Nursery habitats are characterized by favorable conditions for juveniles, including higher food availability and lower predation risk, and disproportionately contribute more individuals per unit area ...to adult populations compared to other habitats. However, nursery habitat inference is complicated by changes in habitat preferences with ontogeny; individuals in early-life stages frequently inhabit different habitats than older juveniles or adults. In this field experiment, we modeled the density of 4 size classes of juvenile blue crabs Callinectes sapidus based on carapace width (CW) across multiple habitats at various locations within an estuarine seascape during the blue crab recruitment season. We examined 4 habitat types—unstructured sand, seagrass meadows, salt marsh edges (SME), and shallow detrital habitat (SDH). Results indicated that densities of small juvenile blue crabs (≤10 mm CW) were highest in seagrass, whereas densities of larger juveniles (16-25 mm CW) were highest in SME. Although densities of juveniles declined in seagrass habitat as a function of size, densities in SME remained consistently high, suggesting that secondary dispersal to SME by smaller juveniles after settlement and recruitment in seagrass may supplement losses in SME due to mortality. Turbidity was positively correlated with densities of both size classes, although our model did not address whether this was due to top-down (refuge) or bottom-up (food availability) mechanisms. Observed patterns in size-specific habitat utilization may result from changing requirements of juvenile blue crabs with size, as animals minimize mortality-to-growth ratios. Our findings emphasize the role of both seagrass and salt marsh habitat within juvenile blue crab ontogeny and emphasize the significance of structurally complex SME habitat in supporting juvenile blue crabs at sizes smaller than previously recognized, challenging past notions about the singular importance of seagrass habitat in this system. Our findings also underscore the need to quantify and preserve the complete chain of habitats used by juveniles.
Taxonomy, floristic studies, biosystematics, classical taxonomy, and modern taxonomic advances; phylogenomics, phylogenetics, and biogeography, including phylogeography; and the description of ...well-documented new taxonomic taxa, monographs, and taxonomic revisions. It incorporates data from classical morphology (including both macro and micro morphology), molecular study, anatomy and ecology, distribution, molecular evolution, evolutionary development, population biology, conservation biology, evolutionary ecology, paleobiology, and related methods and theories in recent development in systematics and floristic studies.
Populations of bumblebees and other pollinators have declined over the past several decades due to numerous threats, including habitat loss and degradation. However, we can rarely investigate the ...role of resource loss due to a lack of detailed long‐term records of forage plants and habitats.
We used 22‐year repeated surveys of more than 262 sites located in grassland, forest, and wetland habitats across Illinois, USA to explore how the abundance and richness of bumblebee food plants have changed over the period of decline of the endangered rusty patched bumblebee Bombus affinis.
We documented a decline in abundance of bumblebee forage plants in forest understories, which our phenology analysis suggests provide the primary nectar and pollen sources for foundress queens in spring, a critical life stage in bumblebee demography. By contrast, the per‐unit area abundance of food plants in primarily midsummer‐flowering grassland and wetland habitats had not declined. However, the total area of grasslands had declined across the region resulting in a net loss of grassland resources.
Synthesis and applications. Our results suggest a decline in spring‐flowering forest understorey plants is a previously unappreciated bumblebee stressor, compounding factors like agricultural intensification, novel pathogen exposure and grassland habitat loss. These findings emphasize the need for greater consideration of habitat complementarity in bumblebee conservation. We conclude that the continued loss of early season floral resources may add additional stress to critical life stages of bumblebees and limit restoration efforts if not explicitly considered in pollinator conservation.
Our results suggest a decline in spring‐flowering forest understorey plants is a previously unappreciated bumblebee stressor, compounding factors like agricultural intensification, novel pathogen exposure and grassland habitat loss. These findings emphasize the need for greater consideration of habitat complementarity in bumblebee conservation. We conclude that the continued loss of early season floral resources may add additional stress to critical life stages of bumblebees and limit restoration efforts if not explicitly considered in pollinator conservation.
