Desert‐like badlands and surrounding (semi‐)dry grasslands of Central Germany promote small‐scale phenotypic and genetic differentiation inThymus praecox

Abstract

Environmental heterogeneity among sites can generate phenotypic and genetic variation facilitating differentiation and microevolution of plant populations. Badlands are desert‐like, predominantly vegetation‐poor habitats often embedded in (semi‐)dry grasslands. The desert‐like conditions of badlands demand extreme adaptation of plants, that is, phenotypic modifications in short‐term and/or natural adaptation in long‐term. However, detailed knowledge is missing about both plant phenotypic and genetic differentiation in this unique and widely occurring habitat type. The present study focused on the largest known badlands systems in Central Europe located in the “Drei Gleichen” region, a designated nature conservation area in Central Germany. Locations were suitable for this study in terms of having co‐occurring badlands and (semi‐)dry grassland habitats (sites) occupied by the pioneer plant Thymus praecox. Here, we studied the environmental preferences, morphological and functional trait variation, and genetic variation using microsatellite markers of T. praecox. Results revealed significant, mainly site‐dependent environmental, phenotypic, and genetic differentiation. In general, individuals in badlands are shorter in height and have lower patch sizes (length × width), relative growth rates, and smaller stomata. The PCA additionally unveiled slightly increased leaf robustness, trichome density, decreased stomatal conductance, fewer females, and earlier phenology in badlands. We interpret differentiation patterns as adaptive responses to light, temperature, drought, and nutrient stress conditions supported by reviewed literature. Genetic differentiation was strongest between local badlands and grassland sites, and clearly weaker among locations and between sites (in total) as indicated by GST, AMOVA, PCoA, and population structure. Our study supports the importance of small‐scale microhabitat conditions as a driver of microevolutionary processes, and the population's need for sufficient phenotypic variation and genetic resources to deal with environmental changes. We demonstrated that badlands are an appropriate model system for testing plant response to extreme habitats and that more research is needed on these fascinating landscapes.

Plant intraspecific functional trait variation is related to within‐habitat heterogeneity and genetic diversity inTrifolium montanumL.

“…Intraspecific functional trait variation captured by iFD CV is probably the response of populations to increased abiotic and biotic environmental differences within their habitats (see also Ghalambor et al, 2007; Nicotra et al, 2010, 2015): as shown, iFD CV was positively correlated to within‐habitat heterogeneity, suggesting that the more environmentally variable a habitat, the higher the intraspecific functional trait variation in T. montanum populations. Results are line with literature showing associations between functional trait values and diversity, and environmental conditions within and across species (e.g., Albert et al, 2010; Bernhardt‐Römermann, Gray, et al, 2011; Bucher et al, 2016; Díaz & Cabido, 2001; Gratani, 2014; Karbstein et al, 2019; König et al, 2018; Violle et al, 2007). Intraspecific functional differences are known to facilitate a more flexible response to varying abiotic conditions (see, e.g., Bucher et al, 2016 for elevational gradients; Karbstein et al, 2019 for small‐scale habitat differences).…”

“…Results are line with literature showing associations between functional trait values and diversity, and environmental conditions within and across species (e.g., Albert et al, 2010; Bernhardt‐Römermann, Gray, et al, 2011; Bucher et al, 2016; Díaz & Cabido, 2001; Gratani, 2014; Karbstein et al, 2019; König et al, 2018; Violle et al, 2007). Intraspecific functional differences are known to facilitate a more flexible response to varying abiotic conditions (see, e.g., Bucher et al, 2016 for elevational gradients; Karbstein et al, 2019 for small‐scale habitat differences). Thus, iFD CV likely affects population growth and reproduction with positive consequences for survival and fitness (see also Nock et al, 2016; Violle et al, 2007).…”

“…Genetic diversity is considered to be fundamental for population fitness and evolutionary processes, and influences adaptive potential of a species with respect to environmental changes, competitors or pathogens (Arnold et al, 2019; Boulding, 2008; Chevin & Hoffmann, 2017; Karbstein, Tomasello, & Prinz, 2019; Lande, 2009; Nicotra et al, 2010; Reed & Frankham, 2003). Relationships between genetic diversity and “traditional” fitness parameters (e.g., number of flowers, seeds and fruits, and seed weight) or life‐history traits have been investigated intensely both within and across species (Freeland, Kirk, & Petersen, 2011; Leimu, Mutikainen, Koricheva, & Fischer, 2006; Reed & Frankham, 2003; Reisch & Bernhardt‐Römermann, 2014).…”

“…In some model plants, functional trait plasticity related to morphology (e.g., plant height), ecophysiology (e.g., water‐use efficiency), and life history (e.g., flowering time and seed traits) was found to be under genetic control (Ackerly et al, 2000; Hughes, Soppe, & Albani, 2019; Locascio, Lucchin, & Varotto, 2009; Thornsberry et al, 2001). Moreover, studies also indicate phenotypic and genetic connections, and also, more explicitly, correlations between phenotypic traits and genetic variation (Csilléry et al, 2020; Karbstein et al, 2019; Waitt & Levin, 1998). Waitt and Levin (1998) impressively showed positive correlations between the phenotypic variation of morphology‐related functional traits and genetic variation in several species from different plant families.…”

The role of light in the adaptation of Thymus praecox Opiz subsp. praecox for diverse habitat conditions

“…There are few publications on this taxon in the literature. They concern cytological, genetic and biochemical issues, some of its subspecies (Trela-Sawicka, 1972;Mártonfi and Mártonfiová, 1996;Avci, 2011;Karbstein et al, 2019).…”