Simulated Herbivory Affects the Volatile Emissions of Oak Saplings, while Neighbourhood Affects Flavan-3-ols Content of Their Leaves.

To what extent particular plant defences against herbivorous insects are constitutive or inducible will depend on the costs and benefits in their neighbourhood. Some defensive chemicals in leaves are thought to be costly and hard to produce rapidly, while others, including volatile organic compounds that attract natural enemies, might be cheaper and can be released rapidly. When surrounding tree species are more closely related, trees can face an increased abundance of both specialist herbivores and their parasitoids, potentially increasing the benefits of constitutive and inducible defences. To test if oaks (Quercus robur) respond more to herbivore attacks with volatile emission than with changes in leaf phenolic chemistry and carbon to nitrogen ratio (C: N), and whether oaks respond to the neighbouring tree species, we performed an experiment in a forest in Poland. Oak saplings were placed in neighbourhoods dominated by oak, beech, or pine trees, and half of them were treated with the phytohormone methyl jasmonate (elicitor of anti-herbivore responses). Oaks responded to the treatment by emitting a different volatile blend within 24 h, while leaf phenolic chemistry and C: N remained largely unaffected after 16 days and multiple treatments. Leaf phenolics were subtly affected by the neighbouring trees with elevated flavan-3-ols concentrations in pine-dominated plots. Our results suggest that these oaks rely on phenols as a constitutive defence and when attacked emit volatiles to attract natural enemies. Further studies might determine if the small effect of the neighbourhood on leaf phenolics is a response to different levels of shading, or if oaks use volatile cues to assess the composition of their neighbourhood.

Ectophagous folivores do not profit from rich resources on phylogenetically isolated trees.

Resource use by consumers across patches is often proportional to the quantity or quality of the resource within these patches. In folivores, such proportional use of resources is likely to be more efficient when plants are spatially proximate, such as trees forming a forest canopy. However, resources provided by forest-trees are often not used proportionally. We hypothesised that proportional use of resources is reduced when host trees are isolated among phylogenetically distant neighbours that mask olfactory and visual search cues, and reduce folivore movement between trees. Such phylogenetically distant neighbourhoods might sort out species that are specialists, poor dispersers, or have poor access to information about leaf quality. We studied individual oaks, their leaf size and quality, their folivory and abundance of folivores (mostly Lepidopteran ectophages, gallers and miners), and parasitism of folivores. We found that leaf consumption by ectophages hardly increased with increasing leaf size when host trees were phylogenetically isolated. We found a similar effect on host use by parasitoids in 1 year. In contrast, we found no consistent effects in other folivore guilds. Relative abundances of specialists and species with wingless females declined with phylogenetic isolation. However, resource use within each of these groups was inconsistently affected by phylogenetic isolation. We suggest that phylogenetic isolation prevents ectophages from effectively choosing trees with abundant resources, and also sorts out species likely to recruit in situ on their host tree. Trees in phylogenetically distant neighbourhoods may be selected for larger leaves and greater reliance on induced defences.

Predictability of temporal variation in climate and the evolution of seasonal polyphenism in tropical butterfly communities.

Phenotypic plasticity in heterogeneous environments can provide tight environment-phenotype matching. However, the prerequisite is a reliable environmental cue(s) that enables organisms to use current environmental information to induce the development of a phenotype with high fitness in a forthcoming environment. Here, we quantify predictability in the timing of precipitation and temperature change to examine how this is associated with seasonal polyphenism in tropical Mycalesina butterflies. Seasonal precipitation in the tropics typically results in distinct selective environments, the wet and dry seasons, and changes in temperature can be a major environmental cue. We sampled communities of Mycalesina butterflies from two seasonal locations and one aseasonal location. Quantifying environmental predictability using wavelet analysis and Colwell's indices confirmed a strong periodicity of precipitation over a 12-month period at both seasonal locations compared to the aseasonal one. However, temperature seasonality and periodicity differed between the two seasonal locations. We further show that: (a) most females from both seasonal locations synchronize their reproduction with the seasons by breeding in the wet season but arresting reproduction in the dry season. In contrast, all species breed throughout the year in the aseasonal location and (b) species from the seasonal locations, but not those from the aseasonal location, exhibited polyphenism in wing pattern traits (eyespot size). We conclude that seasonal precipitation and its predictability are primary factors shaping the evolution of polyphenism in Mycalesina butterflies, and populations or species secondarily evolve local adaptations for cue use that depend on the local variation in the environment.

