title: Rare species contribute disproportionately to the functional structure of species assemblages.
abstract: There is broad consensus that the diversity of functional traits within species assemblages drives several ecological processes. It is also widely recognized that rare species are the first to become extinct following human-induced disturbances. Surprisingly, however, the functional importance of rare species is still poorly understood, particularly in tropical species-rich assemblages where the majority of species are rare, and the rate of species extinction can be high. Here, we investigated the consequences of local and regional extinctions on the functional structure of species assemblages. We used three extensive datasets (stream fish from the Brazilian Amazon, rainforest trees from French Guiana, and birds from the Australian Wet Tropics) and built an integrative measure of species rarity versus commonness, combining local abundance, geographical range, and habitat breadth. Using different scenarios of species loss, we found a disproportionate impact of rare species extinction for the three groups, with significant reductions in levels of functional richness, specialization, and originality of assemblages, which may severely undermine the integrity of ecological processes. The whole breadth of functional abilities within species assemblages, which is disproportionately supported by rare species, is certainly critical in maintaining ecosystems particularly under the ongoing rapid environmental transitions.
authors.affiliation: PPG Biologia de Água Doce e Pesca Interior, Instituto Nacional de Pesquisas da Amazônia, Manaus, Brazil Coordenação de Biodiversidade, Instituto Nacional de Pesquisas da Amazônia, Manaus, Brazil Laboratoire Biodiversité Marine et ses Usages, MARBEC, Université de Montpellier, Montpellier, France ecorafa@gmail.com.
authors.forename: Rafael P
authors.identifier: 0000-0001-7990-0068
authors.initials: RP
authors.lastname: Leitão
authors.affiliation: Coordenação de Biodiversidade, Instituto Nacional de Pesquisas da Amazônia, Manaus, Brazil.
authors.forename: Jansen
authors.initials: J
authors.lastname: Zuanon
authors.affiliation: Laboratoire Biodiversité Marine et ses Usages, MARBEC, Université de Montpellier, Montpellier, France.
authors.forename: Sébastien
authors.identifier: 0000-0002-2362-7178
authors.initials: S
authors.lastname: Villéger
authors.affiliation: Centre for Tropical Biodiversity and Climate Change, James Cook University, Townsville, Australia.
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Williams
authors.affiliation: INRA, UMR Ecologie des Forêts de Guyane, INRA, Kourou, French Guiana International Center for Tropical Botany, Department of Biol Sci, FIU, Miami, USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Baraloto
authors.affiliation: Department of Biology, University of Maryland, College Park, MD, USA.
authors.forename: Claire
authors.identifier: 0000-0002-8367-1605
authors.initials: C
authors.lastname: Fortunel
authors.affiliation: Instituto Federal de Educação, Ciência e Tecnologia, Presidente Figueiredo, Brazil.
authors.forename: Fernando P
authors.initials: FP
authors.lastname: Mendonça
authors.affiliation: Laboratoire Biodiversité Marine et ses Usages, MARBEC, Université de Montpellier, Montpellier, France Australian Research Council Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Australia.
authors.forename: David
authors.identifier: 0000-0002-0200-9514
authors.initials: D
authors.lastname: Mouillot
mesh_terms: D000818:Animals; D044822:Biodiversity; D001717:Birds / Q000502:physiology*; D001938:Brazil; D003247:Conservation of Natural Resources; D053476:Extinction, Biological; D005399:Fishes / Q000502:physiology*; D005616:French Guiana; D011156:Population Density; D011793:Queensland; D065947:Rainforest; D014197:Trees / Q000502:physiology*
keywords: conservation; extinction; functional diversity; null models; rarity index; tropical biodiversity