Joint effects of species traits and environmental preferences on range edge shifts of British birds

Aim

Despite the strong evidence of species range shifts as a response to environmental change, attempts to identify species traits that modulate those shifts have been equivocal. We investigate the role of species traits and environmental preferences on birds' range shifts in Great Britain, an island where dispersal is limited by the English Channel and the North Sea.

Location

Great Britain (England, Scotland and Wales).

Taxa

Birds (Aves).

Time Period

1968–2011.

Methods

Using 404,949 occurrence records from two time periods, we investigated the potential drivers of leading and rear range edge shifts of breeding birds using phylogenetic linear mixed models. We hypothesized that shifts are influenced by species' trophic and morphological traits, dispersal abilities and environmental preferences, but also by the geographical boundaries of Great Britain.

Results

Geographical boundaries—the distance from the northern or southern boundaries of Britain—accounted for most of the variability in range edge shifts. Species traits and environmental preferences emerged as relevant drivers of range shifts only for northern and Passeriform species. Northern habitat specialist, those with more predators and those sensitive to precipitation were more likely to shift their rear edge poleward. For Passeriformes, habitat generalists, species with smaller dispersal capabilities, under higher predatory pressure or associated with forest and grassland were more likely to shift their rear edge poleward.

Main Conclusions

While geographical boundaries impose constraints on range shifts in British birds, the subtle effects of species traits and environmental preferences emerge as relevant predictors for Northern and passeriform species' rear edge shifts. This highlights the importance of accounting for geographical boundaries when predicting species responses to global change. Differential range shifts of species across different trophic levels could result in the reorganization of biotic interactions, with consequences for ecosystem structure and stability.     

Threatened fish species in the Northeast Atlantic are functionally rare

Aim

The criteria used to define the International Union for Conservation of Nature (IUCN) Red List categories are essentially based on demographic parameters at the species level, but they do not integrate species' traits or their roles in ecosystems. Consequently, current IUCN-based protection measures may not be sufficient to conserve ecosystem functioning and services. Some species may have a singular combination of traits associated with unique functions. Such functionally distinct species are increasingly recognized as a key facet of biodiversity since they are, by definition, functionally irreplaceable. The aim of this study is to investigate whether threatened species are also functionally rare and to identify which traits determine extinction risk.

Location

European continental shelf seas.

Time period

1984–2020.

Major taxa studied

Marine fish.

Methods

Using newly compiled trait information of 425 marine fish species in European waters, and more than 30 years of scientific bottom trawl surveys, we estimated the functional distinctiveness, restrictedness and scarcity of each species and cross-referenced it with their IUCN conservation status.

Results

In European continental shelf seas, 38% of the species threatened with extinction (9 out of 24 species) were identified as the most functionally distinct. By mapping extinction risk in the multidimensional species trait space, we showed that species with the greatest risk of extinction are long-lived and of high trophic level. We also identified that the most functionally distinct species are sparsely distributed (4% of the total area on average) and have scarce abundances (<1% of the relative mean abundance of common species).

Main Conclusions

Because a substantial proportion of threatened species are functionally distinct and thus may play unique roles in ecosystem functioning, we stress that species traits—especially functional rarity—should become an indispensable step in the development of conservation management plans.     

Characteristics of Australia's alien flora vary with invasion stage

Aim

Directly or indirectly, humans select the plants that they transport and introduce outside of species native ranges. Plants that have become invasive may therefore reflect which species had the chance to invade, rather than which species would become invasive given the chance. We examine characteristics of failed introductions, along with invasion successes, by investigating (a) variation in plant characteristics across invasion stages, and (b) how observed characteristics predict the likelihood of species moving through invasion stages.

Location

Australia.

Time period

1770s to present.

Major taxa studied

34,650 plant species, across 424 families.

Methods

We used a comprehensive list of 34,650 plant species that are known to have been introduced to Australia, 4,081 of which are classified as naturalized and 428 as invasive. We represent plant characteristics with categorical growth forms, three functional traits (plant height, seed mass, and specific leaf area) and three factors related to species introduction histories (native regions, purpose, and minimum residence times).

Results

(a) The types of species introduced determine the types of species that naturalize and become invasive; (b) species introduction histories predict the likelihood of species moving through invasion stages; and (c) the numbers of species naturalizing (~15%) and becoming invasive (~15%) slightly exceeds expectation from the “tens rule”, which expects that 10% of introduced species naturalize and 10% become invasive.

