EFFECTS OF AGE AND SIZE ON LIFE HISTORIES AND POPULATION GROWTH OF RHODODENDRON MAXIMUM SHOOTS

Age- and size-specific shoot life histories were studied with population censuses in June 1984 and June 1985 in an evergreen understory shrub. Rhododendron maximum. Most shoots (65%) survived without branching or flowering, and lesser numbers branched (2%), flowered (20%), or died (23%) during the year between censuses. The probabilities of surviving, branching, flowering or dying were both age- and size-dependent. Small, young shoots increased in leaf area. Flowering occurred most prominently in 3- to 6-year old shoots that had exceeded a leaf area of 200 cm², and the rate of flowering increased proportionately with size above this threshold. Branching normally occurred in the year following flowering. The age and size distributions of the population shifted significantly between years, indicating a nonequilibrium population. The survival schedule was Deevey Type I, indicating a high degree of “parental care” of young shoots. Age- and age + size-based demographic models predicted a rapid decline of the shoot population over a decade, while a size-based model predicted a much slower decline in shoot numbers. A sensitivity analysis of the models showed that overall shoot population growth was positively influenced by branching shoots and shoots that added leaf area, and negatively influenced by shoots that lost leaf area, died, or flowered. The role of shoot life histories in determining individual plant fitness and ecological dominance is discussed.     

Behavior of current-year shoots as a mechanism to determine the floral sex allocation at the level of individual tree and population in Siberian alder (Alnus hirsuta var. sibirica)

Floral sex allocation (weight of male flower buds over weight of female flower buds) was examined at the levels of current-year shoot, individual tree and population, and the tree individual level and population level floral sex ratio was explained as a consequence of the behavior of current-year shoots in the shoot-level monoecious (flowering current-year shoots have both male and female flowers) species, Siberian alder (Alnus hirsuta var. sibirica). The current-year shoot level floral sex allocation was not size-dependent and not different over years. However, in the year when the reproductive intensity was high, individual tree level floral sex allocation was size-dependent and the population level floral sex allocation was relatively female-biased. The female-biased floral sex allocation at the population level resulted from many gynoecious shoots (current-year shoots which have only female flowers). These results suggest that the floral sex allocation of Siberian alder was controlled not by changing the floral sex allocation of each current-year shoot, but by shifting the sex expression of current-year shoots from shoot-level monoecy to shoot-level gynomonoecy.     

Shoot population dynamics of persisting clones of<Emphasis Type="Italic"> Miscanthus sinensis</Emphasis> in the warm-temperate region of Japan

The population dynamics of annual shoots in four clonal patches of Miscanthus sinensis was surveyed in terms of clone persistence. Over a study period of 3 years, a stable net shoot number was attained through a balanced replacement of old shoots by tillering 2–3 times a year. The birth rate was significantly correlated with the average monthly temperature. This suggests that a warm climate advances the date of tillerings, and shoots become taller as they emerge earlier. Five cohorts were identified, corresponding to shoots that were born in spring, early summer, summer, autumn and early winter. The autumn cohorts were more numerous and had a greater longevity than the other cohorts; they were thus were best suited for overwintering and, consequently, maintaining the population from one generation to the next. The shoots of earlier cohorts grew too tall to survive the cold of winter, which might cause freezing injury, while later cohorts shoots excelled in overwintering because of their shortness. However, if the delayed shoots are very short, they will also have difficulty in surviving the early season of growth. Therefore, M. sinensis shoots have an optimum size for survival.     

Population structure and dynamics of an evergreen shade herb, Ainsliaea apiculata (Asteraceae), with special reference to herbivore effects

The population structure and dynamics of Ainsliaea apiculata, a forest understory evergreen herb widely distributed in Japan, was examined in a Chamaecyparis obtusa forest in Ibaraki Prefecture, central Japan (36°51N, 140°33E; 750 m a.s.l.). The mean population growth rate () calculated from the transition matrices for 4 years was 0.69 per year, predicting that the population size will decrease remarkably. There was a significant positive correlation between the survival of old leaves and the growth of new shoots in the following year. The shoots, especially new leaves, were damaged severely by herbivores (caterpillars of Leioptilus sp.). The survival rate of leaves formed in the previous spring to the next spring was remarkably low (41–54%). The growth of new shoots depended mainly on the reserves contained in old shoots, especially those in old leaves. New shoots of A. apiculata began to develop in spring, even though they were formed in autumn of the previous year. A defoliation experiment also showed that the removal of old shoots at the beginning of the growing season significantly inhibited the growth of new shoots. Damage to old shoots by herbivores severely influenced the growth and population dynamics of A. apiculata.     

