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USGS2019

Comparing grasshopper (Orthoptera: Acrididae) communities on tallgrass prairie reconstructions and remnants in Missouri

Tallgrass prairies, which once occupied a large swath of central North America, face the combined challenges of habitat loss and fragmentation. In Missouri, where less than 1% the historical prairie remains, prairies are being reconstructed from agricultural or wooded land. Invertebrates are often assumed to colonise reconstructions if native vegetation returns; however, the limited mobility of many invertebrates, the isolation of many tallgrass remnants, and the difficulty in establishing prairie plants raise serious questions as to whether invertebrate communities on reconstructed prairies are and will be equivalent to those found on remnant prairies. Grasshoppers (Acrididae) display a range of dispersal capabilities and may be valuable for assessing the success of prairie restoration for invertebrates. Our first objective was to compare grasshopper communities on reconstructed and remnant prairies and, if differences existed, identify species or functional groups associated with each habitat type. The second objective was to evaluate the effect of time because prairie reconstruction on grasshopper communities to determine if communities on reconstructions are converging with communities on remnants. Our results suggest that prairie reconstructions in Missouri do not support the same communities of grasshoppers as prairie remnants. Grasshopper diversity was generally greater on remnants. Many species had not colonised nearby reconstructions. Communities on prairie reconstructions were characterised by a few long-winged, generalist species that are typically successful in agroecosystems. Further investigation into the habitat disparities driving low grasshopper diversity on reconstructions could help restore the grasshopper community of reconstructions.

Insect Conservation and Diversity↗

USGS2012

Aquatic insect assemblages associated with subalpine stream segment types in relict glaciated headwaters

1. Aquatic habitats and biotic assemblages in subalpine headwaters are sensitive to climate and human impacts. Understanding biotic responses to such perturbations and the contribution of high-elevation headwaters to riverine biodiversity requires the assessment of assemblage composition among habitat types. We compared aquatic insect assemblages among headwater stream segment types in relict glaciated subalpine basins in Mt. Rainier National Park, Washington, USA. 2. Aquatic insects were collected during summer and autumn in three headwater basins. In each basin, three different stream segment types were sampled: colluvial groundwater sources, alluvial lake inlets, and cascade-bedrock lake outlets. Ward's hierarchical cluster analysis revealed high β diversity in aquatic insect assemblages, and non-metric multidimensional scaling indicated that spatial and temporal patterns in assemblage composition differed among headwater stream segment types. Aquatic insect assemblages showed more fidelity to stream segment types than to individual basins, and the principal environmental variables associated with assemblage structure were temperature and substrate. 3. Indicator species analyses identified specific aquatic insects associated with each stream segment type. Several rare and potentially endemic aquatic insect taxa were present, including the recently described species, Lednia borealis (Baumann and Kondratieff). 4. Our results indicate that aquatic insect assemblages in relict glaciated subalpine headwaters were strongly differentiated among stream segment types. These results illustrate the contribution of headwaters to riverine biodiversity and emphasise the importance of these habitats for monitoring biotic responses to climate change. Monitoring biotic assemblages in high-elevation headwaters is needed to prevent the potential loss of unique and sensitive biota.

Washington↗

USGS2018

Insect communities in big sagebrush habitat are altered by wildfire and post‐fire restoration seeding

Natural resource managers sow grass, forb, and shrub seeds across millions of hectares of public lands in the western United States to restore sagebrush‐steppe ecosystems burned by wildfire. The effects of post‐fire vegetation treatments on insect communities in these ecosystems have not been investigated. We conducted the first investigation of insect community responses to post‐fire seeding on public rangelands by comparing the composition of insect communities at burned‐and‐seeded (treatment) and burned‐and‐unseeded (control) sagebrush‐steppe ecological sites in southwestern Idaho. Insect communities in burned areas were compared to unburned (reference) areas. Insect communities in burned plots did not resemble those in reference plots. Treatment plots had greater inter‐annual variability in insect community composition than control or reference plots, suggesting that communities may be less stable in seeded areas. The vegetation composition of the landscape surrounding plots influenced mobile species. Wildfire and post‐fire seeding may have lasting effects on insect communities in sagebrush‐steppe ecosystems. Wildfires decrease shrub cover. Post‐fire seeding increases perennial bunchgrasses and, where successful, reduces non‐native annual grasses. These habitat changes influence insect community composition. Future studies are needed to expand the inference of this study.

