Communities of insect herbivores foraging on saplings versus mature trees of Pourouma bicolor (Cecropiaceae) in Panama

The arthropod fauna of 25 saplings and of three conspecific mature trees of Pourouma bicolor (Cecropiaceae) was surveyed for 12 months in a tropical wet forest in Panama, with particular reference to insect herbivores. A construction crane erected at the study site provided access to tree foliage in the upper canopy. A similar area of foliage (ca. 370 m²) was surveyed from both saplings and trees, but samples obtained from the latter included 3 times as much young foliage as from the former. Arthropods, including herbivores and leaf-chewing insects with a proven ability to feed on the foliage of P. bicolor were 1.6, 2.5 and 2.9 times as abundant on the foliage of trees as on that of saplings. The species richness of herbivores and proven chewers were 1.5 (n=145 species) and 3.5 (n=21) times higher on trees than on saplings, respectively. Many herbivore species preferred or were restricted to one or other of the host stages. Host stage and young foliage area in the samples explained 52% of the explained variance in the spatial distribution of herbivore species. Pseudo-replication in the two sampling universes, the saplings and trees studied, most likely decreased the magnitude of differences apparent between host stages in this forest. The higher availability of food resources, such as young foliage, in the canopy than in the understorey, perhaps combined with other factors such as resource quality and enemy-free space, may generate complex gradients of abundance and species richness of insect herbivores in wet closed tropical forests.     

Tree recovery and seed dispersal by birds: Comparing forest, agroforestry and abandoned agroforestry in coastal Ecuador

We used a highly replicated study to examine vegetation characteristics between patches of intervened forest, abandoned agroforestry systems with coffee and actively managed agroforestry systems with coffee in a tropical landscape. In all habitats, plant structural characteristics, individual abundance, species richness and composition were recorded for the three plant size classes: adult trees, saplings and seedlings. Furthermore, bird species richness and composition, and seeds dispersed by birds were recorded. Tree abundance was higher in forest habitats while saplings and seedlings were more abundant in abandoned coffee sites. Although species richness of adult trees was similar in the three habitats, species richness of saplings and seedlings was much higher in forest and abandoned coffee than in managed coffee sites. However, in spite of their relatively low species richness, managed coffee sites are an important refuge for tree species common to the almost disappeared mature forest in the area. Floristic similarity for adult trees was relatively low between land use types, but clearly higher for seedlings, indicating homogenizing processes at the landscape level. More than half of the saplings and seedling were not represented by adults in the canopy layer, suggesting the importance of seed dispersal by birds between habitats. Our results show that each of the studied ecosystems plays a unique and complementary role as seed source and as habitat for tree recovery and tree diversity.     

The assessment of arboreal insect fauna: comparisons of knockdown sampling and faunal lists

Abstract. 1. A comparison is made between the fauna of six British tree species sampled by pyrethrum knockdown and the faunal lists in the literature for the same tree species.
2. Conspecific trees vary both in abundance of arthropods and their proportional distribution across taxa, but there are important overriding differences between tree species.
3. The percentage similarity in faunal composition between tree species reflects the ecological specificity of the arthropod groups used for the comparison.
4. The similarity in species composition between tree species is least for phytophages, the guild most closely associated with particular tree species, The two species of Salix are most similar in their fauna for most guilds.
5. About 40% of the entirely phytophagous species in the faunal lists for native trees were found in the knockdown samples.
6. The proportion of individuals of predominantly phytophagous taxa collected that belong to the relevant faunal lists ranges from 0.39 to 0.99.
7. Those species found in the knockdown samples which are not included in faunal lists none the less contribute to the trophic web of the tree.
8. The relative species richness of arboreal faunas assessed from knockdown samples parallels that derived from faunal lists.
9. The two approaches to the categorization of arboreal faunas, knockdown sampling and faunal lists, provide comparable data.     

