Spatio‐temporal variation in fruit production and seed predation in a perennial herb influenced by habitat quality and population size

Abstract

Summary 1.In patchily distributed plant species, seed production is likely to be influenced both by local abiotic factors affecting plant size and conditions for fruit maturation, and by population characteristics affecting the intensity of interactions with mutualists and antagonists. However, the relative importance of these effects is poorly known. 2. We used multiple regression and path models to examine the importance of abiotic factors (sun exposure, soil depth) and population characteristics (size, density and connectivity) for variation in flower and fruit production and intensity of seed predation among 39 populations of the long-lived herb Vincetoxicum hirundinaria in three consecutive years. In addition, we manipulated water availability in a field experiment and recorded short-term and long-term effects on fruit output, and conducted a supplemental hand-pollination experiment. 3. Flower production varied little, while fruit initiation, fruit abortion and fruit predation varied considerably among years. Sun exposure and soil depth affected fruit production per plant indirectly and positively through their effects on flower number. Population density affected fruit production negatively through its effect on flower number. Both fruit initiation and the proportion of fruits attacked by the tephritid fly Euphranta connexa were related positively to population size. 4. The number of full-size fruits per plant was related positively to sun exposure and population size in two years each, and related negatively to population density in one year. However, because of seed predation, the number of intact mature fruits was related significantly to population characteristics in only one of three years. 5. The field experiments showed that both shortage of water and insufficient pollination may limit fruit set in V. hirundinaria . 6. Synthesis . These results demonstrate that the relative importance of local abiotic conditions and population characteristics may vary considerably along the chain of events from flower formation to intact fruit, and also among years. They further show that, at least in species with a naturally patchy distribution, connectivity may be relatively unimportant for variation in reproductive output compared to effects of habitat quality, population size and density.

Pollination system and the effect of inflorescence size on fruit set in the deceptive orchid Cephalanthera falcata

“…Similar to pollinators, there is evidence that florivores and seed predators are often attracted to larger floral displays, which provide greater resources in the larger ovules (Brody and Mitchell 1997;Adler and Bronstein 2004; but also see Walsh et al 2014). Consequently, florivores and seed predators can cause counter-selection for fewer flowers in opposition to the selection for more flowers to increase pollinator visits (Sletvold and Grindeland 2008;Ågren et al 2008). Further research is therefore required to determine whether larger inflorescences contribute to increased floral herbivory and seed predation in C. falcata, especially since the seed predator J. tokunagai was a common floral visitor at the sites under investigation.…”

Herbivory strongly influences among-population variation in reproductive output of Lythrum salicaria in its native range

“…Reproductive output commonly varies among plant populations, and differences in both abiotic conditions (Willson and Price 1980;Ågren 1988;De Frenne et al 2009;Toräng et al 2010) and intensity of biotic interactions (Schemske and Horvitz 1988;Ehrlén 1995;Morris et al 2007;Ågren et al 2008) may contribute to such variation. Determining the processes governing spatial variation in flower and seed production is important not only because of their influence on plant population dynamics and distributions, but also because determining these processes can lead to a greater understanding of among-population variation in selection regimes, and of interactions with pollinators and herbivores that depend on flowers or seeds as a resource.…”

Effect of rosette size, clonality and spatial distribution on the reproduction of Vriesea carinata (Bromeliaceae) in the Atlantic Forest of Paraná, southern Brazil

“…Bigger plants do not result in higher reproductive eff ort even when biomass was measured with infl orescences. Th e reproductive eff ort in V. carinata diff ers from what has been reported for other species, because fl ower production is frequently correlated with plant size, which usually increases with increased resource availability (Ågren et al 2008;Dauber et al 2010). In bromeliads, sexual reproduction tends to increase with an increase in plant size (Benzing 1981;Hietz et al 2002;Mondragón et al 2004;Mantovani & Iglesias 2009).…”