Combining morphometric and paleoecological analyses: Examining small-scale dynamics in species-level and community-level evolution

By combining two powerful types of quantitative techniques - landmark morphometric and paleocommunity analyses - we can examine the role of ecology in evolutionary processes by determining whether major morphological changes co- occur with significant changes in paleocommunity structure. Whereas morphological changes using landmark morphometric analysis indicate evolutionary changes within a lineage, changes in paleocommunity metrics such as abundance and dominance can be used to indicate ecological changes and identify species of special interest. This preliminary study documents both major ecological and morphological changes within the scallop " Pecten" thompsoni from two closely spaced stratigraphic horizons of the Neogene marine sequence of the Dominican Republic. Ecologically, the abundance and dominance of this species differs dramatically between the two samples. Morphometrically, while size does not change significantly, the two populations exhibit statistically different shapes. In addition, there appears to be a shift in ontogenetic patterns where initially an allometric pattern exists but then changes to an isometric growth relationship. These different morphological patterns are consistent with changes in paleoenvironmental conditions. We suggest that a coupled approach of morphometric and paleocommunity analyses may focus future studies on intervals and taxa where evolutionary change may be directly correlated to concomitant ecological changes.