Global change has altered the nature of disturbance regimes, and megafire events are increasingly common. Megafires result in immediate changes to habitat available to terrestrial wildlife over broad ...landscapes, yet we know surprisingly little about how such changes shape space use of sensitive species in habitat that remains. Functional responses provide a framework for understanding and predicting changes in space use following habitat alteration, but no previous studies have assessed functional responses as a consequence of megafire. We studied space use and tested for functional responses in habitat use by breeding greater sage‐grouse (Centrocercus urophasianus) before and after landscape‐level changes induced by a >40,000 ha, high‐intensity megafire that burned sagebrush steppe in eastern Idaho, USA. We also incorporated functional responses into predictive resource selection functions (RSFs) to map breeding habitat before and after the fire. Megafire had strong effects on the distribution of available resources and resulted in context‐dependent habitat use that was heterogeneous across different components of habitat. We observed functional responses in the use and selection of a variety of resources (shrubs and herbaceous vegetation) for both nesting and brood rearing. Functional responses in the use of nesting habitat were influenced by the overarching effect of megafire on vegetation, whereas responses during brood rearing appeared to be driven by individual variation in available resources that were conditional on nest locations. Importantly, RSFs built using data collected prior to the burn also had poor transferability for predicting space use in a post‐megafire landscape. These results have strong implications for understanding and predicting how animals respond to a rapidly changing environment, given that increased severity, frequency, and extent of wildfire are consequences of global change with the capacity to reshape ecosystems. We therefore demonstrate a conceptual framework to better understand space use and aid habitat conservation for wildlife in a rapidly changing world.
We studied space use of breeding greater sage‐grouse before and after landscape‐level changes to nesting and brood‐rearing habitats that were induced by a megafire event that burned sagebrush steppe in eastern Idaho, USA. Megafire had strong effects on the distribution of resources and resulted in context‐dependent habitat use and selection that were heterogeneous across different components of sage‐grouse habitat. Functional responses in the use and selection of nesting habitat were shaped by the overarching effect of megafire on vegetation, and models built using data collected prior to the megafire had poor transferability for predicting space use in a post‐megafire landscape.
Deforestation can modify stream habitat and the functional structure of fish assemblages. The aims of this study were (a) to identify whether deforestation has a similar effect on local habitats from ...two biogeographically distinct river basins in a tropical region; (b) to identify how fish trait–habitat relationships were influenced by deforestation; and (c) to compare functional redundancy patterns in these basins.
Environmental and biological variables were obtained for 160 stream reaches, 85 located in the Alto Paraná River basin and 75 in the Machado River basin. Traits were associated with body size, habitat preference, food items and foraging period. Linear models were constructed to verify the environmental convergence of habitats across streams from the Alto Paraná and the Machado basins. An RLQ and a fourth‐corner analysis were conducted to investigate how deforestation affected habitat variables and trait–habitat relationships. The nearest relative index (NRI) was used as a functional redundancy measure.
Deforestation led to a similar habitat gradient from streams with a higher proportion of coarse roots in more forested catchments to streams with streamside grasses, bare soil and unconsolidated substrate in more deforested catchments; however, a general pattern of fish trait–habitat relationships was not identified across basins. Functional redundancy was associated with a long history of habitat loss in the Alto Paraná streams, whereas functional complementarity was related to more recent and less intense habitat loss in Machado streams.
We believe that differences in regional species pools and historical processes between the basins influenced the fish functional responses to deforestation. Nevertheless, the results highlighted the importance of stream habitat heterogeneity and the presence of preserved forest fragments in a region to prevent the loss of unique traits. Decision‐makers should therefore maintain large forest fragments and restore riparian forests to preserve stream habitat and the functional structure of fish assemblages.
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.