Recovery of Plant Species Richness and Composition in an Abandoned Forest Settlement Area in Kenya

Cultivation of annual crops in the initial stage of reforestation has been commonly practiced in the tropics. In recent decades, however, cultivation of such areas has been discontinued, resulting in widespread abandoned settlements. In this article we used a former forest village settlement in Kenya, which had been cleared, cultivated and then abandoned, to study how natural vegetation recovers after such disturbances. Species richness, abundance, and composition of tree seedlings, saplings, adult trees, shrubs, and herbs were recorded in different zones, from a heavily degraded zone in the center of the settlement, through less disturbed transition zones (TZs), and in the surrounding secondary forest (SF). Species richness and abundance of tree seedlings, saplings, and adult trees increased gradually from the heavily degraded zone to the SF, whereas shrub and herb richness were the same for TZs and SF and abundance was lowest in the SF. Total species richness was highest in the SF. Some pioneer tree species were highly associated with the TZs, whereas sub‐canopy tree species were associated with the SF. A group of tree species were not particularly associated with any of the four zones. Thus, these species might have good potential as restoration species. The results of our study contribute to the knowledge of natural regeneration in general, and of individual species characterizing the different stages of recovery of abandoned settlements in particular. Such information is urgently needed in designing ecologically sound management strategies for restoring abandoned forest settlements in tropical areas.     

Comparison of Herbivores and Herbivory in the Canopy and Understory for Two Tropical Tree Species1

The Janzen–Connell model of tropical forest tree diversity predicts that seedlings and young trees growing close to conspecific adults should experience higher levels of damage and mortality from herbivorous insects, with the adult trees acting as either an attractant or source of the herbivores. Previous research in a seasonal forest showed that this pattern of distance‐dependent herbivory occurred in the early wet season during the peak of new leaf production. I hypothesized that distance‐dependent herbivory may occur at this time because the new foliage in the canopy attracts high numbers of herbivores that are limited to feeding on young leaves. As a consequence, seedlings and saplings growing close to these adults are more likely to be discovered and damaged by these herbivores. In the late wet season, when there is little leaf production in the canopy, leaf damage is spread more evenly throughout the forest and distance dependence disappears. I tested three predictions based on this hypothesis: (1) the same species of insect herbivores attack young and adult trees of a given plant species; (2) herbivore densities increase on adult trees during leaf production; and (3) herbivore densities in the understory rise during the course of the wet season. Censuses were conducted on adults and saplings of two tree species, raribea asterolepis and Alseis blackiana. Adults and saplings of both species had largely the same suite of chewing herbivore species. On adults of Q. asterolepis, the density of chewing herbivores increased 6–10 times during leaf production, but there was no increase in herbivore density on adults of A. blackiana. Herbivore densities increased 4.5 times on A. blackiana saplings and 8.9 times on Q. asterolepis saplings during the wet season, but there were no clear trends on the adults of either species. These results suggest that the potential of adult trees as a source of herbivores on saplings depends on the value of new leaves to a tree species' herbivores, which may differ across tree species.     

Patterns of tree replacement: canopy effects on understory pattern in hemlock-northern hardwood forests

The effect of canopy trees on understory seedling and sapling distribution is examined in near-climax hemlock-northern hardwood forests in order to predict tree replacement patterns and assess compositional stability. Canopy trees and saplings were mapped in 65 0.1-ha plots in 16 tracts of old-growth forests dominated by Tsuga canadensis, Acer saccharum, Fagus grandifolia, Tilia americana, and Betula lutea in the northeastern United States. Seedlings were tallied in sub-plots. Canopy influence on individual saplings and sub-plots was calculated, using several indices for canopy species individually and in total. For each species sapling and seedling distributions were compared to those distributions expected if saplings were located independently of canopy influence. Non-random distributions indicated that sapling and seedling establishment or mortality were related to the species of nearby canopy trees. Hemlock canopy trees discriminate against beech and maple saplings while sugar maple canopy favors beech saplings relative to other species. Basswood canopy discourages growth of saplings of other species, but produces basal sprouts. Yellow birch saplings were rarely seen beneath intact canopy. Since trees in these forests are usually replaced by suppressed seedlings or saplings, canopy-understory interactions should influence replacement probabilities and, ultimately, stand composition. I suggest that hemlock and basswood tend to be self-replacing, maple and beech tend to replace each other, and birch survives as a fugitive by occupying occasional suitable gaps. This suggests that these species may co-exist within stands for long periods with little likelihood of successional elimination of any species. There is some suggestion of geographical variation in these patterns.     

