Geographic distribution and ecology of two species ofOrsillus(Hemiptera: Lygaeidae) associated with cones of native and introduced Cupressaceae in Europe and the Mediterranean Basin

Abstract

In the Mediterranean Basin, two species of true seed bugs in the genus Orsillus Dallas, O. maculatus Fieber and O. depressus Mulsant et Rey, share the exploitation of seed cones of Cupressaceae for feeding and reproduction and may carry spores of the pathogenic fungus Seiridium cardinale Sutton & Gibson, responsible for the cypress bark canker disease. We compared the life history of the two species. A total of 89 cone collections carried out in 10 Mediterranean countries confirmed that O. maculatus is most closely associated with Cupressus sempervirens L., although it may also infest some other Cupressus L. species and, more rarely, species of Chamaecyparis Spach. Orsillus depressus appears to be less host-specific, being capable of feeding and ovipositing on most of the native and exotic species of Juniperus L., Cupressus, and Chamaecyparis. On C. sempervirens, the abundance of each Orsillus species follows an inverted longitudinal gradient along the Mediterranean Basin, probably corresponding to the pathway of introduction of this tree species from its native eastern range towards western Europe. The dominance of O. maculatus progressively decreases from east to west, whereas O. depressus becomes dominant in the Iberian Peninsula. By contrast, O. depressus is the dominant seed bug on other Cupressaceae all over Europe and the Mediterranean Basin. In the area in which C. sempervirens has been introducted, both Orsillus species may live on the same tree, but morphological variability of both adults and nymphs often hinders accurate identification of the species. Based on frequency distribution, the relative length of the rostrum compared with that of the body seems to be a diagnostic character for specific identification of nymphs of the last two instars.

Oviposition Sites of the Cypress Seed Bug Orsillus maculatus and Response of the Egg Parasitoid Telenomus gr. Floridanus

“…Roques, unpublished observations). Therefore, the association cypress-seed bug-seed chalcid probably originated in the native range and then shifted to most of the introduction range of C. sempervirens in the Western Mediterranean (Roques, 1983;Carcreff et al, 1998;Rouault et al, 2005). The fourth component of the association, the egg parasitoid, has also been observed in the native range (Rouault et al, 2000), but due to the limited number of observations, we are unable to determine whether the system naturally involves the four components or if it corresponds to a secondary colonization from the introduction range of cypress.…”

Complex Insect–Pathogen Interactions in Tree Pandemics

“…The seed bug Orsillus maculatus feeds on cypress seeds and inhabits the cone throughout its development. It shows a perfect overlap with the range of its major host, Cupressus sempervirens , in the Mediterranean region (Rouault et al, 2005). The cypress seed bug may feed on the seeds from outside the cone, penetrating through the cone scales with the mouthparts (adult), or from inside (nymph).…”

Alien True Bugs of Europe (Insecta: Hemiptera: Heteroptera)

“…Regarding impact on individuals, field observations indicate competition, pathogen-transfer, predation, and herbivory, but all these cases need more thorough investigations. The case of transmitting spores of the pathogenic fungus Seiridium cardinale, responsible for cypress bark canker disease by Orsillus species, needs further study (Rouault et al 2005). Escaped polyphagous predatory biocontrol agents (Perillus, Orius, etc.)…”