Friend or foe? A parasitic wasp shifts the cost/benefit ratio in a nursery pollination system impacting plant fitness

Abstract

Nursery pollination systems are species interactions where pollinators also act as fruit/seed herbivores of the plant partner. While the plants depend on associated insects for pollination, the insects depend on the plants' reproductive structures for larval development. The outcome of these interactions is thus placed on a gradient between mutualism and antagonism. Less specialized interactions may fluctuate along this gradient with the ecological context, where natural enemies can play an important role. We studied whether a natural enemy may impact the level of seed consumption of a nursery pollinator and how this in turn may influence individual plant fitness. We used the plant Silene latifolia, its herbivore Hadena bicruris, and its ectoparasitoid Bracon variator as a model plant-herbivore-natural enemy system.We investigated seed output, germination, survival, and flower production as proxies for individual plant fitness. We show that B. variator decreases the level of seed consumption by H. bicruris larvae which in turn increased seed output in S. latifolia plants, suggesting that parasitism by B. variator may act as a regulator in the system. However, our results also show that plant survival and flower production decrease with higher seed densities, and therefore, an increase in seed output may be less beneficial for plant fitness than estimated from seed output alone. Our study should add another layer to the complex discussion of whether parasitoids contribute to plant fitness, as we show that taking simple proxies such as seed output is insufficient to determine the net effect of multitrophic interactions. K E Y W O R D Scost/benefit ratio, host-parasitoid interaction, plant fitness, Silene-Hadena-Bracon system | 4221

The Effect of the Proportion of Adjacent Non-Crop Vegetation on Plant and Invertebrate Diversity in the Vineyards of the South Moravian Region

“…Plant species from the Caryophyllaceae family (Silene, Stellaria spp.) were the subject of several studies focused mostly on attraction for pollinators [54] or herbivore moths and their parasitoids [55,56]. In this study, the Caryophyllaceae found in vineyard inter-rows were Arenaria serpyllifolia L., Stellaria media L.…”

The role of intraspecific competition between plants in a nursery pollination system—Comments on Villacañas de Castro and Hoffmeister 2020

“…Our greatest reserve is toward figure 5b in the original paper (Villacañas de Castro & Hoffmeister, 2020) and the conclusions derived from it. We recognize that the authors make a good point of making a graph to compare the presence of density‐dependent effects on the probability of germination and survival of plants, but we claim that their choice of what to graph was erroneous for their main purpose.…”

“…Original dataset from Villacañas de Castro & Hoffmeister (2020) Dryad:doi.org/10.5061/dryad.rjdfn2z75.…”

“…We have read with great interest the article published by Villacañas de Castro and Hoffmeister titled Friend or foe? A parasitic wasp shifts the cost/benefit ratio in a nursery pollination system impacting plant fitness (Villacañas de Castro & Hoffmeister, 2020). Therein, the authors studied a tritrophic system composed of a plant, Silene latifolia , its pollinating seed predator, Hadena bicruris , and a parasitoid of the latter, Bracon variator .…”

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We present comments on an article published by Villacañas de Castro and Hoffmeister (Ecology and Evolution, 10, 4220;2020). The authors studied a tritrophic system composed of a plant, its pollinating seed predator, and a parasitoid of the latter.

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