Chong, Caroline .
Weed reproduction and dispersal in regulated rivers: genetic connectivity insights.
Understanding the biological processes driving weed invasions in river environments can help improve control and eradication of weed species by allowing for more strategic deployment of management tools, including the seasonal application of hydrological, mechanical, chemical or biological controls. Results are presented of a study that assesses the spatial and genetic impacts of propagules on invasion pattern and genetic connectivity in the Barmah Forest, an internationally recognised Ramsar wetland series on the River Murray floodplain, Victoria, Australia. Natural hydrogeomorphology promotes multi-directional floodwater movement. River regulation has resulted in 50% reduction of winter/spring flooding, altering hydrological and ecological states in the component wetlands of the Forest.
The model species used is Sagittaria platyphylla, an aquatic macrophyte introduced from North America to Australia 50 years ago. S. platyphylla is now recognised as a significant aquatic weed in four Australian states. The distribution of Sagittaria in the Barmah wetlands represents its core range and a dynamic invasion stage comprising many small, dispersed patches and relatively few, large dense stands, providing for a fine-scale genetic approach to assess the invasion front. Clonal (corms) and sexual (seed) offspring may both contribute to genetic structure in Sagittaria, but operate at different spatial scales. Empirical growth studies and molecular genotyping are used as complementary approaches to assess the relative capacity to reproduce and disperse via clonal versus seed propagules, and genetic connectivity among streams in the context of invasive range. Genotypic diversity implicates seed propagation rather than clonal propagules as the major dispersal unit in S. platyphylla. Similar genetic clusters were detected across sampled localities, consistent with multi-directional range expansion in the river-floodplain ecosystem. This is consistent with natural flood patterns within the Barmah Forest and suggests maintained risk of gene flow among streams. Genetic connectivity among sampled localities indicates long-distance seed dispersal (tens of kilometres scale). These findings are considered in the context of improving control and best-practice management for aquatic weeds in regulated rivers.
Weeds are a major threatening process to many riverine ecosystems globally, impacting on native biodiversity, hydrological flows, water quality and availability. Some of the major changes that aquatic weeds can cause include i). restricting water flow and increasing sedimentation, ii). displacing native plant species and limiting opportunities for recruitment, iii). reducing habitat for aquatic species, and, iv. limiting recreational activities, and are additionally associated with significant economic losses. Despite these threats, the demography and dispersal dynamics of many weeds are not well understood in river systems. To improve best-practice management and the cost-effectiveness of control, a useful research framework requires determination of the reproductive modes, likelihood of propagule dispersal and genetic pattern of range expansion in the invasive range in the context of prevailing environmental conditions.
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Research capabilities to protect and restore water ecosystems in Australia
1 - Commonwealth Scientific and Industrial Research Organisation, Plant Industry, Black Mountain Laboratories, Clunies Ross Street, Canberra, ACT, 2601, Australia
Presentation Type: Oral Paper:Papers for Sections
Location: 555B/Convention Center
Date: Tuesday, August 3rd, 2010
Time: 9:30 AM