Main conclusions

Our findings are significant for global biosecurity, indicating that functional traits alone cannot be used to predict a species' risk of becoming invasive. Rather, evidence suggests that characteristics of species introductions—specifically, a longer time-lag since first introduction and more pathways of introduction—define the relative risks of species moving through invasion stages. This is important for assessing future invasion risks, as future introductions may differ from those of the past. Our work highlights the need to reduce the number of species introduced.     

Relationship between leaf traits and fire-response strategies in shrub species of a mountainous region of south-eastern Australia

Background and Aims

Resprouting and seed recruitment are important ways in which plants respond to fire. However, the investments a plant makes into ensuring the success of post-fire resprouting or seedling recruitment can result in trade-offs that are manifested in a range of co-occurring morphological, life history and physiological traits. Relationships between fire-response strategies and other traits have been widely examined in fire-prone Mediterranean-type climates. In this paper, we aim to determine whether shrubs growing in a non-Mediterranean climate region exhibit relationships between their fire-response strategy and leaf traits.

Methods

Field surveys were used to classify species into fire-response types. We then compared specific leaf area, leaf dry-matter content, leaf width, leaf nitrogen and carbon to nitrogen ratios between (a) obligate seeders and all other resprouters, and (b) obligate seeders, facultative resprouters and obligate resprouters.

Key Results

Leaf traits only varied between fire-response types when we considered facultative resprouters as a separate group to obligate resprouters, as observed after a large landscape-scale fire. We found no differences between obligate seeders and obligate resprouters, nor between obligate seeders and resprouters considered as one group.

Conclusions

The results suggest that facultative resprouters may require a strategy of rapid resource acquisition and fast growth in order to compete with species that either resprout, or recruit from seed. However, the overall lack of difference between obligate seeders and obligate resprouters suggests that environmental factors are exerting similar effects on species'' ecological strategies, irrespective of the constraints and trade-offs that may be associated with obligate seeding and obligate resprouting. These results highlight the limits to trait co-occurrences across different ecosystems and the difficulty in identifying global-scale relationships amongst traits.     

The influence of floral symmetry,dependence on pollinators and pollination generalization on flower size variation

Background and Aims

The pollinator-mediated stabilizing selection hypothesis suggests that the specialized pollination system of zygomorphic flowers might cause stabilizing selection, reducing their flower size variation compared with actinomorphic flowers. However, the degree of ecological generalization and of dependence on pollinators varies greatly among species of both flower symmetry types and this may also affect flower size variation.

Methods

Data on 43 species from two contrasting communities (one alpine and one lowland community) were used to test the relationships and interactions between flower size phenotypic variation, floral symmetry, ecological pollination generalization and species'' dependence on pollinators.

Key Results

Contrary to what was expected, higher flower size variation was found in zygomorphic than in actinomorphic species in the lowland community, and no difference in flower size variation was found between symmetry types in the alpine community. The relationship between floral symmetry and flower size variation depended on ecological generalization and species'' dependence on pollinators, although the influence of ecological generalization was only detected in the alpine community. Zygomorphic species that were highly dependent on pollinators and that were ecologically specialized were less variable in flower size than ecologically generalist and selfing zygomorphic species, supporting the pollinator-mediated stabilizing selection hypothesis. However, these relationships were not found in actinomorphic species, probably because they are not dependent on any particular pollinator for efficient pollination and therefore their flower size always shows moderate levels of variation.

Conclusions

The study suggests that the relationship between flower size variation and floral symmetry may be influenced by population-dependent factors, such as ecological generalization and species'' dependence on pollinators.     

Extinction risk of Chinese angiosperms varies between woody and herbaceous species

Aim

Understanding how species' traits and environmental contexts relate to extinction risk is a critical priority for ecology and conservation biology. This study aims to identify and explore factors related to extinction risk between herbaceous and woody angiosperms to facilitate more effective conservation and management strategies and understand the interactions between environmental threats and species' traits.

Location

China.

Taxon

Angiosperms.

Methods

We obtained a large dataset including five traits, six extrinsic variables, and 796,118 occurrence records for 14,888 Chinese angiosperms. We assessed the phylogenetic signal and used phylogenetic generalized least squares regressions to explore relationships between extinction risk, plant traits, and extrinsic variables in woody and herbaceous angiosperms. We also used phylogenetic path analysis to evaluate causal relationships among traits, climate variables, and extinction risk of different growth forms.

