Consequences of competition on the time budgets,growth and distributions of three species of terrestrial slugs

Summary The behavioural time budgets of two non-aggressive slugs and one aggreessive species were evaluated in monocultures or in 2-way combinations in field cages. The seasonal time budgets ofL. maximus, A. ater andA. columbianus in monoculture were remarkably similar despite their strong differences in physiological resource allocation. Similarity in physical design and resource utilization appeared to be more important determinants of behaviour. The time budgets showed distinct seasonal patterns associated with underlying physiological demands for reserve accumulation, sperm acquisition and oviposition.A. ater andL. maximus displayed a definite dispersal phase associated with femalephase maturation. In combination,A. ater andA. columbianus had no detectable effect on one another’s time budgets.L. maximus disrupted nearly every category of behaviour in these non-aggressive species, but its own time budget was not significantly different in the monoculture or in the two combinations, except for minor effects on resting and sexual behaviour.L. maximus appeared to be adapted to maximize behavioural disturbance of interspecific competitors while minimizing intraspecific effects.     

Consequences of competition on the reproduction and mortality of three species of terrestrial slugs

The interaction of three species of terrestrial slugs was studied in six field cages containing monocultures and 2-way combinations. A. columbianus and A. ater were non-aggressive species and L. maximus was highly aggressive during the summer. All three species were similar in body design and resource utilization. Reproduction (egg size, eggs/batch, number of batches, wet-weight productivity) and mortality were monitored through the 1977 season. L. maximus drastically reduced reproductive success of the non-aggressive slugs and increased their mortality. There were also significant interactions between the non-aggressive species. Compared to other invertebrates, the life history characteristics of A. columbianus are strongly K-selected and probably evolved through intraspecific exploitative competition in predictable, stable forest habitats. A. ater is best classified as a refuging r-selected species adapted to less predictable, unstable field environments. L. maximus appears to be α-selected and its overall design is suited to density-dependent regulation in fields.     

The regulation of activity in populations of the terrestrial slugLimax maximus (Gastropoda; Limacidae)

The activity of the slug Limax maximus was studied in relation to weather. Three hundred-and-fifty-eight hourly observations of activity and weather were made on 21 nights from May until October, 1976. Factors causally important to molluscan activity were included in a step-down correlation-regression analysis of daily and seasonal behavior. The analysis was also performed using weather data from the previous hourly observation. Models using lag-weather did not explain as much variability as did concurrent weather. The regression models explained about 73% to 87% of the observed variation in activity. The most important factors included in the regression models were time of day (circadian rhythm), light intensity, changes in light intensity and surface temperature. Shelter temperature, temperature gradients, length of the night, and time of sunset were also included in some models. Age and hydration were shown to be key factors in other experiments. A model incorporating weather thresholds estimated from field data explained 83.06% of the variability in the activity of L. maximus over the season. The values predicted from the model did not differ significantly from those actually observed in the field (Kolmogorov-Smirnov test, p>0.50).     

Development and the effects of extended parenting in the cold‐breeding burying beetle Nicrophorus sayi

1. Burying beetles (Nicrophorus spp.) provide an excellent model system to test predictions about the relationships between environment, life‐history and behaviour. All species in the genus display similar natural histories, breeding on vertebrate carcasses and providing parental care to developing offspring. However, variations in other aspects of species' ecologies provide a rich framework to examine the evolution of parental behaviours and other traits. 2. One little‐studied species, N. sayi, breeds in substantially colder temperatures than its congeners, creating a potentially harsh environment for offspring. Here, we examined the timing of reproductive and developmental events in this species, and also investigated the effects of removing parents on offspring performance. 3. We find that development is not only extremely slow in this species, but it is also delayed even in comparison to other burying beetles reared at similar temperatures. However, the presence of parents reduces the time that offspring take to leave the carcass. This decrease in development time does not appear to result in a trade‐off with mortality or body size. 4. From these results, we suggest that very slow development may be advantageous when living in a particularly cold environment. Additionally, one role of extended parental care may be to assist offspring in dealing with these harsh conditions, and to mitigate the potentially negative consequences of adopting such a slow life‐history strategy.     