Insect Conservation and Diversity↗

USGS2022

Comparison of microscopy and metabarcoding to identify pollen used by the critically endangered rusty patched bumble bee, Bombus affinis

Taxonomic analysis of pollen collected by bees can provide insights into their host plant use, providing information about the plant species selected for targeted conservation strategies. The two main identification approaches used are morphological analysis of pollen samples affixed to microscope slides (i.e., microscopic palynology) and molecular analysis of samples. Both methods are widely used for freshly collected materials and have been compared in multiple studies, yet their application to archived samples remains to be explored. Archived samples may be particularly useful for the study of rare or protected species, particularly when historical foraging patterns are uncertain. We used both methods to analyse pollen collected by the endangered rusty patched bumble bee species, Bombus affinis Cresson, applied to museum-archived specimens. Pollen samples were removed from the corbiculae of bumble bees originally collected in Michigan between 1914 and 1974. Samples included 24 rusty patched bumble bees each with large pollen loads on both corbiculae, allowing for pollen from the same bee to be analysed using both methods. DNA metabarcoding detected more plant taxa than light microscopy, and DNA barcoding also had higher taxonomic resolution when compared to taxa determined using light microscopy. In many instances, pollen could only be confidently identified to tribe or family with light microscopy. Discrepancy between methods decreased when taxa identified via DNA metabarcoding were binned into ecologically relevant groups corresponding to those identified using light microscopy. Although binning demonstrated smaller within-method variance, there was still minimal correspondence between the two methods. Results indicate there are benefits and biases unique to each method and highlight the utility of binning taxonomic results to morphological or ecological groupings.

Insect Conservation and Diversity↗

USGS2023

A comparison of summer, fall and winter estimates of monarch population size before and after milkweed eradication from crop fields in North America

Measures of the area occupied by overwintering monarchs in México since the mid-1990s show a decline. Summer surveys of monarchs, however, do not show a similar decline. This discrepancy has led to the proposition that summer monarch numbers are actually stable and that increasing mortality during migration has led to declining overwintering numbers. A competing hypothesis is that this discrepancy is due to a sampling bias in the summer counts and that the summer population has declined because of the eradication of milkweed habitat from crop fields that occurred in the late 1990s through mid-2000s. We posit that the sampling bias occurred during the period when milkweeds were declining in crop fields and resulted from not sampling in the crop fields. We examined three measures of the size of the population made in the fall during migration and four summer survey measures and compared them to the overwintering measures. Counts of migrating monarchs are not expected to have this sampling bias since migrants come from all habitats, including crop fields. During the period of milkweed eradication, counts of the migrating population were correlated with the size of the overwintering population, whereas summer survey counts were not. After milkweed eradication from crop fields, all population measures were correlated with one another. These results indicate that during the pre-eradication period, summer counts were not an accurate measure of summer population size. Population trends observed at the overwintering site reflect factors, principally milkweed loss, that affect summer population size.

Insect Conservation and Diversity↗

USGS2025

Answering key bumble bee conservation questions by studying discovered wild nests: A Bombus affinis case study

The nesting ecology of wild bumble bees is not well resolved, but information learned from discovered nests can be of great conservation value. Data collected at nests on foraging patterns, caste-specific behaviour and health (e.g., pathogens) are invaluable for understanding bumble bee behaviour and ecology, but difficult to decipher solely from foraging observations away from the nest. Post-senescence nest excavation allows the estimation of colony size, caste numbers, documents pest incidence and provides opportunities to examine nest material for stressors (e.g., pesticides) and to use nest material for training purposes (e.g., conservation dogs). Wild nests are often found opportunistically, and there is an absence of standardised guidance on data collection. We provide an action plan to ensure the data collection is comparable across studies. This framework includes key conservation questions and methodological guidelines for both for in situ and post-season nest data collection and is ordered by increasing complexity of data collection methods. To illustrate our framework, we provide an example with recently discovered Bombus affinis (rusty patched bumble bee) nests. Through observations at B. affinis nests, we discovered novel patterns of activity, changing activity levels over time, the timing of male and gyne production, variable timing in nest senescence, and associations of nests with past rodent activity. Although individual nest discoveries may be of limited value in forwarding conservation strategies, the aggregate collections of many similar datasets can be of critical importance for species of conservation concern.

