Decline In Species Richness Research Articles

From backyard to backcountry: changes in mammal communities across an urbanization gradient

Abstract Urbanization often results in biodiversity loss and homogenization, but this result is not universal and there is substantial variability in the spatiotemporal effects of urbanization on wildlife across cities and taxa. Areas with lower population and housing density are some of the fastest-growing regions in the western United States; thus, more research in these areas could offer additional insight into the effects of urbanization on wildlife and the potential importance of wild spaces in maintaining a diverse biotic community surrounding developed areas. To address this need, we conducted a study to identify the effects of urbanization (i.e. housing density) on mammals along a housing density gradient from wilderness to suburbia in Missoula, Montana. We deployed 178 motion-activated trail cameras at random sites within urban/suburban, exurban, rural, and wild regions from May to October 2019 to 2020. We identified all mammals >150 g, then evaluated how housing density influenced: (i) occupancy and (ii) species richness using multispecies occupancy models; (iii) relative abundance using Poisson models; and (iv) diel activity patterns using kernel density estimation and logistic regression. Urbanization was the strongest driver of mammal distribution, with a linear decline in mammal species richness as housing density increased. Urbanization also had strong effects on occupancy and detection rates, with larger-bodied mammals generally having stronger negative associations. Overall, mammal relative abundance was highest in suburban regions; however, this effect was largely driven by White-tailed Deer. Natural environmental factors explained most changes in mammal nocturnal activity; however, urbanization strongly affected nocturnality in some species, with Black Bear and White-tailed Deer becoming more nocturnal and Red Fox and Northern Raccoon becoming less nocturnal as housing density increased. While our study confirms that some mammals can live and thrive in developed areas, it emphasizes the importance of maintaining wild areas for those species that cannot.

Marine latitudinal diversity gradients are generally absent in intertidal ecosystems.

Current latitudinal diversity gradient (LDG) meta-analyses have failed to distinguish one of the most widespread marine habitats, the intertidal zone, as a separate system despite it having unique abiotic challenges and spatially compressed stress gradients that affect the distribution and abundance of resident species. We address this issue by revisiting published literature and datasets on LDGs since 1911 to explore LDG patterns and their strengths in intertidal benthic, subtidal benthic, and pelagic realms and discuss the importance of recognizing intertidal ecosystems as distinct. Rocky shorelines were the most studied intertidal ecosystem encompassing 64.2% of intertidal LDG studies, and 62.9% of studies focused on assemblage composition, while the remaining 37.1% of studies were taxa specific. While our analyses confirmed LDGs in subtidal benthic and pelagic realms, with a decrease in richness toward the poles, we found no consistent intertidal LDGs in any ocean or coastline across hemispheres or biodiversity unit. Analyzing intertidal and subtidal zones as separate systems increased the strength of subtidal benthic LDGs relative to analyses combining these systems. We demonstrate that in intertidal ecosystems across oceans in both hemispheres, a latitudinal decrease in species richness is not readily apparent, which stands in contrast with significant LDG patterns found in the subtidal realm. Intertidal habitat heterogeneity, regional environmental variability and biological interactions can create species-rich hot spots independent of latitude, which may functionally outweigh a typical latitudinal decline in species richness. Although previous work has shown weaker LDGs in benthic than pelagic systems, we demonstrate that this is caused by combining subtidal and intertidal benthic ecosystems into a single benthic category. Thus, we propose that subtidal and intertidal ecosystems cannot be combined into one entity as the physical and biological parameters controlling ecosystem processes are vastly different, even among intertidal ecosystems. Thus, the intertidal zone offers a unique model system in which hypotheses can be further tested to better understand the complex processes underlying LDGs.

Protective Effects of Different Selenium Green Tea Polysaccharides on the Development of Type 2 Diabetes in Mice.

