槲栎种子雨进程中昆虫的捕食特征

为了了解昆虫捕食与槲栎Quercus aliena种子大小和产量的关系以及在栎林更新中的作用,于2008和2009年秋季,分别在暖温带伏牛山系天池山国家森林公园内研究了两个年度槲栎的种子雨过程及昆虫捕食特征。结果表明：（1）种子雨过程从8月中下旬到9月底约经历40 d,存在高峰期且时段较明显,高峰期下落种子量分别占全部种子雨量的78.13%（2008年）和75.91%（2009年）;（2）槲栎的种子雨强度年间存在较大差异,2008年明显小于2009年（两年分别为31.75±16.65粒/m²和51.92±29.26粒/m²）,但2009年的橡子明显比2008年小（两年分别为1.94±0.61 cm³和2.46±0.57 cm³）;（3）种子雨构成比例在两个年份间存在差异,完好种子的量分别为59.05%（2008年）和36.12%（2009年）,虫蛀率在大量结实的2009年显著提高;（4）虫蛀橡子（2.29±0.42 cm³）显著大于完整橡子（1.59±0.32 cm³）,且虫蛀种子中所含虫卵数与种子大小显著正相关,昆虫有选择大种子产卵寄生的偏好。本研究的结果说明,昆虫对槲栎大种子有寄生选择偏好;大部分槲栎种子遭遇象甲虫蛀而降低生命活力,这可能是影响槲栎林更新的主要因素之一。     

秦岭南坡短柄枹栎和锐齿槲栎的种子产量和种子大小及其与昆虫寄生的关系

【目的】为了解昆虫寄生特征与短柄枹栎 Quercus glandulifera 和锐齿槲栎 Quercus aliena var. acuteserrata 的种子产量及种子大小的关系。【方法】本研究于2011和2012年在秦岭南坡佛坪国家自然保护区,对短柄枹栎和锐齿槲栎种群的种子产量和昆虫寄生特征进行了野外调查研究。【结果】2年中短柄枹栎、锐齿槲栎种子雨密度和种子产量均差异明显,2011年短柄枹栎种子雨密度和种子产量分别为145.76±24.56粒/m²和74.97±11.56粒/m²,分别显著高于2012年的64.09±9.61粒/m²和34.30±3.51粒/m²;2011年锐齿槲栎种子雨密度和种子产量分别为238.88±43.97粒/m²和117.34±18.76粒/m²,分别显著高于2012年的112.00±19.20粒/m²和55.96±19.20粒/m²。2011年短柄枹栎和锐齿槲栎的种子产量中完好种子所占比例分别为49.73%和50.73%,分别显著高于2012年的38.69%和44.28%;而2011年虫蛀短柄枹栎和锐齿槲栎种子所占比例分别为28.05%和19.31%,分别低于2012年的39.77%和26.63%,但并无显著差异。2011和2012年,短柄枹栎和锐齿槲栎虫蛀种子个体均显著大于完好种子,且2011年二者虫蛀种子所含幼虫数与种子大小的相关性显著,2012年二者相关性不显著。【结论】短柄枹栎和锐齿槲栎种子的虫蛀率与种子产量有一定的关系,即在种子产量较低年份,虫蛀率有升高趋势,反之有降低趋势。同时,昆虫对这两种栎树种子中个体大的种子有寄生选择偏好,同时虫蛀种子所含幼虫数与种子大小也有一定的关系,即种子越大,所含昆虫幼虫数就越多。     

滇青冈和高山栲种子昆虫寄生及其对种群更新的影响

对昆明西山地区滇青冈(Cyclobalanopsis glaucoides)和高山栲(Castanopsis delavayi)种子(坚果)虫蛀率在两个年份、整个落种期和山坡不同部位的变化情况进行研究,结果表明：① 寄生于滇青冈种子内的象甲为青冈象(Curculio megadens)和Curculio sp.,寄生于高山栲种子内的象甲是Curculio sp.和剪枝象(Cyllorhynchites sp.);② 滇青冈样地的虫蛀率为2484%~2760%,样地间无显著差异,两年间的平均虫蛀率亦无显著差异;高山栲样地间虫蛀率为1794%~2655%,有显著差异性,两年间的平均虫蛀率也有显著差异。③ 高山栲的下落种子虫蛀率随时间逐步下降,9月和10月中下旬出现两个虫蛀率的高峰期;高山栲种子内寄生的昆虫落地后即入土化蛹,滇青冈落地种子内的寄生昆虫在初期会滞留一段时间;④ 虫蛀率与林下实生苗数量无显著相关性,实生苗多集中在大树周围以及草本层植物较丰富的小生境。     

