Nectar Production by Invasive Lantana camara and Endemic L. peduncularis in the Galápagos Islands

Measurements of nectar volume and sugar concentration along two elevational gradients, in flower exclusion experiments, and over a diurnal cycle of nectar production, were compared for invasive Lantana camara and endemic Lantana peduncularis in the Galápagos Islands during the dry season. Both species show the same pollination syndrome and are pollinated by Lepidoptera. L. camara flowers had a higher nectar volume than L. peduncularis at every elevation and higher total sugar content. However, nectar in L. peduncularis flowers was much more concentrated than in L. camara at lower elevations. The differences in nectar production between Lantana species seemed to be intrinsic and related to contrasting strategies to cope with drought. Nectar volume of unbagged flowers of L. camara was lower than bagged flowers at sunrise, which was probably related to the consumption of nectar by nocturnal Lepidoptera. Nectar removal by floral visitors had a pronounced effect on the total amount of nectar secreted by L. camara flowers, while the sugar concentration did not vary significantly. Our results suggest that L. camara may compete with L. peduncularis for pollinators

Divergence between phenotypic and genetic variation within populations of a common herb across Europe

Analyzing the pattern and causes of phenotypic and genetic variation within and among populations might help to understand life history variability in plants, and to predict their responses to changing environmental conditions. Here we compare phenotypic variation and genetic diversity of the widespread herb Plantago coronopus across Europe, and evaluate their relationship with environmental and geographical factors. Genetic diversity was estimated in 18 populations from molecular markers with AFLP. Phenotypic variation was measured in a subset of 11 populations on six life history traits (plant size, plant growth, fecundity, seed mass, mucilage production and ratio between two functionally different seed morphs). To account for ecological and geographical correlates, we estimated variability in local temperature, precipitation and intraspecific competition, and accounted for the central vs. peripheral position of populations. Phenotypic variation and genetic diversity were not significantly correlated within populations throughout the species' range. Phenotypic variation was positively linked to precipitation variability, whereas genetic diversity was correlated with the position of populations, suggesting that both types of variation are shaped by different processes. Precipitation seems to have acted as a selective agent for variation within populations in most life history traits, whereas the species' post-glacial demographic history has likely reduced genetic diversity in northern peripheral populations with respect to central ones. The positive association between precipitation variability and phenotypic variation also suggests that plant populations may have higher adaptive potential in ecologically variable rather than stable environments. Our study offers an additional criterion when predicting the future performance of species under environmental changes. © 2014 Villellas et al. - Copyright by the Ecological Society of AmericaThis study was funded by the Spanish Ministry of Science and Innovation by means of National Projects to M.B.G. (CGL2006-08507; CGL2010-21642) and A.T. (CGL2009-08713), and a FPU scholarship to J.V. We are grateful to A. Adsuar, A. Barcos, R. Braza, R. Castillo, M.L. Dehesa, R. Corrià, F. Domínguez, R. Forrest, M.C. García, E. López, J. Martínez, E. Morán, C. Niklasson, F. Ojeda, J.M. Olesen, S. Palacio, I. Pardo, A. Pérez, A. Primilla, C. Pérez, P. Sánchez, A. Taboada, M. Talavera and A. Vale for their valuable help in field and laboratory work through years. We thank R. Braza, V. Simón, J. Thompson and A. Traveset for plant material for genetic analyses, R. Braza for phenotypic data from population F and BN, and M. Pazos for her assessment in statistical analyses. X. Picó, J. Arroyo, T. Iriondo, P. Vargas and three anonymous referees provided very helpful comments on the manuscript.Peer Reviewe