New Harvard Forest Publications: Methods and Models of Species Change and Spread

New methods in detecting species change

Data on insect population sizes collected at the Kellogg Biological Station (KBS) LTER were used in a new paper by a group including HF senior ecologist Aaron Ellison focused on new methods to detect changes in species assemblages through time. The methods, including hierarchical models and bootstrapping, provide ways to detect temporal trends in the relatively short time-series of data that are characteristic of many LTER datasets.

Citation: Gotelli, N. J., R. M. Dorazio, A. M. Ellison, and G. D. Grossman. 2010. Detecting temporal trends in species assemblages with bootstrapping procedures and hierarchical models. Philosophical Transactions of the Royal Society of London, Series B 365: 3621-3631.

Model analyzes spread of species due to climate change over time

A key challenge for ecologists, biogeographers, and evolutionary biologists is to detect and identify ecological boundaries, and to understand how these boundaries and range edges are likely to change as the climate changes. This problem is especially important for studying and managing invasive species that are rapidly spreading and expanding their ranges. A new paper by a group led by recent HF post-doc Matt Fitzpatrick develops a Bayesian hierarchical model to (1) analyze the spatial and temporal spread of a species, (2) account for spatial structure in the data and the uncertainty associated with the apparent spatial structure; and (3) objectively assign probabilities to the apparent geographic boundary of a species. These models are applied to the historical record of the spread of the invasive hemlock woolly adelgid, but are generally applicable to any species, native or exotic, whose range is changing through time.

Fitzpatrick, M. C., E. L. Pressier, A. Porter, J. Elkinton, L. A. Waller, B. P. Carlin, and A. M. Ellison. 2010. Ecological boundary detection using Bayesian areal wombling. Ecology 91: 3448-3455.