Differences In Species Ecology Research Articles

Root-centric β diversity reveals functional homogeneity while phylogenetic heterogeneity in a subtropical forest.

Root-centric studies have revealed fast taxonomic turnover across root neighborhoods, but how such turnover is accompanied by changes in species functions and phylogeny (i.e., β diversity) remains largely unknown. As β diversity can reflect the degree of community-wide biotic homogenization, such information is crucial for better inference of below-ground assembly rules, community structuring, and ecosystem processes. We collected 2480 root segments from 625 0-30 cm soil profiles in a subtropical forest in China. Root segments were identified into 138 species with DNA-barcoding with six root morphological and architectural traits measured per species. By using the mean pairwise (Dpw ) and mean nearest neighbor distance (Dnn ) to quantify species ecological differences, we first tested the non-random functional and phylogenetic turnover of root neighborhoods that would lend more support to deterministic over stochastic community assembly processes. Additionally, we examined the distance-decay pattern of β diversity, and finally partitioned β diversity into geographical and environmental components to infer their potential drivers of environmental filtering, dispersal limitation, and biotic interactions. We found that functional turnover was often lower than expected given the taxonomic turnover, whereas phylogenetic turnover was often higher than expected. Phylogenetic Dpw (e.g., interfamily species) turnover exhibited a distance-decay pattern, likely reflecting limited dispersal or abiotic filtering that leads to the spatial aggregation of specific plant lineages. Conversely, both functional and phylogenetic Dnn (e.g., intrageneric species) exhibited an inverted distance-decay pattern, likely reflecting strong biotic interactions among spatially and phylogenetically close species leading to phylogenetic and functional divergence. While the spatial distance was generally a better predictor of β diversity than environmental distance, the joint effect of environmental and spatial distance usually overrode their respective pure effects. These findings suggest that root neighborhood functional homogeneity may somewhat increase forest resilience after disturbance by exhibiting an insurance effect. Likewise, root neighborhood phylogenetic heterogeneity may enhance plant fitness by hindering the transmission of host-specific pathogens through root networks or by promoting interspecific niche complementarity not captured by species functions. Our study highlights the potential role of root-centric β diversity in mediating community structures and functions largely ignored in previous studies.

Partitioning and integrating of plant traits and phylogeny in assessing diversity along secondary forest succession in Loess Plateau of China.

Assessing plant diversity during community succession based on plant trait and phylogenetic features within a community (alpha scale) and among communities (beta scale) could improve our understanding of community succession mechanism. However, whether changes of community functional diversity at alpha and beta scale are structured by different traits and whether integrating plant traits and phylogeny can enhance the ability in detecting diversity pattern have not been studied in detail. Thirty plots representing different successional stages were established on the Loess Plateau of China and 15 functional traits were measured for all coexisting species. We first analyzed the functional alpha and beta diversity along succession by decomposing species trait into alpha and beta components and then integrated key traits with phylogenetic information to explore their roles in shaping species turnover during community succession. We found that functional alpha diversity increased along successional stages and was structured by morphological traits, while beta diversity decreased during succession and was more structured by stoichiometry traits. Phylogenetic alpha diversity showed congruent pattern with functional alpha diversity because of phylogenetic conservation of trait alpha components (variation within community), while beta diversity showed incongruent pattern due to phylogenetic randomness of trait beta components (variation among communities). Furthermore, only integrating relatively conserved traits (plant height and seed mass) and phylogenetic information can raise the detecting ability in assessing diversity change. Overall, our results reveal the increasing niche differentiation within community and functional convergence among communities with succession process, indicating the importance of matching traits with scale in studying community functional diversity and the asymmetry of traits and phylogeny in reflecting species ecological differences under long-term selection pressures.

Year-round water management for desert bighorn sheep corresponds with visits by predators not bighorn sheep.

