Biology subjects

Janecek, S.

Publications and source records attributed to Janecek, S..

10 recordsLinked to original sources

bioRxiv2026

Plant-pollinator interactions along an elevational gradient in Central European forest understorey

Elevational gradients provide a framework for understanding how environmental filtering reorganises communities and interactions, but plant-pollinator interactions along temperate forest elevational gradients remain overlooked. We studied early-spring understorey communities at four forest sites spanning the foothills towards the timberline (450-1,000 m a.s.l.) in the Krkono[s]e Mountains, Czechia. Across six transects per elevation, we quantified flowering plant species richness, floral resources and traits, and video-recorded flowers, yielding 4,003 pollinator visits. We analysed elevational patterns in species richness, community composition, floral traits, and quantitative network characteristics. Visitation frequency and flowering plant and pollinator species richness peaked at intermediate elevations. The contribution of dipteran relative to hymenopteran pollinators increased towards higher elevations, principally because of non-hoverfly flies, whereas individual bee groups showed no uniform response. Floral resources and traits showed no uniform elevational responses, although total nectar sugar availability peaked at the highest site because of the dominant Vaccinium myrtillus. Most notably, both network-level specialisation and mean species-level specialisation were generally greater at the two higher elevations, whereas nestedness was lower and other network characteristics showed no consistent patterns. These findings suggest that shifts in pollinator composition and dominant floral resources potentially shaped interactions along the gradient. The increasing specialisation with elevation contrasts with the generalisation often expected under reduced partner availability and indicates that forest networks may follow elevational patterns not predicted from open habitats. Despite limited site-level replication, this study provides, to our knowledge, the first community-wide characterisation of plant-pollinator interactions along a temperate forest elevational gradient and identifies patterns requiring evaluation across replicated gradients.

ecology↗

bioRxiv2026

Does the mid-domain effect shape interaction networks along environmental gradients?

The mid-domain effect (MDE) predicts that geometric constraints drive unimodal species richness patterns within bounded gradients. However, the role of this effect in ecological networks is currently unexplored. Here we evaluate the role of the MDE in structuring interaction networks. We combine null-model simulations and empirical analyses of plant-pollinator and ant-plant networks along elevational gradients to assess whether the MDE can drive systematic variation in network structure. Our simulations demonstrated that the MDE alone can generate unimodal/U-shaped patterns in network metrics such as connectance, generality, and vulnerability. However, empirical networks only partially conformed to MDE predictions, with deviations indicating the likely influence of other ecological processes. MDE-based models best explained patterns in network-level specialization and nestedness, while only partially explaining patterns in connectance and generality. Because MDEs can shape interaction networks, MDE null models should be used when quantifying the influence of other ecological processes on network structure.

ecology↗

bioRxiv2026

Elevational patterns in plant mating systems and pollen limitation in Afrotropical montane grasslands

O_LIPlant mating systems and pollen limitation often vary along elevational gradients, yet empirical evidence remains mixed and rarely comes from multi-species experimental studies in tropical mountain ecosystems. C_LIO_LIWe tested how elevation affects natural seed set, pollen limitation, and selfing capacity, and whether these patterns are associated with variation in flower visitation, in Afromontane grasslands on Mount Cameroon. We conducted a hand-pollination experiment on seven zoogamous plant species at four elevations above the timberline (2,300-3,800 m), applying autonomous selfing, geitonogamous selfing, outcrossing, and open-pollination treatments to 1,776 flowers and quantifying seed set. In parallel, we quantified pollinator visitation on unmanipulated plants to estimate visitation frequency, morphospecies richness, and functional-group richness. C_LIO_LINatural reproductive success of the studied plants exhibited a pronounced mid-elevation peak and declined sharply towards the summit, where pollen limitation increased strongly. At the highest elevation, some species produced few or no seeds even under outcross-pollination, indicating physiological reproductive constraints. C_LIO_LIIndices of autonomous selfing and geitonogamy varied among species, with no consistent elevational patterns. Despite detected partial self-compatibility, summit populations did not exhibit expected shifts towards selfing, suggesting limited reproductive assurance under high-elevation conditions. C_LIO_LIPollinator visitation frequency and diversity declined at the highest elevation. Natural seed set was positively associated with visitation frequency and mildly negatively associated with morphospecies richness, whereas pollen limitation and selfing indices showed no clear relationships with visitation metrics, consistent with the influence of additional physiological and developmental constraints on reproduction. C_LIO_LISynthesis. Our study shows that in isolated Afrotropical montane grasslands, plant reproductive success at high elevations is jointly constrained by declining pollination service and abiotic limitations, which is not compensated by increased selfing. This suggests that successful plant reproduction near upper vegetation limits depends on both sufficient pollination service and favourable physiological conditions. Under ongoing climate change, upslope range shifts of plants may therefore not guarantee reproductive success if plant and pollinator responses to warming are asynchronous or if a part of extreme high-elevation conditions remain limiting. These findings advance understanding of how biotic interactions and abiotic constraints together shape plant reproduction along tropical elevational gradients. C_LI

plant biology↗

bioRxiv2025

Elevational patterns in two groups of micromoths (Lepidoptera: Pterophoridae, Alucitidae) in tropical forests of Mount Cameroon

