Interactions between growth, demography and biotic interactions in determining species range limits in a warming world: the case of Pinus sylvestris

Changes in climate are affecting the distribution and status of species on a global scale, through alteration of factors including their phenology, growth and ecological interactions. These alterations are often most apparent at species range edges, where changes to conditions previously limiting the species distribution can result in range shifts. In this paper, we review the rapid recent increase in our understanding of the factors limiting the distribution of a species to explore how the interaction of biotic and abiotic factors is likely to significantly alter its range edge behaviour beyond our current predictive capacity. We focus on Scots pine (Pinus sylvestris L.), one of the most abundant tree species on the globe. Glacial refugia and colonisation routes after last glacial maximum have strongly influenced the genetic diversity and local adaptation of this species. Over recent decades, increased reproduction and growth has been detected at the northern limit of P. sylvestris as a response to increased temperature, whereas at its southern limit, increased drought stress has resulted in decreased growth, low recruitment, and in some cases a massive mortality of this species. In addition, direct climatic effects on the species are acting together with indirect effects due to altered biotic interactions including outbreaks of insects, pathogens, and parasites, and increased herbivory linked to declining ecosystem productivity. However, whilst predictive studies forecast a gradual decline of the species at the southern range limit and expansion at higher latitudes, models do not commonly include biotic factors, which can significantly modify the response of the species to climatic changes. We conclude by discussing the early detection of imperilled areas and how their natural resistance and resilience to ongoing climatic changes might be increased