Richness Of Specialists Research Articles

Habitat loss and isolation threaten specialist flora in Baltic coastal meadows

AbstractQuestionsBaltic coastal meadows are ecologically unique habitats that have been severely impacted by habitat loss and environmental change. To determine the effects of habitat loss and isolation on their plant communities, we analysed the relationships between species richness and habitat size and amount. Because coastal meadows host species with a vast array of traits, we expected responses to vary between species groups.LocationSwedish Baltic coast.MethodsWe inventoried the presence of vascular plant species in twenty‐eight 1‐m2 plots placed along edaphically defined transects in fifteen coastal meadows. We determined the richness of three species groups: all species, halophytes and inland grassland specialists. We then mapped the habitat for coastal grassland plants using GIS overlay analysis. Using this habitat map, we calculated two variables: “habitat size” and “habitat amount”. We tested correlations between species richness measures and habitat variables, as well as determining the distribution of species traits within meadows.ResultsWe recorded 174 plant species, of which 6 were halophytes and 35 were inland grassland specialists. Species traits coincided with edaphic sea‐to‐land gradients. Halophyte and inland grassland specialist richness were significantly correlated with both habitat variables (r = 0.52–0.71). No correlations were found with total species richness. Our habitat map showed that there are 8,900 ha of managed Baltic coastal meadow left in Sweden, mostly in the south.ConclusionsSpecies traits and distribution play a major role in determining persistence in the face of habitat loss and environmental change. This is especially true for some halophyte populations, which are more susceptible to habitat size and isolation because of their specialisation. Furthermore, they risk being squeezed between the dual threats of encroaching succession and sea‐level rise. Preventing habitat loss, restoring meadows and increasing connectivity is crucial for the persistence of specialist plant species.

Temperature sensitivity of soil-borne fungal phytopathogens depends on niche breadth and land use types

Soil-borne fungal plant pathogens pose great threats to agricultural productivity and native ecosystems. However, the roles of niche breadth and land-use types in regulating the response of soil-borne fungal plant pathogens to temperature changes largely remain unclear. Here, we surveyed soil pathogens from different valleys where croplands, grasslands, and woodlands scattered in mosaic patterns. We found that pathogen richness increased with increasing temperature in grasslands but not in croplands and woodlands. After classifying the pathogens based on temperature niche, we found that the richness of specialists was sensitive to temperature changes and increased with increasing temperature in grasslands and croplands. By contrast, the richness of neutrals (those taxa not defined as generalists or specialists) did not change with temperature gradients regardless of land-use types. Additionally, pathogens were more abundant and diverse in croplands than those in grasslands and woodlands, and this pattern persisted across the temperature gradient. Our results provide evidence that temperature change and land use types could additively affect the diversity of plant pathogens in soils. This work advances our understanding of how niche breadth affects the response of pathogens to temperature, highlighting the importance of climate change and land use in regulating the abundance and diversity of pathogens.

Insect invasions track a tree invasion: Global distribution of black locust herbivores

AbstractAimMany invasive plant species benefit from enemy release resulting from the absence of insect herbivores in their invaded range. However, over time, specialized herbivores may ‘catch up’ with such invasive plants. Black locust is a tree species with a relatively limited native range in North America but has invaded large areas in virtually every temperate continent including North America. We hypothesize that both intra‐ and intercontinental spread of black locust leads to a parallel, though delayed pattern of intra‐ and intercontinental spread of insect herbivores.LocationGlobal.TaxonBlack locust, Robinia pseudoacacia, and its insect herbivores.MethodsWe compiled historical records of the occurrence of insect herbivore species associated with R. pseudoacacia from all world regions. Based on this list, we describe taxonomic patterns and investigate associations between environmental features and numbers of non‐native specialist herbivores in the portion of North America invaded by R. pseudoacacia.ResultsA total of 454 herbivorous species are recorded feeding on R. pseudoacacia across the world, with 23 of these being specialized on Robinia. From this group, seven species have successfully expanded their range beyond North America. Within North America, the richness of specialists is explained by a combination of road density, R. pseudoacacia density, distance from the R. pseudoacacia native range, and climate.Main ConclusionNon‐native herbivore species have accumulated on invasive R. pseudoacacia in both North America and in other continents. The steady build‐up of invasions likely has diminished the enemy release that this invasive tree species has benefited from – a trend that will likely continue in the future. These findings support the hypothesis that invasive plants promote parallel though delayed invasions of specialist insect herbivores.

