Molecular genetics have also been valuable for recognizing multispecies complexes within a single species of many invertebrates, and this new knowledge of biodiversity is having repercussions in both the basic and applied sciences. For example, the sentinel species for decades in pollution monitoring programs---the blue mussel, Mytilus edulis---is now known to be three distinct species with overlapping distributions [ McDonald et al., 1992]. Moreover, samples of two of these species collected from the same habitat contained significantly different concentrations of various elements, including heavy metals, evidently due to the different growth rates of the species [ Lobel et al., 1990]. The magnitude of these kinds of species-specific differences is now being considered in comparative studies such as the ``International Mussel Watch'' program for monitoring contaminant input to marine waters [ NAS, 1980].
Another example of how new knowledge of biodiversity affects understanding of ecological processes is the recently discovered multispecies complex in the Caribbean star coral, Montastraea annularis [ Knowlton et al., 1992]. Using electrophoretic techniques, three morphotypes of what had previously been called M. annularis were determined to be three distinct species. Furthermore, the three species were shown to have different growth rates and different oxygen isotope ratios, parameters routinely used to estimate past climatic conditions in coral-reef habitats. Thus, in this case, new knowledge of marine biodiversity may result in revised estimates of rates of global warming!