Selenium polysaccharides have attracted significant interest due to their superior function to that of individual polysaccharides. However, limited research has compared the protective effects of different selenium polysaccharides from different selenization methods on diabetes. This work aims to compare the preventive effects of natural selenium-enriched green tea polysaccharides (NSe-TPS), synthetic selenized green tea polysaccharides (PCSe-TPS), and a mixture of sodium selenite and green tea polysaccharides (ordinary tea polysaccharides (Ord-TPS)+Se) on the development of diabetes. While establishing a diabetes model induced by a high-sugar, high-fat diet combined with streptozotocin, different selenium polysaccharides were administered daily by gavage for nine weeks. Our findings indicate that PCSe-TPS exhibited superior preventive effects on developing type 2 diabetes compared to NSe-TPS and Ord-TPS+Se. PCSe-TPS effectively regulated glucose metabolism and insulin resistance by activating the PI3K/Akt pathway, thereby preventing elevated blood glucose levels. Additionally, PCSe-TPS mitigated oxidative damage and inflammatory responses in liver tissues. Notably, PCSe-TPS intervention reversed the decline in bacterial species richness and the abundance of unclassified_Oscillospiraceae during the development of diabetes in mice. These results provide valuable insights into the protective effects of PCSe-TPS against diabetes development, highlighting its advantages over NSe-TPS and Ord-TPS+Se.

Fagus diversification in China in relation to East Asian monsoon evolution

When and how the extraordinary species diversity in subtropical East Asia formed is intensely debated, and the available evidence is often inconsistent. In this study, we evaluate the effects of pre- and post- Quaternary events on the evolutionary and biogeographic history of Chinese beech (Fagus species that now occur in China) to gain new insights into the historical establishment and future fate of the East Asian subtropical forest (EASF). A series of approaches and datasets were used to reconstruct biogeographic and evolutionary history of the Chinese beech. They include phylogeography based on the polymorphisms of the complete chloroplast genomes, species distribution models, and a large palaeobiogeographic dataset including 59 pre-Quaternary fossil records, 296 Quaternary fossil records and 3515 modern pollen records. Our multidisciplinary approach suggests that (i) Chinese beech has dispersed to subtropical East Asia and diversified in the early Miocene when the Asian monsoon (AM) intensified; (ii) the last post-glacial warming resulted in limited poleward displacement but significant contraction at southern and lower elevations; (iii) the poleward dispersal of Chinese beech was limited by drought in the early growing season in temperate China, controlled by the East Asian summer monsoon. Our results support the hypothesis that the establishment of the EASF is closely related to the evolution of the AM. More importantly, we suggest that with continued climate warming (e.g., during the last post-glacial period or under current climate change), the monsoon probably hindered rather than promoted the persistence of deciduous beech species, resulting in a decline in species richness.

Using high-throughput sequencing to investigate summer truffle consumption by chipmunks in relation to retention forestry

Intensive management of forests for wood modifies forest biodiversity, affecting the composition of plant and animal communities as well as microorganisms such as bacteria and fungi. Ectomycorrhizal fungi (EMF) form mutualistic relationships with trees, but there is evidence that the abundance and diversity of EMF declines under intensive forest management. The dispersal of some EMF, including that of truffles, depends on small mammals consuming their fruiting bodies and dispersing spores through feces. To better understand provisioning of this ecosystem service within intensively managed forests, we applied high-throughput, DNA amplicon sequencing to scat collected from Townsend’s chipmunks (Neotamias townsendii) inhabiting retention patches in recently clearcut-conifer stands. Across two summers, we collected 165 chipmunk scat samples from 43 clearcut-conifer stands in the Pacific Northwest (USA). We identified 81 truffle species representing 16 families, which included many rare and uncommon taxa. Retention patch sizes varied from 9 to 222 trees (0.002–0.83 ha) but we did not detect an effect of retention patch size on the richness of truffles in chipmunk scat samples. However, truffle richness was slightly higher in scat samples collected from chipmunks in retention patches compared to individuals sampled in adjacent clearcuts. Furthermore, the abundance of certain truffle species in chipmunk scat varied in relation to retention patch size and location (riparian or upland), suggesting retention forestry practices may influence truffle community composition. Throughout the sampling season, we detected a 44% decline in truffle species richness and a significant reduction in abundance (i.e., sequence reads) for > 50% of common truffle taxa. Our application of high-throughput sequencing of scat effectively captured variation in truffle species consumption by chipmunks. Our results confirm that common small mammals play an important role in the dispersal of EMF across recently logged forests (<8 years since harvest) and indicate that retaining relatively small (∼10 tree) green-tree patches may promote truffle dispersal by providing small mammal habitat.

