01869nas a2200169   4500008004500000020001400045245005900059210005700118260001300175300001200188490000800200520134300208653002101551100002101572700001901593856008701612       2008                        Engldsh    a0022-519300aProlonged diapause: a trait increasing invasion speed?0 aProlonged diapause a trait increasing invasion speed  cMarch 21  a317-3300 v2513 aInvasive species are considered to be the second cause of biodiversity erosion, and one challenge is to determine the life history traits that cause an increased invasion capacity. Prolonged diapause is a major trait in evolution and insect population dynamics, but its effects on invasion speed remain unknown. From a recently developed mathematical approach (integro-difference equations) applied to the insect dormancy, we show that despite a dispersal cost, bet-hedging diapause strategies with low (0.1-0.2) prolonged diapause frequency (emergence after I or 2 years) can have a higher invasion speed than a simple diapause strategy (emergence after I year) when the environmental stochasticity is sufficiently high. In such conditions, prolonged diapause is a trait supporting invasion capacity by increasing population stochastic growth rate. This conclusion, which applies to a large range of demographic parameters, is in opposition to the usual view that prolonged dormancy is an alternative strategy to dispersal. However, prolonged diapause does not support invasion if the level of environmental stochasticity is low. Therefore, conclusion about its influence on invasion ability needs a good knowledge of environmental stochasticity in the introduction area of considered species. (C) 2008 Elsevier Ltd. All rights reserved.10aCurculio elephas1 aMahdjoub, Tewfik1 aMenu, Frederic  uhttps://weevil.myspecies.info/prolonged-diapause-trait-increasing-invasion-speed-001867nas a2200169   4500008004500000020001400045245005900059210005700118260001300175300001200188490000800200520134300208653002101551100002101572700001901593856008501612       2008                        Engldsh    a0022-519300aProlonged diapause: a trait increasing invasion speed?0 aProlonged diapause a trait increasing invasion speed  cMarch 21  a317-3300 v2513 aInvasive species are considered to be the second cause of biodiversity erosion, and one challenge is to determine the life history traits that cause an increased invasion capacity. Prolonged diapause is a major trait in evolution and insect population dynamics, but its effects on invasion speed remain unknown. From a recently developed mathematical approach (integro-difference equations) applied to the insect dormancy, we show that despite a dispersal cost, bet-hedging diapause strategies with low (0.1-0.2) prolonged diapause frequency (emergence after I or 2 years) can have a higher invasion speed than a simple diapause strategy (emergence after I year) when the environmental stochasticity is sufficiently high. In such conditions, prolonged diapause is a trait supporting invasion capacity by increasing population stochastic growth rate. This conclusion, which applies to a large range of demographic parameters, is in opposition to the usual view that prolonged dormancy is an alternative strategy to dispersal. However, prolonged diapause does not support invasion if the level of environmental stochasticity is low. Therefore, conclusion about its influence on invasion ability needs a good knowledge of environmental stochasticity in the introduction area of considered species. (C) 2008 Elsevier Ltd. All rights reserved.10aCurculio elephas1 aMahdjoub, Tewfik1 aMenu, Frederic  uhttps://weevil.myspecies.info/prolonged-diapause-trait-increasing-invasion-speed02983nas a2200193   4500008004100000020001400041245016000055210006900215260001300284300001400297490000700311520222700318653002102545653002202566100002302588700001602611700002702627856013502654       2009                        eng d  a0022-047700aPre-dispersal acorn predation in mixed oak forests: interspecific differences are driven by the interplay among seed phenology, seed size and predator size0 aPredispersal acorn predation in mixed oak forests interspecific   cNovember  a1416-14230 v973 a1. Pre-dispersal seed predation (PSP) often occurs in multi-host-predator systems (e.g. several plant species exposed to a common array of granivorous insects). However, whether the interaction among seed phenology, seed size and predator size accounts for interspecific differences in PSP remains elusive. 