Effects of Rising Temperatures on the Progamic Phase of High-Mountain Plants
Steinacher, G. and Wagner, J. 2012. Effect of temperature on the progamic phase in high-mountain plants. Plant Biology 14: 295-305.
In a laboratory experiment that has relevance to this question, Steinacher and Wagner assessed the efficacy of "pollen adhesion to the stigma, in vivo pollen germination, pollen tube growth and fertilization - which reflects the efficiency of the whole reproductive system - at temperatures ranging from -2 to 40°C." This they did in six herbaceous species having different altitudinal distributions in the European Alps: Gentianella germanica, which occurs from the subalpine to the alpine zone (Zopfi, 1991), Ranunculus alpestris and Saxifraga caesia, which are frequent species in the alpine zone (Zimmermann, 1975; Kaplan, 1995), and Cerastium uniflorum, Ranunculus glacialis and Saxifraga bryoides, which are typical of plant assemblages from the subnival to the nival zone.
Prior to their experiment, the two researchers say they had "expected nival species to perform better in the cold and alpine species to do better in the warmth." However, they found that "this is not always true," reporting that (1) "the alpine species G. germanica was markedly less sensitive to low temperatures than the nival species S. bryoides and C. uniflorum," and that (2) "the species from the alpine belt did not cope better with heat than the species from the nival belt."
In light of their unexpected findings, Steinacher and Wagner conclude that (1) "higher minimum temperatures might promote the reproduction of species from lower elevations and facilitate their upward migration, as already documented for a number of alpine plant species (Hofer, 1992; Grabherr et al., 1995)," and that (2) "under climate warming, which has been on-going in the Alps since the last century (Beniston et al., 1997), nival species would not be discriminated from alpine species because of a poorer pollen performance in the warmth."
And thus it would appear that there may indeed be room for all at the mountaintop.
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Zopfi, H.J. 1991. Aestival and autumnal vicariads of Gentianella (Gentianaceae): a myth? Plant Systematics and Evolution 174: 139-158.