Turnover and nestedness in subtropical dung beetle assemblages along an elevational gradient

Aim

We investigated changes in dung beetle β‐diversity components along a subtropical elevational gradient, to test whether turnover or nestedness‐related processes drive the dissimilarity of assemblages at spatial and temporal scales.

Location

An elevational gradient (200–1,600 m a.s.l.) of the Atlantic Forest in southern Brazil.

Methods

We investigated the extent to which β‐diversity varied along the elevational gradient (six elevations) at both spatial (among sites at different elevations) and temporal (different months at the same site) scales. We compared both the turnover and nestedness‐related dissimilarity of species and genera using multiple‐site or multiple‐month measures and tested whether these measurements were different from random expectations.

Results

A mid‐elevation peak in species richness along the elevational gradient was observed, and the lowest richness occurred at the highest elevations. We found two different groups of species, lowland and highland species, with a mixing of groups at intermediate elevations. The turnover component of β‐diversity was significantly higher for both spatial (i.e. elevational) and temporal changes in species composition. However, when the data for genera by site were considered, the elevational turnover value decreased in relative importance. Nestedness‐related processes are more important for temporal dissimilarity patterns at higher elevation sites.

Main conclusions

Spatial and temporal turnover of dung beetle species is the most important component of β‐diversity along the elevational gradient. High‐elevation assemblages are not subsets of assemblages that inhabit lower elevations, but this relationship ceases when β‐diversity is measured at the generic level. Environmental changes across elevations may be the cause of the differential establishment of distinctive species, but these species typically belong to the same higher taxonomic rank. Conservation strategies should consider elevational gradients in case‐specific scenarios as they may contain distinct species assemblages in lowlands vs. highlands.

     

Ecological traits modulate bird species responses to forest fragmentation in an Amazonian anthropogenic archipelago

Aim

We assessed patterns of avian species loss and the role of morpho‐ecological traits in explaining species vulnerability to forest fragmentation in an anthropogenic island system. We also contrasted observed and detectability‐corrected estimates of island occupancy, which are often used to infer species vulnerability.

Location

Tucuruí Hydroelectric Reservoir, eastern Brazilian Amazonia.

Methods

We surveyed forest birds within 36 islands (3.4–2,551.5 ha) after 22 years of post‐isolation history. We applied species–area relationships to assess differential patterns of species loss among three data sets: all species, forest specialists and habitat generalists. After controlling for phylogenetic non‐independence, we used observed and detectability‐corrected estimates of island occupancy separately to build competing models as a function of species traits. The magnitude of the difference between these estimates of island occupancy was contrasted against species detectability.

Results

The rate of species loss as a function of island area reduction was higher for forest specialists than for habitat generalists. Accounting for the area effect, forest fragmentation did not affect the overall number of species regardless of the data set. Only the interactive model including natural abundance, habitat breadth and geographic range size was strongly supported for both estimates of island occupancy. For 30 species with detection probabilities below 30%, detectability‐corrected estimates were at least tenfold higher than those observed. Conversely, differences between estimates were negligible or non‐existent for all 31 species with detection probabilities exceeding 45.5%.

Main conclusions

Predicted decay of avian species richness induced by forest loss is affected by the degree of habitat specialisation of the species under consideration, and may be unrelated to forest fragmentation per se. Natural abundance was the main predictor of species island occupancy, although habitat breadth and geographic range size also played a role. We caution against using occupancy models for low‐detectability species, because overestimates of island occupancy reduce the power of species‐level predictions of vulnerability.

     

Contrasting responses in community structure and phenology of migratory and non‐migratory pollinators to urbanization

Aim

Anthropogenic landscape change, such as urbanization, can affect community structure and ecological interactions. Furthermore, changes in ambient temperature and resource availability due to urbanization may affect migratory and non‐migratory species differently. However, the response of migratory species to urbanization is poorly investigated, and knowledge for invertebrates in particular is lacking. Our aim was to investigate whether there was a shift in community structure and phenology of hoverflies in urban landscapes, depending on migratory status.

Location

Switzerland.

Methods

Using a paired design, we compared urban and rural landscapes to investigate the impact of urbanization on the abundance, diversity and phenology of hoverflies. Furthermore, we tested whether migratory and non‐migratory species responded differently to urbanization.

