%0 Book Section %B Encyclopedia of Biodiversity %D 2022 %T Species, concepts of %A Mallet, James %A Seixas, Fernando %A Thawornwattana, Yuttapong %X What are species? We take a historical approach to demonstrate how our understanding of the nature of species has changed since Darwin's time until the current postgenomic era. If species are fundamental units of nature (like cells, or organisms, say), as some scientists believe, then their underlying basis has yet to be revealed. Instead, it seems more likely that the species rank in taxonomy is a man-made distinction; a heuristic cut-off that can perhaps be agreed upon bybiologists to enable communication on issues of biodiversity, human health, agriculture, and conservation. %B Encyclopedia of Biodiversity %I Elsevier %G eng