海南岛热带低地雨林刀耕火种弃耕地自然恢复过程中的群落构建

研究群落构建机制是群落生态学的一个重要目标, 群落动态过程中的构建规律对于了解群落演替机理有重要的作用。该文以海南岛刀耕火种干扰后自然恢复的10 hm ²热带低地雨林为研究对象, 通过比较不同恢复阶段的次生林(15年、30年和60年)和老龄林在幼苗、幼树和成年树群落的物种组成, 揭示次生演替过程中的群落构建规律。研究结果表明, 老龄林中不同径级群落的物种多样性及不同径级间的物种相似度显著高于各恢复阶段的次生林, 但优势种在群落中的比例低于各恢复阶段的次生林。随着自然恢复过程的进行, 次生林群落物种组成与老龄林的相似性也逐渐增大, 支持演替平衡理论。所有恢复阶段样地中幼苗的个体、物种丰富度和基于多度涵盖估计量(ACE)都低于幼树和成年树群落, 幼苗层物种组成与幼树、成年树也有较大差异, 说明新增到幼苗群落可能是一个难于预测的过程。研究结果说明了确定过程和随机过程共同决定了次生演替的群落构建。     

Insect herbivores associated with Baccharis dracunculifolia (Asteraceae): responses of gall-forming and free-feeding insects to latitudinal variation

The spatial heterogeneity hypothesis has been invoked to explain the increase in species diversity from the poles to the tropics: the tropics may be more diverse because they contain more habitats and micro-habitats. In this paper, the spatial heterogeneity hypothesis prediction was tested by evaluating the variation in richness of two guilds of insect herbivores (gall-formers and free-feeders) associated with Baccharis dracunculifolia (Asteraceae) along a latitudinal variation in Brazil. The seventeen populations of B. dracunculifolia selected for insect herbivores sampling were within structurally similar habitats, along the N-S distributional limit of the host plant, near the Brazilian sea coast. Thirty shrubs were surveyed in each host plant population. A total of 8 201 galls and 864 free-feeding insect herbivores belonging to 28 families and 88 species were sampled. The majority of the insects found on B. dracunculifolia were restricted to a specific site rather than having a geographic distribution mirroring that of the host plant. Species richness of free-feeding insects was not affected by latitudinal variation corroborating the spatial heterogeneity hypothesis. Species richness of gall-forming insects was positively correlated with latitude, probably because galling insect associated with Baccharris genus radiated in Southern Brazil. Other diversity indices and evenness estimated for both gall-forming and free feeding insect herbivores, did not change with latitude, suggesting a general structure for different assemblages of herbivores associated with the host plant B. dracunculifolia. Thus it is probable that, insect fauna sample in each site resulted of large scale events, as speciation, migration and coevolution, while at local level, the population of these insects is regulated by ecological forces which operate in the system.     

