Biology subjects

Klecka, J.

Publications and source records attributed to Klecka, J..

13 recordsLinked to original sources

bioRxiv2024

The evolution of wasp mimicry and biogeography in the genus Temnostoma (Diptera: Syrphidae)

One of the most remarkable examples of Batesian mimicry occurs in the genus Temnostoma Le Peletier & Audinet-Serville, 1828 (Diptera: Syrphidae). Adults of this genus have an overall resemblance to hymenopterans combined with behavioural mimicry (they move the fore legs in front of the head mimicking hymenopteran antennae). While some species of Temnostoma are considered perfect mimics of social wasps, other species have a darker colour pattern and are rather imperfect mimics. Both colour morphs are widespread through the Holarctic. Here, we infer for the first time the evolutionary history of the genus with special focus on the evolution of mimicry and biogeography. With material covering 75 % of known species of Temnostoma and both colour morphs from each biogeographical region, we inferred a molecular phylogeny based on six molecular markers (mitochondrial protein-coding COI gene, nuclear 28s rRNA gene, and four nuclear protein-coding genes: AATS, CK1, TULP, and RBP-15). Using Bayesian inference, we obtained a highly resolved phylogenetic tree supporting the monophyly of the genus Temnostoma as a sister group of genus Takaomyia Herve-Bazin, 1914. Within Temnostoma, Te. daochus and Te. barberi (two Nearctic species with strikingly different mimicry patterns) were found to be closely related to each other and together form a lineage sister to the rest of the genus. Our results suggest that the behavioural mimicry of wasp antennae is a plesiomorphic state inherited from a common ancestor that includes the genera Temnostoma and Takaomyia. Within Temnostoma, the dark colour pattern (imperfect mimicry) appeared to be an ancestral state and perfect wasp mimicry evolved two times independently within the genus. In some species inhabiting northern parts of the Holarctic, secondary darkening and consequent degradation of the wasp mimicry appeared. This indicates high evolutionary plasticity and ongoing selection pressure on morphological characters related to mimicry in hover flies.

zoology↗

bioRxiv2023

Pollen viability of a widespread plant in response to climate warming: possible local adaptation of populations from different elevations

One of the most vulnerable phases in the plant life cycle is sexual reproduction, which depends on effective pollen transfer, but also on the thermotolerance of pollen grains. Pollen thermotolerance is temperature-dependent and may be reduced by increasing temperature associated with global warming. A growing body of research has focused on the effect of increased temperature on pollen thermotolerance in crops to understand the possible impact of temperature extremes on yield. Yet, little is known about the effects of temperature on pollen thermotolerance of wild plant species. To fill this gap, we selected Lotus corniculatus s.l. (Fabaceae), a species common to many European habitats and conducted laboratory experiments to test its pollen thermotolerance in response to artificial increase in temperature. To test for possible local adaptation of pollen thermal tolerance, we compared data from six lowland (389 - 451 m a.s.l.) and six highland (841 - 1030 m a.s.l.) populations. We observed pollen germination in vitro at 15, 25, 30, and 40{degrees}C. While lowland plants had stable germination rate at a wide range of temperatures between 15 and 30{degrees}C, with reduced germination rate observed only at extremely high temperatures (i.e., 40{degrees}C), the germination rate of highland plants was reduced already when the temperature reached 30{degrees}C, temperature commonly exceeded in the lowland during warm summers. This suggests that lowland populations of L. corniculatus may be locally adapted to higher temperature for pollen germination. On the other hand, pollen tube length decreased with increasing temperature in a similar way in lowland and highland plants. The overall average pollen germination rate significantly differed between lowland and highland populations, with highland populations displaying higher germination rate. On the other hand, the average pollen tube length was slightly smaller in highland populations. In conclusion, we found that pollen thermotolerance of L. corniculatus is reduced at high temperature and that the germination of pollen from plant populations growing at higher elevations is more sensitive to increased temperature, which suggests possible local adaptation of pollen thermotolerance.