Aim
Anticipating the ultimate fraction of a landscape that might be susceptible to invasion is challenging as several species are able to expand the range of environmental conditions used over ...invasion. Despite its relevance, the more proximate processes underlying observed shifts are not sufficiently understood. Habitat selection theory predicts that as population density increases, individuals start using sub‐optimal resources to compensate for the limitation of the preferred ones. However, niche shifts might also occur as result of changes in habitat preferences over time. Here, we tested these alternative hypotheses by investigating nesting resource use and selection over a biological invasion and the relative effect of density‐dependence on such patterns.
Location
Barcelona, Spain.
Methods
We take advantage of a large dataset recording the occurrence of the invasive monk Parakeet, Myiopsitta monachus in Barcelona in the period 1975–2015. We apply generalized linear models to analyse changes in nesting habitat preferences and its interactive effect with conspecific presence.
Results
Temporal changes in nesting habitat use occurred. Palm species were the most commonly used nesting substrate since the beginning of the invasion but the diversity and frequency of use of other nesting substrates increased over time. Changes in nesting substrate use were consistent with a change in habitat selection, when accounting for habitat availability. Although a general role of conspecific aggregation on occupation patterns was found, it was mostly additive. That is, shifts in nesting substrate did not structure in relation to conspecific distribution.
Conclusions
Shifts in nesting resource selection can occur during the spread stage of biological invasions, probably related to innovation and learning, rather than to optimal habitat selection. These shifts present a significant challenge for forecasting efforts and management. However, changes do not happen rapidly over time, highlighting that there is a management opportunity window before significant shifts occur.
Habitat characteristics play an important role in determining the structure of fish communities. The decline in fish diversity and abundance with the decline in coral diversity and cover may be ...explained by habitat specialisation and partitioning among reef fishes and/or preferences for particular corals that are susceptible to disturbance. These preferences may develop at different life history stages. Here, we investigated patterns of habitat specialisation and ontogenetic shifts in habitat preference among 14 co-existing damselfish species at Lizard Island lagoon on the Great Barrier Reef. Although live coral cover contributed only 26% of the substratum, 28% of adults and 57% of new settlers were mostly found on live coral, indicating a strong preference for live coral habitat by new settlers. Only a few species exhibited a high degree of habitat specialisation and low overlap in habitat use with other species. Specialisation differed among species and life stages. New settlers were more commonly associated with finely branched corymbose corals and using those habitats with higher frequency than expected based on habitat availability alone. Adults were more commonly linked to more open branching morphologies or non-coral substrata. Our results suggest that habitat loss may not uniformly impact on all life stages. While adult individuals may not be as reliant as juveniles on corals, detrimental effects of habitat loss on juvenile survival may have longer-term impacts on adult populations. As juveniles show preferential associations with particular coral species, such as corymbose corals, the loss of these growth forms is likely to have the most significant negative impacts on this critical life history stage.
Habitat Split and the Global Decline of Amphibians Becker, Carlos Guilherme; Fonseca, Carlos Roberto; Haddad, Célio Fernando Baptista ...
Science (American Association for the Advancement of Science),
12/2007, Letnik:
318, Številka:
5857
Journal Article
Recenzirano
The worldwide decline in amphibians has been attributed to several causes, especially habitat loss and disease. We identified a further factor, namely "habitat split"--defined as human-induced ...disconnection between habitats used by different life history stages of a species--which forces forest-associated amphibians with aquatic larvae to make risky breeding migrations between suitable aquatic and terrestrial habitats. In the Brazilian Atlantic Forest, we found that habitat split negatively affects the richness of species with aquatic larvae but not the richness of species with terrestrial development (the latter can complete their life cycle inside forest remnants). This mechanism helps to explain why species with aquatic larvae have the highest incidence of population decline. These findings reinforce the need for the conservation and restoration of riparian vegetation.
