Global Ecology and Biogeography最新文献

Scale-Dependency of Native Status

Classifying populations as native or nonnative requires well-defined range boundaries for species. While many studies define native status according to large biogeographic realms, natural dispersal barriers often limit species distributions at regional or smaller spatial extents. As such, native/nonnative definitions are inherently scale-dependent and estimates of community invadedness thus depend on the spatial resolution at which native status is defined. For example, nonnative species can be introduced among realms, among regions within realms, and among ecological provinces within regions (hereafter, simply “provinces”). By explicitly considering the scale-dependency of native/nonnative status definitions, we can more effectively compare results across studies, more comprehensively evaluate the degree of invasion levels, and more objectively communicate the native status of a species.

Location

30,034 stream segments, conterminous United States.

Time Period

2000–2023.

Major Taxa Studied

Freshwater fishes.

Quantifying Fish Community Invadedness Across US Streams

We illustrate the importance of scale-dependent native status definitions by quantifying nonnative species richness and relative abundance in stream fish communities across the United States, finding that provincially nonnative species are nearly four times as prevalent as extra-realm nonnative species, and represented approximately 10% of all individuals in average community surveys.

Implications

Unrealistically broad native status definitions underestimate community invadedness. Dismissing regionally and provincially nonnative species can have severe ecological consequences, including displacement and hybridisation with native species and the loss of unique communities through biotic homogenisation. These consequences may undermine efforts to maintain and protect distinct local biodiversity and conserve endemic species.

Motivation

Subterranean biodiversity is increasingly threatened by multiple intertwined anthropogenic impacts, including habitat loss, pollution, overexploitation of resources, biological invasions and climate change. Worryingly, subterranean biodiversity is still poorly represented in conservation agendas, also due to persisting gaps in our knowledge of the organisms thriving in the often-secluded and difficult-to-access subterranean ecosystems. This is even more apparent for small-sized (body size < 1 mm) groundwater-dwelling metazoans, among which copepods (Crustacea: Copepoda) represent the dominant group in terms of both species richness and biomass.

We present a dataset including 6986 occurrence records of 588 species/subspecies of European obligate groundwater-dwelling copepods. We curated all records to make their taxonomy consistent with the current systematics of Copepoda, while assessing uncertainty in the geographic coordinates by coupling in-depth web and literature searches with GIS analyses. We suggest the data provided can be used to explore a range of eco-evolutionary questions—from the drivers of the distribution of groundwater fauna to the assembly of groundwater communities—as well as to prompt the conservation of groundwater biodiversity and more.

Main Types of Variables Contained

Occurrence records of groundwater-dwelling copepods, with details about specimen taxonomy, source of the record, occurrence locality and habitat type.

Spatial Location and Grain

Geographical Europe (including western Russian Federation), along with Turkey and Georgia. Occurrence records were assigned projected geographic coordinates (EPSG:3035) at 100 m resolution but with varying spatial uncertainty.

Time Period and Grain

1907–2017.

Major Taxa and Level of Measurement

Crustacea: Copepoda. Most records have species-level identification, while some of them are identified at the subspecies level.

Software Format

Comma-separated values file (.csv) and Excel file (.xlsx), with UTF-8 encoding and meta-data provided following the Darwin Core standard.

Aim

Increasing aridity has driven widespread synchronous fire occurrence in recent decades across North America. The lack of historical (pre-1880) fire records limits our ability to understand long-term continental fire-climate dynamics. The goal of this study is to use tree-ring reconstructions to determine the relationships between spatiotemporal patterns in historical climate and widespread fire occurrence in North American forests, and whether they are stable through time. This information will address a major knowledge gap required to inform projections of future fire.

Location

North American Forests.

Time Period

1750–1880 CE.

Major Taxa Studied

Trees.

Methods

We applied regionalisation methods to tree-ring reconstructions of historical summer soil moisture and annual fire occurrence to independently identify broad- and fine-scale climate and fire regions based on common inter-annual variability. We then tested whether the regions were stable through time and for spatial correspondence between the climate and fire regions. Last, we used correlation analysis to quantify the strength of the fire-climate associations through time.

Results

We found that broad-scale historical patterns in climate and fire have strong spatial coherence. Although climate and fire regions vary over time, large core areas of the regions were stable. The association between climate and fire varied through time and was strongest in western North America, likely due to a combination of factors, such as the magnitude of drought frequency and severity, as well as varying use of fire by human communities.

Main Conclusions

The historical perspective gained through tree-ring reconstructions of climate and fire patterns and their association suggests that climate-driven synchrony of fire across large areas of the continent in recent decades is not unprecedented, will likely continue into the future, and may exhibit similar spatial patterns.

Aim

Undersampling and other sources of sampling bias pose significant issues in marine macroecology, particularly when shaping conservation and management decisions. Yet, determining the extent to which such biases impact our understanding of marine diversity remains elusive. Here, utilising empirical data on sampling efforts, we sampled from virtually established species distributions to evaluate how deep is the influence of sampling bias on estimations of the latitudinal gradient in marine diversity.

Location

Atlantic Ocean.

Time Period

Present.

Taxa Studied

Ophiuroidea.

Methods

We developed a computer simulation that implements two null models of species distribution (the geometric constraints and the area model) in a two-dimensional domain, replicates the latitudinal distribution of historical sampling efforts and then quantifies diversity metrics (observed and estimated species richness) and sample completeness for each grid cell and latitudinal band.

Results

We found consistent patterns of observed species richness across models, noting peaks at midlatitudes regardless of whether the true richness was unimodal or flat. Dips in equatorial diversity persisted even after using different methods of species richness estimation. Additional simulations showed that estimators' accuracy improved with increased sampling efforts, but only when samples were randomly distributed. Spatially aggregated samples inflate completeness without necessarily enhancing estimators' accuracy.

Main Conclusions

This finding emphasises the imperative of bolstering sampling efforts at tropical latitudes and deploying robust statistical techniques to mitigate undersampling effects. Meanwhile, we suggest considering sampling bias as an alternative null hypothesis for recorded marine diversity patterns.

Aim

Globally, the knowledge of insect distributions is largely insufficient, and that hinders conservation actions against biodiversity loss. Focusing on butterfly diversity, we aimed to fill knowledge gaps and provide new insights into biodiversity conservation in China.

Location

China.

Time Period

Occurrence records from 1950 to 2023.

Major Taxa Studied

Butterflies, Lepidoptera.

Methods

We collected butterfly occurrence records from published literature, online databases and our butterfly specimens, and then used either species distribution models or expansion from actual occurrence sites to estimate species distribution ranges in China. We identified key environmental variables that are related to butterfly biodiversity patterns, and delineated priority conservation areas based on butterfly distributions.

Results

We report the first country-wide inventory and mapping of China's 1920 butterfly species. The identified hotspots of species richness are distributed mainly in southwestern, southern and southeastern China. Among variables strongly correlated with species richness, the most important one is actual evapotranspiration. Conservation priority areas under the Convention on Biological Diversity 17% area target overlapped well with the hotspots, but only 29.8% of them are covered by existing nature reserves. When that protection target increases to 30%, the additional areas are located mainly in southern China, with its large cities and intensive agriculture.

Main Conclusions

We find that some protected butterfly species have a larger area of habitat than most species, implying that the list of protected butterflies in China should be revised. Urban and farmland landscapes may help sustain butterfly diversity and they should be considered in conservation planning.