Insect Richness Research Articles

A zoning-based solution for hierarchical forest patch mosaic in urban parks

Urbanization has led to the loss, fragmentation, and degradation of habitats, as well as that of biodiversity in cities. Urban parks play a key role in conserving biodiversity. Despite the advantages of complex vegetation structures for insect and bird diversity, a simple vegetation structure is favored in urban parks worldwide. The trade-off between human recreation and biodiversity conservation is challenging. Zoning strategy may be an effective countermeasure informed by the national park and natural scenic area; a zoning-based solution was introduced in this study, including preserved core zones and surrounding recreation zones. Guangyanggu Urban Forest Park was found to be advantageous for biodiversity and in terms of the feasibility of a small hierarchical forest patch (HFP) in the center of Beijing, which can serve as a model for core zones. The park had higher species richness of plants, insects, and birds than did six control sample parks. The Gleason richness indices of insect and bird species significantly correlated with the ratio of multilayered vegetation area to total sample area (r = 0.757 and 0.867 respectively; p < 0.05). The HFP mosaic model was used to develop the core zone in the urban park. Nine scenarios were defined for the HFP mosaic pattern, quantitatively delineating the typical spatial patterns of HFPs in parks. These results will improve the design and management of the current urban park paradigm. A bio-friendly park model characterized by HFP can optimize professional designing and maintenance guidelines for future urban parks.

Early successional colonizers both facilitate and inhibit the late successional colonizers in communities of dung-inhabiting insects

The influence of early arriving species on the establishment and activity of later ones (the priority effect) is a key issue in ecological succession. Priority effects have been extensively studied in communities subject to autotrophic succession (plants, sessile animals), but only sporadically studied in communities subject to heterotrophic succession (e.g. dung or carrion inhabiting communities). We studied the influence of early successional colonizers on late successional colonizers by manipulating the successional processes in cow dung pats via delaying, and thus lowering, colonization by early successional insects. The decreased activity of early successional insects did not affect the species richness of late successional insects, but it did lead to increased abundance of colonizers. Late successional coprophagous beetles were facilitated by early successional species while larvae of late successional coprophagous flies were inhibited, presumably, by the larvae of early successional flies. We therefore propose that both facilitation and inhibition have a role to play in the heterotrophic succession of coprophilous insects. In addition, facilitation and inhibition among taxa seems to reflect their evolutionary relationships, with facilitation being prominent between phylogenetically distant lineages (early successional Diptera and late successional Coleoptera), and inhibition being more common between closely related lineages (early vs. late successional Diptera). These patterns are strikingly reminiscent of the situation in the autotrophic succession of plants.

Higher forest cover and less contrasting matrices improve carrion removal service by scavenger insects in tropical landscapes

Abstract Understanding the links between biological communities and ecosystem service provision through the mechanisms driven by landscape structure is crucial to promote management strategies that safeguard both biodiversity and provision of these services. Here, we assess the impact of landscape structure and matrix contrast on carrion removal by scavenger insects, an often overlooked ecosystem service but of paramount importance for nutrient cycling and disease control. We first hypothesize that more forested landscapes and less contrasting matrices harbour richer communities of scavenger insects, mainly composed of forest species. We then posit that these richer communities of scavenger insects promote a higher provision of the carrion removal service. The scavenger insect community and carrion removal service was surveyed using 18 independent paired sampling sites (forest‐agricultural matrix, composed either by coffee plantations or cattle pastures) in the Atlantic Brazilian Forest domain. We measured insect species richness, community composition and carrion removal amount using meat baits inside exclusion cages monitored along 6 days across a forest cover gradient (8%–89%) and distance gradient from forest edge (0–100 m to the interior of forest patches and adjacent matrix). Species richness of scavenger insects was higher in more fragmented landscapes, with more forested areas presenting communities composed of mainly forest‐associated species. Carrion in coffee plantations attracted richer communities than in cattle pastures or forests. Coffee plantations also presented communities with more forest‐associated species than cattle pastures. Carrion removal was higher in both forest and coffee plantations compared to cattle pastures. Even though forest communities had lower species richness, key forest‐associated groups were the bulk of a higher service provision. Synthesis and applications. Forested landscapes with less contrasting matrices maintain a higher provision of carrion removal service by sustaining communities composed of scavenger insects with higher carrion removal capacity—mostly forest‐associated species. Landscape management focusing on the conservation and reforestation of native forest patches, as well as reducing matrix contrast, could facilitate species spillover and thereby ensure the provision of carrion removal service.

