Mountain birch under multiple stressors--heavy metal-resistant populations co-resistant to biotic stress but maladapted to abiotic stress.

Stress adaptations often include a trade-off of weakened performance in nonlocal conditions, resulting in divergent selection, and potentially, genetic differentiation and evolutionary adaptation. Results of a two-phase (greenhouse and field) common garden experiment demonstrated adaptation of mountain birch (Betula pubescens subsp. czerepanovii) populations from industrially polluted areas of the Kola Peninsula, north-western Russia, to heavy metals (HM), whereas no adaptations to wind or drought stress were detected in populations from wind-exposed sites. HM-adapted seedlings were maladapted to drought but less palatable (co-resistant) to insect herbivores, even under background HM concentrations. The absence of adaptations to harsh microclimate and the generally high adaptive potential of mountain birch, a critical forest forming tree in subarctic Europe, need to be accounted for in models predicting consequences of human-driven environmental changes, including the projected climate change.

Rapid evolution towards heavy metal resistance by mountain birch around two subarctic copper-nickel smelters.

Adaptations to pollution among long-lived trees have rarely been documented, possibly because of their long reproductive cycles and the evolutionarily short timescales of anthropogenic pollution. Here, I present the results of a greenhouse experiment that suggest rapid evolutionary adaptation of mountain birch [Betula pubescens subsp. czerepanovii (Orlova) Hämet-Ahti] to heavy metal (HM) stress around two copper-nickel smelters in NW Russia. The adaptation incurs a cost with reduced performance of adapted seedlings in pristine conditions. The industrial barrens around the studied smelters are extremely high-stress sites with low seed germination and survival. It is likely that strong natural selection has eliminated all sensitive genotypes within one or two generations, with only the most tolerant individuals persisting and producing adapted seeds in the individual barrens. The results were similar from around both smelters, suggesting parallel evolution towards HM resistance.

Variation of phlorotannins among three populations of Fucus vesiculosus as revealed by HPLC and colorimetric quantification.

In ecological studies, phlorotannins have conventionally been quantified as a group with similar functionality. Since this group consists of oligo- and polymers, the quantification of their pooled contents alone may not sufficiently describe the variation of these metabolites. Genetic variation, plastic responses to environment, and the ecological functions of separate phlorotannin oligo- and polymers may differ. Two analyses, i.e., the colorimetric Folin-Ciocalteu assay and a normal-phase high-performance liquid chromatographic (HPLC) method were used to study genetic and environmental variation in phlorotannins of the brown alga Fucus vesiculosus (L.). The colorimetric method provides the total phlorotannin content, the latter a profile of 14 separate traces from the phenolic extract that represent an individual or groups of phlorotannins. We reared the algae that originated from three separate populations in a common garden for 3 months under ambient and enriched-nutrient availability and found that they differed in both their total phlorotannin content and in phlorotannin profiles. Some individual traces of the profiles separated the populations more clearly than the colorimetric assay. Although nutrient enrichment decreased total phlorotannin content, it did not show a significant influence on the phlorotannin profile. This implies that plastic responses of compounds other than phlorotannins may interfere with the determination of total phlorotannins. However, the phlorotannin profile and the total content showed genetic variation among local populations of F. vesiculosus; therefore, phlorotannins may respond to natural selection and evolve both quantitatively and qualitatively.