Local Habitat Quality Research Articles

Environmental Drivers of Local Demography and Size Plasticity in Fire Salamanders (Salamandra salamandra).

Conspecific amphibian populations may vary widely in local demography and average body size throughout their geographical range. The environmental drivers of variation may reflect geographical gradients or local habitat quality. Among fire salamander populations (Salamandra salamandra), local demography shows a limited range of variation because high concentrations of skin toxins reduce mortality from predation to a minimum, whereas average adult body size varies significantly over a wide range. This study on four neighboring populations inhabiting the catchments of low-order streams in the upper middle Rhine Valley (Koblenz, Germany) focuses on the identification of local environmental drivers of variation in age and body size. I collected 192 individuals at two localities per stream, measured snout-vent length, clipped a toe for posterior skeletochronological age determination, and released salamanders in situ again. Populations were similar in age distribution. Local habitat quality accounted for a significant proportion of demographic variability, mediated by the impact of landscape-induced mortality risk, including roads and agriculture. Still, the main effect of variation in habitat quality was on adult body size, the result of growth rates of aquatic larvae and terrestrial juveniles. Larvae exposed to non-lethal heavy metal contamination in streams developed into smaller juveniles and adults than clean-water larvae, providing evidence for carry-over effects from one stage to another. The generally small average adult size in the Rhine Valley populations compared to those in other parts of the distribution range indicates the action of a still unidentified environmental driver.

Local floral abundance influences bumble bee occupancy more than urban‐agricultural landscape context

Abstract Loss of natural habitat due to increases in agricultural extent raises the question of whether human‐dominated landscape types can support biodiversity, particularly for declining insect pollinators. Compared to more rural agricultural landscapes, urban areas may confer benefits for bumble bee populations by providing stable and diverse floral resources. However, disentangling the effects of local‐ and landscape‐scale characteristics on bumble bee populations in human‐modified landscapes is challenging. Here, we assessed bumble bee occupancy using a repeated transect sampling design conducted during the summers of 2019 and 2020 within the metropolitan area of Madison, WI, and the surrounding agricultural landscape. We fit hierarchical occupancy models to estimate the detection (p) and occupancy () probabilities relative to local habitat quality (floral abundance and floral richness) and landscape (agricultural‐urban gradient) features for eight bumble bee species. We hypothesised that bumble bees were more likely to occupy urban areas, serving as refugia, relative to agricultural sites. We found that the detection probability of all bumble bee species was seasonal and influenced by maximum floral abundance at survey sites, independent of the surrounding land cover type. After accounting for species‐specific detection probabilities, the effect of urbanisation on bee occupancy was weak, and no species were less likely to occupy urban than rural agricultural areas. Our findings suggest that bumble bee occupancy is associated with a ‘honeypot effect’ where local resource availability, in the form of higher floral abundance, is most important in limiting the occupancy of bumble bees across urban and agricultural landscapes.

Enhancing semi-aquatic species representativeness beyond protected areas: dragonflies in networks of conservation corridors

Complementarity is crucial when prioritizing sites for biodiversity conservation. Networks of conservation corridors (CCs) can contribute to regional representativeness by complementing biodiversity features included in existing protected areas (PAs). We ask whether criteria important for CC management and design are effective at prioritizing complementary sites, and how the consideration of species represented in PAs influence criteria performance. We focused on species turnover of generalist and specialist dragonflies across 88 riverine sites. Criteria assessed included site-level estimates of dragonfly species richness, estimates of local habitat quality and corridor width. Measures of local habitat quality were based on either dragonfly indicator species or proportion of alien vegetation. Results showed that CCs complement dragonfly diversity in PAs by contributing unrepresented generalist species. Of the criteria, corridor width was the most efficient at prioritizing complementary sites, while prioritization based on dragonfly indicator species or species richness underperformed. When aiming to prioritize CC sites that also complement sites situated in established PAs, wide corridors with low levels of alien vegetation should be favoured.