Short‐term positive effects of wildfire on diurnal insects and pollen transport in a Mediterranean ecosystem

Climate change is a key driver of increased wildfire activity globally. Whilst the recovery of plant communities after fire is generally understood, the impacts on ecological processes, such as pollen transport by insects, have received little attention. We investigated the effects of wildfire on diurnal insects and pollen transport over 2 years following a large fire in Southern Portugal. By comparing samples collected at burned and adjacent unburned sites, we examined wildfire effects on (a) abundance and species richness of insects across seasons, (b) pollen being transported, (c) three of the most abundant species: Oxythyrea funesta, Heliothaurus ruficolis (both Coleoptera), and Apis mellifera (Hymenoptera). Wildfire and season had significant, interacting effects on the abundance of insects but not species richness. Abundance and species richness increased over time at both burned and unburned sites, most notably each spring. Pollen loads, and species richness, found on individual insects were significantly higher in burned sites in the first spring only, but generally increased with time after the wildfire. The abundance of O. funesta was similar between burned and unburned sites in the spring, but in the winter was significantly higher in burned sites; there were no significant differences in summer and autumn. H. ruficolis abundance was higher in burned sites. A. mellifera abundance was unaffected. Overall, across almost all the community metrics, our results suggest that wildfire affects pollen transport by diurnal insects, at least in the short term, but with time, these become similar to unburned habitats.

Warming of aquatic ecosystems disrupts aquatic-terrestrial linkages in the tropics.

Aquatic ecosystems are tightly linked to terrestrial ecosystems by exchanges of resources, which influence species interactions, community dynamics and functioning in both ecosystem types. However, our understanding of how this coupling responds to climate warming is restricted to temperate, boreal and arctic regions, with limited knowledge from tropical ecosystems. We investigated how warming aquatic ecosystems impact cross-ecosystem exchanges in the tropics, through the export of aquatic resources into the terrestrial environment and the breakdown of terrestrial resources within the aquatic environment. We experimentally heated 50 naturally assembled aquatic communities, contained within different-sized tank-bromeliads, to a 23.5-32°C gradient of mean water temperatures. The biomass, abundance and richness of aquatic insects emerging into the terrestrial environment all declined with rising temperatures over a 45-day experiment. Structural equation and linear mixed effects modelling suggested that these impacts were driven by deleterious effects of warming on insect development and survival, rather than being mediated by aquatic predation, nutrient availability or reduced body size. Decomposition was primarily driven by microbial activity. However, total decomposition by both microbes and macroinvertebrates increased with temperature in all but the largest ecosystems, where it decreased. Thus, warming decoupled aquatic and terrestrial ecosystems, by reducing the flux of aquatic resources to terrestrial ecosystems but variably enhancing or reducing terrestrial resource breakdown in aquatic ecosystems. In contrast with increased emergence observed in warmed temperate ecosystems, future climate change is likely to reduce connectivity between tropical terrestrial and aquatic habitats, potentially impacting consumers in both ecosystem types. As tropical ectotherms live closer to their thermal tolerance limits compared to temperate species, warming can disrupt cross-ecosystem dynamics in an interconnected tropical landscape and should be considered when investigating ecosystem-level consequences of climate change.

