Ecology最新文献

Trait-based approaches can improve ecological understanding by linking fitness to the environment. The trilateral life history model is an expansion of r- and K-selection theory that reflects trade-offs between juvenile survival, fecundity, and generation time and describes differential survival of species across environmental gradients. We used this framework to generate and test hypotheses regarding community assembly and the validity of such a model in two disparate taxonomic groups, freshwater mussels and fish. We assessed the distribution of mussel and fish life history strategies across 80 sites spanning aspects of the river continuum concept within the Ouachita Highlands (USA) and asked if their distributions are predicted by a similar life history strategy framework. Because mussel and fish assemblages should both be structured by selective forces in an up- to downstream trajectory, we expected both taxa to converge on more species-rich assemblages with a greater proportion of equilibrium strategists in larger, more stable downstream habitats. We found that both mussel and fish species richness increased with watershed area as well as the proportion of equilibrium strategists in the assemblages. Our study validates the use of the trilateral life history model to test hypotheses about the distribution patterns of two coevolved taxonomic groups.

Algal dynamics are fundamental drivers of lotic ecosystem processes. Although rivers tend to be heterotrophic and have low standing stocks of autotrophic biomass, filamentous algae can cause nuisance algal blooms that alter the structure of the autotrophic assemblage. Still, the influence of these blooms on ecosystem processes can be variable. Here, we examined the structural and functional contribution of filamentous and epilithic algae by linking algal biomass measurements to daily primary production fluxes throughout two growing seasons in six sites along the Upper Clark Fork River, an open canopy, snow melt river in western Montana, USA. We partitioned daily productivity estimates across different algal groups using the spatial and temporal variability in algal assemblages across our six sites. By using reach-scale metabolism estimates, we assessed the in situ functional rates of individual algal groups. Throughout two growing seasons, we measured high fluxes of ecosystem productivity and spatially variable filamentous algal blooms. We found that the filamentous algal blooms determined the ecosystem structure in terms of total biomass and algal turnover times, but not the ecosystem functions of gross primary productivity, ecosystem respiration, or net production. Whole-reach estimates of epilithic and filamentous algae growth rates were 0.30 and 0.026 day$��{\hspace{0.17em}}^{�-�1�}�$ respectively, which are similar to rates measured in mesocosms. The epilithic algae grew and turned over rapidly, dominating total biomass production and driving ecosystem function while filamentous algae grew slowly and built up large amounts of biomass during a growing season, shaping the structure, but not function, of the ecosystem.

How do individuals tolerate both hot and cold climates of our planet? One possibility is that organisms have plastic traits, such as thermal tolerance, that allow them to function in highly variable environments. In this study, we tested whether phenotypic plasticity of temperature tolerance (i.e., acclimatization in the field and acclimation in the lab) occurs in the red harvester ant, Pogonomyrmex barbatus, at two temporal scales. We first measured the upper and lower critical thermal limits (CT_max and CT_min) of ants monthly for 2 years while concurrently measuring environmental conditions. Both CT_max and CT_min covaried with temperature in a predictable way; values increased in a positive, linear manner. We then experimentally tested whether CT_max and CT_min could shift within a shorter time period by exposing subcolonies of ants to cool (10°C), moderate (20°C), and hot (30°C) temperatures for 10 days. CT_max increased only slightly at the hottest temperature treatment (+1.2°C); however, CT_min increased considerably under both moderate (+2.6°C) and hot treatments (+3.8°C). Combined, our results suggest that the thermal tolerance of ants may be more plastic than originally hypothesized, potentially aiding an already thermophilic clade in future climate scenarios.