Quantifying the activity levels and behavioural responses of butterfly species to habitat boundaries

1. The ability of species' to undergo climate‐driven range shifts across fragmented landscapes depends on their dispersal ability as well as the structure of the landscape. For species' range shifts to occur, individuals must first leave suitable habitat to seek new habitat; this is likely to depend on the rate of movement of individuals within habitat and the likelihood that a boundary is crossed, once it is encountered. For three species of butterfly with contrasting histories of recent range expansion, we examined the propensity of individuals to move within a habitat and their responses to habitat boundaries. 2. We quantified the extent to which Plebejus argus (Linnaeus) (a declining habitat specialist), Aricia agestis (Schiffermuller) (an expanding generalist) and Polymmatus icarus (Rottemburg) (a geographically ubiquitous generalist) crossed habitat boundaries into unsuitable habitat and moved within suitable habitat. The observed movement was then related to individual and environmental conditions. 3. Species differed in their activity levels in accordance within their recent distribution patterns (P. icarus > A. agestis > P. argus). Our results for P. argus suggest that movement may be motivated by nectar‐seeking, and that males generally move more than females. All three species tended to avoid crossing habitat boundaries; however the proportion of individuals crossing habitat boundaries did not differ significantly among species. 4. We conclude that levels of activity within a habitat, which will affect the frequency with which individuals encounter habitat boundaries, rather than behavioural responses to the boundaries, may be important drivers of distribution change.     

Breeding ground temperature rises,more than habitat change,are associated with spatially variable population trends in two species of migratory bird

Habitat loss and climate change are key drivers of global biodiversity declines but their relative importance has rarely been examined. We attempted to attribute spatially divergent population trends of two Afro-Palaearctic migrant warbler species, Willow Warbler Phylloscopus trochilus and Common Chiffchaff Phylloscopus collybita, to changes in breeding grounds climate or habitat. We used bird counts from over 4000 sites across the UK between 1994 and 2017, monitored as part of the BTO/JNCC/RSPB Breeding Bird Survey. We modelled Willow Warbler and Common Chiffchaff population size and growth in relation to habitat, climate and weather. We then used the abundance model coefficients and observed environmental changes to determine the extent to which spatially varying population trends in England and Scotland were consistent with attribution to climate and habitat changes. Both species' population size and growth correlated with habitat, climate and weather on their breeding grounds. Changes in habitat, in particular woodland expansion, could be linked to small population increases for both species in England and Scotland. Both species' populations correlated more strongly with climate than weather, and both had an optimum breeding season temperature: 11°C for Willow Warbler and around 13.5°C for Common Chiffchaff (with marginally different predictions from population size and growth models). Breeding ground temperature increases, therefore, had the potential to have caused some of the observed Willow Warbler declines in England (where the mean breeding season temperature was 12.7°C) and increases in Scotland (mean breeding season temperature was 10.2°C), and some of the differential rates of increase for Common Chiffchaff. However, much of the variation in species' population abundance and trends were not well predicted by our models and could be due to other factors, such as species interactions, habitat and climate change in their wintering grounds and on migration. This study provides evidence that the effect of climate change on a species may vary spatially and may switch from being beneficial to being detrimental if a temperature threshold is exceeded.     