Ramet size equalisation in a clonal plant,Phragmites australis

The influence of shading from older generations of dead culms (standing litter) on density, growth rate and development of size structure at the ramet level was investigated in a pure stand of Phragmites australis by experimental neutral shading of plots after removal of standing litter. Initial differences in height distribution between autumn and spring cohorts disappeared in the course of shoot growth. The Gini coefficients of shoot heights and estimated shoot weights indicated that the size structure of the shoots became more equal with increasing mean size in both shaded and unshaded plots. Relative growth rate for height (RHGR) and weight of individual shoots was negatively related to shoot size during the early and presumably storage-dependent growth period, suggesting a strong support for growth of smaller shoots. No etiolation was indicated by mean or maximum height in shaded and unshaded plots, or by the relationship between shoot height and weight. Mean shoot density was significantly lower in shaded than in unshaded plots in one of two shade treatment years. A regression model indicated a small but significant effect of shoot density on the approximately linear relationship between RHGR and the logarithm of height. The growth rate of small shoots was slightly larger at low than at high shoot density. Therefore, it is suggested that the shade from standing litter in P. australis stands can decrease shoot natality in the spring cohort, and thereby increase the support to fewer small shoots.     

Dynamics of cohorts of cladodes and related effects on reproduction in the shrub Retama sphaerocarpa in semi-arid south-eastern Spain

Changes in the size and age structure of the canopy of the leguminous shrub Retama sphaerocarpa in semi-arid south-eastern Spain were investigated by monitoring growth and survivorship of cladodes (photosynthetic stems) on marked shoots over a period of 26 months. Three basic morphological types of cladodes – long shoots, short shoots, and secondary short shoots – were distinguished.The canopy of the shrubs contained three annual cohorts of cladodes in spring and summer. The number and size of shoots produced each year was highly variable and was apparently related to the amount of rainfall during the preceding cool season. The spring cohort of 1994 produced only 37% of cladodes compared with 1993. Two cohorts of shoots were actually initiated in spring and late summer of each year, but the second cohort produced only 2–12% of the number of cladodes compared with the spring cohort. The proportions of the different cohorts in the canopy changed rapidly from April to August, but only slowly during the remainder of the year when only two annual cohorts remained after extensive litterfall in late summer. This late summer litterfall caused a substantial reduction in green canopy area (40–50%) which was achieved mainly be shedding of one year old cladodes. The life expectancy of cladodes decreased with increasing order of their morphological type from 850 ± 25 days in long shoots to 563 ± 4 days and 546 ± 9 days in short shoots and second order short shoots, respectively.Flowering and fruiting took place from May to July, almost exclusively on one year old cladodes, and coincided with the maximum development of the canopy. Flowering intensity was high in 1994, when individual shoots supported a mean number of approximately 150 flowers. Shoots produced an average of 12.6 ± 0.6 and 5.3 ± 1.0 fruits per shoot in 1993 and 1994, respectively. Most of the annual fruit crop (80–90%) was shed during litterfall in late summer. A proportion of 10–20% was retained in the canopy for up to 12 months, however, with some fruits persisting for more than 22 months.     

Individual size variation and population stability in a seasonal environment: a discrete-time model and its calibration using grasshoppers

Much recent literature is concerned with how variation among individuals (e.g., variability in their traits and fates) translates into higher-level (i.e., population and community) dynamics. Although several theoretical frameworks have been devised to deal with the effects of individual variation on population dynamics, there are very few reports of empirically based estimates of the sign and magnitude of these effects. Here we describe an analytical model for size-dependent, seasonal life cycles and evaluate the effect of individual size variation on population dynamics and stability. We demonstrate that the effect of size variation on the population net reproductive rate varies in both magnitude and sign, depending on season length. We calibrate our model with field data on size- and density-dependent growth and survival of the generalist grasshopper Melanoplus femurrubrum. Under deterministic dynamics (fixed season length), size variation impairs population stability, given naturally occurring densities. However, in the stochastic case, where season length exhibits yearly fluctuations, size variation reduces the variance in population growth rates, thus enhancing stability. This occurs because the effect of size variation on net reproductive rate is dependent on season length. We discuss several limitations of the current model and outline possible routes for future model development.     