Divergent nucleic acid allocation in juvenile insects of different metamorphosis modes

Nucleic acids help clarify variation in species richness of insects having different metamorphosis modes, a biological conundrum. Here we analyse nucleic acid contents of 639 specimens of aquatic insects collected from four high mountain streams of Sierra Nevada in southern Spain to test whether the allocation to RNA or DNA content differs during ontogeny between juvenile insects undergoing direct (hemimetabolous) or indirect (holometabolous) metamorphosis. The results show that RNA content as a function of body mass was negatively correlated to insect body length in four out of six and three out of six of the holometabolan and hemimetabolan taxa, respectively. Although no significant differences in RNA content were found between holometabolans and hemimetabolans, the significant interaction between body length and metamorphosis mode for RNA and RNA:DNA indicates a strong ontogenetic component to RNA allocation. In addition, our finding of lower DNA content in holometabolans relative to hemimetabolans agree with the analysis of empirical genome data in aquatic and terrestrial insects, and extend to this class of arthropods the “growth rate-genome size-nutrient limitation” hypothesis that differences in allocation between RNA and DNA may reflect fundamental evolutionary trade-off of life-history strategies associated with high growth rates (and RNA content) in holometabolans at the expense of diminished genome sizes.

Landscape and Local Drivers Affecting Flying Insects along Fennel Crops (Foeniculum vulgare, Apiaceae) and Implications for Its Yield.

Simple SummaryIn a globally strained context where food production constantly challenges biodiversity, the importance of insect activity to crop pollination is at stake, as insects are essential to more than 75% of global crops. Despite this awareness, there is still a gap of knowledge about the importance of pollinators for aromatic crops. Fennel is an aromatic plant cultivated in the South of France for its essential oil, which is of great economic interest. Here, we explored the effect of the abundance and richness of insects caught at the edge of fennel crops on the yield of essential oil. We found that high insect richness improves fennel essential oil yield. In this context, it appeared important to know what structured the insect communities we trapped. By calculating indices describing the landscape, we have shown that rather than the type of habitat surrounding them, it is the arrangement of habitats that affected the abundance and richness of insects. As these results, confirmed the importance of maintaining complex landscapes to sustain both flower-visiting insect populations and crop yield, they will be of interest to fennel producers.Agricultural landscapes are increasingly characterized by intensification and habitat losses. Landscape composition and configuration are known to mediate insect abundance and richness. In the context of global insect decline, and despite 75% of crops being dependent on insects, there is still a gap of knowledge about the link between pollinators and aromatic crops. Fennel (Foeniculum vulgare) is an aromatic plant cultivated in the South of France for its essential oil, which is of great economic interest. Using pan-traps, we investigated the influence of the surrounding habitats at landscape scale (semi-natural habitat proportion and vicinity, landscape configuration) and local scale agricultural practices (insecticides and patch size) on fennel-flower-visitor abundance and richness, and their subsequent impact on fennel essential oil yield. We found that fennel may to be a generalist plant species. We did not find any effect of intense local management practices on insect abundance and richness. Landscape configuration and proximity to semi-natural habitat were the main drivers of flying insect family richness. This richness positively influenced fennel essential oil yield. Maintaining a complex configuration of patches at the landscape scale is important to sustain insect diversity and crop yield.

Bloom evenness modulates the influence of bloom abundance on insect community structure in suburban gardens.

As land use change drives global insect declines, the value of enhancing habitat in urban and suburban landscapes has become increasingly important for flower-visiting insects. In order to help identify best landscaping practices, we conducted plant surveys and insect bowl-trap surveys in 34 suburban yards for 21 months in Gainesville, FL, USA, which resulted in 274 paired days of plant and insect survey data. We assessed the impact of nearest greenspace size, distance to greenspace, yard area, plant richness, plant type, bloom abundance, bloom richness and bloom evenness on insect abundance and richness. Our samples include 34,972 insects captured, 485,827 blooms counted and 774 species of plants recorded. We found that bloom evenness had a modulating effect on bloom abundance—a more even sample of the same number of blooms would have a disproportionately greater positive impact on flower visitor richness, insect richness and insect abundance. Bloom abundance was also highly significant and positively associated with flower visitor abundance, but nearest greenspace size, distance to greenspace, plant type (native vs. non-native vs. Florida Friendly), and yard area were not found to be important factors. Plant richness was a highly significant factor, but its effect size was very small.

Higher Elevations Tend to Have Higher Proportion of Plant Species With Glandular Trichomes.