The importance of positive interactions is increasingly acknowledged in contemporary ecology. Most research has focused on direct positive effects of one species on another. However, there is recent ...evidence that indirect positive effects in the form of facilitation cascades can also structure species abundances and biodiversity. Here we conceptualize a specific type of facilitation cascade—the habitat cascade. The habitat cascade is defined as indirect positive effects on focal organisms mediated by successive facilitation in the form of biogenic formation or modification of habitat. Based on a literature review, we demonstrate that habitat cascades are a general phenomenon that enhances species abundance and diversity in forests, salt marshes, seagrass meadows, and seaweed beds. Habitat cascades are characterized by a hierarchy of facilitative interactions in which a basal habitat former (typically a large primary producer, e.g., a tree) creates living space for an intermediate habitat former (e.g., an epiphyte) that in turn creates living space for the focal organisms (e.g., spiders, beetles, and mites). We then present new data on a habitat cascade common to soft-bottom estuaries in which a relatively small invertebrate provides basal habitat for larger intermediate seaweeds that, in turn, generate habitat for focal invertebrates and epiphytes. We propose that indirect positive effects on focal organisms will be strongest when the intermediate habitat former is larger and different in form and function from the basal habitat former. We also discuss how humans create, modify, and destroy habitat cascades via global habitat destruction, climatic change, over-harvesting, pollution, or transfer of invasive species. Finally, we outline future directions for research that will lead to a better understanding of habitat cascades.
Fragmentation of the boreal forest by linear features, including seismic lines, has destabilized predator–prey dynamics, resulting in the decline of woodland caribou (Rangifer tarandus caribou) ...populations. Restoration of human‐altered habitat has therefore been identified as a critical management tool for achieving self‐sustaining woodland caribou populations. However, only recently has testing of the response of caribou and other wildlife to restoration activities been conducted. Early work has centered around assessing changes in wildlife use of restored seismic lines. We evaluated whether restoration reduces the movement rates of predators and their associated prey, which is expected to decrease predator hunting efficiency and ultimately reduce caribou mortality. We developed a new method for using cameras to measure fine‐scale movement by measuring speed as animals traveled between cameras in an array. We used our method to quantify speed of caribou, moose (Alces alces), bears (Ursus americanus), and wolves (Canis lupus) on treated (restored) and untreated seismic lines. Restoration treatments reduced travel speeds along seismic lines of wolves by 1.38 km/h, bears by 0.55 km/h, and caribou by 1.57 km/h, but did not reduce moose travel speeds. Reduced predator and caribou speeds on treated seismic lines are predicted to decrease encounter rates between predators and caribou and thus lower caribou kill rates. However, further work is needed to determine whether reduced movement rates result in reduced encounter rates with prey, and ultimately reduced caribou mortality.
Resumen
La fragmentación del bosque boreal causado por los accidentes lineales, incluyendo a las líneas sísmicas, ha desestabilizado las dinámicas depredador‐presa, lo que resulta en la declinación de las poblaciones de caribú (Rangifer tarandus caribou). Por esto, la restauración del hábitat con alteraciones antropogénicas ha sido identificada como una herramienta fundamental de gestión para obtener poblaciones autosuficientes de esta especie. Sin embargo, no es hasta hace poco que se ha analizado la respuesta del caribú y otras especies a las actividades de restauración; los primeros trabajos se centraban en analizar los cambios en el uso que les daban las especies a las líneas sísmicas restauradas. Evaluamos si la restauración reduce las tasas de movimiento de los depredadores y sus presas asociadas, las cuales se esperan disminuyan la eficiencia de caza de los depredadores y por último reduzcan la mortalidad del caribú. Desarrollamos un nuevo método para usar las cámaras para medir el movimiento detallado mediante la medición de la velocidad con la que los animales se trasladan a lo largo de una serie de cámaras. Usamos nuestro método para cuantificar la velocidad del caribú, alces (Alces alces), osos (Ursus americanus) y lobos (Canis lupus) en líneas sísmicas tratadas (restauradas) y no tratadas. Los tratamientos de restauración redujeron la velocidad de movimiento de los lobos (reducción de 1.38 km/hora), osos (0.55 km/hora) y caribú (1.57 km/hora), pero no afectaron la velocidad de movimiento de los alces. Se pronostica que la reducción en la velocidad de movimiento sobre las líneas sísmicas disminuye la proporción de encuentros entre el caribú y sus depredadores y, por lo tanto, reduce la proporción de muertes del caribú. Sin embargo, se necesita un análisis más profundo para determinar si la tasa reducida de movimiento resulta en una tasa reducida de encuentros con depredadores y si, por último, esto reduce la mortalidad del caribú.
