Tiit Teder

University of Tartu · Department of Zoology

Where predation is seasonally variable, the potential impact of a predator on individual prey species will critically depend on phenological synchrony of the predator with the prey. Here we explored the effects of seasonally variable predation in multispecies assemblages of short-lived prey. The study was conducted in a landscape in which we had pr...

The degree and direction of sexual size dimorphism (SSD) vary greatly between animal species. At the ontogenetic level, SSD may result from sex differences in birth size, growth rate and/or development time. Nevertheless, evidence concerning proximate causation of SSD is scattered, and the data used to infer ontogenetic determinants of SSD have not...

Risky in the tropics It is well known that diversity increases toward the tropics. Whether this increase translates into differences in interaction rates among species, however, remains unclear. To simplify the problem, Roslin et al. tested for predation rates by using a single approach involving model caterpillars across six continents. Predator a...

Changes in the number of generations per year (voltinism) have been among the most common phenological responses to climate warming in insects inhabiting seasonal environments. Nevertheless, numerous species have maintained univoltine (one generation per year) phenology with increasing temperatures, indicating the involvement of phylogenetic, ecolo...

Conspecific females and males often follow different development trajectories which leads to sex differences in age at maturity (sexual bimaturism, SBM). Whether SBM is typically selected for per se (direct selection hypothesis) or merely represents a side-effect of other sex-related adaptations (indirect selection hypothesis) is, however, still an...

Temperature has a profound effect on the growth and development of ectothermic animals. However, the extent to which ecologically driven selection pressures can adjust thermal plastic responses in growth schedules is not well understood. Comparing temperature‐induced plastic responses between sexes provides a promising but underexploited approach t...

Current climate change is disrupting biotic interactions and eroding biodiversity worldwide. However, species sensitive to aridity, high temperatures and climate variability might find shelter in microclimatic refuges, such as leaf rolls built by arthropods. To explore how the importance of leaf shelters for terrestrial arthropods changes with lati...

Biodiversity is rapidly declining worldwide, with agricultural intensification being among the main drivers of this process. Effective conservation measures in agricultural landscapes are therefore urgently needed. Here we introduce a novel low-cost conservation measure called artificial field defects, i.e., areas where crop is not sown and spontan...

The construction of shelters on plants by arthropods might influence other organisms via changes in colonization, community richness, species composition and functionality. Arthropods, including beetles, caterpillars, sawflies, spiders, and wasps often interact with host plants via the construction of shelters, building a variety of structures such...

Background and aims – Agricultural intensification and loss of farmland heterogeneity have contributed to population declines of wild bees and other pollinators, which may have caused subsequent declines in insect-pollinated wild plants. Material and methods – Using data from 37 studies on 22 pollinator-dependent wild plant species across Europe, w...

Current climate change is disrupting biotic interactions and eroding biodiversity worldwide. However, species sensitive to drought, high temperatures and climate variability might persist in microclimatic refuges, such as leaf shelters built by arthropods. We conducted a distributed experiment across an 11,790 km latitudinal gradient to explore how...

To create effective conservation measures for pollinators, we need to understand how landscape structure affects their distribution. We examined the effects of forest proximity on bumblebee communities in a modern agricultural landscape in the forest-rich hemi-boreal region. We contrasted bumblebee communities in field margins located next to fores...

The distribution of butterflies was mapped throughout entire Estonia in 2016 and 2017. Butterflies were surveyed during three phenologically targeted visits at more than 1200 pre-selected sites. In total, over 180 000 individuals belonging to 97 species were recorded. We compare the resulting distribution maps with historical records, and discuss c...

The harlequin ladybird, Harmonia axyridis, is considered to be one of the most invasive insect species worldwide. Its invasion success and extreme speed of range expansion has been partially attributed to weak control of its populations by natural enemies. Previously published data on emergence rates of the hymenopteran parasitoid Dinocampus coccin...

Sex-specific mechanisms of the determination of insect body sizes are insufficiently understood. Here we use the common heath moth, Ematurga atomaria (Lepidoptera: Geometridae) to examine how larval growth trajectories differ between males and females. We monitored the development of 1379 larvae in controlled laboratory conditions. Sexually dimorph...

The absolute, relative and allometric growth rates, and the rationale behind them. (DOCX)

The recordings of development time (days) and body mass (mg) of the Ematurga atomaria larvae (N = 1379) during their last, 5th instar. (TXT)

Comparing the contributions of 1) sexually dimorphic instantaneous growth rate, and 2) longer development periods of females to the formation of SSD. (DOCX)

Three different integral measures of growth rates of the last (5th) larval instar (mean values±SE) of Ematurga atomaria, a lepidopteran with sexual dimorphism in pupal masses. (DOCX)

Reanalysis of the data of the present article using integral measures of growth rate. (DOCX)

Forests managed by clear-cutting, rich in open spaces, provide alternative habitat for many grassland butterfly species in boreal and temperate environments. We have recently shown that local butterfly assemblages in forest openings are shaped by environmental filtering rather than dispersal limitation. However, at the level of individual movements...

