Landscape Simplification Increases Bactrocera Oleae Abundance In Olive Groves: Populations Dynamics In Different Land Uses.

Bactrocera oleae is the main pest in olive groves and its management requires a sustainable perspective to reduce the use of chemical products. Landscape context is being considered as an important driver of pest reduction but results on B. oleae show inconsistency to date. Most of landscape-pest control studies focus on the dynamics of the pests within the focal crop, ignoring these dynamics in other land uses. Here we present a study in which we analyze the seasonal population dynamics of the olive pest B. oleae in the most important land uses of a typical olive landscape in Portugal. We found that B. oleae is present in all the land uses and the dynamics are very similar to those in the olive groves. However, the presence of these land uses in the landscape did not display any increase of B.oleae abundance within the olives groves. In contrast, a landscape mainly composed by olive groves increased the abundance of this pest. Importantly, more diverse landscapes surrounding olive groves reduce the abundance of the olive fly. Based on these findings, we can conclude that B. oleae is present in all the land uses of the studied landscape but that this presence does not imply an increase of B. oleae in olive groves. Indeed, other land uses can promote landscape diversification which is a driver of the reduction of B. oleae populations in olive groves. We thus encourage olive stakeholders to increase landscape diversification around their farms by promoting/restoring other crops/habitats.

Among-individual and within-individual variation in seasonal migration covaries with subsequent reproductive success in a partially migratory bird

Within-individual and among-individual variation in expression of key environmentally sensitive traits, and associated variation in fitness components occurring within and between years, determine the extents of phenotypic plasticity and selection and shape population responses to changing environments. Reversible seasonal migration is one key trait that directly mediates spatial escape from seasonally deteriorating environments, causing spatio-seasonal population dynamics. Yet, within-individual and among-individual variation in seasonal migration versus residence, and dynamic associations with subsequent reproductive success, have not been fully quantified. We used novel capture-mark-recapture mixture models to assign individual European shags ( Phalacrocorax aristotelis ) to ‘resident’, ‘early migrant’, or ‘late migrant’ strategies in two consecutive years, using year-round local resightings. We demonstrate substantial among-individual variation in strategy within years, and directional within-individual change between years. Furthermore, subsequent reproductive success varied substantially among strategies, and relationships differed between years; residents and late migrants had highest success in the 2 years, respectively, matching the years in which these strategies were most frequently expressed. These results imply that migratory strategies can experience fluctuating reproductive selection, and that flexible expression of migration can be partially aligned with reproductive outcomes. Plastic seasonal migration could then potentially contribute to adaptive population responses to currently changing forms of environmental seasonality.

Seasonal Population Dynamics, Sampling Distribution, and Fixed-Precision Sequential Sampling of Spectrobates ceratoniae (Lepidoptera: Pyralidae) in Pomegranate Orchards

The carob moth, Spectrobates ceratoniae Zeller, is the most destructive pest of pomegranate groves of Iran. Seasonal population dynamics of the pest was studied in pomegranate orchards of Sirvan, Ilam province, in southwestern Iran for 2 yr (2016/2017). Sampling distribution of the pest larvae on pomegranate fruits was evaluated by Taylor’s power law and Iwao’s patchiness index, and a fixed-precision sequential sampling plan of the pest was developed using Green’s model. The adult population peaked in June. The activity period of the larvae was observed from June to October and peaked in October. Sampling distribution of the larvae on pomegranate fruits was random. Estimated optimum sample sizes ranged from 1 to 44 and 1 to 16 fruits at precision levels of 0.25 and 0.1, respectively.