Topic
Curculio
About: Curculio is a research topic. Over the lifetime, 339 publications have been published within this topic receiving 4149 citations.
Papers published on a yearly basis
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Papers
TL;DR: It is concluded that the relationship between seed production and seedling recruitment in Quercus robur is variable from site to site: oak recruitment is seed-limited in open sites where vertebrate herbivores are scarce, microsite-limited beneath a dense forest canopy, but herbivore- limited in other sites, especially those where rabbits are abundant.
Abstract: 1 We investigated the relationship between seed production and seedling recruitment in Quercus robur in order to determine whether oak recruitment was seed-limited, herbivore-limited or microsite-limited. Over a 15-year period, Q. robur showed a pattern of alternate bearing, with significant (but not complete) synchrony between individual trees at several sites in south-east England. 2 Seedling recruitment was assessed in three ways: by annual destructive sampling, by monitoring permanent quadrats, and by ageing destructive samples of saplings using basal ring counts. 3 Seedling recruitment was closely correlated with the size of the acorn crop in some habitats but not others. In Sunningdale, where a competition-free seed bed was available every year and where seed predators were relatively scarce, oak seedlings appeared almost every year, and three peak densities of seedling recruitment followed three peaks of acorn production during the period 1985-92. In Silwood Park, where rabbits were abundant, there was little seedling recruitment except within rabbit exclosures and then only in years of peak acorn production. In Windsor Great Park, rabbit densities were lower and seedling recruitment was higher than at Silwood Park, but the association between seedling recruitment and acorn production could not be established with confidence because of imprecision in ageing the saplings. 4 Rates of acorn loss to invertebrate seed predators were broadly consistent with the hypothesis of predator satiation; low acorn crops suffered a higher percentage mortality than large acorn crops. The two principal acorn-feeding insects (the alien cynipid gall wasp Andricus quercuscalicis and the native weevil Curculio glandium) killed between 30% and 90% of the acorn crop in given years and between 0% and 100% of the acorn crop on individual trees. Vertebrate herbivores (principally rabbits and wood mice) destroyed most of the sound acorns in low years, removing experimentally placed acorns within 24 h. 5 The effectiveness of alternate bearing as a defence against short-lived, specialist insect herbivores and long-lived, generalist vertebrate herbivores is discussed. The evidence presently available does not allow us to discriminate between the competing hypotheses that alternate bearing is an evolved, antipredator strategy on the part of the oaks, or a constraint imposed by limited resource availability within the trees. 6 We conclude that the relationship between seed production and seedling recruitment in Quercus robur is variable from site to site: oak recruitment is seed-limited in open sites where vertebrate herbivores are scarce, microsite-limited beneath a dense forest canopy, but herbivore-limited in other sites, especially those where rabbits are abundant.
394 citations
TL;DR: It is suggested that the higher tannin levels may render the apical portion of the seeds less palatable, and thereby increase the probability of embryo survival after attack by seed consumers.
Abstract: -A common assumption in studies of seed predation is that seeds survive attack and are dispersed only 'when animals fail to find seeds, drop undamaged seeds or fail to recover seeds after they are cached. This study, however, suggests that many acorn consumers consistently eat only a portion of the cotyledon of several species of acorns and thereby permit embryo survival. Several vertebrates [gray squirrels (Sciurus carolinensis), common grackles (Quiscalus quiscula) and blue jays (Cyanocita cristata)] were observed to consume only 30-60% of the cotyledon from the basal portion (cap end) of willow oak (Quercus phellos) acorns. Gray squirrels exhibited a similar preference for the basal end of acorns of several other species of red oaks (Q. rubra, Q. laevis, Q. nigra, Q. palustris and Q. coccinea) from a wide geographic region. In addition, acorn weevil larvae (Curculio sp.) were observed significantly (>35%) more often in the basal portion than in the apical end of Q. alba acorns. Chemical analyses of acorns from two tree species revealed that the concentration of protein-precipitable phenolics (primarily tannins) was 12.5% (Q. phellos) and 84.2% (Q. laevis) higher in the apical portion of the seeds where the embryo is located. Moreover, germination experiments revealed equal or greater germination frequencies for partially consumed acorns than for intact acorns. We suggest that the higher tannin levels may render the apical portion less palatable, and thereby increase the probability of embryo survival after attack by seed consumers.
165 citations
TL;DR: Results indicate that squirrels can distinguish between infested and noninfested acorns, that they often selectively cache sound acorns, and that weevils represent a significant dietary supplement for squirrels.