Costs of reproduction are predicted to shift under climate change, but the extent to which weaker or stronger costs influence population responses to interannual climate variation is unknown. We asked how seasonal climate, manipulated rainfall, and costs of reproduction influence vital rates and population growth in a long-lived herbaceous perennial plant, Primula hendersonii, across an ongoing rainfall manipulation experiment in oak savanna of northwestern North America. Simulated drought reduced population growth rates, and vital rates (e.g., probability of flowering, individual growth) responded individualistically to variation in winter, spring, and summer temperatures, although not to variation in seasonal precipitation. However, only warmer spring temperatures were associated with a decline in population growth rates. Although we observed a weak negative effect of past reproduction on growth and future reproduction for large individuals, these costs of reproduction ultimately did not influence population growth. Further, observational and manipulative experiments to detect costs of reproduction suggest subtle differences in cost expression. We show that direct climate drivers had a stronger effect on population growth than indirect changes in costs of reproduction and may be more important for understanding population persistence under climate change.

Climate change impacts ecosystems directly through differences in species-specific responses as well as indirectly through changes to the strength of species interactions. To predict how species will be impacted by ongoing environmental change, we need to better understand the relative roles of these direct and indirect effects. Salinity is a strong driver of ecological patterns and processes, and salinity regimes in coastal regions are expected to be altered by climate change through the intensification of the hydrological cycle and via climate-driven shifts in the timing and strength of the spring freshet. We hypothesized that hyposalinity can indirectly affect the intertidal community by excluding a dominant guild of herbivores, limpets in the genus Lottia. To test this hypothesis, we (1) conducted intertidal diversity surveys in regions of high versus seasonally low salinity in the Strait of Georgia, British Columbia, (2) conducted laboratory salinity tolerance trials for two important grazers (Lottia pelta and Lottia digitalis) and one primary producer (Ulva sp.), and (3) experimentally manipulated the abundance of grazers in these two regions. We show that rocky intertidal shores from two regions of disparate salinity regimes are distinct in their intertidal communities: low salinity sites were composed primarily of Mytilus trossulus, Fucus distichus, and Ulva sp., whereas high salinity sites were dominated by Chthamalus dalli, Lottia spp., and Mastocarpus sp. Our laboratory trials confirmed that freshwater inputs experienced in the low salinity region resulted in hyposaline levels which exceeded the tolerance of Lottia spp., but not that of Ulva sp. Further, we show that by excluding grazers in high salinity sites, these communities more closely resemble those of the low salinity sites than those of other high salinity sites with grazers present. Together, these results demonstrate that the pattern of distinct estuarine intertidal communities in low versus high salinity regions in the Strait of Georgia may be largely driven by the indirect effects of freshwater inputs, mediated by salinity-driven differences in herbivore population size and thus grazing pressure.

The Swiss Common Breeding Bird Monitoring (“Monitoring Häufige Brutvögel” MHB) is a long-term study organized by the Swiss Ornithological Institute. Its main goal is to collect data for estimating breeding population trends of relatively abundant and widespread species. Since 1999, 267 one-km squares laid out in a mostly systematic grid across all of Switzerland have been surveyed annually by skilled, mostly volunteer ornithologists. The sampling sites thus cover a wide range of typical Western European habitats, and an altitudinal range from 250 up to 2750 m above sea level. Bird populations are recorded using a simplified territory mapping protocol with two visits per square above the timberline and three elsewhere. Surveys are conducted during the breeding season (mid-April to early July) along a square-specific transect route that does not change over the years. A typical transect route is between 4 and 6 km long, and each visit usually lasts 3 to 4 h. The location of all visually or acoustically detected birds is recorded on topographical maps or using a smartphone app. Records that meet predefined criteria in terms of species-specific breeding period and observed behavior are retained for the subsequent step of territory delimitation. This is done automatically for most species by the program Autoterri since 2022 and was done manually before, with subsequent checks by an expert. This process finally results in an estimate of the total number of detected territories per species, square and year. The design also explicitly generates detection histories, consisting of two to three numbers that represent the number of territories found to be occupied during each respective visit, enabling the analysis with binomial N-mixture and site-occupancy models. The dataset currently covers the breeding seasons from 1999 to 2024 and includes 6852 site-by-year combinations with estimates of detected territory numbers. It covers 162 of the 166 bird species recorded at least once as potential breeders, excluding four species to prevent potential disturbance at nesting sites. Besides informing about population trends, data from the Swiss Common Breeding Bird Monitoring were used to illustrate several methodological developments in N-mixture, occupancy and related models and to answer scientific and applied questions. With its clearly defined survey method, the largely systematic distribution of its survey sites, and the long timespan covered, it is likely that this dataset will continue to make important contributions in biological and biostatistical research. Herewith, we make the annually updated data set available with a CC BY 4.0 license, allowing researchers and conservationists to use and analyze the data for their own research and conservation efforts.

