Adaptation of perennial flowering phenology across the European range of Arabis alpina.

Flowering phenology is important in the adaptation of many plants to their local environment, but its adaptive value has not been extensively studied in herbaceous perennials. We used Arabis alpina as a model system to determine the importance of flowering phenology to fitness of a herbaceous perennial with a wide geographical range. Individual plants representative of local genetic diversity (accessions) were collected across Europe, including in Spain, the Alps and Scandinavia. The flowering behaviour of these accessions was documented in controlled conditions, in common-garden experiments at native sites and in situ in natural populations. Accessions from the Alps and Scandinavia varied in whether they required exposure to cold (vernalization) to induce flowering, and in the timing and duration of flowering. By contrast, all Spanish accessions obligately required vernalization and had a short duration of flowering. Using experimental gardens at native sites, we show that an obligate requirement for vernalization increases survival in Spain. Based on our analyses of genetic diversity and flowering behaviour across Europe, we propose that in the model herbaceous perennial A. alpina, an obligate requirement for vernalization, which is correlated with short duration of flowering, is favoured by selection in Spain where the plants experience a long growing season.

Spatio-temporal variation in the wintering associations of an alpine bird.

Many animals make behavioural changes to cope with winter conditions, being gregariousness a common strategy. Several factors have been invoked to explain why gregariousness may evolve during winter, with individuals coming together and separating as they trade off the different costs and benefits of living in groups. These trade-offs may, however, change over space and time as a response to varying environmental conditions. Despite its importance, little is known about the factors triggering gregarious behaviour during winter and its change in response to variation in weather conditions is poorly documented. Here, we aimed at quantifying large-scale patterns in wintering associations over 23 years of the white-winged snowfinch Montifringilla nivalis nivalis. We found that individuals gather in larger groups at sites with harsh wintering conditions. Individuals at colder sites reunite later and separate earlier in the season than at warmer sites. However, the magnitude and phenology of wintering associations are ruled by changes in weather conditions. When the temperature increased or the levels of precipitation decreased, group size substantially decreased, and individuals stayed united in groups for a shorter time. These results shed light on factors driving gregariousness and points to shifting winter climate as an important factor influencing this behaviour.

Ecological and evolutionary drivers of the elevational gradient of diversity.

Ecological, evolutionary, spatial and neutral theories make distinct predictions and provide distinct explanations for the mechanisms that control the relationship between diversity and the environment. Here, we test predictions of the elevational diversity gradient focusing on Iberian bumblebees, grasshoppers and birds. Processes mediated by local abundance and regional diversity concur in explaining local diversity patterns along elevation. Effects expressed through variation in abundance were similar among taxa and point to the overriding role of a physical factor, temperature. This determines how energy is distributed among individuals and ultimately how the resulting pattern of abundance affects species incidence. Effects expressed through variation in regional species pools depended instead on taxon-specific evolutionary history, and lead to diverging responses under similar environmental pressures. Local filters and regional variation also explain functional diversity gradients, in line with results from species richness that indicate an (local) ecological and (regional) historical unfolding of diversity-elevation relationships.

Abiotic, biotic, and evolutionary control of the distribution of C and N isotopes in food webs.

Ecosystem functioning depends on nutrient cycles and their responses to abiotic and biotic determinants, with the influence of evolutionary legacies being generally overlooked in ecosystem ecology. Along a broad elevation gradient characterized by shifting climatic and grazing environments, we addressed clines of plant N and C∶N content and of δ(13)C and δ(15)N in producers (herbs) and in primary (grasshoppers) and secondary (birds) consumers, both within and between species in phylogenetically controlled scenarios. We found parallel and significant intra- and interspecific trends of isotopic variation with elevation in the three groups. In primary producers, nutrient and isotope distributions had a detectable phylogenetic signal that constrained their variation along the environmental gradient. The influence of the environment could not be ascribed to any single factor, and both grazing and climate had an effect on leaf stoichiometry and, thus, on the resources available to consumers. Trends in consumers matched those in plants but often became nonsignificant after controlling for isotopic values of their direct resources, revealing direct bottom-up control and little phylogenetic dependence. By integrating ecosystem and mechanistic perspectives, we found that nutrient dynamics in food webs are governed at the base by the complex interaction between local determinants and evolutionary factors.

The evolutionary convergence of avian lifestyles and their constrained coevolution with species' ecological niche.

