Application of watershed analyses and ecosystem modeling to investigate land–water nutrient coupling processes in the Guadalupe Estuary, Texas

Estuarine nutrient enrichment is thought to be controlled by land use patterns in coastal watersheds. Hence, the objective of this work was to conduct a watershed analysis in two adjacent river basins with different land use characteristics to determine their influence on estuarine ecosystem response in the Guadalupe Estuary, Texas, U.S.A. All data sources for this study were available electronically on the Internet; the data were mined, managed, analyzed and transformed to simulate the estuarine ecosystem response to watershed-derived nutrient loads. Between 1992 and 2001, developed land use/land cover increased the most while forest cover decreased the most in both basins. Two hydrologic units nearest the coast were responsible for the greatest change in land cover. Nutrient concentrations and loads were significantly higher in the San Antonio River Basin than in the Guadalupe River Basin. Both river basins exhibited the highest flows ever recorded in 1992, however the magnitude of difference in loads between the two coastal hydrologic units for a wet and dry year was much greater in the Guadalupe River Basin (GRB) than in the San Antonio River Basin (SARB); this difference supports the concept that the GRB is a nonpoint source dominated system and SARB is a point source dominated system. There was a strong correlation between developed land use and nutrient concentrations in river water; the GRB had less developed land use and lower nutrient concentrations while the SARB had more developed land use and higher nutrient concentrations. Estuarine ecosystem response differed in the timing, duration and magnitude of DIN, phytoplankton and zooplankton when nitrogen loads from the Lower Guadalupe River were used as opposed to the Lower San Antonio. The two basins studied differ in their fundamental characteristics, i.e. precipitation, flow, human population density, etc., resulting in different drivers of nitrogen loading, point sources in the San Antonio River Basin and nonpoint sources in the Guadalupe River Basin, therefore, differing estuarine ecosystem responses.     

Resolving species boundaries in the critically imperiled freshwater mussel species,Fusconaia mitchelli (Bivalvia: Unionidae)

Species are a fundamental unit of biology, and defining accurate species boundaries is integral to effective conservation and management of imperiled taxa. Freshwater mussels (Bivalvia: Unionidae) are among the most imperiled groups of organisms in North America, yet species boundaries remain uncertain for many taxa. The False Spike, Fusconaia mitchelli (Simpson in Dall, 1895), is a freshwater mussel considered to be endemic to central Texas (Brazos, Colorado, and Guadalupe drainages). Recent research revealed significant intraspecific genetic variation between geographically separated populations of F. mitchelli, which could be indicative of speciation; however, small sample sizes for several of the populations precluded formal taxonomic revision. Here, we increase taxon sampling and use multilocus DNA sequence data and traditional morphometrics to re‐evaluate species boundaries in F. mitchelli. We sequenced three loci: the protein‐coding mitochondrial DNA genes cytochrome c oxidase subunit 1 and NADH dehydrogenase 1, and the nuclear internal transcribed spacer 1. Phylogenetic analyses depicted deep genetic divergence between F. mitchelli in the Guadalupe and those in the Brazos and Colorado drainages, which was further supported by available biogeographic information. Morphometric analyses and coalescent‐based species delimitation models integrating both DNA sequence and morphological data provided strong support for the divergence observed between the two geographically isolated clades of F. mitchelli. Based on these results, we revise taxonomy accordingly by elevating the junior synonym Fusconaia iheringi (Wright, 1898) to represent the Brazos and Colorado populations and restrict the distribution of F. mitchelli to the Guadalupe River drainage. Our findings may impact pending management decisions to protect F. mitchelli under the U.S. Endangered Species Act.     

