Past climatic fluctuations are associated with morphological differentiation in the cloud forest endemic tree <Emphasis Type="Italic">Ocotea psychotrioides</Emphasis> (Lauraceae)

Pleistocene glacial periods have had a major influence on the geographical patterns of genetic structure of species in tropical montane regions. However, their effect on morphological differentiation among populations of cloud forest plants remains virtually unexplored. Here, we address this question by testing whether geographical patterns of morphological variation in Ocotea psychotrioides can be explained by the intensity of climate change occurring during 130,000 years. For this, we measured vegetative and reproductive traits for 96 individuals from 36 localities registered across the species’ distribution range. Species distribution models and multivariate statistics were used to investigate geographical patterns of morphological variation and test their association with current and past climatic conditions. Leaf size and pubescence in O. psychotrioides showed a latitudinal pattern of clinal variation that does not fit the geographical gradient of increasing leaf size towards lower latitudes observed globally among plants. Instead, the observed clinal variation conforms to a pattern of increasing leaf size towards higher latitudes. However, our analyses showed weak to non-significant association between morphology and current climate. Interestingly, our analyses showed that predicted shifts in the distribution range of O. psychotrioides during the last 130,000 years were accompanied by significant changes in climatic conditions, particularly temperature seasonality and precipitation. Accordingly, climatic instability showed a better fit to the observed patterns of leaf size and pubescence variation than current climate conditions. These results suggest that climatic instability during the Pleistocene glacial periods might play a key role in promoting morphological differentiation among populations of cloud forest plants.