Background and Mass Extinctions: The Alternation of Macroevolutionary Regimes

Abstract

Comparison of evolutionary patterns among Late Cretaceous marine bivalves and gastropods during times of normal, background levels of extinction and during the end-Cretaceous mass extinction indicates that mass extinctions are neither an intensification of background patterns nor an entirely random culling of the biota. During background times, traits such as planktotrophic larval development, broad geographic range of constituent species, and high species richness enhanced survivorship of species and genera. In contrast, during the, end-Cretaceous and other mass extinctions these factors were ineffectual, but broad geographic deployment of an entire lineage, regardless of the ranges of its constituent species, enhanced survivorship. Large-scale evolutionary patterns are evidently shaped by the alternation of these two macroevolutionary regimes, with rare but important mass extinctions driving shifts in the composition of the biota that have little relation to success during the background regime. Lineages or adaptations can be lost during mass extinctions for reasons unrelated to their survival values for organisms or species during background times, and long-term success would require the chance occurrence within a single lineage of sets of traits conducive to survivorship under both regimes.

General environmental heterogeneity as the explanation of sexuality? Comparative study shows that ancient asexual taxa are associated with both biotically and abiotically homogeneous environments

“…It is true that, somehow paradoxically, paleontological studies (Jablonski, 1986) show increased extinction rates of species without planktonic larvae. However, the main reason for this is probably better colonizing abilities that are usually, but not always, associated with indirect development (Ó Foighil, 1989).…”

Biostratigraphy and Inoceramus survival across the Cenomanian–Turonian (Cretaceous) boundary in the Ram River section, Alberta, Canada

“…Inoceramus appears to be absent from the Early Turonian for a span of about 0.7 Myr (based on ages in Ogg and Hinnov 2012;see also Harries 1993). In its Early Turonian history, Inoceramus therefore behaves as a classic Lazarus taxon (Jablonski 1986;Harries 1996;Wignall and Benton 1999), although what happened to the genus during its apparent hiatal time remains unclear (see discussion in Harries 1993;Kauffman and Harries 1996): Did it survive in a refugium; is the absence due to the poor quality of the fossil record; did it thrive in such small populations that the chance of finding them in the fossil record is extremely low? Other questions appear when this problem is considered at the species level: Did only one, or numerous Inoceramus lineages survive; when did the speciation (or pseudospeciation) take place; do the events observed in the North American Western Interior extend beyond that region?…”

Espaço e diversificação: uma perspectiva teórica

“…The long transients observed for systems close to criticality might sustain the age-diversity association for a relatively long period. Sudden crashes in diversification rates that are observed in the periods following mass extinctions, which some posit are responsible for the "dead clade walking" effect (Jablonski 2002), might be caused by transformations in the spatial structure of the organisms, which might be enough to transverse the critical point.…”

“…The genetic isolation of species is thought to protect genetic and functional diversity as well as promote vaster ranges (Garcia-Ramos and Kirkpatrick 1997), which may in turn serve as a buffer against extinctions caused by shifts in environmental conditions (Jablonski and Raup 1995). The mechanisms by which the prolificacy of many clades plummeted throughout Earth's history, leading to their demise, is still poorly understood (Jablonski 2001). This work suggests that an important factor for these steep transitions in speciation rates might have been the transformation in the spatiotemporal organism distribution patterns.…”

“…The evolutionary persistence of a clade is frequently linked to how prolific it is, that is, the rate at which new species arise within it (Jablonski 1986). The genetic isolation of species is thought to protect genetic and functional diversity as well as promote vaster ranges (Garcia-Ramos and Kirkpatrick 1997), which may in turn serve as a buffer against extinctions caused by shifts in environmental conditions (Jablonski and Raup 1995).…”