Effects of contemporary agricultural land cover on Colorado potato beetle genetic differentiation in the Columbia Basin and Central Sands

Landscape structure, which can be manipulated in agricultural landscapes through crop rotation and modification of field edge habitats, can have important effects on connectivity among local populations of insects. Though crop rotation is known to influence the abundance of Colorado potato beetle (CPB; Leptinotarsa decemlineata Say) in potato (Solanum tuberosum L.) fields each year, whether crop rotation and intervening edge habitat also affect genetic variation among populations is unknown. We investigated the role of landscape configuration and composition in shaping patterns of genetic variation in CPB populations in the Columbia Basin of Oregon and Washington, and the Central Sands of Wisconsin, USA. We compared landscape structure and its potential suitability for dispersal, tested for effects of specific land cover types on genetic differentiation among CPB populations, and examined the relationship between crop rotation distances and genetic diversity. We found higher genetic differentiation between populations separated by low potato land cover, and lower genetic diversity in populations occupying areas with greater crop rotation distances. Importantly, these relationships were only observed in the Columbia Basin, and no other land cover types influenced CPB genetic variation. The lack of signal in Wisconsin may arise as a consequence of greater effective population size and less pronounced genetic drift. Our results suggest that the degree to which host plant land cover connectivity affects CPB genetic variation depends on population size and that power to detect landscape effects on genetic differentiation might be reduced in agricultural insect pest systems.     

Spatially structured intraspecific trait variation can foster biodiversity in disturbed,heterogeneous environments

Trait variation within populations is an important area of research for empirical and theoretical ecologists. While differences between individuals are doubtlessly ubiquitous, their role for species coexistence is much less clear and highly debated. Both unstructured (random) and structured (linked to space, time or inheritance) intraspecific trait variation (ITV) may modify species interactions with nontrivial consequences for emerging community compositions. In many ecosystems, these compositions are further driven by prevalent disturbance regimes. I therefore explored the effects of unstructured as well as spatially structured ITV under disturbances in a generic ecological model of competing sessile species. Using spatially explicit, individual‐based simulations, I studied how intraspecific variation in life history traits together with interspecific tradeoffs and disturbance regimes shape long‐term community composition. I found that 1) unstructured ITV does not affect species coexistence in the given context, 2) spatially structured ITV may considerably increase coexistence, but 3) spatially clumped disturbances reduce this effect of spatially structured ITV, especially if interspecific tradeoffs involve dispersal distance. The findings suggest that spatially structured ITV with individual trait responses to local habitat conditions differing among species may create or expand humps in disturbance–diversity relationships. Hence, if present, these forms of spatially structured ITV should be included in ecological models and will be important for reliably assessing community responses to environmental heterogeneity and change.     

Taxonomic and functional homogenization of an endemic desert fish fauna

Aim The highly endemic fishes of the arid Southwest USA have been heavily impacted by human activities resulting in one of the most threatened fish faunas in the world. The aim of this study was to examine the patterns and drivers of taxonomic and functional beta diversity of freshwater fish in the Lower Colorado River Basin across the 20th century. Location Lower Colorado River Basin (LCRB). Methods The taxonomic and functional similarities of watersheds were quantified to identify patterns of biotic homogenization or differentiation over the period 1900–1999. Path analysis was used to identify the relative influence of dam density, urban land use, precipitation regimes and non‐native species richness on observed changes in fish faunal composition. Results The fish fauna of the LCRB has become increasingly homogenized, both taxonomically (1.1% based on β_sim index) and functionally (6.2% based on Bray–Curtis index), over the 20th century. The rate of homogenization varied substantially; range declines of native species initially caused taxonomic differentiation (?7.9% in the 1960s), followed by marginal homogenization (observed in the 1990s) in response to an influx of non‐native species introductions. By contrast, functional homogenization of the basin was evident considerably earlier (in the 1950s) because of the widespread introduction of non‐native species sharing similar suites of biological traits. Path analysis revealed that both taxonomic and functional homogenization were positively related to the direct and indirect (facilitation by dams and urbanization) effects of non‐native species richness. Main conclusions Our study simultaneously examines rates of change in multiple dimensions of the homogenization process. For the endemic fish fauna of the LCRB, we found that the processes of taxonomic and functional homogenization are highly dynamic over time, varying both in terms of the magnitude and rate of change over the 20th century.     