ecology↗

bioRxiv2023

Invertebrate herbivory damage of lowland plant species decreases after an experimental shift to higher altitudes

Many species of plants and animals shift to higher altitudes in response to the ongoing climate warming. Such shifts of species distributions lead to the co-occurrence of species that have not previously lived in the same environment and allow the emergence of novel plant-animal interactions with potential implications for species diversity and community composition in mountain habitats. According to the enemy release hypothesis, the spread of plants in new geographic regions may be facilitated by the reduction of damage caused by natural enemies, such as herbivores. While the importance of this mechanism for the spread of invasive exotic species has been established, it is unclear whether the movement of plants uphill within their native region in response to increasing temperatures may be also facilitated by the reduction of herbivory at sites above their current upper altitudinal limit. In our study, we experimentally tested this hypothesis. We compared herbivory damage of six species of lowland plants grown in pots exposed to herbivores at their native sites in the lowland and at sites above their current upper altitudinal limit. As a control, we also measured herbivory damage of six plants growing naturally across the entire range of altitude. We found that lowland plants had reduced herbivory damage when they were moved to highland sites, while herbivory damage of species naturally growing at both altitudes did not differ. Changes of herbivory damage were modulated by leaf dry matter content and to a lesser degree also by specific leaf area and plant height. Our results provide support for the enemy release hypothesis in the novel context of altitudinal range shifts. We conclude that the reduction of herbivory damage may facilitate the spread of plants above their current upper altitudinal limit in response to increasing temperature.

ecology↗

bioRxiv2022

Thermoregulation of adult alpine butterflies: microhabitat choice is more important than physical differences

Efficient thermoregulation is crucial for animals living under fluctuating climatic and weather conditions. We studied the body heating of six butterfly species of the genus Erebia (Lepidoptera: Nymphalidae) that co-occur in the European Alps. We tested whether butterfly physical characteristics (body size, wing loading) are responsible for the inter-specific differences in body temperatures recorded previously under natural conditions. We used a thermal camera to measure body heating of wild butterfly individuals in a laboratory experiment with artificial light and heating sources. We revealed that physical characteristics had a small effect on explaining inter-specific differences in mean body temperatures recorded in the field. Our results show that larger butterflies, with higher weight and wing loading, heated up more slowly but reached the same asymptotic body temperature as smaller butterflies. Altogether, our results suggest that differences in body temperatures among Erebia species observed in the field might be caused mainly by species-specific microhabitat use and point towards an important role of active behavioural thermoregulation in adult butterflies. We speculate that microclimate heterogeneity in mountain habitats facilitates behavioural thermoregulation of adults. Similarly, microclimate structuring might also increase survival of less mobile butterfly life stages, i.e., eggs, larvae and pupae. Thus, landscape heterogeneity in management practices may facilitate long term survival of montane invertebrates under increased anthropogenic pressures.

ecology↗

bioRxiv2022

Climatic niche conservatism and ecological diversification in the Holarctic cold-dwelling butterfly genus Erebia

The diversification of alpine species has been modulated by their climatic niches interacting with changing climatic conditions. The relative roles of climatic niche conservatism promoting geographical speciation and of climatic niche diversification are poorly understood in diverse temperate groups. Here, we investigate the climatic niche evolution in a species rich butterfly genus, Erebia. This Holarctic cold-dwelling genus reaches the highest diversity in European mountains. We generated a nearly complete molecular phylogeny and modelled the climatic niche evolution using geo-referenced occurrence records. We reconstructed the evolution of the climatic niche and tested how the species climatic niche width changes across the occupied climate gradient and compared two main Erebia clades, the European and the Asian clade. We further explored climatic niche overlaps among species. Our analyses revealed that the evolution of Erebia has been shaped by climatic niche conservatism, supported by a strong phylogenetic signal and niche overlap in sister species, likely promoting allopatric speciation. The European and the Asian clades evolved their climatic niches toward different local optima. In addition, species in the European clade have narrower niches compared to the Asian clade. Contrasts among the clades may be related to regional climate differences, with lower climate seasonality in Europe compared to Central Asia favouring the evolution of narrower niches. Further, adaptive divergence could appear in other traits, such as habitat use, which can be reflected by narrower climatic niches detected in the European clade. In conclusion, our study extends knowledge about the complexity of evolutionary drivers in temperate insects.

