Nectar Production by InvasiveLantana camaraand EndemicL. peduncularisin the Galápagos Islands

Abstract

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. Lantana camara flowers had a higher nectar volume than L. peduncularis flowers at every elevation and higher total sugar content. However, nectar in L. peduncularis flowers was much more concentrated than in L. camara flowers 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 that of bagged flowers at sunrise, which was probably related to consumption of nectar by nocturnal Lepidoptera. Nectar removal by floral visitors had a pronounced effect on total amount of nectar secreted by L. camara flowers but sugar concentration did not vary significantly. Our results suggest that L. camara may compete with L. peduncularis for pollinators.

Fruit set and the diurnal pollinators of the invasive Lantana camara and the endemic Lantana peduncularis in the Galapagos Islands

“…In this context, L. camara attracted more pollinator species and individuals than L. peduncularis , which might be related to its colored flowers, one of the most important floral characteristics that are used by butterflies to find nectar (Lewis & Lipani ), and to a higher nectar content than that of L. peduncularis (Carrión‐Tacuri et al . ), which could influence the behavior of pollinators (Waser ).…”

“…Moreover, the presence of the invasive L. camara that has higher attractiveness (showy flowers and larger floral display), better rewards (more nectar; Carrión‐Tacuri et al . ) and shares pollinators with L. peduncularis could lead to competition for pollinators as they also share habitats. If this is the case, the inability of L. peduncularis to autonomously produce fruits could increase the impact of the invasive species in competing for pollinators (Brown et al .…”

“…In relation to the main pollinator of both species, U. galapagensis, the frequency of visits, as well as the inflorescence-and flower-visiting rates, were higher in L. camara than in L. peduncularis. In addition, U. galapagensis invested more time in visiting each flower of L. camara, probably owing to its higher nectar content (Carrión-Tacuri et al 2012). Similarly to other Lepidoptera, the endemic U. galapagensis was able to associate the color phase with the availability of reward (Gori 1983;Weiss 1995;1997), visiting mostly the yellow flowers of L. camara (99%), which have more nectar and a higher concentration of nectar than the old pink flowers (Carrión-Tacuri et al 2012).…”

“…However, this study analyzed only diurnal pollination and the highest nectar consumption by the pollinators of L. camara seems to occur during the night (Carrión-Tacuri et al 2012). The fact that L. camara attracted a wide spectrum of pollinators also might affect the pollination mechanism and reproductive success of other sympatric coflowering species that were originally pollinated by these agents.…”

“…However, they also show differences in floral features and display, which could result in differential attractiveness to visitors, leading to differences in pollinator attendance, as reported in other species (Berjano et al 2009). In this context, L. camara attracted more pollinator species and individuals than L. peduncularis, which might be related to its colored flowers, one of the most important floral characteristics that are used by butterflies to find nectar (Lewis & Lipani 1990), and to a higher nectar content than that of L. peduncularis (Carrión-Tacuri et al 2012), which could influence the behavior of pollinators (Waser 1983).…”