Habitat loss, predation pressure and episodic heat-shocks interact to impact arthropods and photosynthetic functioning of microecosystems.

Habitat loss and fragmentation are two main threats to biodiversity. Forest landscape connectivity can directly affect many ecological processes, such as plant seed dispersal and animal migration, and is an important framework for determining strategic priorities for biodiversity conservation. This study examines the Barluk Mountain Nature Reserve in Xinjiang as a case study to evaluate changes in connectivity at different diffusion distances based on graph theory. Our results showed that Barluk consists predominantly (62%) of small patches (<1 hm2) and a relatively limited number (7%) of large patches (>10 hm2). By simulating a forest loss scenario and assessing the importance of individual patches, we found that large patches played an important role in maintaining connectivity. Further, by calculating the delta number of components (dNC), we found that not all small patches contribute to maintaining connectivity, and small patches (with dNC < 0 and area < 1 hm2) that act as “stepping stones” within large patches should also be prioritized for protection. Therefore, priority identification of patches that contribute the most to connectivity will provide effective forest management strategies, help enhance the functioning of forest ecosystems, and protect fragmented ecosystems.

ABSTRACTA multitude of anthropogenic stressors drive biodiversity loss and alter ecosystem functioning. Freshwaters, which contribute disproportionally to global biodiversity and biogeochemical cycles, are particularly threatened. Although the relationship between biodiversity and ecosystem functions (BEF) is generally well‐established, especially in terrestrial ecosystems, the role of multiple, co‐occurring stressors in modulating the relationship remains unclear. We conducted a meta‐analysis to address this knowledge gap by assessing the effect of multiple stressors on the relationship between taxon richness and four measures of ecosystem function. The relationship was generally positive, with the slope becoming steeper as the number of stressors increased, suggesting that exposure to multiple stressors exacerbates impacts of biodiversity loss on ecosystem function. Multiple stressor effects on both taxon richness and ecosystem functions were largely predictable from individual stressor effects, although antagonistic effects on ecosystem functions emerged in 14% of the considered cases. The type of stressor and ecosystem function, along with taxonomic group, exerted no influence on the BEF relationship, contrary to our expectations. Microbial production and biomass declined most strongly in response to stressors, despite notable variability. Overall, our findings imply that functional consequences of freshwater biodiversity loss are more severe under multifaceted environmental change than previously assumed.

We tested the hypothesis that if the quality or quantity of vegetation in small forest patches is greater than in large patches, then vegetation attributes may contribute to greater densities of white-footed mice (Peromyscus leucopus) in smaller patches. We trapped more mice per hectare in small (range 5–9 ha) than in large (range 110–150 ha) patches, as has been reported by other investigators. The difference appeared to be due primarily to the disproportionately high densities of P. leucopus in the edge habitat of small patches. While the greater edge-to-interior ratio in small patches could contribute to greater overall densities of mice in small patches, we trapped the same relative amount of edge and interior habitats in each of the six study patches. The structural complexity of understory vegetation was much greater in small than in large patches and also in edge than in interior habitats across the six patches. Thus, we trapped the most mice in the most structurally complex vegetation (i.e., edges of small patches). However, while vegetation at the edge of large patches was more complex than in the interior, we did not capture relatively high densities of P. leucopus in edge habitat of large patches. Hence, understory vegetation may differentially influence the distribution of P. leucopus between edge and interior habitats in forest patches of different sizes.

