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Patterns of seasonality in species composition with elevation. (a) Patterns of seasonal species turnover (ranges from 0 to 1) with elevation. High values indicate that a seasonal change of species mainly drives seasonal β‐diversity on study plots with species differing among seasons. (b) Patterns of nestedness in species communities (ranges from 0 to 1) with elevation. High values indicate the species communities in species‐poor seasons are nested subsets of those found in the species‐rich season. All diversity trends were analyzed using generalized additive models (Gaussian family, basis dimension k = 5). Dots represent observed values of turnover and nestedness per study plot
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The contribution of seasonality in species communities to elevational diversity of tropical insects remains poorly understood. We here assessed seasonal patterns and drivers of bee diversity in the Eastern Afromontane Biodiversity Hotspot, Kenya, to understand the contribution of seasonality to elevational biodiversity patterns. Bee species and pla...
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Many plant species in high montane ecosystems rely on animal pollination for sexual reproduction, however, our understanding of plant-pollinator interactions in tropical montane habitats is still limited. We compared species diversity and composition of blooming plants and floral visitors, and the structure of plant-floral visitor networks between...
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... For many animals, population and community structure can often show dramatic temporal patterning, driven by both biotic factors, such as competition and facilitation, and abiotic factors like temperature, rainfall, and photoperiod (Chesson, 2000;Dzekashu et al., 2022;Mellard et al., 2019;Ricklefs, 2004;Shimadzu et al., 2013). When turnover in species composition and abundance is synchronized to changes in seasons, usually referred to as a "season-diversity relationship", species diversity typically peaks during the warmest time of year when primary productivity is highest (Mellard et al., 2019). ...
The seasonal use of caves by bats can be attributed to physiologically demanding activities like mating and reproductions or torpor. Although cave use varies intra- and inter-specifically in bats, the microclimatic characteristics of roost sites have significant implications for the fitness of bat populations. As these microclimates are increasingly influenced by surface level climatic changes, understanding the current patterns of cave utilization is crucial to assess the impact of climate change on bats. Therefore, we monitored cave temperatures and studied the diversity and abundance of bats in 41 caves across a seasonal (mid-winter, late-winter and early-spring) and an elevational (400 to 2700 meters above sea level) gradient in the Central Himalayas. The richness and abundance of bat species exhibited seasonal variations, with more species and individuals present during early spring (n = 15) compared to mid-winter (n = 9). Species richness exhibited a linear decline with elevation in mid-winter, but remained relatively stable until 900 msl and then declined in late-winter and early-spring. Furthermore, species such as Hipposideros armiger (20.14 ± 1.60°C in spring and 17.97 ± 0.88°C in mid-winter), Rhinolophus affinis (19.98 ± 1.76°C in spring and 16.18 ± 3.09°C in mid-winter) and Rhinolophus cf. pusillus (19.55 ± 1.64°C in spring and 15.43 ± 2.87°C in mid-winter) preferred warmer microclimates during early-spring compared to mid-winter. This season- and species- specific cave use suggests that even minor fluctuations in cave temperatures could potentially alter the composition of bat communities inside caves. We recommend that long-term studies in such highly diverse climate vulnerable areas would help understand and predict the responses of cave-dwelling bats to climate change.
... The composition of bee communities can greatly change with season (e.g. dry and rainy seasons; see Dzekashu et al., 2022;Samnegård et al., 2015), mediated by changes in floral resources availability and plant species composition (Fisogni et al., 2020). Although similar results have been reported in other studies conducted in different environments (e.g. ...
Urbanization is a major driver of biodiversity change but how it interacts with spatial and temporal gradients to influence the dynamics of plant–pollinator networks is poorly understood, especially in tropical urbanization hotspots. Here, we analysed the drivers of environmental, spatial and temporal turnover of plant–pollinator interactions (interaction β‐diversity) along an urbanization gradient in Bengaluru, a South Indian megacity. The compositional turnover of plant–pollinator interactions differed more between seasons and with local urbanization intensity than with spatial distance, suggesting that seasonality and environmental filtering were more important than dispersal limitation for explaining plant–pollinator interaction β‐diversity. Furthermore, urbanization amplified the seasonal dynamics of plant–pollinator interactions, with stronger temporal turnover in urban compared to rural sites, driven by greater turnover of native non‐crop plant species (not managed by people). Our study demonstrates that environmental, spatial and temporal gradients interact to shape the dynamics of plant–pollinator networks and urbanization can strongly amplify these dynamics.
... This implies that a plant-insect-pollinator network's robustness is dependent on quality of the environment. 28,30,35,44,48,50 Consequently, any change in pollinator diversity due to human disturbance in the environment or ecological systems can negatively affect plant-pollinator interactions. 31 This is supported by the fewer plant-insect-pollinator interactions and lower values of specialization index in our disturbed study areas. ...