Lethal and sublethal behavioural responses of saline water beetles to acute heat and osmotic stress

1. As species' physiological breadth determines their potential to deal with environmental changes, and influences individuals' survival and the persistence of populations, information about lethal and sublethal responses could be fundamental for conservation purposes. 2. We used a standard experimental approach to explore mortality and behavioural avoidance responses (i.e. flight and emersion from the water) to a combination of acute heat and osmotic stress on six species of saline water beetles (belonging to Enochrus, Nebrioporus, and Ochthebius genera). 3. Heat stress affected survival and behavioural responses in all of the species, whereas osmotic stress and the interaction between both stressors only showed significant effects for the Ochthebius genus. Behavioural and survival patterns were highly interrelated across the stress gradients. The Enochrus and Nebrioporus studied species showed maximum avoidance activity at 35–40 °C, and a short (< 30 min) exposure to 45 °C was lethal. Ochthebius species were the most heat tolerant and displayed increasing behavioural responses with increasing temperature. In the Nebrioporus and Ochthebius genera, the species occupying lotic, more environmentally stable habitats, showed greater mortality, and avoidance responses were higher or initiated at lower stress thresholds than lentic species. In contrast, both Enochrus species displayed a similar mortality, and the lentic species E. bicolor emerged and flew more than the lotic E. falcarius, in concordance with its higher dispersal capacity. 4. Avoidance responses could provide interesting information about species' physiological amplitudes as a complement to lethal responses. The lotic species here studied showed narrower physiological amplitude (i.e. N. baeticus and O. glaber) or lower dispersal ability (i.e. E. falcarius) than their lentic relatives; both traits could result in a higher vulnerability of lotic species to thermal habitat changes.     

Trait‐mediated effects of predation across life‐history stages in container mosquitoes

1. It was determined if the predatory midge Corethrella appendiculata Grabham imposes a fitness cost in a native mosquito, Ochlerotatus triseriatus Say, and an invasive mosquito, Aedes albopictus Skuse. The hypothesis that decreased activity of immature prey in the presence of predator cues is associated with life history costs through all life cycle stages was tested. 2. In experiment 1, individual larvae of O. triseriatus or A. albopictus were raised in the presence or absence of predation cues at two resource levels. Prey were video recorded to detect behavioural responses and to measure development time, size at emergence, and adult longevity. In experiment 2, prey populations were reared in similar environments and the frequency of predator cue additions was varied. 3. Only O. triseriatus reduced its activity in the presence of predation cues. Predation cues were associated with longer immature development times and shorter adult life spans in O. triseriatus, whereas in A. albopictus, the cues were associated with a larger size of emerging adults. 4. In the present study, it was found that behavioural modifications during the larval stage can affect mosquitoes through multiple stages of their complex life cycle. The species‐specific behavioural differences are probably attributable to the longer evolutionary history O. triseriatus has with predators, relative to the invasive A. albopictus.     

Ecological and evolutionary drivers of range size in Coenagrion damselflies

Geographic range size is a key ecological and evolutionary characteristic of a species, yet the causal basis of variation in range size among species remains largely unresolved. One major reason for this is that several ecological and evolutionary traits may jointly shape species' differences in range size. We here present an integrated study of the contribution of ecological (dispersal capacity, body size and latitudinal position) and macroevolutionary (species' age) traits in shaping variation in species' range size in Coenagrion damselflies. We reconstructed the phylogenetic tree of this genus to account for evolutionary history when assessing the contribution of the ecological traits and to evaluate the role of the macroevolutionary trait (species' age). The genus invaded the Nearctic twice independently from the Palearctic, yet this was not associated with the evolution of larger range sizes or dispersal capacity. Body size and species' age did not explain variation in range size. There is higher flight ability (as measured by wing aspect ratio) at higher latitudes. Species with a larger wing aspect ratio had a larger range size, also after correcting for phylogeny, suggesting a role for dispersal capacity in shaping the species' ranges. More northern species had a larger species' range, consistent with Rapoport's rule, possibly related to niche width. Our results underscore the importance of integrating macroecology and macroevolution when explaining range size variation among species.     