Human land uses have resulted in landscape mosaics with habitat patches that vary in quality. Patch quality (including the abundance of food and the risk of predation) can affect the survival of animals that are sequestered in remnant patches of habitat. Recent investigations of the demography of New England cottontails (Sylvilagus transitionalis) have shown that cottontails on small (resource poor) patches were in poor physical condition (based on body mass) and often foraged at sites with limited cover. This resulted in a higher mortality rate than among rabbits occupying large (resource rich) patches. To gain additional insight into the consequences of habitat fragmentation, we tracked the physiological condition of rabbits occupying small and large patches during winter. The physiological condition of rabbits was determined using the urinary urea nitrogen:creatinine ratio, and the results were compared with similar indices obtained from captive rabbits. Consistent with our expectations, the nitrogen:creatinine ratios indicated that rabbits on small patches were nutrient limited for a longer period than rabbits on large patches. Transmitter-equipped rabbits on small patches had a lower survival rate and died earlier than rabbits on large patches. All mortalities were predator related. Using these data, we developed a simple model that supports the role of "condition-sensitive predation" as a major factor limiting populations of New England cottontails. Our results also demonstrate the utility of sampling physiological condition to provide an index of quality of lagomorph habitat in human-dominated landscapes.

Natural history collections (NHC) worldwide contain vast amount of valuable data that can be used to answer a wide range of questions by exploring biodiversity and natural resources records, having an immense potential to contribute to science, policy making and legislating, and to public scientific awareness. Likewise, the development and increase of global and regional biodiversity digital databases (e.g., Global Biodiversity Information Facility - GBIF; Fauna Europaea; Naturdata, etc.), scientific literature and all digital information regarding biodiversity, ecological areas and climate records comprise a huge amount of primary and processed digital ecological data (DED) accessible globally that can be readily used, at no cost, and integrated to further study e.g. biodiversity changes, ecological processes, natural habitat distribution, prioritizing ecosystem management and conservation actions, etc. Marine invertebrate biodiversity contributes to the structure and stability of ecosystem processes such as productivity, ecological networks, as well as nutrient and biogeochemical cycling having also an economic importance as a food source for local populations. Mangroves and seagrasses encompass ecological and socio-economic relevance as they have a preponderant role in marine and coastal ecosystem biodiversity and functioning providing a vast number of goods and services to local populations. Although generally pristine, mangroves and seagrasses in Africa are extremely vulnerable to the increased migration of rural populations to urban coastal areas and to extreme climate events. As a result, human activities such as construction, agriculture and food harvesting, provoke habitat degradation and biodiversity loss which will have further devastating consequences. The degradation and unsustainable use of these ecosystems have major drawbacks to the elimination of extreme poverty because this is one of the key factors that drive environmental degradation and biodiversity loss. The main goal of this work is to use NHC and digital repositories data (including scientific literature) to assess how biodiversity loss and habitat degradation affect ecosystem functioning and services provided by marine invertebrate communities of mangroves and seagrass meadows in the West and East African coast, using the case study of Mozambique and Príncipe’s Island. These will lead to the construction of a comprehensive dataset, an ecological model and a framework adapted to marine invertebrate biodiversity from Mozambique’s (MZ) and São Tomé and Príncipe’s (STP) mangroves and seagrasses as tools:1) integrate and disseminate marine invertebrate biodiversity data gathered along a spatio-temporal scale; 2) compare marine invertebrate assemblies from pristine and impacted habitats in African countries and predict the progress of these communities to habitat degradation and biodiversity loss; and 3) manage ecosystem functioning and services delivered by marine invertebrate assemblages under anthropogenic and environmental pressure scenarios. Specifically this project intends to: compile and integrate the available information contained in NHC and DED to develop a comprehensive spatio-temporal dataset on marine invertebrate biodiversity (e.g. species, number of individuals, local of occurrence and georeferencing, date of collection/observation), as well as mangroves and seagrasses distribution along the Mozambique’s and Príncipe’s coasts; assess different indexes of invertebrate marine biodiversity, biodiversity and habitat spatio-temporal distribution; develop an ecological network approach to assess the functional links of marine invertebrate communities within the studied habitats, and to refine their role in ecosystem functioning, as well as ecosystem services (ES) provided by marine invertebrates in mangroves and seagrasses from MZ and STP; construct a model to evaluate the ecological responses of mangrove and seagrass invertebrate communities to habitat degradation and biodiversity loss and to predict multi-dimensional (spatial, temporal, and social) trade-offs in local/regional ecosystem services along a spatio-temporal gradient; develop a practical framework to manage and preserve ecosystem functioning and services delivered by mangrove and seagrass marine invertebrates under a global change scenario. compile and integrate the available information contained in NHC and DED to develop a comprehensive spatio-temporal dataset on marine invertebrate biodiversity (e.g. species, number of individuals, local of occurrence and georeferencing, date of collection/observation), as well as mangroves and seagrasses distribution along the Mozambique’s and Príncipe’s coasts; assess different indexes of invertebrate marine biodiversity, biodiversity and habitat spatio-temporal distribution; develop an ecological network approach to assess the functional links of marine invertebrate communities within the studied habitats, and to refine their role in ecosystem functioning, as well as ecosystem services (ES) provided by marine invertebrates in mangroves and seagrasses from MZ and STP; construct a model to evaluate the ecological responses of mangrove and seagrass invertebrate communities to habitat degradation and biodiversity loss and to predict multi-dimensional (spatial, temporal, and social) trade-offs in local/regional ecosystem services along a spatio-temporal gradient; develop a practical framework to manage and preserve ecosystem functioning and services delivered by mangrove and seagrass marine invertebrates under a global change scenario.

