A multispecies test of source–sink indicators to prioritize habitat for declining populations

For species at risk of decline or extinction in source–sink systems, sources are an obvious target for habitat protection actions. However, the way in which source habitats are identified and prioritized can reduce the effectiveness of conservation actions. Although sources and sinks are conceptually defined using both demographic and movement criteria, simplifications are often required in systems with limited data. To assess the conservation outcomes of alternative source metrics and resulting prioritizations, we simulated population dynamics and extinction risk for 3 endangered species. Using empirically based habitat population models, we linked habitat maps with measured site‐ or habitat‐specific demographic conditions, movement abilities, and behaviors. We calculated source–sink metrics over a range of periods of data collection and prioritized consistently high‐output sources for conservation. We then tested whether prioritized patches identified the habitats that most affected persistence by removing them and measuring the population response. Conservation decisions based on different source–sink metrics and durations of data collection affected species persistence. Shorter time series obscured the ability of metrics to identify influential habitats, particularly in temporally variable and slowly declining populations. Data‐rich source–sink metrics that included both demography and movement information did not always identify the habitats with the greatest influence on extinction risk. In some declining populations, patch abundance better predicted influential habitats for short‐term regional persistence. Because source–sink metrics (i.e., births minus deaths; births and immigrations minus deaths and emigration) describe net population conditions and cancel out gross population counts, they may not adequately identify influential habitats in declining populations. For many nonequilibrium populations, new metrics that maintain the counts of individual births, deaths, and movement may provide additional insight into habitats that most influence persistence.     

Nutritional exchange in a tropical tripartite symbiosis: direct evidence for the transfer of nutrients from anemonefish to host anemone and zooxanthellae

The relationship between anemones and anemonefishes is an oft-cited and endearing example of a mutualistic symbiosis. Current research on mutualistic symbioses suggests these relationships are more commonplace and have greater importance at the ecosystem level on nutrient dynamics and evolutionary processes than previously thought. Using stable isotopes ¹⁵N and ¹³C, both field and laboratory experiments were designed to investigate whether nutrient transfer from two species of resident anemonefishes (Amphiprion perideraion and A. clarkii) to host anemones (Heteractis crispa) occurs. Mass spectroscopy indicated that both ¹⁵N and ¹³C were significantly elevated in the tissues of anemonefishes and in both host anemone and zooxanthellae fractions. These experiments provide the first direct empirical evidence of nitrogen and carbon transfer from resident anemonefishes to host anemones and endosymbiotic zooxanthellae. Such transfer of elements within this intriguing tripartite association underscores the central role that nutrient dynamics contributes to the evolutionary processes of these marine symbioses.     

Effects of Landscape Composition and Wetland Fragmentation on Frog and Toad Abundance and Species Richness in Iowa and Wisconsin, U.S.A.

Abstract: Management of amphibian populations to reverse recent declines will require defining high-quality habitat for individual species or groups of species, followed by efforts to retain or restore these habitats on the landscape. We examined landscape-level habitat relationships for frogs and toads by measuring associations between relative abundance and species richness based on survey data derived from anuran calls and features of land-cover maps for Iowa and Wisconsin. The most consistent result across all anuran guilds was a negative association with the presence of urban land. Upland and wetland forests and emergent wetlands tended to be positively associated with anurans. Landscape metrics that represent edges and patch diversity also had generally positive associations, indicating that anurans benefit from a complex of habitats that include wetlands. In Iowa the most significant associations with relative abundance were the length of the edge between wetland and forest ( positive) and the presence of urban land (negative). In Wisconsin the two most significant associations with relative abundance were forest area and agricultural area ( both positive). Anurans had positive associations with agriculture in Wisconsin but not in Iowa. Remnant forest patches in agricultural landscapes may be providing refuges for some anuran species. Differences in anuran associations with deep water and permanent wetlands between the two states suggest opportunities for management action. Large-scale maps can contribute to predictive models of amphibian habitat use, but water quality and vegetation information collected from individual wetlands will likely be needed to strengthen those predictions. Landscape habitat analyses provide a framework for future experimental and intensive research on specific factors affecting the health of anurans.     