evolutionary biology↗

bioRxiv2021

Individual-level specialisation and interspecific resource partitioning in bees revealed by pollen DNA metabarcoding

It is increasingly recognised that intraspecific variation in traits, such as morphology, behaviour, or diet is both ubiquitous and ecologically important. While many species of predators and herbivores are known to display high levels of between-individual diet variation, there is a lack of studies on pollinators. It is important to fill in this gap because individual-level specialisation of flower-visiting insects is expected to affect their efficiency as pollinators with consequences for plant reproduction. Accordingly, the aim of our study was to quantify the level of individual-level specialisation and foraging preferences, as well as interspecific resource partitioning, across different temporal scales in three co-occurring species of bees of the genus Ceratina (Hymenoptera: Apidae: Xylocopinae), C. chalybea, C. nigrolabiata, and C. cucurbitina. We conducted a field experiment where we provided artificial nesting opportunities for the bees and combined a short-term mark-recapture study with the dissection of the bees nests to obtain repeated samples from individual foraging females and complete pollen provisions from their nests. Hence, we could study variation of the composition of pollen collected by the bees at different temporal scales. We used DNA metabarcoding based on the ITS2 locus to identify the composition of the pollen samples. We found that the composition of pollen carried on the bodies of female bees and stored in the brood provisions in their nests significantly differed among the three co-occurring species. At the intraspecific level, individual females consistently differed in their level of specialisation and in the composition of pollen carried on their bodies and stored in their nests. Our study thus provides evidence of consistent individual-level specialisation in pollinators across multiple temporal scales. We also demonstrate that higher generalisation at the species level stemmed from larger among-individual variation in diets as observed in other types of consumers, such as predators. Our study thus reveals how specialisation and foraging preferences of bees change from the scale of individual foraging bouts to complete pollen provisions accumulated in their nests over their lifetime. Such multi-scale view of foraging behaviour is necessary to improve our understanding of the functioning of plant-flower visitor communities.

ecology↗

bioRxiv2021

Are plants in sown flower strips suitable for communities of wild bees? Pollination network approach in conservation biology

O_LIDrastic reductions of insect diversity and abundance are observed in the highly fragmented agricultural landscapes of central Europe. Declines of pollinators may have detrimental effects on the reproduction of wild insect-pollinated plants as well as the yield of crops. In order to mitigate such impacts, sown flower strips on arable land within Agri-Environment Climate Schemes (AECS) are supported across EU countries. However, it is not clear whether sown flower strips provide equivalent benefits to wild flower-visiting insects as semi-natural habitats. C_LIO_LIHere, we apply plant-pollinator network approach to evaluate the function of sown flower strips for the communities of wild bees. We compared the structural characteristics and the robustness of plant-pollinator networks in sown flower strips and nearby semi-natural habitats. We also quantified the importance of individual plant species for bees based on simulations of plant-pollinator extinction cascades. C_LIO_LIWe found that assemblages of plants and pollinators were less diverse in sown flower strips than in semi-natural habitats, more generalized, and more nested. However, we did not find any significant differences in network robustness to plant-pollinator coextinctions. Further, simulations revealed a large variation in the functional importance among plant species from both habitats. C_LIO_LIWe conclude that although the analysis of network robustness suggested that plants in the sown flower strips and semi-natural habitats were functionally equivalent, this masked important differences among the two habitats. From the conservation point of view, semi-natural habitats were superior in supporting a more diverse community of solitary bees and bumblebees. C_LI

ecology↗

bioRxiv2020

Interactive effects of temperature, water, and nitrogen availability on the growth, floral traits, and pollination of white mustard,