The resource concentration hypothesis states that specialized herbivores are more likely to find remain in pure, large, and/or dense stands of their hosts plants. This study examined whether in fact herbivores tended to remain longer in large vs. small patches of host plants and attempts to explain in the results by modelling herbivore movement. Both movement within a patch and emigration of marked Mexican bean beetles (MBBs) were studied by releasing beetles into small (19 plants) and large (61 plants) patches. Beetles left small patches at a faster rate than large patches, but the difference was not statistically significant. A stochastic model that was developed translates individual patterns of MBB movement into population patterns of beetle distribution within a patch, and predicts how this distribution changes with time. Estimating and testing a model on two separate sets of data provides a more rigorous test than applying the model to the data set on which it was developed. The parameters of the model, therefore, were estimated from data collected in the large patches, and the model was tested by comparing the predicted with the observed spatial distribution of beetles in small patches (i.e., a novel situation). Predicted distribution were very similar to the observed distributions; the predicted proportion of insects remaining in a patch at each census time differed from the observed by @<10% on the average. The model predicts that MBB emigration rate should decrease with patch size, confirming the observed trend.

Invasive noxious plants have important impacts on community dynamics and ecosystem functions in grasslands. Since the 1960s, the noxious plant Melica przewalskyi has spread rapidly and formed different size of patches in subalpine meadows of the Qilian Mountains, Northwest China. In this study, the species richness, vegetation structure, and soil water content are investigated from the patch edge to the center in four sizes of M. przewalskyi patches (i.e., small patch, <100 cm in canopy diameter; middle patch, 100–200 cm; large patch, 200–300 cm; and the largest patch, >300 cm). The results show that while the patches grow continuously, the dominant species changes from Stipa krylovii to M. przewalskyi with an increasing trend in plant productivity and decreasing trend in species richness and soil water content. Plant height, density, coverage, and above‐ground biomass of M. przewalskyi population increases from the patch edge to the center in small, middle, and large patches, whereas it is precisely the opposite in the largest patch. Interestingly, soil water content exhibits a decreasing trend from the patch edge to the center in all patches. The results indicate that the rapid spread of M. przewalskyi may well alter vegetation pattern and cause a severe soil moisture deficit, which would further drive the degradation of ecosystem functioning in subalpine meadows.

