Detrended correspondence analysis: A useful tool to quantify ecological changes from fossil data sets

Resumen

Fossil assemblages
reflect the parental communities that produced them, and are in turn
associated with specific environmental conditions. Thus, climatic
and environmental changes are associated with changes in both the
biotic communities and the fossil assemblages they produce. As a
consequence, the environmental reconstruction of the past relies on
the interpretation of multivariate fossil sequences that are
commonly analyzed through dimensional rescaling techniques.
Detrended correspondence analysis (DCA) has proven as an excellent
technique to summarize ecological changes through time with the
advantage of few prior assumptions and results that can be directly
interpreted in terms of ecological turnover. In this paper we
elaborate on a brief description of the technique and the
interpretation of results, using a worked example on pollen and
diatom data sets from Lago Verde (Los Tuxtlas, Mexico). With this
worked example, we highlight the three basic ways in which DCA can
provide useful approaches for a clear and relatively easy
interpretation of the fossil data: i) identification of the
ecological space through the a priori interpretation of species
ordination; ii) localization of time slices within the ecological
space defined by species, and quantification of the ecological
turnover among samples; and iii) calculation of ecological distances
as a means for putting individual samples into the historical
context provided by the time frame in question.