Capsule Treatments to Enhance Seedling Emergence of Gaura neomexicana ssp. coloradensis

Management of riparian vegetation is difficult because these communities are frequently impacted by herbivores, invasive weeds, and altered hydrologic regimes. Multiple and intertwined factors affecting rare species recruitment are particularly difficult to identify. Gaura neomexicana ssp. coloradensis Munz (Gaura) is a short‐lived perennial forb endemic to riparian areas in mixed‐grass prairies of Wyoming, Nebraska, and Colorado, U.S.A. It became a federally listed threatened species in October 2000. Because the species is a recruitment‐limited monocarpic perennial, we studied the effects of six capsule‐collection dates, a 2‐month cool‐moist stratification, 24‐hr leaching, and 24‐hr imbibition on Gaura seedling emergence. Seedling emergence did not vary with collection date. Capsules collected from Gaura plants grown at the Bridger Plant Materials Center in Montana exhibited greater emergence than capsules harvested from endemic populations near Cheyenne, Wyoming, suggesting that maternal plant growing conditions impact dormancy. Because cool‐moist stratification enhanced seedling emergence of Gaura and leaching did not, sufficient moisture during cool temperatures may be more critical than leaching of germination inhibitors as might occur with normal stream flows. Spring flooding may enhance Gaura recruitment by increasing the availability of riparian sites that are inundated during periods of cool temperatures. If so, hydrologic and climatic regimes must be considered in restoring the unique conditions needed for germination of this rare riparian endemic.     

Functional organization of woody plant assemblages along precipitation and human disturbance gradients in a seasonally dry tropical forest

Chronic anthropogenic disturbances (CAD) and rainfall are important drivers of plant community assembly, but little is known about the role played by inter‐ and intraspecific trait variation as communities respond to these pervasive forces. Here, we examined the hypothesis that lower precipitation and higher CAD reduce both intra‐ and interspecific trait variation in Caatinga dry forests. We sampled woody plants across 15 plots along precipitation and CAD gradients and measured resource‐use traits. The effects of precipitation and CAD on RaoQ functional diversity were decomposed into species turnover and intraspecific variability. We used “T‐statistics” to assess the trait sorting from the regional pool to local communities (i.e., external filtering), and within‐community forces leading to low trait overlap (i.e., internal filtering) at individual and species levels. Intraspecific variability explained at least one‐third of the total trait variation and 46% of variation in multitrait diversity across communities. Increasing disturbance reduced multitrait diversity, while precipitation affected some particular traits, such as wood density. Overall, precipitation determined species sorting across communities, while disturbance relaxed internal filters, leading to higher trait overlap within communities due to higher intraspecific variability. Our results suggest that the woody Caatinga flora contains a substantial amount of both inter‐ and intraspecific trait variation. This variation is not randomly distributed within and across communities, but varies according to rainfall conditions and disturbance intensity. These findings reinforce the emerging idea that human disturbances can reorganize plant communities at multiple scales and highlight trait variability as a key biological asset for the resilience of dry forests.     

Scaling up functional traits for ecosystem services with remote sensing: concepts and methods

Ecosystem service‐based management requires an accurate understanding of how human modification influences ecosystem processes and these relationships are most accurate when based on functional traits. Although trait variation is typically sampled at local scales, remote sensing methods can facilitate scaling up trait variation to regional scales needed for ecosystem service management. We review concepts and methods for scaling up plant and animal functional traits from local to regional spatial scales with the goal of assessing impacts of human modification on ecosystem processes and services. We focus our objectives on considerations and approaches for (1) conducting local plot‐level sampling of trait variation and (2) scaling up trait variation to regional spatial scales using remotely sensed data. We show that sampling methods for scaling up traits need to account for the modification of trait variation due to land cover change and species introductions. Sampling intraspecific variation, stratification by land cover type or landscape context, or inference of traits from published sources may be necessary depending on the traits of interest. Passive and active remote sensing are useful for mapping plant phenological, chemical, and structural traits. Combining these methods can significantly improve their capacity for mapping plant trait variation. These methods can also be used to map landscape and vegetation structure in order to infer animal trait variation. Due to high context dependency, relationships between trait variation and remotely sensed data are not directly transferable across regions. We end our review with a brief synthesis of issues to consider and outlook for the development of these approaches. Research that relates typical functional trait metrics, such as the community‐weighted mean, with remote sensing data and that relates variation in traits that cannot be remotely sensed to other proxies is needed. Our review narrows the gap between functional trait and remote sensing methods for ecosystem service management.     

