Effects of habitat fragmentation on nectar composition in the butterfly pollinated orchid species Gymnadenia Conopsea.
Recent comprehensive meta-analyses have demonstrated that plant traits such as breeding system and seed bank persistence mediate the response of a species to anthropogenic habitat fragmentation. In turn, some evidence has recently become available that habitat fragmentation may also exert selective forces on the plant traits themselves. One such a trait is nectar chemical composition. Nectar plays a crucial role in the interactions between plants and their pollinators and hence in mating success and mating patterns. Because of the phenotypic variation in nectar composition, its inheritability, and the direct link between nectar production and plant reproductive success, it can be expected that nectar characteristics are subject to strong selective forces. In small and isolated populations, individuals with high nectar production (or a specific chemical nectar composition) may have a strong selective advantage because they will be more attractive to the scarce insect pollinators. On the other hand, increased nectar production may increase geitonogamous pollination and cause inbreeding depression. Our general project objective is to test the hypothesis that habitat fragmentation may alter the nectar production and the nectar composition of a plant species through selection. Our study species is the rewarding moth and butterfly pollinated orchid Gymnadenia conopsea which typically occurs in highly fragmented calcareous grasslands. Specific attention will be paid to the Amino Acid composition of the nectar, as it is expected that AA composition is highly important for butterfly-pollinated species in nitrogen poor environments. More specific, we aim at quantifying variability in nectar characteristics in G. conopsea, in relation to the degree of habitat fragmentation, fruit set, degree of selfing and insect visitation rates