Results

The phylogenetic signal of extinction risk differed among woody and herbaceous species. Angiosperm extinction risk was mainly affected by growth form, altitude, mean annual temperature, normalized difference vegetation index, and precipitation change from 1901 to 2020. Woody species' extinction risk was strongly affected by height and precipitation, whereas extinction risk for herbaceous species was mainly affected by mean annual temperature rather than plant traits.

Main conclusions

Woody species were more likely to have higher extinction risks than herbaceous species under climate change and extinction threat levels varied with both plant traits and extrinsic variables. The relationships we uncovered may help identify and protect threatened plant species and the ecosystems that rely on them.     

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.

     

Clonal growth and plant species abundance

Background and Aims

Both regional and local plant abundances are driven by species'' dispersal capacities and their abilities to exploit new habitats and persist there. These processes are affected by clonal growth, which is difficult to evaluate and compare across large numbers of species. This study assessed the influence of clonal reproduction on local and regional abundances of a large set of species and compared the predictive power of morphologically defined traits of clonal growth with data on actual clonal growth from a botanical garden. The role of clonal growth was compared with the effects of seed reproduction, habitat requirements and growth, proxied both by LHS (leaf–height–seed) traits and by actual performance in the botanical garden.

Methods

Morphological parameters of clonal growth, actual clonal reproduction in the garden and LHS traits (leaf-specific area – height – seed mass) were used as predictors of species abundance, both regional (number of species records in the Czech Republic) and local (mean species cover in vegetation records) for 836 perennial herbaceous species. Species differences in habitat requirements were accounted for by classifying the dataset by habitat type and also by using Ellenberg indicator values as covariates.

Key Results

After habitat differences were accounted for, clonal growth parameters explained an important part of variation in species abundance, both at regional and at local levels. At both levels, both greater vegetative growth in cultivation and greater lateral expansion trait values were correlated with higher abundance. Seed reproduction had weaker effects, being positive at the regional level and negative at the local level.

Conclusions

Morphologically defined traits are predictive of species abundance, and it is concluded that simultaneous investigation of several such traits can help develop hypotheses on specific processes (e.g. avoidance of self-competition, support of offspring) potentially underlying clonal growth effects on abundance. Garden performance parameters provide a practical approach to assessing the roles of clonal growth morphological traits (and LHS traits) for large sets of species.     

Anthropogenous areal extension of central European woody species on the British Isles and its significance for the judgement of the present potential natural vegetation

Several central European species have failed to reach the British Isles because of the early separation from the continent. The two tree species Fagus sylvatica and Carpinus betulus reached southern England but were unable to spread much further. Other species, such as Acer pseudoplatanus, were only relatively recently introduced. Recent distribution maps for Fagus and Acer show an almost uninterrupted distribution in the whole British Isles. The beech must be considered to be an important element of the present potential natural vegetation; it has been planted widely and regenerates freely. The woodlands of Brittany may provide a model to enable us to visualize the possible species composition and appearance of these potential Atlantic beech woods.Nomenclature of vascular taxa follows Ehrendorfer (1973).     

When is a native species invasive? Incursion of a novel predatory marsupial detected using molecular and historical data

Aim

Range expansions facilitated by humans or in response to local biotic or abiotic stressors provide the opportunity for species to occupy novel environments. Classifying the status of newly expanded populations can be difficult, particularly when the timing and nature of the range expansion are unclear. Should native species in new habitats be considered invasive pests or actively conserved? Here, we present an analytical framework applied to an Australian marsupial, the sugar glider (Petaurus breviceps), a species that preys upon on an endangered parrot in Tasmania, and whose provenance was uncertain.

Location

Tasmania, Australia.

Methods

We conducted an extensive search of historical records for sugar glider occurrences in Tasmania. Source material included museum collection data, early European expedition logs, community observation records, and peer‐reviewed and grey literature. To determine the provenance of the Tasmanian population, we sequenced two mitochondrial genes and one nuclear gene in Tasmanian animals (n = 27) and in individuals across the species' native range. We then estimated divergence times between Tasmania and southern Australian populations using phylogenetic and Bayesian analyses.