Multispecies genetic objectives in spatial conservation planning

Growing threats to biodiversity and global alteration of habitats and species distributions make it increasingly necessary to consider evolutionary patterns in conservation decision making. Yet, there is no clear‐cut guidance on how genetic features can be incorporated into conservation‐planning processes, despite multiple molecular markers and several genetic metrics for each marker type to choose from. Genetic patterns differ between species, but the potential tradeoffs among genetic objectives for multiple species in conservation planning are currently understudied. We compared spatial conservation prioritizations derived from 2 metrics of genetic diversity (nucleotide and haplotype diversity) and 2 metrics of genetic isolation (private haplotypes and local genetic differentiation) in mitochondrial DNA of 5 marine species. We compared outcomes of conservation plans based only on habitat representation with plans based on genetic data and habitat representation. Fewer priority areas were selected for conservation plans based solely on habitat representation than on plans that included habitat and genetic data. All 4 genetic metrics selected approximately similar conservation‐priority areas, which is likely a result of prioritizing genetic patterns across a genetically diverse array of species. Largely, our results suggest that multispecies genetic conservation objectives are vital to creating protected‐area networks that appropriately preserve community‐level evolutionary patterns.     

Nemertean,copepod, and amphipod symbionts of the dimorphic ascidian Pyura stolonifera near Melbourne,Australia: specificities to host morphs,and factors affecting prevalences

On the central coast of Victoria. Australia, the dimorphic ascidian Pyura stolonifera (Heller, 1878) harbors three endosymbionts: the nemertean Gononemertes australiensis Gibson, 1974, the copepod Doropygus pulex (Thorell, 1859), and the amphipod Paraleucothoe novaehollandiae (Haswell, 1880). The specificities of these symbionts to two host colour morphs were studied during 1989 to 1991 as part of a multidisciplinary investigation aimed at determining whether the two morphs are genetically distinct. Distributional surveys revealed that nemerteans and copepods occur only in yellow and brown ascidians, respectively, and that amphipods live in both forms. These specificities held true not only when the two morphs were in allopatry, but also in sympatry. These observations, especially the sympatric data, suggest that the two host morphs might be genetically distinct. For example, the two morphs might have different genetically encoded internal milieus that favour the survival of nemerteans in yellow ascidians, and copepods in brown hosts. In transplant experiments, which involved moving ascidian morphs within and between habitats, the wrong symbionts never colonised the wrong hosts. These results, although consistent with the hypothesis of genetic maintenance of specificity, were deemed inconclusive because of the difficulty of establishing reliable controls (i.e. vacant hosts). The relationships between symbiont prevalences and several factors (season, year, site within host, host individual, host habitat, host size/age, host breeding condition, and co-occurrence of other symbiont species) were also analysed. Both simple (e.g. greater prevalences for large hosts) and complex (e.g. prevalence x season x gonad state of host) interactions were detected for all three symbiont species. These are among the very few quantitative analyses of factors affecting prevalences of ascidicolous nemerteans and amphipods. The present report identifies one of very few definite nemertean-ascidian symbioses. Since no differences in gross condition were ever noticed between occupied and vacant hosts, it is suggested that all three symbionts are commensals rather than parasites or mutuals.     

Impact of host community composition on Lyme disease risk

The drivers of variable disease risk in complex multi-host disease systems have proved very difficult to identify. Here we test a model that explains the entomological risk of Lyme disease (LD) in terms of host community composition. The model was parameterized in a continuous forest tract at the Cary Institute of Ecosystem Studies (formerly the Institute of Ecosystem Studies) in New York State, U.S.A. We report the results of continuing longitudinal observations (10 years) at the Cary Institute, and of a shorter-term study conducted in forest fragments in LD endemic areas of Connecticut, New Jersey, and New York, USA. Model predictions were significantly correlated with the observed nymphal infection prevalence (NIP) in both studies, although the relationship was stronger in the longer-term Cary Institute study. Species richness was negatively, albeit weakly, correlated with NIP (logistic regression), and there was no relationship between the Shannon diversity index (H') and NIP. Although these results suggest that LD risk is in fact dependent on host diversity, the relationship relies explicitly on the identities and frequencies of host species such that conventional uses of the term biodiversity (i.e., richness, evenness, H') are less appropriate than are metrics that include species identity. This underscores the importance of constructing interaction webs for vertebrates and exploring the direct and indirect effects of anthropogenic stressors on host community composition.     