Testing a new hypothesis: plant vigor and phylloxera distribution on wild grape in Arizona

Summary Longer, meaning more vigorous, shoots of a wild grape clone (Vitis arizonica) were more susceptible to attack by second and third generations of leaf-galling grape phylloxera,Daktulopsphaira vitifoliae, as the growing season progressed. Although there was no significant difference in mean shoot length between attacked and unattacked shoots within a clone at the beginning of shoot elongation, attacked shoots were significantly longer than unattacked shoots when elongation had ceased (P<0.01). Also, long attacked shoots had a significantly greater population of phylloxera galls than short attacked shoots (P<0.01) as the season progressed. The phylloxera population on long shoots increased rapidly while the population on short shoots remained the same. Longer shoots also produced significantly more axillary shoots than shorter shoots as the season progressed (P<0.001), and the number of axillary shoots accounted for 66 percent of the variance in number of attacked leaves on a shoot. Experimental evidence showed that there was a significantly greater percentage of available leaves attacked on long shoots than on short shoots (P<0.05) and the leaves on long shoots generally had a greater number of galls per leaf. The relationship between shoot length and probability of attack was also tested by comparing shoots lengths of 10 attacked clones and 10 unattacked clones at a second location. Mean shoot lengths of attacked clones were significantly longer than mean shoot lengths of unattacked clones (P<0.05), and mean shoot lengths of attacked shoots within a clone were significantly longer than unattacked shoots (P<0.001). Longer shoot length accounted for 81 percent of the variance in probability of attack. The reason for this pattern of attack was that long shoots produced newly expanding leaves over a longer time during the growing season and multivoltine phylloxera require undifferentiated tissue to initiate gall formation. Patterns of attack within a shoot were characterized by an uneven distribution of galls among leaves. This was due to development time between generations and the current availability of undifferentiated tissue at times of colonization. This study supports the hypothesis that some herbivore species are favored more by vigorous plants than by stressed plants.     

Cost and probability of flowering at the shoot level in relation to variability in shoot size within the crown of Vaccinium hirtum (Ericaceae)

Size-related variation in the cost and probability of flowering among shoots within a crown of Vaccinium hirtum was investigated to clarify patterns and regulation of flowering at the shoot-module level, below the level of the individual. The apices of previous-year shoots differentiated into current-year shoots vegetatively (vegetative branches) or became reproductive by developing inflorescences (reproductive branches). Length growth and fate of current-year shoots were determined, and the future potential for reproduction was estimated using a matrix model of shoot dynamics. Reproductive branches had fewer current-year shoots and shorter total shoot lengths and thus had a reduced potential for reproduction compared with vegetative branches, indicating the cost of flowering at the shoot level. This cost of flowering was higher in longer shoots. The probability of the initiation of flowering in a shoot increased with increasing shoot length in shorter shoots, reached a maximum in medium-sized shoots, and decreased in longer shoots. The size-related changes in the probability of flowering at the shoot level can be largely explained by the size-dependent changes in shoot-level resource availability and cost of flowering.     

火灾后兴安落叶松长短枝变化及其对生存的影响

研究了兴安落叶松的长短枝习性及火灾对其影响.结果表明,短枝在春季发叶迅速,而长枝的生长对兴安落叶松的枝条及树冠结构的形成起决定性作用,且在1个长枝上能形成10.5个短枝.中度火烧使兴安落叶松的树冠及枝条受到很大伤害,火烧可刺激1级侧枝上37%的短枝芽变成长枝,加速了火烧后兴安落叶松树冠结构的恢复,火后第3年兴安落叶松的短枝总量达到火前水平的98.46%.     

Annual and spatial variation in shoot demography associated with masting in Betula grossa: comparison between mature trees and saplings

Backgrounds and Aims

Shoot demography affects the growth of the tree crown and the number of leaves on a tree. Masting may cause inter-annual and spatial variation in shoot demography of mature trees, which may in turn affect the resource budget of the tree. The aim of this study was to evaluate the effect of masting on the temporal and spatial variations in shoot demography of mature Betula grossa.

Methods

The shoot demography was analysed in the upper and lower parts of the tree crown in mature trees and saplings over 7 years. Mature trees and saplings were compared to differentiate the effect of masting from the effect of exogenous environment on shoot demography. The fate of different shoot types (reproductive, vegetative, short, long), shoot length and leaf area were investigated by monitoring and by retrospective survey using morphological markers on branches. The effects of year and branch position on demographic parameters were evaluated.