Habitat heterogeneity determines species richness on small habitat islands in a fragmented landscape

AbstractAimThe small‐island effect (SIE), as an exception to the species–area relationship, has received much attention in true island systems. However, the prevalence and related patterns of the SIE have not been well evaluated in habitat island systems. Here, we aimed to identify the existence of SIE for habitat islands in fragmented landscapes and determine the key factors influencing species richness on small habitat islands.LocationInner Mongolia Autonomous Region, China.TaxonVascular plants.MethodsBased on 78 grassland fragments in fragmented landscapes of the agro‐pastoral ecotone of northern China, we used piecewise regression, path analysis and null models to investigate the SIE of the species–area relationship. We then used a multi‐model selection to evaluate the impacts of four influencing factors (instability, isolation, habitat heterogeneity and surrounding productivity) on species richness (including habitat specialists and generalists) on small habitat islands within the range of SIE.ResultsWe found an obvious threshold of 5.1 ha in the species–area relationship, below which habitat island area had no direct and indirect effects on species richness. Small habitat islands (<5.1 ha) host a lower percentage of habitat specialists and a higher percentage of generalists. On small habitat islands, species richness was positively affected by habitat heterogeneity while negatively affected by instability and isolation. Habitat heterogeneity had the strongest effect on species richness, positively affecting specialist richness while negatively affecting generalist richness.Main ConclusionsThere is an SIE in fragmented landscapes of the agro‐pastoral ecotone of northern China, which should be considered in biodiversity conservation. Habitat heterogeneity had a key role in determining the pattern of species richness, especially for small islands. Habitat specialists and generalists had different SIE‐related patterns. Our study highlights the importance of considering different ecological groups of species to improve our understanding of the SIE in fragmented habitats.

Spatial predictions for the distribution of woody plant species under different land-use scenarios in southwestern Ethiopia

ContextDeforestation, forest degradation and intensification of farming threaten terrestrial biodiversity. As these land-use changes accelerate in many landscapes, especially in the Global South, it is vital to anticipate how future changes might impact specific aspects of biodiversity.ObjectivesThe objectives of this study were to model woody plant species richness in southwestern Ethiopia, for the present and for four plausible, spatially explicit scenarios of the future (‘Gain over grain’, ‘Mining green gold’, ‘Coffee and conservation’ and ‘Food first’).MethodsWe used cross-validated generalized linear models for both forest and farmland, to relate empirical data on total and forest-specialist woody plant species richness to indicators of human disturbance and environmental conditions. We projected these across current and future scenario landscapes.ResultsIn both farmland and forest, richness peaked at intermediate elevations (except for total species richness in farmland) and decreased with distance to the forest edge (except for forest specialist richness in forest). Our results indicate that the ‘Mining green gold’ and ‘Food first’ scenarios would result in strong losses of biodiversity, whereas the ‘Gain over grain’ scenario largely maintained biodiversity relative to the baseline. Only the ‘Coffee and conservation’ scenario, which incorporates a new biosphere reserve, showed positive changes for biodiversity that are likely viable in the long term.ConclusionsThe creation of a biosphere reserve could maintain and improve woody plant richness in the focal region, by forming a cluster with existing reserves, would be a major step forward for sustainability in southwestern Ethiopia.

Effects of fragmentation on grassland plant diversity depend on the habitat specialization of species

Evaluating the impacts of habitat loss and fragmentation is essential for biodiversity conservation. However, an understanding of how habitat loss and fragmentation interact and affect biodiversity is limited. Based on 134 landscapes in the agro-pastoral ecotone of northern China selected by a stratified random sampling approach, we used a structural equation model to evaluate the direct effects of habitat loss and its indirect effects (via habitat fragmentation, including edge density, patch density, mean patch area, and mean nearest-neighbor distance) on grassland plant species richness (including specialists and weeds) at the landscape scale. Our results show that habitat loss had a direct negative effect on overall species richness and grassland specialist richness but a positive effect on weed richness. Meanwhile, the increase in patch density caused by habitat loss had a positive effect on overall species richness and grassland specialist richness. These results indicate that the effects of habitat loss and fragmentation can differ for habitat specialists and generalists. Increasing the number of habitat patches in the landscape could increase the species richness of habitat specialists. Our findings emphasize the importance of the management of adding habitat patches in fragmented landscapes for conserving habitat specialists.