鼠类对辽东栎橡子的搬运

在北京东灵山地区,在灌丛、森林2 种生境类型中共设计了5 个处理,以检验种子质量、种子可视度、生境类型如何影响鼠类对辽东栎（Quercus liaotungensis）橡子的搬运。每个处理包括200 枚种子。每日检查种子状态,实验持续16 d。鼠类在几天之内将大多数种子搬运走。完好橡子比虫蛀橡子消失得快。橡子在森林生境中明显比在灌丛生境中消失的快。鼠类对放置在灌丛下方和灌丛之间的橡子的搬运速率差别不大。放置在落叶下方的橡子消失速率明显慢于地表的橡子。本研究利用半存活时间测量种子的搬运率。各处理的半存活时间范围是0. 6 ～ 8. 6 d。各处理的橡子搬运率均较高,这说明鼠类有能力在种子下落到冬季来临的2 个月时间内,搬运绝大多数的橡子。实验说明,鼠类是辽东栎橡子重要的捕食者和扩散者。     

外果皮厚度和种子大小对五种栎属橡子扩散的影响

动物对种子的扩散和贮藏是一个复杂的生态学过程,常常受到种子特征的影响。有关种子特征如何影响动物对种子扩散,许多研究结果并非完全一致。我们于2009 年9 月在黑龙江东方红林场野外和围栏内释放五种栎属橡子(Quercus mongolica,Q.serrata var. brevipetiolata,Q. aliena,Q.variabilis 和Q. liaotungensis),研究种子特征对鼠类(Apodemus peninsulae, Clethrionomys rufocanus 和Tamias sibiricus)扩散和埋藏橡子的影响。野外释放结果表明:橡子大小和外果皮厚度显著影响鼠类对橡子的扩散和埋藏。鼠类偏向扩散和埋藏种皮厚的大橡子,种皮薄的小橡子则多被原地取食。种皮厚的大橡子扩散距离显著高于种皮薄的小橡子。然而,只有外果皮的厚度显著影响围栏内花鼠对橡子的扩散和埋藏,橡子大小并非主要的影响因素。种子特征影响种子扩散的效应可能在种群和群落水平上存在差异。     

两种象甲幼虫肠道微生物组成及对高单宁食物的适应

【目的】象甲是栎属植物橡子中主要的寄生昆虫,但其适应高单宁食物(橡子)的肠道微生物基础尚待揭示。本研究分析了蒙古栎和辽东栎橡子中两种柞栎象(Curculio arakawai和C.dentipes)幼虫的肠道菌群结构和多样性,试图阐明柞栎象幼虫适应高单宁食物的肠道微生物基础。【方法】分别提取蒙古栎和辽东栎橡子中象甲幼虫各50头的肠道DNA,利用Illumina MiSeq技术对肠道菌群的V3–V4区序列进行16S rRNA测序,统计样品操作分类单元(OTU)数量,分析物种组成丰度、α多样性和β多样性。【结果】结果表明,可用于物种分类的OTU分别有2054和2308个,C. arakawai和C. dentipes共有的OUT 481个。在两种柞栎象C. arakawai和C. dentipes肠道菌群中,共注释到的主要分类阶元有27个门、145个科和274个属。变形菌门(Proteobacteria)、拟杆菌门(Bacteroidetes)和厚壁菌门(Firmicutes)在两种象甲肠道菌群中占优势;假单胞菌属Pseudomonas(63.8%)、沙雷氏菌属Serratia(6%)和不动杆菌属Acinetobacter (5.2%)是C. arakawai肠道中的主要类群,而沙雷氏菌属Serratia (32%)、拉恩菌属Rahnella(24.2%)、气单胞菌属Aeromonas(6.8%)和立克次体属Rickettsia(6.6%)在C.dentipes肠道菌群中占主导优势。C. arakawai和C. dentipes肠道菌群α多样性无显著差异,β多样性则差异显著。具有单宁酶活性的肠道细菌,如粘质沙雷菌Serratia marcescens、乳球菌Lactococcus lactis、假单胞菌Pseudomonas spp.在C. arakawai和C. dentipes之间差异不显著。【结论】寄生在蒙古栎和辽东栎橡子中的C. arakawai和C.dentipes肠道菌群组成迥异,这可能与遗传因素和食物特点有关。具有单宁酶活性的粘质沙雷氏菌Serratia marcescens和乳球菌Lactococcus lactis等菌类可能是两种象甲幼虫适应高单宁食物的肠道微生物基础。     