Key Results

Shoot increase rate, production of long shoots, bud mortality, length of long shoots and leaf area of a branch fluctuated periodically from year to year in mature trees over 7 years, in which two masting events occurred. Branches within a crown showed synchronized annual variation, and the extent of fluctuation was larger in the upper branches than the lower branches. Vegetative shoots varied in their bud differentiation each year and contributed to the dynamic shoot demography as much as did reproductive shoots, suggesting physiological integration in shoot demography through hormonal regulation and resource allocation.

Conclusions

Masting caused periodic annual variation in shoot demography of the mature trees and the effect was spatially variable within a tree crown. Since masting is a common phenomenon among tree species, annual variation in shoot demography and leaf area should be incorporated into resource allocation models of mature masting trees.     

Growth Dynamics of Shoot Height and Foliage Structure of a Rhizomatous Perennial Herb, Polygonum cuspidatum

The growth dynamics of shoot populations of Polygonum cuspidatumwere investigated at the Houei crater (approx. 2380 m abovesea level) on the south-eastern slope of Mount Fuji. At thisstudy site, a genetic individual of this species produces apopulation of shoots in the form of a patch occupying a certainground area. Generally, genetic individuals are located awayfrom each other and hence there is little interaction betweenindividuals. A large-sized individual occupying 31·2m² ground area with shoots, a medium-sized individual (5·6m²) and a small-sized individual (1·4 m²) were selectedfor this study. In each individual, growth was investigatedat the shoot level. The results were analysed based on the diffusionmodel. Early in the growing season in 1990, there was littledifference in LAI (leaf area index) and shoot density betweenthe individuals. Shoots of the small- and medium-sized individualsshowed size-independent height growth, whilst those of the larger-sizedindividual showed size-dependent height growth. Consequently,small-sized shoots of the small- and the medium-sized individualshad greater RGRs of shoot height growth than those of the largeindividual at the early stage. As a result, in the small- andmedium-sized individuals, cv (coefficient of variance) and skewnessof shoot height decreased with time. Increases in cv and skewnessof shoot height were found in the large-sized individual. Thesize-independent growth pattern of shoot height in the small-and medium-sized individuals during early growing stages isdifferent from the growth pattern of non-clonal plant species,in which plant height growth is positively size-dependent. Theexistence of a regulatory mechanism of shoot height growth issuggested for the small- and medium-sized individuals. The foliagestructure of the large-sized individual was different from thatof the medium- and small-sized individuals. The foliage structureof small- and medium-sized individuals was similar to the theoretical"optimal foliage structure" of plants. In clonal plant species,a genetic individual occupies a certain ground area with itsshoots. Therefore, "optimal foliage structure" per unit groundarea brings about maximization of photosynthetic rate for agenetic individual, which is consistent with the maximizationof fitness at the level of the individual plant.Copyright 1994,1999 Academic Press Clonal plant species, diffusion model, growth regulatory mechanism, genetic individual, maximization of fitness     

Size-dependent mortality induces life-history changes mediated through population dynamical feedbacks

The majority of taxa grow significantly during life history, which often leads to individuals of the same species having different ecological roles, depending on their size or life stage. One aspect of life history that changes during ontogeny is mortality. When individual growth and development are resource dependent, changes in mortality can affect the outcome of size-dependent intraspecific resource competition, in turn affecting both life history and population dynamics. We study the outcome of varying size-dependent mortality on two life-history types, one that feeds on the same resource throughout life history and another that can alternatively cannibalize smaller conspecifics. Compensatory responses in the life history dampen the effect of certain types of size-dependent mortality, while other types of mortality lead to dramatic changes in life history and population dynamics, including population (de-)stabilization, and the growth of cannibalistic giants. These responses differ strongly among the two life-history types. Our analysis provides a mechanistic understanding of the population-level effects that come about through the interaction between individual growth and size-dependent mortality, mediated by resource dependence in individual vital rates.     

