DETECTING TRENDS IN SPECIES COMPOSITION

Citation
Te. Philippi et al., DETECTING TRENDS IN SPECIES COMPOSITION, Ecological applications, 8(2), 1998, pp. 300-308
Citations number
48
Categorie Soggetti
Ecology
Journal title
ISSN journal
10510761
Volume
8
Issue
2
Year of publication
1998
Pages
300 - 308
Database
ISI
SICI code
1051-0761(1998)8:2<300:DTISC>2.0.ZU;2-Y
Abstract
Species composition reflects a combination of environmental and histor ical events at a site; hence, changes in species composition can provi de a sensitive measure of ecologically relevant changes in the environ ment. Here, we consider the analysis of species composition when multi ple sites are followed through time. Analyses of temporal trends in sp ecies composition either summarize species composition into a few metr ics (indices or axis scores) or analyze the similarity among sites. We develop and illustrate the similarity approach. Each pair of samples represents a pair of replicates, a pair from the same site at differen t times, a pair from different sites at the same time, or an unrelated pair. Differences among times can be estimated by comparing average t emporal dissimilarity to average replicate dissimilarity. Temporal tre nds can be described by one of three statistics that measure progressi ve change, the correlation of temporal dissimilarity with the length o f time between samples. These methods are illustrated using data on ch anges in a South Carolina zooplankton assemblage following disturbance , and changes in bird species composition on Skokholm Island, Wales. I t is difficult to define and interpret temporal trends. Some definitio ns of interesting trends, like increasing divergence from another set of sample plots, place additional requirements on the sampling design. Including replicate samples or clustering sample plots and including ''control'' plots for comparison with sentinel sites would contribute to an understanding of changes in species composition.