title: Effects of elevated CO2on flowering phenology and nectar production of nectar plants important for butterflies of calcareous grasslands.
abstract: Effects of elevated CO2on flowering phenology and nectar production were investigated in Trifolium pratense, Lotus corniculatus, Scabiosa columbaria, Centaurea jacea and Betonica officinalis, which are all important nectar plants for butterflies. In glasshouse experiments, juvenile plants were exposed to ambient (350 μl l-1) and elevated (660 μl l-1) CO2concentrations for 60-80 days. Elevated CO2significantly enhanced the development of flower buds in C. jacea. B. officinalis flowered earlier and L. corniculatus produced more flowers under elevated CO2. In contrast, the number of flowers decreased in T. pratense. The amount of nectar per flower was not affected by elevated CO2in the tested legumes (T. pratense and L. corniculatus), but was significantly reduced (!) in the other forbs. Elevated CO2did not significantly affect nectar sugar concentration and composition. However, S. columbaria and C. jacea produced significantly less total sugar under elevated CO2. The nectar amino acid concentration remained unaffected in all investigated plant species, whereas the total of amino acids produced per flower was reduced in all non-legumes. In addition, the amino acid composition changed significantly in all investigated species except for C. jacea. The observed effects are unexpected and are a potential threat to flower visitors such as most butterflies which have no alternative food resources to nectar. Changes in nectar production due to elevated CO2could also have generally detrimental effects on the interactions of flowers and their pollinators.
authors.affiliation: Botanisches Institut der Universität Basel, Schönbeinstrasse 6, CH-4056 Basel, Switzerland, , , , , , CH.
authors.forename: Hans Peter
authors.initials: HP
authors.lastname: Rusterholz
authors.affiliation: Botanisches Institut der Universität Basel, Schönbeinstrasse 6, CH-4056 Basel, Switzerland, , , , , , CH.
authors.forename: Andreas
authors.initials: A
authors.lastname: Erhardt
keywords: Amino acids; Key words Elevated CO2; Nectar; Phenology; Sugar