Results

We observed a difference in the response of migratory and non‐migratory hoverfly communities. Although the abundance of hoverflies was higher in the rural ecosystem, driven by a high abundance of migratory species, there was no difference in species richness between the land use types. However, the community structure of non‐migratory species was significantly different between urban and rural ecosystems. The phenology of hoverflies differed between the two ecosystems, with an earlier appearance in the year of migratory species in urban landscapes.

Main conclusions

To our knowledge, this is the first study to investigate the response of migratory insect communities to urbanization. We demonstrated that migratory and non‐migratory hoverflies respond differently to urbanization. This highlights the importance of differentiating between trait and mobility groups to understand community assemblage patterns in anthropogenic landscapes. The differences in phenology supports the growing evidence that urbanization not only affects the phenology of vegetation, but also affects the higher trophic levels. Changes in the phenology and community composition of species as a result of anthropogenic landscape change may have important implications for the maintenance of key ecosystem functions, such as pollination.

     

Gone with the forest: Assessing global woodpecker conservation from land use patterns

Aim

As a result of their ecological traits, woodpeckers (Picidae, Aves) are highly sensitive to forest cover change. We explored the current land cover in areas of high species richness of woodpeckers to determinate regions where urgent conservation actions are needed. In addition, we identified woodpecker species that are sensitive to forest loss and that have high levels of human habitat modification and low levels of protection (through protected areas) in their distribution ranges.

Location

Global.

Methods

We joined available range maps for all extant 254 woodpecker species with information of their conservation status and tolerances to human habitat modifications and generated a richness map of woodpecker species worldwide. Then, we associated this information (the richness pattern and individual species’ maps) with land cover and protected areas (PAs) maps.

Result

We found that the foremost woodpecker species richness hotspot is in Southeast Asia and is highly modified. At the second species richness hotspot in the eastern Andes, we observed a front of deforestation at its southern extreme and a greater deforested area in its northern extreme but most of its area remains with forest coverage. At the species level, 17 species that are sensitive to forest modification experience extensive deforestation and have low extents of PAs in their ranges.

Main conclusions

The most diverse woodpecker hotspots are mostly occupied by human‐modified landscapes, and a large portion of the species there avoids anthropogenic environments. The level of representation of woodpecker species in PAs is low as a global general pattern, although slightly better in Asia. Our global analysis of threats to woodpecker from land use patterns reiterates the urgent conservation needs for Southeast Asian forests. Finally, based on our results, we recommend a re‐evaluation for inclusion in the Red List of five woodpecker species.

     

Species’ thermal ranges predict changes in reef fish community structure during 8 years of extreme temperature variation

Aim

To assess whether observed thermal bounds in species’ latitudinal ranges (i.e., realized thermal niches) can be used to predict patterns of occurrence and abundance changes observed during a marine heatwave, relative to other important life history and functional traits.

Location

Rottnest Island, Western Australia.

Methods

A time series of standardized quantitative surveys of reef fishes spanning 8 years of pronounced ocean temperature change is used to test whether accurate predictions on shifts in species occupancy and abundance are possible using species traits.

Results

Species‐level responses in occurrence and abundance were closely related to the mid‐point of their realized thermal niche, more so than body size, range size or trophic level. Most of the species that disappeared from survey counts during the heatwave were characterized by geographic ranges that did not extend to latitudes with temperatures equivalent to the ocean temperature peak during the heatwave. We thus find support for the hypothesis that current distribution limits are set directly or indirectly by temperature and are highly responsive to ocean temperature variability.

Main conclusions

Our study shows that reef fish community structure can change very quickly when exposed to extreme thermal anomalies, in directions predicted from the realized thermal niche of the species present. Such predictions can thus identify species that will be most responsive to changing ocean climate. Continued warming, coupled with periodic extreme heat events, may lead to the loss of ecosystem services and ecological functions, as mobile species relocate to more hospitable climes, while less mobile species may head towards extinction.

     

Conservation implications of divergent global patterns of ant and vertebrate diversity

Aim

Global conservation planning is often oriented around vertebrates and plants, yet most organisms are invertebrates. To explore the potential conservation implications of this bias, we assessed how well patterns of diversity for an influential group of invertebrates, the ants, correspond with those of three vertebrate groups (birds, mammals and amphibians).

Location

Global.

