The cover image relates to the Research Article https://doi.org/10.1111/ddi.13912 “A race against extinction: The challenge to overcome the Linnean amphibian shortfall in tropical biodiversity hotspots” by Carné et al. A Malagasy treefrog from the genus Boophis (B. aff. madagascariensis) recorded in Marojejy National Park, Northern Madagascar. Image Credit: Albert Carné.
The contact zone of three zoogeographic realms, the Palearctic, Saharo-Arabian and Oriental, is an evolutionary cradle of high species richness and endemism in Iran. In this study, we investigate statistically inferred bioregions of Lepidoptera in this region. Additionally, we assess species turnover and potential conservation gaps across the defined bioregions in this country.
Iran.
Lepidoptera.
Potential ranges of Lepidopteran species were estimated using species distribution modelling and masking unsuitable ecosystem patches within a Minimum Convex Polygon, utilising the most comprehensive dataset available for the group to address the knowledge gaps in their known distribution. A presence/absence matrix was generated to define bioregions using clustering- and network-based methods. We then assessed the faunistic relationships of the defined bioregions and the degree of coverage of these regions by the network of protected areas (PAs) within the country.
Despite some differences, the presence of five main bioregions for Lepidoptera was suggested by both clustering- and network-based methods. Beyond this, six and seven small zones were detected respectively, on the overlapping areas of major bioregions as potential transition zones. Ultimately, we found an uneven distribution and extensive gap of PAs across the detected bioregions.
The results of this study suggest a crucial transitional position of Iran between three main global zoogeographic realms. While similar to the results of the clustering-based method, the bioregions detected by the network-based method are more compatible with previously identified ecoregions, macrobioclimates and phytogeographical regions of the country. The most diverse defined bioregions and transition zones in this study are on average protected by less than 10% of their total areas. Further studies are needed to investigate the historical and ecological drivers that differentiate the species assemblages between bioregions and zoogeographic realms.
Ecosystems are witnessing drastic changes in biodiversity worldwide. However, it is still unclear whether changes in phylogenetic diversity—a measure of the evolutionary relationships among species—reflect observed changes in species richness. Specifically, we ask whether changes in local phylogenetic diversity correlate with changes in species richness and examine if major taxonomic groups show diverging trends.
Global.
We estimate how local phylogenetic diversity has changed compared to species richness and whether there were diverging patterns across taxonomic groups. We use a database of compiled assemblage time series from around the world, BioTIME. We use assemblage total evolutionary history (Faith's phylogenetic diversity; PD) as well as average relatedness (mean pairwise distance and mean nearest taxon distance; MPD and MNTD, respectively) as measures of phylogenetic diversity and report taxon-level and assemblage-level posterior slope estimates from a Bayesian hierarchical model. We report trends in four major taxonomic groups: fish, birds, terrestrial mammals and terrestrial plants.
We found strong evidence of widespread increases in MPD across fish and bird assemblages, reflecting decreases in average relatedness and strong evidence of a decrease of MPD in mammals, indicating the opposite. Conversely, we did not find consistent directional change in MNTD, though null average trends included notable positive and negative trends across studies and regions. We also found moderate evidence that SR and PD were increasing in fish assemblages, while they were decreasing in mammals.
Our findings suggest that changes in species composition are significantly altering the evolutionary makeup of assemblages at the local scale and that overall patterns diverge within and across taxonomic groups. We suggest potential drivers of these changes but highlight that our results are more generalisable for fish and birds than for mammals and plants, given the variation in geographical coverage and sample size.
Understanding the distribution of marine biodiversity is critical for evidence-based identification of areas for protection and restoration. Taxonomic richness is a key, intuitive component of biodiversity and is often used to guide marine spatial planning and protection. In this study, we explore the relative merits of two spatial modelling approaches, stacked species distribution models (S-SDMs) and macro-ecological models (MEMs), for mapping the richness of benthic invertebrate taxa.
New Zealand Exclusive Economic Zone.
Two hundred and seven individual layers from SDMs of benthic invertebrate genera were pooled from an existing database and stacked to create a single genera richness layer. The same occurrence data used to develop the SDMs, comprising over 120k occurrences, was used to fit MEMs using an ensemble modelling approach.
