Correlations among traits associated with herbivore resistance and pollination: implications for pollination and nectar robbing in a distylous plant

Abstract

Plants interact simultaneously with a diversity of visitors, including herbivores and pollinators. Correlations among traits associated with herbivory and pollination may constrain the degree to which plants can evolve in response to any one interactor. Using the distylous plant, Gelsemium sempervirens, we tested the hypothesis that traits typically associated with pollination (distyly) and herbivore resistance (secondary compounds) were phenotypically correlated and examined how these traits influenced plant interactions with floral visitors. The flowers of G. sempervirens are visited by pollinators and a nectar robber, and the leaves and flowers express gelsemine, an alkaloid that is deterrent and sometimes toxic to visitors. Using an observational approach across five populations, we found the thrum floral morph (short‐styled) expressed more leaf gelsemine than the pin morph (long‐styled). Leaf gelsemine concentrations were positively correlated with flower gelsemine; however, there were no correlations between gelsemine and other floral morphological traits. Trait expression influenced pollination more so than robbing. Thrums received two times less pollen than pins. Moreover, across both morphs, pollen receipt was lower in plants that expressed higher levels of leaf gelsemine in two sites. These results imply that traits associated with pollination and herbivore resistance may not be independent.

Diversification through multitrait evolution in a coevolving interaction

“…Plant species often have pollinators whose body parts closely complement the flowers they visit, resulting in effective pollination (37)(38)(39)(40). Evolution of the presence, size, or shape of some characters can alter pollination efficacy by creating mismatches in traits (41)(42)(43)(44). The results for woodland stars and Greya moths, however, indicate that there is a wide range of trait combinations that can sustain mutualisms in codiverging lineages.…”

Nectar alkaloids decrease pollination and female reproduction in a native plant

“…Gelsemium contains the alkaloid gelsemine in leaves, Xowers and nectar (Adler and Irwin 2005;Irwin and Adler 2006); this alkaloid is highly toxic to mammals (Kingsbury 1964). Gelsemium nectar can cause bee poisoning (Eckert 1946;Hardin and Arena 1969), and young worker honey bees develop abnormally when feeding on Gelsemium nectar (Burnside and Vansell 1936).…”

“…Gelsemium blooms from early March into late April, producing up to several hundred yellow, tubular Xowers per plant. Each Xower has Wve petal lobes; individual Xowers bloom for 3-5 days and produce nectar at a rate of 1.1 l per 48 h with sugar concentration of approximately 48% (Irwin and Adler 2006). Fruits are dehiscent capsules that mature in the fall.…”

Nectar thieves influence reproductive fitness by altering behaviour of nectar robbers and legitimate pollinators in Corydalis ambigua (Fumariaceae)

“…One of the factors that has prevented nectar robbing from being appreciated as an important phenomenon in plant evolutionary ecology, despite its ubiquity and taxonomic breadth (Irwin, Brody & Waser 2001;Ehrl en 2002), is the lack of generality that researchers have found in the outcomes of plantpollinator-robber interactions (Morris 1996;Maloof & Inouye 2000;Agrawal 2001;Irwin & Adler 2006;Irwin 2009;Zhang et al 2009b). Interactions among a plant species, its pollinators and its larcenists are embedded in a larger web of interactions.…”