The Afrotropical breeding grounds of the Palearctic-African migratory painted lady butterflies (Vanessa cardui)

Migratory insects are key players in ecosystem functioning and services, but their spatiotemporal distributions are typically poorly known. Ecological niche modeling (ENM) may be used to predict species seasonal distributions, but the resulting hypotheses should eventually be validated by field data. The painted lady butterfly (Vanessa cardui) performs multigenerational migrations between Europe and Africa and has become a model species for insect movement ecology. While the annual migration cycle of this species is well understood for Europe and northernmost Africa, it is still unknown where most individuals spend the winter. Through ENM, we previously predicted suitable breeding grounds in the subhumid regions near the tropics between November and February. In this work, we assess the suitability of these predictions through i) extensive field surveys and ii) two-year monitoring in six countries: a large-scale monitoring scheme to study butterfly migration in Africa. We document new breeding locations, year-round phenological information, and hostplant use. Field observations were nearly always predicted with high probability by the previous ENM, and monitoring demonstrated the influence of the precipitation seasonality regime on migratory phenology. Using the updated dataset, we built a refined ENM for the Palearctic-African range of V. cardui. We confirm the relevance of the Afrotropical region and document the missing natural history pieces of the longest migratory cycle described in butterflies.This work was funded by the National Geographic Society (grant WW1-300R-18); by the British Ecological Society (grant LRB16/1015); by the Research and Conservation Projects of the Fundació Barcelona Zoo; by the grant PID2020-117739GA-I00/MCIN/AEI/10.13039/501100011033 of the Spanish Ministry of Science and Innovation and the Spanish State Research Agency to G.T.; by the grant LINKA20399 from the Spanish National Research Council iLink program to G.T., C.P.B., N.E.P., and R.V.; by fellowship FPU19/01593 of the program Formación de Profesorado Universitario (FPU) to A.G.-B.; by the Turkana Basin Institute, National Geographic Society, and Whitley Fund for Nature to D.J.M.; and by grant 2018-00738 of the New Frontiers in Research Fund (Government of Canada) to G.T. and C.P.B.Significance Abstract Results Field Surveys, Larval Hostplants, and Field-Based Model Validation Monitoring Results and Population Dynamics across Regions A Refined Model for the Afrotropical Region Discussion The Afrotropical Breeding Grounds of V. cardui: Multiple Generations Shift South Toward the Tropics Diversity and Phenology of Larval Hostplants in the Afrotropics The Ecological Relevance of Delimiting Spatiotemporal Distributions in Migratory Insects Conclusion Methods December-January Field Surveys and Year-Round Monitoring Spatiotemporal Ecological Niche Modeling Data, Materials, and Software Availability Acknowledgments Supporting Information Reference

Supporting Information for The Afrotropical breeding grounds of the Palearctic-African migratory Painted Lady butterflies (Vanessa cardui)

Supporting Information includes: Supporting Methods.-- Supporting Results.-- Figures S1 to S7.-- Tables S1, S2.-- SI ReferencesCopyright © 2023 the Author(s). Published by PNAS. This article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND).Peer reviewe

Micro-habitat shifts by butterflies foster conservation strategies to preserve pollinator diversity in a warming Mediterranean climate

The Butterfly Monitoring Scheme based on linear transects conducted by citizen scientists has become a fundamental indicator for understanding the impact of climate change on butterfly populations. A key finding is the fast poleward expansion of butterfly distributions in Europe, coupled with slower population declines in southern regions. Given that the Mediterranean region is a climate change hotspot, understanding the largely unknown mechanisms employed by butterflies to cope with increasing aridity is crucial for developing data-driven conservation strategies. To address this issue, we developed a monitoring approach based on 90 transects fully covering areas of 50 m × 50 m squares instead of linear paths. This enabled us to explore the fine-scale dynamics of 80 butterfly species and their association with vegetational units in the Mediterranean hills (∼800 m a.s.l. as maximum altitude) of the MAB UNESCO Reserve of Monte Peglia (Central Italy). We sampled the transects from April to October 2022 (the locally hottest summer of the last decade) and documented three main patterns: 1) butterfly richness and abundance correlate with environmental features and these relationships vary across seasons. Richer sites consisted of some 30 % of woodland and were those closer to water, mostly during summer (area-based analysis). 2) Environmental preferences vary with species traits. Specialist species and those adapted to colder climates and narrower temperature ranges were more abundant in higher altitudes sites, closer to water and with wider woodland coverage (fourth-quadrant analysis). 3) Although most species preferred meadows, when temperature increases, they increased their abundance in sites with wider tree coverage, closer to streams, and at higher altitude (species-based analysis). These dynamics demonstrate that butterflies opportunistically move to cooler micro-habitats to buffer elevated temperatures. This phenomenon potentially involves most of the community since the species showing significant effects encompass >80 % of the observed individuals. Our analysis introduces new dimensions to the niche of Mediterranean butterflies, highlighting the significance of shady micro-habitats, altitudinal ranges, and water streams. These factors are likely to become increasingly critical with rising aridity levels. By combining our findings with existing literature data, we have provided a protocol aimed at preserving Mediterranean butterflies within the resist-accept-direct framework

A sunny spot: habitat management through vegetation cuts increases oviposition in abandoned fields in an endemic Mediterranean butterfly

The abandonment of agricultural land and the afforestation of grassland habitats represent major threats for butterflies in European and Mediterranean areas. A crucial goal for Lepidoptera conservation is to maintain and/or restore habitat quality by targeted management. Nevertheless, there are few experimental studies allowing to derive data-driven strategies to protect butterflies of open grasslands in the Mediterranean region. We developed a habitat management strategy for the conservation of the Italian endemic butterfly Zerynthia cassandra by adopting a three-step procedure: (i) characterising which environmental and host plant features influence oviposition on plants; (ii) identifying and testing the effect of a data-driven habitat management intervention; (iii) understanding which micro-habitat features promote Z. cassandra oviposition in restored places to optimise the intervention. Both patch (areas of 1 m radius hosting Aristolochia shoots) and plant features affect oviposition, with the strongest positive effects showed by high irradiation of the patch and plant quality (high number of flowers and leaves). Accordingly, the management consisted in vegetation cuts to increase irradiation, and 2 years of monitoring demonstrated that this procedure significantly increased oviposition (average increase of about 2 eggs per plant) and larval presence. Micro-habitat sampling demonstrated that the maximum oviposition differed between vegetation structures, highlighting the importance of a local fine-tuning before the intervention. We provided a data-driven, effective, and sustainable management strategy to increase habitat suitability and oviposition for an endemic and endangered Mediterranean butterfly. Our framework can drive management strategies for other species with similar ecological requirements and subjected to similar threats