Species Invasions

Our work integrates studies of local-scale invasion events with global invasion patterns.  Our aim is to better understand and predict impacts of invasions on local, regional and global biodiversity. We are also interested in understanding the mechanisms of invasion, i.e., the processes that allow non-native species to out-perform natives.  Current work in the lab aims to understand the evolutionary consequence of differences in the region of origin of non-native species with respect to their eventual success and impact. Finally, we are interested in gleaning information about ecological, evolutionary and biogeographical processes from the many unplanned ‘experiments’ that invasions provide.


Exotic Eucalyptus globulus stands in Spain, where this species forms dense monospecific stands that exclude most native species.

Extinction Dynamics

Species extinctions can occur quickly in punctuated events, but more often extinction is a slow process characterized by pronounced time lags following episodes of environmental change. Our aim is to better understand these time lags, and in particular to evaluate the predictability and dynamics of species extinctions. We are currently collaborating with a paleoecologist, Steve Jackson, to apply traditional paleoecology techniques in an unconventional manner (to study just the most recent paleontogical past); our aim so as to create long-term ecological data sets that record disturbance events and subsquent extinctions over the last several hundred years.


Field site at the Miller Woods section of the Indiana Dunes National Lakeshore, where we are studying the extinction dynamics of aquatic species over the past 300 years.

Managed Relocation

Managed Relocation (aka Assisted Colonization and Assisted Migration) is a new, controversial strategy that aims to save species from global warming by purposefully transporting them to areas where they have not previously occurred, but where they are expected to survive as climate changes.  We are co-leading a working group effort that aims to provide a synthetic evaluation of this strategy, one that considers the ecological, evolutionary, ethical, legal and economic dimensions of managed relocation. For more information on this working group, and the many academic, NGO and U.S. government partners involved in this effort see our web page on Managed Relocation. We are also assessing the feasibility of relocating endangered species, in collaboration with the U.S. Fish & Wildlife Service and the U.S. Geological Survey.


A tortoise on the edge of a protected area - in Athens, Greece.  Individuals like this will be unable to disperse through urban areas, which will function as geographical barriers for species dispersal as climate changes.

Species Responses to Climate Change

Some species will shift their geographic distributions by great distances in response to climate change, while others will largely stay put. Similarly some species will experience pronounced genetic changes or changes in phenology (i.e., the timing of key life-history events), while others will remain largely unchanged. At present, ecologists, evolutionary biologists and conservation biologists lack a thorough understanding of which species will be most sensitive to changes in climate. To advance our knowledge in this area, we are attempting to better characterize species responses to climate change. Active projects include work to predict the impacts of climate change on shifts in species geographic distributions, changes in phenology, and changes in body size.


Amphibians, like this salamander in California, are being evaluated for their potential to shift their geographic distribution and occupy newly available habitat as climate changes over the next century.


Sax Research Lab, Brown University, Box G-W Providence, Rhode Island 02912; (401) 863-9676;