Uso de Reintroducciones Experimentales para Determinar las Funciones de la Calidad delHábitat y las Dinámicas Metapoblacionales en la Ocupación de Paisajes Fragmentados
Resumen
La declinación de las especies en paisajes fragmentados tiene el potencial de ser revertida mediante la restauración de la conectividad o de la calidad del hábitat. Se pueden utilizar los modelos ajustados a los datos de ocupación instantánea para predecir la efectividad de estas acciones. Sin embargo, estas inferencias pueden ser engañosas si se desconoce la confiabilidad de las medidas usadas para el hábitat y el paisaje. La única manera de determinar inequívocamente las funciones de la calidad del hábitat y de las dinámicas metapoblacionales es mediante la realización de reintroducciones experimentales en los fragmentos no ocupados, de tal manera que se puede medir directamente la calidad del hábitat a partir de los datos de las tasas vitales. Por lo tanto, realizamos un estudio de 15 años que involucró la reintroducción de un ave neozelandesa amenazada en fragmentos no ocupados de bosque para así obtener datos confiables de la calidad del hábitat y reevaluar las inferencias iniciales hechas por los modelos de ocupación en relación con las medidas de hábitat y paisaje. Aunque las tasas de reproducción fueron similares entre los fragmentos, algunas diferencias sutiles en las tasas de supervivencia de los adultos resultaron en estimaciones λ (una tasa finita de incremento) <0.9 en nueve de los doce fragmentos que no estaban ocupados previamente. Este fue el caso para uno solo de los 14 fragmentos ocupados naturalmente. Esta variación λ explicó en su mayoría el patrón original de ocupación, revirtiendo nuestra conclusión original obtenida del modelo de ocupación de que este patrón estuvo causado por el aislamiento y sugiriendo que sería perjudicial incrementar la conectividad sin mejorar la calidad del hábitat local. Estos resultados muestran que las inferencias a partir de la ocupación instantánea deberían abordarse con cautela y estar sujetas al análisis mediante reintroducciones experimentales en sistemas modelados selectos.
Urbanization and land cover change are significantly affecting the availability of habitats for wildlife worldwide. However, linking species persistence to large-scale habitat changes is challenging, ...especially when wildlife monitoring data is lacking. In China, the Eurasian otter (
Lutra lutra
) is a species of conservation concern and is listed as endangered as a consequence of declining populations across the country. Hong Kong is home to a small population of Eurasian otters, which are primarily restricted to a set of wetlands in the inner Deep Bay area. However, the drivers of their historical distribution changes are largely unknown. We combined otter spraint data from 2018 to 2019 with historical records of otter data spanning 1959–2018 to examine otter habitat preference and changes in their distribution, relating this with land cover changes measured by Landsat-5 and Landsat-8 satellite remote sensing in the past (1986 and 1995) and present (2018) using supervised random forest classification. We found that otters showed habitat preference for fish ponds and watercourses, and persisted in areas where fish pond area was more readily available. We also found no significant effect of the extent of land cover changes on otter persistence, suggesting that the species is resilient to some level of fish pond loss and find value in available terrestrial habitats. Our results demonstrate the utility of relating satellite remote sensing data to species distribution data over decadal time scales and highlight the importance of managing terrestrial and wetland habitats for otters and other key species in increasingly urbanized landscapes.
•Physical complexity increased cryptobenthic fish interaction with the substrate.•Physical complexity hindered foraging activities of pelagic and cryptobenthic fish.•Cryptobenthic fish interacted and ...fed more from developed fouling assemblages.•Seeding with oysters increased feeding activity of cryptobenthic fish.•We can design better eco-engineering solutions for fish communities with these data.
The replacement of natural marine habitats with less structurally complex human infrastructure has been linked to the homogenisation of epibenthic assemblages and associated changes in fish assemblages. To mitigate these impacts, eco-engineering efforts have focussed on increasing the physical and biogenic complexity of artificial structures, in the form of crevices added to seawalls and the seeding of the substrate with habitat-forming organisms such as oysters. While these studies have assessed how these interventions affect epibenthic assemblages, the effect of these strategies on the behaviour, such as feeding and habitat use, of different functional groups of fish (e.g. cryptobenthic and pelagic) remains uncertain. To do this, we manipulated complexity on seawalls by adding concrete tiles with different physical (flat or structured with crevices and ridges) and biogenic (seeding with two common habitat-forming species or naturally recruited fouling) complexities. We assessed pelagic and cryptobenthic fish species composition, abundance, interaction time with the tiles and number of feeding bites on three occasions 8–12 months after deployment. Cryptobenthic fish interacted more with physically complex tiles than flat tiles, regardless of biogenic complexity. In contrast, cryptobenthic fish fed more from flat tiles compared to physically complex tiles, and also appeared to feed more from tiles seeded with oysters. Pelagic fish interacted and fed more from naturally fouled tiles compared to unfouled control tiles, regardless of physical complexity. This study showed that manipulating complexity at the scales used here affects behaviour of fish, but it does not affect fish community. Increasing physical complexity facilitated fish use of seawalls as habitat by providing refuge, while it also hindered fish feeding by providing refuge for their prey. Cryptobenthic fish are important trophic linkages in their ecosystems and we have shown that by changing habitat complexity, we can change the habitat use and feeding activity of these fish, allowing them to fulfil this essential ecosystem role.
