Florivory affects pollinator visitation and female fitness in Nemophila menziesii

Abstract

While herbivory has traditionally been studied as damage to leaves, florivory - herbivory to flowers prior to seed set - can also have large effects on plant fitness. Florivory can decrease fitness directly, either through the destruction of gametes or through alterations to plant physiology during fruit set, and can also change the appearance of a flower, deterring pollinators and reducing seed set. In order to distinguish between these hypotheses, it is necessary to both damage flowers and add pollen in excess to study the effects of damage on pollen limitation. Very few studies have used this technique over the lifetime of a plant. Here I describe a series of experiments showing the effects of natural and artificial damage on reproductive success in the annual plant Nemophila menziesii (Hydrophyllaceae, sensu lato). I show that natural and artificial petal damage decreased radial symmetry relative to controls and that both types of damage deterred pollinator activity. Both naturally damaged flowers and artificially damaged flowers in the field set fewer fruit or seed relative to undamaged control flowers. Finally, in an experiment crossing artificial petal damage with pollen addition, petal damage alone over the lifetime of this plant decreased female fitness, but only after a threshold of damage was reached. The fitness effect appeared to be direct because there was no detectable effect of pollen addition on the relationship between florivory and fitness. This result implies that both damaged and undamaged plants show similar amounts of pollen limitation and suggests that pollinator-mediated effects contributed little to the negative effects of florivory on female fitness. Florivores may thus be an under-appreciated agent of selection in certain plants, although more experimental manipulation of florivory is needed to determine if it is important over a range of taxa.

Effects of Florivory on the Pollination of Flowers: An Experimental Field Study with a Perennial Plant

“…This study revealed that pollinators were less likely to visit and pollinate flowers with missing parts (especially the lower lip), resulting in lower fruit and seed sets. Both naturally and artificially damaged flowers of Nemophila menziesii receive fewer visits from pollinators and set less fruit and seed than do undamaged flowers (McCall 2008).…”

Escape from floral herbivory by early flowering in Arabidopsis halleri subsp. gemmifera

“…First, floral herbivory affects the abundance and appearance of flowers, and may alter patterns of pollinator attraction and pollen movements Leavitt and Robertson 2006;Penet et al 2009). Second, floral herbivory may directly reduce the availability of reproductive organs that would otherwise produce mature seeds (McCall 2008). Finally, temporal changes in the intensity of floral herbivory have been observed (Evans et al 1989;EnglishLoeb and Karban 1992;Bishop and Schemske 1998;Pilson 2000;Mahoro 2002;Juenger et al 2005;Tarayre et al 2007;Oguro and Sakai 2009), and this can serve as a source of selection on flowering time to avoid floral herbivory (Elzinga et al 2007).…”

Petuniaflowers solve the defence/apparency dilemma of pollinator attraction by deploying complex floral blends

“…But, they can also cause collateral damage by altering species interactions, such as plant–pollinator interactions when florivores reduce flower numbers or size (Lohman et al . ; see Appendix S1 in Supporting Information), or more directly by damaging petals, which alters floral shape and size (McCall ; Sober et al . ), or simply by being present on a flower (Lohman et al .…”