Climate change filtered out resource-acquisitive plants in a temperate grassland in Inner Mongolia, China.

Global climate change has led to the decline of species and functional diversity in ecosystems, changing community composition and ecosystem functions. However, we still know little about how species with different resource-use strategies (different types of resource usage and plant growth of plants as indicated by the spectrum of plant economic traits, including acquisitive resource-use strategy and conservative resource-use strategy) would change in response to climate change, and how the changes in the diversity of species with different resource-use strategies may influence community-level productivity. Here, using long-term (1982-2017) observatory data in a temperate grassland in Inner Mongolia, we investigated how climate change had affected the species richness (SR) and functional richness (FRic) for the whole community and for species with different resource-use strategies. Specifically, based on data for four traits representing leaf economics spectrum (leaf carbon concentration, leaf nitrogen concentration, leaf phosphorus concentration, and specific leaf area), we divided 81 plant species appearing in the grassland community into three plant functional types representing resource-acquisitive, medium, and resource-conservative species. We then analyzed the changes in community-level productivity in response to the decline of SR and FRic at the community level and for different resource-use strategies. We found that community-level SR and FRic decreased with drying climate, which was largely driven by the decline of diversity for resource-acquisitive species. However, community-level productivity remained stable because resource-conservative species dominating this grassland were barely affected by climate change. Our study revealed distinctive responses of species with different resource-use strategies to climate change and provided a new approach based on species functional traits for predicting the magnitude and direction of climate change effects on ecosystem functions.

Human-modified landscapes driving the global primate extinction crisis.

The world's primates have been severely impacted in diverse and profound ways by anthropogenic pressures. Here, we evaluate the impact of various infrastructures and human-modified landscapes on spatial patterns of primate species richness, at both global and regional scales. We overlaid the International Union for the Conservation of Nature (IUCN) range maps of 520 primate species and applied a global 100 km2 grid. We used structural equation modeling and simultaneous autoregressive models to evaluate direct and indirect effects of six human-altered landscapes variables (i.e., human footprint [HFP], croplands [CROP], road density [ROAD], pasture lands [PAST], protected areas [PAs], and Indigenous Peoples' lands [IPLs]) on global primate species richness, threatened and non-threatened species, as well as on species with decreasing and non-decreasing populations. Two-thirds of all primate species are classified as threatened (i.e., Critically Endangered, Endangered, and Vulnerable), with ~86% experiencing population declines, and ~84% impacted by domestic or international trade. We found that the expansion of PAST, HFP, CROP, and road infrastructure had the most direct negative effects on primate richness. In contrast, forested habitat within IPLs and PAs was positively associated in safeguarding primate species diversity globally, with an even stronger effect at the regional level. Our results show that IPLs and PAs play a critical role in primate species conservation, helping to prevent their extinction; in contrast, HFP growth and expansion has a dramatically negative effect on primate species worldwide. Our findings support predictions that the continued negative impact of anthropogenic pressures on natural habitats may lead to a significant decline in global primate species richness, and likely, species extirpations. We advocate for stronger national and international policy frameworks promoting alternative/sustainable livelihoods and reducing persistent anthropogenic pressures to help mitigate the extinction risk of the world's primate species.