Arthropod faunal similarity of Bornean rain forest trees

ABSTRACT. 1. Arthropod samples, collected by insecticide fogging ten Bornean lowland rain forest trees, were sorted to species and used to study some of the determinants of faunal similarity of these trees.
2. Similarity indices were calculated between pairs of trees for guilds of beetles, beetle families and for different orders and other families of insects.
3. Multiple regression analyses of five independent variables of the trees (taxonomic similarity, distance apart, vertical canopy overlap, similarity in tree height, epiphytic load) were carried out against these similarity indices.
4. In eight of the eighteen insect groups analysed, taxonomic similarity of the trees is the most important variable affecting their species composition, accounting for a maximum of 29.4% of the variation.
5. For the Homoptera, Gryllidae, Anthicidae, Chrysomeloidea and scavengers, distance between the trees and the similarity of the trees'epiphyte load have a greater effect on their faunal similarities than taxonomic similarity of the trees.
6. The maximum variation accounted for by variables with significant T ratios was 38.6% in the Anthicidae. In four groups, the Formicidae, Heteroptera, Galerucinae and Corylophidae, none of the variables was significant.
7. These data may support the view that for many insect groups there is less host-specificity in the tropics than in temperate regions.     

Importance of functional traits and regional species pool in predicting long-distance dispersal in savanna ecosystems

Long-distance dispersal (LDD) of plants is difficult to measure but disproportionately important for various ecological and evolutionary processes. Dispersal of seeds of gallery-forest trees in savanna provides an opportunity for the study of colonisation processes and species coexistence driven by LDD. Investigations were carried out on 91 isolated trees along four gallery forests sampled in the Biosphere Reserve of Pendjari, Benin. The abundance of adult trees within nearest gallery forest was combined with functional traits (species maximum height, seed weight, morphological adaptation for dispersal by wind, water, birds and mammals) to explain the floristic composition of forest seedlings and saplings under isolated trees and in savanna. Stepwise negative binomial regression was used to identify the most significant variables explaining abundance of seedlings and saplings beneath isolated trees and in savanna and then derive colonisation from seedlings and persistence from saplings. The maximum height of species and seed weight explained the highest proportion of variance in species colonisation. Morphological dispersal syndromes by wind and birds had poor explanatory importance. Species rare in gallery forest had higher potential to colonise new environments through LDD whilst abundant species had higher persistence abilities. Contrary to the predictions of the seedling-size effect, small-seeded species dominated the sapling stage. The findings revealed the strong dependence of LDD and subsequent colonisation and persistence processes on species traits specialised for a variety of dispersal vectors. They also suggest that LDD towards isolated trees established far away from gallery forest can be difficult.     

Spatio-temporal variation in Lepidopteran larval assemblages associated with oak, Quercus crispula: the importance of leaf quality

Abstract.  1. Lepidoptera larval abundance and diversity in the canopies of oak ( Quercus crispula ) trees and saplings were surveyed in a cool-temperate, deciduous broadleaf forest in northern Japan.
2. In general, newly developed leaves were soft, rich in water and nitrogen, and low in tannin, whereas they became tough, poor in water and nitrogen, and high in tannin as the season proceeded. Leaf quality also varied among forest strata, such variations resulting in seasonal and among-strata differences in the structure of the Lepidoptera larval assemblage.
3. The greater Lepidoptera larval abundance and species richness may related to the higher leaf quality on spring foliage compared with summer foliage. On the other hand, diversity (Shannon's H' ) and evenness (Pielou's J' ) were greater on summer foliage than on spring foliage. Strengthened defences of the host plants against herbivory may cause these differences by filtering the larvae of Lepidoptera species and by constraining the super-dominance of a few species on summer foliage.
4. Canonical Correspondence Analysis (CCA) ordination also revealed a stratified structure of the Lepidoptera larval assemblage in the forest. In both spring and summer, the assemblage composition was more similar between sunlit and shaded canopies than between canopies and saplings. Such assemblage stratification was highly correlated with toughness and tannin content (in spring and summer) or water content (in summer).
5. This study emphasised the importance of spatio-temporal variations in leaf quality, even within the same host plant species, for promoting herbivore diversity in forests.     