Aquatic vegetation types identified during early and late phases of vegetation recovery in the Upper Mississippi River

AbstractAssemblage patterns and processes of aquatic vegetation in most large floodplain rivers are not well understood, particularly after plant recovery. Identifying vegetation types, which are recurring plant groupings based on species composition, diversity, and abundances, can describe plant assembly patterns and environmental drivers that aid conservation planning and management. We used a 22‐year dataset (n = 18,000 sampling plots) to identify aquatic vegetation types during an “early phase” and “late phase” of plant recovery at multiple spatial scales nested within a 500‐km river reach of the Upper Mississippi River, USA. We hypothesized that vegetation types varied according to scale because of the stark environmental differences among riverine habitats and differing regional species pools along the river's latitudinal gradient, and that the late phase of recovery had developed several new vegetation types. We first used cluster analyses at multiple spatiotemporal scales to identify the number of vegetation types and their characteristics, such as indicator species, species compositions and abundances, and diversity index. Then we applied a multivariate regression to pinpoint environmental factors (such as hydrodynamics, system productivity, local habitat, and water quality) that structured those vegetation types. Clustering revealed that ~90% of plots irrespective of recovery phase were not classified into vegetation types, which indicated that most aquatic sampling plots are unique in species composition and unpredictable. However, impounded areas upriver from dams had matured five vegetation types: lotus (Nelumbo lutea Willd.), submersed (a mix of 11 common submersed species), watercelery (Vallisneria americana Michx.), arrowheads (Sagittaria rigida Pursh and Sagittaria latifolia Willd.), and a diverse community (with high diversity indices and multiple life forms). The vegetation types were associated with three environmental gradients related to inundation depth and duration, system productivity, and water clarity. These five vegetation types are known to be of high ecological value to fish and wildlife and thus targets for restoration, for example, the watercelery community is principal forage for migrating canvasback ducks (Aythya valisineria) along the Mississippi River flyway. Our results provide insights on vegetation assembly during recovery and aid habitat conservation by providing quantitative, environmental targets for restoration.

The degree of urbanisation reduces wild bee and butterfly diversity and alters the patterns of flower-visitation in urban dry grasslands

Insect-provided pollination services are increasingly threatened due to alarming declines in insect pollinator populations. One of the main threats to insect pollinators and consequently pollination is urbanisation. Here, we investigate the effects of local habitat quality (patch size, flowering plant richness, bare soil cover, vegetation structure), degree of urbanisation (impervious surfaces) and 3D connectivity on bee, hoverfly and butterfly flower visitors and plant-flower visitor networks in flower-rich urban dry grasslands. Overall, the degree of urbanisation and the quality of the local habitat influenced the flowering plant and pollinator communities. Although flowering plant abundance increased with urbanisation, bee species richness and butterfly species richness decreased with increasing impervious surfaces. Flowering plant richness and ground nesting resource availability were positively related to bee richness and local vegetation structure boosted hoverfly and butterfly visitation rates. In terms of plant–pollinator interactions, insect pollinators visited a lower proportion of the available flowering plants in more urbanised areas and network modularity and specialisation increased with patch size. Our findings show that urban dry grasslands are valuable habitats for species-rich pollinator communities and further highlight the importance of minimizing the intensity of urbanisation and the potential of local management practices to support insect biodiversity in cities.

Hedgerows have contrasting effects on pollinators and natural enemies and limited spillover effects on apple production