Changes in the wild bee community (Hymenoptera: Apoidea) over 100 years in relation to land use: a case study in a protected steppe habitat in Eastern Austria

The wild bee community of a sand steppe habitat in Eastern Austria was surveyed in the years 2018 and 2019, complemented with historical data from over 100 years, and analyzed in relation to land use change. The mapping of land use categories was based on historical aerial photographs and orthophotos. Changes in bee community composition were analyzed by a multivariate statistical approach and took ecological traits into account (lecty, nesting type, habitat requirements, flight period, parasitism). In total, 310 bee species were recorded in the area, with the oldest records dating back to 1882. The bee species composition differed significantly among four defined time periods. Across the two most intensively sampled time periods (1931–1966 vs 2001–2021), a decline in species richness of over 50% was observed. We observed a disproportionally high decline of steppe- and sand-associated species, and a distinct shift from ground nesting species to above-ground nesting species. The area covered with woods increased from 1966 to 2018, while the total area covered with grassland and fallows decreased slightly between 1966 and 1994. The oligolectic species assemblage was specialized on Dipsacaceae, Brassicaceae and Fabaceae in the two earlier periods, and on Asteraceae and specifically on Carduoideae during the two later ones.Implications for insect conservationstronger reference to historic land management practices as short time periods of intensive grazing and small-scaled, staggered mowing would be desirable to improve the habitat quality. More drastic measures, such as removal of the topsoil in some parts and changes in the landscape re-establishing exposure to wind erosion, might be necessary, if the area is to be fully restored to the condition it was in a century ago.

Comparison of survey methods for fungi using metabarcoding and fruit body inventories in an altitudinal gradient.

Metabarcoding of environmental samples is nowadays an established method in biodiversity research. When it comes to studying fungal populations in various ecotypes, fruit body inventories are the traditional method to assess the diversity of fungal communities. In this study, both methods-metabarcoding of soil samples and a traditional fruit body inventory-were conducted on 144 sample plots in an altitudinal gradient in the Bavarian Forest (Germany) and the results were compared. Metabarcoding detected significantly more species than the traditional fruit body inventory. The majority of taxa recorded in the fruit body inventory belonged to the Basidiomycota, whereas in the metabarcoding data, the distribution of species between Basidiomycota and Ascomycota was approximately balanced. Species of several orders forming inconspicuous or hypogeous fruit bodies were detected only by metabarcoding, while several wood decomposers were recorded only in the fruit body inventory. The proportion of detected wood-colonising species with melanized spores was considerably higher with metabarcoding than with the fruit body inventory, where more than 70% of recorded wood-colonisers had hyaline spores. Based on the metabarcoding data, a decline of species richness with increasing altitude was evident, but this was not visible in the fruit body inventory data. Detrended correspondence analyses yielded similar results for relative species community similarities with both survey methods.

The Filtering Effect of Oil Palm Plantations on Potential Insect Pollinator Assemblages from Remnant Forest Patches

Extensive oil palm plantations worldwide are dependent on insect pollination, specifically by introduced African weevils (Elaidobius spp.). The effectiveness of these weevils has been questioned following poor pollination and yield loss in Malaysia. Indigenous thrip (Thysanoptera) species, and moths (Lepidoptera) in the genus Pyroderces, may also be pollinators of oil palm, while the role of bees (Hymenoptera) and flies (Diptera) is unknown. The potential of native pollinators remains uncertain because of the almost total clearing of forest habitat from oil palm landscapes. In this study, we investigate the value of small high conservation value (HCV) forests as sources of potential native insect pollinators of oil palm in northern Sarawak. We further examine the filtering effect of oil palm-dominated landscapes on the species assemblages of six potential pollinator insect orders: Blattodea, Coleoptera, Diptera, Hemiptera, Hymenoptera and Lepidoptera. Orders differed in both species composition and abundance between forest and oil palm plantations, with an average of 28.1% of species unique to oil palm. Oil palm presented a soft permeable boundary to Coleoptera, Hymenoptera and Lepidoptera. Their species richness and abundance differed little between habitats with distance, despite species turnover. In contrast, oil palm presented a harder boundary to Diptera with a decline in both species richness and abundance with distance into oil palm. The abundance of the oil palm weevil (Elaedobius kamerunicus) was low compared to the native dominants, but similar to levels displayed by native thrips that may be pollinators of oil palm. The functional diversity of well-known pollinator guilds—bees and flies—was similar in forest and oil palm, suggesting that potential pollinators may yet exist among native orders of insects. Contrary to the prevailing opinion, even small forest patches in oil palm landscapes may provide native pollinator pressure.

