Most hypotheses of biotic change without mass extinction also implicate competition, whether direct or indirect ( 1). This trend has been attributed to environmental changes favoring advanced cladids ( 12). However, it has long been known that camerates experienced high extinction rates in the later Mississippian and were reduced to just a few lineages by the Pennsylvanian ( 19, 20, 25). 2 and SI Appendix, Supporting Methods and Discussion), the decline could not be directly tested owing to the small number of data points. Whereas the overall camerate curve could not be distinguished from a random walk (runs test P = 0.07) because of the Tournaisian-Viséan inflection point ( Fig. However, it should be noted that r value remains strongly positive (>0.5) after detrending, which is consistent with the significant correlation observed in the raw data.Ĭamerates exhibit an abrupt decline beginning at the Tournaisian–Viséan boundary ( 19, 20, 24). The lack of significance in the more conservative first differencing results is not surprising given the small number of data points (three) from the four time intervals (Tournaisian 1–4) available for calculations ( 4).
This confirms results from the global dataset showing major crinoid diversification as a post-Hangenberg and postpredator extinction phenomenon. The greatest gains among camerate crinoids took place during the Tournaisian stage, during which diversity more than doubled from Late Devonian levels ( Fig. 2 and SI Appendix, Table S4) can be attributed to independent radiations after loss of incumbent predators rather than real interaction. Mirrored increases in diversity among Mississippian fish and camerate crinoids during the Tournaisian ( r = 0.96, P = 0.04 FD r = 0.56, P = 0.62) ( Fig. These two areas have the most comprehensive vertebrate and crinoid records during this interval. To investigate these patterns further, we divided Mississippian occurrence data from North American and the British Isles into 11 time bins of approximately equal length ( SI Appendix, Table S2). Both trophic knock-on effects and retention of obsolete traits might be common in the aftermath of predator extinction. Thus, interactions observed in small ecosystems, such as Lotka-Volterra cycles and trophic cascades, could operate at geologic time scales and higher taxonomic ranks. Our results suggest that major crinoid evolutionary phenomena, including rapid diversification, faunal turnover, and species selection, might be linked to vertebrate predation.
Camerate failure is linked to the retention of obsolete defenses or “legacy adaptations” that prevented coevolutionary escalation. In contrast, later Mississippian (359–318 Mya) camerate crinoids declined precipitously in the face of increasing predation pressure from new durophagous fishes. Despite apparently favorable environmental conditions, crinoids diversified only after removal of their vertebrate consumers, exhibiting predatory release on a geological time scale. Here we show that the end-Devonian Hangenberg event (359 Mya) was a natural experiment in which vertebrate predators were both removed and added to an otherwise stable prey fauna, revealing specific and persistent trophic interactions. As a result, the role of predation in macroevolution is often dismissed in favor of competition and abiotic factors. Both characteristics are notoriously difficult to infer in the fossil record, where evidence of predation is usually limited to damage from failed attacks, individual stomach contents, one-sided escalation, or modern analogs. In modern ecosystems, experimental removal or addition of taxa is often used to determine trophic relationships and predator identity.
Predator–prey interactions are thought by many researchers to define both modern ecosystems and past macroevolutionary events.
0 kommentar(er)
