title: Ecological emergence of thermal clines in body size.
abstract: The unprecedented rate of global warming requires a better understanding of how ecosystems will respond. Organisms often have smaller body sizes under warmer climates (Bergmann's rule and the temperature-size rule), and body size is a major determinant of life histories, demography, population size, nutrient turnover rate, and food-web structure. Therefore, by altering body sizes in whole communities, current warming can potentially disrupt ecosystem function and services. However, the underlying drivers of warming-induced body downsizing remain far from clear. Here, we show that thermal clines in body size are predicted from universal laws of ecology and metabolism, so that size-dependent selection from competition (both intra and interspecific) and predation favors smaller individuals under warmer conditions. We validate this prediction using 4.1 × 10(6) individual body size measurements from French river fish spanning 29 years and 52 species. Our results suggest that warming-induced body downsizing is an emergent property of size-structured food webs, and highlight the need to consider trophic interactions when predicting biosphere reorganizations under global warming.
authors.affiliation: Université Pierre et Marie Curie - Paris 6, UMR 7618 BIOEMCO, Ecole Normale Supérieure, 46 rue d'Ulm, 75230, Paris Cedex 05, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Edeline
authors.forename: Gérard
authors.initials: G
authors.lastname: Lacroix
authors.forename: Christine
authors.initials: C
authors.lastname: Delire
authors.forename: Nicolas
authors.initials: N
authors.lastname: Poulet
authors.forename: Stéphane
authors.initials: S
authors.lastname: Legendre
mesh_terms: D000818:Animals; D044822:Biodiversity; D049628:Body Size; D003163:Competitive Behavior; D005399:Fishes / Q000033:anatomy & histology* / Q000502:physiology; D020387:Food Chain; D008954:Models, Biological; D011235:Predatory Behavior; D013696:Temperature
keywords: Bergmann's rule; community interactions; food-web structure; life history; metabolic theory of ecology; niche theory; predator-prey size ratio; size distributions; temperature-size rule; thermal reaction norms