Within-species Diversity as a Potential Tool in Climate Change Adaptation

Given the above mentioned velocity of climate change and the involved negative impacts on grassland and forest ecosystems, nature conservation, agriculture and silviculture have to adopt counteracting practices that aim on supporting dispersal and facilitating adaptability in order to maintain ecosystem functioning and thus the provision of ecosystem goods and services. Traditional assessments of climate change impact on species with climatic envelopes (Thomas et al. 2004; Thuiller et al. 2005; Kölling 2007) might misinterpret the adaptive capacity of a species to changing conditions. Within-species diversity is potentially important in this context.

Populations within species or taxa are known to differ phenotypically. Provenance-trials have a long tradition in forestry and have been conducted for more than a century now (e.g.

vonWuehlisch et al. 1995) Evidence from these trials suggests that differentiation within

species is distinct, at least in forest trees. For grassland species, only a few experiments considered within-species variation (Fetcher and Shaver 1990; Ryser and Aeschlimann 1999).

These differences in phenotypic expression could be underlined on a genotypic level by molecular methods for forest trees (Magri et al. 2006) and common grass species (Michalski et al. 2010). Generally this phenotypic and genetic variation is expressed in local adaptation to climate conditions or other abiotic factors such as soil type (e.g. Joshi et al. 2001; Hufford and Mazer 2003; Savolainen et al. 2007; Chen et al. 2010; Ofir and Kigel 2010).

Especially species with large distribution ranges that cover a broad range of climatic conditions, such as F. sylvatica are likely to display high levels of within-species variation and adaptation to local conditions. In forestry, the introduction of provenances or ecotypes from regions within the distribution range of the species with current climatic conditions similar to the projected conditions for the target area has therefore been suggested as one potential tool in climate change adaptation (Hemery 2008; Bolte et al. 2009; Bolte and Degen 2010). For grassland species this has been not yet discussed on a mentionable level, yet, in spite of the deficit in studies which examine local adaptation and its implication for climate adaptation in grass species, Macel et al. (2007) found evidence for a local adaptation to climatic factors in two ecotypes of Holcus lanatus.

F. sylvatica exhibits a high genetic diversity within in populations in Central Europe (Konnert 1995; Vornam et al. 2004). Looking at the distribution range on a continental scale the genetic differences between populations become more distinct (Comps et al. 1990; Magri et al. 2006).

The genetic composition and diversity of populations determine their phenotypic plasticity and thus their adaptive capacity (Schaberg et al. 2008; Matyas et al. 2009), so differences in genetic configuration most likely display differences in adaptive capacities between populations. In several provenance trials, distinct responses of provenances of F. sylvatica to climatic stressors, such as drought, have been demonstrated (Schraml and Rennenberg 2000;

Peuke et al. 2006; Czajkowski and Bolte 2006). Evidence for macroclimatic adaptation could be detected in a European-wide provenance-trial network, where the performance of different provenances was negatively correlated with climatic distance between test-site and origin of provenance (Matyas et al. 2009). Yet, also in the field local adaptations to drought are found.

In the extraordinary dry year 2003, beech populations in Greece only experienced mild drought stress compared to Central European beech forests (Fotelli et al. 2009), which indicates an adaptation of Greek populations to drought conditions. Especially these marginal populations, which face more adverse conditions and are thus under stronger genetic selection

(Wortemann et al. 2011), are therefore under focus in the search of drought-resistant ecotypes (Rose et al. 2009).

Supported by its scattered distribution range, P. nigra also shows strong genetic differences between populations and subspecies (Jagielska et al. 2007; Soto et al. 2010). This genetic differentiation is supposed to have been enhanced by geographic isolation during the Pleistocene (Aguinagalde et al. 1997). Provenance trials showed a non-uniform performance of P.nigra provenances from various geographic origins (Varelides et al. 2001; Seho et al.

2010); however, differences in response to climatic stressors, such as drought, could not be proven yet, as the high drought tolerance across population might prevent a strong selection.

Considering the outlined potential impacts of changing climatic conditions on functions and services of grasslands and forest ecosystems it is important to know, whether specific provenances or ecotypes of key species are more or less susceptible or better adapted to climatic stressors, such as drought, heat or frost. This knowledge can be crucial to assess the potential of selective transplanting of climate-resistant provenances or ecotypes of native or exotic species as a tool of coping and adaptation strategy in agriculture and forestry to dampen the harmful impacts of such extremes in the face of climate change (Manuscripts 2, 3, 4, 5, 7, 8, 9). Unlike in economics, ecosystem management has hardly introduced risk management into decision making processes until today, despite the strong risk of an uncertain future in terms of climatic conditions (Knoke et al. 2005; Hanewinkel et al. 2011).

In economics, the risk of a complete loss of profits is reduced by a diversification of investments. This effect is called the portfolio effect and was described by Markowitz (1952).

In ecology, a comparable concept, the insurance hypothesis, describes a the positive effect of biodiversity on ecosystem functioning and reliability, as the higher number of species, the more likely the function of a failing species can be adopted by other species in the system (Yachi and Loreau 1999). The conversion of monocultures into mixed forests, i.e. an increase of species diversity as insurance against adverse biotic and abiotic impactshas become popular over the last decades (Knoke et al. 2005), yet the role that within-species diversity could play in this context just recently came into focus of forest science and management.

With respect to the described uncertainties and the potential positive effects of biodiversity on risk abatement, the mixing of provenances has been suggested by several authors (Kolström et al. 2011; Frascaria-Lacoste and Fernández-Manjarrés 2012). However, evidence has to be provided whether an anthropogenic enhancement of genotypic diversity and phenotypic plasticity, e.g. by intermixing local, highly-adapted and very plastic provenances from

different climatic regions, may maintain high yields under favourable conditions and securing ecosystem functioning, persistence and services under extreme conditions (Manuscript 8).