Insect Conservation and Diversity↗

USGS2010

Spatial patterns of bee captures in North American bowl trapping surveys

1. Bowl and pan traps are now commonly used to capture bees (Hymenoptera: Apiformes) for research and surveys. 2. Studies of how arrangement and spacing of bowl traps affect captures of bees are needed to increase the efficiency of this capture technique. 3. We present results from seven studies of bowl traps placed in trapping webs, grids, and transects in four North American ecoregions (Mid-Atlantic, Coastal California, Chihuahuan Desert, and Columbia Plateau). 4. Over 6000 specimens from 31 bee genera were captured and analysed across the studies. 5. Based on the results from trapping webs and distance tests, the per bowl capture rate of bees does not plateau until bowls are spaced 3–5 m apart. 6. Minor clumping of bee captures within transects was detected, with 26 of 56 transects having index of dispersion values that conform to a clumped distribution and 39 transects having positive Green's index values, 13 with zero, and only four negative. However, degree of clumping was slight with an average value of only 0.06 (the index ranges from -1 to 1) with only five values >0.15. Similarly, runs tests were significant for only 5.9% of the transects. 7. Results indicate that (i) capture rates are unaffected by short distances between bowls within transects and (ii) that bowls and transects should be dispersed throughout a study site.

Insect Conservation and Diversity↗

USGS2026

Advancing ecosystem recovery with diverse species plantings in tropical forest restoration

Tropical forest restoration has increased in the past decades, with possible advancements given the UN declaration of the “Decade of Ecosystem Restoration”. However, robust assessments to compare ecosystem functions among restored forest stages are essential. We evaluated 13 actively restored forest stands ranging from 3 to 21 years of age and compared measures of forest biodiversity, structure, and ecosystem function to four 70+ year old “reference” stands that serve as restoration “targets” in the study region of the Premontane wet forest of Costa Rica. The restored stands were planted with an average of 13 tree species on abandoned pastures that were fallow for at least two years. Sixteen tree-stand attributes and six ecosystem function estimates were assessed, including: annual biomass (C) accumulation, N-fixation potential, threatened species conservation, and the provision of avian frugivore forage, insect habitat, and insect pollination. Using Principal Component Analysis, linear modeling, and Mahalanobis distance analyses, we learned that planting a diversity of tree species sets the stage for forest recovery at early restoration ages, with an inflection point at 15 years towards older reference forest characteristics and functions. Given that all restoration ages provided tree diversity and some level of ecosystem functions, the value of all restored stands in the landscape is notable. The assessment methods are easily employed, thereby providing an accessible tool to restoration practitioners.

Monteverde↗

USGS2025

Scalable environmental DNA methods reveal strong associations between landscape-scale forest habitat and insect richness

While aquatic environmental DNA (eDNA) methods have reached relative maturity, terrestrial eDNA methods are nascent and have yet to reach widespread use. Field-ready applications require eDNA survey methods where samples are easy to collect by inexperienced practitioners, easy to transport between the field and lab, and easy to process thereafter. Here, we demonstrate methods that satisfy these requirements and show strong potential for characterizing diverse terrestrial eDNA samples collected from flower and leaf surfaces. We used novel methods to collect and process 236 flower eDNA samples and 21 leaf surface eDNA samples, obtaining 2,228 Arthropoda eDNA detections spanning 175 families using amplicon sequencing of two genetic markers. Detected taxa were diverse and included numerous groups of conservation concern, such as bees (Hymenoptera; Anthophila, 32 genera spanning 5 families) and Lepidoptera (209 genera from 21 families). Data reveal strong associations between insect community richness and remotely sensed measures of forest habitat, providing a quantitative perspective of relevance to insect conservation. It is increasingly clear that a variety of organisms readily disperse eDNA throughout the environment, supporting the notion that eDNA will be a powerful tool for characterizing species distributions and monitoring at-risk species. However, we conclude that researchers seeking to characterize fine-scale habitat associations or plant-pollinator interactions using eDNA will need to carefully design studies with appropriate field controls, such as the leaf surface eDNA samples collected here.