橄榄星室木虱的生活史和种群消长动态的研究

本研究了莆田市延寿村的橄榄星室木虱的生活史和种群消长动态。结果表明,橄榄星室木虱在莆田地区一年发生8代,世代重叠。卵、若虫(1—5龄)、成虫在1年中有6个发生高峰期,以秋梢期为全年雌成虫产卵、若虫发生最高峰,夏梢期是成虫羽化全年最高峰。其田间种群数量消长与橄榄抽梢期有着极为密切的关系,每一次抽梢期都带来一个产卵高峰期和低龄若虫发生高峰期,每一次抽梢都使虫口数量急尉上升,并出现高峰,其间也带来一个很高的种群增长率,待到新梢定型老化(枝梢生长后期)又使种群数量明显下降,而低龄若虫的发生和高峰期的出现,一般比产卵滞后5—10d。     

Competition between Shoots in Stands of Clonal Plants

Abstract Data on shoot turnover, shoot size distributions and individual shoot growth in stands of clonal plants are reviewed and compared with shoot density regulation in non-clonal plants. Shoots are the smallest units capable of independent existence in clonal as well as unitary plants and this comparison allows an investigation of the impact of integration and other factors on clonal shoot dynamics. Physiological integration, the capacity of clonal plants to exchange resources and growth substances between interconnected shoots, has long been held responsible for the ability of clonal plants to prevent shoot overproduction and for the general lack of density-dependent mortality and self-thinning. A review of published data leads to the conclusion that the effects of integration on shoot dynamics in clonal plants have been overestimated. Other characteristics such as the density-dependent control of meristem activity, the synchronization of shoot growth in spring and the maximum shoot size, seem more important for the deviating behaviour of shoot populations of clonal plants.     

Shoot tip culture and cryopreservation for eradication of Apple stem pitting virus (ASPV) and Apple stem grooving virus (ASGV) from apple rootstocks ‘M9’ and ‘M26’

This study attempted to eradicate Apple stem pitting virus (ASPV) and Apple stem grooving virus (ASGV) from virus‐infected in vitro shoots of apple rootstocks ‘M9’ and ‘M26’ using shoot tip culture and cryopreservation. In shoot tip culture, shoot tips (0.2 mm in length) containing two leaf primordia failed to show shoot regrowth. Although shoot regrowth rate was the highest in the largest shoot tips (1.0 mm in length) containing four leaf primordia, none of the regenerated shoots was virus‐free. Shoot tips (0.5 mm in length) containing two and three leaf primordia produced 100% and 10% of ASPV‐free shoots, respectively, while those (1.0 mm) containing four leaf primordia were not able to eradicate ASPV. ASGV could not be eradicated by shoot tip culture, regardless of the size of the shoot tips tested. In cryopreservation, shoot tips (0.5 mm in length) containing two leaf primordia did not resume shoot growth. Although 1.0‐mm and 1.5‐mm shoot tips gave similarly high ASPV‐free frequencies, the latter had much higher shoot regrowth rate than the former. Very similar results of shoot regrowth and virus eradication by shoot tip culture and cryopreservation were observed in both ‘M9’ and ‘M26’. Histological observations showed that only cells in upper part of apical dome and in leaf primordia 1–3 survived, while other cells were damaged or killed, in shoot tips following cryopreservation. Virus immunolocalization found ASPV was not detected in upper part of apical dome and leaf primordia 1 and 2, but was present in lower part of apical dome, and in leaf primordium 4 and more developed tissues in all samples tested. ASPV was also detected in leaf primordium 3 in about 16.7% and 13.3% samples tested in ‘M9’ and ‘M26’. ASGV was observed in apical dome and leaf primordia 1–6, leaving only a few top layers of cells in apical dome free of the virus. Different abilities of ASPV and ASGV to invade leaf petioles and shoot tips were also noted.     

黄花倒水莲生长与内源激素水平动态变化关系研究北大核心CSCD

为探索黄花倒水莲春梢生理生化特性的差异以及不同内源激素的变化规律,该文对黄花倒水莲春梢的生长动态进行监测,采用间接酶联免疫吸附法(ELISA)测定脱落酸(ABA)、生长素(IAA)、赤霉素(GA)、乙烯(ETH)和玉米素核苷(ZR)五种内源激素含量的动态变化,并对两者间的相关性进行分析。结果表明:(1)黄花倒水莲春梢生长发育过程可分为快速增长期(0~12 d)、生长转折期(16~20 d)和缓慢增长期(24~32 d)三个阶段。(2)内源激素ABA、GA、ETH和ZR含量在缓慢增长期显著高于快速增长期和生长转折期,IAA含量各时期差异较小。(3)春梢长、底部叶长和叶宽在快速增长期与ABA、GA、ETH和ZR含量呈负相关,且与ZR含量具有一定显著性,与IAA含量呈正相关;生长转折期,各指标与GA、ETH和ZR含量呈正相关,与GA含量具有一定显著性,与ABA含量呈负相关;缓慢增长期,各指标与五种内源激素含量均呈正相关,与IAA和ZR含量具有一定显著性。该研究结果为生产上利用外源激素调控黄花倒水莲春梢抽出以及生长提供了理论基础。     