Managing water (e.g., catchments) to increase the abundance and distribution of game is popular in arid regions, especially throughout the southwest United States, where biologists often manage water year-round for desert bighorn sheep (Ovis canadensis nelsoni). Bighorn may visit water when predators (e.g., mountain lions [Puma concolor], coyotes [Canis latrans]) do not, suggesting that differences in species ecology or their surface water requirements influence visit timing. Alternatively, visits by desert bighorn sheep and predators may align. The former outcome identifies opportunities to improve water management by providing water when desert bighorn sheep visit most, which hypothetically may reduce predator presence, range expansion and predation, thereby supporting objectives to increase sheep abundances. Since advancing water management hinges on understanding the patterns of species visits, we identified when these three species and mule deer (Odocoileus hemionus) visited managed waters in three North American deserts (Chihuahuan, Sonoran, Mojave). We unraveled the ecological basis describing why visits occurred by associating species visits with four weather variables using multi-site, multi-species models within a Bayesian hierarchical framework (3.4 million images; 105 locations; 7/2009-12/2016). Desert bighorn sheep concentrated visits to water within 4-5 contiguous months. Mountain lions visited water essentially year-round within all deserts. Higher maximum temperature influenced visits to water, especially for desert bighorn sheep. Less long-term precipitation (prior 6-week total) raised visits for all species, and influenced mountain lion visits 3-20 times more than mule deer and 3-37 times more than sheep visits. Visits to water by prey were inconsistent predictors of visits to water by mountain lions. Our results suggest improvements to water management by aligning water provision with the patterns and ecological explanations of desert bighorn sheep visits. We exemplify a scientific approach to water management for enhancing stewardship of desert mammals, be it the southwest United States or arid regions elsewhere.

Do traits and phylogeny support congruent community diversity patterns and assembly inferences?

Abstract It is now commonplace in community ecology to assess patterns of phylogenetic or functional diversity in order to inform our understanding of the assembly mechanisms that structure communities. While both phylogenetic and functional approaches have been used in conceptually similar ways, it is not clear if they both in fact reveal similar community diversity patterns or support similar inferences. We review studies that use both measures to determine the degree to which they support congruent patterns and inferences about communities. We performed a literature review with 188 analyses from 79 published papers that compared some facet of phylogenetic (PD) and functional diversity (FD) in community ecology. These studies generally report four main cases in which phylogenetic and functional information are used together in community analyses, to determine if: (a) there were phylogenetic signals in the measured traits in communities; (b) PD and FD were correlated with one another; (c) standardized PD and FD measures similarly revealed patterns of community over‐ or under‐dispersion; and (d) PD and FD were both related to other explanatory variables (e.g. elevation) similarly. We found that the vast majority of studies found both strong phylogenetic signals in their traits and positive correlations of PD and FD measures across sites. However, and surprisingly, we found substantial incongruencies for the other tests. Phylogenetic and functional dispersion patterns were congruent only about half the time. Specifically, when communities were phylogenetically over‐dispersed, these same communities were more likely to be functionally under‐dispersed. Similarly, we found that phylogenetic and functional relationships with independent predictors were incongruent in about half of the analyses. Synthesis. Phylogenetic signal tests and PD–FD correlations appear to strongly support the congruence between traits and phylogeny. It is surprising that strong phylogenetic signals appeared so ubiquitous given that ecological studies often analyse phylogenetically incomplete sets of species that have undergone ecological sorting. Despite the largely congruent findings based on phylogenetic signal tests and PD‐FD correlations, we found substantial incongruencies when researchers assessed either dispersion patterns or relationships with independent predictors. We discuss a number of potential ecological, evolutionary and methodological reasons for these incongruencies. Phylogenetic and functional information might reflect species ecological differences unequally with phylogenies better reflecting multivariate conserved elements of ecological similarity, and single traits better able to capture recent divergence, and both elements influence ecological patterns.

