Andrés Baselga

Aim: Ecological uniqueness quantifies how different a community is relative to all other communities within the study. This broad‐sense definition of uniqueness makes it dependent on the choice of the dissimilarity metric used to quantify differences between communities. Moreover, under a narrow‐sense definition of the concept, a uniqueness metric should indicate the proportion of species in the community that are unique to that community, i.e., absent from other communities. Here we develop and assess the key properties of a reliable metric for the quantification of uniqueness and compare the behaviour of two widely used approaches: (i) average pairwise dissimilarity between the focal community and all others and (ii) Local Contribution to Beta Diversity (LCBD). Innovation: We introduce two new metrics to compute ecological uniqueness using presence/absence ( U _rlb ) and abundance data ( U _rlb.ab ), based on asymmetric Ruggiero dissimilarity ( β _rlb ) and a new abundance‐based asymmetric dissimilarity index ( β _rlb.ab ), respectively. We also identify two key properties for the quantification of uniqueness under a narrow definition of the concept: pairwise index asymmetry and independence from the number of non‐focal sites included in the study. Pairwise asymmetry refers to the possibility that the dissimilarity between community A and B differs from the dissimilarity between B and A. To show this, we provide conceptual and simulated examples assessing the behaviour of uniqueness when quantified as LCBD (Hellinger and Sørensen), as average symmetric dissimilarity (Sørensen and Simpson) and as average asymmetric dissimilarity (Ruggiero) using presence/absence data. We also include a case study using real data on European longhorn beetles. We show that both approaches (average dissimilarity and LCBD) are conceptually and mathematically equivalent, but only average dissimilarity can be interpreted in absolute terms as it accounts for the overall beta diversity (i.e., community differentiation) within the region and does not depend on the number of non‐focal communities. Conclusion: Our results show that only average dissimilarity values based on an asymmetric index allow the quantification of uniqueness that is consistent with its ecological narrow‐sense concept. Uniqueness thus emerges as an important ecological attribute that, if properly quantified, can be used to identify highly valuable communities, containing many species exclusive to them. Consequently, by focusing on uniqueness, conservation efforts can target large‐scale conservation goals with a site‐focused perspective.

Aim: Resilience is a crucial property of ecosystems experiencing accelerated degradation in natural environments. While the functional characteristics of ecosystems play a significant role in shaping their resilience, the development of functional approaches in marine conservation has been largely overlooked. In light of this deficiency, we simultaneously consider the functional richness and redundancy of marine fish communities associated with rocky reefs to uncover and characterise the thriving and struggling areas. Location: Five marine ecoregions in southern Europe. Methods: We collected data on the density of reef‐associated marine fish species using the Reef Life Survey's standardised protocol. Based on these data, we estimated the functional richness and redundancy using four key functional traits: dietary patterns, gregariousness, position in the water column, and substrate preference. Next, we applied a predictive approach by using the XGBoost algorithm to estimate these functional metrics across the study area, including areas where in situ data were unavailable. Subsequently, to identify threshold points in the predictions, we employed decision trees, enabling us to unveil thriving and struggling areas. Results: Our results indicate that the proportion of thriving areas (26.7%) is similar to that of struggling areas (26.5%), and that their distribution is heterogeneous across the ecoregions. We also find that these thriving areas are distinguished by lower values of human density, fishing pressure, chlorophyll concentrations, and they also exhibit a higher protection status compared to struggling areas. Main Conclusions: In the current context of declining resilience, it is essential to address the functional dimension of biodiversity to unveil thriving and struggling areas, thereby highlighting the regions that require prioritisation in conservation and restoration efforts. Our findings offer critical information for policymakers and governments at local, regional, and national levels, pinpointing priority areas to enhance marine resilience and prevent the ongoing loss of this vital ecosystem property.

Distinct biological communities have high conservation value because they harbour species that cannot be preserved elsewhere. However, community uniqueness is scale‐dependent: irreplaceability depends on whether community dissimilarity emerges at small or large spatial scales. To assess conservation value, here we integrate phylogenetic endemism with the spatial scaling of phylogenetic uniqueness in terrestrial vertebrates. We show that phylogenetic endemism is the most efficient single criterion to maximise global phylogenetic diversity within the smallest land area. Moreover, the spatial scaling of phylogenetic uniqueness allows distinguishing globally distinct but regionally less unique sites ‘(evolutionary hills)’, from highly irreplaceable sites even at small scales ‘(evolutionary islands)’, which support lower local diversity but host species that are both evolutionarily unique and threatened. This approach provides a non‐heuristic and stable baseline to identify high‐value biodiversity areas and offers a powerful tool for prioritising conservation efforts to safeguard evolutionary heritage effectively.