Assessing the importance of species and their assemblages for the biodiversity-ecosystem multifunctionality relationship.

Biodiversity changes, such as decline in species richness and biotic homogenization, can have grave consequences for ecosystem functionality. Careful investigation of biodiversity-ecosystem multifunctionality linkages with due consideration of conceptual and technical challenges is required to make the knowledge practically useful in managing social-ecological systems. In this paper, we introduced different methods to assess perspectives regarding the issue of diversity-multifunctionality, including a possible multifunctional redundancy/uniqueness, and the influences of the number and identity of functions on multifunctionality. In particular, we aimed to align methods with detecting the mechanisms underpinning diversity- multifunctional relationships that are free from statistical biases. Based on a set of novel methods that excluded analytical biases resulting from differences in the number and identities of multiple functions considered, we found that a substantial portion of species disproportionately supported ecosystem functions and that the diversity effects on multifunctionality were more markedly observed when more functions were considered. These results jointly emphasize that individual species are, to some extent, both functionally unique as well as redundant, highlighting the complexity and necessity for managed assemblages to retain high levels of diversity. We also observed that the relative magnitude of uniqueness or redundancy can differ between species and functions and therefore should be defined in a multifunctional context. We further found that only a small subset of species was identified as significantly less important, especially at low levels of multifunctionality. Taken together, given the low level of multifunctional redundancy we identified, we stress that unraveling the hierarchical roles of biodiversity at different levels, such as individual species and their assemblages, should be a high research priority, in both theory and practice. This article is protected by copyright. All rights reserved.

Cefquinome shows a higher impact on the pig gut microbiome and resistome compared to ceftiofur

Cephalosporins are licensed for treatment of severe bacterial infections in different species. However, the effect of these antimicrobials on the fecal microbiome and potential spread of resistance-associated genes causes great concern. This highlights the need to understand the impact of cephalosporins on the porcine fecal microbiome and resistome. A combination of long-read 16S rRNA gene and shotgun metagenomic sequencing was applied to investigate the effect of conventional treatment with either ceftiofur (3 mg.kg−1 intramuscular, 3 consecutive days) or cefquinome (2 mg.kg−1 intramuscular, 5 consecutive days) on the porcine microbiome and resistome. Fecal samples were collected from 17 pigs (6 ceftiofur treated, 6 cefquinome treated, 5 control pigs) at four different timepoints. Treatment with ceftiofur resulted in an increase in Proteobacteria members on microbiome level, while on resistome level selection in TetQ containing Bacteroides, CfxA6 containing Prevotella and blaTEM-1 containing Escherichia coli was observed. Cefquinome treatment resulted in a decline in overall species richness (α-diversity) and increase in Proteobacteria members. On genus level, administration of cefquinome significantly affected more genera than ceftiofur (18 vs 8). On resistome level, cefquinome resulted in a significant increase of six antimicrobial resistance genes, with no clear correlation with certain genera. For both antimicrobials, the resistome levels returned back to the control levels 21 days post-treatment. Overall, our study provides novel insights on the effect of specific cephalosporins on the porcine gut microbiome and resistome after conventional intramuscular treatment. These results might contribute to better tailoring of the most ideal treatment strategy for some bacterial infections.