Tropical elevational gradients offer unique insights into ecological processes shaping biodiversity, although micromoths remain severely understudied, especially in the Afrotropics. We analysed species richness, community composition, and functional traits (elevational range size and wingspan) of two micromoth families, many-plumed moths (Alucitidae) and plume moths (Pterophoridae), along a complete forest gradient on Mount Cameroon, an Afrotropical biodiversity hotspot. Alucitidae exhibited a distinct mid-elevation diversity peak, mirroring common patterns in tropical butterflies and moths, whereas Pterophoridae showed an uncommon upslope increase in species richness. Both families demonstrated clear elevational turnover in community composition, indicative of strong environmental filtering. Additionally, community-weighted elevational range size and wingspan increased consistently with elevation, supporting Rapoports rule and Bergmanns cline, respectively. These patterns likely reflect interactions among climatic factors and environmental complexity, though the underlying mechanisms remain unresolved. Our findings reveal the unique communities of both mid- and high-elevation forests, as well as the distinctiveness of species-poor lowland assemblages. This elevational differentiation underscores the need for conservation across the full gradient and the vulnerability of endemic highland taxa to climate-driven range contractions. Comprehensive research on neglected tropical insect groups is urgently needed to better anticipate biodiversity responses to environmental change.

ecology↗

bioRxiv2025

Butterfly and moth habitat specialisation changes along an elevational gradient of tropical forests on Mount Cameroon

Niche breadth is a key ecological trait influencing species distribution, persistence, vulnerability to environmental change, and interspecific interactions. While the elevational niche-breadth hypothesis predicts broader ecological niches at higher elevations due to increased environmental stress and heterogeneity, empirical tests have mostly focused on food specialisation, with habitat specialisation remaining largely overlooked. Here, we provide the first direct test of this hypothesis using habitat characteristics, analysing fruit-feeding butterflies and moths along a complete tropical forest gradient on Mount Cameroon. We quantified habitat-related niche breadth using the Outlying Mean Index across 96 forest plots spanning 350-2200 m a.s.l., employing two complementary metrics: absolute niche breadth (ANB) based on the total range of habitat conditions occupied across the gradient, and within-elevation niche breadth (WENB) reflecting the proportion of local habitat heterogeneity utilized at each elevation. Forest structural heterogeneity increased steeply with elevation. In response, butterfly communities showed a substantial upslope broadening of ANB, particularly in Charaxinae and Satyrinae. Moth families exhibited similar but weaker patterns. In contrast, WENB showed no consistent elevational patterns and was more variable among lepidopteran groups. These results support the elevational niche-breadth hypothesis for habitat specialisation in tropical butterflies, likely reflecting increased habitat opportunity space and reduced competition at higher elevations. However, the decoupling of ANB and WENB highlights that broader availability of environmental conditions does not necessarily translate into more generalised local habitat use, suggesting constraints from behavioural preferences, resource distributions, or biotic interactions. By disentangling overall and local habitat niche breadths, our study reveals unrecognised complexity in elevational specialisation patterns and provides new insights into how tropical insect respond to environmental gradients.

ecology↗

bioRxiv2022

The Ruminococcus bromii amylosome protein Sas6 binds single and double helical α-glucan structures in starch.

Resistant starch is a prebiotic with breakdown by gut bacteria requiring the action of specialized amylases and starch-binding proteins. The human gut symbiont Ruminococcus bromii expresses granular starch-binding protein Sas6 (Starch Adherence System member 6) that consists of two starch-specific carbohydrate binding modules from family 26 (RbCBM26) and family 74 (RbCBM74). Here we present the crystal structures of Sas6 and RbCBM74 with a double helical dimer of maltodecaose bound along an extended surface groove. Binding data combined with native mass spectrometry suggest that RbCBM26 binds short maltooligosaccharides while RbCBM74 can bind single and double helical -glucans. Our results support a model by which RbCBM74 and RbCBM26 bind neighboring -glucan chains at the granule surface. CBM74s are conserved among starch granule-degrading bacteria and our work provides molecular insight into how this structure is accommodated by select gut species.