Vanishing islands in the sky? A comparison of correlation- and mechanism-based forecasts of range dynamics for montane salamanders under climate change

Forecasting the effects of climate change on species and populations is a fundamental goal of conservation biology, especially for montane endemics which seemingly are under the greatest threat of extinction given their association with cool, high elevation habitats. Species distribution models (also known as niche models) predict where on the landscape there is suitable habitat for a species of interest. Correlative niche modeling, the most commonly employed approach to predict species' distributions, relies on correlations between species' localities and current environmental data. This type of model could spuriously forecast less future suitable habitat because species' current distributions may not adequately represent their thermal tolerance, and future climate conditions may not be analogous to current conditions. We compared the predicted distributions for three montane species of Plethodon salamanders in the southern Appalachian Mountains of North America using a correlative modeling approach and a mechanistic model. The mechanistic model incorporates species-specific physiology, morphology and behavior to predict an annual energy budget on the landscape. Both modeling approaches performed well at predicting the species' current distributions and predicted that all species could persist in habitats at higher elevation through 2085. The mechanistic model predicted more future suitable habitat than the correlative model. We attribute these differences to the mechanistic approach being able to model shifts in key range-limiting biological processes (changes in surface activity time and energy costs) that the correlative approach cannot. Choice of global circulation model (GCM) contributed significantly to distribution predictions, with a tenfold difference in future suitability based on GCM, indicating that GCM variability should be either directly included in models of species distributions or, indirectly, through the use of multi-model ensemble averages. Our results indicate that correlative models are over-predicting habitat loss for montane species, suggesting a critical need to incorporate mechanisms into forecasts of species' range dynamics.     

European butterfly populations vary in sensitivity to weather across their geographical ranges

Aim

The aim was to assess the sensitivity of butterfly population dynamics to variation in weather conditions across their geographical ranges, relative to sensitivity to density dependence, and determine whether sensitivity is greater towards latitudinal range margins.

Location

Europe.

Time period

1980–2014.

Major taxa studied

Butterflies.

Methods

We use long‐term (35 years) butterfly monitoring data from > 900 sites, ranging from Finland to Spain, grouping sites into 2° latitudinal bands. For 12 univoltine butterfly species with sufficient data from at least four bands, we construct population growth rate models that include density dependence, temperature and precipitation during distinct life‐cycle periods, defined to accommodate regional variation in phenology. We use partial R² values as indicators of butterfly population dynamics' sensitivity to weather and density dependence, and assess how these vary with latitudinal position within a species' distribution.

Results

Population growth rates appear uniformly sensitive to density dependence across species' geographical distributions, and sensitivity to density dependence is typically greater than sensitivity to weather. Sensitivity to weather is greatest towards range edges, with symmetry in northern and southern parts of the range. This pattern is not driven by variation in the magnitude of weather variability across the range, topographic heterogeneity, latitudinal range extent or phylogeny. Significant weather variables in population growth rate models appear evenly distributed across the life cycle and across temperature and precipitation, with substantial intraspecific variation across the geographical ranges in the associations between population dynamics and specific weather variables.

Main conclusions

Range‐edge populations appear more sensitive to changes in weather than those nearer the centre of species' distributions, but density dependence does not exhibit this pattern. Precipitation is as important as temperature in driving butterfly population dynamics. Intraspecific variation in the form and strength of sensitivity to weather suggests that there may be important geographical variation in populations' responses to climate change.     

Differential effect of wave stress on the physiology and behaviour of native versus non-native benthic invertebrates

