Consistent life history shifts along invasion routes? An examination of round goby populations invading on two continents

Aim

Many invasive populations exhibit dynamic life history shifts along their invasion route. We investigated whether these shifts represent consistent biological responses of a given species to range expansion, even in systems located in different geographic regions.

Location

North‐eastern France, Central Ontario (Canada).

Method

We investigated population density, life history traits and age‐specific reproductive investment in expanding populations of round goby at three invasion stages (expansion front, area colonized one year earlier and area colonized for ~five years) along the invasive routes in two river systems differing in climate and system productivity. Interindividual variability, shown to affect range expansion rates, was also investigated along the invasion routes. The study was based on female round gobies collected in three locations within each invasion stage twice monthly throughout the reproductive season (March/May to July).

Results

In both systems, reproductive investment was highest in the newly colonized area and decreased with time since colonization. A faster decrease in reproductive investment was found in the warmer, more productive system behind the invasion front, potentially associated with faster population growth and increased intraspecific competition. In both systems, individual variability in growth and reproductive traits increased from the newly colonized area to the areas of earlier colonization.

Main conclusions

The patterns observed in the two systems suggest a common invasion strategy independent of environmental conditions and highlight the dynamic nature of invasive populations’ life history behind the invasion front. Common energetic allocation strategies can be expected at the invasion front. Range expansion may be associated with population growth induced by rapid acclimation to biotic conditions associated with range shift.

     

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.

     

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.

     

Fishing pressure and species traits affect stream fish invasions both directly and indirectly

Aim

We sought to identify direct and indirect effects of factors contributing to establishment and spread of 272 stream fish species.

Location

Two hundred and ninety‐seven watersheds in the eastern United States.

Methods

We modelled two variables: (1) whether a species had become established outside its native range (establishment) and (2) the number of watersheds in which species established outside their native range (spread). We estimated these variables by comparing historical distributions to a rich data set of contemporary sampling. We calculated metrics of human use (indexing propagule pressure), and gathered species trait data from an open‐access database. We then used piecewise path analysis to estimate direct and indirect effects of human use, native range size and species traits on the two metrics of species introductions.

Results

We identified a hierarchical causal structure in which native range size and fishing pressure were important direct determinants of introductions. Species traits had some direct effects, but played a more indirect role. Native range size was significantly affected by thermal tolerance and diet breadth. Likewise, fishing pressure was significantly affected by life history strategy: larger‐bodied, longer‐living and more fecund species were positively associated with fishing pressure.

Main conclusions

Functional traits can confer an advantage to some species during the establishment phase, but human use is important for subsequent dispersal throughout the non‐native range. However, human use is non‐random, and is largely a function of species traits. Considering both direct and indirect effects of traits across stages of the invasion process can help to elucidate the full role of traits in species invasions.

     

Moving from representation to persistence: The capacity of Australia's National Reserve System to support viable populations of mammals

Aim

Species require sufficiently large and connected areas of suitable habitat to support populations that can persist through change. With extensive alteration of unprotected natural habitat, there is increasing risk that protected areas (PAs) will be too small and isolated to support viable populations in the long term. Consequently, this study addresses the urgent need to assess the capacity of PA estates to facilitate species persistence.

Location

Australia.

Methods

We undertake the first assessment of the capacity of the Australian National Reserve System (NRS) to protect 90 mammal species in the long term, given the size and distribution of individual PAs across the landscape relative to species’ habitat and minimum viable area (MVA) requirements and dispersal capabilities.

Results

While all mammal ranges are represented within the NRS, the conservation capacity declined notably when we refined measures of representation within PAs to include species’ habitat and area requirements. The NRS could not support any viable populations for between three and seven species, depending on the MVA threshold used, and could support less than 10 viable populations for up to a third of the species. Planning and managing PAs for persistence emerged as most important for species with large MVA requirements and limited dispersal capabilities.

Main conclusions

The key species characteristics we identify can help managers recognize species at risk within the current PA estate and guide the types of strategies that would best reduce this risk. We reveal that current representation‐based assessments of PA progress are likely to overestimate the long‐term success of PA estates, obscuring vulnerabilities for many species. It is important that conservation planners and managers are realistic and explicit regarding the role played by different sizes and distributions of PAs, and careful in assuming that the representation of a species within a PA equates to its long‐term conservation.

