matter of scale: apparent niche differentiation of diploid and tetraploid plants may depend on extent and grain of analysis

• Published in: Journal of biogeography Vol. 43; no. 4; pp. 716 - 726
• Main Authors: Kirchheimer, Bernhard, Schinkel, Christoph C. F, Dellinger, Agnes S, Klatt, Simone, Moser, Dietmar, Winkler, Manuela, Lenoir, Jonathan, Caccianiga, Marco, Guisan, Antoine, Nieto‐Lugilde, Diego, Svenning, Jens‐Christian, Thuiller, Wilfried, Vittoz, Pascal, Willner, Wolfgang, Zimmermann, Niklaus E, Hörandl, Elvira, Dullinger, Stefan
• Format: Journal Article
• Language: English
• Published: England Blackwell Scientific Publications 01.04.2016; Blackwell Publishing Ltd; John Wiley & Sons Ltd; Wiley Subscription Services, Inc; Wiley; John Wiley and Sons Inc
• Subjects: alpine plants; ancestry; apomixis; Biodiversity; Biodiversity and Ecology; competition; cytotypes; data collection; diploidy; Ecology, environment; Environmental Sciences; European Alps; Global Changes; indicator values; Life Sciences; niche breadth; niche shift; niches; Original; polyploidization; Polyploidy and Niches; principal component analysis; Ranunculus; Ranunculus kuepferi; spatial grain; temperature; tetraploidy; vegetation; Alps region; apomixis; polyploidization; European Alps; alpine plants; Ranunculus kuepferi; competition; niche shift; spatial grain; indicator values; niche breadth
• ISSN: 0305-0270; 1365-2699
• DOI: 10.1111/jbi.12663

AIM: Emerging polyploids may depend on environmental niche shifts for successful establishment. Using the alpine plant Ranunculus kuepferi as a model system, we explore the niche shift hypothesis at different spatial resolutions and in contrasting parts of the species range. LOCATION: European Alps. METHODS: We sampled 12 individuals from each of 102 populations of R. kuepferi across the Alps, determined their ploidy levels, derived coarse‐grain (100 × 100 m) environmental descriptors for all sampling sites by downscaling WorldClim maps, and calculated fine‐scale environmental descriptors (2 × 2 m) from indicator values of the vegetation accompanying the sampled individuals. Both coarse and fine‐scale variables were further computed for 8239 vegetation plots from across the Alps. Subsequently, we compared niche optima and breadths of diploid and tetraploid cytotypes by combining principal components analysis and kernel smoothing procedures. Comparisons were done separately for coarse and fine‐grain data sets and for sympatric, allopatric and the total set of populations. RESULTS: All comparisons indicate that the niches of the two cytotypes differ in optima and/or breadths, but results vary in important details. The whole‐range analysis suggests differentiation along the temperature gradient to be most important. However, sympatric comparisons indicate that this climatic shift was not a direct response to competition with diploid ancestors. Moreover, fine‐grained analyses demonstrate niche contraction of tetraploids, especially in the sympatric range, that goes undetected with coarse‐grained data. MAIN CONCLUSIONS: Although the niche optima of the two cytotypes differ, separation along ecological gradients was probably less decisive for polyploid establishment than a shift towards facultative apomixis, a particularly effective strategy to avoid minority cytotype exclusion. In addition, our results suggest that coarse‐grained analyses overestimate niche breadths of widely distributed taxa. Niche comparison analyses should hence be conducted at environmental data resolutions appropriate for the organism and question under study.