In fresh waters, non-native invertebrate species preferentially spread via navigation waterways, where they often dominate assemblages. Littoral habitats in navigation waterways are regularly exposed to ship-induced waves. We conducted experiments to test the effects of artificial wave exposure on the relative performance of wide-spread native and non-native species. We compared physiological and behavioural response variables (i.e. growth rate, glycogen content, feeding and swimming activity) of two amphipods (native Gammarus roeselii and non-native Dikerogammarus villosus) and two gastropods (native Bithynia tentaculata and non-native Physella acuta) subject to wave and control (i.e. no wave) treatment flumes across a 6-week period. Growth, and in part glycogen content (as a measure of energy storage), were significantly reduced after exposure to waves in native invertebrates, but not in non-native invertebrates. The reduction in growth may be associated with the disturbance effects of waves, such as the higher swimming activity of G. roeselii and lower food uptake of B. tentaculata. In comparison, the effective hiding behaviour observed for D. villosus and good swimming ability of P. acuta, were identified as important traits facilitating the successful colonisation of the harsh habitat conditions of littoral waterways. Our study demonstrates that artificial wave regimes may contribute significant selective pressure, thus explaining the observed dominance of non-native species in navigational waterways. The success of non-native species under the harsh hydraulic habitat conditions of these socio-economically driven ecosystems may consequently be traced directly to behavioural and/or physiological traits.     

Behavioural thermoregulation and climatic range restriction in the globally threatened Ethiopian Bush‐crow Zavattariornis stresemanni

Climate may influence the distribution and abundance of a species through a number of demographic and ecological processes, but the proximate drivers of such responses are only recently being identified. The Ethiopian Bush‐crow Zavattariornis stresemanni is a starling‐like corvid that is restricted to a small region of southern Ethiopia. It is classified as Endangered in the IUCN Red List of globally threatened species. Previous work suggested that this range restriction is almost perfectly defined by a climate envelope that is cooler than surrounding areas, but the proximate mechanism remains unexplained. The heavily altered habitats which the species inhabits are widespread across Africa, and recent work has shown that the Bush‐crow is behaviourally adaptable and has a catholic diet. We assess whether its enigmatic distribution can be explained by behavioural responses to the higher temperatures that surround its current range. Using environmental niche models and field observations of thermally mediated behaviour, we compare the range restriction and behavioural thermoregulation of the Ethiopian Bush‐crow with those of two sympatric control species that are similar in size and ecology, but have much larger ranges that include hotter environments. White‐crowned Starling Lamprotornis albicapillus and Superb Starling L. superbus occupy similar habitats to the Ethiopian Bush‐crow and all three frequently forage together. We found that the Bush‐crow's range is limited primarily by temperature, with a secondary effect of dry season rainfall, whereas the ranges of the two starling species are better predicted by wet season rainfall alone. Bush‐crows exhibited panting behaviour and moved into the shade of trees at significantly lower ambient temperatures than did the starlings, and their food intake declined more steeply with increasing temperature. These results indicate that the limited geographical range of the Bush‐crow reflects an inability to cope with higher temperatures. This suggests that a species' response to climate change might not be easily predicted by its ecological generalism, and may represent an inherited debt from its evolutionary history.     

Parallel speciation or long‐distance dispersal? Lessons from seaweeds (Fucus) in the Baltic Sea

Parallel evolution has been invoked as a forceful mechanism of ecotype and species formation in many animal taxa. However, parallelism may be difficult to separate from recently monophyletically diverged species that are likely to show complex genetic relationships as a result of considerable shared ancestral variation and secondary hybridization in local areas. Thus, species' degrees of reproductive isolation, barriers to dispersal and, in particular, limited capacities for long‐distance dispersal will affect demographical structures underlying mechanisms of divergent evolution. Here, we used nine microsatellite DNA markers to study intra‐ and interspecific genetic diversity of two recently diverged species of brown macroalgae, Fucus radicans (L. Bergström & L. Kautsky) and F. vesiculosus (Linnaeus), in the Baltic Sea. We further performed biophysical modelling to identify likely connectivity patterns influencing the species' genetic structures. For each species, we found intraspecific contrasting patterns of clonality incidence and population structure. In addition, strong genetic differentiation between the two species within each locality supported the existence of two distinct evolutionary lineages (F_ST = 0.15–0.41). However, overall genetic clustering analyses across both species' populations revealed that all populations from one region (Estonia) were more genetically similar to each other than to their own taxon from the other two regions (Sweden and Finland). Our data support a hypothesis of parallel speciation. Alternatively, Estonia may be the ancestral source of both species, but is presently isolated by oceanographic barriers to dispersal. Thus, a limited gene flow in combination with genetic drift could have shaped the seemingly parallel structure.     

