As a plant population ecologist, I am interested in the processes that determine abundance and distribution of plant species and genotypes. Through experimentation, survey, sampling, laboratory analysis and modelling, we are able to predict how abundance and distribution change under different conditions and hence what action we might take to manage populations.
This same research philosophy applies to rare species requiring conservation, to invasive species requiring eradication or containment, or to abundant weeds that require control. I have written academic books on Population Dynamics of Weeds (with Martin Mortimer) and Dispersal in Plants: A Population Perspective (with Calvin Dytham and Richard Law); I was also part of the team that wrote the identification book Western Weeds: A Guide to The Weeds of Western Australia. Over 35+ years, my interests have moved from seaweeds, to weeds of agricultural systems and now to the geographic and local dynamics of alien plants and their post-invasion adaptation.
The main focus of my research group is currently the invasion of Australian coastlines by two sea rockets, one from Europe and N. Africa (Cakile maritima), the other from eastern N. America (C. edentula). In a way analogous to the spread of modern man into regions occupied by Neanderthals, the European species has spread into parts of Australia pre-invaded by the N. American species. As the European species spread, C. edentula was eliminated. Sara Ohadi (PhD student, with Peter Ades and Josquin Tibbits) has uncovered multiple introductions of the European species and bi-directional hybridisation between the two species and introgression from C. edentula into C. maritima. There is still much to do to determine why C. edentula is being displaced, but we have lots of hypotheses to test! Our early work on the two species led to the hypothesis that an obligately out-breeding species (such as C. maritima) could overcome this handicap and spread faster, through transient hybridisation with a native or a pre-invaded self-fertile relative (such as C. edentula). We refer to this as an example of invasion "piggy-backing" of species at the same trophic level. Mohsen Mesgaran, postdoc working on an ARC Discovery grant (with Mark Lewis, Uni of Alberta, and Kathleen Donohue, Duke Uni) is modelling the population dynamics of the system We are now working to obtain more reliable estimates of the model parameters for Cakile. Chengjun Li (PhD student) is studying the inheritance of mating systems in crosses between the two species and back-crosses to the parents. He will also be studying the attractiveness of these to insects. There are great opportunities for further postgraduate research on all aspects of this 3-way interaction between pollinators and plants (and a 4-way interaction with a disease! ).
Other recent research projects have included: the use of herbarium databases to estimate invasion lag phases (with Rob Hyndman, Monash Uni, Mohsen Mesgaran); methodology for climatic niche modelling and application to invasive plants (Mohsen Mesgaran, Philipp Robeck); the impact of river flow management on seed dispersal (Joe Greet, with Angus Webb); statistical methods for seed germination prediction (Mohsen Mesgaran, Qi Sun, postgraduate student)); optimising search patterns for hawkweed eradication (Cindy Hauser, with Nick Williams, Kate Giljohann, Mathieu Bonneau); density-dependence of plant architecture and its implications for seed dispersal (with Natalie Kelly, CSIRO); impacts of various kinds (ecological, geomorphological, economic, sociological) caused by coastal invasive plants (with Kath Williams, David Kennedy and Grainne Maguire, Birdlife Australia); ecology and impacts of the coastal invader Sea Wheatgrass (Thinopyrum junceiforme, with Mohsen Mesgaran); and the population ecology of Sea Spurge (Euphorbia paralias, with Susan Ebeling and John Scott, CSIRO).
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Roger Cousens' highlights
FEATURED Journal article
A question of logic: experiments cannot prove lack of an herbicide-resistance fitness penalty
Read moreRoger Cousens' selected work
When Is Hybridisation Helpful Or Harmful To Invaders?
Research Grant
Planting the seeds of sovereignty
NEWS ARTICLE
Inheritance of breeding system in Cakile (Brassicaceae) following hybridization: implicati..
Journal article
Interactions Among Invading Species: Transient Hybridisation And Rates Of Replacement
Research Grant
A weed by any other name
NEWS ARTICLE
How can natural hybridisation between self-compatible and self-incompatible species be bid..
Journal article
Roger Cousens' selected work
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Bachelor of Science
Dalhousie University
Doctor of Philosophy
Wales