Results

We found no historical evidence of sugar gliders occurring in Tasmania prior to 1835. All Tasmanian individuals (n = 27) were genetically identical at the three genes surveyed here with those individuals being 0.125% divergent from individuals from a population in Victoria. Bayesian analysis of divergence between Tasmanian individuals and southern Australian individuals suggested a recent introduction of sugar gliders into Tasmania from southern Australia.

Main conclusions

Molecular and historical data demonstrate that Tasmanian sugar gliders are a recent, post‐European, anthropogenic introduction from mainland Victoria. This result has implications for the management of the species in relation to their impact on an endangered parrot. The analytical framework outlined here can assist environmental managers with the complex task of assessing the status of recently expanded or introduced native species.

     

Life History Differences between Rare and Common Flowering Plant Species of California and the British Isles

Generalizations about rare and endangered species are important for the development of conservation management policy and for understanding of the nature of rarity. Therefore, we sought such generalizations by statistically comparing eight life history and reproductive traits of rare and common plant species in two better-studied but climatically and geographically distinct Holarctic floras-those of California and the British Isles. Trends were often similar in both floras. Rare and common species differ significantly for a number of characters. In both floras, a woody habit was significantly more frequent for the rare species than the common species. Also, in both floras, monocarpy was less frequent in the rare species, significantly so in California. The rare species of both floras were, on average, significantly shorter in stature than the common species. This trend in stature remained significant when nonwoody species were compared but did not do so for woody species. Rare and common species differed with regard to their frequency of inflorescence structure types, but these differences were not concordant for both floras. The rare species of the British Isles had significantly higher proportions of mixed and polymorphic flower colors; the trend was not significant in California. In both floras, rare species had a higher frequency of many-seeded fruits, significantly so in California. California's rare species had a significantly higher frequency of dehiscent fruits than common species; the trend was reversed and not significant for the British Isles. We found no significant differences for characters associated with fruit dispersal. Finally, in California, the median altitude of the range of the common species was significantly greater than that of the rare species. At present, these correlates cannot be assigned as possible causes or consequences of rarity. Nonetheless, they may represent "high-risk" traits that could be used to identify other species already at risk or potentially at risk of becoming rarer.     

Species distribution and crown decline are associated with contrasting water relations in four common sympatric eucalypt species in southwestern Australia

Background and aims

Drought-associated vegetation declines are increasingly observed worldwide. We investigated whether differences in water relations can potentially explain the distribution and vulnerability to drought-induced decline of four common tree species in Mediterranean southwestern Australia.

Methods

We compared seasonal and daily water relations of four eucalypt species (i.e. C. calophylla, E. accedens, E. marginata, E. wandoo) when co-occurring as well as on nearby typical sites for each species.

Results

When co-occurring, species generally inhabiting drier regions (i.e. E. accedens, E. wandoo) had lower summer leaf water potentials, osmotic potential, and vulnerability to cavitation and higher stomatal conductance and relative sapflow velocity. Both wetter zone species (e.g. C. calophylla and E. marginata) had remarkably high vulnerabilities to cavitation for Mediterranean woody species but showed greatly improved leaf water status on nearby sites where they dominate. Using local soil moisture retention curves of saprolitic clay layers underlying southwestern Australia we show the large disadvantage that the wetter zone species have in terms of accessing tightly bound water in these layers.

Conclusions

Our work shows that species distribution and local dominance of four dominant overstorey species in southwestern Australia is largely a function of plant water relations interacting with local soil profiles. The observed differences in water relations amongst species are consistent with some of the declines that have been observed in recent decades.     

Traits help explain species' performance away from their climate niche centre

Aim

Climate change impacts on biota are variable across sites, among species and throughout individual species' ranges. Niche theory predicts that population performance should decline as site climate becomes increasingly different from the species' climate niche centre, though studies find significant variation from these predictions. Here, we propose that predictions about climate responses can be improved by incorporating species' trait information.

Location

Europe.

Methods

We used observations of plant species abundance change over time to assess variation in climate difference sensitivity (CDS), defined as how species performance (colonization, extinction and abundance change) relates to the difference of site climate from the mean temperature and precipitation of each species' range. We then investigated if leaf economics, plant size and seed mass traits were associated with the species' CDS.