Anthropogenic stressors are the leading causes of species and biodiversity declines, driving wide-scale ecosystem changes. Additionally, synergistic effects of multiple anthropogenic modifications, including species introductions and habitat alterations, can have complex outcomes for native species. We assessed how a nonnative predator (the Striped Bass Morone saxatilis) and habitat alterations (a small diversion dam and other altered habitats) interacted to influence mortality of native juvenile Chinook Salmon Oncorhynchus tshawytscha during their emigration from the lower Mokelumne River, California. Relative abundance and diet surveys across natural and human-altered habitats were used to assess Striped Bass functional and aggregative responses. Per capita consumption (PCC) of juvenile salmon and behavioral aggregation (CPUE) by Striped Bass at a small diversion dam (Woodbridge Irrigation District Dam [WIDD]) were elevated in comparison with those at other altered and natural habitats (WIDD: PCC = 3.54 juvenile salmon, CPUE = 0.189 Striped Bass/s of electrofishing; other altered habitats: PCC = 0 juvenile salmon, CPUE = 0.0024 Striped Bass/s; natural habitats: PCC = not estimable, CPUE = 0.0003 Striped Bass/s). Increased aggregative and functional predator responses created a localized area of heightened predation at WIDD. At this predation hot spot, we used three approaches (experimental Striped Bass removals, diet energetic analysis, and before–after impact assessment) to estimate Striped Bass consumption at 8–29% of the emigrating juvenile salmon population. Striped Bass PCC rates for juvenile salmon as determined by the three approaches were 0.92% (predator removals), 0.71–1.20% (diet energetic analysis), and 0.96–1.11% (before–after impact assessment). Our results (1) illustrate how the synergistic effect of habitat modification and a nonnative predator can exacerbate the mortality of native juvenile salmon during their emigration and (2) highlight the importance of considering interactions among stressors when planning local management strategies and assessing population-level impacts on salmon. Received February 12, 2015; accepted November 8, 2015 Published online March 30, 2016

Environmental conditions and the spatial arrangement of habitats are thought to play a major role in shaping community assembly during habitat construction and may be key in establishing time lags between habitat establishment and species colonization (colonization credits), and between local species extinction and habitat loss (extinction debts). Despite the importance of soil organisms in ecosystem functioning and their limited dispersal ability, these kinds of shifts in microarthropod communities have rarely been explored. We assessed the roles of the environment and connectivity in soil microarthropod community composition during habitat regeneration in Mediterranean forests. We selected three different forest patches in six study areas: one long‐established (pre‐1956; LONG) control forest patch, and two recent forest patches (post‐1956), one connected (CONN) to and one isolated (ISOL) from the LONG. In each patch, we determined soil temperature, moisture, pH, and fertility and collected soil samples for microarthropod extraction. Our results indicate that the densities of fauna such as oribatid mites and proturans with limited mobility were lower in ISOL than in other forest types; as well, oribatid populations in ISOL were less diverse. Arthropods with greater mobility than the precedent groups, such as collembolans and non‐oribatid mites, were present in lower densities in LONG than in other forest types. Oribatid assemblages in the two recent forest patches were more similar to one another than to those in the LONG. Recent forests were mostly dominated by known pioneer species, while LONG was dominated by the typical species found in well‐developed organic soils. In conclusion, oribatid density and richness had recovered surprisingly well in CONN, more so than in ISOL and to a similar extent as LONG. However, oribatid assemblages in the recent forests are different from those in long‐established forests due to the potential colonization credits and extinction debts triggered by soil development.