BioRxiv↗

USGS2019

Framework for monitoring shrubland community integrity in California Mediterranean type ecosystems: Information for policy makers and land managers

Shrublands in Mediterranean‐type ecosystems worldwide support important ecosystem services including high levels of biodiversity and are threatened by multiple factors in heavily used landscapes. Use, conservation, and management of these landscapes involve diverse stakeholders, making decision processes complex. To be effective, management and land use decisions should be informed by current information on ecosystem quality and resilience. However, obtaining this information is often a challenge due to the extent of landscapes involved. Here we present a conceptual integrity monitoring framework based on simple easily observable ecosystem components readily understood by nonspecialists. Community integrity is defined by plant functional group based on relative proportion of shrubs and nonnative annual grasses. The ability to use these straightforward metrics results from four factors: relatively good alignment of characteristic bird, mammal, and insect communities with shrub cover, positive feedback between annual grasses and short fire intervals, the inhibitory effect of annual grasses on shrub seedling establishment, and similar functional group response to different disturbances. Two additional metrics, indicator species and shrub species diversity, capture subtle yet persistent signatures of disturbance on integrity not reflected in functional group composition. The framework is designed to: categorize habitats into ecosystem integrity classes, forecast likely integrity class changes caused by threats and environmental conditions, and provide a simple reporting mechanism that can be overlain with data on conservation status and vulnerabilities. The proposed framework includes a pilot phase to validate empirical relationships, thresholds, and sampling efficiency. The accessibility of these metrics to nonspecialists is anticipated to enhance communication among stakeholders and thus facilitate problem solving. Leveraging monitoring and mapping programs driven by other needs (e.g., species conservation and fire management) affords meaningful opportunities to offset program costs.

California↗

USGS2022

Hawaiian forest bird conservation strategies for minimizing the risk of extinction: biological and biocultural considerations

The iconic forest birds of Hawai‘i are facing a conservation crisis. Across the Hawaiian Islands, native forest birds have been experiencing population declines that have accelerated in the last one to two decades. While habitat loss, invasive species, and non-native predators have negatively affected forest bird species for hundreds of years, and continue to do so, introduced diseases, particularly avian malaria, are the greatest threat to forest birds today. Further, climate change has increased temperatures in the high-elevation forests, facilitating the spread of disease into areas that were once largely disease-free. Rapid population declines have now (2022) pushed four Hawaiian honeycreeper species to the brink of extinction: the endangered ‘akikiki ( Oreomystis bairdi ) and ‘akeke‘e ( Loxops caeruleirostris ) on Kaua‘i Island, and kiwikiu ( Pseudonestor xanthophrys ) and ‘ākohekohe ( Palmeria dolei ) on Maui Island. The biologists that study these birds strongly agree that without a rapid conservation response to the threat of increasing disease mortality there is a high probability these species will go extinct in the coming decade. To help evaluate alternative conservation strategies for minimizing the risk of extinction, we convened diverse groups of experts with broad experience in Hawai‘i forest birds and ecosystems, as well as the management approaches being considered, to assess the probability of success of alternative management actions. In addition to assessing this crisis from a biological perspective, we convened a group of Native Hawaiian participants that have a strong connection to the forest birds, forests, and the integration of their culture in natural and biocultural resource management. They give voice to the significance of forest birds to Native Hawaiians and provide their perspectives on alternative management actions. Broadly, the three alternative management actions being considered to prevent the extinction of forest birds from the increasing threat of disease are (1) landscape-level mosquito control through the Wolbachia incompatible insect technique, (2) captive care, and (3) conservation translocations. The two key components of the problem of preventing extinction in these four bird species is time and risk. For each species, very few individuals remain, and they are all in danger of imminent extinction. Each management action takes time to implement, which might exceed the actual time to extinction. Additionally, each of these conservation actions has potential benefits and inherent risks, as well as substantial uncertainty in terms of being successful. Native Hawaiian perspectives and considerations also vary across the conservation actions. The expert evaluations summarized in this report provide a broad assessment of conservation strategies that could be undertaken to prevent the extinction of ‘akikiki, ‘akeke‘e, kiwikiu, and ‘ākohekohe. While this report does not recommend specific actions, the information is intended to support decision-makers as they assess which, if any, conservation strategies to pursue.