Changes in environmental conditions are likely to have a complex effect on the growth of plants, their phenology, plant-pollinator interactions, and reproductive success. The current world is facing an ongoing climate change along with other human-induced environmental changes. Most research has focused on the impact of increasing temperature as a major driving force for climate change, but other factors may have important impacts on plant traits and pollination too and these effects may vary between different seasons. In addition, it is likely that the effects of multiple environmental factors, such as increasing temperature, water stress, and nitrogen enrichment are not independent. Therefore, we tested the impact of three key factors - season, water, and nitrogen supply - on plant traits, pollination, and seed production in Sinapis alba (Brassicaceae). Plants were grown in three seasons with two levels of water and nitrogen supply in a factorial design. We collected data on multiple vegetative and floral traits and assessed the response of pollinators in the field. Additionally, we evaluated the effect of growing conditions on seed set in plants exposed to pollinators and in hand-pollinated plants. Our results show that water stress impaired vegetative growth, decreased flower production, reduced visitation by pollinators and seed set, while nitrogen availability played an important role in nectar production. Seasonality modulated the effect of water and nitrogen availability on vegetative and floral traits and strongly affected flowering phenology and flower production. We demonstrated that changes in water and nitrogen availability alter plant vegetative and floral traits, which impacts flower visitation and consequently plant reproduction. We conclude that ongoing environmental changes such as altered precipitation regimes and nitrogen enrichment may thus affect plant-pollinator interactions with negative consequences for the reproduction of wild plants and insect-pollinated crops.

ecology↗

bioRxiv2020

Increasing habitat loss and human disturbances in the world's largest mangrove forest: the impact on plant-pollinator interactions

The Sundarbans, the largest mangrove forest in the world and a UNESCO world heritage site has been facing an increasing pressure of habitat destruction. Yet, no study has been conducted to test how human disturbances are affecting plant-pollinator interactions in this unique ecosystem. Hence, we aimed to provide the first insight of the impact of habitat loss and human disturbances on the pollinator communities in the Sundarbans. We selected 12 sites in the North-Western region of the Sundarbans, along a gradient of decreasing habitat loss and human activities from forest fragments near human settlements to continuous pristine forest, where we studied insect pollinators of two mangrove plant species, Acanthus ilicifolius and Avicennia officinalis. Our results show that different pollinator groups responded to the disturbance gradient differently. For example, the abundance of Apis dorsata, one of the three local species of honey bees, increased gradually from the village area towards the deep pristine forest. On the other hand, A. cerana and A. florea were found in the village sites and completely absent in the deep forest. Although pollinator community composition changed along the disturbance gradient, their efficacy in pollination did not seem to be significantly affected. However, lower plant diversity and low understory plant cover in the forest patches nearby the village indicated that human disturbances not only affected pollinator community composition but also played a major negative role in the regeneration of the forest. Our study provides first insights into plant-pollinator interactions in the Sundarbans and demonstrates that more research is needed to inform conservation of this unique habitat.

ecology↗

bioRxiv2020

An empirical attack tolerance test alters the structure and species richness of plant-pollinator networks

Ecological network theory hypothesizes a link between structure and stability, but this has mainly been investigated in-silico. In an experimental manipulation, we sequentially removed four generalist plants from real plant-pollinator networks and explored the effects on, and drivers of, species and interaction extinctions, network structure and interaction rewiring. Our results indicate that cumulative species and interaction extinctions increased faster with generalist plant loss than what was expected by co-extinction models, which predicted the survival or extinction of many species incorrectly. In addition, network nestedness decreased, modularity increased, and opportunistic random interactions and structural unpredictability emerged, which are all indicators of network instability and fragility. Conversely, interaction reorganization (rewiring) was high, asymmetries between network levels emerged as plants increased their centrality. From the experimental manipulations of real networks, our study shows how plant-pollinator network structure has low stability and changes towards a more fragile state when generalist plants are lost.

ecology↗

bioRxiv2019

Does a strong reduction of colony workforce affect the foraging strategy of a social pollinator?