     

Immigrant and native? The case of the swamp foxtail Cenchrus purpurascens in Australia

Aim

Spring wetlands in arid regions of Australia provide habitat for many highly endemic organisms, including fish, molluscs, crustaceans and plants, but these unique ecosystems have been under pressure since the arrival of Europeans about 250 years ago. Arguments over whether particular plant species are long‐term spring inhabitants or recent immigrants are confounding efforts to conserve spring flora. One such example is the swamp foxtail, Cenchrus purpurascens, a grass that is variably listed in the literature as being native to Australian wetlands or as being an introduced weedy species from Asia.

Location

Australia, China and Korea.

Methods

We use DNA sequences of the nuclear ITS and the chloroplast DNA regions trnL‐F and matK, complemented with newly designed simple sequence repeat (SSR) markers, to assess the native status of C. purpurascens in Australia and determine whether there is genetic differentiation among spring populations.

Results

We find that, although there has been gene flow between Asia and Australia in the geological past, the populations are now strongly differentiated: C. purpurascens has probably been present in Australia through the Pleistocene. In Australia, there is also strong genetic differentiation among populations from different springs, and between springs and non‐springs populations, indicating long‐term occupancy of some springs sites.

Main conclusions

Cenchrus purpurascens was present in Australia well before European colonization of the continent. The level of genetic differentiation among populations enhances the existing conservation values of Elizabeth Springs, Edgbaston, Doongmabulla and Carnarvon Gorge springs complexes within the Great Artesian Basin.

     

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.

     

Standardized genetic diversity‐life history correlates for improved genetic resource management of Neotropical trees

Aim

Life history traits and range size are key correlates of genetic diversity in trees. We used a standardized sampling protocol to explore how life history traits and range size relate to the magnitude, variance and structuring (both between‐ and within‐population) of genetic diversity in Neotropical tree species.

Location

The Neotropics

Methods

We present a meta‐analysis of new population genetic data generated for 23 Neotropical tree species (=2,966 trees, 86 populations) across a shared and broad geographic area. We compared established population genetic metrics across these species (e.g., genetic diversity, population structure, fine‐scale genetic structure), plus we estimated the rarely used variance in genetic diversity among populations. We used a multivariate, maximum likelihood, multimodel inference approach to explore the relative influence of life history traits and range size on patterns of neutral genetic diversity.

Results

We found that pioneer and narrow range species had lower levels but greater variance in genetic diversity—signs of founder effects and stronger genetic drift. Animal‐dispersed species had lower population differentiation, indicating extensive gene flow. Abiotically dispersed and pioneer species had stronger fine‐scale genetic structure, suggesting restricted seed dispersal and family cohort establishment.

Main conclusions

Our multivariable and multispecies approach allows ecologically relevant conclusions, since knowing whether one parameter has an effect, or one species shows a response in isolation, is dependent on the combination of traits expressed by a species. Our study demonstrates the influence of ecological processes on the distribution of genetic variation in tropical trees, and will help guide genetic resource management, and contribute to predicting the impacts of land use change.

     

Chasing a changing climate: Reproductive and dispersal traits predict how sessile species respond to global warming

Aim

Studies of species' range shifts have become increasingly relevant for understanding ecology and biogeography in the face of accelerated global change. The combination of limited mobility and imperilled status places some species at a potentially greater risk of range loss, extirpation or extinction due to climate change. To assess the ability of organisms with limited movement and dispersal capabilities to track shifts associated with climate change, we evaluated reproductive and dispersal traits of freshwater mussels (Unionida), sessile invertebrates that require species‐specific fish for larval dispersal.

Location

North American Atlantic Slope rivers.

Methods

To understand how unionid mussels may cope with and adapt to current and future warming trends, we identified mechanisms that facilitated their colonization of the northern Atlantic Slope river basins in North America after the Last Glacial Maximum. We compiled species occurrence and life history trait information for each of 55 species, and then selected life history traits for which ample data were available (larval brooding duration, host fish specificity, host infection strategy, and body size) and analysed whether the trait state for each was related to mussel distribution in Atlantic Slope rivers.

