PARENT SESSION
Contributed Oral Session 131: Biogeography: Ranges; Species Area; Populations
Thursday, August 11, 1:30 PM - 5:00 PM, Meeting Room 515 A, Level 5, Palais des congrès de Montréal
A trade-off based framework to analyse species range sizes.
Morin, Xavier*,1, Chuine, Isabelle1, 1 Centre d'Ecologie Fonctionnelle et Evolutive, Montpellier, FRANCE
ABSTRACT- Among the few laws in ecology, the Rapoport′s rule is currently one of the most discussed in the context of biodiversity changes. This rule states that the more northern is the distribution of a species, the larger is its range. Although several hypotheses have been proposed to explain this rule (notably the climatic variability hypothesis, the competition hypothesis and the productivity gradient hypothesis), it remains incompletely understood. In this study we show that the Rapoport′s rule applies to North American and European trees, and we suggest a new framework to analyse this rule. On the basis of a phylogenetic multiple regression analysis of 242 species, we show that the range size of temperate/boreal tree species is significantly related to their successional status, with late successional species having a narrower range. With a sub-sample of species, we show that succession related traits (seed mass, height and age at maturity) explain part of the variability. However, the relationship between range size and successional status remains significant when the variability explained by these traits is removed. As late successional species are assumed more competitive than early successional ones, our findings suggest that the regional trade-off between niche breadth and competitive strength has consequences on range sizes at a continental scale. This ′trade-off based distribution framework′ reconciles the three hypotheses previously suggested to explain the Rapoport′s rule, and opens many perspectives to understand species biogeography and biodiversity patterns.
Key words: Rapoport's rule, Biogeography, Range size, Phylogenetic regressions