Agro-ecology of Malva parviflora (small-flowered mallow) in the Mediterranean-climatic agricultural region of Western Australia

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[Truncated abstract] Malva parviflora L. (small-flowered mallow) (Malvaceae) is a common weed of pastures and wastelands and its distribution has increased rapidly throughout Australia during the last decade. Control of M. parviflora with herbicides, such as glyphosate, is often unsatisfactory and changing farming practices, such as minimum tillage, have facilitated its spread. Yet there has been little research on M. parviflora in the past and many aspects of its biology and ecology are unknown. Hence, there exists a need to examine these aspects in order to investigate and develop suitable integrated weed management strategies. Weed identification is the first and probably the most important step in the management of weeds. Here it is shown that the weedy Malva species in Western Australian farming systems is M. parviflora, and not a morphologically similar Malva species or hybrid of two species. A common garden study of 24 populations collected across the agricultural region of south-west Western Australia revealed that since its introduction over 140 years ago M. parviflora has successfully adapted to a wide range of distinct environments. The species is able to thrive in areas that vary in annual rainfall from 315 to 496 mm, maximum average temperatures from 21.9 to 26.8oC and minimum average temperatures from 9 to 13.6oC. However, there was limited broad scale ecoclinal differentiation and low genetic variation within the common garden study with only length of time between sowing and flowering differing between populations. As the species was shown to possess a predominately inbreeding system, which typically would create ecotypes/ecoclines due to limited gene flow, it was suggested that seed dispersal by sheep is likely to have increased gene flow thus suppressing population differentiation. A considerable proportion of mature hardseeded M. parviflora can survive rumen digestion and mastication by sheep. ... With origins thought to be in the Mediterranean region, it is not surprising that M. parviflora has thrived and prospered in south-west Western Australia. This thesis has determined several aspects that have enabled it to flourish in this Mediterranean-type environment and most of these attributes, including autogamous reproduction, ecoclinal/ecotypic formation, dormancy and asynchronous germination and rapid seed development, are commonly found in successful weeds world-wide.
Original languageEnglish
QualificationDoctor of Philosophy
StateUnpublished - 2006


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