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- A novel morphological phenotype does not ensure reduced biotic resistance on an oceanic islandPublication . Ferrante, Marco; Nunes, Rui; Lamelas-López, Lucas; Lövei, Gabor L.; Borges, Paulo A. V.Biotic resistance by the local community is a prominent theory seeking to explain invasion success or failure. Oceanic island communities might be prone to invasions because of their assumed low biotic resistance, due to low species richness and ecological naivety towards invaders. Biotic resistance, however, has rarely been quantified. We attempted such quantification on Terceira Island (Azores, Portugal) using the sentinel prey method. Vanessa virginiensis, a widely distributed Nearctic butterfly, has not been recorded on Terceira, and their caterpillars have characteristic green–black stripes that make it dissimilar to other Azorean caterpillars. We examined whether predation rate (PR) on plasticine caterpillars mimicking the unfamiliar V. virginiensis pattern were lower than on familiar green ones. We exposed a total of 4479 caterpillars in native forests and five non-native habitats, the agroecosystems orchards, vineyards, low and high elevation maize fields, and intensively managed pastures. Overall PR was higher on caterpillars with the unfamiliar than with the familiar pattern (6.4%d⁻¹ vs. 3.7%d⁻¹). Invertebrate PR was also significantly higher on the unfamiliar than on the familiar pattern in the native forest (5.9%d⁻¹ vs. 1.0%d⁻¹), as well as vertebrate PR in orchards (4.8%d⁻¹ vs. 2.3%d⁻¹) and low elevation maize fields (7.4%d⁻¹ vs. 2.2%d⁻¹). Our results suggest the existence of biotic resistance even on a species-poor, remote island, and that a novel morphological phenotype in itself does not guarantee reduced predation pressure.
- Gains and losses in ecosystem services and disservices after converting native forest to agricultural land on an oceanic islandPublication . Ferrante, Marco; Lövei, Gábor L.; Nunes, Rui; Monjardino, Paulo; Lamelas-López, Lucas; Möller, Daniella M.; Soares, António O.; Borges, Paulo A. V.Habitat conversion to agricultural land is one of the main threats to terrestrial biodiversity and can affect ecosystem processes and cause changes in ecosystem services (ESs) and disservices (EDs). Yet, studies often rely only on the abundance and diversity of the service providers; the effects on ecological processes of habitat conversion are rarely directly monitored. In this study, we used the sentinel approach to evaluate how habitat conversion from native forest to agricultural land affected ESs and EDs on an oceanic island. We quantified herbivory on lettuce plants, invertebrate and vertebrate predation rates on artificial caterpillars, pollination on strawberry plants, seed predation on wheat and mustard seeds, and leaf decomposition rates in native forests, maize fields and pastures on Terceira Island, Azores (Portugal). Herbivory, invertebrate predation rates, and pollination service were not significantly different between habitats. Vertebrate predation rates in native forests (mean 6.1% d⁻¹) were significantly higher than that in pastures (0.3% d⁻¹), or high-elevation maize fields (0.5% d⁻¹), and marginally higher than in low-elevation maize fields (2.2% d⁻¹). Overall seed predation after 48 h was significantly higher on wheat (mean 16.8%) than mustard seeds (5.6%). High-elevation maize fields also had higher seed predation (27.8%) than low-elevation ones (0.6%) or pastures (3.6%), but did not differ from the native forest (12.9%). Decomposition after 90 days was highest in pastures (78.4% and 45.9%, for tea and rooibos, respectively); although no significant differences between habitats were detected, except for low-elevation maize fields (64.4% and 33.6%). Conversion from native forest to cultivated land did not cause a clear decrease in the intensity of the studied ESs/EDs except for vertebrate predation. Using direct monitoring tools to simultaneously and consistently quantify multiple ecological processes is not only possible but needed, as ecological processes can respond differently to landscape changes.