Methods

We compiled data on the number of genera of ants and the three vertebrate groups for 370 political regions across the world. We then compared their correlations both for overall diversity and between subsets of genera likely to be of conservation concern. We also developed generalized additive models (GAM) to identify regions where vertebrates and ants diverged in their diversity patterns.

Results

While ant and vertebrate diversity do positively correlate, the correlations are substantially weaker for the ant lineages of the greatest conservation concern. Vertebrates also notably fail to predict ant diversity in specific geographic areas, including Australia and Southeast Asia, parts of Africa and Madagascar, and south‐western China. These failures may be genuine differences in diversity patterns, or they may indicate important gaps in our knowledge of ant and vertebrate diversity.

Main conclusions

We conclude that it is currently unwise to assume that global conservation priorities based on vertebrates will conserve ants as well. We suspect that this also applies to other invertebrates.

     

The importance of water‐retaining features for biodiversity on artificial intertidal coastal defence structures

Aim

Artificial coastal defence structures are proliferating in response to rising and stormier seas. These structures provide habitat for many species but generally support lower biodiversity than natural habitats. This is primarily due to the absence of environmental heterogeneity and water‐retaining features on artificial structures. We compared the epibiotic communities associated with artificial coastal defence structures and natural habitats to ask the following questions: (1) is species richness on emergent substrata greater in natural than artificial habitats and is the magnitude of this difference greater at mid than upper tidal levels; (2) is species richness greater in rock pools than emergent substrata and is the magnitude of this difference greater in artificial than natural habitats; and (3) in artificial habitats, is species richness in rock pools greater at mid than upper tidal levels?

Location

British Isles.

Methods

Standard non‐destructive random sampling compared the effect of habitat type and tidal height on epibiota on natural rocky shores and artificial coastal defence structures.

Results

Natural emergent substrata supported greater species richness than artificial substrata. Species richness was greater at mid than upper tidal levels, particularly in artificial habitats. Rock pools supported greater species richness than emergent substrata, and this difference was more pronounced in artificial than natural habitats. Rock pools in artificial habitats supported greater species richness at mid than upper tidal levels.

Main conclusions

Artificial structures support lower biodiversity than natural habitats. This is primarily due to the lack of habitat heterogeneity in artificial habitats. Artificial structures can be modified to provide rock pools that promote biodiversity. The effect of rock pool creation will be more pronounced at mid than upper tidal levels. The challenge now is to establish at what tidal height the effect of pools becomes negligible and to determine the rock pool dimensions for optimum habitat enhancement.

     

Environmental gradients shift the direction of the relationship between native and alien plant species richness

Aim

To assess how environmental, biotic and anthropogenic factors shape native–alien plant species richness relationships across a heterogeneous landscape.

Location

Banks Peninsula, New Zealand.

Methods

We integrated a comprehensive floristic survey of over 1200 systematically located 6 × 6 m plots, with corresponding climate, environmental and anthropogenic data. General linear models examined variation in native and alien plant species richness across the entire landscape, between native‐ and alien‐dominated plots, and within separate elevational bands.

Results

Across all plots, there was a significant negative correlation between native and alien species richness, but this relationship differed within subsets of the data: the correlation was positive in alien‐dominated plots but negative in native‐dominated plots. Within separate elevational bands, native and alien species richness were positively correlated at lower elevations, but negatively correlated at higher elevations. Alien species richness tended to be high across the elevation gradient but peaked in warmer, mid‐ to low‐elevation sites, while native species richness increased linearly with elevation. The negative relationship between native and alien species richness in native‐dominated communities reflected a land‐use gradient with low native and high alien richness in more heavily modified native‐dominated vegetation. In contrast, native and alien richness were positively correlated in very heavily modified alien‐dominated plots, most likely due to covariation along a gradient of management intensity.

Main conclusions

Both positive and negative native–alien richness relationships can occur across the same landscape, depending on the plant community and the underlying human and environmental gradients examined. Human habitat modification, which is often confounded with environmental variation, can result in high alien and low native species richness in areas still dominated by native species. In the most heavily human modified areas, dominated by alien species, both native and alien species may be responding to similar underlying gradients.

     

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

Aim

We 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.

Location

Seven European regions

Methods

Richness 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.

Results

Land 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 conclusions

In 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.