Antarctic Futures: An Assessment of Climate-Driven Changes in Ecosystem Structure, Function, and Service Provisioning in the Southern Ocean

In this article, we analyze the impacts of climate change on Antarctic marine ecosystems. Observations demonstrate large-scale changes in the physical variables and circulation of the Southern Ocean driven by warming, stratospheric ozone depletion, and a positive Southern Annular Mode. Alterations in the physical environment are driving change through all levels of Antarctic marine food webs, which differ regionally. The distributions of key species, such as Antarctic krill, are also changing. Differential responses among predators reflect differences in species ecology. The impacts of climate change on Antarctic biodiversity will likely vary for different communities and depend on species range. Coastal communities and those of sub-Antarctic islands, especially range-restricted endemic communities, will likely suffer the greatest negative consequences of climate change. Simultaneously, ecosystem services in the Southern Ocean will likely increase. Such decoupling of ecosystem services and endemic species will require consideration in the management of human activities such as fishing in Antarctic marine ecosystems.

A framework for linking competitor ecological differences to coexistence.

Not all ecological differences among competing species affect their ability to locally coexist. Rather, the differences that promote stable coexistence can be those which cause each species to experience stronger intraspecific than interspecific competition. Recent approaches have established how to detect the demographic signature of these competitive effects, but alone they cannot elucidate the ecological differences among species that yield these patterns. Here, we present a unifying experimental and observational framework that identifies potential ecological differences among species shaping their responses to intra- and interspecific competition. We first describe a conceptual model establishing why the strength of intra- and interspecific competitive interactions should vary along environmental gradients related to species ecological differences. We then show how to apply the framework using Enallagma damselflies, a diverse group of predatory aquatic insects. To determine how species responded to intra- and interspecific competition along environmental gradients, we experimentally manipulated the relative abundances of three species and replicated this across five lakes which varied in environmental conditions affecting larval damselfly per capita growth and mortality rates-key vital rates regulating their populations. Results suggest Enallagma are ecologically differentiated in ways that in some communities can result in intraspecific competition exceeding interspecific competition. However, in many cases the opposite was true, or the effects of intra- and interspecific competition were equivalent via growth and mortality responses. Moreover, these effects tended to be weak and asymmetrical among competitors, which suggests that differential responses of larval growth and mortality to intra- and interspecific competition may not contribute strongly to the maintenance of Enallagma diversity. Different environmental factors appear to shape these demographic responses to competition, providing insight into the ecological mechanisms regulating damselfly assemblages. This framework can be broadly applied to identify the ecological differences among species that may promote coexistence, advancing knowledge of the mechanisms underlying coexistence and overcoming some limitations of purely phenomenological approaches.

Relationships between biotic indices, multiple stressors and natural variability in New Zealand estuaries

In response to the need to assess the ecological quality or health of marine benthic habitats, there has been a proliferation of biotic indices based on soft sediment macrofaunal communities. While shown to be useful in areas where they have been developed, some indices may not be readily transferrable to other regions due to differences in species ecology or composition, stressor type or magnitude, and natural variability. Using a national New Zealand dataset compiled from estuary monitoring data for 2001–2016, we used linear mixed models to determine the effect of multiple stressors (sediment mud content, metals and total phosphorus) and natural variability (associated with space, estuary type and time) on nine indices developed in New Zealand and overseas. The Richness-Integrated AZTI Marine Biotic Index (RI-AMBI), a modification of a popular overseas biotic index, had the most variation explained by stressors overall (marginal pseudo-R2=0.22 compared to ≤0.15 for all other indices). This variation was primarily explained by a single stressor, sediment mud content, which is the dominant stressor in New Zealand estuaries. However, although the overall variation explained by stressors was lower for all other indices, multiple, rather than single, stressors had significant effects on some indices. For example all three stressors had a significant effect on the Traits Based Index, and the variation explained by metals was highest for this index. Relatively high amounts of natural and unexplained variation for all indices suggested that further understanding is required before operational implementation of indices at a national scale. Thus, the use of more than one index, i.e. a weight of evidence approach, is suggested to minimise uncertainty related to inaccuracy and misclassification of ecological health in New Zealand estuaries.

