Shifts in species richness, herbivore specialization, and plant resistance along elevation gradients


  • This work was supported by ECOCHANGE project, contract number. FP6 2006 GOCE 036866); Swiss Science Foundation grant number 31003A-125145 (BIOASSEMBLE project); Swiss Science Foundation Ambizione grant PZ00P3_131956/1.


Sergio Rasmann, Department of Ecology and Evolution, University of Lausanne, Bâtiment Biophore, CH-1015 Lausanne, Switzerland. Tel: +4121 692 42 63; Fax: +4121 692 41 65; E-mail:


Environmental gradients have been postulated to generate patterns of diversity and diet specialization, in which more stable environments, such as tropical regions, should promote higher diversity and specialization. Using field sampling and phylogenetic analyses of butterfly fauna over an entire alpine region, we show that butterfly specialization (measured as the mean phylogenetic distance between utilized host plants) decreases at higher elevations, alongside a decreasing gradient of plant diversity. Consistent with current hypotheses on the relationship between biodiversity and the strength of species interactions, we experimentally show that a higher level of generalization at high elevations is associated with lower levels of plant resistance: across 16 pairs of plant species, low-elevation plants were more resistant vis-à-vis their congeneric alpine relatives. Thus, the links between diversity, herbivore diet specialization, and plant resistance along an elevation gradient suggest a causal relationship analogous to that hypothesized along latitudinal gradients.