Abstract: We tested the caching and feeding responses of gray squirrels ( Sciurus carolinensis ) to acorns of three species of oaks ( Quercus alba, Q. palustris , and Q. rubra ) infested with weevil larvae ( Curculio ). Experiments were designed to test the primary hypothesis that squirrels selectively cache sound acorns and the secondary hypothesis that such response may be due to increased perishability resulting from infestation. In an open, suburban oak ( Quercus ) forest in northeastern Pennsylvania, we presented free-ranging animals with whole, infested acorns, whole, noninfested acorns, and noninfested acorns from which the pericarp (shell) was removed to increase perishability. Squirrels cached significantly (20–35%) more of whole, intact acorns of red oak, dispersed these acorns significantly greater distances before caching them, and consumed shelled and infested acorns. Squirrels showed a similar response to acorns of pin oak, but ate significantly more of both infested and noninfested acorns of white oak. Squirrels also were observed to consume weevil larvae in >76% of all trials with infested acorns. These results indicate that squirrels can distinguish between infested and noninfested acorns, that they often selectively cache sound acorns, and that weevils represent a significant dietary supplement for squirrels. We also suggest that gray squirrels may exert a strong influence on the dispersal of oaks by selecting viable seeds for storage.
122 citations
TL;DR: It is found that simple predator satiation fails due to the synchrony of the life-cycle of acorn-feeding insects and the periodical production of acorns, and the proportion of sound acorns notably increased in a rich crop after a disturbance in alternate bearing.
Abstract: Quercus crispula (=Q. mongolica var. grosseserrata) is the predominant tree species in cool temperate, mixed broadleaf/conifer forests in northern Japan. We compared 11 years of data on acorn production in a population of Q. crispula, with data on seed-insect populations, to try to answer the following questions: (1) Does Q. crispula show a regular pattern of masting? (2) How long do principal seed predators remain in diapause? (3) How do the seed predators affect the pattern of predator satiation? Q. crispula showed a tendency to alternate bearing, with significant synchrony between individual trees. The principal acorn-feeding insects (Curculio spp. weevils), which infested 25%–70% of matured acorns, generally exhibited a prolonged diapause of 2 years. No significant negative relationship was found between the rate of injury by the weevils and the density of mature acorns, indicating that simple predator satiation fails due to the synchrony of the life-cycle of acorn-feeding insects and the periodical production of acorns. However, the rate of injury by the weevils was negatively correlated with the relative abundance of mature acorns to the number of weevil larvae that had matured 2 years previously. Thus, the proportion of sound acorns notably increased in a rich crop after a disturbance in alternate bearing. Prolonged diapause of specific seed predators is critical in determining the peak year of sound-seed production.
106 citations
TL;DR: The results suggest that the Sodalis-allied symbiont was certainly acquired by an ancestor of the Sitophilus weevils and replaced the original Nardonella symbionts, but the symbiotic association must have experienced occasional re-associations such as new acquisitions, horizontal transfers, replacements and/or losses.
Abstract: The processes and mechanisms underlying the diversification of host–microbe endosymbiotic associations are of evolutionary interest. Here we investigated the bacteriocyte-associated primary symbionts of weevils wherein the ancient symbiont Nardonella has experienced two independent replacement events: once by Curculioniphilus symbiont in the lineage of Curculio and allied weevils of the tribe Curculionini, and once by Sodalis-allied symbiont in the lineage of grain weevils of the genus Sitophilus. The Curculioniphilus symbiont was detected from 27 of 36 Curculionini species examined, the symbiont phylogeny was congruent with the host weevil phylogeny, and the symbiont gene sequences exhibited AT-biased nucleotide compositions and accelerated molecular evolution. These results suggest that the Curculioniphilus symbiont was acquired by an ancestor of the tribe Curculionini, replaced the original symbiont Nardonella, and has co-speciated with the host weevils over evolutionary time, but has been occasionally lost in several host lineages. By contrast, the Sodalis-allied symbiont of Sitophilus weevils exhibited no host–symbiont co-speciation, no AT-biased nucleotide compositions and only moderately accelerated molecular evolution. These results suggest that the Sodalis-allied symbiont was certainly acquired by an ancestor of the Sitophilus weevils and replaced the original Nardonella symbiont, but the symbiotic association must have experienced occasional re-associations such as new acquisitions, horizontal transfers, replacements and/or losses. We detected Sodalis-allied facultative symbionts in populations of the Curculionini weevils, which might represent potential evolutionary sources of the Sodalis-allied primary symbionts. Comparison of these newcomer bacteriocyte-associated symbiont lineages highlights potential evolutionary trajectories and consequences of novel symbionts after independent replacements of the same ancient symbiont.
105 citations
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| Year | Papers |
|---|---|
| 2025 | 9 |
| 2024 | 9 |
| 2023 | 16 |
| 2022 | 39 |
| 2021 | 10 |
| 2020 | 19 |