Living on the edge: Plant diversity in the Iberian chionophilous vegetation

AbstractAimsChionophilous vegetation (i.e. snowbed vegetation and chionophilous grasslands) hosts relict arctic–alpine species, among which snowbed specialists, that find their southernmost limit in the Iberian Peninsula, where they are especially threatened by climate change. Our aims were to identify the main Iberian chionophilous vegetation groups, and analyse their plant diversity patterns and their role as refugia for snowbed glacial relicts, as well as that of Iberian high‐mountain regions.LocationIberian high mountains.MethodsWe used thebeta‐flexibleclustering method to classify 1002 vegetation relevés of Iberian chionophilous vegetation, and computed species Indicator Values and frequencies for the resulting groups. We performed a Detrended Correspondence Analysis (DCA) ordination of the relevés, and fitted six climatic variables to reveal the main ecological gradients. We constructed rarefaction curves to compare species richness between vegetation groups and between mountain regions.ResultsWe obtained eight vegetation groups, four consisting of snowbed vegetation and four of chionophilous grasslands. All but one group were present in the Pyrenees, where snowbed specialist richness was the highest. In southern and central Iberian ranges, snowbed vegetation was extremely scarce, and the main vegetation group corresponded to cryoromediterranean grasslands, where both species and specialist richness were the lowest. Snowbed and northern Iberian grassland groups accounted for similar high specialist richness, although specialists were infrequent and scarce at relevé level in these grasslands.ConclusionsDespite the set of specialised species that thrive in snowbeds, many of them are also present but scarce in northern Iberian chionophilous grasslands. In a future scenario with a high reduction of snow cover duration, which may entail the disappearance of many snowbed vegetation patches, northern Iberian chionophilous grasslands may act as terminal refugia for snowbed specialists. Nevertheless, specialists are very threatened in central and southern Iberian ranges, where snowbed vegetation is infrequent and chionophilous grasslands provide almost no shelter to them.

Scale‐dependent responses of understory vegetation to the physical structure of undisturbed tundra shrub patches

Much of the Arctic is experiencing rapid change in the productivity and recruitment of tall, deciduous shrubs. It is well established that shrub expansion can alter tundra ecosystem composition and function; however, less is known about the degree to which variability in the physical structure of shrub patches might mediate these changes. There is also limited information as to how different physical attributes of shrub patches may covary and how they differ with topography. Here, we address these knowledge gaps by measuring the physical structure, abiotic conditions, and understory plant community composition at sampling plots within undisturbed green alder patches at a taiga–tundra ecotone site in the Northwest Territories, Canada. We found surprisingly few associations between most structural variables and abiotic conditions at the plot scale, with the notable exceptions of canopy complexity and snow depth. Importantly, neither patch structure nor abiotic conditions were associated with the vegetation community at the plot scale when among-patch variation was accounted for. However, among-patch variation in plant community composition was significant and represented a gradient in the richness of tundra specialists and Sphagnum moss abundance. This gradient was strongly associated with mean patch snow depth, which was likely controlled at least in part by mean patch canopy complexity. Overall, natural variability in green alder patch structure had less of an association with abiotic conditions than expected, suggesting future changes in physical structure at undisturbed sites may have limited environmental impact at the plot scale. However, at the patch scale, increases in snow depth, likely related to canopy complexity, were negatively associated with tundra specialist richness, potentially due to phenological limitations associated with shortened growing seasons. In summary, our data suggest emergent properties exist at the patch scale that are not apparent at the plot scale such that plot-scale measurements do not represent variation in understory community composition across the landscape. The results presented here will inform future work addressing spatial variability in shrub impacts on ecosystem function and increase our understanding of understory community variation within alder patch habitats at the taiga–tundra ecotone.