Results

Brooding duration (p < .01) and host fish specificity (p = .02) were significantly related to mussel species distribution. Long‐term brooders were more likely than short‐term brooders to colonize formerly glaciated rivers, as were host generalists compared to specialists. Body size and host infection strategy were not predictive of movement into formerly glaciated rivers (p > .10).

Main conclusions

Our results are potentially applicable to many species for which life history traits have not been well‐documented, because reproductive and dispersal traits in unionid mussels typically follow phylogenetic relationships. These findings may help resource managers prioritize species according to climate change vulnerability and predict which species might become further imperilled with climate warming. Finally, we suggest that similar trait‐based decision support frameworks may be applicable for other movement limited taxa.

     

Old‐growth forests buffer climate‐sensitive bird populations from warming

Aim

Habitat loss and climate change constitute two of the greatest threats to biodiversity worldwide, and theory predicts that these factors may act synergistically to affect population trajectories. Recent evidence indicates that structurally complex old‐growth forest can be cooler than other forest types during spring and summer months, thereby offering potential to buffer populations from negative effects of warming. Old growth may also have higher food and nest‐site availability for certain species, which could have disproportionate fitness benefits as species approach their thermal limits.

Location

Pacific Northwestern United States.

Methods

We predicted that negative effects of climate change on 30‐year population trends of old‐growth‐associated birds should be dampened in landscapes with high proportions of old‐growth forest. We modelled population trends from Breeding Bird Survey data for 13 species as a function of temperature change and proportion old‐growth forest.

Results

We found a significant negative effect of summer warming on only two species. However, in both of these species, this relationship between warming and population decline was not only reduced but reversed, in old‐growth‐dominated landscapes. Across all 13 species, evidence for a buffering effect of old‐growth forest increased with the degree to which species were negatively influenced by summer warming.

Main conclusions

These findings suggest that old‐growth forests may buffer the negative effects of climate change for those species that are most sensitive to temperature increases. Our study highlights a mechanism whereby management strategies to curb degradation and loss of old‐growth forests—in addition to protecting habitat—could enhance biodiversity persistence in the face of climate warming.

     

Contrasting climate niches among co‐occurring subdominant forbs of the sagebrush steppe

Aim

Abiotic conditions are key components that determine the distribution of species. However, co‐occurring species can respond differently to the same factors, and determining which climate components are most predictive of geographic distributions is important for understanding community response to climate change. Here, we estimate and compare climate niches of ten subdominant, herbaceous forb species common in sagebrush steppe systems, asking how niches differ among co‐occurring species and whether more closely related species exhibit higher niche overlap.

Location

Western United States.

Methods

We used herbarium records and ecological niche modelling to estimate area of occupancy, niche breadth and overlap, and describe characteristics of suitable climate. We compared mean values and variability in summer precipitation and minimum temperatures at occurrence locations among species, plant families, and growth forms, and related estimated phylogenetic distances to niche overlap.

Results

Species varied in the size and spatial distribution of suitable climate and in niche breadth. Species also differed in the variables contributing to their suitable climate and in mean values, spatial variation and interannual variation in highly predictive climate variables. Only two of ten species shared comparable climate niches. We found family‐level differences associated with variation in summer precipitation and minimum temperatures, as well as in mean minimum temperatures. Growth forms differed in their association with variability in summer precipitation and minimum temperatures. We found no relationship between phylogenetic distance and niche overlap among our species.

Main conclusions

We identified contrasting climate niches for ten Great Basin understorey forbs, including differences in both mean values and climate variability. These estimates can guide species selection for restoration by identifying species with a high tolerance for climate variability and large climatic niches. They can also help conservationists to understand which species may be least tolerant of climate variability, and potentially most vulnerable to climate change.

     

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.

     

Species traits suggest European mammals facing the greatest climate change are also least able to colonize new locations

Aim

The risk climate change poses to biodiversity is often estimated by forecasting the areas that will be climatically suitable for species in the future and measuring the distance of the “range shifts” species would have to make to reach these areas. Species’ traits could indicate their capacity to undergo range shifts. However, it is not clear how range‐shift capacity influences risk. We used traits from a recent evidence review to measure the relative potential of species to track changing climatic conditions.