Understanding the stable coexistence of species despite resource competition has been a central topic in ecology. Ant communities are particularly enigmatic as various species coexist despite resource overlap. Community ecology theory predicts stable species coexistence when intraspecific competition is stronger than interspecific competition, but due to their perennial and underground life, competition coefficients of ants have never been rigorously measured in the field. We tackled this problem by studying Diacamma cf. indicum, which allows for noninvasive mark–recapture of whole colonies. Several ant species coexisted at the study site where Diacamma was most abundant, and baiting experiments and stable isotope analyses suggested overlapping food niches. Consistently, per worker brood production of Diacamma colonies was significantly negatively correlated with con- and heterospecific worker densities within the foraging area, suggesting exploitative competition among the ants. In terms of net population growth, however, the estimated intraspecific competition coefficient was about five times larger than the interspecific competition coefficient. This is possibly because exploitative competition for food occurs both intra- and interspecifically, whereas interference competition occurs mostly among conspecifics. Indeed, for Diacamma worker survival, there was a significant (nonlinear) negative correlation only with the density of conspecific colonies within the foraging area. This is consistent with the observation that Diacamma rarely fought with other species, although it violently attacked conspecific aliens encountered in their nest vicinity. We interpreted these results in light of the recent theory of intraspecific adaptation load. This theory predicts that density-dependent adaptation to intraspecific conflict can intensify intraspecific competition and act to suppress per capita population growth in dominant species, thereby leading to species coexistence with overlapping resources. Our inclusive fitness model suggests that the intraspecific territorial aggression in Diacamma may be a counter-adaptation to intraspecific conflict, that is, brood abduction between conspecific colonies. This aggression pattern can cause the observed density-dependent worker mortality. Our population dynamic model indicates that such density-dependent excess mortality acting on dominant competitors can promote stable coexistence with subordinate competitors. Overall, our results support the intraspecific adaptation load theory that aims at integrating behavioral and community ecology to understand how adaptation interacts with population and community dynamics.

Meta-analysis (MA), a powerful tool for synthesizing reported results, is influential in ecology. While ecologists have long been well-informed on the potential problems associated with nonindependence in experimental work (e.g., pseudoreplication), they have, until recently, largely neglected this issue in MA. However, results used in MAs are likely much more similar when they come from the same locality, system, or laboratory. A simple and common form of nonindependence in MA arises when multiple data points, that is, observed effect sizes, come from the same paper. We obtained original data from 20 published MAs, reconstructed the published analyses, and then, for 14 that had not accounted for a paper effect, used three approaches to evaluate whether within-paper nonindependence was a problem. First, we found that “nonsense” explanatory variables added to the original analyses were statistically significant (p < 0.05) far more often than the expected 5% (25%–50% for four nonsense variables). For example, the number of vowels in the first author's name had a significant effect 50% of the time. Second, we found that an added dummy variable, which was randomly assigned at one of two levels, was statistically significant an average of 38% of the time, far exceeding the expected 5%. Even after including a random paper effect in the analyses, there was still an excess of significant results, suggesting that the within-paper nonindependence was more complex than modeled with the random paper effect. Third, we repeated the original MAs that did not include random paper effects (n = 14 MAs) but added a random paper effect to each revised analysis. In 12 out of the 14 MAs, an added random effect was statistically significant (indicating group nonindependence that was not accounted for in the original analyses), and often the original inferences were substantially altered. Further, incorporating random paper effects was not a sufficient solution to nonindependence. Thus, problems resulting from nonindependence are often substantial, and accounting for the problem will likely require careful consideration of the details of the potential dependence among observed effect sizes. MAs that do not properly account for this problem may reach unwarranted conclusions.