... The lower values of the interaction metrics in disturbed areas could also be due to lower insect-pollinator diversity. 30,41,[50][51][52][53][54] Since semi-natural study areas had high nestedness, we show that communities with more plant-insect-pollinator interactions are much more nested. 28,31 Also, these areas exhibited more stable interactions as seen by their high connectance as compared to disturbed areas. ...
... 23,24,53 Essentially, high connectance infers resilience and network stability in semi-natural areas. 31,53,54 On the other hand, fewer plant-insect-pollinator interactions in disturbed areas account for decreased network nestedness and connectance., 48,50,51 In general, the difference in network metrics between disturbed and semi-natural areas is largely due to the variations in species richness and abundance, as well as floral abundance, brought on by anthropogenic activities and changes in land use. 52 Despite the fact that disturbed areas had lower insect-pollinator abundance, diversity, and species richness as well as fewer insect-pollinator interactions, our findings suggest that both disturbed and semi-natural areas are potential habitats for insect-pollinators. ...
Due to inadequate insect-pollinator data, particularly in sub-Saharan African countries like Tanzania, it is difficult to manage and protect these species in disturbed and semi-natural areas. Field surveys were conducted to assess insect-pollinator abundance and diversity and their interactions with plants in disturbed and semi-natural areas in Tanzania's Southern Highlands using pan traps, sweep netting, transect counts, and timed observations techniques. We found that species diversity and richness of insect-pollinators were high in semi-natural areas, and there was 14.29% more abundance than in disturbed areas. The highest plant-pollinator interactions were recorded in semi-natural areas. In these areas, the total number of visits by Hymenoptera was more than three times that of Coleoptera, while that of Lepidoptera and Diptera was more than 237 and 12 times, respectively. Hymenoptera pollinators had twice the total number of visits of Lepidoptera, and threefold of Coleoptera, and five times more visits than Diptera in disturbed habitats. Although disturbed areas had fewer insect-pollinators and fewer plant-insect-pollinator interactions, our findings indicate that both disturbed and semi-natural areas are potential habitats for insect-pollinators. The study revealed that the over-dominant species Apis mellifera could influence diversity indices and network-level metrics in the study areas. When A. mellifera was excluded from the analysis, the number of interactions differed significantly between insect orders in the study areas. Also, Diptera pollinators interacted with the most flowering plants in both study areas compared to Hymenopterans. Though A. mellifera was excluded in the analysis, we found a high number of species in semi-natural areas compared to disturbed areas. Conclusively, we recommend that more studies be conducted in these areas across sub-Saharan Africa to unveil their potential for protecting insect-pollinators and how ongoing anthropogenic changes threaten them.
... Recent analyses at the global scale confirm the bimodal latitudinal bee richness gradient proposed by Michener (1979). Specifically, climate and resource availability (i.e., vegetation communities) have arisen as the main drivers of bee diversity worldwide (Bystriakova et al., 2018;Orr et al., 2021) and regionally (Dzekashu et al., 2022;Sponsler et al., 2022). Moreover, anthropogenic stress in the form of land-use change negatively affects wild bee α and β diversity for Palearctic bees at the continental (Bystriakova et al., 2018) andsmaller scales (e.g., De Palma et al., 2017;Moroń et al., 2012). ...
Wild bees are critical for multiple ecosystem functions but are currently threatened. Understanding the determinants of the spatial distribution of wild bee diversity is a major research gap for their conservation. We modeled wild bee α and β taxonomic and functional diversity in Switzerland to uncover countrywide diversity patterns and determine the extent to which they provide complementary information, assess the importance of the different drivers structuring wild bee diversity, identify hotspots of wild bee diversity, and determine the overlap between diversity hotspots and the network of protected areas. We used site‐level occurrence and trait data from 547 wild bee species across 3343 plots and calculated community attributes, including taxonomic diversity metrics, community mean trait values, and functional diversity metrics. We modeled their distribution with predictors describing gradients of climate, resource availability (vegetation), and anthropogenic influence (i.e., land‐use types and beekeeping intensity). Wild bee diversity changed along gradients of climate and resource availability; high‐elevation areas had lower functional and taxonomic α diversity, and xeric areas harbored more diverse bee communities. Functional and taxonomic β diversities diverged from this pattern, with high elevations hosting unique species and trait combinations. The proportion of diversity hotspots included in protected areas depended on the biodiversity facet, but most diversity hotspots occurred in unprotected land. Climate and resource availability gradients drove spatial patterns of wild bee diversity, resulting in lower overall diversity at higher elevations, but simultaneously greater taxonomic and functional uniqueness. This spatial mismatch among distinct biodiversity facets and the degree of overlap with protected areas is a challenge to wild bee conservation, especially in the face of global change, and calls for better integrating unprotected land. The application of spatial predictive models represents a valuable tool to aid the future development of protected areas and achieve wild bee conservation goals.
