Ecography最新文献

Pelagic-feeding seabirds deliver nutrient subsidies that enhance the productivity, biodiversity, and resilience of terrestrial and marine ecosystems, particularly in nutrient-poor tropical environments. However, the biogeophysical variables governing the fluxes of these nutrients within and among interconnected ecosystems remain poorly understood. To address this, we examined the spatial distribution of seabird-vectored nutrients in the seascape of Tetiaroa, a semi-enclosed coral atoll in French Polynesia, where seabird populations and associated nutrient cycles are recovering after recent rat eradication. We focus on the nitrogen isotope (δ¹⁵N) signatures of a dominant marine alga as evidence of seabird-vectored nutrient uptake. Integrating stable isotope analysis within a seascape ecology framework, we show that breeding seabird biomass, depth, distance to land, geographic location within the atoll, and seafloor curvature drive spatial patterns of nutrient enrichment. Specifically, our models account for up to 88% of the variation in algal δ¹⁵N signatures and reveal peak enrichment in shallow, nearshore areas where water flow slows and converges due to localised seafloor curvature. These results extend previous research by highlighting seafloor geomorphology, notably curvature, as a modulator of fine-scale nutrient delivery patterns. Although a complex model incorporating 11 high-resolution biogeophysical variables enhanced spatial predictions by revealing fine-scale variations, a simpler model using only five of these variables was comparably effective in capturing overall spatial trends. This study identifies the key seascape configuration and complexity characteristics likely to affect the spatial patterns of recovery potential following the restoration of seabird-driven nutrient cycles, offering valuable guidance for ongoing restoration efforts in this coupled island-reef system. Future investigations could assess how the effects of biogeophysical variables on nutrient delivery vary in magnitude and direction across different geographic, geological, and anthropogenic contexts.

The core–periphery hypothesis (CPH) predicts that genetic diversity is greatest at the centre and lowest at the edges of a species' distribution because genetic diversity is a function of a species' abundance, which is also expected to be greatest at the centre and lowest at the edges of the distribution. Variants of the CPH include the ‘Ramped North' (greatest variation in the north), the ‘Ramped South' (greatest in the south), and the ‘Abundant Edge' (greatest at the distributional edges). Here, we present the first standardised multi-phylum analysis of the CPH using nine indices of genetic diversity for New Zealand's marine biota, covering 52 species. Based on 80 studies across eight phyla, spatial variation in the genetic indices was tested against four models (Normal (N), Ramped North (RN), Ramped South (RS), Abundant Edge (AE)). Only 22.7% of all individual taxon-specific tests were statistically significant: Ramped North (10.5%), Ramped South (7.4%), Abundant Edge (2.6%) and Normal (2.2%). Nonetheless, amongst the Chordata (Ramped North and Ramped South), Arthropoda (Ramped South) and Mollusca (Ramped North), a reasonably consistent pattern of genetic variation was observed within each phylum. Spatially-explicit genetic diversity of the remaining taxa fitted different models but without any obvious pattern across the phyla. Generalised binomial testing of observed p-values for each genetic index across all studies revealed that 10 of 29 tests were significant (5 RN, 2 N, 2 RS, 1 AE). Overall, our meta-analysis revealed no real support for the CPH and only limited support for a Ramped model (either Ramped North or Ramped South) of spatially-explicit genetic diversity. For New Zealand coastal marine taxa, we conclude that consistently strong patterns of genetic variation across multiple taxa do not exist and the CPH requires extensive testing from multiple other regions before we can say that such patterns exist, let alone explain them.

Determining population status to inform mitigation of anthropogenic threats requires statistical approaches that investigate spatial and temporal variation. In the face of climate change it is increasingly important to differentiate between changes in population size and redistributions of populations. This is especially true for wide-ranging species such as the blue whale. Abundance of eastern North Pacific blue whales has previously been estimated using (non-spatial) closed capture–recapture and distance sampling methods, but the estimates show opposite and diverging trends over the last 30 years. Evidence that the distribution has been expanding could explain the apparent disparity, due to the confounding effects of spatial variation in sampling and the changing distribution. To investigate this, we apply, for the first time, spatial capture–recapture (SCR) methods to blue whale photo-identification data from small boat surveys to estimate abundance. The study area was defined as the length of the continental USA coastline, extending approximately 100 km offshore. Average annual effort from 1991 to 2023 was 97 days, resulting in 7358 sightings of 1488 unique individuals. We find significant support for non-linear spatiotemporal variation. In all years, there were higher densities at lower latitudes but there were notable decadal cyclical fluctuations in the number of animals using the study area. This large variation in the numbers of animals using these waters motivates further study into the relationship with environmental changes. Our results are an important step in spatially explicit modelling of observational blue whale data, which highlight the value of including spatial and temporal data and are relevant to any marine mammal species monitored using photo-identification.