Persistence,morphology, and nutritional state of a gastropod hosted bacterial symbiosis in different levels of hydrothermal vent flux

The limpet, Lepetodrilus fucensis McLean, is found in prominent stacks around hydrothermal vents on the Juan de Fuca Ridge. L. fucensis hosts a filamentous episymbiont on its gill lamellae that may be ingested directly by the gill epithelium. To assess the persistence of this symbiosis I used microscopy to examine the gills of L. fucensis from sites representing its geographic range and different habitats. The symbiosis is present on all the specimens examined in this study, including both sexes and a range of juvenile and adult sizes. Next, I aimed to determine if patterns in bacterial abundance, host condition, and gill morphology support the hypotheses that the bacteria are chemoautotrophic and provide limpets with a food resource. To do so, I compared specimens from high and low flux locations at multiple vents. My results support the above hypotheses: (1) gill bacteria are significantly less abundant in low flux where the concentrations of reduced chemicals (for chemoautotrophy) are negligible, (2) low flux specimens have remarkably poor tissue condition, and (3) the lamellae of high flux limpets have greater surface area: the blood space and bacteria-hosting epithelium are deeper and have more folds than low flux lamellae, modifications that support higher symbiont abundances. I next asked if the morphology of the lamellae could change. To test this, I moved high flux limpets away from a vent and after 1 year the lamellar depth and shape of the transplanted specimens resembled low flux gills. Last, I was interested in whether bacterial digestion by the gill epithelium is a significant feeding mechanism. As bacteria-like cells are rarely apparent in lysosomes of the gill epithelium, I predicted that lysosome number would be unrelated to bacterial abundance. My data support this prediction, suggesting that digestion of bacteria by the gill epithelium probably contributes only minimally to the limpet’s nutrition. Overall, the persistence and morphology of the L. fucensis gill symbiosis relates to the intensity of vent flux and indicates that specimens from a variety of habitats may be necessary to characterize the morphological variability of gill-hosted symbioses in other molluscs.     

Assessing sensitivities of marine areas to stressors based on biological traits

Analysis of the biological traits (e.g., feeding mode and size) that control how organisms interact with their environment has been used to identify environmental drivers of, or impacts on, species and to explain the importance of biodiversity loss. Biological trait analysis (BTA) could also be used within risk-assessment frameworks or in conservation planning if one understands the groups of traits that predict the sensitivity of habitats or communities to specific human activities. Deriving sensitivities from BTA should extend sensitivity predictions to a variety of habitats, especially those in which it would be difficult to conduct experiments (e.g., due to depth or risk to human life) and to scales beyond the norm of most experiments. We used data on epibenthos, collected via video along transects at 27 sites in a relatively pristine region of the seafloor, to determine scales of natural spatial variability of derived sensitivities and the degree to which predictions of sensitivity differed among 3 stressors (extraction of species, sedimentation, and suspended sediments) or were affected by underlying community compositions. We used 3 metrics (weighted abundance, abundance of highly sensitive species, and number of highly sensitive species) to derive sensitivity to these stressors and simulated the ability of these metrics to detect a range of stressor intensities. Regardless of spatial patterns of sensitivities across the sampled area, BTA distinguished differences in sensitivity to different stressors. The BTA also successfully separated differences in community composition from differences in sensitivity to stressors. Conversely, the 3 metrics differed widely in their ability to detect simulated impacts and likely reflect underlying ecological processes, suggesting that use of multiple metrics would be informative for spatial planning and allocating conservation priorities. Our results suggest BTA could be used as a first step in strategic prioritization of protected areas and as an underlying layer for spatial planning.     