Climate change drives substantial decline of understorey species richness and abundance in Norway spruce forests during 32 years of vegetation monitoring

AbstractQuestionsObservations in permanent forest vegetation plots in Norway and elsewhere indicate that complex changes have taken place over the period 1988–2020. These observations are summarised in the “climate‐induced understorey change (CIUC)” hypothesis, i.e. that the understorey vegetation of old‐growth boreal forests in Norway undergoes significant long‐term changes and that these changes are consistent with the ongoing climate change as an important driver. Seven testable predictions were derived from the CIUC hypothesis.LocationNorway.MethodsVegetation has been monitored in a total of 458 permanently marked plots, each 1 m2, in nine old‐growth forest sites dominated by Picea abies at intervals of 5–8 years over the 32‐year study period. For each of the 52 combinations of site and year, we obtained response variables for the abundance of single species, abundance and species density of taxonomic–ecological species groups and two size classes of cryptogams, and site species richness. All of these variables were subjected to linear regression modelling with site and year as predictors.ResultsMean annual temperature, growing‐season length and the number of days with precipitation were higher in the study period than in the preceding ca. 30‐year period, resulting in increasingly favourable conditions for bryophyte growth. Site species richness decreased by 13% over the 32‐year study period. On average, group abundance of vascular plants decreased by 24% (decrease in forbs: 38%). Patterns of group abundance change differed among cryptogam groups: although peat‐moss abundance increased by 39%, the abundance of mosses, hepatics and lichens decreased by 13%, 49% and 67%, respectively. Group abundance of small cryptogams decreased by 61%, whereas a 13% increase was found for large cryptogams. Of 61 single species tested for abundance change, a significant decrease was found for 43 species, whereas a significant increase was found only for 6 species.ConclusionsThe major patterns of change in species richness, group species density and group abundance observed over the 32‐year study period accord with most predictions from the CIUC hypothesis and are interpreted as direct and indirect responses to climate change, partly mediated through changes in the population dynamics of microtine rodents. The more favourable climate for bryophyte growth explains the observed increase for a few large bryophyte species, whereas the decrease observed for small mosses and hepatics is interpreted as an indirect amensalistic effect, brought about by shading and burial in mats of larger species and accelerated by reduced fine‐scale disturbance by microtine rodents. Indirect effects of a thicker moss mat most likely drive the vascular plant decline although long‐term effects of tree‐stand dynamics and former logging cannot be completely ruled out. Our results suggest that the ongoing climate change has extensive, cascading effects on boreal forest ecosystems. The importance of long time‐series of permanent vegetation plots for detecting and understanding the effects of climate change on boreal forests is emphasised.

Human appropriation of net primary production as driver of change in landscape-scale vertebrate richness.

Land use is the most pervasive driver of biodiversity loss. Predicting its impact on species richness (SR) is often based on indicators of habitat loss. However, the degradation of habitats, especially through land-use intensification, also affects species. Here, we evaluate whether an integrative metric of land-use intensity, the human appropriation of net primary production, is correlated with the decline of SR in used landscapes across the globe. Global. Present. Birds, mammals and amphibians. Based on species range maps (spatial resolution: 20 km × 20 km) and an area-of-habitat approach, we calibrated a "species-energy model" by correlating the SR of three groups of vertebrates with net primary production and biogeographical covariables in "wilderness" areas (i.e., those where available energy is assumed to be still at pristine levels). We used this model to project the difference between pristine SR and the SR corresponding to the energy remaining in used landscapes (i.e., SR loss expected owing to human energy extraction outside wilderness areas). We validated the projected species loss by comparison with the realized and impending loss reconstructed from habitat conversion and documented by national Red Lists. Species-energy models largely explained landscape-scale variation of mapped SR in wilderness areas (adjusted R 2-values: 0.79-0.93). Model-based projections of SR loss were lower, on average, than reconstructed and documented ones, but the spatial patterns were correlated significantly, with stronger correlation in mammals (Pearson's r=0.68) than in amphibians (r=0.60) and birds (r=0.57). Our results suggest that the human appropriation of net primary production is a useful indicator of heterotrophic species loss in used landscapes, hence we recommend its inclusion in models based on species-area relationships to improve predictions of land-use-driven biodiversity loss.