Earth’s ecosystems are composed of living organisms and their biotic and abiotic environment. In order to understand the structure and functioning of these ecosystems, ecologists study the interactions of organisms with one another and their environment. The body mass of an organism, its energy demand, and the elemental composition of the body tissue of itself and the resources it depends on are three fundamental aspects of its biology affecting its interactions with other organisms and its environment and, therefore, shaping ecological communities. While a large body of research has established the importance of these drivers, much less is known about how they jointly affect whole-ecosystem processes. This lack of knowledge is partly due to the lack of comprehensive approaches integrating body mass, metabolism and stoichiometry to assess ecosystem structure and functioning in diverse, multitrophic communities. 
\nBody size has fundamental effects on biological rates and ecological interactions and strongly affects living organisms across levels of organisation, from individuals to communities. One major reason for this importance is the effect of body size on an organism’s metabolic rate, the rate of energy uptake, transformation and allocation that, in turn, controls important aspects of its biology and defines the organism’s energy demand. Ecological stoichiometry is concerned with the balance of chemical substances in ecological interactions and thus puts constraints on consumer-resource interactions. As such, these three drivers play a key role in describing and explaining ecological processes. Over the past centuries, the growing human population has dramatically altered Earth’s ecosystems and climate with severe consequences on biodiversity and ecosystem functioning. In this thesis, I provide an important step towards jointly using body mass, metabolism and stoichiometry to assess ecological impacts of changing environmental conditions, as driven by anthropogenic alteration of Earth’s ecosystems.
\nFirst, in Chapter 2, I review previous research on body size with a focus on insects. Initially, I discuss the historical underrepresentation of insects in body-size research and present recent developments toward a better representation of this important animal group enabled by technological improvements and the availability of high-resolution datasets. I discuss the importance of body size for animal movement and behaviour and highlight their importance for the strength and outcome of trophic interactions. Furthermore, I point to the importance of including both size and non-size effects, such as temperature,phylogeny, and stoichiometry, in future ecological experiments and theory. Finally, I emphasise the intersection of allometry effects on behaviour and functional-morphology effects on foraging success as promising directions of future research. 
\nIn Chapter 3, I present whole-community energy flux as a measure of multitrophic ecosystem functioning and test it by assessing ecological consequences of anthropogenic land use on biodiversity and ecosystem functioning in tropical leaf-litter macro-invertebrate communities in forest, jungle rubber, rubber and oil-palm plantations. Combining metabolic theory and food web theory with previous advances in the energetic view of ecosystem processes, I develop a highly flexible measure that takes into account consumer metabolism, assimilation efficiency, network topology, feeding preferences and loss to higher trophic levels. It can now be used to easily assess and compare ecosystem funtioning across communities in different ecosystem types, carrying out a diverse range of functions that would otherwise be difficult to compare. After establishing consistent declines in species richness, animal density, and biomass from forest to oil-palm macro-invertebrate communities, I find that energy flux also decreases and is able to pick up more fine scale differences between trophic groups than, for example, standing stock biomass can detect. Additionally, I use the novel measure of ecosystem functioning to compare biodiversity ecosystem functioning relationships between land-use systems and find the relationship of species richness and energy flux to be steepest in oil-palm communities. However, different trophic guilds exhibit different patterns here. These results highlight the importance of including trophic complexity into future research on community-level processes and additionally emphasise the ability of the developed ecosystem functioning measure to describe community-level patterns based on only few easily obtainable parameters.
\nIn Chapter 4, I combine the energetic approach developed in the previous chapter with ecological stoichiometry theory to assess multitrophic consumer responses to changing resource quality. Specifically, I test for changes in consumer stoichiometry, biomass, and feeding rates in response to increasing resource carbon:nitrogen ratios. By slightly altering the energy flux calculations, I calculate consumer feeding rates based on metabolic demand and assimilation efficiency in response to varying resource stoichiometry without having to measure feeding rates in the field or laboratory. I find that, instead of altering their body stoichiometry or avoiding low-quality resources, detritivore and predator communities exhibit increased feeding rates when exposed to low-quality resources. Interestingly, detritivore species richness significantly decreases with decreasing resource quality, potentially indicating limited ability of consumer species to perform compensatory feeding due to physiological constraints. Thus, my findings suggest compensatory feeding to be much more common across trophic levels than was previously known. Additionally, the method of calculating consumer feeding rates in response to resource quality is a highly useful tool for future research on consumer-resource interactions.
\nFinally, in Chapter 5, I use an information theoretic approach to investigate the effects of basal resource stoichiometry and habitat structure on multitrophic consumer biomass density and diversity. Using this standardised model averaging framework, I am able to directly compare the effects of three habitat structural and seven stoichiometric variables on ten major taxonomic groups and four functional feeding guilds. I find partial support for all specifically tested hypotheses relating certain consumer groups to different stoichiometric and habitat-structural drivers. The tropical macro-invertebrate consumer communities are co-limited by multiple, rather than single, variables with different taxonomic groups controlled by different sets of predictor variables. Interestingly, biomass density and diversity of a given consumer taxon do not always respond homogeneously to a given change in a certain stoichiometric variable, but exhibit a diverse range of response patterns, such as parallel and opposing effects, but also cases where only one of the community characteristics is affected. Consequently, I develop a conceptual framework explaining response patterns found across 80% of the taxonomic consumer groups by assuming a saturating response of biomass, but a hump-shaped response of diversity to increasing availability of a limiting resource. Thus, my findings suggest that tropical consumer communities are co-limited by multiple parameters and highlight the importance of looking at both consumer biomass and diversity when trying to understand community responses to changing environmental conditions. Additionally, I provide a conceptual framework explaining biomass and diversity responses that can now be tested in other ecosystem types.
\nTaken together, in this thesis, I present novel methods and approaches that jointly use body mass, metabolism and stoichiometry to investigate ecological consequences of changing abiotic and biotic conditions. I develop whole-community energy flux and a method for calculating consumer feeding rates in response to resource stoichiometry and test the ability of these tools to describe ecological processes in complex, real-world communities. Furthermore, I integrate metabolic theory and ecological stoichiometry theory to study consumer-resource interactions across trophic levels. By combining ecological theory with state-of-the-art statistical approaches to develop and test novel methods of assessing ecological processes, this thesis provides a significant advance toward understanding and mitigating ecological impacts of anthropogenic alterations of Earth’s ecosystems.

