Relative taxonomic and ecologic stability in Devonian marine faunas of New York State: a test of coordinated stasis

Abstract

The concept of coordinated stasis, manifest as a pattern of long intervals of concurrent taxonomic and ecologic persistence separated by comparatively abrupt periods of biotic change, has been challenged in recent studies that claim a lack of prolonged persistence of taxa and associations. A key problem has been the difficulty of distinguishing faunal change owing to localized, short-term environmental fluctuation or patchiness from that indicating regionally pervasive, long-term evolutionary or ecological change. Here, we use an extensive database from the Middle Devonian Hamilton Group of the Appalachian Basin to test for taxonomic and ecologic persistence within this ecological-evolutionary subunit, a succession of purported relative stability. Replicate samples collected from many localities and stratigraphic horizons over a wide geographic area allow us to address the effects of small-scale environmental variation and localized faunal patchiness while exploring basin-scale variation in faunal composition within and between the formations of the Hamilton Group.Observed stratigraphic distributions of fossils are consistent with a scenario in which all taxa are present from bottom to top of the Hamilton Group, and absences result only from sampling failure. Although small-scale variation in faunal composition indeed does occur, there is no more variation among formations than occurs within them. Assemblages from different formations, whether they are defined by taxonomic or ecologic composition, are statistically indistinguishable according to several independent metrics, including ANOSIM and a maximum likelihood estimation that evaluates stratigraphic turnover using Bayesian “Information Criterion.” Simulated data sets indicate that test results are most consistent with species-level extinction of 2.6% per Myr within the Hamilton Group, far lower than the Givetian rate of 11.5% per Myr generic extinction derived from a global database. Such faunal persistence over the ~5.5 Myr encompassed by this unit is consistent with the pattern of coordinated stasis. Earlier studies showing greater amounts of temporal turnover in Hamilton Group faunas are likely influenced by their smaller geographic scale of analysis, suggesting that regional studies done elsewhere may yield similar results.

The Okmulgee, Oklahoma fossil flora, a Mazon Creek equivalent: Spatial conservatism in the composition of Middle Pennsylvanian wetland vegetation over 1100km

“…This kind of compositional persistence, or recurrence also has been documented in terrestrial wetland vegetation from Carboniferous lowland environments (e.g., DiMichele et al, 2002), and for normal marine benthic faunas from Mississippian environments (e.g., Bonelli and Patzkowski, 2011). These kinds of patterns in both terrestrial and marine environments have been attributed to relatively narrow ranges of physical environmental tolerance by most organisms, resulting in strong patterns of habitat tracking through space and time (e.g., Brett et al, 2007;DiMichele et al, 2008), and, as observed by Ivany et al (2009), may account for observed larger spatio-temporal scale, evolutionary-ecological patterns.…”

Phase shifts and stable states on coral reefs

“…Of course, time to recovery is not related to difficulty of transition, so the time course of a transition has no bearing on hysteresis or alternative community states. The biotic stability of coral reefs on centennial, millennial, and longer time scales is most parsimoniously viewed as an indication of the stability of environmental drivers (Aronson et al 2002a(Aronson et al , 2002b(Aronson et al , 2005, in the absence of evidence to the contrary (Ivany et al 2009). …”

Early establishment of vertebrate trophic interactions: Food web structure in Middle to Late Devonian fish assemblages with exceptional fossilization

“…Thus, these three species likely played a major role in the structure of the food web and interspecies relationships. Because of the large timespan of the Escuminac Formation, a coordinate and evolutionary stasis (Brett et al 1996, Ivany et al 2009 has been suggested for the Escuminac assemblage (Cloutier et al 2011). A long duration stasis is only possible if links between species are strong and explained by ecological stability and complexity as suggested by biostratigraphic distribution of taxa and the trophic structure of the Escuminac assemblage.…”