The scent of roses (Rosa x hybrida) is composed of hundreds of volatile molecules. Monoterpenes represent up to 70% percent of the scent content in some cultivars, such as the Papa Meilland rose. Monoterpene biosynthesis in plants relies on plastid-localized terpene synthases. Combining transcriptomic and genetic approaches, we show that the Nudix hydrolase RhNUDX1, localized in the cytoplasm, is part of a pathway for the biosynthesis of free monoterpene alcohols that contribute to fragrance in roses. The RhNUDX1 protein shows geranyl diphosphate diphosphohydrolase activity in vitro and supports geraniol biosynthesis in planta.

In conservation biology genetic diversity is recognized as an important criterion to consider when prioritizing populations for protection. Today, population genomics offers the opportunity to evaluate both neutral and adaptive components of genetic diversity directly at the genome level with molecular tools. By screening the genome with many genetic markers, it is possible to detect loci supposedly under natural selection and thus of adaptive significance. We devised a new diversity index, the population adaptive index (PAI), which accounts for the adaptive value of the population it refers to. To estimate this index, we performed a genome scan with amplified fragment length polymorphism markers to identify neutral and selected loci in several populations of a widespread amphibian (common frog, Rana temporaria) and a threatened plant (Austrian dragonhead, Dracocephalum austriacum L.). We then investigated four different conservation strategies aimed at protecting the maximum amount of genetic diversity (neutral or selected). In particular we explored the relevance of the principle of complementarity, usually applied to the protection of species, in the management of intraspecific diversity. This principle advocates the conservation of sets of units that together maximize the species' or genetic diversity, which is in opposition to the traditional approach of targeting populations that are the most diverse individually. Four major conclusions emerged from these results. First, the PAI seemed to be a valuable index to evaluate the adaptive diversities within populations. Second, in the two species, the neutral and adaptive diversities within and among populations were not correlated, so conservation strategies based on the neutral and adaptive indexes would not select the same populations for protection. Third, because of its efficiency in conserving genetic diversity, the principle of complementarity deserves to be used more often for this purpose. Fourth, when neutral and adaptive results conflict, additional arguments (e.g., demography, ecology, and geographic proximity) should be considered together with levels of genetic diversity to determine a conservation strategy.

Summary 1.To predict the viability of populations, it is essential to clarify how performance depends both on large-scale environmental changes, such as climate warming, and on the local habitat. However, in spite of their potential importance, effects of interactions between large-scale environmental changes and the local environment on population viability have rarely been examined. 2. We investigated how population dynamics of the endangered alpine plant Dracocephalum austriacum depend on local habitat quality and climatic variation, as well as how effects of climate depend on local habitat. We used lasso regression shrinkage and integral projection models to identify effects on vital rates and population growth rates in seven populations over seven annual transitions. 3. Populations on steeper slopes had lower survival and stochastic population growth rate than populations on more gentle slopes. In years with low spring temperatures and high summer temperatures, survival and population growth rate were lower. In addition, the negative effects of high summer temperatures did depend on local habitat quality, being more negative in populations on steeper slopes. 4. Combining the net positive effects of high spring temperature and the net negative effects of high summer temperature on plant vital rates with predicted climate change over the next 30 years suggested that effects on D. austriacum would be relatively small. 5. Synthesis. Our results show that different aspects of a warmer climate may have opposing effects on populations, and that climatic effects may depend on local habitat quality. Such interactive effects should be accounted for when determining effects of large-scale environmental changes on population and community dynamics.