Taxonomic, phylogenetic and functional responses of plant communities in different life-stages to forest cover loss

Habitat loss is among one of the main causes of biodiversity decline worldwide. Therefore, assessing different dimensions of diversity such taxonomic, phylogenetic, and functional is important for more effective conservation strategies. Also, important but scarce, is the comparison of different life-stages which can bring insights due to different time delay on species responses to anthropogenic changes. Herein we assessed the influence of landscape-scale forest cover loss on different diversity dimensions of adult and juvenile tree assemblages. Our results showed that richness, phylogenetic and functional diversity were highly correlated for both life-stages. Forest cover loss leads to a decline in species richness more sharply in juveniles than adults, but in general, it did not affect phylogenetic and functional diversity. The responses among life-stages differed only for richness and phylogenetic mean pairwise distance. The negative impacts of forest cover loss on richness were not mirrored by phylogenetic and functional diversity, although there are some differences among life-stages. Our findings suggest that for practical purposes species richness is a primary and effective biodiversity measure at the landscape-scale. Furthermore, the stronger effects on juvenile assemblages indicate recruitment limitation and an impoverished future plant community, highlighting the importance to include different life-stages into conservation actions.

Changes in macrofaunal groups before, during and after the Cenomanian–Turonian biotic crisis in north Eastern Desert, Egypt

The stratigraphic distribution of the different faunal groups of the upper Cenomanian–lower Turonian deposits in the north Eastern Desert, Egypt, is investigated. Variations in species richness, faunal diversity, extinction and origination rates before, during, and after the globally known Oceanic Anoxic Event (OAE) 2 are documented. The OAE2 interval is constrained by the first occurrence of the marker ammonite species Vascoceras cauvini and the last occurrence of Vascoceras proprium, along with the positive δ13C excursions, previously identified from the Wadi El-Burga section. A prominent decline in species richness and diversity, high extinction rates, and low origination rates of the recorded macrofaunal elements are reported during the OAE2 interval. Such faunal bottleneck was attributed to the prevailing major palaeoclimatic and palaeoenvironmental perturbations during that time. Besides oceanic anoxia, changes in sea water palaeotemperature and sea level are discussed. It can be concluded that oceanic anoxia, warming, and /or transgressive episodes were the major driving mechanisms of the faunal crisis reported in the present work.

Little evidence for land-use filters on intraspecific trait variation in three arthropod groups

Abstract. Declines in species richness and abundance of insects over the last decades are often driven by anthropogenic land use and can have severe consequences for ecosystem functioning. Many studies investigated the effects of land-use intensification on the distribution of phenotypic traits across species at the community level, often with mixed results. However, biotic and abiotic environmental filters and potential selection act on individuals within each species, i.e., at the species' population level, and thus drive the extent of intraspecific phenotypic variation. Here, we compare the morphological trait variation within selected species of dung beetles, bees and grasshoppers and link this variation to land-use intensity in forests and grasslands. Selected traits included absolute body size measures and relative leg, wing or eye size, or shape and are often interpreted as “functional traits” in the context of specific ecological responses or effects. We predicted that trait variability among individuals of arthropod species is reduced in intensively used ecosystems (with pronounced environmental filtering) compared to low-intensity ones, particularly for arthropod species that were more abundant in intensively used sites (“land-use winners” compared to “losers”). In general, only few effects of land-use intensity on trait variation were found showing a decreasing variation with increasing land-use intensity in forests but an increasing variation in grasslands. Although many studies confirmed strong land-use impacts on species composition, diversity and trait distribution, including evidence from the same land-use gradients, we were not able to confirm consistent effects at the intraspecific level. However, the choice of which traits are included in analyses and the linkage between phenotypic variation and genetic variability can strongly influence the conclusions drawn on ecological processes. Therefore, we suggest extending the use of intraspecific trait variation on other, more specific response or effect traits and a broader range of species in future studies.

