Latitudinal variation in life-cycle characteristics of Potamogeton pectinatus L.: vegetative growth and asexual reproduction

Abstract

Across latitudinal gradients, environmental conditions that influenceplant growth and reproduction largely change. Here we study clonal variation inlife-cycle characteristics of the cosmopolitan water plantPotamogetonpectinatus L. across a broad latitudinal range.Two consecutive experiments were performed under standardised laboratoryconditions (photoperiod, irradiance and temperature). In the first experimentweinvestigated asexual reproduction among fifteen clones, obtained from latitudesranging from 24 to 68° N. After 90 days of growth, high-latitude clonesproduced more but smaller tubers, while the aboveground biomass was lower ascompared to the clones obtained from low latitudes.In a second experiment we studied inherent differences in early growth,morphology and photosynthesis for eleven clones (obtained from the samelatitudinal range as in experiment 1). We found high among clonal variation formost measured variables, but the number of latitude-correlated traits waslimited. The only trait that correlated with latitude was the number of leavesper plant, which increased in clones from higher latitudes.Our results agree with the hypothesis of a latitude-correlated switch inlife-cycle strategy for this species. For northern clones this results in ashort life-cycle, with an early and high investment in tuber biomass, while forlow latitude clones the length of the life-cycle is prolonged, with a delayedreproduction and increased total plant biomass.