Agricultural intensification has resulted in a decline in insect biodiversity and threatens the provision of valuable ecosystem services. Agri-environment schemes (AESs) have been implemented in an effort to conserve biodiversity on farmland and increase agricultural sustainability, but their effectiveness can vary widely. To better determine which factors influence AES effectiveness, the relative roles of local habitat features, habitat quality, and landscape context need to be further explored. The aim of this study was to determine the most important factors influencing field margin AES effectiveness in commercial apple orchards, in terms of arthropod biodiversity conservation and ecosystem service provision. We surveyed wild bees and aphid natural enemies in field margins and apple trees in 20 orchards, ten bordered by hedgerow field margins (an AES) and ten with herbaceous field margins (no hedgerows present, not an AES). We considered field margin floral resources and the cover of semi-natural habitat in the surrounding landscape as indicators of local habitat quality and landscape context, respectively. We furthermore quantified pollination and pest control as measures of ecosystem service delivery and the relationship between arthropod communities and apple yield (initial and final fruit set) and quality. We found that hedgerow presence strongly predicted both pollinator and natural enemy communities and that these relationships were more pronounced than those with local habitat quality and landscape context. Hedgerows were negatively related to wild bee richness and abundance within the orchard, and positively related to natural enemy richness and abundance at the field margin but not within the orchard. We found no relationships between local and landscape factors and ecosystem service delivery, and no relationship between wild bee communities and apple yield, suggesting that apple is not pollen limited in our study system. There was, however, a negative relationship between natural enemy richness and initial fruit set. We conclude that annually cut hedgerows can benefit the conservation of natural enemies, but have limited arthropod-mediated private benefits for apple production, and likely need to be supplemented with additional local habitat resources for the conservation of wild bees. Our findings indicate that local habitat factors can strongly influence biodiversity regardless of landscape context, but that AESs likely need to be designed with separate biodiversity and ecosystem service targets, and specific taxonomic groups, in mind.

Landscape‐scale dynamics of a threatened species respond to local‐scale conservation management

Landscape‐scale approaches are increasingly advocated for species conservation but ensuring landscape level persistence by enlarging the size of patches or increasing their physical connectivity is often impractical. Here, we test how such barriers can be overcome by management of habitat at the local (site‐based) level, using a rare butterfly as an exemplar. We used four surveys of the entire UK distribution of the Lulworth skipper Thymelicus acteon over 40 years to test how local habitat influences population density and colonization/extinction dynamics, and parameterized, validated and applied a metapopulation model to simulate effects of varying local habitat quality on regional persistence. We found the total number of populations in four distribution snapshots between 1978 and 2017 varied between 59 and 84, and from 1997 to 2017 34% of local populations showed turnover (colonization or extinction). Population density was closely linked to vegetation characteristics indicative of management, namely height and food plant frequency, both of which changed through time. Simulating effects of habitat quality on metapopulation dynamics 40 years into the future suggests coordinated changes to two key components of quality (vegetation height and food plant frequency) would increase patch occupancy above the range observed in the past 40 years (50–80%). In contrast, deterioration of either component below threshold levels leads to metapopulation retraction to core sub‐networks of patches, or eventual extirpation. Our results indicate that changes to habitat quality can overcome constraints imposed by habitat patch area and spatial location on relative rates of colonization and local extinction, demonstrating the sensitivity of regional dynamics to targeted in situ management. Local habitat management therefore plays a key role in landscape‐scale conservation. Monitoring of population density, and the monitoring and management of local (site‐level) habitat quality, therefore represent effective and important components of conservation strategies in fragmented landscapes.

Small-scale differences in blue cod length distribution, growth, and trophic ecology in New Zealand

Growth and reproduction in marine fish populations can be strongly influenced by local habitat quality and nutritional resources. Habitat degradation can alter prey composition and availability, and, consequently, trophic position and dietary niche breadth of marine fish. In the present study, we compared length-frequency distributions, growth, stomach contents, and isotopic values (δ13C and δ15N) of blue cod Parapercis colias subpopulations from biogenic reef habitats and habitats that were more strongly influenced by shellfish dredges and fine sediment in New Zealand. Blue cod inhabiting more degraded regions were significantly smaller and relied on different prey items than blue cod from biogenic reef habitats. Results indicated that the isotopic niche areas of blue cod occupying degraded habitats were smaller than those of blue cod inhabiting relatively undisturbed biogenic reefs. Isotope mixing models demonstrated that blue cod from one of the biogenic reef regions relied predominantly on suspended particulate organic matter, while blue cod from the other biogenic and degraded regions primarily relied on macroalgae as their organic matter source. Dietary niche overlap was likely higher for blue cod from degraded habitats, with potential consequences for growth and reproduction. Blue cod inhabiting biogenic reefs showed a high degree of individual specialisation. The present study demonstrated that differences in length distribution, growth, and trophic ecology among blue cod subpopulations coincided with differences in habitat degradation. Ecosystem-based management solutions can help regenerate high-quality biogenic habitats while reducing fisheries mortality within these critical habitats.