Glandular trichomes are well known to participate in plant chemical and physical defenses against herbivores, especially herbivorous insects. However, little is known about large-scale geographical patterns in glandular trichome occurrence. Herbivory pressure is thought to be higher at low elevations because of warmer and more stable climates. We therefore predicted a higher proportion of species with glandular trichomes at low elevations than at higher elevations. We compiled glandular trichome data (presence/absence) for 6,262 angiosperm species from the Hengduan Mountains (a global biodiversity hotspot in southwest China). We tested the elevational gradient (800–5,000 m a.s.l.) in the occurrence of plant species with glandular trichomes, and its correlations with biotic (occurrence of herbivorous insects) and abiotic factors, potentially shaping the elevational gradient in the occurrence of glandular trichomes. We found a significantly positive relationship between elevation and the occurrence of glandular trichomes, with the proportion of species having glandular trichomes increasing from 11.89% at 800 m a.s.l. to 17.92% at above 4,700 m. This cross-species relationship remained significant after accounting for phylogenetic relationships between species. Herbivorous insect richness peaked at mid-elevations and its association with the incidence of glandular trichomes was weak. Mean annual temperature was the most important factor associated negatively with glandular trichomes. Our results do not support the hypothesis that plant defenses decrease with increasing elevation. In contrast, a higher proportion of plant species with glandular trichome toward higher elevations is observed. Our results also highlight the importance of considering the simultaneous influences of biotic and abiotic factors in testing geographical variation in multifunctional plant defenses.

Indigenous plants promote insect biodiversity in urban greenspaces.

The contribution of urban greenspaces to support biodiversity and provide benefits for people is increasingly recognized. However, ongoing management practices favor vegetation oversimplification, often limiting greenspaces to lawns and tree canopy rather than multi-layered vegetation that includes under- and midstorey, and the use of nonnative species. These practices hinder the potential of greenspaces to sustain indigenous biodiversity, particularly for taxa like insects that rely on plants for food and habitat. Yet, little is known about which plant species may maximize positive outcomes for taxonomically and functionally diverse insect communities in greenspaces. Additionally, while cities are expected to experience high rates of introductions, quantitative assessments of the relative occupancy of indigenous vs. introduced insect species in greenspace are rare, hindering understanding of how management may promote indigenous biodiversity while limiting the establishment of introduced insects. Using a hierarchically replicated study design across 15 public parks, we recorded occurrence data from 552 insect species on 133 plant species, differing in planting design element (lawn, midstorey, and tree canopy), midstorey growth form (forbs, lilioids, graminoids, and shrubs) and origin (nonnative, native, and indigenous), to assess (1) the relative contributions of indigenous and introduced insect species and (2) which plant species sustained the highest number of indigenous insects. We found that the insect community was overwhelmingly composed of indigenous rather than introduced species. Our findings further highlight the core role of multi-layered vegetation in sustaining high insect biodiversity in urban areas, with indigenous midstorey and canopy representing key elements to maintain rich and functionally diverse indigenous insect communities. Intriguingly, graminoids supported the highest indigenous insect richness across all studied growth forms by plant origin groups. Our work highlights the opportunity presented by indigenous understory and midstorey plants, particularly indigenous graminoids, in our study area to promote indigenous insect biodiversity in urban greenspaces. Our study provides a blueprint and stimulus for architects, engineers, developers, designers, and planners to incorporate into their practice plant species palettes that foster a larger presence of indigenous over regionally native or nonnative plant species, while incorporating a broader mixture of midstorey growth forms.

Aquatic Insects as Bio-Indicators of Water Quality – A Study on Sungai Kawal, Johor National Park of Endau-Rompin, Peninsular Malaysia