-Forest canopy was partly removed [33% or 66% removal of canopy tree basal area (BA)] from patches of three sizes (0.015, 0.053, 0.196 ha) to determine whether the frequency of five deciduous forest herbs was affected by patch size. Herb frequency, irradiance and woody stem density were recorded after canopy removal and 2 yr later. Irradiance and woody stem density both increased more in large (0.196 ha) patches than in smaller patches (0.015 and 0.053 ha) with 33% and 66% of tree BA removed. In contrast, where 66% of tree BA was removed, the frequency of four herbs increased more in smaller patches than in large patches and the frequency of the fifth herb was unaffected by patch size. Where 33% of tree BA was removed, herb frequency also increased more in smaller patches than in large patches for one herb and by about the same amount in all patches for another herb. The remaining three herbs each increased more in medium-sized patches (0.053 ha) than in small or large patches. These results indicate that the frequency of perennial forest herbs does not increase more in large canopy openings than in smaller openings. Although irradiance was higher in large patches than in smaller patches, woody stem density was greater in large patches as well and competition from more woody plants in large patches may explain why herbs did not increase more in large patches than in smaller patches.

Minimum patch size criteria for habitat protection reflect the conservation principle that a single large (SL) patch of habitat has higher biodiversity than several small (SS) patches of the same total area (SL>SS). Nonetheless, this principle is often incorrect, and biodiversity conservation requires placing more emphasis on protection of large numbers of small patches (SS>SL). We used a global database reporting the abundances of species across hundreds of patches to assess the SL>SS principle in systems where small patches are much smaller than the typical minimum patch size criteria applied for biodiversity conservation (i.e., ∼85% of patches <100ha). The 76 metacommunities we examined included 4401 species in 1190 patches. From each metacommunity, we resampled species-area accumulation curves to evaluate how biodiversity responded to habitat existing as a few large patches or as many small patches. Counter to the SL>SS principle and consistent with previous syntheses, species richness accumulated more rapidly when adding several small patches (45.2% SS>SL vs. 19.9% SL>SS) to reach the same cumulative area, even for the very small patches in our data set. Responses of taxa to habitat fragmentation differed, which suggests that when a given total area of habitat is to be protected, overall biodiversity conservation will be most effective if that habitat is composed of as many small patches as possible, plus a few large ones. Because minimum patch size criteria often require larger patches than the small patches we examined, our results suggest that such criteria hinder efforts to protect biodiversity.