Incorporating putatively neutral and adaptive genomic data into marine conservation planning

The availability of genomic data for an increasing number of species makes it possible to incorporate evolutionary processes into conservation plans. Recent studies show how genetic data can inform spatial conservation prioritization (SCP), but they focus on metrics of diversity and distinctness derived primarily from neutral genetic data sets. Identifying adaptive genetic markers can provide important information regarding the capacity for populations to adapt to environmental change. Yet, the effect of including metrics based on adaptive genomic data into SCP in comparison to more widely used neutral genetic metrics has not been explored. We used existing genomic data on a commercially exploited species, the giant California sea cucumber (Parastichopus californicus), to perform SCP for the coastal region of British Columbia (BC), Canada. Using a RAD-seq data set for 717 P. californicus individuals across 24 sampling locations, we identified putatively adaptive (i.e., candidate) single nucleotide polymorphisms (SNPs) based on genotype–environment associations with seafloor temperature. We calculated various metrics for both neutral and candidate SNPs and compared SCP outcomes with independent metrics and combinations of metrics. Priority areas varied depending on whether neutral or candidate SNPs were used and on the specific metric used. For example, targeting sites with a high frequency of warm-temperature-associated alleles to support persistence under future warming prioritized areas in the southern coastal region. In contrast, targeting sites with high expected heterozygosity at candidate loci to support persistence under future environmental uncertainty prioritized areas in the north. When combining metrics, all scenarios generated intermediate solutions, protecting sites that span latitudinal and thermal gradients. Our results demonstrate that distinguishing between neutral and adaptive markers can affect conservation solutions and emphasize the importance of defining objectives when choosing among various genomic metrics for SCP.     

丛枝菌根对盐胁迫的响应及其与宿主植物的互作

丛枝菌根真菌(Arbuscular Mycorrhizae Fungi,AMF)作为陆地生态系统的组成部分之一,在促进宿主植物对土壤养分和水分的吸收、提高植物生物量生产、调节种群和群落的结构、维持生态系统的稳定性等方面发挥了重要作用。其中,盐渍化是自然生态系统中广泛存在的一种胁迫生境条件,全球盐渍化土地约占耕地总面积的10%,因而探讨AM菌根在此胁迫生境下对宿主植物生长的影响具有重要意义。从以下几个方面,围绕盐胁迫条件、AM菌根和宿主植物三者之间的关系对当前国际上相关领域的研究进展进行了综述:1)AM真菌对盐胁迫的响应,包括菌根共生体形成、菌根侵染率、AM真菌的分布、菌丝体生长发育、孢子的形成和分布等;2)盐胁迫条件下AM菌根对宿主植物的效应,包括AM菌根促进宿主植物对P、N等元素的吸收、降低植物体内Na 的含量、提高光合作用能力,进而提高植物的生物量和对植物的群落结构产生影响等;3)AM菌根提高宿主植物耐盐性的机理,分别从植物根系形态的改变、水分吸收能力的加强、细胞内营养物质的平衡,以及细胞生理代谢的调节等方面对AM菌根促进植物抗盐性的机理进行了剖析。     

Seasonal water stress tolerance and habitat associations within four neotropical tree genera

We investigated the relationship between habitat association and physiological performance in four congeneric species pairs exhibiting contrasting distributions between seasonally flooded and terra firme habitats in lowland tropical rain forests of French Guiana, including Virola and Iryanthera (Myristicaceae), Symphonia (Clusiaceae), and Eperua (Caesalpiniaceae). We analyzed 10-year data sets of mapped and measured saplings (stems >150 cm in height and <10 cm diameter at breast height [dbh]) and trees (stems > or =10 cm dbh) across 37.5 ha of permanent plots covering a 300-ha zone, within which seasonally flooded areas (where the water table never descends below 1 m) have been mapped. Additionally, we tested the response of growth, survival, and leaf functional traits of these species to drought and flood stress in a controlled experiment. We tested for habitat preference using a modification of the torus translation method. Strong contrasting associations of the species pairs of Iryanthera, Virola, and Symphonia were observed at the sapling stage, and these associations strengthened for the tree stage. Neither species of Eperua was significantly associated with flooded habitats at the sapling stage, but E. falcata was significantly and positively associated with flooded forests at the tree stage, and trees of E. grandiflora were found almost exclusively in nonflooded habitats. Differential performance provided limited explanatory support for the observed habitat associations, with only congeners of Iryanthera exhibiting divergent sapling survival and tree growth. Seedlings of species associated with flooded forest tended to have higher photosynthetic capacity than their congeners at field capacity. In addition, they tended to have the largest reductions in leaf gas exchange and growth rate in response to experimental drought stress and the least reductions in response to experimental inundation. The corroboration of habitat association with differences in functional traits and, to a lesser extent, measures of performance provides an explanation for the regional coexistence of these species pairs. We suggest that specialization to seasonally flooded habitats may explain patterns of adaptive radiation in many tropical tree genera and thereby provide a substantial contribution to regional tree diversity.     