Hawaii↗

USGS1994

Conservation of invertebrates in US National Parks

Entomologists who enter national parks often are surprised by the diversity of life and geography found in these remarkable natural areas. There are ichneumon wasps, carabid beetles, leps…and, of course, there are trees and mountains. In contrast, an average person entering the same parks will see the magnificent mountains and rivers, the endless forests and meadows, and the abundant wildlife. The experience would be pure joy if it were not for pesky mosquitoes. This difference in perspective explains why insects, and invertebrates in general, have traditionally been a low priority in the National Park Service (NPS). Typically, invertebrates are ignored until they cause problems.

American Entomologist↗

USGS2013

Population genetic structure of rare and endangered plants using molecular markers

This study was initiated to assess the levels of genetic diversity and differentiation in the remaining populations of Phyllostegia stachyoides and Melicope zahlbruckneri in Hawai`i Volcanoes National Park and determine the extent of gene flow to identify genetically distinct individuals or groups for conservation purposes. Thirty-six Amplified Fragment Length Polymorphic (AFLP) primer combinations generated a total of 3,242 polymorphic deoxyribonucleic acid (DNA) fragments in the P. stachyoides population with a percentage of polymorphic bands (PPB) ranging from 39.3 to 65.7% and 2,780 for the M. zahlbruckneri population with a PPB of 18.8 to 64.6%. Population differentiation (Fst) of AFLP loci between subpopulations of P. stachyoides was low (0.043) across populations. Analysis of molecular variance of P. stachyoides showed that 4% of the observed genetic differentiation occurred between populations in different k ī puka and 96% when individuals were pooled from all k ī puka. Moderate genetic diversity was detected within the M. zahlbruckneri population. Bayesian and multivariate analyses both classified the P. stachyoides and M. zahlbruckneri populations into genetic groups with considerable sub-structuring detected in the P. stachyoides population. The proportion of genetic differentiation among populations explained by geographical distance was estimated by Mantel tests. No spatial correlation was found between genetic and geographic distances in both populations. Finally, a moderate but significant gene flow that could be attributed to insect or bird-mediated dispersal of pollen across the different k ī puka was observed. The results of this study highlight the utility of a multi-allelic DNA-based marker in screening a large number of polymorphic loci in small and closely related endangered populations and revealed the presence of genetically unique groups of individuals in both M. zahlbruckneri and P. stachyoides populations. Based on these findings, approaches that can assist conservation efforts of these species are proposed.

Hawai`i↗

USGS2019

Diversity and abundance of wild bees in an agriculturally dominated landscape of eastern Colorado