Landcover change and habitat quality mediate impacts of temperature and precipitation on population dynamics of a threatened aridland predator

AbstractClimate and landcover change can have synergistic impacts on wildlife populations, but the pervasiveness of these threats and factors that buffer them remain unclear despite important implications for conservation. I evaluated the additive and interactive effects of spatiotemporal variation in temperature, precipitation, and landcover change on annual territory occupancy, colonization, and extinction of a threatened top‐predator, the ferruginous pygmy‐owl (Glaucidium brasilianum), across a vast binational region of the Sonoran Desert over 16 years. I also assessed how local habitat quality and regional population size mediate impacts of these stressors. Despite significant bivariate associations between occupancy and temperature, precipitation, and landcover change, evidence for interactions was much greater than for additive effects. Occupancy of territories imbedded in increasingly disturbed landscapes declined at greater rates with warming winter temperatures, but the temperature had little effect in intact landscapes suggesting they buffer impacts of climate warming. Occupancy increased markedly with precipitation due likely to major positive impacts on prey, but again, interactive effects were stronger given territories of higher quality amplified benefits of precipitation. Impacts of landcover change and habitat quality on extinction depended markedly on regional population sizes. When populations were small and few potential colonists were present, high‐quality habitat and low landcover change failed to reduce extinction. When populations were large, however, high‐quality habitat and more intact landscapes, which best foster dispersal, reduced extinction. Hence, complex interacting processes linked to the effects of precipitation and habitat quality on carrying capacity, landcover change on habitat connectivity and vulnerability to rising temperatures, and local population sizes simultaneously drove dynamics. Efforts to identify and protect high‐quality habitat and limit landcover change can enhance conservation but will be most efficient in intact landscapes. Efforts to enhance local habitat quality and quantity, and directly augment populations should consider broader landscape contexts linked to habitat connectivity and potential source populations.

Direct and Spillover Effects of Urban Land Expansion on Habitat Quality in Chengdu-Chongqing Urban Agglomeration

Urban land expansion has dramatically changed the spatial distribution patterns and functional structure of habitats. Previous studies on the spatial externality effect of urban land expansion on the habitat quality of urban agglomerations are still insufficient. With the use of remote sensing and statistical data from 2000 to 2018, this study explored the evolutionary relationship between urban land expansion and habitat quality in the Chengdu-Chongqing urban agglomeration (CUA) using the bivariate local autocorrelation method and spatial Durbin model. Partial differential equation decomposition of the local and spatial spillover effects was implemented to investigate the marginal effects of the influencing factors. The highlights of the results are as follows: CUA’s urban land increased by 2890.42 km2 from 2000 to 2018, mainly caused by urban encroachment over farmland and grassland. New urban lands were situated primarily in the main urban districts of Chengdu and Chongqing; urban expansion intensity slowed to 7.64% in 2010–2018, declining by 53.95% from 2000 to 2010. The average habitat quality decreased to 0.905, and two “ring-shaped decline areas” were formed around the main urban areas of Chengdu and Chongqing. “Low-High” and “Low-Low” clusters were the main associations between urban land expansion and habitat quality changes. The impact of urban land expansion on local habitat quality changed from insignificant to negative, while its spatial spillover effects over adjacent areas have increased the negative environmental externalities to habitat quality in adjacent areas through spatial spillovers. Our findings provide evidence for urban agglomerations such as CUA that are still being cultivated to carry out cross-city joint protection strategies of habitat quality, also proving that habitat quality protection should be an integration of urban expansion regulation, natural adaptation and socioeconomic adjustment.