molecular biology↗

bioRxiv2022

Cheaters among pollinators: Floral traits drive spatiotemporal variation in nectar robbing and thieving in Afrotropical rainforests

O_LINectar robbing and thieving can substantially affect the reproduction of animal-pollinated plants. Although the intensity of nectar exploitation remains unexplored at the community level, it probably varies along environmental gradients. C_LIO_LIWe video-recorded flower visits to animal-pollinated plants in Afrotropical rainforests along a complete elevational gradient in the wet and dry seasons on Mount Cameroon. We analysed how the proportion of nectar robbing and thieving in the communities changes spatiotemporally, especially in association with the floral traits of the flowering plants. C_LIO_LIWe recorded 14,391 flower visits, of which ~4.3% were from robbers (mostly bees and birds), and ~2.1% were from thieves (mostly flies, bees, and moths). Of the 194 studied plants, only 29 and 39 were nectar robbed and thieved, respectively. Robbers and thieves were most frequent at mid-elevations, with more frequent robbing in the wet season and thieving in the dry season. These trends were linked to the local composition of floral traits, and cheating groups associations to particular traits. Floral traits that prevented thieving made flowers susceptible to robbing, and vice versa. C_LIO_LISpatiotemporal variation in floral traits across drives the cheating behaviour of flower visitors across communities, while indicating a trade-off between preventing nectar robbing and thieving. C_LI

ecology↗

bioRxiv2021

Role and patterns of butterflies and hawkmoths in plant-pollinator networks at different elevations and seasons in tropical rainforests of Mount Cameroon

O_LIButterflies and moths are well-visible flower visitors. Nevertheless, almost no quantification of their role in plant-pollinator interactions exists at a community level, especially from tropical rainforests. Moreover, we have virtually no knowledge on environmental and other factors affecting lepidopteran flower visits. C_LIO_LIWe focused on the role of butterflies and hawkmoths as flower visitors in tropical rainforests of Mount Cameroon, especially on its elevational and seasonal changes. We also analysed their preferences to selected floral traits, with a specific focus on pollination syndromes. C_LIO_LIWe video-recorded flower visitors of 1,115 specimens of 212 plant species (>26,000 recording hrs) along the complete elevational gradient of rainforests in two main seasons, and compared frequencies of flower-visiting lepidopterans to other visitors. We compared characteristics of plant-lepidopteran networks among elevations and seasons, and analysed patterns of selected lepidopteran traits. Finally, we analysed inter-family differences in their floral preferences. C_LIO_LIAltogether, we recorded 734 flower visits by 80 butterflies and 27 hawkmoth species, representing only ~4% of all 18,439 flower visits. Although lepidopterans visited only a third species, they appeared key visitors of several plants. The most flower visits by lepidopterans were recorded in mid-elevations and dry season, mirroring the general patterns of lepidopteran diversity. The networks showed no apparent elevational or seasonal patterns, probably because of the surprisingly high specialisation of interactions in all networks. Significant non-linear changes of proboscis and forewing lengths were found along elevation, and long-proboscid hesperiid butterflies visited flowers with longer tubes or spurs. Substantial differences in floral preferences were found between sphingids, and papilionid, nymphalid and lycaenid butterflies, revealing importance of nectar production, floral size and shape for sphingids, and floral colour for butterflies. C_LIO_LIButterflies and hawkmoths were confirmed as relatively minor visitors of tropical forest flowers, although they seemed crucial for pollination of some plant species. Moreover, the revealed floral preferences and trait-matchings confirmed a potential of some lepidopteran families to drive floral evolution in tropical ecosystems. C_LI

ecology↗

bioRxiv2020

Spatiotemporal shifts in the role of floral traits in shaping tropical plant-pollinator interactions

The pollination syndrome hypothesis predicts that plants pollinated by the same pollinator group bear convergent combinations of specific floral traits. Nevertheless, some studies have shown relatively low predictive power for these floral trait combinations. This discrepancy may be caused by changes in the importance of specific floral traits for shaping interactions under different environmental conditions and for different pollinator groups. To test this, we studied pollination systems and floral traits along an elevational gradient on Mount Cameroon during wet and dry seasons. Using Random Forest models, allowing the ranking of traits by significance, we demonstrated that some floral traits are more important than others in shaping interactions and that these traits predict pollinators relatively well. However, the distribution and importance of traits varies under different environmental conditions. Our results imply the need to improve our trait-based understanding of plant-pollinator interactions to better inform the debate surrounding pollination syndrome hypothesis.

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↗