Agricultural intensification has resulted in loss of natural and semi-natural habitats impacting several important ecosystem services. One group of organisms that has suffered greatly are the bees and hence pollination, the supporting ecosystem service they complete. The United States Department of Agriculture (USDA) Conservation Reserve Program (CRP) has implemented conservation practices designed to improve habitat for pollinators in agroecosystems by paying to recover environmentally sensitive agricultural land from production, and restoring them by planting native grass mixes, pollinator-friendly legumes and wildflowers. Our study, aimed at demonstrating the efficacy of this practice, measured diversity and abundance of wild bee genera in the agricultural landscape of eastern semiarid regions of Colorado, USA, where CRP practices were implemented. Over our 3-year study, we obtained a total of 16,207 bees belonging to 51 genera. We found inconsistent differences in number of bee genera and abundance of bees in CRP fields supplemented with wildflowers compared to those with conventional grass seed mix. However, we observed only a 40–80% overlap in bee genera between fields supplemented with wildflowers and those with grass seed mixes indicating that diversity was enhanced by having both habitats. With the caveat that 3 years is a very short period to see appreciable changes, our results suggest that recovering environmentally sensitive land can strengthen pollinator populations in landscapes dominated by agricultural activities. In addition, periodic evaluation and maintenance of these recovered lands will further support the efforts towards revitalization of ecosystem services in these areas.

Colorado↗

USGS2022

Divergent responses of butterflies and bees to burning and grazing management in tallgrass prairies

Butterflies and bees contribute significantly to grassland biodiversity and play important roles as pollinators and herbivores. Grassland conservation and management must be seen through the lens of insect conservation and management if these species are to thrive. In North America, grasslands are a product of climate and natural disturbances such as fire and grazing. These natural disturbances have changed considerably since European colonization and subsequent landscape fragmentation. The aim of this study was to better understand the impacts of fire and grazing management on butterfly and bee communities in tallgrass prairie, enabling land managers and conservationists to better protect and manage remnant prairie. We examined butterfly and bee abundance, species richness, and diversity in Minnesota tallgrass prairies managed by grazing or fire. In 2016 and 2017, we surveyed butterflies, bees, vegetation, and surrounding land use at 20 remnant prairies (10 burned and 10 grazed) with known management histories. Butterfly and bee abundance at our study sites were significantly negatively correlated. Butterfly abundance, but not species richness, was higher in burned than grazed prairies, and prairie-associated grass-feeding butterflies were more abundant at sites with higher plant species richness. Bee abundance was unrelated to management type but was higher at sites with sandier soils; bee species richness was positively associated with forb frequency. These findings highlight the challenges of designing management plans tailored to wide groups of pollinators and the potential pitfalls of using one group of pollinators as indicators for another. They also point to the importance of a mosaic of management practices across the prairie landscape.