Results

Species that performed better (e.g. increased in abundance) towards sites progressively cooler than their niche centre were shorter and had more resource-acquisitive leaves (i.e. lower leaf dry matter content or LDMC) relative to species with zero or the opposite pattern of temperature difference sensitivity. This result supports the hypothesis that if sites cooler than niche centres are more stressful for a species, then shorter stature is advantageous compared with taller species. The LDMC result suggests the environment selects for more resource-acquisitive leaf strategies towards relatively cooler climates with shorter growing seasons, counter to expectations that conservative strategies would be favoured in such environments. We found few consistent relationships between precipitation difference sensitivities and traits.

Main Conclusions

The results supported key a priori foundations on how trait-based plant strategies dictate species responses to climate variation away from their niche centre. Furthermore, plant height emerged as the most consistent trait that varied with species CDS, suggesting height will be key for theory development around species response to climate change.     

The scarcer freshwater fishes of the British Isles

This, the first of two papers on the scarcer freshwater fishes of the British Isles, gives an account of the introduced species. Nineteen species are included. The natural distribution of these fishes, the history of their introduction, their success in acclimatization, and their present distribution in the British Isles are given. A brief discussion on the introduction of exotic fishes to aquatic ecosystems follows.     

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.

     

Distribution of cryptic blue oat mite species in Australia: current and future climate conditions

• 1 Invertebrate pests, such as blue oat mites Penthaleus spp., cause significant economic damage to agricultural crops in Australia. Climate is a major driver of invertebrate species distributions and climate change is expected to shift pest assemblages and pest prevalence across Australia. At this stage, little is known of how individual species will respond to climate change.
• 2 We have mapped the current distribution for each of the three pest Penthaleus spp. in Australia and built ecological niche models for each species using the correlative modelling software, maxent . Predictor variables useful for describing the climate space of each species were determined and the models were projected into a range of future climate change scenarios to assess how climate change may alter species‐specific distribution patterns in Australia.
• 3 The distributions of the three cryptic Penthaleus spp. are best described with different sets of climatic variables. Suitable climate space for all species decreases under the climate change scenarios investigated in the present study. The models also indicate that the assemblage of Penthaleus spp. is likely to change across Australia, particularly in Western Australia, South Australia and Victoria.
• 4 These results show the distributions of the three Penthaleus spp. are correlated with different climatic variables, and that regional control of mite pests is likely to change in the future. A further understanding of ecological and physiological processes that may influence the distribution and pest status of mites is required.

     

Livestock exclusion alters plant species composition in fen meadows

Questions

Our study evaluated how species composition and plant traits that indicate functioning condition in fens responded to grazing cessation over time in an arid ecosystem of the western US. The specific questions addressed were: (i) how does livestock exclusion influence species composition in fens; (ii) is grazing cessation associated with shifts in species functional traits that indicate fen condition; and (iii) what is the pattern of response to livestock exclusion over time?

Location

Plumas National Forest, California, US.

Methods

We studied paired fenced and unfenced study sites in two fens to examine the effects of livestock exclusion. Parallel transects were established at each site, and plant species and ground cover were repeatedly surveyed, once prior to and multiple times following treatment, using 0.01 m² frequency frames. We used NMDS to analyse species composition, RLQ and fourth‐corner analysis to evaluate species functional traits and environmental variables, and linear mixed effects models to examine differences in responses between fenced and unfenced study sites over time.

Results

After fencing, we observed unexpected shifts in species composition and plant functional traits. Grazed sites were associated with peat‐forming obligate wetland, moss and sedge species, while fenced sites were characterized by non‐peat‐forming facultative upland, and upland forb, grass and early seral species. Species composition also varied between sites and sample years.

Conclusions

We found that livestock exclusion strongly affects plant species composition in fens, including promoting species with functional traits that indicate a loss of functioning condition, such as ruderal and upland species. Possible explanations for these observed shifts include: (1) biomass accumulation in the absence of herbivory, (2) competitive exclusion in fenced sites, (3) succession, (4) the abiotic conditions of our study sites, particularly hydrology and nutrient status, and (5) interactions among these factors. We conclude that degradation of fen wetlands caused by livestock grazing in the arid western US may not be reversed by excluding livestock alone.     