幼虫密度和温度对水芹叶象甲未成熟阶段生长发育的影响

[目的]为明确不同幼虫密度和不同温度条件对水芹叶象甲Hypera sp.未成熟阶段生长发育的影响.[方法]在室内条件下对不同幼虫饲养密度和不同温度条件饲养的水芹叶象甲未成熟阶段(卵、幼虫、预蛹和蛹)的存活和生长发育进行研究.[结果]幼虫密度对水芹叶象甲幼虫、预蛹和蛹的存活和生长发育均具有显著影响.水芹叶象甲幼虫、预蛹和蛹在50头/盒的密度条件下的存活率均显著高于其它密度条件,且发育历期显著短于其它密度条件.此外,各密度条件下的雌蛹重均显著重于雄蛹重,但性比(♀/♂)不受密度条件的影响.温度条件对水芹叶象甲卵、幼虫、预蛹和蛹的存活和生长发育亦均具有显著影响.27℃条件下的幼虫和蛹的存活率均显著高于其它温度条件,1龄幼虫在30℃条件下的存活率显著高于其它温度条件,而3龄幼虫在27℃条件下的存活率显著高于其它温度条件,但温度条件对2龄幼虫的存活率无显著影响.水芹叶象甲各龄期幼虫及各虫态的发育历期随着温度升高而显著缩短.[结论]幼虫饲养密度和温度是影响水芹叶象甲种群变化的重要因子,这将为分析水芹叶象甲种群动态变化规律,以 及提高该虫的预测预报和综合防控水平提供依据.     

都江堰地区灌丛内袍栎橡子的捕食和搬运

从2000年9月至2002年12月,以四川都江堰常绿阔叶林灌丛内的优势种--枹栎(Quercus serrata)为研究对象,研究了昆虫、鼠类和真菌对枹栎橡子的捕食和搬运.结果表明(1)取食橡子的鼠类的群落结构和数量在年间差异较小,这可能与三年间袍栎橡子的产量相对稳定有关;(2)袍栎橡子的虫蛀率在三年间存在显著性差异,范围在14.17%-32.49%之间;(3)鼠类的就地取食和搬运是影响种子库内橡子命运的主要因素;(4)橡子虫蛀率的变化影响鼠类的觅食活动.鼠类对饱满橡子和虫蛀橡子的选择性取食和搬运可能影响许多坚果植物(栎树)的自然更新过程[动物学报50(4)535-540,2004].     

昆虫寄生与滇合欢种子大小和数量的关系

以云南地区含羞草科合欢属滇合欢Albizia simeonis为研究对象,在调查滇合欢正常种荚和被昆虫寄生种荚内种子数、种子败育数和种子大小的基础上,研究昆虫寄生对滇合欢种荚内种子数量、大小以及败育的影响,分析了种荚内种子大小和数量之间的关系。结果表明:完好种荚与受害种荚内种子总数差异并不显著,但完好种荚内正常种子数量显著高于受害种荚,而败育种子数则显著低于受害种荚。昆虫寄生并没有对滇合欢种荚内正常种子大小产生显著影响,但被寄生的种子体积显著大于正常种子。种荚内败育种子数与被寄生种子数呈显著正相关关系,表明昆虫寄生对滇合欢种荚内种子败育产生了影响。滇合欢种荚内种子数量与种子大小呈负相关关系,但完好种荚内种子数量与大小的相关性并不显著,而有昆虫寄生的种荚内种子数量与种子大小则表现出显著的负相关,即昆虫寄生加剧了滇合欢种荚内种子大小与数量的权衡。     

都江堰地区灌丛内迺栎橡子的捕食和搬运(英文)