【摘要】
包括地震测线在内的线性特征对北方森林的破碎化破坏了捕食者‐猎物动态的稳定性, 导致北美驯鹿(Rangifer tarandus caribou)种群的减少。因此, 恢复人为改变的栖息地已被认为是实现北美驯鹿种群自我维持的关键管理工具。然而, 直到最近才有研究测试了驯鹿及其他野生动物对恢复活动的响应;早期的工作主要是评估野生动物对恢复的地震测线的使用变化。本研究评估了恢复活动是否降低了捕食者及其猎物的移动速度, 这预计会降低捕食者的捕食效率, 并最终降低驯鹿的死亡率。我们开发了一种新的方法, 通过计算动物在红外相机阵列中的移动速度, 来用相机测量精细尺度的运动。我们用该方法量化了驯鹿、驼鹿(Alces alces)、美洲黑熊(Ursus americanus)和狼(Canis lupus)在处理(恢复)和未处理的地震测线上的速度。恢复处理使狼沿地震测线的移动速度降低了1.38千米/时, 熊降低了0.55千米/时, 驯鹿降低了1.57千米/时, 但没有降低驼鹿的移动速度。预计在恢复处理的地震测线上降低捕食者和驯鹿的速度会减少捕食者和驯鹿之间的相遇概率, 从而降低驯鹿的死亡率。然而, 还需要进一步的工作来确定降低移动速率是否会降低与猎物相遇概率, 并最终降低驯鹿的死亡率。【翻译:胡怡思;审校:聂永刚】
Habitat‐selection analyses allow researchers to link animals to their environment via habitat‐selection or step‐selection functions, and are commonly used to address questions related to wildlife ...management and conservation efforts. Habitat‐selection analyses that incorporate movement characteristics, referred to as integrated step‐selection analyses, are particularly appealing because they allow modelling of both movement and habitat‐selection processes.
Despite their popularity, many users struggle with interpreting parameters in habitat‐selection and step‐selection functions. Integrated step‐selection analyses also require several additional steps to translate model parameters into a full‐fledged movement model, and the mathematics supporting this approach can be challenging for many to understand.
Using simple examples, we demonstrate how weighted distribution theory and the inhomogeneous Poisson point process can facilitate parameter interpretation in habitat‐selection analyses. Furthermore, we provide a ‘how to’ guide illustrating the steps required to implement integrated step‐selection analyses using the amt package
By providing clear examples with open‐source code, we hope to make habitat‐selection analyses more understandable and accessible to end users.
Habitat‐selection analyses allow researchers to link animals to their environment in support of wildlife management and conservation efforts. We provide a ‘how to' guide for correctly interpreting parameters in habitat‐ and step‐selection functions and for implementing integrated step‐selection analyses using the amt package for program R.
Providing food, timber, energy, housing, and other goods and services, while maintaining ecosystem functions and biodiversity that underpin their sustainable supply, is one of the great challenges of ...our time. Understanding the drivers of land-use change and how policies can alter land-use change will be critical to meeting this challenge. Here we project land-use change in the contiguous United States to 2051 under two plausible baseline trajectories of economic conditions to illustrate how differences in underlying market forces can have large impacts on land-use with cascading effects on ecosystem services and wildlife habitat. We project a large increase in croplands (28.2 million ha) under a scenario with high crop demand mirroring conditions starting in 2007, compared with a loss of cropland (11.2 million ha) mirroring conditions in the 1990s. Projected land-use changes result in increases in carbon storage, timber production, food production from increased yields, and >10% decreases in habitat for 25% of modeled species. We also analyze policy alternatives designed to encourage forest cover and natural landscapes and reduce urban expansion. Although these policy scenarios modify baseline land-use patterns, they do not reverse powerful underlying trends. Policy interventions need to be aggressive to significantly alter underlying land-use change trends and shift the trajectory of ecosystem service provision.
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