Aim: We assess the role of spatial distance and depth difference in shaping beta diversity patterns across abyssal seascape regions. We measured the decrease of faunistic similarity across the northeast Pacific seafloor, to test whether species turnover rates differ between deep and shallow‐abyssal biogeographical provinces and whether these patterns vary across functionally or taxonomically different biotic groups.Location: Abyssal NE Pacific Ocean.Time Period: Present.Major Taxa Studied: Benthic Invertebrates (13 Phyla).Methods: We examined the relationship between compositional similarity (𝛽_sim) and spatial distance, distance‐decay, in benthic megafauna communities (animals > 10 mm) based on seabed imagery data (> 36,000 specimens in 402 species) collected across 28 abyssal seascape locations spanning a total of 4000 km. By comparing the statistical parameters (intercept and slope) of decay curves, we investigated whether distance‐decay patterns differ (i) between communities above and below the carbonate compensation depth (~4400 m at N Pacific), (ii) among taxa with contrasting life‐habits and (ii) across dominant phyla.Results: We found steeper species turnover rates in communities below 4400 m and variations in distance‐decay patterns across biotic groups. Turnover was higher for taxa facultatively growing on hard‐substratum patches (polymetallic nodules) than for sediment‐dwelling or swimming organisms. Cnidaria and Porifera, respectively, depicted the most and least evident spatial decays in community similarity.Main Conclusions: We demonstrate the utility of combining seabed imaging with distance‐decay modelling to capture macroecological patterns in poorly explored deep‐sea ecosystems. Our results suggest that chemical boundaries associated with depth are a very relevant niche‐sorting mechanism driving large‐scale beta‐diversity patterns and an association between species life‐habits and dispersal limitation in abyssal seabed communities. These findings have important implications for biodiversity conservation plans in the deep ocean, amid the need to protect vast abyssal seascape ecosystems from globally rising human threats.

Unified models of biological diversity across organizational levels (genes, species, communities) provide key insight into fundamental ecological processes. Theory predicts that the strength of the correlation between species abundance and genetic diversity should be related to community age in closed communities (i.e. abundant species accumulate more genetic diversity over time than rare species). Following this rationale, we hypothesize that historical climatic events are expected to impact assembly processes, hence affecting both the species abundance distribution (SAD) and the species genetic distribution (SGD) in continental communities. Therefore, we predict that, if the congruence between SADs and SGDs depends on community age, then higher congruence would be observed in localities where climate has been more stable since the Last Glacial Maximum (LGM). We tested this prediction using relative abundance and nucleotide diversity ( cox1 ‐5′) data from 20 communities of leaf beetles along a latitudinal transect in the Iberian Peninsula. We observed that the congruence between SAD and SGD curves, measured as the correlation between the species' rank orders in both distributions, was significantly related to the change in mean annual temperature since the LGM, but not to current climatic conditions. Our results suggest that, despite the high connectivity of continental communities, historical climatic stability is still a relevant predictor of the congruence between species abundance and genetic diversity. Hence, the degree of congruence between SADs and SGDs could be used as a proxy of community stability, related not only to historical climatic variation but also to any other disrupting factors, including human pressure.

Given the sensitivity of mountain biodiversity to human pressure, it is essential to quantify changes in montane biological communities and contrast them with expectations based on potential drivers of change. This need is particularly pressing for biological groups representing important but little‐studied fractions of biodiversity, such as insects. We analyze the temporal changes (between 1998 and 2015) of leaf beetle communities in an altitudinal gradient in the Sierra de Ancares (NW Spain). Our results show temporal changes in the composition of local communities, with a tendency to assemblage thermophilization, as well as a homogenization of the spatial turnover pattern, mostly driven by an increased similarity between communities at the lower and intermediate altitudes. These temporal changes in community composition and in the spatial structure of biodiversity were associated with upward shifts of the upper altitudinal limit of warm‐adapted species and with downward shifts of the lower altitudinal limit of cold‐adapted species. While this upward shift is consistent with expectations of climate change effects, the observed downward shift suggests a land‐use change effect. Our results point to the joint effect of multiple factors (climate and land‐use change) behind temporal changes of these leaf beetle communities, which result in compositional reorganization and biotic homogenization, rather than a mere coherent displacement toward higher altitudes. More generally, we show that understanding temporal change of biodiversity requires assessing multiple community‐level metrics (e.g., variation in assemblage composition and/or changes in spatial turnover) for the detection of tendencies among the species‐specific signals (e.g., altitudinal range shifts).

