Glacial History Affected Phenotypic Differentiation in the Alpine Plant, Campanula thyrsoides

Abstract

Numerous widespread Alpine plant species show molecular differentiation among populations from distinct regions. This has been explained as the result of genetic drift during glacial survival in isolated refugia along the border of the European Alps. Since genetic drift may affect molecular markers and phenotypic traits alike, we asked whether phenotypic differentiation mirrors molecular patterns among Alpine plant populations from different regions. Phenotypic traits can be under selection, so we additionally investigated whether part of the phenotypic differentiation can be explained by past selection and/or current adaptation. Using the monocarpic Campanula thyrsoides as our study species, a common garden experiment with plants from 21 populations from four phylogeographic groups located in regions across the Alps and the Jura Mountains was performed to test for differentiation in morphological and phenological traits. Past selection was investigated by comparing phenotypic differentiation among and within regions with molecular differentiation among and within regions. The common garden results indicated regional differentiation among populations for all investigated phenotypic traits, particularly in phenology. Delayed flowering in plants from the South-eastern Alps suggested adaptation to long sub-mediterranean summers and contrasted with earlier flowering of plants experiencing shorter growing seasons in regions with higher elevation to the West. Comparisons between molecular and phenotypic differentiation revealed diversifying selection among regions in height and biomass, which is consistent with adaptation to environmental conditions in glacial refugia. Within regions, past selection acted against strong diversification for most phenotypic traits, causing restricted postglacial adaptation. Evidence consistent with post-glacial adaptation was also given by negative correlation coefficients between several phenotypic traits and elevation of the population's origin. In conclusion, our study suggests that, irrespective of adaptation of plants to their current environment, glacial history can have a strong and long-lasting influence on the phenotypic evolution of Alpine plants.

Evolutionary melting pots: a biodiversity hotspot shaped by ring diversifications around the Black Sea in the Eastern tree frog (Hyla orientalis)

“…parts of a species' ranges where most of its diversity is concentrated) and the mechanisms causing their formation have become an important field of research (Petit et al 2003;Hewitt 2004;G omez & Lunt 2006;Feliner 2011). Hotspots constitute appealing frameworks to address fundamental topics in evolutionary biology, such as local adaptation (Margraf et al 2007;Scheepens & St€ ocklin 2011;Haase et al 2013;Scheepens et al 2013), vicariant speciation (Hewitt 1996;Martin & McKay 2004;Carstens & Knowles 2007), genetic interactions between diverging lineages (Colliard et al 2010;Hewitt 2011;, the biogeographic variation in evolutionary significant traits (Dufresnes et al 2014a,e) and the study of the geo-climatic processes shaping biodiversity (Canestrelli et al 2010;Dufresnes et al 2013). Moreover, these areas are highly valuable for the long-term survival of species because they harbour most of their genetic resources and thus adaptive potential to cope with sudden environmental changes (Hampe & Petit 2005;Dufresnes & Perrin 2015).…”

“…; Scheepens et al . ), vicariant speciation (Hewitt ; Martin & McKay ; Carstens & Knowles ), genetic interactions between diverging lineages (Colliard et al . ; Hewitt ; Dufresnes et al .…”

Trade-off among different anti-herbivore defence strategies along an altitudinal gradient

“…We know a good deal about mechanisms of plant-trait differentiation and local adaptation along steep ecological gradients ( Galen et al 1991 ; reviewed by Núñez-Farfán and Schlichting 2001 , Scheepens et al 2013 ). However, relatively few studies have investigated intraspecific variation in both direct and indirect defence in natural populations of plants ( Wason and Hunter 2014 ; Rasmann et al 2014 c ) and to the best of our knowledge, none have compared direct and indirect defences with tolerance to herbivory and plant growth along environmental gradients.…”

Environmental filtering, not local adaptation of established plants, determines the occurrence of seed- and bulbil-producing Poa alpina in a local flora

“…Local adaptation can be assumed from circumstantial evidence, i.e. by correlating population trait values from a common garden experiment with environmental conditions from the populations' origin (Linhard & Grant, 1996;Weber & Schmid, 1998;Scheepens et al, 2013). However, unequivocal evidence of local adaptation requires reciprocal transplantation experiments between a minimum of two and preferably more populations, and testing whether the outcome is compatible with divergent selection (Kawecki & Ebert, 2004;Blanquart et al, 2013).…”