INTRODUCTION

The fossil record clearly documents both changes in taxonomic lineages and community composition. However, it is unclear how closely related the processes and patterns of species evolution and community changes may be. The evidence to suggest that the role of biotic interactions shape the evolutionary paths of lineages remains controversial (e.g., Valentine 1973; Kitchell 1985; Gould 2001; Vermeij 2004).

Among neontologists, however, local ecological interactions between species have been cited as a major influence on speciation and evolution. The geographic mosaic theory of co-evolution has provided a new way of considering the role of local ecology and biotic interactions in allopatric speciation processes and evolutionary patterns. For example, in examining the interactions between a species of moth and a plant in western US states, Thompson (1997, 1999) documented that there existed mutualistic, commensalistic, or even antagonistic relationships between the two species depending on the presence or absence of other insect species. These differences in biotic interactions can be correlated with different genetic populations (Thompson 1999) and thus, can drive speciation through time (Forde et al. 2004). Another implication of these observations and interpretations is that within small geographic areas, "[I]nteractions may show selection mosaics, such that different traits and outcomes are favored by natural selection in different communities" (Thompson 1999).

In a paleontological context, the geographic mosaic theory of co-evolution suggests that paleocommunity composition and biotic interactions may vary geographically and temporally even at small scales, and that these differences may result in evolutionary changes. This theoretical framework may, therefore, bridge the fields of evolutionary biology and paleoecology as well as neoecology and population genetics. In this paper, we explore the potential of using quantitative morphometric and paleocommunity composition data to examine whether correlations exist between community-level and species-level patterns. Quantitative morphometrics allows for the evaluation of species-level microevolutionary changes whereas the analysis of paleocommunity composition provides a first-level proxy for evaluating biotic interactions and ecological fluctuations. If evolutionary changes within lineages as evidenced by morphological change are concurrent with major changes in community structure, it would allow us to seriously reconsider the role of biotic interactions in determining patterns of species evolution in the fossil record.

In order to investigate the relationship between ecological and evolutionary processes, one must have appropriate depositional systems and fossil samples which will allow for robust quantitative analyses. One such depositional system is in the Neogene marine sequences of the Cibao Valley of the northern Dominican Republic. This system has become a major focal point of many important paleobiological studies for many good reasons. The fossils have been studied since the mid 1800s with much modern study based on collections made by E. and H. Vokes and the Naturhistorisches Museum of Basel, Switzerland, since the 1970s (see Jung 1986 for review of molluscan studies and NMITA web site). The marine sequences exposed in river gorges in the north central highlands are very fossiliferous and are believed to represent fairly continuous deposition in a gradually deepening basin (Saunders et al. 1986).

Many paleontologists around the world have been involved in examining the Dominican Republic Neogene fauna. Experts in taxonomic groups have systematically surveyed the samples collected by the Naturhistorisches Museum of Basel (many monographs have been published in Bulletins of American Paleontology). Given the long history of taxonomic study, the alpha taxonomy and basic identification of fossils found in these rocks is comparatively good even if higher level taxonomic reorganizations have not yet been completed for most of the groups. In addition, paleobiologists have long used this system to examine patterns of evolution, including documenting rates of change and investigating the role of heterochrony in speciation processes (e.g., Anderson 1994; Cheetham et al. 1994; Nehm and Geary 1994).