Habitat Specificity Modulates the Response of Small Mammals to Habitat Fragmentation, Loss, and Quality in a Neotropical Savanna

Landscape conversion of natural environments into agriculture and pasture are driving a marked biodiversity decline in the tropics. Consequences of fragmentation might depend upon habitat amount in the landscape, while the quality of remnants can also affect some species. These factors have been poorly studied in relation to different spatial scales. Furthermore, the impacts of these human-driven alterations may go beyond species loss, possibly causing a loss of ecosystem function and services. In this study, we investigated how changes in landscape configuration (patch size and isolation), habitat loss (considering a landscape gradient of 10, 25, and 40% of remnant forest cover), and habitat quality (forest structure) affect small mammal abundance, richness, taxonomic/functional diversity, and species composition in fragmented landscapes of semideciduous forests in the Brazilian Cerrado. Analyses were performed separately for habitat generalists and forest specialists. We live-trapped small mammals and measured habitat quality descriptors four times in 36 forest patches over the years 2018 and 2019, encompassing both rainy and dry seasons, with a total capture effort of 45,120 trap-nights. Regression analyses indicated that the effect of landscape configuration was not dependent on the proportion of habitat amount in the landscape to determine small mammal assemblages. However, both patch size and habitat loss impacted different aspects of the assemblages in distinct ways. Smaller patches were mainly linked to an overall increase in small mammal abundance, while the abundance of habitat generalists was also negatively affected by habitat amount. Generalist species richness was determined by the proportion of habitat amount in the landscape. Specialist richness was influenced by patch forest quality only, suggesting that species with more demanding habitat requirements might respond to fragmentation and habitat loss at finer scales. Taxonomic or functional diversity were not influenced by landscape structure or habitat quality. However, patch size and habitat amount in the landscape were the major drivers of change in small mammal species composition in semideciduous forests in the Brazilian savanna.

Five decades of ground flora changes in a temperate forest: The good, the bad and the ambiguous in biodiversity terms

We explore how the ground flora of a temperate woodland (Wytham Woods, southern England) changed in terms of species-richness, cover and biomass over five decades; what the drivers of change were; and possible future change as a consequence of the decline in Fraxinus excelsior as a canopy dominant. Vascular plants were recorded from 164 permanent, 10x10 m plots, distributed as a 141 m grid, in 1974, 1991, 1999, 2012, and 2018. Species presence and frequency/abundance in each plot were estimated and used to model biomass changes. Changes in species-richness, vegetation composition and structure were analysed. Stands opened out by thinning or which became denser through tree growth gained or lost species respectively, particularly non-woodland species. Deer pressure favoured the spread of Brachypodium sylvaticum and reduced Rubus fruticosus. No obvious impacts of climate change, eutrophication or of invasive species were detected in the plot records although other signs suggest these are starting to affect the flora. Just 12 out of 235 species contributed 47% of all species occurrences, 82% of the vegetation cover and 87% of the modelled biomass. We conclude that the ground flora is highly variable over decadal timescales, but the patterns of change observed differ according to the measures used (species richness, cover, biomass, etc). Site level drivers in the short-term swamped effects of slower acting regional/global drivers. Legacy effects were seen in the greater richness of specialists in the older woodland. While some impacts can be mitigated by management, others are largely beyond control at the site level.

Distribution and protection of avian specialization in Europe

AbstractAimWe assessed the spatial distribution of four different types of avian specialization throughout Europe, identifying landscape features associated with specialization and quantifying where the Natura 2000 network intersects with areas of high avian specialization.LocationEurope.Time periodPresent day.Taxa studiedEuropean breeding birds.MethodsWe used the European Atlas of breeding birds and four avian specialization measures (diet, foraging behaviour, foraging substrate and habitat). We calculated specialization richness and identified geographical hotspots for each of these ecological traits. We tested whether elevational gradient, landscape heterogeneity or dominant land use predicted each type of specialization richness. We determined which types of European protected areas are most associated with higher specialization richness.ResultsDiet and foraging substrate specialists increased with elevation, whereas richness of foraging behavioural specialists decreased. There was a greater richness of dietary and habitat specialists in forests than in other environments. The Natura 2000 areas declared under Bird and both directives (Birds and Habitats) intersected with a high dietary, foraging substrate and habitat specialist richness. The richness of foraging behaviour specialists was high in Birds directive areas. Single and multiple hotspots of specialization were greater in protected than non‐protected areas. However, almost 30% of specialization hotspots did not intersect with protected areas.Main conclusionsOur findings suggest that higher levels of avian specialization in Europe are positively associated with elevation and forested land cover. Importantly, we found that the Natura 2000 network supports all types of avian ecological specialization, albeit mainly in areas declared under both directives.