Parasitoids acting as biocontrol agents provide farmers with valuable ecosystem services, but are sensitive to insecticides applied against pests. Besides lethal effects of insecticides, sublethal effects observed among survivors may further influence parasitoids’ performance. However, information on sublethal effects is scattered across case studi...

Evaluating ecological processes that assemble local animal communities from available species pools has remained a challenging task. At a time of drastic decline of natural and seminatural grasslands, contemporary production forests provide various novel types of open spaces (clear-cuts, power line corridors, etc.) that are potentially suitable hab...

Sexual size dimorphism (SSD) can vary drastically across environments, demonstrating pronounced sex-specific plasticity. In insects, females are usually the larger and more plastic sex. However, the shortage of taxa with male-biased SSD hampers the assessment of whether the greater plasticity in females is driven by selection on size or represents...

The PREDICTS project—Projecting Responses of Ecological Diversity In Changing Terrestrial Systems (www.predicts.org.uk)—has collated from published studies a large, reasonably representative database of comparable samples of biodiversity from multiple sites that differ in the nature or intensity of human impacts relating to land use. We have used t...

Female oviposition decisions in insects may strongly affect offspring growth and survival, and thus determine population performance. In this study, we examined oviposition site selection in the xerophilous ecotype of the endangered myrmecophilous butterfly Phengaris (=Maculinea) alcon (Lepidoptera, Lycaenidae) in Estonia, at the northern distribut...

In myrmecophilous insects, interactions with ants are often a key factor determining persistence of their populations. Regional variation in host ant use is therefore an essential aspect to consider to provide adequate conservation practices for such species. In this study, we examined this important facet of species’ ecology in an endangered myrme...

Contemporary forest landscapes in boreal and temperate environments, harvested by clear-cutting, contain various novel types of open spaces which are potentially suitable for species inhabiting natural or semi-natural open habitats. However, systematic analyses identifying the share of the regional species pool that can take advantage of this oppor...

The degree of ecological specialization plays a crucial role in shaping the structure and functioning of communities. However, comparing specialization within and among groups of organisms is complicated due to methodological issues but also by conceptual and terminological inconsistencies. Environmental predictability has been considered a key det...

Populations close to species distribution limits often differ in their habitat use from more central populations of the species distribution. Knowledge of species ecology derived from the latter may therefore not be sufficient to ensure successful conservation of peripheral populations.In this study, we examine habitat use of Phengaris (=Maculinea)...

Making generalisations on trophic interactions is often limited because studies mostly focus on only a few target systems. Despite the important role of fungivores in forest ecosystems, the determinants of their communities are poorly known. This study examined, for the first time on the basis of quantitative data, the diversity of fungivorous inse...

An evolutionary explanation should consider the balance between environmentally-based selective pressures, and the resistance of the organism's phenotype to adaptive evolution, with the latter being captured by the concept of constraint. The limited attention to non-adaptive explanations in evolutionary ecology is at least partly caused by methodol...

Optimality models predict that diet-induced bivariate reaction norms for age and size at maturity can have diverse shapes, with the slope varying from negative to positive. To evaluate these predictions, we perform a quantitative review of relevant data, using a literature-derived data base of body sizes and development times for over 200 insect sp...

Most insect populations are exploited by a complex of different parasitoid species, providing ample opportunities for competitive interactions among the latter. Despite this, resource-mediated competition (i.e., exploitative competition) among insect parasitoids remains poorly documented in natural systems. Here we propose a novel way to infer the...

Seasonal generations of short-lived organisms often differ in their morphological, behavioural and life history traits, including body size. These differences may be either due to immediate effects of seasonally variable environment on organisms (responsive plasticity) or rely on presumably adaptive responses of organisms to cues signalizing forthc...

Patterns of variability in quantitative traits across environmental gradients have received relatively little attention in evolutionary ecology. A recent meta-analysis showed that relative phenotypic variability in body size tends to decrease with improving environmental conditions. This pattern was explained by introducing the concept of upper thr...

1. Mortality caused by natural enemies is an essential but largely overlooked aspect of habitat quality for herbivorous insects. Quantitative data on mortality sources and their spatiotemporal variation are especially scarce for adult insects. 2. Here we report the results of an extensive field study aimed to quantify spatial and seasonal variatio...

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 appro...

Different biotic interactions may influence one another to produce complex patterns of direct and indirect effects, which together influence plant reproductive success. However, so far most studies on plant-animal interactions have focused on single interactions in isolation. In this study, we studied the effect of florivory by the weevil Cionus ni...

Habitat loss often leads to a substantial decline in species richness. However, the extinction of species is typically not instant, but rather involves a time lag. Species richness in recently disturbed habitats is therefore expected to reflect past rather than current habitat availability, with the set of species eventually going extinct represent...

Different levels of sexual size dimorphism (SSD) have usually been explained by selective forces operating in the adult stage. Developmental mechanisms leading to SSD during the juvenile development have received less attention. In particular, it is often not clear if the individuals of the ultimately larger sex are larger already at hatching/birth...

