Plant Genetic Diversity and Plant–Pollinator Interactions Along Altitudinal Gradients

Abstract

Alpine plants are thought to be particularly vulnerable to extinction as a result of global warming because their habitat ranges are expected to shift upward until, eventually, no higher habitats remain into which they can escape. Moreover, even mountain plants distributing across wide altitudinal ranges are likely to experience range shifts, raising the possibility of local extinctions, especially of genetically and ecologically differentiated types with narrow distribution ranges. In this chapter, we examine to what extent plants genetically and ecologically differentiate along altitude and how altitudinal changes in pollinator assemblages affect floral evolution. First, by literature survey, we demonstrate that although altitudinal patterns of species and genetic diversity have been extensively investigated, few clear-cut examples of altitudinal genetic differentiation of neutral markers have been identified. On the other hand, many studies have shown that adaptive traits of plants differentiate along altitude, although their adaptive genetic background is yet to be uncovered. We then briefly introduce three case studies of mountain herbaceous plant species displaying cryptic neutral genetic or adaptive trait differentiation. The first two case studies show that the floral size of both Campanula punctata and Prunella vulgaris differs among populations along altitude and is adapted to altitudinally variable pollinator size. The third case study demonstrates that Cimicifuga simplex is composed of three genetically differentiated ecotypes that are distributed parapatrically or allopatrically along an altitudinal gradient. To meet the challenges posed by future climate warming, it is essential to clarify the genetic and ecological differentiation of mountain plants along altitude.