coexistence between M. stipoides populations and introduced and naturalized perennial grass species in pennanent pastures could be due to the balancing of competitive abilities between natural neighboring pairs.

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