The way pollinators gather resources may play a key role for buffering their population declines. Social pollinators like bumblebees could adjust their foraging after significant workforce reductions to keep provisions to the colony optimal, especially in terms of pollen quality, diversity, and quantity. To test what effects a workforce reduction causes on the foraging for pollen, colonies of the bumblebee Bombus terrestris were experimentally manipulated in field by removing half the number of workers. The pollen pellets of the workers were taxonomically identified with DNA metabarcoding, a ROC approach was used to filter out underrepresented OTUs, and video cameras and network analyses were employed to investigate foraging strategies and behaviour. The results suggested that the plant diversity in the pollen pellets was high but plant identity and pollen quantity traits were influenced mainly by plant phenology. During the experiment, although the treated colonies increased foraging effort in relation to control nests, only minor changes in the diet breadth and in the other node-level and network-level indices were observed after workforce removal. Therefore, a consistency in the bumblebees feeding strategies emerges despite the lowered workforce, which questions the ability of social pollinators to adjust their foraging in the field.

ecology↗

bioRxiv2018

Experimental loss of generalist plants reveals alterations in plant-pollinator interactions and a constrained flexibility of foraging

Species extinctions undermine ecosystem functioning but species do not disappear at random. Ecosystem dynamics are ruled by a subset of dominant species, but it is not clear how losing several of these key species would affect plant-pollinator interactions. We tested how the experimental loss of the most highly visited generalist plants would affect flower visitor abundances (visitation) and pollinator effectiveness (quantity of pollen-tubes within pistils) in several sites. Significant changes in the plant-pollinator communities were detected. Firstly, visitation decreased after removing 1-2 most visited plants, suggesting that these species mostly facilitate other plants by keeping high flower visitor abundances in the sites. Nevertheless, we recorded within-site variations of these trends, especially among sampled transects and among plant species, suggesting that complex facilitation-competition interactions occur among plants, but that these vary among transects within the same sites. Pollinator effectiveness fluctuated but not in a clear linear way and was not directly linked to changes of flower visitation. This suggests that fluctuations of pollinator effectiveness might be due to destabilization of the pollinators by the removal of key resources. In addition, we detected a constrained flexibility of the foraging of flower visitors because they did not switch among flower shapes and they favoured specific plant traits such as high sugar content, small inflorescences and taller plants. Indeed, these constraints would eventually limit utilisation of new resources after perturbations, possibly undermining the stability of the system. In conclusion, our work demonstrates that the loss of dominant, highly generalist plants alters plant-pollinator interactions with implications for pollination and insect foraging. Therefore, in order to preserve ecosystems, generalist plants should not get lost, because they sustain the complex pattern of interactions between plants and flower visitors.

ecology↗

bioRxiv2017

Effects Of Small-Scale Clustering Of Flowers On Pollinator Foraging Behaviour And Flower Visitation Rate

Plants often grow in clusters of various sizes and have a variable number of flowers per inflorescence. This small-scale spatial clustering affects insect foraging strategies and plant reproductive success. In our study, we aimed to determine how visitation rate and foraging behaviour of pollinators depend on the number of flowers per plant and on the size of clusters of multiple plants using Dracocephalum moldavica (Lamiaceae) as a target species. We measured flower visitation rate by observations of insects visiting single plants and clusters of plants with different numbers of flowers. Detailed data on foraging behaviour within clusters of different sizes were gathered for honeybees, Apis mellifera, the most abundant visitor of Dracocephalum in the experiments. We found that the total number of flower visitors increased with the increasing number of flowers on individual plants and in larger clusters, but less then proportionally. Although individual honeybees visited more flowers in larger clusters, they visited a smaller proportion of flowers, as has been previously observed. Consequently, visitation rate per flower and unit time peaked in clusters with an intermediate number of flowers. These patterns do not conform to expectations based on optimal foraging theory and the ideal free distribution model. We attribute this discrepancy to incomplete information about the distribution of resources. Detailed observations and video recordings of individual honeybees also showed that the number of flowers had no effect on handling time of flowers by honeybees. We evaluated the implications of these patterns for insect foraging biology and plant reproduction.

ecology↗