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.
Semi‐natural habitats provide important resources for wild bees in agricultural landscapes. Landscapes under management are dynamic and floral resources fluctuate in space and time. Thus, promoting ...different semi‐natural habitat types within landscapes could be key to support diverse bee meta‐communities throughout the season.
Here, we integrate analyses of α‐diversity (species richness) and β‐diversity and species‐habitat networks to examine the relative contribution of all major semi‐natural habitats to wild bee meta‐communities in agricultural landscapes. We sampled extensively and conventionally managed meadows, flower strips, hedgerows and forest edges in spring, early and late summer in 25 landscapes in Switzerland.
Habitat types varied in their importance for wild bees throughout the season: While extensively managed meadows supported more rare species, habitat specialists and bee species overall than the other habitat types, flower strips were most important later in the season. Each of the five investigated habitat types harboured relatively unique sets of species with different habitats generally acting as distinct modules in the overall bee‐habitat network.
Not only flower richness in a habitat per se, but also flower‐habitat network properties (habitat strength and functional complementarity) were good predictors of wild bee richness. In addition to local floral richness, landscape composition and configuration interactively influenced β‐diversity patterns across habitats.
Synthesis and applications. Our study highlights the value of pollinator‐habitat network analysis to inform pollinator conservation management at the landscape scale, especially when combined with information on floral resources and flower‐habitat networks. Maintaining different types of semi‐natural habitats offers diverse and complementary resources throughout the season, which are crucial to sustain diverse wild bee meta‐communities in agricultural landscapes. Particularly meadow extensification schemes can play a key role in safeguarding rare and specialist species in these landscapes. While locally a high flower richness promoted bee abundance and richness in general, our results indicate that increasing connectivity between habitat patches in landscapes dominated by arable crops appears to improve species exchange between local bee communities of different habitats, thereby possibly increasing their resilience to disturbances.
Zusammenfassung
Naturnahe Lebensräume bieten wichtige Ressourcen für Wildbienen in Agrarlandschaften. Diese bewirtschafteten Landschaften sind jedoch dynamisch, und die Verfügbarkeit von Ressourcen wie Blütenpflanzen kann stark variieren. Daher könnte die Förderung verschiedener Typen von naturnahen Lebensräumen der Schlüssel sein für den ganzjährigen Schutz artenreicher Wildbienengemeinschaften.
In dieser Studie analysieren wir α‐Diversität (Artenzahl), β‐Diversität (Ähnlichkeit der Artzusammensetzung) und Art‐Lebensraum‐Netzwerke, um die relative Wichtigkeit der häufigsten naturnahen Lebensräume in Agrarlandschaften für artenreiche Wildbienengemeinschaften zu untersuchen. In 25 Landschaften in der Schweiz sammelten wir Daten zu Wildbienenarten in extensiv und konventionell bewirtschafteten Wiesen, Buntbrachen, an Hecken und Waldrändern im Frühling, Früh‐ und Spätsommer.
Die verschiedenen Lebensraumtypen waren von unterschiedlicher Wichtigkeit für Wildbienen, je nach Zeitpunkt in der Saison. Während extensiv bewirtschaftete Wiesen generell mehr seltene Arten, Lebensraumspezialisten und mehr Bienenarten beherbergten als die anderen Lebensraumtypen, waren Buntbrachen vor allem im Juli wichtig. In jedem der fünf untersuchten Lebensraumtypen fanden wir eine relativ einzigartige Artzusammensetzung: Im Bienen‐Lebensraum‐Netzwerk gliederten sich die Lebensraumtypen in verschiedene Module.
