Plant?plant interactions promote alpine diversification

GAVINI, S. S. ; EZCURRA, C.; AIZEN, M. A.

EVOLUTIONARY ECOLOGY

SPRINGER

Lugar: Berlin; Año: 2019 vol. 33 p. 195 - 209

0269-7653

Plant?plant interactions can promote diversification in harsh environments through (1) natural selectionproducing divergent adaptations to extreme and varying abiotic conditions in plants that grow in the open,or (2) genetic drift involving little niche differentiation in plants that grow associated with others. Weassessed whether alpine plant genera characterized by competitively-excluded or facilitated species aremore diverse than genera characterized by habitat-generalist species at both global and local scales. Basedon literature data, we characterized plant?plant interactions for 642 alpine species in 254 generaworldwide, using the relative interaction index (RII) that indicates the extent to which a plant species iscompetitively-excluded or facilitated by others. We tested whether the RII can be considered as a plant traitrelatively well-preserved at the generic level and, within a phylogenetic framework, assessed how thenumber of alpine species per genus varies along the entire gradient of plant?plant interactions at bothglobal and local scales. Species belonging to the same genus tended to be more similar in the RII-valuesthan species from different genera, with ca. 20% of the variation in RII accounted by differences amonggenera. The relation between the total number of alpine species per genus and mean RII showed twocomparable peaks, with genera in the competitive-exclusion or facilitation categories having, on average,more than twice as many species as genera in the neutral category. However, we found that morecongeneric species from the competitive-exclusion category coexist locally than congeneric species fromthe facilitation category. This pattern of plant species richness at the community level was consistent withpredictions from the hypotheses that competition promotes adaptive niche divergence at local scales,whereas facilitation promotes divergence with little niche differentiation. We conclude that both negativeand positive ecological interactions play an important role as evolutionary drivers of alpine plant diversity.