Recovery from the most profound mass extinction of all time

Abstract

The end-Permian mass extinction, 251 million years (Myr) ago, was the most devastating ecological event of all time, and it was exacerbated by two earlier events at the beginning and end of the Guadalupian, 270 and 260 Myr ago. Ecosystems were destroyed worldwide, communities were restructured and organisms were left struggling to recover. Disaster taxa, such as Lystrosaurus, insinuated themselves into almost every corner of the sparsely populated landscape in the earliest Triassic, and a quick taxonomic recovery apparently occurred on a global scale. However, close study of ecosystem evolution shows that true ecological recovery was slower. After the end-Guadalupian event, faunas began rebuilding complex trophic structures and refilling guilds, but were hit again by the end-Permian event. Taxonomic diversity at the alpha (community) level did not recover to pre-extinction levels; it reached only a low plateau after each pulse and continued low into the Late Triassic. Our data showed that though there was an initial rise in cosmopolitanism after the extinction pulses, large drops subsequently occurred and, counter-intuitively, a surprisingly low level of cosmopolitanism was sustained through the Early and Middle Triassic.

Figure 1

Global diversity (dashed line) and mean alpha diversity (solid line) of Permo-Triassic tetrapod families. Extinctions are labelled as 1, Olson's extinction; 2, end-Guadalupian extinction; and 3, end-Permian extinction. Geological stages (Gradstein & Ogg 2004) are as follows: Ar, Artinskian; K, Kungurian; R, Roadian; W, Wordian; Ca, Capitanian; Wu, Wuchiapingian; Ch, Changhsingian; I, Induan; O, Olenekian; An, Anisian; L, Ladinian; Cr, Carnian.

Figure 2

Rate of alpha diversification (the first derivative of diversity through time) of mean number of tetrapod families in communities, calculated stage-by-stage from the Mississippian to the Late Triassic; error bars cannot be applied. Miss, Mississippian; Penn, Pennsylvanian; Cisur, Cisuralian; Guad, Guadalupian; Lopin, Lopingian; E. Tri, Early Triassic; M. Tri, Middle Triassic; L. Tri, Late Triassic.

Figure 3

Ecological diversity of Permo-Triassic tetrapod communities. (a) Size (light green, large; light yellow, medium; sky blue, small) and (b) diet (pink, browsers; light green, predators; light yellow, insectivores; sky blue, piscivores) are expressed as a percentage of the total community. (c) The guilds are defined by body size and inferred diet. Error bars cannot be applied as the number of occupied guilds is not a mean number, rather a cumulative count of the guilds filled in each stage. Size of the animals is defined as small (with snout-vent length (SVL) less than 150 mm), medium (SVL from 150 mm to 1.5 m) and large (SVL greater than 1.5 m). Geological stages are the same as given in figure legend 1.

Figure 4

Cosmopolitanism of tetrapods through the Carboniferous, Permian and Triassic. Cosmopolitanism (C) is measured as mean alpha diversity $(\overline{T})$ divided by global diversity (T_t), according to the formula $C=\overline{T}/T_{\text{t}}$. Note the overall decline of cosmopolitanism through this time interval, perhaps related to increasing taxonomic and ecological diversity of tetrapods, but also note the coupled rises and falls in cosmopolitanism following major extinction events, especially (1) Olson's extinction, (2) the end-Guadalupian extinction and (3) the end-Permian extinction. Abbreviations are the same as given in figure legend 2.