Habitat fragmentation is causing the collapse of seed dispersal interactions and ecosystem functioning. When management and conservation strategies aim to sustain ecosystem functioning of fragmented forests, species' traits and functional performance are critical in guiding decisions. However, to date, we lack a quantitative understanding of the role of frugivores' body size and dispersal ability in ecosystem sustainability among fragmented forests. Focusing on avian frugivory and seed dispersal in a multi-island setting, we address the data gap by recording more than 20,000 frugivory events in an artificial insular fragmented landscape constructed in 1959 and nearby unfragmented forests on the mainland. We show that large-bodied and dispersal-limited frugivorous birds are largely confined to large islands and the unfragmented mainland, whereas on small islands, small-bodied and highly mobile birds predominantly engage in frugivory interactions. The plant-frugivore meta-network exhibits a distinct compartmentalization, driven by island area and bird mobility. Birds with smaller size and greater mobility have higher topological importance, and the presence of small-bodied birds significantly enhances meta-network robustness. These results suggest that among insular fragmented forests where frugivory interactions are degraded, small-bodied and highly mobile birds disproportionately contribute to meta-community cohesion and ecosystem functioning because of the lack of large-bodied and dispersal-limited birds. We thus advocate for the restoration of landscapes to facilitate seed dispersal and functional connectivity, ensuring the presence of large patches along with small patches as stepping-stones. Meanwhile, we recommend prioritizing conservation on small-bodied and highly mobile birds in fragmented landscapes, a subset of underappreciated species that yet play crucial roles in ecosystem functioning.

We examined physical condition, niche dimensions, and survival of New England cottontails (Sylvilagus transitionalis) that occupied 21 habitat patches of different sizes during winter. Rabbits on small patches (≤2.5 ha) were predominantly males, and both sexes had lower body mass than individuals on large patches (≥5.0 ha). Niche indices (β, where β ranges from 0 to 1. and values approaching 1 indicate generalized resource use) of habitat use revealed that rabbits on small patches used a greater variety of microhabitats (based on understory stem density: βs, and proximity to cover: βc) than rabbits occupying large patches (βs=0.65, βc=0.66). Rabbits on small patches also consumed low quality forage more often and fed at sites farther from escape cover than rabbits on large patches. There were no significant correlations between rabbit densities and niche dimensions. Niche expansion was not a result of compertitive release or relaxation of predator pressure. Rabbits on small patches apparently modified their niche dimensions in response to resource limitations. This response included occupying sites with limited understory cover that apparently resulted in rabbits on small patches having a lower survival rate (0.35) than rabbits on large patches (0.69) during a 10-week monitoring period. Skewed sex ratios and low survival rates among rabbits on small patches suggest that these habitats act as sinks to dispersing, juveniles from large (source) patches. As a result, local populations of New England cottontails may become vulnerable to extinction if larte patches of habitat are not maintained.

Cumulative human impacts across the world's oceans are considerable. We therefore examined a single model taxonomic group, the penguins (Spheniscidae), to explore how marine species and communities might be at risk of decline or extinction in the southern hemisphere. We sought to determine the most important threats to penguins and to suggest means to mitigate these threats. Our review has relevance to other taxonomic groups in the southern hemisphere and in northern latitudes, where human impacts are greater. Our review was based on an expert assessment and literature review of all 18 penguin species; 49 scientists contributed to the process. For each penguin species, we considered their range and distribution, population trends, and main anthropogenic threats over the past approximately 250 years. These threats were harvesting adults for oil, skin, and feathers and as bait for crab and rock lobster fisheries; harvesting of eggs; terrestrial habitat degradation; marine pollution; fisheries bycatch and resource competition; environmental variability and climate change; and toxic algal poisoning and disease. Habitat loss, pollution, and fishing, all factors humans can readily mitigate, remain the primary threats for penguin species. Their future resilience to further climate change impacts will almost certainly depend on addressing current threats to existing habitat degradation on land and at sea. We suggest protection of breeding habitat, linked to the designation of appropriately scaled marine reserves, including in the High Seas, will be critical for the future conservation of penguins. However, large-scale conservation zones are not always practical or politically feasible and other ecosystem-based management methods that include spatial zoning, bycatch mitigation, and robust harvest control must be developed to maintain marine biodiversity and ensure that ecosystem functioning is maintained across a variety of scales.