Ecography最新文献

Macroclimate is a key driver of biodiversity, but habitat conditions can modulate the local microclimate by amplifying or buffering macroclimatic temperatures. The interplay between microclimatic modulation and macroclimatic temperature is crucial for shaping local biodiversity in a warming world, but remains poorly understood across life forms. We examined how macroclimate and microclimatic modulation jointly shape alpha diversity across eight taxonomic groups. We surveyed multi-taxon biodiversity along gradients of macroclimate (elevation) and microclimatic modulation (habitat structure), focusing on soil bacteria, soil fungi, understory plants, ground-dwelling arthropods, moths, flying insects, bats, and birds. We hypothesized that alpha diversity would increase with temperature at both macro- and microclimatic scales, with the strongest effects for immobile and ectothermic taxa, and that microclimatic effects would be more pronounced in thermally constrained (cold) macroclimates. Contrary to our expectations, micro- and macroclimatic effects were weakest for soil bacteria, soil fungi, and vascular plants, which responded more strongly to edaphic factors. Alpha diversity increased with macroclimatic temperature for arthropods, but not for the other groups. Effects of microclimatic amplification varied across taxa, with positive effects for flying insects and bats, but negative effects for soil bacteria and fungi. Interactive effects of microclimatic modulation and macroclimatic temperature on understory plants, ground-dwelling arthropods, moths, and birds indicated that microclimate influenced diversity differently in warm versus cold macroclimates. However, we found both stronger (ground-dwelling arthropods and moths) and weaker (understory plants and birds) positive effects of microclimatic amplification under cold compared to warm macroclimates. Our findings demonstrate that effects of microclimatic modulation on biodiversity depend on macroclimatic context and differ between taxa, and thus, both have to be considered when predicting climate-change impacts on biodiversity. Conservation planning should account for potentially changing effects of microclimatic modulation under climate warming that might affect the role of climatic microrefugia within the landscape.

Whether the limits of species' ranges and their seasonal activity reflect physiological tolerance of climatic extremes is a long-standing question in ecology and has implications for species' responses to recent climate change. We explored these associations in butterflies, using thermal tolerance traits and traits describing geographic distribution across 119 butterfly species, as well as adult flight season phenological traits across 87 species, accompanied by nearly 30 years of temporal population abundance trends. Butterflies with more poleward cold range edges and those that emerged earlier in the season were better able to tolerate low temperatures. By contrast, heat tolerance was unrelated to the equatorward warm range edge position and the timing of peak abundance across the flight season. Nevertheless, the difference between heat tolerance and high-temperature extremes (warming tolerance) revealed differences in vulnerability of butterflies across large spatial extents from the tropics to the subarctic. Warming tolerances in the tropics approached zero or were in deficit for many species, whereas warming tolerances at higher latitudes were consistently large. Yet, even among butterflies at higher latitudes, there was substantial interspecific variation in warming tolerance. This variation in warming tolerance, including its components and correlates, had complex relationships with multi-decadal population abundance trends. In some cases, our results directly implicated climate as a factor associated with population trends, as range-wide coldadapted species had larger declines than more warm-adapted species. In other cases, our results implicated indirect effects of ecological and demographic consequences of climate adaptation to seasonal variation in temperature, as species with earlier emergence and longer flight seasons (traits associated with better cold tolerance and worse heat tolerance) had smaller population declines than species with later emergence and shorter flight seasons. These results suggest caution when using physiological trait-based analyses to forecast vulnerability without an explicit consideration of mechanism.

Copious questions in global change biology require estimates of climatic suitability for species in the past or future, often via transfers of ecological niche models (ENMs) using outputs from global circulation models (GCMs). However, available GCMs differ markedly, affecting hindcasts and forecasts of species potential distributions. We propose using demographic inferences based on genetic data (indicative of either population-level continuous occupation or postglacial colonization) to test which GCM leads to a better match with reality for ENM hindcasting. We implement an intuitive worked example for four isolated focal populations of a montane shrew Cryptotis mexicanus in central-eastern Mexico, by comparing suitability maps at the Last Glacial Maximum (LGM) and today. We built an optimized Maxent niche model and transferred it to the LGM based on four GCMs (CCSM4, IPSL-CM5A-LR, MIROC-ESM, MPI-ESM-P), followed by phylogeographic analyses to test hypotheses of changes in distribution according to each GCM. CCSM4 and IPSL-CM5A-LR indicated an LGM suitability area for C. mexicanus mainly in the southern portion of its range, suggesting that extant focal populations to the north result from postglacial colonization. In contrast, MIROC-ESM and MPI-ESM-P indicated LGM suitability for three or all the populations, respectively. Genetic results for the four focal populations showed high genetic diversity and signals of constant population size. Because only the hindcast based on MPI-ESM-P generated the prediction of stable occupation for all four sites, we interpret that its estimate (a cold and wet LGM climate) best approximates reality for this system. Future studies can apply this framework using more extensive genetic or genomic data and finer temporal resolutions, also exploring differences in the assumptions and methodologies underlying the various GCMs.