     

Capturing arthropod diversity in complex cave systems

Aim

Identify the optimal combination of sampling techniques to maximize the detection of diversity of cave‐dwelling arthropods.

Location

Central‐western New Mexico; north‐western Arizona; Rapa Nui, Chile.

Methods

From 26 caves across three geographically distinct areas in the Western Hemisphere, arthropods were sampled using opportunistic collecting, timed searches, and baited pitfall trapping in all caves, and direct intuitive searches and bait sampling at select caves. To elucidate the techniques or combination of techniques for maximizing sampling completeness and efficiency, we examined our sampling results using nonmetric multidimensional scaling (NMDS), analysis of similarity (ANOSIM), Wilcoxon signed‐rank tests, species richness estimators and species accumulation curves.

Results

To maximize the detection of cave‐dwelling arthropod species, one must apply multiple sampling techniques and specifically sample unique microhabitats. For example, by sampling cave deep zones and nutrient resource sites, we identified several undescribed cave‐adapted and/or cave‐restricted taxa in the south‐western United States and eight new species of presumed cave‐restricted arthropods on Rapa Nui that would otherwise have been missed. Sampling techniques differed in their detection of both management concern species (e.g., newly discovered cave‐adapted/restricted species, range expansions of cave‐restricted species and newly confirmed alien species) and specific taxonomic groups. Spiders were detected primarily with visual search techniques (direct intuitive searches, opportunistic collecting and timed searches), while most beetles were detected using pitfall traps. Each sampling technique uniquely identified species of management concern further strengthening the importance of a multi‐technique sampling approach.

Main conclusions

Multiple sampling techniques were required to best characterize cave arthropod diversity. For techniques applied uniformly across all caves, each technique uniquely detected between ~40% and 67% of the total species observed. Also, sampling cave deep zones and nutrient resource sites was critical for both increasing the number of species detected and maximizing the likelihood of detecting management concern species.

     

Effectiveness of protected areas for bird conservation depends on guild

Aim

Protected areas are key conservation tools intended to increase biodiversity and reduce extinction risks of species and populations. However, the degree to which protected areas achieve their conservation goals is generally unknown for many protected areas worldwide. We assess the effect of protected areas on the abundance of 196 common, resident bird species. If protected areas were beneficial to avian biodiversity, we expect landscapes with a higher proportion of protected areas will have higher densities of species compared to landscapes with no protection.

Location

Greater Gauteng region, South Africa.

Methods

We analysed bird survey data collected over regular grid cells across the study area. We estimated bird abundance in relation to the proportion of a grid cell that was protected with the Royle–Nichols model and fitted the model once for each of the species. We examined variation in estimated abundance as a function of avian guild (defined by the type of food a species preferentially ate and its foraging mode) with a regression tree analysis.

Results

Abundance was significantly positively related to the proportion of protected areas in grid cells for 26% of the species, significantly negatively related in 15%, and not significantly related in 59% species. We found three distinct guild groups which differed in their average abundance, after accounting for associated variance. Group 1 consisted of guilds frugivores, ground‐feeders, hawkers, predators, and vegivores and average abundance was strongly positively related to the proportion of protected areas. Group 2 included granivores, and average abundance was strongly negatively related to proportion of protected areas. Group 3 included gleaners only, and average abundance was not related to proportion of protected areas.

Main conclusion

We conclude that the network of protected areas within the greater Gauteng region sustained relatively higher abundances of common birds and thus perform an important conservation role.

     

Land use legacy effects on woody vegetation in agricultural landscapes of south‐western Ethiopia

Aim

Past land use legacy effects—extinction debts and immigration credits—might be particularly pronounced in regions characterized by complex and dynamic landscape change. The aim of this study was to evaluate how current woody plant species distribution, composition and richness related to historical and present land uses.

Location

A smallholder farming landscape in south‐western Ethiopia.

Methods

We surveyed woody plants in 72 randomly selected 1‐ha sites in farmland and grouped them into forest specialist, generalist and pioneer species. First, we investigated woody plant composition and distribution using non‐metric multidimensional scaling. Second, we modelled species richness in response to historical and current distance from the forest edge. Third, we examined diameter class distributions of trees in recently converted vs. permanent farmland.