Species distributions models may predict accurately future distributions but poorly how distributions change: A critical perspective on model validation

Aim

Species distribution models (SDMs) are widely used to make predictions on how species distributions may change as a response to climatic change. To assess the reliability of those predictions, they need to be critically validated with respect to what they are used for. While ecologists are typically interested in how and where distributions will change, we argue that SDMs have seldom been evaluated in terms of their capacity to predict such change. Instead, typical retrospective validation methods estimate model's ability to predict to only one static time in future. Here, we apply two validation methods, one that predicts and evaluates a static pattern, while the other measures change and compare their estimates of predictive performance.

Location

Fennoscandia.

Methods

We applied a joint SDM to model the distributions of 120 bird species in four model validation settings. We trained models with a dataset from 1975 to 1999 and predicted species' future occurrence and abundance in two ways: for one static time period (2013–2016, ‘static validation’) and for a change between two time periods (difference between 1996–1999 and 2013–2016, ‘change validation’). We then measured predictive performance using correlation between predicted and observed values. We also related predictive performance to species traits.

Results

Even though static validation method evaluated predictive performance as good, change method indicated very poor performance. Predictive performance was not strongly related to any trait.

Main Conclusions

Static validation method might overestimate predictive performance by not revealing the model's inability to predict change events. If species' distributions remain mostly stable, then even an unfit model can predict the near future well due to temporal autocorrelation. We urge caution when working with forecasts of changes in spatial patterns of species occupancy or abundance, even for SDMs that are based on time series datasets unless they are critically validated for forecasting such change.     

Seedling traits, plasticity and local differentiation as strategies of invasive species of Impatiens in central Europe

Background and Aims

Invasiveness of some alien plants is associated with their traits, plastic responses to environmental conditions and interpopulation differentiation. To obtain insights into the role of these processes in contributing to variation in performance, we compared congeneric species of Impatiens (Balsaminaceae) with different origin and invasion status that occur in central Europe.

Methods

Native I. noli-tangere and three alien species (highly invasive I. glandulifera, less invasive I. parviflora and potentially invasive I. capensis) were studied and their responses to simulated canopy shading and different nutrient and moisture levels were determined in terms of survival and seedling traits.

Key Results and Conclusions

Impatiens glandulifera produced high biomass in all the treatments and the control, exhibiting the ‘Jack-and-master’ strategy that makes it a strong competitor from germination onwards. The results suggest that plasticity and differentiation occurred in all the species tested and that along the continuum from plasticity to differentiation, the species at the plasticity end is the better invader. The most invasive species I. glandulifera appears to be highly plastic, whereas the other two less invasive species, I. parviflora and I. capensis, exhibited lower plasticity but rather strong population differentiation. The invasive Impatiens species were taller and exhibited higher plasticity and differentiation than native I. noli-tangere. This suggests that even within one genus, the relative importance of the phenomena contributing to invasiveness appears to be species''specific.     

Invasive plants in Minnesota are “joining the locals”: A trait‐based analysis

Questions

Predicting which newly arrived species will establish and become invasive is a problem that has long vexed researchers. In a study of cold temperate oak forest stands, we examined two contrasting hypotheses regarding plant functional traits to explain the success of certain non‐native species. Under the “join the locals” hypothesis, successful invaders are expected to share traits with resident species because they employ successful growth strategies under light‐limited understorey conditions. Instead, under the “try harder” hypothesis, successful invaders are expected to have traits different from native species in order to take advantage of unused niche space.

Location

Minnesota, USA.

Methods

We examined these two theories using 109 native and 11 non‐native plants in 68 oak forest stands. We focused on traits related to plant establishment and growth, including specific leaf area (SLA), leaf carbon‐to‐nitrogen ratio (C:N), wood density, plant maximum height, mycorrhizal type, seed mass and growth form. We compared traits of native and non‐native species using ordinations in multidimensional trait space and compared community‐weighted mean (CWM) trait values across sites.

Results

We found few differences between trait spaces occupied by native and non‐native species. Non‐native species occupied smaller areas of trait space than natives, yet were within that of the native species, indicating similar growth strategies. We observed a higher proportion of non‐native species in sites with higher native woody species CWM SLA and lower CWM C:N. Higher woody CWM SLA was observed in sites with higher soil pH, while lower CWM C:N was found in sites with higher light levels.

Conclusions

Non‐native plants in this system have functional traits similar to natives and are therefore “joining the locals.” However, non‐native plants may possess traits toward the acquisitive end of the native plant trait range, as evidenced by higher non‐native plant abundance in high‐resource environments.