Andalo, C. | bioRxiv Science

bioRxiv2026

Edge effect on the distribution of the Green Shield Bug Palomena prasina in hazelnut orchards, and the role of adjacent habitats in crop colonization.

Palomena prasina (L.) (Hemiptera: Pentatomidae), the green shield bug (GSB), is an important hazelnut pest in Southern Europe. Currently, its control focuses on insecticide spraying during the crop season. We hypothesised that, as for other pentatomid species, adjacent habitats strongly influence the population build-up in spring and, therefore, lead to edge effects in crop fields during the production season. This could allow for precision-targeted pest management strategies. This study examined the spatio-temporal dynamics of the GSB in spring and summer over two years. We investigated the plant preferences of GSBs in spring and the existence of edge effects on their distribution and on fruit damage in hazelnut orchards in summer. We also examined the relative contribution of adjacent habitats to GSB abundance in crops. Our results show that, following their emergence from overwintering in spring, GSB adults, and later on their offspring, are primarily found on wild host plants in natural habitats, particularly on Crataegus monogyna Jacquin, and Cornus sanguinea L.. In early summer, the older nymphs of the second generation colonise the hazelnut orchards, with populations and damage proportion displaying edge effects. We were unable to identify an adjacent habitat variable that significantly explains the abundance of GSB in the orchards, although both forest habitats and hazelnut orchards have an effect on GSB abundance. Based on these findings, we propose various IPM strategies for controlling P. prasina.

ecology↗

bioRxiv2025

Genomic tree scans identify loci underlying adaptive peaks in Antirrhinum

A key question in evolutionary biology is how barriers to gene flow operate and arise between populations, leading to speciation. Barriers are typically identified by comparing populations distinguished by phenotype, geographical location and/or environment. However, such prior classifications may bias recovery towards features obvious to the human eye, influencing mechanistic interpretations. Here we develop a method blind to prior classifications. We apply it to 18 Antirrhinum populations occupying habitats from coastal to alpine. By scanning the genome for regions with deeply rooted similar trees, we identify a single multi-locus partition, comprising less than 0.5% of the genome. It derives from eight genes, three newly identified here, which interact to generate complementary pollinator guides, likely corresponding to two adaptive peaks in a fitness landscape. Hybrid genotypes fall in a fitness valley, allowing the partition to be maintained through hybrid incompatibility and creating steep clines in allele frequency at a hybrid zone. Another partition derives from a single locus linked to a gene controlling plant height. The locus exhibits a shallow cline in allele frequency across an eco-geographic barrier and may be eco-adaptive. Our results suggest that two ancestral subspecies underwent extensive gene flow except at a few barrier loci, showing how both hybrid incompatibility and eco-adaptation can operate to maintain diversity.

evolutionary biology↗