The S-SDM layer performed poorly when validated against a database of observed genera richness, while the MEM approach performed well. While there were some consistencies in the areas predicted as high richness, substantial differences between the methods were also apparent, with the MEM seemingly better able to discern nuanced, fine-scale patterns in richness. Areas of high richness predicted by the MEM include parts of the Chatham Rise, a large component of the sub-Antarctic region, continental-shelf and coastal habitat in the south of the South Island, the north-east coast of the North Island, around East Cape and the Kermadec, Lau-Colville and Macquarie Ridges.
Spatial and catchability biases in the underlying occurrence data may contribute to the poor performance of the S-SDM and suggest the approach may not be appropriate when using occurrence datasets with limited systematic sampling. The predictions from the MEM provide the best available information for the distribution of benthic invertebrate richness for New Zealand waters and thus offer important information for current and future marine spatial planning processes.
The white shark (Carcharodon carcharias) is one of the world's largest and most recognisable marine predators but has suffered significant declines since the mid-twentieth century. Conservation efforts remain complicated by persistent knowledge gaps associated with white shark biology and ecology, including the biological connectedness of white shark populations. We re-assess patterns of population genetic structure in Australian white sharks, where two subpopulations—eastern and southern-western—are currently recognised based on previous animal tracking and genetic assessments.
Population genomic analyses are performed using tissues from ~650 individual white sharks and ~7000 single nucleotide polymorphism (SNP) loci generated through reduced genome representation sequencing. We test for evidence of genetic structure and relatedness among sharks from eastern and southern Australia and use population genetic simulations to assess the likely strength of inter-generational migration between regions.
This study challenges the current paradigm of population structure in Australian white sharks, showing a lack of genetic structure between white sharks from eastern and southern Australia. These findings are further supported by population genetic simulations and kinship analyses indicating high levels of intergenerational migration and relatedness between regions. Consistent with recent reports from eastern Australia, we also detected high levels of relatedness among juvenile and subadult white sharks and estimated the overall effective population size (Ne) of Australian white sharks to be less than 500 individuals. Furthermore, we provide evidence of a potential reduction in Ne over the last two generations.
Overall, these findings highlight the need to consider this revised estimate of genetic structure when discussing the management and conservation of the species. Our results also raise concerns for the conservation of Australian white sharks highlighting risks of potential inbreeding, and reductions in population fitness and resilience. We discuss the need for further research and the importance of ongoing population monitoring.
We explore the impact of demography and biogeographic history on the interpretation of ecological niche model, highlighting the potential for integrating genetic and ecological approaches to elucidate the evolutionary dynamics underlying the geographic distributions of cryptic species.
Western Palaearctic (Africa and Europe).
We conducted intensive sampling across the Iberian Peninsula to obtain mtDNA phylogeographic data and to develop fine-scale ecological niche models, projecting these models into both past and future scenarios for the cryptic earwigs Forficula dentata and F. mediterranea. Additionally, we utilised Bayesian skyline plot (BSP) analyses to reconstruct demographic histories and infer past population trends for both species.
The phylogeographic patterns revealed divergent evolutionary histories: F. dentata exhibited a well-established, geographically structured lineage, whereas F. mediterranea displayed a star-shaped pattern characteristic of recent expansion. Comparison between current climate models and those projected into the past and future indicate that F. dentata is likely facing a substantial reduction in its suitable habitat due to ongoing climate change, possibly exacerbated by increasing competition with F. mediterranea.
Our results suggest that climatic factors alone cannot determine the distribution of cryptic species. Historical and demographic factors play a crucial role in shaping their current geographical structure. In addition, human-mediated dispersal and ongoing climate change may contribute to the genetic and spatial structure within the F. auricularia species complex. Overall, exploring the intricate interplay between historic, genetic and geographic distribution is recommended to overcome contradictory predictions of climate models.
We investigated the effects of habitat destruction and hunting on the functional decline of top predators, specifically jaguar and puma, in the Gran Chaco.
The 1.1 million km2 South American Gran Chaco.
We used spatially explicit, individual-based models for jaguars and pumas, incorporating detailed information on habitat suitability and hunting pressure. We parameterized our models with literature data and calibrated them through a Delphi expert-elicitation process. We simulated population trajectories under a hypothetical, threat-free, baseline versus different threat scenarios.