Quantifying the effects of species traits on predation risk in nature: A comparative study of butterfly wing damage.

Evading predators is a fundamental aspect of the ecology and evolution of all prey animals. In studying the influence of prey traits on predation risk, previous researchers have shown that crypsis reduces attack rates on resting prey, predation risk increases with increased prey activity, and rapid locomotion reduces attack rates and increases chances of surviving predator attacks. However, evidence for these conclusions is nearly always based on observations of selected species under artificial conditions. In nature, it remains unclear how defensive traits such as crypsis, activity levels and speed influence realized predation risk across species in a community. Whereas direct observations of predator-prey interactions in nature are rare, insight can be gained by quantifying bodily damage caused by failed predator attacks. We quantified how butterfly species traits affect predation risk in nature by determining how defensive traits correlate with wing damage caused by failed predation attempts, thereby providing the first robust multi-species comparative analysis of predator-induced bodily damage in wild animals. For 34 species of fruit-feeding butterflies in an African forest, we recorded wing damage and quantified crypsis, activity levels and flight speed. We then tested for correlations between damage parameters and species traits using comparative methods that account for measurement error. We detected considerable differences in the extent, location and symmetry of wing surface loss among species, with smaller differences between sexes. We found that males (but not females) of species that flew faster had substantially less wing surface loss. However, we found no correlation between cryptic coloration and symmetrical wing surface loss across species. In species in which males appeared to be more active than females, males had a lower proportion of symmetrical wing surface loss than females. Our results provide evidence that activity greatly influences the probability of attacks and that flying rapidly is effective for escaping pursuing predators in the wild, but we did not find evidence that cryptic species are less likely to be attacked while at rest.

No Indication of High Host-Plant Specificity in Afrotropical Geometrid Moths.

Specificity is one of the fundamental concepts in ecology. Host specificity of phytophagous insects has been of particular interest because of its crucial role in diversification and life-history evolution. However, the majority of tropical insects remain insufficiently explored with respect to their host-plant relations. A lack of respective data is also hindering the debate over whether higher levels of host-plant specificity prevail in tropical insects compared to temperate ones. We investigated host-plant specificity of forest geometrid moths (Lepidoptera: Geometridae) in equatorial Africa using host-plant acceptability trials with neonate larvae, with the addition of field observations. We compare our experimental data to the (well-known) host-specificity patterns of closely related temperate (hemiboreal) species. Similarly to the temperate region, there were broadly polyphagous tropical species in several clades of Geometridae utilizing hosts belonging to different plant families. Phylogenetic comparative analysis returned no significant differences in host specificity between the two regions. Our study contributes to the evidence that host-plant specificity of herbivores is not necessarily substantially higher in tropical than temperate regions.

Correlations between social context and fecal glucocorticoid metabolite concentrations in free-ranging female gray-cheeked mangabeys (Lophocebus albigena) in Kibale National Park, Uganda.

An elevated concentration of glucocorticoids is an indicator of stress, and chronically high glucocorticoid levels are often associated with poor health and reduced fertility. We explored conditions that might be stressors in the lives of adult female gray-cheeked mangabeys (Lophocebus albigena) by measuring fecal glucocorticoid metabolites (fGCM) concentrations. During a six-month study we collected 109 fecal samples from 28 adult females from five groups in Kibale National Park, Uganda. We examined fecal fGCM levels of individual females relative to their own reproductive status (cycling or not cycling) and that of other females and to the presence of newcomer (immigrant) males. We found elevated fGCM concentrations in females when other females in their groups were at the peak of sexual swelling, and when immigrant males joined the group.