从 2 0 0 0年 9月至 2 0 0 2年 1 2月 ,以四川都江堰常绿阔叶林灌丛内的优势种———栎 (Quercusserrata)为研究对象 ,研究了昆虫、鼠类和真菌对栎橡子的捕食和搬运。结果表明 :(1 )取食橡子的鼠类的群落结构和数量在年间差异较小 ,这可能与三年间栎橡子的产量相对稳定有关 ;(2 )栎橡子的虫蛀率在三年间存在显著性差异 ,范围在 1 4 1 7% - 32 4 9%之间 ;(3)鼠类的就地取食和搬运是影响种子库内橡子命运的主要因素 ;(4 )橡子虫蛀率的变化影响鼠类的觅食活动。鼠类对饱满橡子和虫蛀橡子的选择性取食和搬运可能影响许多坚果植物 (栎树 )的自然更新过程     

Seed growth suppression constrains the growth of seed parasites: premature acorn abscission reduces Curculio elephas larval size

Abstract.  1. 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.     

Multi-trophic effects of ungulate intraguild predation on acorn weevils

Predators and parasitoids may contribute to controlling the population sizes of phytophagous insects, and this has been shown to benefit plants. Phytophagous insects may also be killed by other herbivores (intraguild predation), usually larger-sized vertebrates that ingest insects accidentally while feeding on common food sources. We studied the intraguild predation on acorn weevils by ungulates and assessed the consequences for weevil populations. Infested acorns are prematurely abscised and the weevil larvae finish their development inside the acorns after being dropped. Our results show that weevil larvae were killed by ungulates eating the infested acorns on the ground. Ungulates did not discriminate between infested and sound acorns, and the probability of a larva being incidentally eaten was inversely related to acorn availability. Thus, predation risk was enhanced by the premature drop of infested acorns when acorn availability on the ground was low. Predation rates on infested acorns were much higher where ungulates were present, and acorn infestation rates were significantly lower. However, ungulates did not provide the oaks any net benefit, since the reduction of infestation rates was not enough to compensate for the large amounts of sound acorns eaten by ungulates. Seed predation is usually studied as a progressive loss of seeds by pre- and post-dispersal predators, but the interactions between them are usually not considered. We show that intraguild predation on insects by large ungulates had an effect on the structure of the foraging guild, as the proportion of acorns predated by insects decreased; however, replicating the same experimental design in different ecological scenarios would increase the strength of these results. In conclusion, the present study shows the importance of considering the multi-trophic interactions between seed predators in order to have a complete picture of granivory.     

Large acorns benefit seedling recruitment by satiating weevil larvae in <Emphasis Type="Italic">Quercus aliena</Emphasis>

Plants can enhance their seed viability and survival through reducing the fitness costs of herbivory by satiating seed predators at either plant or seed level, or both. The former satiates with production of large crops while the latter with large-sized seeds, enhancing the probability of seed survival. We analyzed both types of satiation in the interaction between the Quercus aliena and the weevil Curculio spp in 2 years with different crop size and acorn size. Larger crop size seemed to satiate less effectively weevils due to higher proportions of the seeds were attacked in oaks producing more crops of smaller acorns. However, prematurely abscission of infested acorns in large crop year might compensate this ineffectiveness. Larger acorns in lean year well satiated weevil larvae, as a larger acorn size increased the likelihood of embryo survival and seedling establishment. Although effective satiation by larger acorns would be negated by smaller seed crops, the proportion of attacked acorns that survived increased with large acorn size in lean year. These results highlighted the importance of annual variation in acorn size of Quercus aliena in satiating and defending weevil larval predations, consequently in successful seedling recruitment and establishment.     

Satiation of predispersal seed predators: the importance of considering both plant and seed levels

Plants can reduce 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.     

