Garrick lab
Evolutionary & molecular population biology

Phylogeography

1.    Southern Appalachians, USA

This project seeks to understand how organisms responded to past climatic warming (Last Glacial Maximum to present) with the goal of developing more effective strategies for managing biodiversity under future climate change scenarios. In the past, species responded to rapid environmental change either by persisting in local refuges, or by migration to follow the changing spatial distribution of suitable habitats. However, we currently lack information on how the ecology of a given species interacts with the landscape setting in determining its response to climatic warming. The project will focus on several low-mobility invertebrates that play important functional roles in maintaining forest health, but also live in microhabitats that provide strong contrasts with respect to climatic buffering and stability.


2.    Baja California, Mexico

This project focuses on a suite of Sonoran Desert plant-insect species pairs that exhibit different kinds of ecological interactions. The type of relationship (e.g., host-herbivore vs. pollination mutualism) could dictate the degree to which spatial genetic patterns, and underlying microevolutionary processes, are congruent. Ultimately, we want to disentangle the relative influence of biogeographic and co-evolutionary processes on the evolution of genetic structure. Impacts of past geological and climatic changes on biodiversity of numerous vertebrates from the Baja California peninsula have been well-established, but there are reasons to believe that plants and thier insect pollinators or herbivores responded to past geological and climatic changes in ways that differ from the responses of vertebrates. Moreover, despite the typically strong dispersal ability of flight-capable insects, if the plant-insect association is tight, their responses to past environmental changes may be heavily constrained by the dispersal ability of the host. This study system is being used as a testing-ground for Population Graphs (Dyer & Nason 2004 Mol. Ecol. [Abstract]) - an analytical method for assessing congruence and testing hypotheses (software for implementing the method is available here).

Collaborating labs: Rodney Dyer (Virginia Commonwealth Univ.), John Nason (Iowa State Univ.)

Selected publications: Garrick et al. (2009) Mol. Ecol., Dyer et al. (2010) Mol. Ecol.



3.    Tallaganda, Australia

This project investigates whether population structure and demographic history of a suite of distantly-related low-mobility forest invertebrates closely mirror one another owing to thier shared reliance on a particular type of microhabitat - dead wood. Alternatively, perhaps at least some of these rotting-log-associated (saproxylic) invertebrates have unique evolutionary histories owing to subtle but nonetheless important differences in other life history characteristics (e.g., dispersal ability, desiccation susceptibility). In other words, is phylogeographic structure habitat-specific or species-specific? The project is centered in the cool temperate eucalypt forests at Tallaganda, an isolated, linear section of the Great Dividing Range in south-eastern Australia. Outcomes from this study have raised the possibility of using topography (particularly drainage catchments) as landscape-level biodiversity management units. We are also investigating how and why spatially clustered multi-species phylogeographic breaks form in some parts of the forest, and what drives different gene flow dynamics operating at different genetic contact zones - sometimes within the same species.

Collaborating labs: Paul Sunnucks (Monash Univ.), Dave Rowell (Australian National Univ.)

Selected publications: Garrick et al. (2004) Mol. Ecol., Sunnucks et al. (2006) Mol. Ecol., Garrick et al. (2007) Mol. Ecol., Garrick et al. (2008) Evolution

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