What defines insularity for plants in edaphic islands?

The theory of island biogeography postulates that size and isolation are key drivers of biodiversity on islands. This theory has been applied not only to true (e.g. oceanic) islands but also to terrestrial island‐like systems (e.g. edaphic islands). Recently, a debate has opened as to whether terrestrial island‐like systems function like true islands. However, identifying the effect of insularity in terrestrial systems is conceptually and methodologically challenging because recognizing species source(s) and measuring isolation is not as straightforward as for true islands. We contribute to the debate by proposing an approach to contextualize the definition of insularity and to identify the role of isolation in terrestrial island‐like systems. To test this approach, we explored the relationship between insularity predictors and specialist species richness of edaphic islands in three systems in Europe (spring fens, mountaintops, and outcrops). We detected that insularity affected specialist richness of edaphic islands through island size and target effect (i.e. an emergent property of islands depending on their isolation and size). As predicted by the Theory of Island Biogeography, species richness decreased with increasing isularity. Given the comprehensiveness and ease of implementation of our approach, we encourage its extension to other island‐like systems.

Fragmented dry grasslands preserve unique components of plant species and phylogenetic diversity in agricultural landscapes

In intensively used landscapes biodiversity is often restricted to fragmented habitats. Exploring the biodiversity potential of habitat fragments is essential in order to reveal their complementary role in maintaining landscape-scale biodiversity. We investigated the conservation potential of dry grassland fragments in the Great Hungarian Plain, i.e. patch-like habitats on ancient burial mounds and linear-shaped habitats in verges, and compared them to continuous grasslands. We focused on plant taxonomic diversity, species richness of specialists, generalists and weeds, and the phylogenetic diversity conserved in the habitats. Verges meshing the landscape are characterised by a small core area and high level of disturbance. Their species pool was more similar to grasslands than mounds due to the lack of dispersal limitations. They held high species richness of weeds and generalists and only few specialists. Verges preserved only a small proportion of the evolutionary history of specialists, which were evenly distributed between the clades. Isolated mounds are characterised by a small area, a high level of environmental heterogeneity, and a low level of disturbance. Steep slopes of species accumulation curves suggest that high environmental heterogeneity likely contributes to the high species richness of specialists on mounds. Mounds preserved the same amount of phylogenetic diversity represented by the branch-lengths as grasslands. Abundance-weighted evolutionary distinctiveness of specialists was more clustered in these habitats due to the special habitat conditions. For the protection of specialists in transformed landscapes it is essential to focus efforts on preserving both patch-like and linear grassland fragments containing additional components of biodiversity.

Steppe islands in a sea of fields: Where island biogeography meets the reality of a severely transformed landscape

AbstractQuestionsSteppes are among the most transformed and fragmented biomes in the world, but studies on the impact of habitat loss and fragmentation on these zonal grasslands are scarce. In many regions, steppe has survived only on small habitat islands, particularly on kurgans (ancient burial mounds) surrounded by intensive croplands. We asked how the size of kurgans, their isolation and other landscape and local factors influence their species richness.LocationSouthern Ukraine.MethodsWe recorded all species of vascular plants and assessed local (area, steepness, disturbance level), landscape (distance to the nearest habitat patch, habitat amount in the surroundings, surrounding type, distance to settlements) and climatic (precipitation) conditions of 112 kurgans. We analysed species–area relationships (SARs) for total richness, habitat specialists and generalists. Then, we assessed importance of environmental factors in explaining the residuals of the SAR models.ResultsPatch area explained more than 50% of variance in total and specialist species richness. The slopes of the power function SAR (z‐values) were higher for specialists than for generalists. Connectivity measures (the distance to the nearest large habitat enclave and share of habitat in the surroundings) were more important for richness of specialists than for that of generalists, which were more controlled by the kurgan's surroundings.ConclusionsWe found that for specialist species the steppe “islands” follow the theory of island biogeography closely, but less so for generalist species. Combined with the revealed importance of connectivity for specialist species richness, we conclude that the conservation value of the kurgans in the long term likely can only be achieved with larger steppe areas in the surroundings.