Results

Historical distance was a primary driver of woody plant composition and distribution. Generalist and pioneer species richness increased with historical distance. Forest specialists, however, did not respond to historical distance. Only few old individuals of forest specialist species remained in both recently converted and permanent farmlands.

Main conclusions

Our findings suggest that any possible extinction debt for forest specialist species in farmland at the landscape scale was rapidly paid off, possibly because farmers cleared large remnant trees. In contrast, we found substantial evidence of immigration credits in farmland for generalist and pioneer species. This suggests that long‐established farmland may have unrecognized conservation values, although apparently not for forest specialist species. We suggest that conservation policies in south‐western Ethiopia should recognize not only forests, but also the complementary value of the agricultural mosaic—similar to the case of European cultural landscapes. A possible future priority could be to better reintegrate forest species in the farmland mosaic.

     

Integrating multiple data sources for assessing blue whale abundance and distribution in Chilean Northern Patagonia

Aim

Species distribution models are useful tools for depicting important habitat, assessing abundance and orienting conservation efforts. For small populations in poorly studied ecosystems, available data are often scarce and patchy. To overcome this limitation, we aim to evaluate the use of different data types within a hierarchical Bayesian framework with the goal of modelling the abundance and distribution of a small and highly migratory population of blue whale (BW, Balaenoptera musculus) summering in Chilean Northern Patagonian (CNP).

Location

CNP, Eastern South Pacific (ESP).

Methods

We constructed a Bayesian hierarchical species distribution Model (HSDM), combining a binomial N‐mixture model used to model BW groups counts in line‐transect data (2009, 2012 and 2014) with a logistic regression for modelling presence‐availability data (2009–2016), allowing both models to share covariate parameters for borrowing strength in estimations.

Results

Distance to areas of high chlorophyll‐a concentration during spring before summering season (AHCC‐s) was the most important and consistent explanatory variable for assessing BW abundance and distribution in CNP. Incorporating accessorial presence‐only data reduced uncertainty in parameters estimation when comparing with a model using only line‐transect data, although other covariates of secondary importance failed to be retained in this model.

Main conclusions

Our results remark the capability of HSDM for integrating different data types providing a potential powerful tool when data are limited and heterogeneous. Results indicate that AHCC‐s, and possibly thermal fronts, could modulate BW abundance and distribution patterns in CNP. Preliminary model‐based delimitations of possible priority conservation areas for BW in CNP overlap with highly used vessel navigation routes and areas destined to aquaculture.

     

Geographical gradients in the biodiversity of Chinese freshwater molluscs: Implications for conservation

Aim

Large ‐ scale diversity patterns are generated by different but not mutually exclusive mechanisms. However, understanding of multiple facets of diversity and their determinants in the freshwater realm remains limited. Here, we characterized the geographical gradients, hotspots and spatial congruence of three facets of freshwater molluscan diversity and evaluated the relative importance of three different underlying mechanisms related to the energy, area/environmental heterogeneity and dispersal/historical hypotheses.

Location

China.

Methods

Species richness (SR), functional richness (FR) and taxonomic distinctness (TD, a proxy of phylogenetic diversity) were calculated for 212 drainage basins with a total of 313 molluscan species. Spatial congruence between the diversity facets was evaluated with Pearson correlation coefficient and overlap among hotspots. Multiple linear regression models and variation partitioning were used to assess the relative importance of different mechanisms.

Results

Hotspots of SR and FR were mainly concentrated in the Yangtze River and Huai River basins, while high TD values were patchily distributed across China. We found extremely low spatial congruence between TD and both SR and FR, while there was relatively high concordance between SR and FR. All diversity facets were best explained by the dispersal/historical hypothesis with strong unique effects, followed by the factors related to the energy hypothesis. The area/ environmental heterogeneity hypothesis was only weakly supported.

Main conclusions

We found a potentially strong influence of dispersal limitation and evolutionary history on the geographical diversity gradients of Chinese molluscs. This finding contrasts with the general finding that energy‐related factors are the strongest correlates of diversity patterns at large spatial scales. Moreover, our results do not support the idea that using any one diversity component as a surrogate of the others in developing conservation strategies. Instead, an integrative approach embracing multiple facets of diversity should be adopted in the conservation of freshwater biodiversity.

