Latitudinal gradient of taxonomic richness: combined outcome of temperature and geographic mid-domains effects?

• Main Authors: Brayard, Arnaud, Escarguel, Gilles, Bucher, Hugo
• Other Authors: PaleoEnvironnements et PaleobioSphere (PEPS), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Paläontologisches Institut und Museum, Universität Zürich Zürich = University of Zurich (UZH)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2005
• Subjects: Latitudinal gradient of taxonomic richness; probabilistic model; sea surface temperature; currents; mid-domain effect; Planktonic Foraminifera; Atlantic Ocean; [SDU.STU.PG]Sciences of the Universe [physics]/Earth Sciences/Paleontology; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; Planktonic foraminifera
• Online Access: https://hal.science/hal-00180263; https://doi.org/10.1111/j.1439-0469.2005.00311.178–188

International audience For several decades, the origin and ecological consequences of large-scale continental and marine Latitudinal Gradients of Taxonomic Richness (LGTR) have been intensively debated. Among the various hypotheses, it has been proposed that a LGTR is the by-product of a geographic middomain effect, i.e. the result of a random distribution of ranges of taxa between physical hard boundaries such as the continent/ocean interface. In order to more realistically evaluate the role of the mid-domain effect on the origin and evolution of the LGTR of marine planktonic organisms, we present a 2D model based on a cellular-automaton approach in which sea surface temperatures (SST) and currents are forced in the biogeographic dispersal of a randomly generated clade (a 2D ‘geophyletic' model). Sensitivity experiments allow to evaluate the effects of currents, SST and the geographical origin of a clade on the formation and shape of a LGTR for planktonic organisms when coupled with a geographic mid-domain effect. Results are discussed in the light of the empirical LGTR of extant planktonic Foraminifera in the Atlantic Ocean. Independently of any other biotic or abiotic parameter, inclusive of the surface currents and origination/extinction absolute and relative rates, our simulations show that the coupling of the mid-domain effect with two critical parameters, namely the shape and intensity of the SST gradient and the geographic origin of a clade, produces realistic patterns of diversity when compared with the observed LGTR of extant atlantic planktonic foraminifera. The results illustrate a non-linear relation between a unimodal latitudinal SST gradient and a resulting bimodal LGTR characterized by a drop in species richness near the equator. This relation indicates that the SST gradient exerts a mid-domain effect on the LGTR. The latitudinal positions of the modal values of the LGTR are also found to be influenced by the geographic origin of the simulated clade.