Contrasting responses of diazotrophic specialists, opportunists, and generalists to steppe types in Inner Mongolia

Assembly mechanisms and responses of diazotrophic habitat specialists, opportunists, and generalists may differ among various steppe ecosystems. In this study, we investigated the ecological processes that determine the assemblies of diazotrophic communities in meadows and typical steppes (MT), desert steppes (D), and sandy steppes (S) and the effects of habitat environments on diazotrophic specialists, opportunists, and generalists in Inner Mongolia, China. The results showed that taxonomic and phylogenetic communities of diazotrophs were clustered according to their habitat types, as community dissimilarities among habitat types were significantly higher than those within them. Variable selection and dispersal limitation were recognized as the dominant ecological processes that shape diazotrophic community assemblages. Furthermore, the diazotrophic populations were dichotomized into specialists, opportunists and generalists with various strategies to adapt to habitat types. The richness of specialists significantly correlated with vegetation variables, implying that specialists have greater responses to vegetation than generalists and opportunists. This study provides insights into the mechanisms of diazotrophic community differentiation when habitat environments change.

Rare and phylogenetically distinct plant species exhibit less diverse root‐associated pathogen communities

Abstract One of the central questions in ecology is why some species are abundant while others are rare. In plant communities, some studies show that rare plant species are rare because they suffer stronger negative density‐dependent effects from pathogens compared to abundant plant species. Moreover, such pathogen effects are also suggested to be related to phylogenetic distance among plant species. However, the importance of pathogens has been commonly inferred by treating the entire pathogen community as a “black box” without explicitly characterizing pathogen richness and community composition. Here, we test two predictions. First, if rare plant species are more susceptible to pathogens, we predict that rare plant species are associated with a higher richness of specialists (i.e., pathogens that attack only a single plant species) and/or the total pathogen community. If phylogenetically distinct plant species are less susceptible to pathogens, we predict that plant species with higher phylogenetic distinctiveness (i.e., a measure of how phylogenetically distant a species is from other co‐occurring species) are associated with a lower richness of phylogenetic specialists (i.e., pathogens that attack closely related plant species) and/or the total pathogen community. We conducted a survey of the root‐associated pathogen communities from 45 plant species in a subtropical forest. We showed that approximately 40% and 25% of the pathogens were specialists and phylogenetic specialists respectively. In contrast to our first prediction, the richness of the total pathogen community but not the richness of the specialists was found to be positively related to plant species abundance, indicating that rare plant species suffer less from pathogens. Consistent with our second prediction, both the richness of the phylogenetic specialists and the total pathogen community were found to be negatively related to plant species phylogenetic distinctiveness. Furthermore, these correlations were stronger at the earlier plant life stages examined. Synthesis. We found that the root‐associated pathogen communities were less diverse in rare plant species and plant species with few close relatives. These associations varied across multiple plant life stages, suggesting that the strength of the above‐ground–below‐ground interactions change dynamically across plant life span.

Super-regional land-use change and effects on the grassland specialist flora

Habitat loss through land-use change is the most pressing threat to biodiversity worldwide. European semi-natural grasslands have suffered an ongoing decline since the early twentieth century, but we have limited knowledge of how grassland loss has affected biodiversity across large spatial scales. We quantify land-use change over 50–70 years across a 175,000 km2 super-region in southern Sweden, identifying a widespread loss of open cover and a homogenisation of landscape structure, although these patterns vary considerably depending on the historical composition of the landscape. Analysing species inventories from 46,796 semi-natural grasslands, our results indicate that habitat loss and degradation have resulted in a decline in grassland specialist plant species. Local factors are the best predictors of specialist richness, but the historical landscape predicts present-day richness better than the contemporary landscape. This supports the widespread existence of time-lagged biodiversity responses, indicating that further species losses could occur in the future.

Landscape history confounds the ability of the NDVI to detect fine‐scale variation in grassland communities

