title: Bimodality of Latitudinal Gradients in Marine Species Richness.
abstract: The paradigm for the latitudinal gradient in species richness is that it is unimodal with a tropical peak. For 27 published studies, and global datasets of 65 000 recent and 50 000 fossil marine species, we found that almost all datasets were significantly bimodal with a dip in species richness near the equator. The locations of mid-latitude peaks varied between taxa and were higher in the northern hemisphere where the continental shelf is greatest. Our findings support hypotheses of tropical species evolving in response to temperature variation near the edges of the tropics and available high-productivity habitat. They suggest that the equator may already be too hot for some species and that the modes may move further apart due to climate warming.
authors.affiliation: Institute of Marine Science, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.
authors.forename: Chhaya
authors.initials: C
authors.lastname: Chaudhary
authors.affiliation: Institute of Marine Science, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.
authors.forename: Hanieh
authors.initials: H
authors.lastname: Saeedi
authors.affiliation: Institute of Marine Science, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand. Electronic address: m.costello@auckland.ac.nz.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Costello
mesh_terms: D044822:Biodiversity; D002980:Climate; D017753:Ecosystem; D005580:Fossils
keywords: biodiversity; biogeography; climate change.; habitat; latitude; temperature