What Drives Caterpillar Guilds on a Tree: Enemy Pressure, Leaf or Tree Growth, Genetic Traits, or Phylogenetic Neighbourhood?

Communities of herbivorous insects on individual host trees may be driven by processes ranging from ongoing development via recent microevolution to ancient phylogeny, but the relative importance of these processes and whether they operate via trophic interactions or herbivore movement remains unknown. We determined the leaf phenology, trunk diameter, genotype, and neighbourhood of sessile oak trees (Quercus petraea), and sampled their caterpillar communities. We found that leaf development across a time period of days related to free-living caterpillars, which disappeared with leaf age. Tree growth across decades is related to increased parasitism rate and diversity of herbivores. The microevolution of oak trees across millennia is related to the abundance of leaf-mining casebearers, which is higher on more homozygous oaks. However, oak genome size was not important for any guild. In contrast to most previous studies, the phylogenetic distance of oaks from their neighbours measured in millions of years was associated with higher abundances of entire caterpillar guilds. Furthermore, on trees surrounded by only distantly related tree species, parasitism tended to be lower. Lower parasitism, in turn, was associated with higher abundances of codominant caterpillar species. Neighbourhoods and traits of trees were also related to community composition and diversity, but not to the average wingspans or specialization of species, consistent with the assembly of herbivore communities being driven by leaf traits and parasitism pressure on trees rather than by insect movement among trees. However, movement in rarer species may be responsible for concentration effects in more phylogenetically distant neighbourhoods. Overall, we suggest that the assembly of insects on a tree is mostly driven by trophic interactions controlled by a mosaic of processes playing out over very different time scales. Comparisons with the literature further suggest that, for oak trees, the consequences of growing amongst distantly related tree species may depend on factors such as geographic region and tree age.

Social factors increase fecal testosterone levels in wild male gray-cheeked mangabeys (Lophocebus albigena).

Testosterone can be expected to play a significant role in mediating behavior and life history in social animals, but the number of species with data from the wild is still too small to make generalizations. We investigated the influence of social factors (social status, aggression, and reproductive females) and environmental variation (rainfall and temperature) on fecal testosterone concentrations in wild male gray-cheeked mangabeys (Lophocebus albigena) living in five groups in Kibale National Park, Uganda. This species is phylogenetically closely related to baboons, but is arboreal, with multi-male, multi-female groups rarely exceeding 20 individuals. We analyzed 358 fecal samples from 21 adult males. We found that the highest-ranking males had the highest testosterone concentrations while immigrant males had the lowest testosterone concentrations. Aggression was not correlated with testosterone levels. The presence of females with sexual swellings at their most tumescent stage increased testosterone concentrations in all males. Finally, individuals tended to have lower testosterone when the temperature was higher.

Seasonal trends in Ceratitis capitata reproductive potential derived from live-caught females in Greece.

Reproductive data of individual insects are extremely hard to collect under natural conditions, thus the study of research questions related to oviposition has not advanced. Patterns of oviposition are often inferred only indirectly, through monitoring of host infestation, whereas the influence of age structure and several other factors on oviposition remains unknown. Using a new approach, in this article, we live-trapped wild Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) females on the Greek island of Chios during two field seasons. For their remaining lifetime, these females were placed individually in small cages and their daily oviposition was monitored. Reproduction rates between cohorts from different collection dates were then compared. The results showed that in the different captive cohorts the average remaining lifetime and reproduction were highly variable within and between seasons. Multivariate regression analysis showed that the month of capture had a significant effect on captive life span, average daily reproduction, and patterns of egg laying. The effect of year was significant on reproduction, but not on captive life span. These differences between sampling periods probably reflect differences in the availability of hosts and other factors that vary during the season and affect age structure and reproduction. Using a non-parametric generalized additive model, we found a statistically significant correlation between the captive life span and the average daily reproduction. These findings and the experimental approach have several important implications.

Reproductive tactics influence cortisol levels in individual male gray-cheeked mangabeys (Lophocebus albigena).