... Along elevational gradients, abiotic and biotic factors, such as climate or resource availability change over very small spatial scales (Körner, 2007), which can fundamentally restructure species communities (Sponsler et al., 2022). However, while many studies have centered on the impact of elevation on abundance and species richness of individual taxonomic or trophic groups (e.g., plants or pollinators) (Dzekashu et al., 2022;Maicher et al., 2018;Peters et al., 2016), there still remains an apparent dearth of studies addressing patterns and drivers of species interaction networks with elevation (Hoiss et al., 2015;Maunsell et al., 2015), especially on tropical mountains (Classen et al., 2020;Mertens et al., 2021;Ramos-Jiliberto et al., 2010). ...
... The impact of elevation and seasonal changes in climate (Dzekashu et al., 2022) on plant-pollinator interaction networks still remains elusive for tropical elevation gradients. Seasonality substantially influences plant phenology and animal physiology at both high and low latitudes (Thuiller, 2007). ...
... Farming and grazing activities are equally carried out and several honeybee hives are deployed by local indigenes into the forested highlands. Along the elevation gradient, the landscape is made up of savannah, shrublands, indigenous bushlands, pasture, and human settlement with some subsistence farming activities (Dzekashu et al., 2022). Seasonality in climate is pronounced in the study region. ...
Across an elevation gradient, several biotic and abiotic factors influence community assemblages of interacting species leading to a shift in species distribution, functioning, and ultimately topologies of species interaction networks. However, empirical studies of climate-driven seasonal and elevational changes in plant-pollinator networks are rare, particularly in tropical ecosystems. Eastern Afromontane Biodiversity Hotspots in Kenya, East Africa. We recorded plant-bee interactions at 50 study sites between 515 and 2600 m asl for a full year, following all four major seasons in this region. We analysed elevational and seasonal network patterns using generalised additive models (GAMs) and quantified the influence of climate, floral resource availability, and bee diversity on network structures using a multimodel inference framework. We recorded 16,741 interactions among 186 bee and 314 plant species of which a majority involved interactions with honeybees. We found that nestedness and bee species specialisation of plant-bee interaction networks increased with elevation and that the relationships were consistent in the cold-dry and warm-wet seasons respectively. Link rewiring increased in the warm-wet season with elevation but remained indifferent in the cold-dry seasons. Conversely, network modularity and plant species were more specialised at lower elevations during both the cold-dry and warm-wet seasons, with higher values observed during the warm-wet seasons. We found flower and bee species diversity and abundance rather than direct effects of climate variables to best predict modularity, specialisation, and link rewiring in plant-bee-interaction networks. This study highlights changes in network architectures with elevation suggesting a potential sensitivity of plant-bee interactions with climate warming and changes in rainfall patterns along the elevation gradients of the Eastern Afromontane Biodiversity Hotspot.
... temperature and rainfall seasonality on several indices. It has already been showed that seasonality strongly impacts diversity of communities in tropical terrestrial ecosystems (Correa et al., 2021;Dzekashu et al., 2022;Oita et al., 2021) but few studies highlighted such a result in lotic ecosystems, especially temperate (Epele et al., 2022;Li et al., 2019). Most studies in lotic ecosystems (Faulks et al., 2011) but also in other ecosystems highlighted the predominance of environmental factors such as altitude or temperature seasonality (Howard et al., 2019). ...
Evaluating the effects of anthropogenic pressures on several biodiversity metrics can inform the management and monitoring of biodiversity loss. However, the type of disturbances can lead to different responses in different metrics. In this study, we aimed at disentangling the effects of different types of anthropogenic disturbances on freshwater fish communities. We calculated diversity indices for 1109 stream fish communities across France by computing richness and evenness components for ecological, morphological, and phylogenetic diversity, and used null models to estimate standardized effect sizes. We used generalized linear mixed models to assess the relative effects of environmental and anthropogenic drivers in driving those diversity indices. Our results demonstrated that all diversity indices exhibited significant responses to both climatic conditions and anthropogenic disturbances. While we observed a decrease of ecological and phylogenetic richness with the intensity of disturbance, a weak increase in morphological richness and evenness was apparent. Overall, our results demonstrated the importance of disentangling various types of disturbances when assessing human‐induced ecological impacts and highlighted that different facets of diversity are not impacted identically by anthropogenic disturbances in stream fish communities. This calls for further work seeking to integrate biodiversity responses to human disturbances into a multifaceted framework, and could have beneficial implications when planning conservation action in freshwater ecosystems.