Contemporary sexual selection does not explain variation in male display traits among populations

Sexual selection is widely hypothesized to facilitate the evolution of reproductive isolation through divergence in sexual traits and sexual trait preferences among populations. However, direct evidence of divergent sexual selection causing intraspecific trait divergence remains limited. Using the wolf spider Schizocosa crassipes, we characterized patterns of female mate choice within and among geographic locations and related those patterns to geographic variation in male display traits to test whether divergent sexual selection caused by mate choice explains intraspecific trait variation. We found evidence of phenotypic selection on male behavior arising from female mate choice, but no evidence that selection varied among locations. Only those suites of morphological and behavioral traits that did not influence mate choice varied geographically. These results are inconsistent with ongoing divergent sexual selection underlying the observed intraspecific divergence in male display traits. These findings align with theory on the potentially restrictive conditions under which divergent sexual selection may persist, and suggest that long‐term studies capable of detecting periodic or transient divergent sexual selection will be critical to rigorously assess the relative importance of divergent sexual selection in intraspecific trait divergence.     

The effect of intraspecific variation and heritability on community pattern and robustness

Intraspecific trait variation is widespread in nature, yet its effects on community dynamics are not well understood. Here we explore the consequences of intraspecific trait variation for coexistence in two‐ and multispecies competitive communities. For two species, the likelihood of coexistence is in general reduced by intraspecific variation, except when the species have almost equal trait means but different trait variances, such that one is a generalist and the other a specialist consumer. In multispecies communities, the only strong effect of non‐heritable intraspecific variation is to reduce expected species richness. However, when intraspecific variation is heritable, allowing for the possibility of trait evolution, communities are much more resilient against environmental disturbance and exhibit far more predictable trait patterns. Our results are robust to varying model parameters and relaxing model assumptions.     

Characterizing the contribution of plasticity and genetic differentiation to community‐level trait responses to environmental change

The match between functional trait variation in communities and environmental gradients is maintained by three processes: phenotypic plasticity and genetic differentiation (intraspecific processes), and species turnover (interspecific). Recently, evidence has emerged suggesting that intraspecific variation might have a potentially large role in driving functional community composition and response to environmental change. However, empirical evidence quantifying the respective importance of phenotypic plasticity and genetic differentiation relative to species turnover is still lacking. We performed a reciprocal transplant experiment using a common herbaceous plant species (Oxalis montana) among low‐, mid‐, and high‐elevation sites to first quantify the contributions of plasticity and genetic differentiation in driving intraspecific variation in three traits: height, specific leaf area, and leaf area. We next compared the contributions of these intraspecific drivers of community trait–environment matching to that of species turnover, which had been previously assessed along the same elevational gradient. Plasticity was the dominant driver of intraspecific trait variation across elevation in all traits, with only a small contribution of genetic differentiation among populations. Local adaptation was not detected to a major extent along the gradient. Fitness components were greatest in O. montana plants with trait values closest to the local community‐weighted means, thus supporting the common assumption that community‐weighted mean trait values represent selective optima. Our results suggest that community‐level trait responses to ongoing climate change should be mostly mediated by species turnover, even at the small spatial scale of our study, with an especially small contribution of evolutionary adaptation within species.     

