Abstract
The effects of herbivorous insects on a plant population are not always well tolerated. This is especially true if the herbivorous actions are directed toward rare plant species. Salvia ceratophylloides Ard. is a rare endemism of southern Italy. Observations of the plants in situ revealed that many of them were under severe stress and did not produce seeds. Therefore, to find out which factors affect the reproductive activity as a whole, an observational study was carried out. We found bottom-up and top-down effects on plant health and reproduction associated with herbivorous action. Squamapion elongatum (Coleoptera, Curculionoidea, Apionidae), in all monitored sites, infested plants non-uniformly but was able to threaten the health condition, flowering, and seed production of sage by digging tunnels into the sage branches (bottom-up action), and then secondarily by seed feeder Systole salvia Zerova (Hymenoptera, Eurytomidae) predating sage seeds (top-down action). Mainly, chalcid parasitoid wasps such as Trichomalus spp. (Hymenoptera, Pteromalidae), as well as Eupelmus vesicularis and E. muellneri (Hymenoptera, Eupelmidae), limited the herbivorous S. elongatum population and the seed herbivore S. salviae emerged with its parasitoid Ormyrus diffinis (Hymenoptera, Ormyridae). Overall, this study showed how ecological interactions among herbivores, their host, and their natural enemies act on this sage species in all sites investigated. Among the herbivores, mainly S. elongatum affected this rare sage species, which should be taken into consideration, especially in the formulation of biological control solutions and for improving operating practice aimed at reproducing the species. This study provides the molecular characterization of the herbivorous species involved, in order to support future projects to evaluate the intra- and interspecific genetic variability of insects, their evolutionary relationships, and phylogeny studies.
Highlights
IntroductionIntroduction nal affiliationsThe loss of both animal and plant biodiversity is basically related to several key factors, some of which are related to human activity (fragmentation and loss of habitat, pollution, etc.) and others related to climatic events and geological processes [1,2,3]
Introduction nal affiliationsThe loss of both animal and plant biodiversity is basically related to several key factors, some of which are related to human activity and others related to climatic events and geological processes [1,2,3]
The infested plants were positively related to the reproductive phase (i.e., reproductive plants (RPs)) and not to the vegetative phase (i.e., growing plants (GPs)) or sites (Table 3)
Summary
Introduction nal affiliationsThe loss of both animal and plant biodiversity is basically related to several key factors, some of which are related to human activity (fragmentation and loss of habitat, pollution, etc.) and others related to climatic events and geological processes [1,2,3]. The processes that determine the recovery of biodiversity are reversible and are linked to the reduction of pollutants and an increase in habitat favorable to the species [4]. To achieve this aim, it is often essential to know which factors at the local scale contribute to regulating the relationships among plants, the environment, and herbivores [5,6]. Reproductive strategies, are essential for determining the quantity and quality of offspring [11,12], which can be conditioned by the action of some herbivores or pathogens limiting the fitness of a species [13,14,15]. The detrimental action by herbivores, when occurring in rare species on a small number of individuals/populations, directly affects both suitability and genetic composition, influencing the population dynamics and long-term persistence [16]
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