Location

Europe.

Time period

Baseline period (1961–1990) and forecast period (2035–2064).

Major taxa studied

62 mammal species.

Methods

We modelled species distributions using two general circulation models and two representative concentration pathways (RCPs) to calculate three metrics of “exposure” to climate change: range area gained, range area lost and distance moved by the range margin. We identified traits that could inform species’ range‐shift capacity (i.e., potential to establish new populations and proliferate, and thus undertake range shifts), from a recent evidence‐based framework. The traits represent ecological generalization and reproductive strategy. We ranked species according to each metric of exposure and range‐shift capacity, calculating sensitivity to ranking methods, and synthesized both exposure and range‐shift capacity into “risk syndromes.”

Results

Many species studied whose survival depends on colonizing new areas were relatively unlikely to undergo range shifts. Under the worst‐case scenario, 62% of species studied were relatively highly exposed. 47% were highly exposed and had relatively low range‐shift capacity. Only 14% of species faced both low exposure and high range‐shift capacity. Both range‐shift and exposure metrics had a greater effect on risk assessments than climate models.

Main conclusions

The degree to which species’ potential ranges will be altered by climate change often does not correspond to species’ range‐shift capacities. Both exposure and range‐shift capacity should be considered when evaluating biodiversity risk from climate change.

     

Modelling the distribution and compositional variation of plant communities at the continental scale

Aim

We investigate whether (1) environmental predictors allow to delineate the distribution of discrete community types at the continental scale and (2) how data completeness influences model generalization in relation to the compositional variation of the modelled entities.

Location

Europe.

Methods

We used comprehensive datasets of two community types of conservation concern in Europe: acidophilous beech forests and base‐rich fens. We computed community distribution models (CDMs) calibrated with environmental predictors to predict the occurrence of both community types, evaluating geographical transferability, interpolation and extrapolation under different scenarios of sampling bias. We used generalized dissimilarity modelling (GDM) to assess the role of geographical and environmental drivers in compositional variation within the predicted distributions.

Results

For the two community types, CDMs computed for the whole study area provided good performance when evaluated by random cross‐validation and external validation. Geographical transferability provided lower but relatively good performance, while model extrapolation performed poorly when compared with interpolation. Generalized dissimilarity modelling showed a predominant effect of geographical distance on compositional variation, complemented with the environmental predictors that also influenced habitat suitability.

Main conclusions

Correlative approaches typically used for modelling the distribution of individual species are also useful for delineating the potential area of occupancy of community types at the continental scale, when using consistent definitions of the modelled entity and high data completeness. The combination of CDMs with GDM further improves the understanding of diversity patterns of plant communities, providing spatially explicit information for mapping vegetation diversity and related habitat types at large scales.

     

Zero‐sum landscape effects on acorn predation associated with shifts in granivore insect community in new holm oak (Quercus ilex) forests

Aim

Landscape attributes can determine plant–animal interactions via effects on the identity and abundance of the involved species. As most studies have been conducted in a context of habitat loss and fragmentation, we know very little about interaction assembly in new habitats from a landscape approach. This study aimed to test the effect of forest age and connectivity on acorn predation by a guild of predator insects differing in dispersal ability and resilience mechanisms: two weevils (Curculio elephas and C. glandium) and one moth (Cydia fagiglandana) in expanding Quercus ilex forests.

Location

Barcelona, Spain.

Methods

We assessed the proportion of infested acorns and identified the predator at the species level in five patches of connected old forests, connected new forests and isolated new forests. Effects of habitat age and connectivity at three scales (tree, patch and landscape) were analysed using generalized linear mixed‐effects models.

Results

Predation by weevils was positively associated with old connected forests, while moths, with better dispersal ability, were able to predate upon all patches equally. Moreover, C. elephas, the weevil with lower dispersal ability, exhibited colonization credits in the new isolated patches. In spite of these changes in the guild of seed predators, the proportion of infested acorns was non‐significantly different among forests.