Niche evolution and thermal adaptation in the temperate species Drosophila americana

The study of ecological niche evolution is fundamental for understanding how the environment influences species' geographical distributions and their adaptation to divergent environments. Here, we present a study of the ecological niche, demographic history and thermal performance (locomotor activity, developmental time and fertility/viability) of the temperate species Drosophila americana and its two chromosomal forms. Temperature is the environmental factor that contributes most to the species' and chromosomal forms' ecological niches, although precipitation is also important in the model of the southern populations. The past distribution model of the species predicts a drastic reduction in the suitable area for the distribution of the species during the last glacial maximum (LGM), suggesting a strong bottleneck. However, DNA analyses did not detect a bottleneck signature during the LGM. These contrasting results could indicate that D. americana niche preference evolves with environmental change, and thus, there is no evidence to support niche conservatism in this species. Thermal performance experiments show no difference in the locomotor activity across a temperature range of 15 to 38 °C between flies from the north and the south of its distribution. However, we found significant differences in developmental time and fertility/viability between the two chromosomal forms at the model's optimal temperatures for the two forms. However, results do not indicate that they perform better for the traits studied here in their respective optimal niche temperatures. This suggests that behaviour plays an important role in thermoregulation, supporting the capacity of this species to adapt to different climatic conditions across its latitudinal distribution.     

Cryptic species,gene recombination and hybridization in the genus Spiraeanthemum (Cunoniaceae) from New Caledonia

The Oceanian plant genus Spiraeanthemum (Cunoniaceae) has a centre of diversity in New Caledonia, where it is represented by seven species. Its diversification was investigated using two low‐copy nuclear genes, ncpGS and GapC, and phylogenetic analyses were based on maximum parsimony, maximum likelihood and recombination networks. We detected several cases of gene recombination in both datasets, and these have obscured the history within the genus. For S. ellipticum and S. pubescens, accessions from southern populations on ultramafic soils were genetically distinct from accessions from northern populations on non‐ultramafic soils. Given that no obvious morphological characters distinguish northern and southern populations in either taxon, both may be considered as examples of cryptic species. Incongruence between gene trees and species' delimitation may be explained by the parallel evolution of similar morphology, differential lineage sorting leading to differential fixation of alleles or different introgression patterns in the north and south leading to allele displacement. In New Caledonia, some species with broad ecological preferences may thus be artificial concepts. This suggests that they should be treated more critically in monographs and that the species' richness of the New Caledonian flora may be underestimated. Problems associated with the typification of S. ellipticum and evidence of hybridization events in the history of Spiraeanthemum are also discussed. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 161 , 137–152.     

Competition between Native Hawaiian Plants and the Invasive Grass Megathyrsus maximus: Implications of Functional Diversity for Ecological Restoration

Biodiversity loss is a global crisis, due primarily to habitat destruction and widespread nonnative invasions. Invasive grasses are particularly problematic in many tropical ecosystems, where they possess traits that promote their persistence and can drastically alter native plant communities. We explored the ecophysiological basis for restoring native Hawaiian dryland ecosystems currently dominated by the nonnative invasive grass Megathyrsus maximus (guinea grass) in a garden experiment. Three native species—Myoporum sandwicense (naio; canopy tree), Dodonaea viscosa (aalii; shrub), and Plumbago zeylanica (iliee; groundcover)—were grown with M. maximus at three levels of native functional diversity (one, two, or three species) while holding overall plant density constant. We tested which individual and functional combinations of native species were more productive and best suppressed M. maximus growth and reproduction. Megathyrsus maximus had 39–94% higher maximum photosynthetic rates (A_max) than native species and increasing native functional diversity did not affect M. maximus A_max. Aboveground, belowground, and total biomass of M. maximus varied with functional diversity, although intraspecific competition reduced growth as much as interspecific competition. Reproductive tiller production by M. maximus decreased significantly when planted with any of the native species and with increasing native functional diversity. These results indicate that high native functional diversity in an ecological restoration setting may aid in the control of a dominant invasive grass and the reintroduction of diverse native species. Recommendations for restoring degraded nonnative grasslands in Hawaii and throughout the tropics include selection of native species that are ecophysiologically competitive and have high functional diversity.     