Community structure of arboreal caterpillars within and among four tree species of the eastern deciduous forest

Abstract.  1. A seasonally replicated experimental design was used to address the question of how differences within and among host tree species affect arboreal caterpillar communities.
2. Seasonal variation influenced caterpillar community composition most significantly, and the similarity among caterpillar assemblages did not necessarily follow the pattern of phylogenetic relatedness among host trees.
3. Species richness and abundance of caterpillars were higher on oaks and maples than on American beech. Diversity partitioning models revealed that β diversity was only occasionally greater or less than expected by chance alone.
4. When β diversity was significant, values tended to be greater than expected by chance among replicate trees within each species and lower than expected by chance among the four tree species.
5. Differences among trees appeared important for determining patterns of species presence/absence for rare species and influencing patterns of species dominance within caterpillar assemblages. Differences among tree species had a significant effect on overall lepidopteran community composition and mean species diversity (i.e. α diversity).
6. Because β diversity of caterpillars among host trees was lower than expected by chance, host specificity within the Lepidoptera may be less prevalent than thought previously.     

Colonization of a host tree by herbivorous insects under a changing climate

Climate warming has been predicted to increase the abundance of herbivorous insects. Together with concurrent poleward shifts in many insect species this may increase herbivore pressure on plants. However, the manner in which plants at higher latitudes become colonized by herbivorous insects in the future is unknown. We established a translocation experiment using 26 micropropagated silver birch Betula pendula genotypes from six populations originating from 60°N to 67°N, to study the susceptibility of the translocated birches to local herbivores. The birches were planted at three different latitudes in Finland (60°N, 62°N and 67°N). We studied the effect of source population and latitudinal translocation on herbivore density, species richness, and community composition among the genotypes growing in the same environmental conditions in two years; 2011 and 2012. The source population explained the variation in the herbivore density only in 2012, whereas latitudinal translocation did not affect herbivore density. Variation in species richness was not explained by the source population or by the latitudinal translocation. At two of the study sites, the similarity of the herbivore communities among the populations decreased with increasing latitudinal distance of the source populations, possibly because birch populations that grow geographically closer to each other are genetically more similar, and therefore support a more similar composition of the arthropod community. All birch genotypes were colonized by local herbivores, suggesting that as herbivores shift their ranges polewards, they are able to colonize novel host‐plant genotypes. This enables compositional changes in insect communities on their host plants in the future, which in turn, might affect total herbivory and eventually, plant growth.     

Foliage value,apparency and defence investment in birch seedlings and trees

Summary Two factors determining plant anti-herbivore defence investment fitness loss due to herbivory and the probability of herbivory occurring in the field were quantified for birch seedlings and trees. Fitness loss due to defoliation (assumed to be related to loss of growth increment compared to controls) appeared to be greater in seedlings compared to trees, but the result was equivocal. In contrast, seedling foliage at the field site — a typical habitat for birch — suffered much less natural defoliation than tree foliage, suggesting that seedlings are markedly less apparent to most birch herbivores than trees. This low apparency should result in lower investment in anti-herbivore defences by seedlings compared to trees — and being a strong effect, should outweigh the possibly greater growth loss suffered by seedlings, which in isolation would tend to increase their optimum defence investment compared to trees. This prediction was tested using palatability trials with a wide range of common birch herbivores and by direct quantification of anti-herbivore defences. Problems and assumptions inherent in these approaches are discussed, but it seems that birch seedlings are genuinely unapparent to herbivores, and consequently do not need the degree of defence investment required by trees.     

Patterns of composition and species richness of crustaceans and aquatic insects along environmental gradients in Mediterranean water bodies