Biological indicator species or bio-indicators are sensitive to specific environmental factors so that changes in their environment will be reflected by their incidence or abundance. In fact, aquatic insects of freshwater river and stream ecosystems have been widely used as bio-indicators to examine the species-habitat relationship with regard to the water quality of the habitat. Therefore, this study attempted to determine species richness of aquatic insects in Sungai Kawal, Johor National Park of Endau-Rompin (TNJER), Mersing, Johor, Malaysia; to identify traditional knowledge (TK) used by Jakun tribe in Kampung Peta, TNJER for maintaining rivers and streams at good level; and then to correlate the relationship between the scientific perspective and TK perspective. Aquatic insects were collected and sampled by using kick sampling technique and D-framed net. Throughout the study, a total of 618 individuals consisting of 23 families belonging to seven orders of aquatic insects were reported. The documentation of TK was done by interviewing 10 total respondents of the Jakun tribe in Kampung Peta. Physical features of Sungai Kawal were also recorded during sampling. The correlation between the scientific perspective and TK perspective regarding how the ecosystem maintenance by the Jakun tribe has contributed to an excellent habitat for the aquatic insects to breed and multiply. The number of species recorded indicated the good status of water quality of Sungai Kawal based on science and then supported by TK of the Jakun tribe of Kampung Peta. Furthermore, the findings also suggested a good correlation between the scientific perspective and TK perspective, and the significant contribution of TK of the Jakun tribe to the management of natural resources.

Caddisflies (Trichoptera, Insecta)as Bioindicator of Water Quality Assessment in a Small Stream in Northern Thailand

The influence of environmental variables and the potential as bioindicators of larval stages of the species of Trichoptera were evaluated in a small stream in northern Thailand from January to November 2017. A total of 1,191 individual caddisfly larvae belonging to 7 families and 13 genus were found. The larvae of the family Glossosomatidae were the most abundant, followed by Hydropsychidae and Calamoceratidae. The genus Glossosoma, Hydromanicusand Hydropsyche were the most abundant genus in this study. Results of the CCA ordination showed that total dissolved solids, electrical conductivity, and water temperature were the most important factors affecting the abundance and diversity of caddisfly larvae. Changes in the caddisfly larvae may indicate changes in physicochemical factors owing to urbanization or other anthropogenic. The results showed that the order Trichoptera, identified to the species or genus level, can potentially be used to assess environmental water quality status in freshwater ecosystems. This study suggested that species richness of aquatic insects may indicate the conservation value of the habitats because of their significant responses to environmental factors.

Biodiversity baselines: Tracking insects in Kruger National Park with DNA barcodes

Reflecting their species richness and ecological diversification, insects play a central role in terrestrial ecosystems but difficulties in species-level assignments have restricted large-scale analysis of their community structure. Employing South Africa's largest national park as a model system, we demonstrate that DNA barcoding can break this barrier. A year-long deployment of Malaise traps at 25 sites in Kruger National Park (KNP) generated 1000+ weekly collections containing about 800,000 specimens. Insect biomass averaged 1.05 g per trap-day but varied by up to 2-fold between months, being lower in the dry than wet season. Nearly 370,000 specimens were individually analyzed to reveal 19,730 Barcode Index Numbers (BINs; species proxy), a count equal to 43% of the known insect fauna of southern Africa. There was clear differentiation in insect richness and composition between KNP's two ecoregions, but little among the vegetation types comprising them. The spatial gradient in annual rainfall explained more than half of the variation in compositional similarity among sites with less similarity among samples in the wet season, particularly among those in high rainfall areas. These results suggest that the factors organising insect communities in KNP are not fine-scale vegetation differences, but larger-scale processes associated with ecoregions and rainfall. Estimates of sample coverage indicate that the species not collected are rare, comprising only 4% of the individuals in the community. With a well-parameterized DNA barcode reference library in place, metabarcoding can be used to assess future shifts in the insect fauna of KNP rapidly and inexpensively.

