The Restructuring of Ecological Networks by the Pleistocene Extinction

Abstract

Most terrestrial large mammals went extinct on different continents at the end of the Pleistocene, between 50,000 and 10,000 years ago. Besides the loss in species diversity and the truncation of body mass distributions, those extinctions were even more impactful to interaction diversity. Along with each extinction, dozens of ecological interactions were lost, reorganizing species interaction networks, which attained species-poor configurations with low functional redundancy. Extinctions of most large herbivores impacted energy flow and the rates of nutrient cycling, reconfiguring ecosystem-level networks. Because large mammals have high mobility, their loss also shortened seed-dispersal distance and reduced nutrient diffusivity, disrupting spatial networks. This review examines the recent advances in understanding how different types of ecological networks have been restructured by megafaunal extinctions and how this reorganization affected ecosystem functions. ▪ Megafaunal extinctions resulted in the loss of multiple ecological interactions in terrestrial systems. ▪ Interaction loss reshaped different types of ecological networks including food webs and spatial networks. ▪ The reorganization of ecological networks changed how terrestrial ecosystems are structured and function. Expected final online publication date for the Annual Review of Earth and Planetary Sciences, Volume 52 is May 2024. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

The reorganization of predator–prey networks over 20 million years explains extinction patterns of mammalian carnivores

“…Taken together, these findings suggest that trophic structure, functional structure (as in Blanco et al, 2021) and species richness capture complementary aspects of the functional retailoring of communities over time. A simplification interaction networks has been described for abrupt biotic transition between terminal Pleistocene and early Holocene (Fricke et al, 2022;Pires, 2024;Pires et al, 2015), but in such cases, network restructuring was associated with human or climatedriven extinctions of the Pleistocene megafauna. Our results suggest that in the Iberian Peninsula, structural changes may have started far earlier and were not necessarily associated with overall reductions in species richness, but with a restructuring of the interactions due to changes in the faunal composition of the herbivore guild.…”

“…In one of the few studies analysing a relatively long timeseries of reconstructed interaction networks spanning more than 800 thousand years, Nénzen et al (2014) showed that despite a high species turnover, the structure of interaction networks among terrestrial mammals in Europe changed little throughout the Pleistocene. Megafaunal extinctions at the terminal Pleistocene, however, resulted in secondary extinctions that simplified interaction networks, resulting in ecological systems that became progressively more vulnerable to species loss (Fricke et al, 2022;Nenzén et al, 2014;Pires, 2024;Pires et al, 2015). Other studies have used palaeoecological inferences to reconstruct interaction networks in Palaeozoic and Mesozoic communities showing, for instance, that food webs underwent marked structural changes during episodes of mass extinction (Angielczyk et al, 2005;Mitchell et al, 2012;Roopnarine et al, 2007Roopnarine et al, , 2019Roopnarine & Angielczyk, 2015).…”