2. We studied PSP in a mixed-oak forest with two oaks (the larger-seeded Quercus humilis and the smaller-seeded Q. ilex), both depredated by two acorn weevils (the smaller Curculio glandium and the larger C. elephas). We intensively monitored acorn production and infestation phenology and we identified the weevil species depredating acorns by means of DNA taxonomy. 3. The minimum acorn size required for infestation was lower for C. glandium than for C. elephas, in accordance with their different body sizes. This resulted in an earlier infestation phenology in C. glandium and the ability of this species to infest both smaller and larger acorns. Above a minimum acorn size threshold, no selection for larger acorns by weevils was observed. 4. Initial acorn crop size was similar in the two oaks. Nonetheless, the earlier acorn phenology and the production of larger acorns in Q. humilis favoured the earlier infestation by C. glandium and the predation by both small and large weevils. Smaller acorns of Q. ilex almost excluded infestation by the larger C. elephas. 5. Although larger acorns of Q. humilis could better survive infestation (preserve the embryo), higher PSP in this species finally resulted in a lower mature acorn crop size than in Q. ilex. 6. Synthesis. In a multi-host-predator system, smaller-seeded species may benefit from a reduced PSP because they exclude larger granivorous insects, but also by means of a 'free-rider effect', if larger-seeded heterospecifics earlier reach a critical size to be depredated. These results also highlight the benefits of a small body size in granivorous insects to depredate seeds earlier and to forage on a wider range of seed sizes. Whether the advantage of 'being small' in this antagonistic plant-animal interaction is offset by other processes, or whether it results in a pressure towards seed and insect size reduction, deserves further attention.10aCurculio elephas10aCurculio glandium1 aEspelta, Josep, M.1 aBonal, Raul1 aSanchez-Humanes, Belen  uhttps://weevil.myspecies.info/pre-dispersal-acorn-predation-mixed-oak-forests-interspecific-differences-are-driven-interplay-among02167nas a2200169   4500008004100000020001400041245011300055210006900168260000900237300001200246490000700258520154800265653002101813100001601834700001901850856012801869       2009                        eng d  a0307-694600aSeed weevils living on the edge: pressures and conflicts over body size in the endoparasitic Curculio larvae0 aSeed weevils living on the edge pressures and conflicts over bod  cJune  a304-3090 v343 a1. Body size in parasitic insects can be subjected to contrasting selective pressures, especially if they complete their development within a single host. On the one hand, a larger body size is associated with a higher fitness. On the other hand, the host offers a discrete amount of resources, thus constraining the evolution of a disproportionate body size.2. The present study used the weevil Curculio elephas as a study model. Larvae develop within a single acorn, feeding on its cotyledons, and larval body size is strongly related to individual fitness.3. The relationship between larval and acorn size was negatively exponential. Larval growth was constrained in small acorns, which did not provide enough food for the weevils to attain their potential size. Larval size increased and levelled off in acorns over a certain size (inflexion point), in which cotyledons were rarely depleted. When there were more than one larva per acorn, a larger acorn was necessary to avoid food depletion.4. The results show that C. elephas larvae are sometimes endoparasitic, living on the edge of host holding capacity. If they were smaller they could avoid food depletion more easily, but the fitness benefits linked to a larger size have probably promoted body size increase. The strong negative effects of conspecific competition may have possibly influenced female strategy of laying a single egg per seed.5. Being larger and fitter, but always within the limits of the available host sizes, may be one main evolutionary dilemma in endoparasites.10aCurculio elephas1 aBonal, Raul1 aMunoz, Alberto  uhttps://weevil.myspecies.info/seed-weevils-living-edge-pressures-and-conflicts-over-body-size-endoparasitic-curculio-larvae02738nas a2200181   4500008004100000020001400041245010300055210006900158260000900227300001200236490000700248520210700255653002102362100001602383700001902399700001602418856012202434       2007                        eng d  a0269-765300aSatiation of predispersal seed predators: the importance of considering both plant and seed levels0 aSatiation of predispersal seed predators the importance of consi  cJune  a367-3800 v213 aPlants can redeuce the fitness costs