Diverging effects of geographic distance and local habitat quality on the genetic characteristics of three butterfly species

Abstract The genetic characteristics of neutral loci in natural populations are shaped by the interplay between genetic drift and gene flow that themselves result from key ecological and evolutionary processes. Because of their influence on population size, habitats characteristics may influence substantially populations' genetic characteristics. However, past studies focused primarily on variables related to habitat quantity while habitat quality was largely overlooked. We therefore combined genetic data to detailed habitat descriptions of three sympatric butterfly species having different ecological needs to quantify the relative contribution of geographic distance and habitat quality/quantity on their genetic characteristics. In all species, the genetic diversity was greater in larger and good quality patches. The genetic differentiation of Lycaena helle (specialist species with limited dispersal) was mostly explained by geographical distances. This effect was dampened by habitat quality as populations inhabiting low quality patches had higher genetic differentiations indicating that the constraints set by local environmental factors increased genetic drift. In Boloria eunomia (specialist species with greater dispersal), the genetic differentiation was only influenced by geographic distance. Finally, in Brenthis ino (more generalist species with greater dispersal), isolation‐by‐distance was weak and habitat characteristics were unrelated to genetic differentiation. The different effect of habitat quality on these species' genetic characteristics suggests that fundamental ecological traits underpin their response to habitat degradation. In L. helle, a species with major conservation concerns, these results show that preserving habitat quality and connectivity among populations' are important to ensure the maintenance of fully functional metapopulations.

Using experimental reintroductions to resolve the roles of habitat quality and metapopulation dynamics on patch occupancy in fragmented landscapes.

Declines of species in fragmented landscapes can potentially be reversed either by restoring connectivity or restoring local habitat quality. Models fitted to snapshot occupancy data can be used to predict the effectiveness of these actions. However, such inferences can be misleading if the reliability of the habitat and landscape metrics used is unknown. The only way to unambiguously resolve the roles of habitat quality and metapopulation dynamics is to conduct experimental reintroductions to unoccupied patches so that habitat quality can be measured directly from data on vital rates. We, therefore, conducted a 15-year study that involved reintroducing a threatened New Zealand bird to unoccupied forest fragments to obtain reliable data on their habitat quality and reassess initial inferences made by modeling occupancy against habitat and landscape metrics. Although reproductive rates were similar among fragments, subtle differences in adult survival rates resulted in λ (finite rate of increase) estimations of <0.9 for 9 of the 12 fragments that were previously unoccupied. This was the case for only 1 of 14 naturally occupied fragments. This variation in λ largely explained the original occupancy pattern, reversing our original conclusion from occupancy modeling that this occupancy pattern was isolation driven and suggesting that it would be detrimental to increase connectivity without improving local habitat quality. These results illustrate that inferences from snapshot occupancy should be treated with caution and subjected to testing through experimental reintroductions in selected model systems.

Bees increase seed set of wild plants while the proportion of arable land has a variable effect on pollination in European agricultural landscapes

Background and aims – Agricultural intensification and loss of farmland heterogeneity have contributed to population declines of wild bees and other pollinators, which may have caused subsequent declines in insect-pollinated wild plants. Material and methods – Using data from 37 studies on 22 pollinator-dependent wild plant species across Europe, we investigated whether flower visitation and seed set of insect-pollinated plants decline with an increasing proportion of arable land within 1 km. Key results – Seed set increased with increasing flower visitation by bees, most of which were wild bees, but not with increasing flower visitation by other insects. Increasing proportion of arable land had a strongly variable effect on seed set and flower visitation by bees across studies. Conclusion – Factors such as landscape configuration, local habitat quality, and temporally changing resource availability (e.g. due to mass-flowering crops or honey bee hives) could have modified the effect of arable land on pollination. While our results highlight that the persistence of wild bees is crucial to maintain plant diversity, we also show that pollen limitation due to declining bee populations in homogenized agricultural landscapes is not a universal driver causing parallel losses of bees and insect-pollinated plants.

Adaptive and Plastic Responses to Environmental Variation: Introduction to a Virtual Symposium in The Biological Bulletin.