Autochthonous production in shallow littoral zones of five floodplain rivers: effects of flow,turbidity and nutrients

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Male courtship song and female preference variation between phylogeographically distinct populations of Drosophila montana

Understanding the variation within and between populations in important male mating traits and female preferences is crucial to theories concerning the origin of sexual isolation by coevolution or other processes. There have been surprisingly few studies on the extent of variation and covariation within and between populations, especially where the evolutionary relationships between populations are understood. Here we examine variation in female preferences and a sexually selected male song trait, the carrier frequency of the song, within and between populations from different phylogeographic clusters of Drosophila montana. Song is obligatory for successful mating in this species, and both playback and field studies implicate song carrier frequency as the most important parameter in male song. Carrier frequency varied among three recently collected populations from Oulanka (Finland), Vancouver (Canada), and Colorado (central United States), which represent the main phylogeographic groups in D. montana. Males from Colorado had the most distinct song frequency, which did not follow patterns of genetic differentiation. There was considerable variation in preference functions within, and some variation between, populations. Surprisingly, females from three lines from Colorado seem to have preferences disfavoring the extreme male trait found in this population. We discuss sources of selection on male song and female preference.     

Intraspecific phenotypic variability of plant functional traits in contrasting mountain grasslands habitats

Empirical studies that link plants intraspecific variation to environmental conditions are almost lacking, despite their relevance in understanding mechanisms of plant adaptation, in predicting the outcome of environmental change and in conservation. Here, we investigate intraspecific trait variation of four grassland species along with abiotic environmental variation at high spatial resolution (n = 30 samples per species trait and environmental factor per site) in two contrasting grassland habitats in Central Apennines (Italy). We test for phenotypic adaptation between habitats, intraspecific trait-environment relationships within habitats, and the extent of trait and environmental variation. We considered whole plant, clonal, leaf, and seed traits. Differences between habitats were tested using ANOVA and ANCOVA. Trait-environment relationships were assessed using multiple regression models and hierarchical variance partitioning. The extent of variation was calculated using the coefficient of variation. Significant intraspecific differences in trait attributes between the contrasting habitats indicate phenotypic adaptation to in situ environmental conditions. Within habitats, light, soil temperature, and the availability of nitrate, ammonium, magnesium and potassium were the most important factors driving intraspecific trait-environment relationships. Leaf traits and height growth show lower variability than environment being probably more regulated by plants than clonal traits which show much higher variability. We show the adaptive significance of key plant traits leading to intraspecific adaptation of strategies providing insights for conservation of extant grassland communities. We argue that protecting habitats with considerable medium- and small-scale environmental heterogeneity is important to maintain large intraspecific variability within local populations that finally can buffer against uncertainty of future climate and land use scenarios.     

Contrasting effects of plant inter‐ and intraspecific variation on community trait responses to restoration of a sandy grassland ecosystem

Changes in plant community traits along an environmental gradient are caused by interspecific and intraspecific trait variation. However, little is known about the role of interspecific and intraspecific trait variation in plant community responses to the restoration of a sandy grassland ecosystem. We measured five functional traits of 34 species along a restoration gradient of sandy grassland (mobile dune, semi‐fixed dune, fixed dune, and grassland) in Horqin Sand Land, northern China. We examined how community‐level traits varied with habitat changes and soil gradients using both abundance‐weighted and non‐weighted averages of trait values. We quantified the relative contribution of inter‐ and intraspecific trait variation in specific leaf area (SLA), leaf dry matter content (LDMC), leaf carbon content (LCC), leaf nitrogen content (LNC), and plant height to the community response to habitat changes in the restoration of sandy grassland. We found that five weighted community‐average traits varied significantly with habitat changes. Along the soil gradient in the restoration of sandy grassland, plant height, SLA, LDMC, and LCC increased, while LNC decreased. For all traits, there was a greater contribution of interspecific variation to community response in regard to habitat changes relative to that of intraspecific variation. The relative contribution of the interspecific variation effect of an abundance‐weighted trait was greater than that of a non‐weighted trait with regard to all traits except LDMC. A community‐level trait response to habitat changes was due largely to species turnover. Though the intraspecific shift plays a small role in community trait response to habitat changes, it has an effect on plant coexistence and the maintenance of herbaceous plants in sandy grassland habitats. The context dependency of positive and negative covariation between inter‐ and intraspecific variation further suggests that both effects of inter‐ and intraspecific variation on a community trait should be considered when understanding a plant community response to environmental changes in sandy grassland ecosystems.     