Nicht nur Blütenpflanzenvielfalt in einem Lebensraum, sondern auch Blütenpflanzen‐Lebensraum‐Netzwerk Eigenschaften («Lebensraum‐Stärke» und «funktionelle Komplementarität») konnten die Wildbienenvielfalt in einem Lebensraum voraussagen. Zusätzlich zur lokalen Blütenpflanzenvielfalt beeinflussten die Landschaftszusammensetzung und ‐konfiguration die β‐Diversität der Wildbienen (Ähnlichkeit der Artzusammensetzung) zwischen den Lebensraumtypen.
Unsere Studie unterstreicht den Wert der Analyse von Bestäuber‐Lebensraum‐Netzwerken für die Förderung und den Schutz der Bestäuber auf Landschaftsebene, insbesondere in Kombination mit Informationen zu Ressourcen wie Blütenpflanzen. Die Erhaltung verschiedener Typen naturnaher Lebensräume bietet während der gesamten Saison vielfältige und sich ergänzende Ressourcen, die für die Erhaltung vielfältiger Wildbienengemeinschaften in Agrarlandschaften von entscheidender Bedeutung sind. Insbesondere Massnahmen zur Extensivierung von Wiesen können eine Schlüsselrolle beim Schutz seltener und spezialisierter Arten in diesen Landschaften spielen. Während eine lokal hohe Blütenpflanzenvielfalt die Anzahl und Vielfalt der Wildbienen im Allgemeinen fördert, kann eine bessere Vernetzung der Lebensräume in von Ackerbau dominierten Landschaften den Artenaustausch zwischen lokalen Bienengemeinschaften verbessern. Dies erhöht möglicherweise die Widerstandsfähigkeit der Wildbienengemeinschaften gegenüber Störungen.
Our study highlights the value of pollinator‐habitat network analysis to inform pollinator conservation management at the landscape scale, especially when combined with information on floral resources and flower‐habitat networks. Maintaining different types of semi‐natural habitats offers diverse and complementary resources throughout the season, which are crucial to sustain diverse wild bee meta‐communities in agricultural landscapes. Particularly meadow extensification schemes can play a key role in safeguarding rare and specialist species in these landscapes. While locally a high flower richness promoted bee abundance and richness in general, our results indicate that increasing connectivity between habitat patches in landscapes dominated by arable crops appears to improve species exchange between local bee communities of different habitats, thereby possibly increasing their resilience to disturbances.
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.
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.
All of the marine environments have been found to be affected by anthropogenic impacts with the sprawl of marine infrastructure being one of the most extreme factors modifying habitats. Artificial ...reefs (ARs) are a common type of these infrastructures, that are frequently used for fisheries management, species conservation and habitat restoration. Attractiveness of ARs for some species have been demonstrated, however little is known about the fitness of individuals that occupy ARs compared to natural reefs. ARs that provide lower fitness advantages may become ecological traps. We examined individual fitness of three species (Trachinops caudimaculatus, Vincentia conspersa and Trinorfolkia clarkei) occupying three different habitat types: natural reefs, Reef Ball reefs (RBs) and custom-designed artificial reefs (CDARs) in Port Phillip Bay, Victoria, Australia, through comparing a range of condition indices (hepato-somatic, gonado-somatic and relative weight index). Additionally, we investigated mortality rates of new recruits and juveniles of T. caudimaculatus among habitat types. T. caudimaculatus exhibited nine times higher instantaneous mortality rates on RBs than the other two habitat types. Combined with known habitat preference of T. caudimaculatus for RB, this suggests that RBs may act as an ecological trap for this species. V. conspersa exhibited higher fitness on RBs, while T. clarkei fitness proxies were context dependent. Although our results indicate that responses by fishes to artificial habitats are species-, location- and habitat-specific, this is one of the first studies to demonstrate the formation of ecological traps in the marine environment due to proliferation of artificial reefs.
Poorly designed or placed ARs may lead to insufficient positive outcomes or even significant negative impacts on marine communities. Combined with high costs, these effects may lead to reduced social acceptance of new placements and could impede future management and conservation efforts.
Display omitted
•AR performance as fish habitat is species-, location-, habitat- and design-specific•T.caudimaculatus show nine times higher mortality rates on RBs vs other habitats•There is evidence for perceptual trap for some fish species (e.g. T. clarkei)•There is evidence for adaptive habitat selection in V.conspersa•These findings have implications for management and conservation strategies
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