Environmental changes define ecological limits to species richness and reveal the mode of macroevolutionary competition.
Co-dependent geological and climatic changes obscure how species interact in deep time. The interplay between these environmental factors makes it hard to discern whether ecological competition exerts an upper limit on species richness. Here, using the exceptional fossil record of Cenozoic Era macroperforate planktonic foraminifera, we assess the evidence for alternative modes of macroevolutionary competition. Our models support an environmentally dependent macroevolutionary form of contest competition that yields finite upper bounds on species richness. Models of biotic competition assuming unchanging environmental conditions were overwhelmingly rejected. In the best-supported model, temperature affects the per-lineage diversification rate, while both temperature and an environmental driver of sediment accumulation defines the upper limit. The support for contest competition implies that incumbency constrains species richness by restricting niche availability, and that the number of macroevolutionary niches varies as a function of environmental changes.
Ocean and Earth Sciences, National Oceanography Centre Southampton, University of Southampton Waterfront Campus, Southampton, SO14 3ZH, UK.|Centre for Biological Sciences, University of Southampton, Life Sciences Building 85, Highfield Campus, Southampton, SO17 1BJ, UK.
Thomas H G
TH
Ezard
Department of Life Sciences, Natural History Museum, Cromwell Road, London, SW7 5BD, UK.|Department of Life Sciences, Silwood Park Campus, Imperial College London, Ascot, Berkshire, SL5 7PY, UK.
Andy
A
Purvis
D000818:Animals; D044822:Biodiversity; D005075:Biological Evolution; D002980:Climate; D017753:Ecosystem; D056908:Foraminifera / Q000145:classification* / Q000235:genetics*; D005580:Fossils; D008954:Models, Biological; D010802:Phylogeny
Beverton-Holt; Ricker; contest competition; diversification; diversity-dependence; ecological limits; microfossil; scramble competition