Concentration of the hormone cortisol is often used as an indicator of stress, and chronically high cortisol levels are often associated with poor health. Among group living animals that compete for resources, agonistic social interactions can be expected to contribute to variation in cortisol levels within and among individuals over time. Reproductive tactics of males can change with individual quality, relatedness, and social structure, and affect cortisol levels. In gray-cheeked mangabey (Lophocebus albigena) groups, male rank is an important factor in social interactions, and males also move between groups while actively competing for females or sneaking copulations. During a 20-month study we observed the social behavior and collected 461 fecal samples from 24 adult male gray-cheeked mangabeys from five groups in Kibale National Park, Uganda. Aggressive interactions and the presence of females at the peak of sexual swelling were associated with elevated cortisol concentrations in all males. Independently, dominant (i.e., highest-ranking) males within groups had higher cortisol concentrations than subordinate males, and immigrant males had higher cortisol concentrations than dominant males.

Species, age and sex differences in type and frequencies of injuries and impairments among four arboreal primate species in Kibale National Park, Uganda.

Animals in the wild often have physical impairments that can affect their fitness. The aim of this study was to compare injuries and impairments of four different primate species (black-and-white colobus, red colobus, red-tailed monkeys, and grey-cheeked mangabeys) living in Kibale National Park (Uganda), and estimate the proportion of injured and impaired individuals among the sexes and age classes. The species differed in the proportion of individuals with injuries and impairments, with 16.7% in black-and-white colobus, 23.1% in red colobus, 16.2% in red-tailed monkey and 30.2% in grey-cheeked mangabeys. Species also differed in the types and location on the body of injuries. Adult animals had more injuries than immatures. Males had more injuries than females, in all but red-tailed monkeys. The results are discussed in relation to the literature on aggressive behavior, locomotion, and predation in these species.

Amino acid sources in the adult diet do not affect life span and fecundity in the fruit-feeding butterfly Bicyclus anynana.

1. In tropical forests, the adults of many butterfly species feed on fruits rather than nectar from flowers and have long life spans. Rotting fruit and nectar differ from each other in many respects, including sources of amino acids and microbial life. If amino acids in the adult diet can be used for reproduction, this may have facilitated the evolution of extended life spans in this guild.2. This issue was addressed by investigating effects of banana, yeast, and amino acids in the adult diet of the fruit-feeding butterfly Bicyclus anynana (Lepidoptera) on longevity and female reproductive output in two experiments.3. Results showed that in the fruit-feeding butterfly B. anynana: (i) banana juice, but not sliced banana or added amino acids extend life span compared with a sugar solution of similar composition; (ii) compared with this sugar solution, other cohorts (banana juice-amino acid enriched) did not have significantly higher reproductive outputs; (iii) yeast does not represent a valuable source of nutrients; (iv) caloric restriction may cause decreased life span and rate of reproduction; and (v) increased rates of reproduction have a life span cost.

Adult diet affects lifespan and reproduction of the fruit-feeding butterfly Charaxes fulvescens.

Fruit-feeding butterflies are among the longest lived Lepidoptera. While the use of pollen-derived amino acids by Heliconius butterflies has been interpreted as important for the evolution of extended lifespans, very little is known about the life-history consequences of frugivory. This issue is addressed by investigating effects of four adult diets (sugar, sugar with amino acids, banana, and moistened banana) on lifespan and reproduction in the fruit-feeding butterfly Charaxes fulvescens Aurivillius (Lepidoptera: Nymphalidae). Female butterflies were collected from Kibale National Park, Uganda, and kept individually in cages near their natural habitat and data were collected on lifespan, oviposition, and hatching of eggs. Lifespan in captivity was longer for the sugar and the amino acid cohort, than for the banana cohorts. The longitudinal pattern of oviposition was erratic, with many days without oviposition and few periods with high numbers of eggs laid. Butterflies typically did not lay eggs during their 1st week in captivity and the length of the period between capture and first reproduction was significantly shorter for butterflies fed moistened banana. The length of the reproduction period (first reproduction-last reproduction in captivity) and the reproduction rate (total number of eggs/length of the reproduction period) did not differ significantly between the diet treatments. Those fed with amino acid and moistened banana had significantly higher egg hatchability than those fed with sugar and banana. We found no evidence for a lifespan cost of reproduction. Our results show that (1) female C. fulvescens can use amino acids in their diet for laying fertile eggs, (2) more wing-wear does correlate with lower survival in captivity (indicating aging in the wild), but not with intensity of reproduction (providing no evidence for reproductive aging), and (3) fruit-feeding butterflies may be dietary restricted in the field.

