Host plant selection and differential survival on two Aristolochia L. species in an insular population of Zerynthia cassandra
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Understanding host plant preference and the relative quality of resource provided by co-occurring host plants is a key step to predict butterfly species abundance and responses to environmental changes, and, consequently, to plan management measures. Zerynthia cassandra is an Italian endemic species strongly dependent on the availability of its host plants, Aristolochia rotunda and Aristolochia lutea. The insular population occurring on Elba island (Tuscan Archipelago) is highly threatened, because of limited host plant distribution, small population size and apparent lack of gene flow with the mainland. In 2017, we carried out field surveys and rearing experiments to (i) identify the characteristics of the host plants (vegetative status) and the site characteristics (aspect, irradiation, distance from other patches) correlated with the number of eggs occurring on individual plants, (ii) compare larval growth, food-conversions rate and larval and adult survivorship on the two host plants species. Egg occurrence depends on patch irradiation, the number of leaves and flowers occurring on individual plants and the occurrence of nearby patches. These findings allowed to identify the optimal Aristolochia patch features for egg laying and development. Laboratory rearing success was higher than 50% and although plant species did not show a significant effect on oviposition, we found that larval and adult survival was higher on A. rotunda. Our results suggest habitat management aimed at increasing resource availability for Z. cassandra and possible ex-situ conservation actions aimed at recovering the population in case of potential catastrophic events.
KeywordsZerynthia cassandra Aristolochia Egg laying Laboratory rearing Elba island
We thank Umberto Mazzantini, Dr. Brunella Perito, Dr. Bruno Foggi for helping in collecting the data. The study has been conducted in collaboration with the Tuscan Archipelago National Park.
Funds were provided to LD by the University of Florence and by the Ministero dell’Ambiente e della Tutela del Territorio e del Mare, through the project “Insetti di valore conservazionistico: presenza, status e interazioni con specie di fitopatogeni”, Progetto di sistema of Italian National Parks, “Biodiversità” directive.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
This article does not contain any studies with human participants performed by any of the authors. Any applicable international, national, and/or institutional guidelines for the care and use of animals were followed. Specimens were collected and reared in the laboratory after permission from the Italian Ministero dell’Ambiente e della Tutela del Territorio e del Mare (Prot. 0012493/PNM 24/06/2015).
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