Using GIS to unlock the interactions between biogeography, environment, and evolution in Middle and Late Devonian brachiopods and bivalves

The Late Devonian was a time of profound evolutionary and environmental change associated with the Frasnian-Famennian biodiversity crisis. One way to unravel the faunal dynamics of this complex crisis is to document the spatial and temporal patterns associated with biodiversity decline. This analysis investigates the relationship between biogeography, relative sea level, and environmental changes in Laurentian brachiopod and bivalve species during the Givetian through Famennian Stages (upper Middle to terminal Devonian). Representatives from all major brachiopod and bivalve clades and paleocommunities were examined to provide a cross-faunal comparison. Species' ranges were reconstructed both spatially and temporally (at the level of conodont zones) using GIS to understand the timing and extent of species invasions and the importance of geographic range during the crisis interval. Species' geographic ranges were linked closely with both relative sea-level change and depositional environment and expanded as relative sea-level rose. In addition, times of interbasinal species invasions corresponded closely with sea-level rises that breached tectonic barriers. Species with larger geographic ranges were more resistant to extinction during the Late Devonian. This relationship is reflected partly in a general trend towards increased extinction resistance in taxa that are found farther offshore in environments that potentially included more area. For example, there is an increased survival advantage for species that inhabited the middle and outer platform environments, though not for species inhabiting the open shelf. Additionally, species whose Givetian to Frasnian history includes at least one interbasinal invasion event were more likely to survive the Late Devonian biodiversity crisis than noninvasive species; this may have relevance for our understanding of the current biodiversity crisis, given the role that invasive species are playing in mediating modern extinctions. (C) 2004 Elsevier B.V. All rights reserved.