of granivory by satiating seed predators. The most common satiation mechanism is the production of large crops, which ensures that a proportion of the seeds survive predation. Nevertheless, satiation of small granivores at the seed level may also exist. Larger seeds would satiate more efficiently, enhancing the probability of seed survival after having been attacked. However, a larger seed size could compromise the efficiency of satiation by means of large crops if there were a negative relationship between seed size and the number of seeds produced by an individual plant. We analyze both types of satiation in the interaction between the holm oak Quercus ilex and the chestnut weevil Curculio elephas. Both crop size and acorn size differed strongly in a sample of 32 trees. Larger crop sizes satiated weevils, and higher proportions of the seeds were not attacked as crop size increased. Larger seeds also satiated weevil larvae, as a larger acorn size increased the likelihood of embryo survival. Seedling size was strongly related to acorn size and was reduced by weevil attack, but seedlings coming from large weeviled acorns were still larger. The number and the size of the acorns produced by individual trees were negatively related. Larger proportions of the crop were infested in oaks producing less numerous crops of larger acorns. However, contrary to expectations, these trees did not satiate more effectively at the seed level either. Effective satiation by larger acorns was precluded by larger multi-infestation rates associated to smaller seed crops, in such a way that the proportion of attacked seeds that survived did not vary among trees with different acorn sizes. These results highlight the need of considering satiation by means of large crops and large seeds in studies of predispersal seed predation. Long-term monitoring on individual oaks will help to assess whether there is a trade-off between the number and the size of the acorns and, if it existed, how it could condition the fitness consequences of both types of satiation.10aCurculio elephas1 aBonal, Raul1 aMunoz, Alberto1 aDiaz, Mario  uhttps://weevil.myspecies.info/satiation-predispersal-seed-predators-importance-considering-both-plant-and-seed-levels02246nas a2200181   4500008004100000020001400041245012900055210006900184260000800253300001200261490000700273520156700280653002101847100001601868700001901884700002601903856013501929       2010                        eng d  a0307-694600aMismatch between the timing of oviposition and the seasonal optimum. The stochastic phenology of Mediterranean acorn weevils0 aMismatch between the timing of oviposition and the seasonal opti  cJun  a270-2780 v353 a1. The timing of reproduction is predicted to match the period of maximum food availability. In this sense, the case of many phytophagous insects in temperate regions is very illustrative, as their larvae usually depend on a resource only available for a limited period of time each year. 2. For 3 years the interactions between the weevil Curculio elephas and the Mediterranean Holm oak Quercus ilex were studied. Weevil larvae grow within the acorns, feeding on the cotyledons. The timing of oviposition will determine food availability for the larvae, as acorns stop growing once they are attacked. 3. Acorn temporal growing patterns did not change between years and food availability for larvae was at its highest in October, when temperature was still suitable for larval development. However, oviposition phenology did change between years. In 2002 females oviposited later, larvae grew within larger acorns, and their body mass was significantly higher than in 2003 or 2004, when females oviposited into early acorns. 4. Thus, weevils do not always adjust oviposition to the best possible feeding conditions for their offspring. Rather, they seem to maximise their own lifetime fitness, ovipositing as soon as they emerge in late summer. Emergence, in turn, depends strongly on stochastic events such as summer storms in the Mediterranean region. 5. Under a climate change perspective, the trend towards higher August rainfall recorded in our study area may alter oviposition phenology, with the subsequent cascade effects on weevil body size and fitness.10aCurculio elephas1 aBonal, Raul1 aMunoz, Alberto1 aEspelta, Josep, Maria  uhttps://weevil.myspecies.info/mismatch-between-timing-oviposition-and-seasonal-optimum-stochastic-phenology-mediterranean-acorn-we02307nas a2200169   4500008004500000020001400045245013300059210006900192260001300261300001000274490000700284520165500291653002101946100001601967700001901983856013502002       2008                        Engldsh    a0307-694600aSeed growth suppression constrains the growth of seed parasites: premature acorn abscission reduces Curculio elephas larval size0 aSeed growth suppression constrains the growth of seed parasites   cFebruary  a31-360 v333 a1. The abscission of seeds infested by insects is common in many plants and has been proposed as a defensive mechanism, although its negative consequences for insects have rarely been assessed. 