Intensification or abandonment of agricultural land use has led to a severe decline of semi-natural habitats across Europe. This can cause immediate loss of species but also time-delayed extinctions, known as the extinction debt. In a pan-European study of 147 fragmented grassland remnants, we found differences in the extinction debt of species fro...

Males and females of nearly all animals differ in their body size, a phenomenon called sexual size dimorphism (SSD). The degree and direction of SSD vary considerably among taxa, including among populations within species. A considerable amount of this variation is due to sex differences in body size plasticity. We examine how variation in these se...

1. Habitat fragmentation can affect pollinator and plant population structure in terms of species composition, abundance, area covered and density of flowering plants. This, in turn, may affect pollinator visitation frequency, pollen deposition, seed set and plant fitness. 2. A reduction in the quantity of flower visits can be coupled with a reduct...

Changes in plant population size, induced by various forms of habitat degradation, can affect the performance of plants by altering their interactions with other organisms such as pollinators and herbivores. However, studies on plant reproductive response to variation in population size that simultaneously consider different interactions are rare....

Local extinction of species can occur with a substantial delay following habitat loss or degradation. Accumulating evidence suggests that such extinction debts pose a significant but often unrecognized challenge for biodiversityconservation across a wide range of taxa and ecosystems. Species with long generation times and populations near their ext...

Within a season, successive generations of short-lived organisms experience different combinations of environmental parameters, such as temperature, food quality and mortality risk. Adult body size of e.g. insects is therefore expected to vary both as a consequence of proximate environmental effects as well as adaptive responses to seasonal cues. I...

The recent "overhead threshold" model for optimal age and body size at maturity (Day and Rowe 2002 ) predicts that phenotypic variability in adult body size will be low under inferior environmental quality and will increase with improving conditions. The model is, however, based on a potentially restrictive assumption of a monotone increase of fecu...

Rensch's rule (so termed by Abouheif and Fairbairn 1997; Fairbairn 1997) describes a wide- spread pattern in the animal kingdom that male body size diverges faster than female body size over evolutionarily time among related species, such that male-biased sexual size dimorphism (henceforth dimorphism) increases and female- biased dimorphism decreas...

1. In arthropods, the evolution of sexual size dimorphism (SSD) may be constrained by a physiological limit on growth within each particular larval instar. A high SSD could, however, be attained if the larvae of the larger sex pass through a higher number of larval instars. 2. Based on a survey of published case studies, the present review shows t...

Practical approaches to monitoring biological diversity vary widely among countries, and the accumulating data are frequently not generalizable at the international scale. Although many present monitoring schemes, especially in developed countries, produce highly complex data, there is often a lack of basic data about the level and spatial distribu...

A prominent interspecific pattern of sexual size dimorphism (SSD) is Rensch's rule, according to which male body size is more variable or evolutionarily divergent than female body size. Assuming equal growth rates of males and females, SSD would be entirely mediated, and Rensch's rule proximately caused, by sexual differences in development times,...

1. Sexual differences in body size are expected to evolve when selection on female and male sizes favours different optima.2. Insects have typically female-biased size dimorphism that is usually explained by the strong fecundity advantage of larger size in females. However, numerous exceptions to this general pattern have led to the search for sele...

Studies examining interspecific differences in sexual size dimorphism (SSD) typically assume that the degree of sexual differences in body size is invariable within species. This work was conducted to assess validity of this assumption. As a result of a systematic literature survey, datasets for 158 insect species were retrieved. Each dataset conta...

Despite the impact of parasitoids on insect populations being extensively studied, indirect parasitoid-mediated effects remain rarely documented in natural communities. We examined the influence of shared parasitoids on the interactions between two functionally monophagous moths, Nonagria typhae and Archanara sparganii. The moths showed a considera...

1. Consequences of variation in food plant quality were estimated for a system consisting of two monophagous noctuid herbivores and three ichneumonid parasitoids. 2. In a natural population, pupal weights of the herbivores in this system, Nonagria typhae and Archanara sparganii, were found to be highly variable. Pupal weights increased strongly an...

The effect of larval body size of Epirrita autumnata (Lepidoptera, Geometridae) on the risk of parasitism was studied in a field experiment. The experiment involved three pairwise exposures of different larval instars to parasitoids. Three hymenopteran species were responsible for most of the parasitism. Parasitism risk was found to be host-instar...

In order to assess the role of parasitoids in the regulation of non-outbreaking populations of Epirrita autumnata, a geometrid lepidopteran with outbreaking populations in northern Europe, we examined the temporal and spatial variation of larval parasitism in southwestern Finland during 6 successive years. The study was carried out on two spatial s...

We detected a significant inter- and intraspecific host preference on the level of individual host use in a system, in which three moth species (Lepidoptera: Noctuidae), feeding on a cattail Typha latifolia, are parasitized by three solitary parasitoid species (Hymenoptera: Ichneumonidae). The biology of the host species is similar but they exhibit...

We studied the morphometric variability of genitalia in five species of the genus Pimpla (Hymenoptera, Ichneumonidae). This genus is characterized by a high intraspecific variation in body size, a simple structure of the genitalia and many closely related species. We found that genitalic characters of all studied species vary less than characters r...