     

Unravelling the evolutionary origins of biogeographic assemblages

Aim

Floristic and faunal diversity fall within species assemblages that can be grouped into distinct biomes or ecoregions. Understanding the origins of such biogeographic assemblages helps illuminate the processes shaping present‐day diversity patterns and identifies regions with unique or distinct histories. While the fossil record is often sparse, dated phylogenies can provide a window into the evolutionary past of these regions. Here, we present a novel phylogenetic approach to investigate the evolutionary origins of present‐day biogeographic assemblages and highlight their conservation value.

Location

Southern Africa.

Methods

We evaluate the evolutionary turnover separating species clusters in space at different time slices to determine the phylogenetic depth at which the signal for their present‐day structure emerges. We suggest present‐day assemblages with distinct evolutionary histories might represent important units for conservation. We apply our method to the vegetation of southern Africa using a dated phylogeny of the woody flora of the region and explore how the evolutionary history of vegetation types compares to common conservation currencies, including species richness, endemism and threat.

Results

We show the differentiation of most present‐day vegetation types can be traced back to evolutionary splits in the Miocene. The woody flora of the Fynbos is the most evolutionarily distinct, and thus has deeper evolutionary roots, whereas the Savanna and Miombo Woodland show close phylogenetic affinities and likely represent a more recent separation. However, evolutionarily distinct phyloregions do not necessarily capture the most unique phylogenetic diversity, nor are they the most species‐rich or threatened.

Main conclusions

Our approach complements analyses of the fossil record and serves as a link to the history of diversification, migration and extinction of lineages within biogeographic assemblages that is separate from patterns of species richness and endemism. Our analysis reveals how phyloregions capture conservation value not represented by traditional biodiversity metrics.

     

Identifying the factors that determine the severity and type of alien bird impacts

Aim

To identify traits related to the severity and type of environmental impacts generated by alien bird species, in order to improve our ability to predict which species may have the most damaging impacts.

Location

Global.

Methods

Information on traits hypothesized to influence the severity and type of alien bird impacts was collated for 113 bird species. These data were analysed using mixed effects models accounting for phylogenetic non‐independence of species.

Results

The severity and type of impacts generated by alien bird species are not randomly distributed with respect to their traits. Alien range size and habitat breadth were strongly associated with impact severity. Predation impacts were strongly associated with dietary preference, but also with alien range size, relative brain size and residence time. Impacts mediated by interactions with other alien species were related to alien range size and diet breadth.

Main conclusions

Widely distributed generalist alien birds have the most severe environmental impacts. This may be because these species have greater opportunity to cause environmental impacts through their sheer number and ubiquity, but this could also be because they are more likely to be identified and studied. Our study found little evidence for an effect of per capita impact on impact severity.

     

Past levels of canopy closure affect the occurrence of veteran trees and flagship saproxylic beetles

Aim

Open woodlands are biologically highly diverse habitats, and veteran (i.e., old, senescent) trees are key structures supporting their biodiversity. Open canopy structure had been maintained by both natural‐ and human‐induced disturbances. In the past two centuries, suppression of such disturbances, together with forestry intensification, has turned most lowland woodlands into closed‐canopy forests. We investigated the effect of increased canopy closure on veteran trees and several threatened beetles associated with them.

Location

Floodplain woodlands along the lower Dyje and Morava rivers, Czech Republic.

Methods

We used an approach combining the study of aerial photographs with on‐ground survey of veteran trees and associated endangered beetles. The aerial images were used to obtain the information on historical (1938) and recent (2009) canopy closure in the area of 146 km², where we mapped large oaks (d.b.h. >70 cm), hollow trees and three associated beetles including the hermit beetle (Osmoderma barnabita), the great capricorn beetle (Cerambyx cerdo) and the jewel beetle Eurythyrea quercus.

Results

The presence of large oaks, hollow trees and their associated beetle species are negatively related to recent high canopy closure, and the historical level of canopy closure matters, as in nowadays closed‐canopy stands, the beetles and veteran trees are more common in places that were rather open in 1938 than in the places with closed canopy already in 1938. Moreover, the health state of veteran trees highly depends on the canopy closure.

Main conclusion

The negative effect of canopy closure on veteran trees and their endangered inhabitants is several decades delayed and may thus often go undetected. In the forests, however, large and hollow trees and their associated biodiversity are relics of the past, more open conditions. The restoration of open woodlands is therefore vital for preventing their further decline. Conservation management planning needs to take this into account wherever, veteran trees and associated biota are concerned.