The patchiness of epifoliar fungi in tropical forests: host range, host abundance, and environment

Fungal symbioses affect the diversity, dynamics, and spatial patterns of trees in tropical forests. Their ecological importance is partly driven by their inherent patchiness. We used epifoliar fungi, a guild of common, benign, obligate, fungal symbionts of plants, as a model system to evaluate the relative importance of host phylogeny, host relative abundance, and microclimate on the three-dimensional distribution of plant-fungus symbioses. In parallel studies in rainforests in Panama and Australia, most epifoliar fungi were able to colonize several plant lineages but showed significant host preferences within the local plant community. More closely related plant species were not more likely to share fungal symbionts. Instead, fungal species were more likely to be shared by more abundant hosts, which supported a greater number and diversity of fungi. Environmental conditions strongly affected spatial distributions, with sites in the dark understory 2.5- to fourfold more likely to have epifoliar fungi than in the exposed forest canopy. In the understory, fungal incidence increased with canopy openness. Canopy trees supported only a subset of the fungal symbionts found in the understory, suggesting that adult trees are not reservoirs of these fungal symbionts for understory juveniles.     

Currents connecting communities: nearshore community similarity and ocean circulation

Understanding the mechanisms that create spatial heterogeneity in species distributions is fundamental to ecology. For nearshore marine systems, most species have a pelagic larval stage where dispersal is strongly influenced by patterns of ocean circulation. Concomitantly, nearshore habitats and the local environment are also influenced by ocean circulation. Because of the shared dependence on the seascape, distinguishing the relative importance of the local environment from regional patterns of dispersal for community structure remains a challenge. Here, we quantify the "oceanographic distance" and "oceanographic asymmetry" between nearshore sites using ocean circulation modeling results. These novel metrics quantify spatial separation based on realistic patterns of ocean circulation, and we explore their explanatory power for intertidal and subtidal community similarity in the Southern California Bight. We find that these metrics show significant correspondence with patterns of community similarity and that their combined explanatory power exceeds that of the thermal structure of the domain. Our approach identifies the unique influence of ocean circulation on community structure and provides evidence for oceanographically mediated dispersal limitation in nearshore marine communities.     

Life-history strategies of plant pathogens: distribution patterns and phylogenetic analysis

Here we analyze herbarium records, surveys, and studies of fungal plant pathogens in tropical natural systems in order to establish a framework to study plant-pathogen interactions from a life-history perspective. We looked at how life-history traits of pathogens and their host plants affect the distribution of pathogens in different tropical habitats, and the importance of host phylogeny in determining the habitat associations of obligate fungal pathogens. Our study reveals that plant-pathogen interactions are prevalent and widespread in the tropics. Phylogenetic analysis of the distribution of obligate pathogens among plant families did not suggest a strong overall pattern of higher-level host phylogeny in pathogen host range, except that smut pathogens are particularly dominant on Poaceae and Asteraceae, and rusts are most common on Fabaceae, families that dominate disturbed areas in the tropics.     