Minnesota↗

USGS2010

Grassland birds wintering at U.S. Navy facilities in southern Texas

Grassland birds have undergone widespread decline throughout North America during the past several decades. Causes of this decline include habitat loss and fragmentation because of conversion of grasslands to cropland, afforestation in the East, brush and shrub invasion in the Southwest and western United States, and planting of exotic grass species to enhance forage production. A large number of exotic plant species, including grasses, have been introduced in North America, but most research on the effects of these invasions on birds has been limited to breeding birds, primarily those in northern latitudes. Research on the effects of exotic grasses on birds in winter has been extremely limited. This is the first study in southern Texas to examine and compare winter bird responses to native and exotic grasslands. This study was conducted during a period of six years (2003–2009) on United States Navy facilities in southern Texas including Naval Air Station–Corpus Christi, Naval Air Station–Kingsville, Naval Auxiliary Landing Field Waldron, Naval Auxiliary Landing Field Orange Grove, and Escondido Ranch, all of which contained examples of native grasslands, exotic grasslands, or both. Data from native and exotic grasslands were collected and compared for bird abundance and diversity; ground cover, vegetation density, and floristic diversity; bird and vegetation relationships; diversity of insects and arachnids; and seed abundance and diversity. Effects of management treatments in exotic grasslands were evaluated by comparing numbers and diversity of birds and small mammals in mowed, burned, and control areas. To determine bird abundance and bird species richness, birds were surveyed monthly (December–February) during the winters of 2003–2008 in transects (100 meter × 20 meter) located in native and exotic grasslands distributed at all five U.S. Navy facilities. To compare vegetation in native and exotic grasslands, vegetation characteristics were measured during 2003–2008 in the same transects used for bird surveys and included five measures of ground cover, plus estimates of plant species richness, vegetation density (visual obstruction) at two different heights, and shrub numbers. These data, plus seasonal rainfall, were then used to evaluate components of variation in native and exotic grasslands. Relations between total bird numbers and bird species richness with environmental variation in native and exotic grasslands were compared. To compare diversity of arthropods in native and exotic grasslands, insects and arachnids were collected using three different methodologies (standardized sweep-net, random sweep-net, and pitfall traps) during four seasons, (2005–2006), at Naval Air Station–Corpus Christi, Naval Auxiliary Landing Field Waldron, and Naval Air Station–Kingsville. To compare seed abundance and diversity between native and exotic grasslands, seeds were collected for two winters (2004–2006) at Naval Air Station–Corpus Christi and Naval Air Station–Kingsville. To evaluate effects of management on grassland vertebrates, abundance and diversity of birds and small mammals were estimated and compared in exotic grasses subjected to mowing, burning, or no active management (control) for one full year (2008–2009). Observations were made of 1,044 birds of 30 species in grassland transects during five winters. The Savannah Sparrow ( Passerculus sandwichensis ) was the most common bird, which, with 644 detections, accounted for 63 percent of all individuals identified to species. Meadowlarks ( Sturnella spp. ) and Le Conte’s Sparrows ( Ammodramus leconteii ) were the second (10 percent) and third (7 percent) most abundant bird species, respectively. Six of the seven most abundant species detected in grasslands were grassland species, and their numbers accounted for 87 percent of all birds, but 20 of the 30 species (67 percent) that used grasslands were not grassland species. Seven species observed in grassland transects during the study were Species of Conservation Concern: Le Conte’s Sparrow, Sedge Wren ( Cistothorus platensis ), Grasshopper Sparrow ( Ammodramus savannarum ), Long-billed Curlew ( Numenius americanus ), Sprague’s Pipit ( Anthus spragueii ), Cassin’s Sparrow ( Aimophila cassinii ), and Loggerhead Shrike ( Lanius ludovicianus ). Native grasslands consistently supported greater bird species richness than exotic grasslands. In one winter, exotic grasslands supported more birds than native grasslands. Native grasslands were determined to have more forb cover, more bare ground, and greater plant species richness than exotic grasslands, whereas exotic grasslands were characterized by more grass cover and relatively greater vegetation density during dry years. Not only did these individual measures differ between native and exotic grasslands, but components of variation also differed. In native grasslands, grass density and cover contributed more to variation, whereas in exotic grasslands, non-grass vegetation was a greater component of variation. Total bird numbers and bird species richness in native grasslands were related to the principal component that contained a measure of litter cover. Total bird numbers and bird species richness in exotic grasslands indicated no significant relationships with any of the principal components of variation. The two most common insect orders in native grasslands were Hymenoptera and Coleoptera, which accounted for 42 percent of all insects. The two most common insect orders in exotic grasslands were Hemiptera and Homoptera, which accounted for about 80 percent of all insects. Insect family richness was greater in exotic grasslands than in native grasslands in two of four seasons. Proportions of arachnid families were similar in native and exotic grasslands, but arachnid family richness was greater in exotic grasslands than in native grasslands. Abundance of seeds was greater in exotic than in native grasslands. However, seed diversity was greater in native grasslands than in exotic grasslands. Among the three types of management (mowed, burned, and control) applied to exotic grasses, birds were most abundant in the mowed area. Sedge Wrens, however, were never encountered in mowed sites. Meadowlarks were similarly abundant in all treatments, but Le Conte’s Sparrows were detected only in the control (unmanaged) area. Hispid cotton rats ( Sigmodon hispidus ) accounted for 93 percent of all rodent captures, with the number of captures peaking December through February. Hispid cotton rat numbers and total rodent numbers were greatest in control and pre-burn areas, and lowest in the mowed area. Mammal diversity, however, was greatest in the mowed habitat. Native and exotic grasslands differed essentially in all categories (bird numbers and diversity, vegetation characteristics, components of variation, diversity of insects and arachnids, and seed abundance and diversity) used to measure and compare them. This indicates that fundamental ecosystem processes have been altered after native grasslands have undergone invasion and ultimate domination by exotic grass species. Future research in Texas grassland ecosystems is essential because: 1) Texas sustains more area in grasslands than any other state or province in the Central Flyway; 2) Texas serves as the winter destination or migration pathway for hundreds of species of birds, including winter residents and Neotropical migrants; 3) ecology, distribution, and numbers of grassland birds wintering in southern latitudes of the United States remains poorly understood; and 4) climate change threatens to further accelerate advances of invading grass species.

