干旱区生态环境知识资源中心

Aim: Crassulacean acid metabolism (CAM) is a widespread physiological adaptation to drought. CAM is common in plants distributed in arid regions, such as Bromeliaceae species. In Chile, latitude is an accurate predictor of climate, with increasing temperature and decreasing moisture towards north. Northern species of Chilean bromeliads mainly show CAM photosynthesis, while southern-distributed species rely on the C-3 pathway. We evaluated the influence of latitude and associated climatic variables on the adoption of photosynthetic pathways by Chilean bromeliads, accounting for phylogenetic relatedness. We expected a significant relation between photosynthetic pathway and the latitudinal limits of species’ distribution ranges, independent of phylogeny.

Location: Data from Bromeliaceae species native to Chile (latitudinal distribution range: 15 degrees S to 43 degrees S).

Methods: We gathered information on geographical ranges and isotopic discrimination data (delta C-13, an indicator of photosynthetic pathway) of Chilean bromeliads. We evaluated whether delta C-13 values were related to latitude, temperature and precipitation using separate multiple linear regressions in northern and southern distribution limits of Chilean bromeliads. To account for phylogeny, we performed phylogenetically independent contrasts.

Results: In the south, delta C-13 values were not significantly correlated with latitude, temperature or precipitation. In the north, delta C-13 values were significantly correlated with latitude and annual precipitation. After phylogenetic correction, both variables were still significantly associated with delta C-13.

Main conclusions: In Chilean bromeliads, for those taxa reaching northernmost latitudes both aridity and other factors associated with latitude are probably the main drivers of adaptive evolution of CAM photosynthesis while advancing towards their present limits in arid regions. Phylogenetic relatedness also influences CAM photosynthesis in this lineage.