Adaptive and Plastic Responses to Environmental Variation: Introduction to a Virtual Symposium in The Biological Bulletin.

Does soil bioengineering benefits aquatic biodiversity? An empirical study of the relative influence of local and regional drivers on benthic macroinvertebrate assemblages

Riverine ecosystems form a dendritic network in which landscape and catchment-scale properties influence freshwater community structure. Placed in a restoration framework, this suggests that regional drivers can overrule the benefit of measures aiming at improving local habitat quality. Disentangling the relative influence of local and regional drivers on freshwater communities is thus crucial for ecosystem management and restoration. Along riverbanks, soil bioengineering is often used to both control erosion and improve ecological conditions. Soil bioengineering techniques aim at copying naturally functioning riverbank models and can thus be viewed as riparian ecosystem restoration. Nevertheless, these techniques are mostly designed at the local scale and are implemented in a broad range of rivers. This implies large variations in regional drivers, which may greatly influence the response of freshwater communities to restoration efforts. We studied 37 riverbanks, from civil engineering to soil bioengineering, plus natural willow stands, in the foothills of the Alps and Jura Mountains, and assessed the relative influence of local (terrestrial and aquatic habitat conditions) and regional (water quality, hydrological context and land cover composition) drivers on benthic macroinvertebrate assemblages. Using multivariate GLM and structural equation modelling, we investigated variations in the taxonomic and functional composition and in the diversity of native, exotic, shredder and scraper taxa to both set of drivers. Our results showed that soil bioengineering improved local habitat conditions, with an increase in the vegetation density and in the aquatic habitat quality. These changes directly influenced functional composition but indirectly diversity patterns. Instead, we found that native and shredder species richness increased between civil engineered and soil bioengineered structures, suggesting a positive effect of vegetated riverbanks on other local abiotic factors (i.e. shade, water temperature, organic matter supply). Our results also showed that macroinvertebrates were more influenced by regional than by local drivers. Thus, the hydrological context best explained the composition of taxa feeding habits and variation in taxa diversity, with larger abundance and richness of scrapers and shredders in small headwater streams. Land cover ranked second in explaining variation in functional composition. Also, the diversity of natives, scrapers and shredders increased as the proportion of predominantly urban landscapes decreased. Finally, the abundance of scraper and native species increased with water quality, while the richness of exotic species decreased. Overall, these results highlight the hierarchical structure of local and regional drivers on freshwater communities. Along river networks, catchment-scale properties and landscape attributes are major drivers of macroinvertebrate assemblages. Soil bioengineering improves habitat quality and as such appears to be a good compromise solution to control erosion and support freshwater communities, even though this nature-based solution cannot solve anthropogenic pressures at larger scales. To improve the efficiency of restoration efforts, integrated approaches accounting for both local and regional drivers remains a priority.

Qualitative and Quantitative Loss of Habitat at Different Spatial Scales Affects Functional Moth Diversity

Land use change has led to large-scale insect decline, threatening ecosystem resilience through reduced functional diversity. Even in nature reserves, losses in insect diversity have been detected. Hereby, changes in local habitat quality and landscape-scale habitat quantity can play a role driving functional diversity toward erosion. Our aim was to analyze how local and landscape-scale factors simultaneously affect functional insect diversity. Therefore, we sampled moths in two Italian coastal forest reserves at 60 sites. Our focus was on functional richness, redundancy and niche occupation, being important for ecosystem resilience, following the insurance framework. Ecological information about 387 species and 14 traits was used to analyze functional diversity. Twenty-five functional groups were recognized and used to estimate niche occupation and redundancy. Fourteen local and 12 landscape-scale factors were measured and condensed by using Principal Components Analysis. The resulting PC-axes served as predictors in linear mixed effects models. Functional richness, redundancy and niche occupation of moths were lower at sites with low habitat quality and quantity, indicating reduced ecosystem resilience. Especially landscape diversity and habitat structure, viz. a humidity-nutrient gradient, but also plant diversity, were promoting functional richness. Landscape fragmentation, indicating increased impermeability for insects, reduced local functional richness, redundancy and niche occupation. Local habitat quality and landscape-wide habitat quantity are both important for maintaining functional insect diversity inside reserves. Therefore, small and isolated nature reserves might fail in preserving biodiversity and ecosystem functions through adverse effects acting from the surrounding landscape structure and configuration.

