Serotinous cones of <i>Cupressus sempervirens</i> provide viable seeds 
in spite of high seed predation

Battisti, Andrea; Cantini, Raffaella; Rouault, Gaëlle; Roques, Alain

doi:10.1051/forest:2003073

Cited by 13 publications

(10 citation statements)

References 16 publications

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“…Most other seed chalcids exploiting Pinaceae also emerge from seeds fallen to the ground, however on Cupressaceae, emergence of Megastigmus spp. occurs before seed release, and larvae can remain in diapause in seeds within unopened serotinous cones still hanging on the tree (Battisti et al 2003). Except for M. spermotrophus and Douglas-fir, the relationships between ovule development and seed chalcids are poorly understood.…”

Section: Introductionmentioning

confidence: 99%

Oviposition strategies of conifer seed chalcids in relation to host phenology

Rouault

Turgeon

Candau

et al. 2004

Naturwissenschaften

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Insects are considered the most important predators of seed cones, the female reproductive structures of conifers, prior to seed dispersal. Slightly more than 100 genera of insects are known to parasitize conifer seed cones. The most diverse (i.e., number of species) of these genera is Megastigmus (Hymenoptera: Torymidae), which comprises many important seed pests of native and exotic conifers. Seed chalcids, Megastigmus spp., lay eggs inside the developing ovules of host conifers and, until recently, oviposition was believed to occur only in fertilized ovules. Ovule development begins just after pollination, but stops if cells are not fertilized. The morphological stage of cone development at the time of oviposition by seed chalcids has been established for many species; however, knowledge of ovule development at that time has been documented for only one species, M. spermotrophus. Megastigmus spermotrophus oviposits in Douglas-fir ovules after pollination but before fertilization. Unlike the unfertilized ovules, those containing a M. spermotrophus larva continue to develop, whether fertilized or not, stressing the need to broaden our understanding of the insect-plant interactions for this entire genus. To achieve this task, we reviewed the scientific literature and assembled information pertaining to the timing of oviposition and to the pollination and fertilization periods of their respective host(s). More specifically, we were searching for circumstantial evidence that other species of Megastigmus associated with conifers could behave (i.e., oviposit before ovule fertilization) and impact on female gametophyte (i.e., prevent abortion) like M. spermotrophus. The evidence from our compilation suggests that seed chalcids infesting Pinaceae may also oviposit before ovule fertilization, just like M. spermotrophus, whereas those infesting Cupressaceae seemingly oviposit after ovule fertilization. Based on this evidence, we hypothesize that all species of Megastigmus associated with Pinaceae can oviposit in unfertilized ovules, whereas those exploiting Cupressaceae cannot, and thus oviposit only in already fully developed fertilized seeds. Furthermore, we predict that the presence of a larva in unfertilized ovules of all Pinaceae will influence the development of the female gametophyte by preventing its abortion. This influence on the Pinaceae can be interpreted as an ability to parasitize any of the potential seeds present in a seed cone, and as such represents a much more efficient oviposition strategy than searching and locating only fertilized seeds. Concomitantly, this ability has likely led to an overestimation of the impact of the species of seed chalcid infesting Pinaceae on seed production.

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Section: Introductionmentioning

confidence: 99%

Oviposition strategies of conifer seed chalcids in relation to host phenology

Rouault

Turgeon

Candau

et al. 2004

Naturwissenschaften

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“…This study was conducted in a plantation of C. sempervirens in Italy, where a large pop- Table 1. ulation of O. maculatus was previously recorded (Battisti et al 2003 Each sample consisted of a random collection of 30 mature, 3-year-old cones and 30 overmature, 4-year-old cones. Sampled cones were stored at 5°C until analysis, which was completed within 10 days of the date of collection.…”

Section: Life History Of O Maculatus Under Field Conditionsmentioning

confidence: 99%

“…Under laboratory conditions, five developmental instars have been observed for the nymphs of O. maculatus reared on C. sempervirens; the overall development from egg to adult takes approximately 61 days, and the species is considered multivoltine (Guido et al 1995;Battisti et al 1997;Rouault 2002). In the field, O. maculatus oviposited on cypress cones preferentially in the emergence holes of a cypress seed chalcid, Megastigmus wachtli Seitner (Hymenoptera: Torymidae), or on the inner side of partly opened cone scales (Guido et al 1995;Battisti et al 1997Battisti et al , 2003Rouault 2002). Chalcid holes appeared to protect bug eggs from parasitoid attacks and mechanical injuries (Rouault et al 2000).…”

Section: Introductionmentioning

confidence: 99%

“…However, several Cupressaceae species (e.g., Cupressus atlantica Gaussen, Cupressus dupreziana A. Camus, and Juniperus thurifera L.) face extinction in parts of their native range, whereas C. sempervirens largely suffers from the disastrous spread of an exotic disease, cypress bark canker . Since the 1990s, several studies have attempted to establish the part played by cone and seed insects in limiting the potential for natural regeneration of Mediterranean cypresses and junipers (Guido et al 1995;Garcia 1998;Roques et al 1999b;Roques and Battisti 1999;Battisti et al 2000;Blasco-Zumeta 2000;Garcia et al 2000) and in disseminating pathogenic fungi (Battisti et al , 2003Ramos and Caetano 1999). Seed bugs have always appeared to constitute a key element of the cone entomofauna, but their bionomics have remained unclear because they are external predators of seed cones and thus are usually difficult to sample.…”

Section: Introductionmentioning

confidence: 99%

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

Rouault¹,

Cantini

Battisti

et al. 2005

Can Entomol

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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.

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“…These trees were selected randomly for cone sampling. As genotype does not significantly affect the feeding and oviposition of Orsillusmaculatus, as established in a previous trial (Battisti et al, 2003), we considered the samples of cones irrespective of their genetic composition.…”

Section: Cone Sampling Proceduresmentioning

confidence: 99%

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

Rouault¹,

Battisti

Roques³

2006

Biocontrol

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Phytophagous insects have many strategies to escape parasitoids, for example by hiding eggs into plant tissues, but oviposition in holes made by another insect is rather scarce. The cypress seed bug Orsillus maculatus Fieber (Heteroptera: Lygaeidae) is strictly dependent on the availability of cones of Cupressus sempervirens L. to oviposit. Females lay eggs either in exit holes cut through the cone scale by emerging adults of the cypress seed chalcid, Megastigmus wachtli Seitner (Hymenoptera: Torymidae), or on the inner side of scales of partly open cones. A recently discovered egg parasitoid belonging to the genus Telenomus has been shown to attack bug eggs in both oviposition sites. In this paper we investigated the parasitoid performance according to oviposition sites. Field samplings were conducted in two evergreen cypress orchards located in the south of France. The distribution and condition of the egg patches were compared between the two locations and oviposition sites. Seed bugs preferred to oviposit in emergence holes of M. wachtli, and parasitoid performance was higher in eggs laid on cone scales. The chalcid emergence holes seemed to ensure bug eggs with enemy-free space. Oviposition site selection could be an adaptive strategy to escape parasitoid attack.

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Serotinous cones of Cupressus sempervirens provide viable seeds in spite of high seed predation

Cited by 13 publications

References 16 publications

Oviposition strategies of conifer seed chalcids in relation to host phenology

Oviposition strategies of conifer seed chalcids in relation to host phenology

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

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

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