Mismatch between the timing of oviposition and the seasonal optimum. The stochastic phenology of Mediterranean acorn weevils

1. 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     

昆虫寄生对辽东栎种子命运的影响

报道了昆虫寄生对辽东栎 Quercus liaotungensis 种子命运的影响。结果表明：（1）被昆虫寄生的种子发芽率明显低于正常成熟的种子,被昆虫寄生的种子或者不能发芽,或者能发芽但随后死亡;（2）从虫卵到老龄幼虫的发育在橡实内完成,当橡实落地后幼虫破壳而出,整个种子库的幼虫破壳时间延续2～50天,并非高度同步化;种子库的虫寄生率高达45.4%,以柞栎象Curculio dentipes为主,还有少量其它种类,如另一种象虫Curculio sp.、栗白小卷蛾 Cydia kurokoi 和螟蛾科（Pyralidae）的一未定名种;（3）昆虫寄生影响橡实成熟,测量种子大小分布表明,被昆虫寄生的种子的大小分布介于未成熟和成熟种子之间;（4）象虫寄生取食引起16.05% 的种子能量损失,显著低于对照组。结果证明昆虫寄生对辽东栎种子的命运有重要影响,是影响辽东栎种群更新的关键因素之一。     

Seed weevils living on the edge: pressures and conflicts over body size in the endoparasitic Curculio larvae

Abstract 1. 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.     

啮齿动物鉴别虫蛀种子的能力及其对坚果植物更新的潜在影响

作为种子捕食者和种子扩散者, 啮齿动物对产坚果植物的自然更新有很大作用。然而, 对啮齿动物鉴别虫蛀种子的能力颇有争议。2001 年秋季在中国四川都江堰市实验林场, 以3 种比例(I₁∶S = 1∶1 , I₁∶S = 4∶1 和I₁∶I₂∶S = 1∶1∶1)供给啮齿动物4 种壳斗科种子: 栓皮栎( Quercus variabilis) 、枹树( Q. serrata) 、青冈( Cyclobalanopsis glauca) 和栲树( Castanopsis fargesii) 的3 种坚果型(即饱满种子(S) , 不含象虫的虫蛀种子(I₁) 和含象虫的虫蛀种子( I₂ ) 验证了啮齿动物能够准确地鉴别虫蛀种子这一假说。结果表明, 在3 种比例下4 种坚果的虫蛀种子的消失速率均慢于饱满种子。即使虫蛀种子的比例增加, 啮齿动物显著地搬走了更多的饱满种子(67%～92%) 。当虫蛀种子的比例增加时, 虫蛀种子就地消耗和拒绝的比例降低, 搬走比例增加。啮齿动物并不拒绝虫蛀种子, 这可能与它们的可利用性(如象虫可以作为蛋白质的补充) 和数量以及它们的觅食行为有关。结果证实啮齿动物能准确地鉴别虫蛀种子, 从而有区别地搬走并贮藏更多的饱满种子, 消耗一部分可以利用的虫蛀种子(包括其内的象虫) 。这样, 啮齿动物通过对饱满种子和虫蛀种子的鉴别和选择会影响不同种子的命运, 从而对这些坚果植物的自然更新产生影响。     

Acorn selection by Mexican jays: a test of a tri-trophic symbiotic relationship hypothesis

By caching acorns, jays serve as important dispersal agents for oak (Quercus) species. Yet little is known about which acorn characteristics affect selection by jays. In the traditional model of jay/oak symbiosis, large, brown, ripe acorns free of invertebrate parasites (e.g., Curculio acorn weevils) are selected by jays. Recently, it has been suggested that a tri-trophic relationship between oaks, jays, and weevils may have evolved to counter the negative dietary effects of acorn tannins. Under the tri-trophic model, jays would preferentially select acorns containing weevil larvae. We tested the assumptions that (1) acorns containing curculionid larvae exist in sufficient quantities to support jay populations and (2) jays can detect, and preferentially select, acorns containing weevil larvae, and investigated the cues by which jays select acorns. Captive Mexican jays (Aphelocomaultramarina) were presented Emory oak (Quercusemoryi) acorns in aviary feeding trials. Large, dense, viable acorns free of curculionid larvae were preferentially selected. Contrary to results of previous research, color did not affect selection. Acorn viability increased and curculionid larval occupancy decreased in adjacent savannas and isolated stands relative to existing oak woodland, perhaps favoring oak recruitment into adjacent lower-elevation grasslands. Our results compel us to reject the tri-trophic model for this system, and are consistent with the traditional jay/oak symbiosis model. Relatively long-distance dispersal of viable acorns favors Emory oak replacement, and spatial patterns of acorn viability and curculionid parasitism suggest expansion of Emory oak into adjacent low-elevation semi-arid grasslands. Received: 29 February 1996 / Accepted: 26 September 1996