Differences in Response of Butterfly Diversity and Species Composition in Urban Parks to Land Cover and Local Habitat Variables

Background and Objectives: As urbanisation is a significant global trend, there is a profound need for biodiversity protection in urban ecosystems. Moreover, the potential of urban green space to support urban biodiversity should be appreciated. Butterflies are environmental indicators that are sensitive to urbanisation. Therefore, it is important to identify butterfly distribution patterns and the factors influencing butterfly diversity and species composition in urban parks within cities. Research Highlights: To our knowledge, ours is the first study evaluating the effects of both land cover and local habitat features on butterfly species composition in urban parks of Beijing, China. Materials and Methods: In this study, we surveyed butterfly richness and abundance in 28 urban parks in Beijing, China. The parks differed in age and location in the urban area. Meanwhile, we investigated the green space in the surroundings of the parks at multi-spatial scales at the landscape level. We also investigated local park characteristics including the age of the park (Age), perimeter/area ratio of the park (SQPRA), area of the park (ha) (Area), green space cover within the park (Greenp), nectar plant species richness (Necpl), abundance of flowering nectar plants (Necabu) and overall plant species richness (Pl). Generalised linear models (GLMs) and redundancy discriminant analysis (RDA) were applied to relate butterfly diversity and butterfly species composition to environmental variables, respectively. Results: We recorded 3617 individuals belonging to 26 species from July to September in 2019. Parks on the city fringe had significantly higher butterfly diversity. Butterfly species richness was mostly related to total plant richness. The abundance of flowering nectar plants was closely linked to butterfly abundance. Land cover had little impact on butterfly diversity and community structure in urban parks. Conclusions: Once a park has sufficient plants and nectar resources, it becomes a useful haven for urban butterflies, regardless of the surrounding land cover. Well-planned urban parks focused on local habitat quality support butterfly conservation.

Habitat Features Predict Carrying Capacity of a Recovering Marine Carnivore

ABSTRACTThe recovery of large carnivore species from over‐exploitation can have socioecological effects; thus, reliable estimates of potential abundance and distribution represent a valuable tool for developing management objectives and recovery criteria. For sea otters (Enhydra lutris), as with many apex predators, equilibrium abundance is not constant across space but rather varies as a function of local habitat quality and resource dynamics, thereby complicating the extrapolation of carrying capacity (K) from one location to another. To overcome this challenge, we developed a state‐space model of density‐dependent population dynamics in southern sea otters (E. l. nereis), in which K is estimated as a continuously varying function of a suite of physical, biotic, and oceanographic variables, all described at fine spatial scales. We used a theta‐logistic process model that included environmental stochasticity and allowed for density‐independent mortality associated with shark bites. We used Bayesian methods to fit the model to time series of survey data, augmented by auxiliary data on cause of death in stranded otters. Our model results showed that the expected density at K for a given area can be predicted based on local bathymetry (depth and distance from shore), benthic substrate composition (rocky vs. soft sediments), presence of kelp canopy, net primary productivity, and whether or not the area is inside an estuary. In addition to density‐dependent reductions in growth, increased levels of shark‐bite mortality over the last decade have also acted to limit population expansion. We used the functional relationships between habitat variables and equilibrium density to project estimated values of K for the entire historical range of southern sea otters in California, USA, accounting for spatial variation in habitat quality. Our results suggest that California could eventually support 17,226 otters (95% CrI = 9,739–30,087). We also used the fitted model to compute candidate values of optimal sustainable population abundance (OSP) for all of California and for regions within California. We employed a simulation‐based approach to determine the abundance associated with the maximum net productivity level (MNPL) and propose that the upper quartile of the distribution of MNPL estimates (accounting for parameter uncertainty) represents an appropriate threshold value for OSP. Based on this analysis, we suggest a candidate value for OSP (for all of California) of 10,236, which represents 59.4% of projected K. © 2021 The Authors. The Journal of Wildlife Management published by Wiley Periodicals LLC on behalf of The Wildlife Society.