Variation in Insect Richness on Six Prairie Plant Species

Insects play a fundamental role in ecosystem stability by providing important ecological services such as pollination, biological pest control, and nutrition for other organisms. Recent human-caused declines in insect populations mandate that we better understand how to improve and sustain insect diversity and abundance. The goal of our study was to identify the insects associated with 6 prairie plant species. We spent 248 hours over 3 months during 1 year monitoring insect visits to 10 replicates of ∼1-m2 patches each of Verbena brasiliensis (Brazilian Vervain, Verbenaceae), Pycnanthemum muticum (Blunt Mountainmint, Lamiaceae), Monarda fistulosa (Wild Bergamot, Lamiaceae), Eryngium yuccifolium (Rattlesnake Master, Apiaceae), Silphium gracile (Slender Rosinweed, Asteraceae), and Rudbeckia texana (Texas Coneflower, Asteraceae). We identified 11 bee species and 100 non-bee species representing 9 orders and 57 families. Insect richness varied widely among plant species: More taxa (n = 75) visited Blunt Mountainmint than any other plant species. Wild Bergamot had the fewest visiting taxa (n = 23). The majority of insects visited multiple plants, although we observed 2 bee species and 44 non-bee species on only 1 plant species. The number of unique insect visitors of each plant species varied from 1 to 19 taxa. Total insect richness was significantly greater in the morning than afternoon (χ2 = 3.7, P = 0.054). That plant diversity begets insect diversity is widely accepted, and our work suggests that inclusion of plants that are strong insect attractors could be integral to insect conservation and restoration initiatives.

Detecting flying insects using car nets and DNA metabarcoding.

Monitoring insects across space and time is challenging, due to their vast taxonomic and functional diversity. This study demonstrates how nets mounted on rooftops of cars (car nets) and DNA metabarcoding can be applied to sample flying insect richness and diversity across large spatial scales within a limited time period. During June 2018, 365 car net samples were collected by 151 volunteers during two daily time intervals on 218 routes in Denmark. Insect bulk samples were processed with a DNA metabarcoding protocol to estimate taxonomic composition, and the results were compared to known flying insect richness and occurrence data. Insect and hoverfly richness and diversity were assessed across biogeographic regions and dominant land cover types. We detected 15 out of 19 flying insect orders present in Denmark, with high proportions of especially Diptera compared to Danish estimates, and lower insect richness and diversity in urbanized areas. We detected 319 species not known for Denmark and 174 species assessed in the Danish Red List. Our results indicate that the methodology can assess the flying insect fauna at large spatial scales to a wide extent, but may be, like other methods, biased towards certain insect orders.

Geographical, temporal and taxonomic biases in insect GBIF data on biodiversity and extinction

1. Analysis of geographic patterns of extinction must be accompanied by knowledge of biodiversity patterns. Such analysis is not yet available in insects given three shortfalls. First, knowledge of insect species' distribution is poor. Second, insect inventories have taxonomic, geographical, temporal and habitat biases. Third, the accelerated loss of insect species likely surpasses the rate at which the authors are discovering new species.2. The authors have examined the state of the art of knowledge of the geographical distribution of insect extinction risk and diversity, as well as their relation with human footprint.3. Insect records are highly scattered. Geographically, inventories are incomplete worldwide, except for some areas in Europe. Although the description of new insect species has increased in the last 40 years, this is biased towards lepidopterans and coleopterans. Comparably, IUCN‐listed species has also increased in the last 40 years, yet with biases towards odonates and lepidopterans. Likewise, aquatic species have been more intensively sampled and considered by the IUCN than terrestrial species. Of high priority are some pristine areas but with few insect records, whereas the east coast of the United States, Europe and Japan raise concerns given that the human footprint exceeded the species richness of insects registered.

Plant diversity drives responses of gall-inducing insects to anthropization in Neotropical savannas

Human-induced habitat modification is among the main factors that threaten biodiversity on the planet. For highly specialized herbivorous insects, such as galling insects, anthropogenic disturbances that affect plants can have great effects on insects. In this sense, in the present study, we investigated the diversity of host plants and gall-inducing insects in anthropized and preserved remnants of Neotropical savannas in the Brazilian Cerrado. Sampling was performed in 30 plots (10 × 10 m) distributed in six study areas. Of these total, fifteen plots were in areas with anthropized vegetation and fifteen plots in areas with preserved vegetation. Overall, we recorded 67 species of gall-inducing insects and 39 species of host plants. We found that the diversity of both host plant species and gall-inducing insects differed significantly between areas, being higher in preserved plots than in anthropized plots. Our results revelated that changes in the species richness and composition of gall-inducing insects from preserved environments to anthropized environments were mediated by changes in the richness and composition of the plant species, respectively. Our study stands out as the first to demonstrate that plant diversity drives responses of gall-inducing insects to human disturbance in Neotropical savannas. Our findings indicate that the preservation of natural vegetation is important for the conservation of plant assemblages and their gall-inducing insects in urban environments.