Main conclusions

The guild of seed predators may vary depending on forest age and connectivity. However, because those with higher dispersal ability may replace less mobile species, this resulted in zero‐sum effects of landscape attributes on acorn predation (i.e., similar predation rates in well‐connected old forests vs. isolated new forests).

     

Propagule pressure and land cover changes as main drivers of red and roe deer expansion in mainland Portugal

Aim

The management of the rapid expansion of wild ungulate populations is a challenging task and a societal priority. Using a progressive database of red (Cervus elaphus) and roe (Capreolus capreolus) deer colonization over the last three decades, we estimate the range expansion rates and the underlying mechanisms involved in the expansion patterns of red and roe deer populations at the south‐western edge of its European distribution.

Location

Mainland Portugal.

Methods

We compiled and grouped historical red and roe deer distribution data in three time periods (1981–1990, 1991–2000 and 2001–2010). We used generalized linear mixed models to evaluate how biotic and abiotic drivers determine the expansion patterns of red and roe deer.

Results

We reported a significant expansion of red and roe deer populations during the last three decades. The significant interaction between propagule pressure and land cover suggests that the effects of propagule pressure vary along environmental gradients. We found that the influence of livestock on red and roe deer expansion is idiosyncratic. Contrary to red deer, roe deer expansion was also influenced by climatic conditions. We did not detect any significant effect of human factors on the red and roe deer expansion.

Main conclusions

The synergistic effects between variables should be taken into account when studying the patterns of species expansion. Our study emphasize that policy makers should consider the spatial, temporal, ecological and societal nuances of species expansion in order to prioritize management measures and to allocate management budgets. Although concerted strategies to curtail species spread should mitigate red and roe deer economic and ecological impacts, these effects can be neutralized by a continuous rural exodus and the consequent forest and shrub encroachment.

     

Predicting distributions,habitat preferences and associated conservation implications for a genus of rare fishes,seahorses (Hippocampus spp.)

Aim

To identify useful sources of species data and appropriate habitat variables for species distribution modelling on rare species, with seahorses as an example, deriving ecological knowledge and spatially explicit maps to advance global seahorse conservation.

Location

The shallow seas.

Methods

We applied a typical species distribution model (SDM), maximum entropy, to examine the utility of (1) two versions of habitat variables (habitat occurrences vs. proximity to habitats) and (2) three sources of species data: quality research‐grade (RG) data, quality‐unknown citizen science (CS) and museum‐collection (MC) data. We used the best combinations of species data and habitat variables to predict distributions and estimate species–habitat relations and threatened status for seahorse species.

Results

We demonstrated that using “proximity to habitats” and integrating all species datasets (RG, CS and MC) derived models with the highest accuracies among all dataset variations. Based on this finding, we derived reliable models for 33 species. Our models suggested that only 0.4% of potential seahorse range was suitable to more than three species together; seahorse biogeographic epicentres were mainly in the Philippines; and proximity to sponges was an important habitat variable. We found that 12 “Data Deficient” species might be threatened based on our predictions according to IUCN criteria.

Main conclusions

We highlight that using proper habitat variables (e.g., proximity to habitats) is critical to determine distributions and key habitats for low‐mobility animals; collating and integrating quality‐unknown occurrences (e.g., CS and MC) with quality research data are meaningful for building SDMs for rare species. We encourage the application of SDMs to estimate area of occupancy for rare organisms to facilitate their conservation status assessment.

     

Transport pathways shape the biogeography of alien freshwater fishes in Australia

Aim

Changing preferences regarding which species humans have transported to new regions can have major consequences for the potential distribution of alien taxa, but the mechanisms shaping these patterns are poorly understood. We assessed the extent to which changes in human preferences for transporting and introducing alien freshwater fishes have altered their biogeography.

Location

Australia.

Methods

We compiled an up‐to‐date database of alien freshwater fishes established in drainages in Australia before and after the number of established alien fish species doubled (pre‐1970 and post‐1970, respectively). Using metacommunity models, we analysed the influence of species traits and drainage features on the distribution of alien fishes that established pre‐ and post‐1970.