Aim: To assess the relative relevance of dispersal limitation and species sorting as drivers of spatial turnover between spider faunas of European territories.Location: Continental Europe.Time period: Present.Major taxa studied: Spiders (Order Araneae).Methods: We analysed how distance‐decay patterns differ between northern and southern Europe (broadly, territories covered vs. not covered by ice sheets during the last glacial maximum, respectively) in 15 spider families, using standardized distances to allow a direct comparison between parameters (i.e. slope and intercept) of climatic and spatial distance‐decay models. Thus, we assessed North–South differences in parameters of spatial and, independently, climatic distance‐decay models, and whether those differences are explained by family‐specific traits related to dispersal ability.Results: Climatic and spatial distance‐decay patterns are very similar in northern Europe, where climatic and spatial distances are highly correlated. In contrast, slopes are steeper in spatial than in climatic distance‐decay curves in southern Europe, where climatic and spatial distances are decoupled. Moreover, family traits related to dispersal ability explained the North–South difference in spatial distance‐decay slopes, as well as the amount of nestedness‐resultant dissimilarity between southern and northern spider faunas.Main conclusions: Our results suggest that differences in beta diversity patterns between northern and southern Europe reflect the strength of dispersal limitation in spiders, which varies across families and leads to different degrees of disequilibrium with current climatic conditions depending on the taxon. Moreover, in the South of Europe, where spatial and climatic distances are uncorrelated, spatial distance‐decay models are steeper and have larger explanatory power than climatic distance‐decay models, which suggests that dispersal limitation is the main factor shaping current beta diversity patterns of European spiders at the continental scale.

Land‐use change and habitat degradation are among the biggest drivers of aboveground biodiversity worldwide but their effects on soil biodiversity are less well known, despite the importance of soil organisms in developing soil structure, nutrient cycling and water drainage. Combining a global compilation of biodiversity data from soil assemblages collated as part of the PREDICTS project with global data on soil characteristics, we modelled how taxon richness and total abundance of soil organisms have responded to land use. We also estimated the global Biodiversity Intactness Index (BII)—the average abundance and compositional similarity of taxa that remain in an area, compared to a minimally impacted baseline, for soil biodiversity. This is the first time the BII has been calculated for soil biodiversity. Relative to undisturbed vegetation, soil organism total abundance and taxon richness were reduced in all land uses except pasture. Soil properties mediated the response of soil biota, but not in a consistent way across land uses. The global soil BII in cropland is, on average, a third of that originally present. However, in grazed sites the decline is less severe. The BII of secondary vegetation depends on age, with sites with younger growth showing a lower BII than mature vegetation. We conclude that land‐use change has reduced local soil biodiversity worldwide, and this further supports the proposition that soil biota should be considered explicitly when using global models to estimate the state of biodiversity.

Aim: To test whether spatial turnover patterns of mountain madicolous insect communities in the Southern Hemisphere support the ‘mountain passes are higher in the Tropic’ hypothesis (MPHT). To do this, we compared madicolous communities in the Amazon Mountains (equator) and the Atlantic Forest Mountains (23°S).Location: Brazil.Methods: We characterized madicolous insect communities in two elevational gradients between 90 to 3000 m a.s.l. separated by 23° of latitude, totalling 108 sampling sites. Since the MPHT predicts a more intense turnover along elevational gradients at lower latitudes than at higher latitudes, we evaluated beta diversity in the Amazon mountains, at the equator, and in the Atlantic Forest mountains, in the subtropical region. We quantified multiple‐site abundance‐based dissimilarity to assess whether beta diversity was different between both regions. We also performed constrained ordination (db‐RDA) analyses to assess whether community dissimilarity (balanced variation in abundances) was uniquely or jointly explained by environmental, spatial and/or elevational predictors. Additionally, we independently assessed the relationship between community dissimilarity and altitudinal difference in each region and tested for differences in model parameters between regions.Results: Although we found high species turnover in both regions, the community variation explained by environmental factors and altitude was higher in the Amazon than in the Atlantic Forest, as evidenced by db‐RDA and altitudinal difference models. In general, communities were remarkably constrained by spatial predictors, which result from low dispersion capacity of most madicolous insects and low connectivity of madicolous systems. Consequently, the composition of madicolous insects notably diverged between regions, highlighting the complementarity and high conservation value of both systems.Main Conclusions: Our results indicate that the MPHT explains, at the community level, the differences between low‐ and high‐latitude mountain systems in community turnover along elevational gradients, even within a relatively short latitudinal distance in the Southern Hemisphere.

This study is the first attempt to assess the diversity of beetles (Coleoptera) in terrestrial moss cushions on three West Indian islands (Hispaniola, Jamaica, and Puerto Rico) based on 10 years of moss sampling in 18 localities. In total 1711 adult beetles were collected. They belong to 234 species from 30 families. The most species and specimen rich families are Staphylinidae (86 morphospecies and 1195 specimens), Curculionidae (61 morphospecies and 131 specimens), and Chrysomelidae (16 morphospecies and 185 specimens). In addition to basic bryobionts feeding on moss tissues, moss cushions host a diverse fauna of mycophagous and saprophagous Coleoptera together with predaceous species of beetles. Our results suggest that community composition in moss inhabiting beetles is determined both by geographical isolation processes and, to a lesser degree, by environmental variation across altitudinal gradients. This confirms that the greater relevance of geographical isolation is a common pattern in organisms with limited dispersal ability. Beetle abundance was not significantly related to either the volume of moss or the substrate. Despite being not significant (but close to), the observed trend was to higher beetle abundance in moss cushions collected on trees than in those collected on soil/rock. This may be resulting from the greater diversity of fungi and higher number of beetle fungivores associated with tree growing moss communities.