Extinction Debt and Ecosystem Change: ~ Bioblogia.net

1 de febrero de 2010

Extinction Debt and Ecosystem Change:

We seek a post-doctoral research associate, for a three-year position, in the Department of Ecology and Evolutionary Biology, *Brown** University* for participation in a collaborative project between Dov Sax (Brown University) and Steve Jackson (University of Wyoming). This project will investigate the dynamics of species extinction at local scales, paying particular attention to lag times in species extinction, extinction debt and predictability of extinction across taxa. The project will be conducted in wetland ecosystems of the Indiana Dunes. The primary method of investigation will be analysis of plant macrofossils and pollen in sediment cores, but the project will also include a resurvey of extant vegetation, and a taphonomic examination of plant macrofossil and pollen deposition. The project has key defined goals, but there is substantial room for independent and collaborative exploration of related topics in community ecology, paleoecology, and conservation biology. Candidates should have a Ph.D. with research experience in either ecology or paleoecology; botanical experience is desirable but not mandatory. The project will require extensive field work in the summer and some travel to the University of Wyoming. Starting salary will be $40,000 with full benefits. Please send a CV, a brief statement of research interests, and the names and contact information for three references to Dov Sax, dov.sax@gmail.com. Review of applicants will begin on March 1 and will continue until the post is filled. We would like the postdoc to begin the position on or before May 15, 2010.

*PDF of paper in press on Extinction Debt by Jackson and Sax:*


*Project summary of the grant proposal that is funding the postdoctoral position:*

The time-course and dynamics of species extinctions at local spatial scales are poorly understood relative to the intrinsic interest of this topic. The reason for this disparity is simple – there are relatively few data sets available that reveal patterns of species extinction at local spatial scales over time-courses of decades to centuries. “Long-term” ecological data typically span periods of 20-40 years. While such data sets are invaluable, extinction dynamics may require longer runs of time to play out. Here we propose to remedy this shortcoming by adapting paleoecological techniques to address contemporary extinction dynamics in pond communities. We will conduct a detailed study of extinction dynamics following major human-induced disturbances of the mid-late 19^th Century by examining plant macrofossils and pollen in well-dated sediment cores. Plant macrofossils (seeds, fruits, and vegetative material) are produced by most aquatic and wetland species, do not travel far from source plants, and can be identified to species. Thus, they can provide detailed records of changes in local populations, including invasion and extinction.

Our study will concentrate on the Indiana Dunes National Lakeshore, where numerous well-studied ponds are available. Previous plant-macrofossil work conducted at this site has shown good preservation of plant fossils over the past several thousand years. This work also shows that many abundant species underwent local extinction following onset of human disturbance approximately 150 years ago. By collecting more than 100 sediment cores across a landscape of ponds, we will be able to study the fine-scale dynamics of species extinctions over the past 300 years. Because of the high sedimentation rates at the study sites, we will be able to resolve changes in relative abundance and composition of these species in approximately 15-year increments from 300-150 years ago and in 5-year increments from 150 years ago to the present (when sedimentation rates were higher). We will complement the macrofossil findings with more ‘traditional’ long-term data, by conducting a 28-year resurvey of the vegetation in these ponds. We will also advance the study of taphonomy by relating extant vegetation to the deposition of plant pollen, seeds and fruits.

Dov F. Sax
Assistant Professor
Ecology and Evolutionary Biology
80 Waterman Street, Box G-W
Brown University
Providence, RI 02912-0001
phone: 401-863-9676
fax: 401-863-2166

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