Evolutionary replacement of ecological equivalents in Late Devonian benthic marine communities

Temporal changes in taxonomic diversity, dominance structure, trophic structure, niche structure, and community composition are examined in equivalent nearshore and offshore Late Devonian benthic marine communities of New York and the central Applachians. The study interval spans an approximately 5-m.y. record of Frasnian tropical marine environments. Community structures remain relatively constant during the five million year interval, though offshore communities appear to be more unstable than nearshore communities. Considerable change in community composition occurs, however, with the total replacement of dominant spiriferacean brachiopods in the early Frasnian by their ecological equivalents in the late Frasnian. Ecological replacement of dominant species affected both offshore and nearshore communities, and does not appear to be a function of spatial environmental gradients.