Differences in the dynamics of ecological processes between Mediterranean and colder temperate aquatic systems could imply different patterns in faunal communities in terms of composition and biodiversity (i.e. species richness and rarity). In order to identify some of these patterns the crustacean and aquatic insect composition and biodiversity of four water body types, classified according to their salinity and water permanence, were compared. Moreover, the relationships between species richness and water, pond and landscape variables were analysed. A total number of 91 water bodies located throughout Catalunya (NE Iberian Peninsula) were sampled. Three species assemblages were observed: one for permanent freshwaters, another for temporary freshwaters, and a third one for saline waters (SW), since permanent and temporary saline water bodies had similar composition. Differences in salinity were associated with proportion of crustaceans versus insects and with singularity. Thus, saline ponds had a higher proportion of crustaceans, and lower values of singularity. Conductivity was significantly related to total (crustaceans plus insects) richness, and also related to insect richness. The main difference between the models obtained for crustacean species richness and insect species richness is the significance of landscape variables in the latter, and this fact could be related to the different dispersion types of these two faunal groups: active for insects versus passive for crustaceans. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Guest editors: R. Céréghino, J. Biggs, B. Oertli & S. Declerck The ecology of European ponds: defining the characteristics of a neglected freshwater habitat     

古田山不同干扰程度森林的群落恢复动态

森林采伐后次生林的恢复过程对于生物多样性的保护和生态系统功能的重建具有重要意义。作者以古田山不同干扰程度的12个1 ha 森林样地为研究对象, 运用群落多元统计方法, 探讨了自然恢复过程中森林群落组成及物种多样性的动态变化及趋势。结果表明: 不同恢复阶段森林样地的群落组成存在显著性差异, 而同一恢复阶段的样地具有高度的相似性。物种丰富度随恢复进程有增加的趋势, 但各阶段差异并不显著; 物种均匀度除人工林较低以外, 其他恢复阶段之间无显著性差异。不同恢复阶段研究样地的群落组成及物种多样性的差异主要存在于林冠层。灌木及更新层具有各自的指示种, 人工林的指示种为落叶灌木或阳性乔木, 幼龄次生林的指示种为常绿灌木或小乔木, 老次生林的指示种为亚乔木层常绿树种, 老龄林的指示种为林冠层树种。上述结果表明古田山不同人为干扰程度森林群落的物种多样性具有较强的自我恢复能力。尽管物种组成难以预测, 但处于同一恢复阶段的森林, 其幼树的生活型组成呈现出一致的变化趋势。     

Seedling and Sapling Dynamics of Treefall Pits in Puerto Rico1

Seedling and sapling dynamics in a Puerto Rican rain forest were compared between forest understory and soil pits created by the uprooting of 27 trees during Hurricane Hugo. Soil N and P, organic matter, and soil moisture were lower and bulk densities were higher in the disturbed mineral soils of the pits than in undisturbed forest soils ten months after the hurricane. No differences in N and P levels were found in pit or forest soils under two trees with N–fixing symbionts (Inga laurina and Ormosia krugii) compared to soils under a tree species without N–fixing sym–bionts (Casearia arborea), but other soil variables (Al, Fe, K) did vary by tree species. Forest plots had greater species richness of seedlings (<10 cm tall) and saplings (10–100 cm tall) than plots in the soil pits (and greater sapling densities), but seedling densities were similar between plot types. Species richness and seedling densities did not vary among plots associated with the three tree species, but some saplings were more abundant under trees of the same species. Pit size did not affect species richness or seedling and sapling densities. Recruitment of young Cecropia schreberiana trees (>5 m tall) 45 months after the hurricane was entirely from the soil pits, with no tree recruitment from forest plots. Larger soil pits had more tree recruitment than smaller pits. Defoliation of the forest by the hurricane created a large but temporary increase in light availability. Recruitment of C. schreberiana to the canopy occurred in gaps created by the treefall pits that had lower soil nutrients but provided a longer–term increase in light availability. Treefall pits also significantly altered the recruitment and mortality of many understory species in the Puerto Rican rain forest but did not alter species richness.     