Insect diversity across an afro-tropical forest biodiversity hotspot

Tropical forests host a remarkable proportion of global arthropod diversity. Yet, arthropod communities living in tropical forests are still poorly studied, particularly for dry forests of Eastern Africa. The aim of this study was to analyse community structures, species richness and relative abundances of insects across a heterogeneous forest consisting of various forest types. We collected insects in the lower canopies with light traps across the Arabuko Sokoke forest, part of the East African coastal forest biodiversity hotspot in southeast Kenya. Sampling was conducted across three forest types and along the forest edge. In total we collected > 250,000 individuals. We grouped these individuals into orders, and beetles into (sub)families. Representatives of the taxonomically well-known beetle families Cerambycidae, Tenebrionidae and Scolytinae were further determined to species level. We subsequently classified these groups into guilds according to their ecological requirements and life-histories. Relative abundances of arthropods strongly differed among taxonomic groups and forest types. Evenness was highest in the heterogeneous natural Brachystegia forest type. The mixed forest type and the forest edges showed intermediate degrees of evenness, while the structurally homogenous Cynometra forest showed comparatively low degrees of evenness.Implications for insect conservationWe found that taxonomic and guild compositions strongly differed among the forest types. Our findings reveal that structural heterogeneity of a forest is the major driver of insect diversity, community composition, and relative abundance. Our study underlines that the preservation of all three forest types is crucial to maintain the complete diversity of arthropods across all taxonomic groups.

Biodiversity response to forest management intensity, carbon stocks and net primary production in temperate montane forests

Managed forests are a key component of strategies aimed at tackling the climate and biodiversity crises. Tapping this potential requires a better understanding of the complex, simultaneous effects of forest management on biodiversity, carbon stocks and productivity. Here, we used data of 135 one-hectare plots from southwestern Germany to disentangle the relative influence of gradients of management intensity, carbon stocks and forest productivity on different components of forest biodiversity (birds, bats, insects, plants) and tree-related microhabitats. We tested whether the composition of taxonomic groups varies gradually or abruptly along these gradients. The richness of taxonomic groups was rather insensitive to management intensity, carbon stocks and forest productivity. Despite the low explanatory power of the main predictor variables, forest management had the greatest relative influence on richness of insects and tree-related microhabitats, while carbon stocks influenced richness of bats, birds, vascular plants and pooled taxa. Species composition changed relatively abruptly along the management intensity gradient, while changes along carbon and productivity gradients were more gradual. We conclude that moderate increases in forest management intensity and carbon stocks, within the range of variation observed in our study system, might be compatible with biodiversity and climate mitigation objectives in managed forests.

Powerline right-of-way management and flower-visiting insects: How vegetation management can promote pollinator diversity.

Loss in the availability of early successional habitat is a threat to pollinator populations. Given that powerline rights-of-way (ROW) must be managed to maintain early successional habitat, preventing vegetation from interfering with electrical lines, they have the potential to provide conservation benefits for wild pollinators. Moreover, it is possible to provide conservation benefits with no additional cost to land managers. We surveyed flower-visiting insects over two years in different vegetation management treatments in a long-term research ROW to determine which best promoted pollinator abundance and species richness. We found that the ROW had stabilized in an early successional state soon after its establishment and that this early successional state could be maintained with low levels of periodic maintenance. We collected a high diversity of flower-visiting insects (126 bee species and 179 non-bee morphospecies) in six ROW plots. Higher levels of herbicide application had a negative effect on bee species richness, but low levels of herbicide application were compatible with a high abundance and species richness of flower-visiting insects, including several rare species. Moreover, this effect was seen only in the bee community, and not in non-bee flower-visiting insects. Our results suggest further research into the conservation value of ROW for pollinators is warranted. We demonstrate that there is substantial potential for pollinator conservation in ROW, compatible with low-cost vegetation management.