Abstract The NDVI is a remotely sensed vegetation index that is frequently used in ecological studies. There is, however, a lack of studies that evaluate the ability of the NDVI to detect fine‐scale variation in grassland plant community composition and species richness. Ellenberg indicators characterize the environmental preferences of plant species—and community‐mean Ellenberg values have been used to explore the environmental drivers of community assembly. We used variation partitioning to test the ability of satellite‐based NDVI to explain community‐mean Ellenberg nutrient (mN) and moisture (mF) indices, and the richness of habitat‐specialist species in dry grasslands of different ages. The grasslands represent a gradient of decreasing soil nutrient status. If community composition is determined by the responses of individual species to the underlying environmental conditions and if, at the same time, community composition determines the optical characteristics of the vegetation canopy, then positive relationships between the NDVI and mN and mF are expected. Many grassland specialists are intolerant of nutrient‐rich soils. If specialist richness is negatively related to soil‐nutrient levels, then a negative association between the NDVI and specialist richness is expected. However, because grassland community composition is not only influenced by abiotic variables but also by other spatial and temporal drivers, we included spatial variables and grassland age in the statistical analyses. The NDVI explained the majority of the variation in mF, and also contributed to a substantial proportion of the variation in mN. However, variation in specialist richness and the lowest values of mN were explained by grassland age and spatial variables—but were poorly explained by the NDVI. Synthesis and applications. The NDVI showed a good ability to detect variation in plant community composition, and should provide a valuable tool for assessing fine‐scale environmental variation in grasslands or for monitoring changes in grassland habitat properties. However, because the concentration of grassland specialists not only depends on environmental variables but also on the age and spatial context of the grasslands, the NDVI is unlikely to allow the identification of grasslands with high numbers of specialist species.

Principal factors controlling the species richness of European fens differ between habitat specialists and matrix‐derived species

AbstractAimWe present the first continental‐scale study of factors controlling the species richness of groundwater‐fed fens, comparing land snails, vascular plants and bryophytes. We separately analyse two ecologically distinct groups differing in conservation value and colonization/extinction dynamics, that is habitat specialists, and matrix‐derived species. Considering the island‐like nature of fen habitats, we hypothesize larger differences in the species richness–environment relationships between habitat specialists and matrix‐derived species than among the taxonomic entities.LocationSeven European regionsMethodsRichness was counted at 373 well‐preserved fens with undisturbed hydrology using the same protocols. Relationships between the species richness and water pH, waterlogging, climate and geography were explored by GLMs.ResultsLand snail richness responded mainly to water pH, regardless of habitat specialization. Richness of vascular plant and bryophyte specialists was strongly driven by geographical location of the sites, while that of matrix‐derived species was driven by waterlogging and water pH. The richness of matrix‐derived species of all taxa significantly increased with the decreasing waterlogging. Residual richness of specialists of all taxa decreased towards southern Europe.Main conclusionsIn island‐like terrestrial habitats, differences between specialists and matrix‐derived species may outweigh differences among taxa, unless there is one strong physiological determinant of species richness such as pH in land snails. The richness of specialists seems to be strongly related to difficult‐to‐measure regional factors such as historical frequency and connectivity of fen habitats. The richness of matrix‐derived species depends mainly on local conditions, such as pH and waterlogging, determining the degree of habitat contrast against the surrounding matrix. Sufficient waterlogging maintains a high representation of habitat specialists in fen communities, and disturbance of water regime may cause the increase in the number of matrix‐derived species and potentially trigger successional shifts towards non‐fen communities.

Anthropogenic habitat disturbance induces a major biodiversity change in habitat specialist bryophytes of boreal springs

Land-use is a major driver of global biodiversity loss. Despite much evidence of land-use impacts on freshwater biodiversity, long-term changes to groundwater-dependent ecosystems, and their post-disturbance recovery, remain largely unknown. We examined long-term changes of bryophyte communities in 34 boreal springs from 1987 to 2015. In 1987, all the study springs were in near-pristine condition, but 29 of them were disturbed by peatland drainage in the late 1980s and early 1990s. Five sites retained their natural status throughout the study and were used as reference sites. We aimed to assess whether bryophyte vegetation, particularly spring specialist bryophytes, showed gradual recovery toward near-pristine conditions or whether the drainage-induced habitat degradation had caused delayed extinctions of specialists, leading to dominance by generalist taxa. Bryophyte diversity showed no signs of recovery about 20years since the initial disturbance. In disturbed springs, the abundance of specialists first decreased, then remained relatively stable. Specialist richness decreased steadily and their community composition shifted gradually from the pre-disturbance state. Abundance of habitat generalists did not change but generalist richness also decreased with a time lag. At the same time, both groups remained unaltered in undisturbed springs. We conclude that without restoration measures that improve groundwater hydrology the self-recovery potential of springs is very low. As little is currently known about the effectiveness of spring restoration in halting spring biodiversity loss, the safest management strategy is to refrain from land use within broad buffers around springs.