Diurnal and Nocturnal Dive Durations and Inter-Dive Intervals of Stiff-Tailed Ducks in Puerto Rico

Research comparing dive durations and inter-dive intervals of stiff-tailed diving ducks, which is important for understanding differences in species ecology, is lacking for the non-migratory Masked Duck (Nomonyx dominicus) and West Indian Ruddy Duck (Oxyura jamaicensis jamaicensis), and the migratory Northern Ruddy Duck (Oxyura jamaicensis jamaicensis). Although the Northern Ruddy Duck and West Indian Ruddy Duck are considered the same species, we treated them separately to evaluate possible ecological differences. All three were observed at the same time in the same place in Laguna Cartagena National Wildlife Refuge, Puerto Rico. Dive durations and inter-dive intervals were recorded for Masked Duck (n = 60), Northern Ruddy Duck (n = 70), and West Indian Ruddy Duck (n = 445) from 1 January through 30 April 2015 and 2016. The Northern Ruddy Duck had a longer mean (± SE) dive duration (22.9 ± 0.75 sec) than the West Indian Ruddy Duck (18.8 ± 0.02 sec). Northern Ruddy Ducks likely had longer dive times because of their larger body size and migratory behavior.

Terrestrial Salamanders Alter Antipredator Behavior Thresholds Following Tail Autotomy

Abstract: Prey animals avoid and survive encounters with predators through morphological and behavioral mechanisms, but these defenses can negatively affect fitness when individuals forgo foraging and reproductive opportunities. Although many studies have focused on the costs associated with antipredator behavior, few have evaluated how that behavior changes immediately following a nonlethal interaction with a predator. Understanding how differences in species ecology (i.e., autotomy and regeneration capabilities) influence antipredator behaviors prior to and following a predation attempt could provide insight into how animals cope with living among predators. In this study, we evaluated the antipredator and compensatory behaviors of Northern Zigzag Salamanders (Plethodon dorsalis) to determine how attempted predation affects behavioral responses to perceived predation risk. In a laboratory setting, we performed behavioral assays evaluating escape distance, exploratory movements, cover use, eating habits...

Trait distribution patterns in savanna and forest plant assemblages and their relationship with soil features

Community ecologists seek to understand the processes acting on community assembly and the importance of species ecological differences to the co-existence of organisms. Here we investigated trait distribution patterns in two contrasting vegetation types, how the inclusion of intraspecific variability improves our ability to understand trait-based assembly, and if soil features predict the occurrence of non-random trait distribution patterns. We conducted our study at Emas National Park, Goias, Brazil. We used a null model approach to investigate trait distribution patterns and a model selection approach to quantify soil features important in structuring assemblages. In savanna, we detected trait convergence at individual and species level (evidence of environmental filters) favoring plants with resource conservation strategies. In forests, however, trait dispersion at individual level equal to a random expectation corroborated a premise of neutral theory (individuals ecological equivalence). Nevertheless, at species level, we found convergence (seed mass) and divergence (height), reflecting distinct strategies related to light capture and resource use. Therefore, including intraspecific trait variability did not improve the detection of non-random trait distribution patterns. Furthermore, the influence of soil features on trait patterns was different between savanna and forest. There was a tendency for niche differentiation toward more fertile and clayey soils, but the relative importance of soil factors in assembling communities could not be generalized for savannas and dry forests.