The phylogenetic distance among species in a community (community phylogenetic structure) has been used to infer deterministic and stochastic assembly processes, albeit with criticisms. The effect of phylogenetic scale (old versus young lineages) and spatial scale on measures of CPS are rarely tested simultaneously, especially in the boreal biome, yet are essential to unravel different assembly processes that might operate in a community. We examined lineage-specific phylogenetic structure for six vascular plant communities defined at the habitat scale (Arctic-alpine barren, bog, fen, Kalmia barren, limestone barren, and serpentine barren) on the island of Newfoundland, Canada, and the phylogenetic structure of plant communities defined at a plot scale (72 plots × 1 m²). Contrary to the expectation under the stress-dominance hypothesis of phylogenetic clustering in challenging boreal environments, the majority of clades across the six boreal habitats had random phylogenetic structure. However, we observed a shift from phylogenetic clustering at the deepest nodes of the angiosperms to no phylogenetic structure at shallower nodes (< 110 Mya), suggesting changes in assembly processes with phylogenetic scale within a habitat, and the potential role for deterministic processes at deep nodes. The random phylogenetic structure of 1 m² plots and our modeling effort to test the effect of an environmental stress gradient on community composition suggest that a complex set of stochastic and deterministic factors is responsible for species assembly at this fine spatial scale, not just abiotic filtering in hostile environments like the serpentine as predicted by the stress-dominance hypothesis. The interpretation of phylogenetic structure metrics did not change when considering species abundances or when polytomies were resolved. Taken together, inference of assembly processes must be lineage-, habitat-, and spatial scale-specific, supplemented with knowledge on trait role and evolution for which we outline future research hypotheses.

About 14% of all fern species have chlorophyllous spores, which lack dormancy, have thin walls, and have a shorter viability (only a few days in some species). These spores should have limited dispersal distances and be more susceptible to harsher climatic conditions, raising questions about the evolutionary and ecological significance of this trait. Here, we assemble the global distribution of chlorophyllous-spored ferns and assess the underlying environmental and evolutionary factors. We first evaluated the environmental predictors of the proportional representation of 1387 chlorophyllous-spored species (CSS) across 577 geographical regions using generalized linear mixed models. We then estimated the phylogenetic signal of spore type and assessed the relative importance of environmental factors in the phylogenetic structure of fern assemblages. Species richness of CSS peaked in the tropics, while their proportional representation was highest in temperate and island floras. The proportion of CSS was positively associated with water availability and less seasonal climates. Spore type was strongly conserved phylogenetically, and CSS assemblages were phylogenetically clustered towards higher latitudes. Our study provides strong evidence that chlorophyllous spores do not limit the geographical distribution of fern species and that their latitudinal distribution patterns can be explained by a combination of environmental and evolutionary factors.

In natural or human-disturbed ecosystems, ecological networks often comprise multiple interaction types, which have been increasingly represented by multipartite ecological networks. One important aspect of their network architecture is how different interaction types or subnetworks are interconnected by connector species, here defined as the interconnection structure. Previous studies have proposed various indices of connector species to characterize macro-scale interconnection patterns and micro-scale centrality, but the meso-scale interconnection structures (here defined as interconnection motifs) remain largely unexplored. Furthermore, there is no package available in the R programming language for conducting analyses of various interconnection structures.

Within a tripartite network with two interaction subnetworks, we define the forms of interconnection motifs and unique roles within these motifs. Then we introduce the R package ‘ILSM' for analyzing interconnection pattern, interconnection centrality, and interconnection motif for unweighted and weighted networks. Specifically, we derive mathematical expressions for the frequencies of interconnection motifs and species roles within motifs.

We describe the main functions in the package and demonstrate their uses with an example pollinator–plant–herbivore network. In addition, we show that interconnection motifs can reveal additional variation beyond interconnection patterns and centrality using empirical tripartite interaction networks.

‘ILSM' will help ecologists understand how different types of interactions are interconnected by shared species using interconnection pattern, centrality, and motif.