2. We assessed the consequences of seed abscission studying the interactions between the holm oak Quercus ilex and the chestnut weevil Curculio elephas, its main pre-dispersal seed predator. Female weevils oviposit into the acorns and the larvae must complete their development inside a single acorn feeding on the cotyledons. The growth of the infested acorns is suppressed because they are prematurely abscised. 3. Female weevils oviposit along the acorn growing period; hence, the size of the infested acorns increased with date. The growth of the larvae inside the smaller, early infested, acorns was constrained because food (i.e. cotyledons) was frequently depleted. Larval size increased with the date along with the size of the infested acorns, but it declined slightly in the latest dates as a result of the higher conspecific competition provoked by the larger number of larvae per acorn. 4. The present results demonstrate that premature seed abscission by Q. ilex had negative consequences for C. elephas, as a smaller acorn size reduced food availability and constrained larval size, a key insect life history trait. At the same time, it is suggested that the growth suppression of infested acorns may condition the oviposition phenology of these insects according to their body size. These results need to be considered in further research in the context of the evolutionary significance of premature seed abscission as a defensive mechanism.10aCurculio elephas1 aBonal, Raul1 aMunoz, Alberto  uhttps://weevil.myspecies.info/seed-growth-suppression-constrains-growth-seed-parasites-premature-acorn-abscission-reduces-curculio02525nas a2200193   4500008004100000020001400041245012500055210006900180260000800249300001400257490000800271520181700279653001302096653002102109100001602130700002602146700002402172856013502196       2011                        eng d  a0029-854900aComplex selection on life-history traits and the maintenance of variation in exaggerated rostrum length in acorn weevils0 aComplex selection on lifehistory traits and the maintenance of v  cDec  a1053-10610 v1673 aTrophic interactions can trigger the development of exaggerated specialized characters and promote morphological diversification. For example, acorn weevils (genus Curculio) present strikingly long rostrums, which are used by females to perforate oviposition holes through the seed coat. Species exhibiting longer rostrums are known to exploit larger acorns, and therefore rostrum length is thought to be subject to selection to match the preferred acorn type. However, rostrum length is strongly correlated with body size, and morphological divergence could result from either selection on rostrum length for optimal food exploitation or from other pressures acting on body size. We collected infested acorns at oak forests where the large Curculio elephas and the small-bodied Curculio glandium co-occur. There were no interspecific differences in adult female body size to rostrum length allometric relationships, and rostrum length is equally correlated with body size in either species. MtDNA-based species identification showed that C. glandium larvae were present within acorns of all sizes, whereas C. elephas larvae were restricted to acorns above a minimum size, irrespective of oak species. Hence, exploitation of large acorns can hardly have triggered rostrum enlargement, as the small sized C. glandium adults (with short rostrums) could perforate and oviposit in both small and large acorns. Rather, increased rostrum length is probably a by-product of the larger body sizes of individuals emerging from bigger acorns, which allow increased larval size and enhance larval survival likelihood. Summarizing, when exaggerated feeding traits co-vary with other body features, interspecific morphological variability may result from contrasting selective pressures acting on these correlated characters.10aCurculio10aCurculio elephas1 aBonal, Raul1 aEspelta, Josep, Maria1 aVogler, Alfried, P.  uhttps://weevil.myspecies.info/complex-selection-life-history-traits-and-maintenance-variation-exaggerated-rostrum-length-acorn-wee