Large body size constrains dispersal assembly of communities even across short distances.

Dispersal limitation has been considered to decrease with body size in animals and to be an important factor limiting community assembly on spatially isolated patches. Here we hypothesize that for flightless bark-dwelling oribatid mites dispersal limitation onto young trees might increase with body size (due to a decrease in aerial dispersal capacities), and it might occur even within a spatially contiguous forest canopy. We suppressed dispersal limitation towards branches from young trees by physically connecting them to branches from old trees and analyzed the impacts on community composition, accounting for branch microhabitat variables. Suppression of dispersal limitation increased community evenness and mean body size of mites on branches from young trees. Across all species, large species body-size corresponds to an abundance increase after suppression of dispersal limitation. Consistently, on no-contact control branches, mite body-sizes were larger on branches from old compared to young trees. Our study suggests that colonization/performance trade-offs might affect community assembly even across seemingly contiguous habitats. Overall, a previously underappreciated factor selecting against large body size in flightless canopy-dwelling invertebrates might be that large bodies makes these invertebrates fall faster and disperse less, not more.

Relative contribution of neutral and deterministic processes in shaping fruit-feeding butterfly assemblages in Afrotropical forests.

The unified neutral theory of biodiversity and biogeography has gained the status of a quantitative null model for explaining patterns in ecological (meta)communities. The theory assumes that individuals of trophically similar species are functionally equivalent. We empirically evaluate the relative contribution of neutral and deterministic processes in shaping fruit-feeding butterfly assemblages in three tropical forests in Africa, using both direct (confronting the neutral model with species abundance data) and indirect approaches (testing the predictions of neutral theory using data other than species abundance distributions). Abundance data were obtained by sampling butterflies using banana baited traps set at the forest canopy and understorey strata. Our results indicate a clear consistency in the kind of species or species groups observed at either the canopy or understorey in the three studied communities. Furthermore, we found significant correlation between some flight-related morphological traits and species abundance at the forest canopy, but not at the understorey. Neutral theory's contribution to explaining our data lies largely in identifying dispersal limitation as a key process regulating fruit-feeding butterfly community structure. Our study illustrates that using species abundance data alone in evaluating neutral theory can be informative, but is insufficient. Species-level information such as habitat preference, host plants, geographical distribution, and phylogeny is essential in elucidating the processes that regulate biodiversity community structures and patterns.

A search for principles of disability using experimental impairment of Drosophila melanogaster.

The results of life table experiments to determine the effects of artificial impairment (leg amputation) in 7500 Drosophila melanogaster adults revealed that the extent to which life expectancy was reduced in impaired individuals was conditional on: (1) leg location and number amputated--front leg had greatest impact and the number of legs amputated directly correlated with mortality impact; (2) age of amputation--the greatest relative reduction in remaining life expectancy occurred when young flies were impaired; (3) vial orientation--mortality in impaired flies was the least when vials held upside-down (most friendly environment) and the greatest when they were right-side up (least friendly environment); and (4) sex--male mortality was increased more than female mortality in nearly all impairment treatments. These results were used to formulate a set of general principles of disability that would apply not only to humans but to all organisms.

Differentiation in putative male sex pheromone components across and within populations of the African butterfly Bicyclus anynana as a potential driver of reproductive isolation.

