Unpaved roads disrupt the effect of herbivores and pollinators on the reproduction of a dominant shrub

Abstract

Anthropogenic linear developments, such as trails and firebreaks, also called soft linear developments (SLD), can influence animal behavior, altering the ecological interactions in which animals are involved. For example, SLD can affect the behavior of pollinators and herbivores, but little is known about the combined effect of these three elements on plant reproduction.We evaluated the combined effect of SLD, insect pollinators and herbivores (ungulates) on three reproductive output variables (fruit set, seed set, and seed mass) of a Mediterranean shrub (Halimium halimifolium). We considered two different habitats (SLD verges vs. adjacent scrublands), two scenarios of herbivory (with and without ungulates), and three scenarios of pollinator activity (without pollinators, with manual pollination and with natural pollination).SLD had contrasting effects on H. halimifolium reproduction. In the absence of herbivores, overall fruit set was lower in the verges of SLD than in adjacent scrublands, probably due to lower flower pollination rates. Where herbivores were present, overall fruit set was similar between habitats, because ungulate browsing was lower in SLD verges than in adjacent scrublands. The quantity and weight of seeds per fruit was similar in both habitats, probably because all fertilized flowers received similar amounts of pollen.SLD can alter the interaction among pollinators, herbivores and plants, leading to changes in the reproductive performance of the latter. These changes can have strong negative impacts on endangered plants that rely on fruit and seed production to persist. However, SLD verges could be safe places for plants particularly sensitive to herbivory by ungulates. ZusammenfassungAnthropogene lineare Landschaftselemente wie Wanderwege oder Feuerschneisen können das Verhalten von Tieren beeinflussen und damit die ökologischen Interaktionen, an denen die Arten beteiligt sind, verändern. Diese grünen linearen Strukturen (GLS) können beispielsweise das Verhalten von Bestäubern und Herbivoren beeinflussen, aber wenig ist über den gemeinsamen Effekt dieser drei Elemente auf die Reproduktion von Pflanzen bekannt.

Effects of Road Dust on the Pollination and Reproduction of Wildflowers

“…This consistent result is highly improbable if dust exposure had no effect on pollen receipt. Furthermore, the fact that we observed the same pattern with experimental hand dusting implicates dust, rather than other effects of roads or features correlated with roads (e.g., Geerts and Pauw 2011;Suárez-Esteban et al 2014), as a major (perhaps sole) cause of reduced pollen receipt.…”

Exploring the Genetic Diversity of Wild Cranberry Populations in the Upper Midwestern United States

“…For example, the declining number and quality of pollinators in an area due to human activity, such as a nearby construction or a major road disrupting an area, has had an effect in other plant species, such as lower fruit set in Halimium halimifolium (L.) Willk. (Suárez-Esteban et al, 2014). Previous studies that found low levels of genetic variation in wild populations of cranberry were surprised by their low diversity results (Stewart and Excoffier, 1996;Bruederle et al, 1996).…”

Are metapopulation species drivers of metacommunity structure in sandstone outcrop communities?

“…Species richness not exhibiting a relationship with patch area contradicts the long‐standing species–area hypothesis (Arrhenius, 1921; Gleason, 1922). In addition, previous studies have found differing effects of roads on both species' dispersal as well as gene flow (Taylor et al, 2012; Suárez‐Esteban et al, 2013, 2014; Lemke et al, 2019). We found that the area‐dependent metapopulation extinction probability (avg x values) was highest in large, regularly shaped sites, highlighting how area availability in patches may be crucial for metapopulation persistence.…”