Under combined threats of hunting and habitat loss, jaguar and puma populations declined by 88% and 80%, respectively, compared to range contractions of 48% and 35%, respectively. Both species remained regionally viable, particularly due to large protected areas, which acted as population sources but were surrounded by strong sinks. We observed a widespread weakening of the top carnivore guild function, with at least one species extirpated across 67% of the Chaco and strong declines (> 80%; considered here as functional loss) for both species concurrently across 61% of their area of historical co-occurrence. Hunting was a much stronger driver of population declines (88% and 77% for jaguars and pumas, respectively) compared to habitat destruction (26% and 22%).
Large predators play key functional roles in ecosystems. Our findings reveal that these functions can be lost over vast areas due to the combined effects of habitat destruction and hunting, with functional loss extending far beyond the areas of species' extirpation. Very large protected areas, like Kaa-Iya in Bolivia, are crucial for maintaining viable populations of top predators, highlighting the pressing need for increased protection and connectivity in the Chaco to prevent further trophic downgrading. More generally, our research underscores the value of spatially detailed, mechanistic models for disentangling the complex dynamics of multiple threats on ecological functioning at broad scales.
The integration of high-quality field data with high-resolution remote sensing data can give detailed insights into the spatial distribution of biodiversity and provide valuable information for biodiversity conservation at a scale relevant for management action. We developed a framework based on remote sensing data and field surveys for modelling species richness and abundance of butterflies at high spatial resolution to inform about the spatial distribution of butterfly species richness and abundance and analyse their drivers and the scale of effect of landscape factors.
Western Austria.
We combined structured butterfly surveys at 175 grassland sites in western Austria with remote sensing variables describing topography, grassland characteristics, and the landscape composition and configuration at different radii around a site. For spatial predictions of butterfly species richness and abundance, generalised linear models with elastic net regularisation were used and compared with stepwise variable selection. To analyse the influence of selected variables and their scale of effect, models with landscape variables in different radii around the sites and variables describing topography were applied.
For species richness, the Spearman rank correlation between predicted and measured values was 0.62. For abundance, predictive power was lower with a correlation of 0.52. Models with variables from smaller radii (125 and 250 m) generally showed better predictive performance than those at larger radii (500 and 1000 m). We found an effect of elevation, maximum grassland productivity, northness, and forest ecotone density in most models.
Integrating remote sensing data with spatial modelling techniques substantially enhances our ability to understand patterns and identify key drivers of butterfly species richness at high spatial resolution. Our study highlights the positive influence of forest edges, small woody features, and moderate grassland productivity on butterfly species richness and abundance.
Oviparous elasmobranchs lay benthic eggs with long incubation periods, many of which also require habitat-forming sessile organisms for their development. However, they are threatened by bottom-trawling fishing impacts. Here, we aimed to identify the suitable habitat distribution of small-spotted catshark (Scyliorhinus canicula) egg nursery areas, assess their current protection extent by an existing no-take MPA network and their coverage by other delimited spatial-based conservation areas.
Balearic Sea, northwestern Mediterranean.
Egg cases were collected over 5 years (2018–2022) by a bottom-trawling monitoring programme along the eastern coast of the Iberian Peninsula. We used these occurrences and various environmental variables (bathymetry, slope, sea bottom temperature, sea bottom dissolved oxygen and seabed type) to model the habitat suitability of egg nurseries for the species using maximum entropy modelling.
Sea bottom temperature was the most important variable explaining habitat suitability of egg nurseries. Small-spotted catshark eggs were found either attached to or in the same samples as various species of habitat-forming sessile organisms. We found only 3.6% (381 km2) of the modelled suitable egg nursery habitat in the Balearic Sea to be currently covered by an implemented no-take MPA network. At the same time, 52% of said MPAs are inadvertently protecting suitable egg nursery habitats (and their associated benthic community), as they were not initially planned with elasmobranchs as conservation targets. Important shark and ray areas (ISRA-IUCN) were also observed to cover egg nursery habitat (4502 km2 or 15.52%) within their boundaries.
While half of the current MPA surface is providing protection to this elasmobranch species' egg nursery areas and their associated benthic communities, they are not sufficient for their conservation. However, mapping the distributions of these essential fish habitats can help towards the 2030 European conservation target of ‘strictly protecting’ 10% of marine environments.
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