Species richness patterns along environmental gradients in island land molluscan fauna

The relationship between species richness and environmental variables may change depending on habitat structure, dispersal ability, species mixing, and community adaptation to the environment. It is crucial to know how these factors regulate the environment-diversity relationship. The land molluscan fauna of the Ogasawara Islands in the West Pacific is an excellent model system to address this question because of the high species endemicity (> 90%), small area, and simple habitat structure of the islands. I examined relationships among indigenous species composition, richness, and habitat condition, and especially productivity and forest moisture on the island of Anijima. Two major communities of snails could be distinguished by detrended correspondence analysis (DCA): one group dominated in a moist habitat with high productivity, and the other group dominated in a dry habitat with low productivity. However, species richness became highest at the intermediate condition between the habitats in which the two snail communities were dominant, so that species richness showed a hump-shaped relationship with moisture and productivity. In contrast, the species richness of the snail community in the moist habitat showed a monotonically positive correlation, and that in the dry habitat showed a monotonically negative correlation with moisture and productivity. Thus, the greater species richness in intermediate moisture and productivity resulted from the ecotone effect or community overlap at the transitional areas, where faunas with different ecologies can meet in a single site. These findings suggest that hump-shaped productivity-diversity relationships in land Mollusca would reflect the ecotone effect as a result of the mixing of species adapted to either fertile habitats or sterile habitats.     

Diversity, ecosystem function, and stability of parasitoid-host interactions across a tropical habitat gradient

Global biodiversity decline has prompted great interest in the effects of habitat modification and diversity on the functioning and stability of ecosystem processes. However, the applicability of previous modeled or mesocosm community studies to real diverse communities in different habitats remains ambiguous. We exposed standardized nesting resources for naturally occurring communities of cavity-nesting bees and wasps and their parasitoids in coastal Ecuador, to test the effects of host and parasitoid diversity on an ecosystem function (parasitism rates) and temporal variability in this function. In accordance with predictions of complementary host use, parasitism rates increased with increasing diversity, not simply abundance, of parasitoids. In contrast, parasitism decreased with increasing host diversity, possibly due to positive prey interactions or increased probability of selecting unpalatable species. Temporal variability in parasitism was lower in plots with high mean parasitoid diversity and higher in plots with temporally variable host and parasitoid diversity. These effects of diversity on parasitism and temporal stability in parasitism rates were sufficiently strong to be visible across five different habitat types, representing a gradient of increasing anthropogenic modification. Habitat type did not directly affect parasitism rates, but host and parasitoid diversity and abundance were higher in highly modified habitats, and parasitoid diversity was positively correlated with rates of parasitism. The slope of the richness-parasitism relationship did not vary significantly across habitats, although that for Simpson's diversity was significant only in rice and pasture. We also show that pooling data over long time periods, as in previous studies, can blur the effect of diversity on parasitism rates, and the appropriate spatiotemporal scale of study must be considered.     

Evaluating Children's Conservation Biology Learning at the Zoo

Millions of children visit zoos every year with parents or schools to encounter wildlife firsthand. Public conservation education is a requirement for membership in professional zoo associations. However, in recent years zoos have been criticized for failing to educate the public on conservation issues and related biological concepts, such as animal adaptation to habitats. I used matched pre‐ and postvisit mixed methods questionnaires to investigate the educational value of zoo visits for children aged 7–15 years. The questionnaires gathered qualitative data from these individuals, including zoo‐related thoughts and an annotated drawing of a habitat. A content analysis of these qualitative data produced the quantitative data reported in this article. I evaluated the relative learning outcomes of educator‐guided and unguided zoo visits at London Zoo, both in terms of learning about conservation biology (measured by annotated drawings) and changing attitudes toward wildlife conservation (measured using thought‐listing data). Forty‐one percent of educator‐guided visits and 34% of unguided visits resulted in conservation biology‐related learning. Negative changes in children's understanding of animals and their habitats were more prevalent in unguided zoo visits. Overall, my results show the potential educational value of visiting zoos for children. However, they also suggest that zoos’ standard unguided interpretive materials are insufficient for achieving the best outcomes for visiting children. These results support a theoretical model of conservation biology learning that frames conservation educators as toolmakers who develop conceptual resources to enhance children's understanding of science. Evaluación del Aprendizaje de Biología de la Conservación por Niños en el Zoológico Jensen