Mountain roads and non-native species modify elevational patterns of plant diversity

HAIDER, SYLVIA; KUEFFER, CHRISTOPH; BRUELHEIDE, HELGE; SEIPEL, TIM; ALEXANDER, JAKE M.; REW, LISA J.; ARÉVALO, JOSÉ RAMÓN; CAVIERES, LOHENGRIN A.; MCDOUGALL, KEITH L.; MILBAU, ANN; NAYLOR, BRIDGETT J.; SPEZIALE, KARINA; PAUCHARD, ANÍBAL

Global Ecology and Biogeography

WILEY-BLACKWELL PUBLISHING, INC

Año: 2018 vol. 27 p. 667 - 678

1466-822X

Aim: Elevational species richness patterns havefascinated ecologists for centuries, yet there remains little consensus about general patterns . We conducted the first globally replicated, standardized survey of vascular plants alongelevation gradients toseek consistent patterns in species richness trends and communitydissimilarity. Additionally, we investigated how patterns are influenced byanthropogenic pressure (represented by increased human-assisted dispersal ofplants, disturbance and altered abiotic conditions at mountain roads) and non-nativespecies.Location: GlobalMethods: Native and non-native vascular plant specieswere recorded in 943 plots along twenty-five elevation gradients, in ninemountain regions, on four continents. Sampling took place in plots along and away from roads. We analyzed the effects of elevation,distance from road and non-native species richness on native species richnesspatterns and community dissimilarity.Results: Globally,native and total species richness showed a unimodal relationship with elevationthat peaked at lower-mid elevations. Region-specific patterns disappeared at roadsides and non-native specieschanged the patterns? character in all study regions. Community dissimilaritywas reduced alongside roads and through non-nativespecies. We found a significant elevation-decay of beta-diversityin interior plots, which  was not significantlydifferent at roadsides or when non-native species were included.Main conclusions: Idiosyncratic native species richness patterns in natural habitats pointto region-specific underlying mechanisms. However, roadsides, which are associatedwith increased disturbance, higher propagule pressure and higher habitathomogeneity, a clearer elevational signal emerged and species richness mostlypeaked at mid-elevations. Such roadside characteristics might also have causedthe shift of highest native community dissimilarity from high to mid-elevationsWe conclude that three mechanisms ?increased human-assisted dispersal, higher habitat homogeneity, and presence ofgeneralist (alien) species ­? drive biotic homogenisation along environmentalgradients at a regional scale