     

Predicting effects of large‐scale reforestation on native and exotic birds

Aim

Ecological restoration is critical for recovering biodiversity and ecosystem services, yet designing interventions to achieve particular outcomes remains fraught with challenges. In the extensive regions where non‐native species are firmly established, it is unlikely that historical conditions can be fully reinstated. To what degree, and how rapidly, can human‐dominated areas be shifted via restoration into regimes that benefit target species, communities or processes?

Location

We explore this question in a >20‐year‐old reforestation effort underway at Hakalau Forest National Wildlife Refuge in montane Hawaii. This large‐scale planting of Acacia koa trees is designed to secure populations of globally threatened bird species by transitioning the site rapidly from pasture to native forest.

Methods

We surveyed all forest birds in multiple corridors of young planted trees, remnant corridors of mature trees along gulches and at sites within mature forest. Using a Bayesian hierarchical approach, we identified which factors (distance from forest, habitat type and surrounding tree cover) had the most important influence on native and exotic bird abundance in the reforestation area.

Results

We found that 90% of native and exotic bird species responded quickly, occupying corridors of native trees approximately a decade after planting. However, native and exotic forest birds responded to markedly different characteristics of the reforested area. Native bird abundance was strongly predicted by proximity to mature forest and remnant corridors; conversely, exotic bird abundance was best predicted by overall tree cover throughout the area reforested.

Main conclusions

Our results demonstrate that large‐scale tree planting in corridors adjacent to mature forest can catalyse rapid recovery (both increased abundance and expanded distribution) of forest birds and that it is possible to design reforestation to benefit native species in novel ecosystems.

     

Invasion lags: The stories we tell ourselves and our inability to infer process from pattern

Aim

Many alien species experience a lag phase between arriving in a region and becoming invasive, which can provide a valuable window of opportunity for management. Our ability to predict which species are experiencing lags has major implications for management decisions that are worth billions of dollars and that may determine the survival of some native species. To date, timing and causes of lag and release have been identified post hoc, based on historical narratives.

Location

Global.

Methods

We use a simple but realistic simulation of population spread over a fragmented landscape. To break the invasion lag, we introduce a sudden, discrete change in dispersal.

Results

We show that the ability to predict invasion lags is minimal even under controlled circumstances. We also show a non‐negligible risk of falsely attributing lag breaks to mechanisms based on invasion trajectories and coincidences in timing.

Main conclusions

We suggest that post hoc narratives may lead us to erroneously believe we can predict lags and that a precautionary approach is the only sound management practice for most alien species.

     

Impacts of past habitat loss and future climate change on the range dynamics of South African Proteaceae

Aim

To assess how habitat loss and climate change interact in affecting the range dynamics of species and to quantify how predicted range dynamics depend on demographic properties of species and the severity of environmental change.

Location

South African Cape Floristic Region.

Methods

We use data‐driven demographic models to assess the impacts of past habitat loss and future climate change on range size, range filing and abundances of eight species of woody plants (Proteaceae). The species‐specific models employ a hybrid approach that simulates population dynamics and long‐distance dispersal on top of expected spatio‐temporal dynamics of suitable habitat.

Results

Climate change was mainly predicted to reduce range size and range filling (because of a combination of strong habitat shifts with low migration ability). In contrast, habitat loss mostly decreased mean local abundance. For most species and response measures, the combination of habitat loss and climate change had the most severe effect. Yet, this combined effect was mostly smaller than expected from adding or multiplying effects of the individual environmental drivers. This seems to be because climate change shifts suitable habitats to regions less affected by habitat loss. Interspecific variation in range size responses depended mostly on the severity of environmental change, whereas responses in range filling and local abundance depended mostly on demographic properties of species. While most surviving populations concentrated in areas that remain climatically suitable, refugia for multiple species were overestimated by simply overlying habitat models and ignoring demography.

Main conclusions

Demographic models of range dynamics can simultaneously predict the response of range size, abundance and range filling to multiple drivers of environmental change. Demographic knowledge is particularly needed to predict abundance responses and to identify areas that can serve as biodiversity refugia under climate change. These findings highlight the need for data‐driven, demographic assessments in conservation biogeography.