The fit between life histories and ecological niche is a paradigm of phenotypic evolution, also widely used to explain patterns of species co-occurrence. By analysing the lifestyles of a sympatric avian assemblage, we show that species' solutions to environmental problems are not unbound. We identify a life-history continuum structured on the cost of reproduction along a temperature gradient, as well as habitat-driven parental behaviour. However, environmental fit and trait convergence are limited by niche filling and by within-species variability of niche traits, which is greater than variability of life histories. Phylogeny, allometry and trade-offs are other important constraints: lifetime reproductive investment is tightly bound to body size, and the optimal allocation to reproduction for a given size is not established by niche characteristics but by trade-offs with survival. Life histories thus keep pace with habitat and climate, but under the limitations imposed by metabolism, trade-offs among traits and species' realized niche.

Large-scale adaptive differentiation in the alpine perennial herb Arabis alpina.

Information about the incidence and magnitude of local adaptation can help to predict the response of natural populations to a changing environment, and should be of particular interest in arctic and alpine environments where the effects of climate change are expected to be severe. To quantify adaptive differentiation in the arctic-alpine perennial herb Arabis alpina, we conducted reciprocal transplant experiments for 3 yr between Spanish and Scandinavian populations. At the sites of one Spanish and one Scandinavian population, we planted seedlings representing two Spanish and four Scandinavian populations, and recorded survival, flowering propensity and fecundity. The experiment was replicated in two subsequent years. The results demonstrate strong adaptive differentiation between A. alpina populations from the two regions. At the field site in Spain, survival and fruit production of Spanish populations were higher than those of Scandinavian populations, while the opposite was true at the site in Scandinavia, and these differences were consistent across years. By comparison, fitness varied little among populations from the same region. The results suggest that the magnitude and geographical scale of local adaptation need to be considered in predictions of the effects of global change on the dynamics of arctic and alpine plant populations.

Mineral nutrient stoichiometric variability in Hedera helix (Araliaceae) seeds.

BACKGROUND AND AIMS: The analysis of variability in mineral allocation to seeds has rarely been considered in relation to allometric patterns and deviations from the allometric trajectory. Here, I examine the scaling of carbon (C), nitrogen (N), phosphorus (P) and sulfur (S) with seed mass in field-collected seeds of Hedera helix, taking into account that brood size might influence the allocation patterns. METHODS: C, N and S contents of 56 individual seeds of different sizes were analysed by combustion using a standard automated CNHS procedure. P content was determined for 200 individual seeds using spectrophotometry after acid digestion of ashed samples. This sample included seeds from different brood sizes. KEY RESULTS: C and N content both varied isometrically with seed mass and this variable explained most of the variation in their content in seeds. P and S, however, varied allometrically with seed mass. Additionally, seed mass only explained 37·3 % and 37·6 % of the total variance in P and S content, respectively. Seeds with higher mass contained proportionately more P and, furthermore, the seeds from small broods contained proportionally more P than those from large broods. CONCLUSIONS: Although seed mass in this species can be used as a surrogate of investment in C and N, it does not account for variability in allocation of nutrients such as P and S. The fact that larger seeds increased their P concentration when found in smaller broods might be a consequence of intense competition for this nutrient among developing seeds. Then, brood size may influence the mineral nutrient concentration of seeds.

Mimicry as a novel pathway linking biodiversity functions and individual behavioural performances.

The feedback of biodiversity on individual trait variation is a poorly explored mechanistic pathway in ecological research. We analysed the relationship between biodiversity and individual performance by focusing on vocal mimicry, a widespread interaction that may serve in intra- and interspecific communication. We studied the songs of two lark species (genus Galerida) that increase the complexity of their song displays by mimicking other birds, and analysed the influence of bird species richness on individual song performance. The diversity of mimicked species and the prevalence of mimicry increased in areas characterized by great α and γ diversity (i.e. where larks experience more diverse encounters with community members, many of them being highly vocal owing to breeding). Conversely, the variability in species-specific song components peaked where larks were abundant, probably matching the complexity of conspecific social milieu. Some trade-offs existed between homo- and heterospecific complexity, suggesting that larks could change from population- to community-driven song variation by tracking the composition of the auditory environment. Mimicry, which serves communication with conspecifics or predators, may mediate interactions, ultimately cascading to aspects of ecological diversity other than those promoting its complexity.

Selection for functional performance in the evolution of cuticle hardening mechanisms in insects.

Calcified tissues have repeatedly evolved in many animal lineages and show a tremendous diversity of forms and functions. The cuticle of many insects is enriched with elements other than Calcium, a strategy of hardening that is taxonomically widespread but apparently poorly variable among clades. Here, we investigate the evolutionary potential of the enrichment with metals in insect cuticle at different biological levels. We combined experimental evidence of Zinc content variation in the mandibles of a target species (Chorthippus cazurroi [Bolívar]) with phylogenetic comparative analyses among grasshopper species. We found that mandibular Zinc content was repeatable among related individuals and was associated with an indicator of fitness, so there was potential for adaptive variation. Among species, Zinc enrichment evolved as a consequence of environmental and dietary influences on the physical function of the jaw (cutting and chewing), suggesting a role of natural selection in environmental fit. However, there were also important within and transgenerational environmental sources of similarity among individuals. These environmental influences, along with the tight relationship with biomechanics, may limit the potential for diversification of this hardening mechanism. This work provides novel insights into the diversification of biological structures and the link between evolutionary capacity and intra- and interspecific variation.