The effects of taxonomy, diet, and ecology on the microbiota of riverine macroinvertebrates.

Freshwater macroinvertebrates play key ecological roles in riverine food webs, such as the transfer of nutrients to consumers and decomposition of organic matter. Although local habitat quality drives macroinvertebrate diversity and abundance, little is known about their microbiota. In most animals, the microbiota provides benefits, such as increasing the rate at which nutrients are metabolized, facilitating immune system development, and defending against pathogenic attack. Our objectives were to identify the bacteria within aquatic invertebrates and determine whether their composition varied with taxonomy, habitat, diet, and time of sample collection. In 2016 and 2017, we collected 264 aquatic invertebrates from the mainstem Saint John (Wolastoq) River in New Brunswick, Canada, representing 15 orders. We then amplified the V3‐V4 hypervariable region of the 16S rRNA gene within each individual, which revealed nearly 20,000 bacterial operational taxonomic units (OTUs). The microbiota across all aquatic invertebrates were dominated by Proteobacteria (69.25% of the total sequence reads), but they differed significantly in beta diversity, both among host invertebrate taxa (genus‐, family‐, and order‐levels) and temporally. In contrast to previous work, we observed no microbiota differences among functional feeding groups or traditional feeding habits, and neither water velocity nor microhabitat type structured microbiota variability. Our findings suggest that host invertebrate taxonomy was the most important factor in modulating the composition of the microbiota, likely through a combination of vertical and horizontal bacterial transmission, and evolutionary processes. This is one of the most comprehensive studies of freshwater invertebrate microbiota to date, and it underscores the need for future studies of invertebrate microbiota evolution and linkages to environmental bacteria and physico‐chemical conditions.

Long‐term effects of colonization–extinction dynamics of generalist versus specialist wood‐decaying fungi

Abstract Long‐term metapopulation persistence is mediated by the dynamics of colonization and extinction. To understand and predict future species occupancy in changing landscapes, we must account for the dynamic rates that shape the occupancy and disentangle their dependence on environmental conditions. Specialist and generalist species may differ in their dynamics in systematic ways. Using an extensive, large‐scale repeat survey dataset for wood‐decaying fungi, we fitted dynamic metapopulation models for ten species, ranging from generalists to specialists with differing resource requirements. We first estimated base rates of colonization and extinction and tested their relationships to species' degree of specialization. We then tested for effects of local and landscape scale variables on the colonization and extinction rates. Finally, using the fitted models and a scenario of future forest development we projected future colonization–extinction dynamics over 100 years to test for differences in species occupancies between production stands and set‐aside stands. Our study revealed a striking pattern of decreasing colonization rates with increasing degree of specialization across species, along with concomitantly increasing extinction rates. Strong sensitivity of colonization probabilities to local habitat quality (dead wood volume and stand age) in specialist but not generalist species constrained the regional occupancy of specialists, especially in production forest. We found evidence for short‐range dispersal limitation in two specialists, but no effect of our measure for landscape‐scale connectivity on colonization rates. Simulations of future metapopulation dynamics resulted in decreasing and lower final occupancy in production forest than in set‐asides, especially of specialist species. In set‐aside stands, however, specialists increased over time to relatively high occupancies. Synthesis. Colonization–extinction dynamics of wood‐decaying fungi varied with species' degree of specialization. Increasing specialization was associated with increasing sensitivity of colonization rates to habitat conditions, and partly local connectivity, as well as with increasing extinction rates. Low landscape‐scale occupancies of specialist as compared to generalist wood‐decaying fungi are thus maintained by a combination of lower colonization rates, particularly in production forest, and higher extinction rates.