Sexual traits are often the most divergent characters among closely related species, suggesting an important role of sexual traits in speciation. However, to prove this, we need to show that sexual trait differences accumulate before or during the speciation process, rather than being a consequence of it. Here, we contrast patterns of divergence among putative male sex pheromone (pMSP) composition and the genetic structure inferred from variation in the mitochondrial cytochrome oxidase 1 and nuclear CAD loci in the African butterfly Bicyclus anynana (Butler, 1879) to determine whether the evolution of "pheromonal dialects" occurs before or after the differentiation process. We observed differences in abundance of some shared pMSP components as well as differences in the composition of the pMSP among B. anynana populations. In addition, B. anynana individuals from Kenya displayed differences in the pMSP composition within a single population that appeared not associated with genetic differences. These differences in pMSP composition both between and within B. anynana populations were as large as those found between different Bicyclus species. Our results suggest that "pheromonal dialects" evolved within and among populations of B. anynana and may therefore act as precursors of an ongoing speciation process.

Sexual differences in weight loss upon eclosion are related to life history strategy in Lepidoptera.

Given that immature and adult insects have different life styles, different target body compositions can be expected. For adults, such targets will also differ depending on life history strategy, and thus vary among the sexes, and in females depend on the degree of capital versus income breeding and ovigeny. Since these targets may in part be approximated by loss of substances upon eclosion, comparing sexual differences in such losses upon eclosion among species that differ in life history would provide insights into insect functional ecology. We studied weight loss in eclosing insects using original data on pupal and adult live weights of 38 species of Lepidoptera (mainly Geometridae) and further literature data on 15 species of Lepidoptera and six representatives of other insect orders, and applied the phylogenetic independent contrasts approach. In addition, data on live and dry weights of pupae of four species of Lepidoptera are presented. We documented that Lepidoptera typically lose a large proportion (20-80%) of their pupal weight upon adult eclosion. Sexual differences in weight loss varied between absent and strongly male biased. Most of the weight loss was water loss, and sexual differences in adult water content correlate strongly with differences in weight loss. Using feeding habits (feeds or does not feed as an adult) and female biased sexual size dimorphism as measures of degree of capital breeding, we found that the difference among the sexes in weight loss tends to be more pronounced in capital breeding species. Additionally, females of more pro-ovigenic species (large proportion of eggs mature upon emergence) tend to have higher water contents. Our results suggests that metamorphosis is generally facilitated by a high water content, while adults excrete water upon eclosion to benefit flight unless water has been allocated to eggs, or is treated as a capital resource for adult survival or future allocation to eggs.

Reproductive aging in tephritid fruit flies.

The broad objective of this paper is to present an overview and synthesis of selected studies on reproduction and aging in two model tephritid fruit fly species including the Mediterranean fruit fly, Ceratitis capitata, and the Mexican fruit fly, Anastrepha ludens. We summarize the research findings from empirical studies and modeling investigations involving reproduction in the two tephritid species. At the end we identify and discuss four general principles regarding reproductive aging in tephritids including reciprocity of reproductive and aging costs, qualitative tradeoffs, plasticity of lifespan and reproduction, and life history constraints and determinacy.

Cost of reproduction in male medflies: the primacy of sexual courting in extreme longevity reduction.

In polygynous insect species, male reproductive success is directly related to lifetime mating success. However, the costs for males of sexual activities such as courting, signaling, and mating are largely unknown. We studied the cost of sexual activities in male Mediterranean fruit flies, Ceratitis capitata (Tephritidae), a polygynous lekking species, by keeping cohorts of individual male flies under relaxed crowding conditions in the laboratory. We used 5 cohorts among which individuals differed in their opportunities to interact with con-specifics and recorded life span, and in one treatment, mating rate. We found that males kept singly lived more than twice as long as males that interacted intensively with mature virgin females, while male-male interactions caused a smaller reduction in longevity. Because longevity of males that could court but not mate was not significantly different from those that could court and mate, we conclude that courting (not mating) was responsible for the observed longevity reduction. Moreover, we detected high variability in male mating success, when 5 virgin females were offered daily. In contrast to the cohort level, individual males that mated at a high rate lived relatively long, thus indicating heterogeneity in quality or sexual strategy among males.