Combining phylogeography and landscape genetics to infer the evolutionary history of a short-range Mediterranean relict, <Emphasis Type="Italic">Salamandra salamandra longirostris</Emphasis>

Examining historical and contemporary processes underlying current patterns of genetic variation is key to reconstruct the evolutionary history of species and implement conservation measures promoting their long-term persistence. Combining phylogeographic and landscape genetic approaches can provide valuable insights, especially in regions harboring high levels of biodiversity that are currently threatened by climate and land cover changes, like southern Iberia. We used genetic (mtDNA and microsatellites) and spatial data (climate and land cover) to infer the evolutionary history and contemporary genetic connectivity in a short-range endemic salamander subspecies, Salamandra salamandra longirostris, using a combination of ecological niche modelling, phylogeographic, and landscape genetic analyses. Ecological-based analyses support a role of the Guadalquivir River Basin as a major vicariant agent in this taxon. The lower genetic diversity and greater differentiation of peripheral populations, together with analyses of climatically stable areas throughout time, suggest the persistence of a population in the central part of the current range since the Last Inter Glacial [LIG; ~?120,000–140,000 years BP], and a micro refugium in the eastern end of the range. Habitat heterogeneity plays a major role in shaping patterns of genetic differentiation in S. s. longirostris, with forests representing key areas for its long-term persistence under scenarios of environmental change. Our study stresses the importance of maintaining population genetic connectivity in low-dispersal organisms under rapidly changing environments, and will inform management plans for the long-term survival of this evolutionarily distinct Mediterranean endemic.     

Light and warming drive forest understorey community development in different environments

Plant community composition and functional traits respond to chronic drivers such as climate change and nitrogen (N) deposition. In contrast, pulse disturbances from ecosystem management can additionally change resources and conditions. Community responses to combined environmental changes may further depend on land‐use legacies. Disentangling the relative importance of these global change drivers is necessary to improve predictions of future plant communities. We performed a multifactor global change experiment to disentangle drivers of herbaceous plant community trajectories in a temperate deciduous forest. Communities of five species, assembled from a pool of 15 forest herb species with varying ecological strategies, were grown in 384 mesocosms on soils from ancient forest (forested at least since 1850) and postagricultural forest (forested since 1950) collected across Europe. Mesocosms were exposed to two‐level full‐factorial treatments of warming, light addition (representing changing forest management) and N enrichment. We measured plant height, specific leaf area (SLA) and species cover over the course of three growing seasons. Increasing light availability followed by warming reordered the species towards a taller herb community, with limited effects of N enrichment or the forest land‐use history. Two‐way interactions between treatments and incorporating intraspecific trait variation (ITV) did not yield additional inference on community height change. Contrastingly, community SLA differed when considering ITV along with species reordering, which highlights ITV’s importance for understanding leaf morphology responses to nutrient enrichment in dark conditions. Contrary to our expectations, we found limited evidence of land‐use legacies affecting community responses to environmental changes, perhaps because dispersal limitation was removed in the experimental design. These findings can improve predictions of community functional trait responses to global changes by acknowledging ITV, and subtle changes in light availability. Adaptive forest management to impending global change could benefit the restoration and conservation of understorey plant communities by reducing the light availability.     