Evolutionary conservation of within-family biodiversity patterns.

The tendency for species to retain their ancestral biological properties has been widely demonstrated, but the effect of phylogenetic constraints when progressing from species to ensemble-level properties requires further assessment. Here we test whether community-level patterns (environmental shifts in local species richness and turnover) are phylogenetically conserved, assessing whether their similarity across different families of lichens, insects, and birds is dictated by the relatedness of these families. We show a significant phylogenetic signal in the shape of the species richness-elevation curve and the decay of community similarity with elevation: closely related families share community patterns within the three major taxa. Phylogenetic influences are partly explained by similarities among families in conserved traits defining body plan and interactions, implying a scaling of phylogenetic effects from the organismal to the community level. Consequently, the phylogenetic signal in community-level patterns informs about how the historical legacy of a taxon and shared responses among related taxa to similar environments contribute to community assembly and diversity patterns.

Gradual Distance Dispersal Shapes the Genetic Structure in an Alpine Grasshopper.

The location of the high mountains of southern Europe has been crucial in the phylogeography of most European species, but how extrinsic (topography of sky islands) and intrinsic features (dispersal dynamics) have interacted to shape the genetic structure in alpine restricted species is still poorly known. Here we investigated the mechanisms explaining the colonisation of Cantabrian sky islands in an endemic flightless grasshopper. We scrutinised the maternal genetic variability and haplotype structure, and we evaluated the fitting of two migration models to understand the extant genetic structure in these populations: Long-distance dispersal (LDD) and gradual distance dispersal (GDD). We found that GDD fits the real data better than the LDD model, with an onset of the expansion matching postglacial expansions after the retreat of the ice sheets. Our findings suggest a scenario with small carrying capacity, migration rates, and population growth rates, being compatible with a slow dispersal process. The gradual expansion process along the Cantabrian sky islands found here seems to be conditioned by the suitability of habitats and the presence of alpine corridors. Our findings shed light on our understanding about how organisms which have adapted to live in alpine habitats with limited dispersal abilities have faced new and suitable environmental conditions.

The costs of reproduction in plants.

This review reports on the processes associated with costs of reproduction, including some theoretical considerations, definitions and methodological aspects, followed by a list of the situations where costs are difficult to find. Despite some exceptions, case studies, examined by trade-offs between reproduction and other life-history traits, generally support the predictions of the cost of reproduction hypothesis. The cost of reproduction as an evolutionary determinant of sexual dimorphism in life history traits in dioecious species was specifically tested, considering that the higher cost of reproduction in females has driven the life history traits related to sexual dimorphism. Females of woody dioecious species were consistently smaller than males supporting the costs of reproduction hypothesis. By contrast, females of herbaceous perennials were generally the larger sex, which did not fit the expectations of the hypothesis. Finally, the mechanisms that enable the compensation of the reproductive costs are detailed, including the plastic responses of photosynthesis and growth, the effects of the timing of investment, plant architecture and plant physiological integration. Contents Summary 321 I. Introduction 321 II. Theory on costs of reproduction 322 III. Methodological aspects 324 IV. Empirical evidence 328 V. Plant size and costs of reproduction 330 VI. Costs of reproduction in sexually dimorphic plants 331 VII. Compensation of the costs 333 VIII. Concluding comments and future perspectives 336 Acknowledgements 337 References 337.

Geographic distribution and community structure of bumblebees in the northern Iberian peninsula.

Relationships between species distribution and abundance, the influence of proboscis length on species-packing, and species associations within the local assemblages were studied in local communities of bumblebees in northern Spain along an altitudinal gradient. Local species abundance and altitudinal range occupied accounted for much of the variation in species distribution. Altitudinal range occupied by species was related to species distribution, but the most important variable accounting for species distribution was the local percentage abundance. Despite this, there was no evidence for age abundance. Despite this, there was no evidence for bimodality in the distributions of species incidence. A general trends for mean proboscis length in each locality to be greater in lowland localities exists, but this variable was not related to species distribution or abundance. Proboscis length spacings were studied among species in local assemblages and in most of the cases observed spacing did not differ from random expectations. The same patterns were demonstrated calculating spacings for 'core' species in each local assemblage. Furthermore, species showed little tendency towards associations, so it may be concluded that bumblebee assemblages were irregularly structured and no clear patterns emerged from the present study.