Plant quality and predation risk mediated by plant ontogeny: consequences for herbivores and plants

Bottom‐up and top‐down impacts on herbivores can be influenced by plant productivity, structural complexity, vigor and size. Although these traits are likely to vary with plant development, the influence of plant ontogeny on the relative importance of plant quality (i.e. bottom‐up forces) and predation risk (i.e. top‐down forces) has been the focus of little previous investigation. We evaluated the role of plant ontogeny for the relative importance of bottom‐up and top‐down forces on insect herbivore abundance, species richness, and species diversity attacking the tropical tree Casearia nitida. We also quantified the cascading effects on herbivory, growth and reproduction of this plant species. Plant quality traits (nitrogen and phenolic compounds) were assessed in saplings and reproductive trees. Bottom‐up forces were manipulated by fertilizing plants from both ontogenetic stages. Top‐down forces were manipulated by excluding insectivorous birds from saplings and reproductive trees. Plant ontogeny influenced foliage quality in terms of total phenolics, which were in greater concentration in reproductive trees than in saplings; however, it did not influence bottom‐up forces as modified by fertilization. Bird exclusion increased herbivore density with the same magnitude on both stages. Ontogeny influenced species diversity, which was greater in reproductive trees than in saplings, and also influenced treatment impacts on species richness and diversity. Although top‐down forces increased herbivory equally on plants of each ontogenetic stage, the two stages showed different overcompensation responses to increased damage: caged saplings produced greater leaf biomass than non‐caged saplings, whereas caged trees increased in height proportionally more than non‐caged trees. In sum, plant ontogeny influenced the impact of bird predation on herbivore density, species richness, and species diversity, and the growth variables affected by increased damage in caged plants. We suggest that plant ontogeny can contribute to some extent to the influence of plant quality and the third trophic level on herbivores in this system.     

Relationship between plant development, tannin concentration and insects associated with Copaifera langsdorffii (Fabaceae)

Plant development is the main factor that determines the insect-ontogeny interaction, since it leads to variations in resource quality and availability. The aim of this study was to test the hypothesis that plant development and varying tannin concentration leads to changes in species richness, abundance and composition of ants, free-feeding herbivores and galling insects associated with Copaifera langsdorffii (Fabaceae). The plant ontogeny and tannin concentration effects on insects were tested on 60 individuals with height varying from 0.9 to 11.0 m. A positive correlation was observed for tree height and species richness and abundance of ants, free-feeding and galling insects. In contrast, we did not find a significant relation between leaf tannin concentration and plant height, or richness and abundance of the different insect guilds. The assemblage of ants (composition of species) did not change between saplings and adults of C. langsdorffii. However, the assemblage of free-feeding herbivores and galling insects varied between the two development stages studied. The present study reveals an ontogenetic succession pattern for herbivore insects along the C. langsdorffii growth, probably due to both indirect and direct benefits from the host plant architecture and quality. Those plants with more complex architectures should support a wider diversity of insects, since they present higher number of sites for egg laying, housing, feeding and better environmental conditions. This is the first work to investigate the host plant ontogeny effect on insects in Cerrado “Savanna” vegetation. The pattern described, along with other previous studies, suggests a vast occurrence of ontogenetic succession in tropical areas.     

Seasonal patterns in species richness of herbivores: Macrolepidopteran larvae on Finnish deciduous trees

Abstract. 1. The seasonal distribution of macrolepidopteran species richness on Finnish deciduous trees vaned from positively skewed (peak in spring) to negatively skewed (peak in autumn).
2. The skewness values of species richness had a significant negative correlation ( r = - 0.98) with the duration of the seasonal shoot-growth period of the tree species.
3. Trees which complete their shoot growth early in the season ( Quercus type) produce new leaves only during spring, while trees whose shoot growth continues to autumn ( Populus type) do so throughout the summer.
4. Consequently, there is a difference in the number of available resources in the late summer foliage of different tree species, Trees ceasing leaf production early such as oak ( Quercus robur ) and bird cherry ( Prunus padus ) have one major resource type (mature leaves) in late-season foliage while trees like birches and alders have two Ooung and mature leaves).
5. Because young leaves formed late in the season are preferred to mature ones by some species of herbivores and because other species prefer mature leaves at the same time, the species richness of Populus-type trees is higher later in the season than the species richness of Quercus-type of trees, which have just one type of resource available.