辽东栎芽库统计:芽的命运

植物体是一个构件集合体,植物的枝系伸展可由芽库出生率、死亡率的统计学过程来分析。在东灵山地区,应用随机枝取样法调查了辽东栎芽的命运,并对其与枝长、叶数、果数等的关系进行了统计分析。结果表明：（1）辽东栎的芽或保持休眠状态,或死亡后脱落,或分化为营养枝、生殖枝（包括雄花枝、雄花序、雌花枝和两花枝）等;（2）不同生境中芽的命运不同,生活在林窗中的幼树上的芽分化为具有生殖功能的枝条的比例显著高于郁闭林中的幼树,而与成熟个体接近;（3）芽的命运还受其它因子的影响,如上层枝条上、或叶数多的长枝上的芽分化为生殖枝的可能性大于其它的芽,另外还发现结实枝的枝长、枝上叶数都明显高于非结实枝。     

慈竹母株大小对克隆生长的影响

 克隆生长在慈竹种群更新中占有重要地位。本文以基径和生物量两个指标同时衡量慈竹(Neosinocalamus affinis)的母株大小,并分析了母株大小对新竹笋产生、竹笋大小和根茎大小的影响。结果表明：1）慈竹的成竹基径与一级母株基径、二级母株基径以及与2龄和3龄母株平均单株生物量呈正相关,但是成竹基径随一级母株基径增加比随二级母株基径增加而增加的速率快得多;2）慈竹母株大小与各样方中出笋数、活笋数和死笋数无显著的正相关;3）发笋母株的基径显著大于未发笋母株,但发一个笋母株与发两个以上笋母株的基径无显著差异;4）母株基径、2龄和3龄母株平均单株生物量都与根茎的长度和粗度呈显著正相关,且竹笋基径与根茎粗度也呈显著的正相关。母株大小对慈竹竹笋的影响是通过影响根茎实现的。总之,慈竹的克隆生长在个体水平受母株大小制约。     

Release of phylogenetic constraints through low resource heterogeneity: the case of gall-inducing sawflies

Abstract. 1. A group of six unusual sawfly species, which do not conform to the phylogenetic constraints hypothesis as it has been applied to sawflies, was examined in natural populations. All species were in the genus Pontania (Hymenoptera: Tenthredinidae), which induce galls on leaves of willow species (Salicaceae). An understanding of these non‐conformist species was important as a test of the validity of the general hypothesis. 2. The six species of sawfly, Pontania mandshurica, P. cf. arcticornis, P. aestiva, P. arcticornis, P. pacifica, and P. nr. pacifica, showed no oviposition preference for long, vigorous shoots, in contrast to 37 documented tenthredinid species that have demonstrated such a preference. Rather, the non‐conformist species attacked the shortest shoot length classes more frequently and larval establishment in galls was successful. 3. The evident escape from the phylogenetic constraint, which commonly limits sawfly attack to the most vigorous shoots in a willow population, resulted from low apparent heterogeneity of the resources exploited by these Pontania species. At the time of female oviposition, shoots and leaves were too uniform to allow discrimination by females among shoot length classes, resulting in random, or near random attack of shoots. 4. The unusual relative uniformity of resources to which sawflies were exposed resulted from several characteristics. (1) Females emerged early relative to shoot growth phenology, making discrimination among shoot length and vigour difficult or impossible. (2) Low heterogeneity in leaf length resulted in resource similarity independent of shoot length. (3) Abscission of leaves occurred after emergence of larvae from leaf galls so that differential abscission of leaves in relation to shoot length became irrelevant. (4) In some cases, low variance in shoot lengths was evident in old ramets lacking long, vigorous shoots. Probably as a result of low resource heterogeneity, larvae survived well across all shoot length classes, revealing no ovipositional preference and larval performance linkage related to the exploitation of the longest shoot length classes in a population of willows, as in the conformist species. Therefore, larval survival did not provide positive feedback on female preferential behaviour for long shoots, as in the conformist species studied.