Extensive variation, but not local adaptation in an Australian alpine daisy

Abstract

Alpine plants often occupy diverse habitats within a similar elevation range, but most research on local adaptation in these plants has focused on elevation gradients. In testing for habitat‐related local adaptation, local effects on seed quality and initial plant growth should be considered in designs that encompass multiple populations and habitats. We tested for local adaptation across alpine habitats in a morphologically variable daisy species, Brachyscome decipiens, in the Bogong High Plains in Victoria, Australia. We collected seed from different habitats, controlled for maternal effects through initial seed size estimates, and characterized seedling survival and growth in a field transplant experiment. We found little evidence for local adaptation for survival or plant size, based on three adaptation measures: Home versus Away, Local versus Foreign, and Sympatric versus Allopatric (SA). The SA measure controlled for planting site and population (site‐of‐origin) effects. There were significant differences due to site‐of‐origin and planting site effects. An important confounding factor was the size of plants directly after transplantation of seedlings, which had a large impact on subsequent seedling survival and growth. Initial differences in plant width and height influenced subsequent survival across the growing season but in opposing directions: wide plants had higher survival, but tall plants had lower survival. In an additional controlled garden experiment at Cranbourne Royal Botanic Gardens, site‐of‐origin effects detected in the field experiments disappeared under more benign homogeneous conditions. Although B. decipiens from different source areas varied significantly when grown across a range of alpine habitats, these differences did not translate into a local or habitat‐related fitness advantage. This lack of local advantage may signal weak past selection, and/or weak adaptive transgeneration (plasticity) effects.

Are local plants the best for ecosystem restoration? It depends on how you analyze the data

“…The most rigorous method of testing for local adaptation is reciprocal transplant experiments (Blanquart, Kaltz, Nuismer, & Gandon, 2013). Most knowledge on local adaptation comes from such studies of individual species (e.g., Bischoff & Trémulot, 2011;Mendola, Baer, Johnson, & Maricle, 2015;Mathiasen & Premoli, 2016;Evans et al, 2016;Hirst, Sexton, & Hoffmann, 2016;Lu, Parker, Colombo, Man, & Baeten, 2016 and many others). While a classical reciprocal transplant experiment involves at least two origins of a single species transplanted reciprocally to both sites of origin, some studies simplified this design to only multiple origins in one site (Gellie, Breed, Thurgate, Kennedy, & Lowe, 2016;Hancock, Leishman, & Hughes, 2013), whereas others have extended it to multiple origins of multiple species in multiple sites (e.g., Bischoff et al, 2006;Bucharova et al, 2017;Carter & Blair, 2012;Joshi et al, 2001;Körner et al, 2016;Kramer, Larkin, & Fant, 2015).…”

“…Third, the "sympatric vs. allopatric" approach (unfortunately sometimes called "home vs. away" in older studies) uses multiple local populations and compares the general performance of plants growing in their local environments (sympatric) with plants growing outside their local environments (allopatric). Only the last approach allows to detect general patterns in local adaptation as it is not site-specific (Blanquart et al, 2013), as exemplified by Joshi et al (2001), Bischoff et al (2006), Hirst et al (2016. The analysis approach depends on the experimental design.…”

High intraspecific phenotypic variation, but little evidence for local adaptation in Geum reptans populations in the Central Swiss Alps

“…While it is possible that local adaptation may take more time than allowed in our experiment to express depending on plant longevity (Bennington et al 2012;Hirst et al 2016), the most likely explanation for the lack of local adaptation in our study is related to the narrow habitat niche of G. reptans. This species grows at high elevation, typically in glacier forelands, close to the glacier snout, and in moist scree fields (Aeschimann et al 2004).…”

“…An alternative, not mutually exclusive, explanation for the lack of local adaptation in our study could be that highly plastic phenotypic responses to local environmental conditions may overcome the need for genetic differentiation among populations, especially in perennial herbs (Antonovics and Primack 1982;Bazzaz 1996;Cheplick 2015;Hirst et al 2016). Indeed, our study revealed that G. reptans had a great capacity to respond plastically to environmental conditions (Tables 2, 3), which can represent a means to maximize plant performance in heterogeneous environments (Alpert and Simms 2002;Stöcklin et al 2009;Nicotra et al 2010).…”

“…Evidence for local adaptation has been found in a number of alpine plant populations (Gonzalo-Turpin and Hazard 2009;Fischer et al 2011;Giménez-Benavides et al 2011;Hamann et al 2016); however, an extensive meta-analysis and another recent study suggest that local adaptation may be less common than frequently assumed (Leimu and Fischer 2008;Hirst et al 2016). Extensive gene flow among populations has been recognized as a main hindrance for local adaptation (Kawecki and Ebert 2004).…”