Amphibians exhibit a large diversity in reproductive and developmental strategies, which in turn are linked to their body size, life history and habitat. Here, we explore why terrestrial egg laying frogs are on average smaller than aquatic egg laying ones and whether this pattern also exists in salamanders. We hypothesized that egg deposition site and body mass are not linked directly across species, but that terrestrial egg layers occur in climates and use microhabitats that favor small masses. To test this, we compiled a dataset on egg deposition site (terrestrial or aquatic), development mode (biphasic with larvae or direct development without larvae), body mass, microhabitat use (water-dependent, ground-dwelling or arboreal) and climate within their distribution area (temperature, precipitation and seasonality in both) of 3091 frog and 244 salamander species. We analyzed the interrelations between these traits and environmental factors by using a cross-species approach and phylogenetic generalized least squares analysis. Body masses increased along a gradient from warm, humid and unseasonal climates to cold, dry and seasonal climates in frogs and salamanders. Terrestrial egg deposition was constrained to warm, humid and unseasonal climates only in frogs. Terrestrial eggs and an arboreal microhabitat use were linked in frogs and salamanders, and arboreal frogs were smaller than non-arboreal ones. We confirmed that frogs with terrestrial eggs had smaller average body masses than those with aquatic eggs, irrespective of their development mode, but this difference disappeared when we corrected body masses for the effects of climate and microhabitat use. In salamanders, however, egg deposition site and development mode were neither directly related to body mass, nor indirectly via the effects of climate and microhabitat use. Our results suggest that thermal and hydric environmental conditions determine the geographical distribution of body mass and reproductive strategies in amphibians and set the framework for their evolution.

The positive relationship between species richness and area is regarded as one of the few laws in ecology. Therefore, deviations from predictable species–area scaling, evident as high residual variance in species–area curves, are often interpreted as anomalous behaviour. Small-island systems often do not conform to species–area relationships, yet the high stochasticity in their species–area curves is frequently treated as unexplainable noise or attributed to idiosyncratic extinction rates. Here, we introduce a statistical framework that incorporates the degree of stochasticity in species–area relationships as an explicit, interpretable model parameter. Using a global island plant dataset for atolls (378 islands across 19 atolls) – prototypical examples for small-island dynamics – we show that the degree of residual variance in species–area curves can be captured, modelled, and linked to environmental conditions. Our heteroscedastic modelling approach demonstrates that apparent stochasticity in species–area relationships is not random but predictable through environmental drivers. Specifically, we found that increased rainfall reduces the residual variance around the species–area curve, indicating that resource availability is a critical factor enabling conformity to species–area scaling. Cyclone disturbance frequency did not drive stochasticity, challenging the prevailing view that disturbance regimes drive the stochasticity in species–area scaling on small islands. By treating residual variance as an explicit model parameter in species–area relationships rather than unexplainable noise, our approach provides new insights into the conditions enabling biological communities to conform to species–area scaling. Shifting the focus in species–area studies on the residual variance as an interpretable model parameter that captures the degree of conformity to species–area scaling offers novel perspectives into the environmental factors prerequisite for species–area scaling. This contributes to unifying the apparent anomalous, stochastic nature of small-island systems with the general law of linear species–area scaling.

Boreal and tundra plant communities are expected to change in biodiversity due to increasing global change pressures such as climate warming. One long-term scenario is increasing compositional similarity, i.e. biotic homogenization, which has been relatively little studied in high-latitude plant communities. Here, we study how the composition and diversity of heathland and tundra plant communities have changed in northern Fennoscandia over several decades. In 2013–2023, we resurveyed 275 historic vegetation plots, originally surveyed in 1964–1975, with percentage covers for vascular plant, bryophyte and lichen species. We analyzed temporal changes in community composition and diversity across the study area and in different biogeographic zones, continentality-humidity classes and habitat types. We found a strong homogenization trend across the study area, with plant communities becoming more similar in composition over the decades when all taxa were treated together. The observed homogenization was driven especially by the increased similarity of vascular plant and lichen communities and was largely independent of biogeographic zones or continentality-humidity gradient. Homogenization was particularly associated with the drastic encroachment of the evergreen dwarf shrub Empetrum nigrum in habitat types originally dominated by other species, and with the decrease in lichen cover. In general, our findings suggest that Fennoscandian heathland and tundra vegetation is transforming towards a more homogeneous evergreen dwarf shrub-dominated system, which may threaten ecosystem multifunctionality. Our results highlight the importance of exploring biodiversity among different metrics and growth forms to understand the overall changes in heathland and tundra biodiversity.

Between the 16th and the 20th centuries, European countries established vast colonial empires on all continents. These empires triggered profound environmental, demographic and economic transformations. It is likely that many non-native species have benefited from the newly emerged trade network between European countries and their colonies to spread to new regions, leading to an increase in invasions across countries that belonged to these empires. However, this hypothesis has not been tested, and it is still unknown whether colonial empires influenced non-native species richness and invasion dynamics over the last centuries. Here, we show that prior to 1960, countries that belonged to a colonial empire received more than twice as many non-native ant species than those that did not. During that period, ant species native to parts of an empire spread preferentially to other countries within the same empire. However, after 1960 former colonial ties had no longer an effect on ant introductions. We also found that colonized countries were the most important source of non-native ants, contradicting the ‘Imperialist dogma'. Overall, our findings show that ant invasion dynamics were shaped by the rise and fall of European colonial empires, transitioning from empire-centered invasions before 1960 to a truly global spread of species in the more recent decades.