Results

Alien fishes in Australia were introduced via four main transport pathways: acclimatization, aquaculture, biocontrol and ornamental trade. The relative importance of each pathway changed substantially between the two periods, accompanied by changes in the distribution of alien fishes and the variables predicting their distribution. Pre‐1970, most species (64%) were introduced by acclimatization societies for purposes such as angling and biocontrol, and these fish have established in inland drainages more heavily impacted by human activities. In contrast, most of the post‐1970 introductions (69%) were ornamental fishes, with most species established in small, north‐eastern, tropical and subtropical coastal drainages.

Main conclusions

Substantial changes in introduction preferences and transport pathways over time have altered both the patterns and underlying processes shaping the biogeography of alien fishes in Australia. Our findings highlight the need for caution when using historical data to infer potential future distributions of alien species. The continuing spread of alien species means traditional biogeographical units may no longer be identifiable in the foreseeable future.

     

Combining point‐process and landscape vegetation models to predict large herbivore distributions in space and time—A case study of Rupicapra rupicapra

Aim

When modelling the distribution of animals under current and future conditions, both their response to environmental constraints and their resources’ response to these environmental constraints need to be taken into account. Here, we develop a framework to predict the distribution of large herbivores under global change, while accounting for changes in their main resources. We applied it to Rupicapra rupicapra, the chamois of the European Alps.

Location

The Bauges Regional Park (French Alps).

Methods

We built sixteen plant functional groups (PFGs) that account for the chamois’ diet (estimated from sequenced environmental DNA found in the faeces), climatic requirements, dispersal limitations, successional stage and interaction for light. These PFGs were then simulated using a dynamic vegetation model, under current and future climatic conditions up to 2100. Finally, we modelled the spatial distribution of the chamois under both current and future conditions using a point‐process model applied to either climate‐only variables or climate and simulated vegetation structure variables.

Results

Both the climate‐only and the climate and vegetation models successfully predicted the current distribution of the chamois species. However, when applied into the future, the predictions differed widely. While the climate‐only models predicted an 80% decrease in total species occupancy, including vegetation structure and plant resources for chamois in the model provided more optimistic predictions because they account for the transient dynamics of the vegetation (?20% in species occupancy).

Main conclusions

Applying our framework to the chamois shows that the inclusion of ecological mechanisms (i.e., plant resources) produces more realistic predictions under current conditions and should prove useful for anticipating future impacts. We have shown that discounting the pure effects of vegetation on chamois might lead to overpessimistic predictions under climate change. Our approach paves the way for improved synergies between different fields to produce biodiversity scenarios.

     

Prioritizing refugia for freshwater biodiversity conservation in highly seasonal ecosystems

Aim

Refugia play a key ecological role for the persistence of biodiversity in areas subject to natural or human disturbance. Temporary freshwater ecosystems regularly experience dry periods, which constrain the availability of suitable habitats. Current and future threats (e.g. water extraction and climate change) can exacerbate the negative effects of drying conditions. This could compromise the persistence of a large proportion of global freshwater biodiversity, so the identification and protection of refugia seems an urgent task.

Location

Northern Australia.

Methods

We demonstrate a new approach to identify and prioritize the selection of refugia and apply it to the conservation of freshwater fish biodiversity. We identified refugia using estimates of water residency time derived from satellite imagery and used a systematic approach to prioritize areas that provide all the fish species inhabiting the catchment with access to a minimum number of refugia while maximizing the length of stream potentially accessible for recolonization after the dry period. These priority refugia were locked into a broader systematic conservation plan with area‐based targets and direct connectivity. We accounted for current threats during the prioritization process to ensure degraded areas were avoided, thus maximizing the ecological role of priority refugia.

Results

Priority refugia were located in lowland reaches, where the incidence of threats was less prominent in our study area and headwaters in good condition. An additional set of 106 planning units (6500 km²) were required to represent 10% of each species' distribution in the broad conservation plan. A hierarchical management zoning scheme was applied to demonstrate how these key ecological features could be effectively protected from the major threats caused by aquatic invasive species and grazing.

Main conclusions

This new approach to identifying priority refugia and incorporating them into the conservation planning process in a systematic way would help enhance the resilience of freshwater biodiversity in temporary systems.