Monitoring the impacts of a mega-dam on Amazonian understorey herbs

Mega-dams have drastically altered the pulse of natural flooding in rivers of the Amazon, negatively affecting the biodiversity of different forest ecosystems. This study aimed to investigate the impacts of the Jirau dam on herbaceous assemblages, a relatively little studied biodiversity component. To accomplish this, we surveyed understorey herbs in 22 permanent plots (375 m2 each) between 2012 and 2019, before and after filling of the Jirau dam, and also measured a set of environmental predictors. Sampling comprised 178 morphospecies and 43,335 individuals. We found that species compositions in the pre-dam period differed in each of the sampled habitats (terra firme, transitional forest, várzea, and campinarana), and that such differences were mostly correlated with sum of bases, topography, C/N ratio, silt and pH. Environmental associations differed among three major groups of herbs (Ferns, Poales and Zingiberales). During the post-dam period, flooded plots showed high rates of mortality and recruitment close to 100 % and a sharp decline in species richness while non-flooded plots showed relative stability for these parameters. The number of flooded days and habitat type were strong predictors of mortality and recruitment rates. A combination of canopy opening driven by tree mortality and seasonal flooding after filling of the Jirau reservoir altered herb species composition in flooded plots, favouring the recruitment of Poales. Overall, herbaceous plants showed higher sensitivity to flooding caused by the Jirau dam when compared to trees sampled in the same site, reinforcing their potential as biodiversity targets for environmental assessments.

Decline in wild bee species richness associated with honey bee (Apis mellifera L.) abundance in an urban ecosystem.

The spatial heterogeneity of urban landscapes, relatively low agrochemical use, and species-rich floral communities often support a surprising diversity of wild pollinators in cities. However, the management of Western honey bees (Apis mellifera L.) in urban areas may represent a new threat to wild bee communities. Urban beekeeping is commonly perceived as an environmentally friendly practice or a way to combat pollinator declines, when high-density beekeeping operations may actually have a negative influence on native and wild bee populations through floral resource competition and pathogen transmission. On the Island of Montréal, Canada there has been a particularly large increase in beekeeping across the city. Over the years following a large bee diversity survey ending in 2013, there was an influx of almost three thousand honey bee colonies to the city. In this study, we examined the wild bee communities and floral resources across a gradient of honey bee abundances in urban greenspaces in 2020, and compared the bee communities at the same sites before and after the large influx of honey bees. Overall, we found a negative relationship between urban beekeeping, pollen availability, and wild bee species richness. We also found that honey bee abundance had the strongest negative effect on small (inter-tegular span <2.25 mm) wild bee species richness. Small bee species may be at higher risk in areas with abundant honey bee populations as their limited foraging range may reduce their access to floral resources in times of increased competition. Further research on the influence of urban beekeeping on native and wild pollinators, coupled with evidence-based beekeeping regulations, is essential to ensure cities contain sufficient resources to support wild bee diversity alongside managed honey bees.

Hummingbird diversity in a fragmented tropical landscape in the Chocó biogeographic zone

AbstractForest loss and fragmentation drive widespread declines in biodiversity. However, hummingbirds seem to exhibit relative resilience to disturbance, characterized by increasing abundance alongside declining species richness and evenness. Yet, how widespread this pattern may be, and the mechanisms by which it may occur, remain unclear. To fill in this knowledge gap, we investigated habitat‐ and site‐level patterns of diversity, and community composition of hummingbirds between continuous forest (transects n = 16 in ~3500 ha) and more disturbed surrounding fragments (n = 39, 2.5–48.0 ha) in the Chocó rain forest of northwestern Ecuador. Next, we assessed within‐patch and patch‐matrix characteristics associated with hummingbird diversity and composition. We found higher hummingbird species richness in forest fragments relative to the continuous forest, driven by increased captures of rare species in fragments. Community composition also differed between continuous forest and fragments, with depressed evenness in fragments. Increased canopy openness and density of medium‐sized trees correlated with hummingbird diversity in forest fragments, although this relationship became nonsignificant after applying false discovery rate (p &lt; .01). Higher species richness in fragments and higher evenness in the continuous forest highlight the complex trade‐offs involved in the conservation of this ecologically important group of birds in changing Neotropical landscapes.Abstract in Spanish is available with online material.