Specificity of grouping behaviour: comparing colony sizes for the same seabird species in distant populations

Animal collective patterns such as group size frequency distributions often show substantial intraspecific variation, suggesting low species‐specific consistency. Here, we dissect intraspecific vs interspecific components of colony size variation to estimate the repeatability (R) of colony size frequency distribution (CSFD) statistics for seabird species breeding in at least two out of four distant geographic areas of the Northern Hemisphere (21 species; 57 populations; 21 665 colonies; 9 326 479 breeding pairs). Colony sizes were highly variable both within and between species. We estimated the proportion of between‐species variation using the repeatability statistic. Colony size‐related statistics of CSFDs (e.g. geometric mean) showed high repeatabilities (R = 0.73–0.88), and shape‐related measures ranged from null (kurtosis), moderate (fit to a log‐normal distribution, R = 0.62) to highly repeatable (e.g. skewness, R = 0.74–0.87). We thus show that species collective patterns can be at the same time highly variable within species and a robust species‐specific trait that bridge ecological spatio‐temporal heterogeneities.     

Distinct ecosystem types respond differentially to grazing exclosure

Here, we evaluate the ecosystem functioning and the ecosystems services supply of different vegetation types (grasslands, shrublands and woodlands) under contrasting management regimes by comparing a protected area with the surrounding landscape, which has been subjected to human disturbance in the Eastern Hills of Uruguay. We propose, based on functional attributes and vegetation physiognomy, a State and Transition Model for the dynamics of the grassland–woodland mosaic. We used remote sensing techniques to: (i) develop a land‐cover map of the study area based on supervised Landsat imagery classification, and (ii) compare attributes of the ecosystem functioning (productivity and seasonality) and service supply derived from the Normalized Difference Vegetation Index (NDVI) images provided by the moderate resolution imaging spectroradiometer (MODIS) sensor. The land‐cover map showed that grasslands and shrublands were the most extensive land covers in the study area. These vegetation types presented higher productivity, seasonality and ecosystem service supply, outside the protected area than inside it. On the other hand, woodlands showed higher productivity, ecosystem service supply and lower seasonality inside the protected area than outside of it. Two axes represented the grassland–woodland mosaic dynamic: (i) the mean annual and (ii) the intra‐annual coefficient of variation of the NDVI. Our results highlight that conservation of grasslands, shrublands and woodlands require different management strategies based on particular disturbance regimes like moderate grazing and controlled burns. Moderate disturbances may help to preserve ecosystem services provisioning in grasslands and shrublands. On the contrary, woodland conservation requires a more rigorous regime of protection against disturbances.     

Local versus regional intraspecific variability in regeneration traits

Intraspecific trait variability has a fundamental contribution to the overall trait variability. However, little is known concerning the relative role of local (e.g. disturbances and species interaction) and regional (biogeographical) processes in generating this intraspecific trait variability. While biogeographical processes enhance plant trait variability between distant populations, in fire-prone ecosystems, recurrent fires may have a preponderant role in generating variability at a local scale. We hypothesize that plants respond to the local spatio-temporal heterogeneity generated by fire by having a relatively large local variability in regeneration traits in such a way that overrides the variability at a broader biogeographical scale. We test this hypothesis by assessing the intraspecific variability in fire-related regeneration traits of two species (Cistus salviifolius and Lavandula stoechas) growing in fire-prone ecosystems of the Mediterranean Basin. For each species, we selected six populations in two distant regions, three in the east (Anatolian Peninsula) and three in the west (Iberian Peninsula). For each species and population, we analysed the following regeneration traits: seed size, seed dormancy and stimulated germination by fire-related cues (heat and smoke). To evaluate the distribution of the variability in these traits, we decomposed the variability of trait values at each level, between regions (regional) and between population within region (local), using linear mixed-effect models. Despite the biogeographical and climatic differences between regions, for the two species, intraspecific variability in regeneration traits was higher at a local (within regions) than at a regional scale (between regions). Our results suggest that, in Mediterranean ecosystems, fire is an important source of intraspecific variability in regeneration traits. This supports the prominent role of fire as an ecological and evolutionary process, producing trait variability and shaping biodiversity in fire-prone ecosystems.