The ecology of differences: assessing community assembly with trait and evolutionary distances

Species enter and persist in local communities because of their ecological fit to local conditions, and recently, ecologists have moved from measuring diversity as species richness and evenness, to using measures that reflect species ecological differences. There are two principal approaches for quantifying species ecological differences: functional (trait-based) and phylogenetic pairwise distances between species. Both approaches have produced new ecological insights, yet at the same time methodological issues and assumptions limit them. Traits and phylogeny may provide different, and perhaps complementary, information about species' differences. To adequately test assembly hypotheses, a framework integrating the information provided by traits and phylogenies is required. We propose an intuitive measure for combining functional and phylogenetic pairwise distances, which provides a useful way to assess how functional and phylogenetic distances contribute to understanding patterns of community assembly. Here, we show that both traits and phylogeny inform community assembly patterns in alpine plant communities across an elevation gradient, because they represent complementary information. Differences in historical selection pressures have produced variation in the strength of the trait-phylogeny correlation, and as such, integrating traits and phylogeny can enhance the ability to detect assembly patterns across habitats or environmental gradients.

Quantitative analysis of forest fragmentation in the atlantic forest reveals more threatened bird species than the current red list.

Habitat loss and attendant fragmentation threaten the existence of many species. Conserving these species requires a straightforward and objective method that quantifies how these factors affect their survival. Therefore, we compared a variety of metrics that assess habitat fragmentation in bird ranges, using the geographical ranges of 127 forest endemic passerine birds inhabiting the Atlantic Forest of Brazil. A common, non-biological metric — cumulative area of size-ranked fragments within a species range — was misleading, as the least threatened species had the most habitat fragmentation. Instead, we recommend a modified version of metapopulation capacity. The metric links detailed spatial information on fragment sizes and spatial configuration to the birds’ abilities to occupy and disperse across large areas (100,000+ km2). In the Atlantic Forest, metapopulation capacities were largely bimodal, in that most species’ ranges had either low capacity (high risk of extinction) or high capacity (very small risk of extinction). This pattern persisted within taxonomically and ecologically homogenous groups, indicating that it is driven by fragmentation patterns and not differences in species ecology. Worryingly, we found IUCN considers some 28 of 58 species in the low metapopulation capacity cluster to not be threatened. We propose that assessing the effect of fragmentation will separate species more clearly into distinct risk categories than does a simple assessment of remaining habitat.

Evaluation of Habitat Suitability Models for Forest Passerines Using Demographic Data

ABSTRACT Habitat suitability is often used as a surrogate for demographic responses (i.e., abundance, survival, fecundity, or population viability) in the application of habitat suitability index (HSI) models. Whether habitat suitability actually relates to demographics, however, has rarely been evaluated. We validated HSI models of breeding habitat suitability for wood thrush (Hylocichla mustelina) and yellow‐breasted chat (Icteria virens) in Missouri, USA. First, we evaluated HSI models as a predictor of 3 demographic responses: within‐site territory density, site‐level territory density, and nest success. We demonstrated a link between HSI values and all 3 types of demographic responses for the yellow‐breasted chat and site‐level territory density for the wood thrush. Second, we evaluated support for models containing HSI values, models containing measured habitat features (e.g., tree age, tree species, ecological land type), and models containing management treatments (e.g., even‐aged and uneven‐aged forest regeneration treatments) for each demographic response using model selection. Models containing HSI values received more support, in general, than models containing only habitat features or management treatments for all 3 types of wildlife response. The assumption that changes in habitat suitability represent wildlife demographic response to vegetation change is supported by our models. However, differences in species ecology may contribute to the degree to which HSI values are related to specific demographic responses. We recommend validation of HSI models with the particular demographic data of interest (i.e., density, productivity) to increase confidence in the model used for conservation planning.

Rythmes circannuels chez les mammifères hibernants sauvages

Circannual rhythms have been studied for 25 years. Most information has come from work on hibernators. Like circadian rhythms, circannuals rhythms are endogenous, innate, self sustained, and their spontaneous frequencies (biological period) are always different from astronomical time. They are insensitive to temperature changes. Their mechanisms are not yet known. Circannual rhythms are synchronized by external factors. There is, however, a great variability among these rhythms, some species being better synchronized than others. Differences in species ecology could be involved in this variability. The adaptative value of these rhythms is discussed.