|Location||Monash University, School of Biological Sciences|
The genetics of adaptation in invasive species
The Hodgins lab is currently seeking outstanding PhD candidates interested in studying plant ecological genomics (www.hodginslab.com). Our laboratory studies the genetic basis for adaptation in plants. We are particularly interested in using introduced species as a model for studying rapid adaptation. We also study adaptation to climate in forest trees and plant domestication. To address evolutionary questions relating to these topics, we use a combination of genomics, ecological fieldwork and experimental approaches.
The project can commence any time during 2016/17 and will be developed in collaboration with the student (but see potential project descriptions). Teaching is not required for the duration of the PhD (3.5 years in Australia). Research funding as well as attendance in one conference per year is guaranteed.
Successful candidates will be fully funded for 3.5 years with an annual tax-free stipend of approximately $26,000 AUD, which includes tuition and medical cover. Fully funded PhD stipends are available for either international students or domestic students.
Melbourne is diverse and thriving city with a desirable climate. It is one of the most livable cities in the world and is a cultural and recreational hub.
Monash is a member of the Group of Eight, a coalition of top Australian universities recognized for their excellence in teaching and research. The School of Biological Sciences is a dynamic unit with strengths in both ecology and genetics and the nexus between these disciplines.
Please send your CV, a transcript, a brief statement of your research interests and the contact details of two referees to email@example.com.
Potential project descriptions
Replaying the evolutionary tape: the genetics of parallel adaptation Repeated adaptations to similar selective environments certainly occur. The recurrent evolution of pesticide resistance, as well as parallel geographic patterns of flowering time invasive plants stand out as classic case studies. Given the involvement of chance and the myriad of possible ways a species could evolve, why are the phenotypic outcomes often so consistent? Is adaptive evolution of phenotypes to similar environments always highly repeatable, or is our attention diverted to a biased selection of examples? Even if similar phenotypes evolve independently in different geographic regions, are they as alike as they appear: could different genetic mechanisms be responsible in some cases?
This project aims to gain insight into the repeatability of local adaptation, and the genetic constraints that may underlie this, using a set of replicated range expansions along major climatic gradients. The annual plants Cakile maritima and Cakile edentula (both 2n=18) evolved along parallel gradients of great climatic range (over ~30º of latitude) on either side of the North Atlantic in a narrow coastal habitat. They have since undergone human-assisted introductions and subsequent range expansions in multiple regions (e.g. western North America, Australia, New Zealand, Japan, South America). Thus, we can compare local adaptation during range expansions differing in evolutionary timescales (millennia for post-glacial spread in native ranges vs. decades in their exotic ranges) in the same species as well as between species. Moreover, each invasion arises from unique combinations of source and recipient climates. Adaptation is potentially ongoing, since they are still expanding their exotic geographic ranges. These species afford us an exciting opportunity to examine fundamental evolutionary hypotheses about the genetic basis of adaptation outside the laboratory, in ecologically realistic experimental conditions.
Reconstructing the genetics of rapid adaptation using historic DNA
Invasive species are increasingly commonplace as human activities accidentally or intentionally move species or their propagules from place to place. When species are first introduced to a new location they must often contend with new abiotic environments, different species, and a lack of mates. How do introduced species manage to overcome these barriers to their survival and reproduction? In some cases species may be genetically predisposed to thrive in their new environment, or possess high levels of plasticity. In other cases newly introduced populations may have to adapt genetically to their local environments. Although invasive species have substantial economic and environmental consequences, they represent success stories for how organisms can deal with novel environments. These species offer an exciting avenue to address fundamental evolutionary questions, as each introduction can be analogous to a natural experiment where adaptation to local environments can begin anew. The species Ambrosia artemisiifolia is a highly successful invasive species showing strong evidence for rapid local adaptation of flowering time in the introduced range, which mirror patterns observed in the native range.
As introduced species spread and adapt within recent times, we have the unique opportunity to track genetic changes using historic DNA samples from specimens in herbarium collections. Whole genome resequencing of herbarium and contemporary specimens in the introduced ranges of A. artemisiifolia (Europe and Australian) can shed light on the tempo of adaptive evolution during invasion. Importantly, this data may allow us to assess the relative importance of pre-adaptation versus in situ local adaptation during invasion. This whole genome approach has not yet been taken for invasive species, and has the potential to explicitly demonstrate temporal changes in candidate adaptive alleles.
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