The adaptive significance of behavioural ontogeny in some. centrarchid fishes

Synopsis Studies on the ontogeny of behaviour in fish have seldom considered the adaptive significance of the order of appearance of the behaviours. Results of laboratory studies and field observations on the ontogeny of feeding, predator-avoidance, and agonistic behaviour in largemouth bass, Micropterus salmoides, rock bass, Ambloplites rupestris, and pumpkinseed, Lepomis gibbosus, young indicate that the order of appearance of the various behavioural systems enhances the survival of the young. In the laboratory, all species spend significantly more time feeding during the first weeks of free-swimming than the later weeks. During a corresponding period in the field the young are either occupying an offshore area low in predators (rock bass, pumpkinseed) or are being guarded by a parent (largemouth bass); thus the risk of predation is low. When the young are in a predator-rich environment (inshore) both the predator-avoidance response and agonistic behaviour are well developed. Agonistic behaviour is the last to appear and may serve to disperse the young. Dispersal may relate to the feeding mode of the various species and may also reduce the probability of predation. It is apparent that the sequential onsets of the behavioural systems are in concert with ecological events and selective pressures confronting centarchid young.     

Climate niche shift in invasive species: the case of the brown anole

Anolis sagrei, a Cuba and Bahama native lizard, is a successful invader in Florida and adjacent areas. Herein, we focus on conservatism in its climate niche axes and possible congruencies with its natural history properties. The not mutually exclusive hypotheses of the present study explaining its northern range limit are: (1) climatic conditions within species' native and invasive ranges are identical; (2) the species is pre‐adapted to novel conditions as a result of historical climate variations; and (3) only some niche axes limit the species' invasive distribution and the observed pattern is explained by an interplay between the potential niche within its native range and life‐history. Species distribution models for native and invasive distributions were built on ten bioclimatic variables. Using Schoener's niche overlap index, the degree of niche conservatism among variables was identified. Significances of hypothesis (1) were tested using null‐model approaches. Possible climatic pre‐adaptations were evaluated by comparing its actual tolerance within its invasive range with that of the Last Glacial Maximum (LGM) within its native range (hypothesis 2). Results of (1) and (2) are discussed in relation to natural history, approaching hypothesis 3. We detect varying overlaps in niche axes, indicating that natural history properties are associated with conservative niche axes. Climatic comparisons with LGM of native and current conditions of invasive range suggest that pre‐adaptations are unlikely. Possible shifts in the fundamental niche of the species may have been facilitated by enhanced genetic diversity in northern invasive populations. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 943–954.     

Range expansion through fragmented landscapes under a variable climate

Ecological responses to climate change may depend on complex patterns of variability in weather and local microclimate that overlay global increases in mean temperature. Here, we show that high‐resolution temporal and spatial variability in temperature drives the dynamics of range expansion for an exemplar species, the butterfly Hesperia comma. Using fine‐resolution (5 m) models of vegetation surface microclimate, we estimate the thermal suitability of 906 habitat patches at the species' range margin for 27 years. Population and metapopulation models that incorporate this dynamic microclimate surface improve predictions of observed annual changes to population density and patch occupancy dynamics during the species' range expansion from 1982 to 2009. Our findings reveal how fine‐scale, short‐term environmental variability drives rates and patterns of range expansion through spatially localised, intermittent episodes of expansion and contraction. Incorporating dynamic microclimates can thus improve models of species range shifts at spatial and temporal scales relevant to conservation interventions.