Effects of sexual dimorphism and landscape composition on the trophic behavior of Greater Prairie-Chicken.

Partitioning of ecological niche is expected in lekking species that show marked sexual size dimorphism as a consequence of sex-specific ecological constraints. However, niche partitioning is uncertain in species with moderate sexual dimorphism. In addition, the ecological niche of a species may also be affected by landscape composition; particularly, agricultural fragmentation may greatly influence the trophic behavior of herbivores. We studied trophic niche variation in Greater Prairie-Chickens (Tympanuchus cupido), a grouse species that shows moderate sex-dimorphism. Greater Prairie-Chickens are native to tallgrass prairies of North America, although populations persist in less natural mosaics of cropland and native habitats. We used stable isotope analysis of carbon and nitrogen in blood, claws and feathers to assess seasonal differences in trophic niche breadth and individual specialization between male and female Greater Prairie-Chickens, and between birds living in continuous and fragmented landscapes. We found that females showed broader niches and higher individual specialization than males, especially in winter and autumn. However, differences between females and males were smaller in spring when birds converge at leks, suggesting that females and males may exhibit similar feeding behaviors during the lekking period. In addition, we found that birds living in native prairies showed greater annual trophic variability than conspecifics in agricultural mosaic landscapes. Native habitats may provide greater dietary diversity, resulting in greater diversity of feeding strategies.

Multilevel selection and neighbourhood effects from individual to metapopulation in a wild passerine.

Multilevel selection has rarely been studied in the ecological context of animal populations, in which neighbourhood effects range from competition among territorial neighbours to source-sink effects among local populations. By studying a Dupont's lark Chersophilus duponti metapopulation, we analyze neighbourhood effects mediated by song repertoires on fitness components at the individual level (life-span) and population level (growth rate). As a sexual/aggressive signal with strong effects on fitness, birdsong creates an opportunity for group selection via neighbour interactions, but may also have population-wide effects by conveying information on habitat suitability to dispersing individuals. Within populations, we found a disruptive pattern of selection at the individual level and an opposite, stabilizing pattern at the group level. Males singing the most complex songs had the longest life-span, but individuals with the poorest repertoires lived longer than 'average' males, a finding that likely reflects two male strategies with respect to fitness and sexual trait expression. Individuals from groups with intermediate repertoires had the longest life-span, likely benefitting from conspecific signalling to attract females up to the detrimental spread of competitive interactions in groups with superior vocal skills. Within the metapopulation selection was directional but again followed opposite patterns at the two levels: Populations had the highest growth rate when inhabiting local patches with complex repertoires surrounded by patches with simple repertoires. Here the song may impact metapopulation dynamics by guiding prospecting individuals towards populations advertising habitat quality. Two fitness components linked to viability were therefore influenced by the properties of the group, and birdsong was the target of selection, contributing to linking social/sexual processes at the local scale with regional population dynamics.

Rodent seed predation promotes differential recruitment among bird-dispersed trees in temperate secondary forests.

We investigated the role of seed predation by rodents in the recruitment of the fleshy-fruited trees Taxus baccata, Ilex aquifolium and Crataegus monogyna in temperate secondary forests in NW Spain. We measured the densities of dispersed seeds, early emerged seedlings, established recruits and adults, at four sites over a period of 2 years. Seed predation among species was compared by seed removal experiments and analysis of rodent larder-hoards. The three species differed markedly in local regeneration patterns. The rank order in the seed rain following decreasing seed density was Ilex, Taxus and Crataegus. However, Crataegus established 3.3 times more seedlings than Taxus. For all species, there was a positive linear relationship between the density of emerged seedlings and seed density, suggesting that recruitment was seed- rather than microsite-limited. A consistent pattern of seed selection among species was exerted by rodents, which preferred Taxus and, secondarily, Ilex seeds to Crataegus seeds. Predation ranking was the inverse of that of seed protection against predators, measured as the mass of woody coat per mass unit of the edible fraction. Recruitment potential, evaluated as the ratio of seedlings to seeds, was negatively related to seed predation, with the rank order Crataegus > Ilex > Taxus. The selective early recruitment limitation exerted by predation may have a demographic effect in the long term, as judged by the positive relationship between early seedling emergence and the density of established recruits. By modulating the pre-emptive competition for seed safe sites, rodents may preclude the progressive exclusion of species that produce low numbers of seeds (i.e. Crataegus) by those dominant in seed number (i.e. Ilex, Taxus), or at least foster the evenness for site occupation among seedlings of different species.