Open-File Report↗

USGS2024

Milkweed and floral resource availability for monarch butterflies (Danaus plexippus) in the United States

The global decline of pollinators, particularly insects, underscores the importance of enhanced monitoring of their populations and habitats. However, monitoring some pollinator habitat is challenging due to widespread species distributions and shifts in habitat requirements through seasons and life stages. The monarch butterfly ( Danaus plexippus ), a migratory insect pollinator that breeds widely throughout North America, presents a unique case study for testing a sampling framework to overcome these challenges. Monarchs exhibit discrete resource needs across life stages (e.g., larval requirement for milkweed, adult requirement for floral nectar), utilizing many land use types across their extensive geographic range during breeding and migration seasons. The Integrated Monarch Monitoring Program (IMMP) uses a standardized protocol with a generalized random tessellation stratified (GRTS) sampling design to gather spatially balanced and ecologically representative information on monarch habitats within the United States. The IMMP is applicable to various land use types and habitats used by breeding monarchs and may be extended to sites outside of the GRTS design to collect data on non-random sites of interest, such as legacy or conservation sites. Additionally, the IMMP’s modular design and publicly available training allows for broad participation, including involvement from community scientists. Here, we summarize habitat metrics (milkweed and floral resources) across 1,233 sites covering much of the monarch’s breeding range. We examine variation in milkweed density and floral resource availability on probabilistic (random) and non-probabilistic (convenience) samples and among land use types (site types). Additionally, we assess resource availability within core geographies for monarch breeding and migration, specifically within the U.S. Fish and Wildlife Service’s Monarch Conservation Units (western, northern, and southern United States). Milkweed density, floral frequency, and floral richness were higher on non-random sites and in the North region. Among site types, milkweed density was highest on Rights-of-Way and Unclassified Grassland, while floral frequency was lowest on Rights-of-Way. The IMMP represents the first field-based habitat monitoring program of this scale for monarchs, yielding a robust dataset on monarchs and their habitats across their breeding range and offering a framework for surveying the habitat of insect species with diverse habitat requirements or widespread distributions.

Frontiers in Ecology and Evolution↗

USGS2026

Society’s struggle with unwanted species: What centuries of history reveal about species bounty programs

Species bounty programs, much like bounty hunters charged to bring fugitives to justice, enlist the public to locate and remove unwanted species through financial incentives. With the goal of reducing population sizes, these programs address perceived ecological and economic damage caused by target species. In this study, we provide the first global assessment of species bounty programs, drawing on evidence from both historical and contemporary efforts across diverse regions and cultural contexts over the past eight centuries. We uncovered a long history of bounty programs involving at least 283 species—mammals, birds, fish, plants, reptiles, mollusks, insects, amphibians, and crustaceans—across 449 programs in 60 countries. Using this collective knowledge, we offer five perspectives on species bounty programs. First, bounty programs are launched for a variety of reasons, including economic (livestock, crops, fisheries, infrastructure), ecological (species, ecosystems), and social (human health) considerations related to unwanted species. Second, bounty programs vary in their design and implementation, ranging from well-planned operations with clear management and conservation objectives to ad hoc operations with limited articulation and investigation of project outcomes. Third, evidence points to unintended consequences, in which bounty programs result in the incidental removal of non-target species or in effects that may inadvertently benefit target species. Fourth, while not always the case, fraudulent activities have been reported, compromising the management outcomes of some programs. Fifth, public perception of bounty programs is highly dynamic and ensuring program engagement remains a persistent challenge. By reviewing the scattered narratives of past and present bounty programs globally, this review seeks to inform the evolving role of this management strategy.

npj Biodiversity↗