The ecology of exotic annual legumes of the northern Mt. Lofty and southern Flinders Ranges of South Australia

[Truncated abstract] This study describes aspects of the ecology of exotic annual legumes that had colonised the croplands of the northern Mt Lofty and southern Flinders Ranges of South Australia. The distribution and abundance of the exotic annual legumes was surveyed across 55 sites in the target area (32o30‘ to 33 o30’ S, 138o to 139o E). The results of the survey were used to describe the influences of climate and soils on the distribution and abundance of populations of species of the Medicago and Trifolium genera. M. minima, M. truncatula and T. glomeratum were the most widely distributed and abundant species of the two genera. Alkalinity, soil carbonate and salinity contents were major influences but within alkalinity classes, rainfall influenced the density of seed banks of the colonising legumes species. Further, the study aimed to understand the role of populational variation in the colonisation of the study area by these exotic legumes. Differences among populations for numerous reproductive traits were detected within species yet these differences were not regularly and generally consistent with decreasing rainfall. The infrequency of population changes associated with increasing aridity could be attributed to limited variation and the structure of that variation in these populations. Greater variation within populations was associated with the presence of morphs, which accounted for a significant proportion of the total variation. This organisation of variation is typical of inbreeding species, which was suggested by a pollen-ovule study. While their incidence was not generally associated aridity, the presence of the morphs had the effect of extending the distribution of species. Increasing aridity influenced the frequency and distribution of T. tomentosum morphs...