The high biodiversity in mountains is attributed to species accumulation from dispersal, high habitat heterogeneity and local speciation. Landscape connectivity thereby influences colonization and speciation processes, making its net effect on biodiversity challenging to understand. This is especially true for complex and biologically diverse mountain systems, such as the Hengduan Mountains (HDM), with their remarkably high levels of endemism. Here, we mapped the distributions of 3165 endemic plant species (25% of the region's total richness) in the HDM and studied the complex interplay between landscape connectivity and climate as drivers of endemic richness, as well as endemic compositional turnover. We found that endemic richness peaks at elevations of 3000 to 4000 m a.s.l., about 1000 m higher than that of overall richness. Mean temperature of the warmest quarter, climate change velocity since the Last Glacial Maximum, and connectivity together explain patterns of both α- and β-diversity of endemism. Our models show strong explanatory power along the elevation gradient and across the landscape. Our findings point to a distinct, context-dependent role of landscape connectivity in shaping biodiversity. In the endemic hotspot of the central-western HDM, particularly within the Three-Parallel-Rivers Region, endemic diversity indices are negatively associated with landscape connectivity. In contrast, we found a positive association between endemic richness and connectivity in the northern and southern HDM, which have overall lower endemism levels. This context-dependent effect of the connectivity–richness relationship highlights the complex influences of geomorphological processes on endemic patterns at a regional spatial scale.

Habitat heterogeneity and demographic processes create variability in the major taxonomic diversity trends: 1) biotic homogenization and 2) the emergence of novel community compositions. Nonetheless, little is known about how the imprints of environmental filtering and random demographic processes on community dissimilarity vary over 1) time or 2) space. Quantifying such variation is key to revealing temporal regime shifts, latitudinal trends, and site-level specificity in the drivers of community dissimilarity.

To characterise variation in drivers of community change, we introduce the concept of ‘non-stationary community responses'. We then apply this concept to estimate temporal and spatial variability in the imprints of climate, land cover and random processes on spatial and temporal dissimilarity of community composition. As a model system, we use multidecadal monitoring data of bird (1147 monitoring sites; 49 years), butterfly (101 monitoring sites; 22 years), and moth (99 monitoring sites; 26 years) communities across a 1200-km latitudinal gradient in Finland.

Regarding spatial dissimilarity, environmental filtering had a larger imprint than what random processes had. For butterflies and moths, environmental filtering shifted from being primarily associated with land cover to being primarily associated with climate indicating a likely regime shift along with warming climate. Regarding temporal dissimilarity of bird and butterfly communities, the imprints of environmental filtering and random processes varied between monitoring sites. A conventional stationary model was unable to track such site-specific processes. The imprints did not change linearly along a latitudinal gradient.

Our results demonstrate that accounting for non-stationarity in community dynamics is needed to pinpoint temporal shifts and spatial variability in the drivers of community change. Should we assume that community change is driven by the same primary forces at all times and everywhere, then we will fail to detect the real local and contemporary drivers of change, and risk applying the wrong corrective measures.

Patterns in functional and phylogenetic diversity reflect ecological and evolutionary relationships among taxa, and thus can offer key insights into the mechanisms underlying species distributions. However, disentangling the relative influence of proximate environmental drivers versus biogeographic evolutionary history can be a challenge. Moreover, human activities have enormously impacted the global distribution of mammals over the past millennia, potentially skewing our understanding of the underlying processes influencing biodiversity accumulation and community structure. Here, we investigated how the environment shapes global patterns in terrestrial mammal diversity, and how anthropogenic impacts have altered our understanding of these mechanisms. To distinguish aspects of mammal diversity most directly influenced by proximate environmental conditions, we employed novel metrics representing the deviation between functional and phylogenetic diversity. We calculated these residual functional diversity values using both current mammal distributions and estimated distributions in the absence of human impacts to characterize the effect of anthropogenic diversity loss. Each dataset was then modeled separately as a function of key environmental drivers and compared. We found remarkable variation in residual functional diversity across terrestrial communities, suggesting the environment strongly mediates the relationship between functional and phylogenetic diversity. Specifically, temperature seasonality and evapotranspiration play key roles in shaping global patterns in mammal functional diversity. Critically, the strength of these relationships is dampened by anthropogenic biodiversity loss, which has homogenized functional and phylogenetic community structure across environmental gradients. By disentangling the role of human impacts on both patterns and purported mechanisms of mammal diversity, our results provide a more accurate depiction of the fundamental relationships underlying mammal communities.

Around the world, ecological communities are becoming more similar to one another in a process known as biotic homogenization – an increase in similarity among communities over time. While biotic homogenization has been widely studied among spatial communities, very little attention has been paid to beta diversity between seasonal communities, especially in terms of functional or phylogenetic diversity. In temperate ecosystems, seasonality plays a major role in structuring ecological communities, but anthropogenic pressures are altering community composition. We analyze 40 years of data to study changes in beta diversity between winter and breeding bird communities in the northeastern US. We find evidence of taxonomic, phylogenetic, and functional homogenization between winter and breeding bird communities driven by decreasing turnover. Changes in phylogenetic diversity largely mirrored changes in taxonomic diversity, but functional diversity did not, with functional richness increasing in both seasons despite species richness increasing only in winter. Functional homogenization was driven by 1) decreasing occurrence of winter boreal finches and breeding season aerial insectivores, which reduced the functional space unique to either season, and 2) increasing occurrence of raptors, mergansers, wild turkey, and other functionally distinct species, which expanded the total functional space of both seasons and the shared functional space between seasons. Together, these shifts demonstrate a decline in the distinctiveness of functional space between seasons. Our study is one of the first to describe functional and phylogenetic homogenization between seasons and highlights the importance of considering seasonal homogenization and of using multiple facets of diversity to describe and understand biotic homogenization.