Among-population variation in drought responses is consistent across life stages but not between native and non-native ranges.

Understanding how widespread species adapt to variation in abiotic conditions across their ranges is fundamental to ecology. Insight may come from studying how among-population variation (APV) in the common garden corresponds with the environmental conditions of source populations. However, there are no such studies comparing native vs non-native populations across multiple life stages. We examined APV in the performance and functional traits of 59 Conyza canadensis populations, in response to drought, across large aridity gradients in the native (North America) and non-native (Eurasia) ranges in three experiments. Our treatment (dry vs wet) was applied at the recruitment, juvenile, and adult life stages. We found contrasting patterns of APV in drought responses between the two ranges. In the native range, plant performance was less reduced by drought in populations from xeric than mesic habitats, but such relationship was not apparent for non-native populations. These range-specific patterns were consistent across the life stages. The weak adaptive responses of non-native populations indicate that they can become highly abundant even without complete local adaptation to abiotic environments and suggest that long-established invaders may still be evolving to the abiotic environment. These findings may explain lag times in invasions and raise concern about future expansions.

Land use modulates resistance of grasslands against future climate and inter-annual climate variability in a large field experiment.

Climate and land-use change are key drivers of global change. Full-factorial field experiments in which both drivers are manipulated are essential to understand and predict their potentially interactive effects on the structure and functioning of grassland ecosystems. Here, we present 8 years of data on grassland dynamics from the Global Change Experimental Facility in Central Germany. On large experimental plots, temperature and seasonal patterns of precipitation are manipulated by superimposing regional climate model projections onto background climate variability. Climate manipulation is factorially crossed with agricultural land-use scenarios, including intensively used meadows and extensively used (i.e., low-intensity) meadows and pastures. Inter-annual variation of background climate during our study years was high, including three of the driest years on record for our region. The effects of this temporal variability far exceeded the effects of the experimentally imposed climate change on plant species diversity and productivity, especially in the intensively used grasslands sown with only a few grass cultivars. These changes in productivity and diversity in response to alterations in climate were due to immigrant species replacing the target forage cultivars. This shift from forage cultivars to immigrant species may impose additional economic costs in terms of a decreasing forage value and the need for more frequent management measures. In contrast, the extensively used grasslands showed weaker responses to both experimentally manipulated future climate and inter-annual climate variability, suggesting that these diverse grasslands are more resistant to climate change than intensively used, species-poor grasslands. We therefore conclude that a lower management intensity of agricultural grasslands, associated with a higher plant diversity, can stabilize primary productivity under climate change.

Spatial variability in herbaceous plant phenology is mostly explained by variability in temperature but also by photoperiod and functional traits.

Whereas temporal variability of plant phenology in response to climate change has already been well studied, the spatial variability of phenology is not well understood. Given that phenological shifts may affect biotic interactions, there is a need to investigate how the variability in environmental factors relates to the spatial variability in herbaceous species' phenology by at the same time considering their functional traits to predict their general and species-specific responses to future climate change. In this project, we analysed phenology records of 148 herbaceous species, which were observed for a single year by the PhenObs network in 15 botanical gardens. For each species, we characterised the spatial variability in six different phenological stages across gardens. We used boosted regression trees to link these variabilities in phenology to the variability in environmental parameters (temperature, latitude and local habitat conditions) as well as species traits (seed mass, vegetative height, specific leaf area and temporal niche) hypothesised to be related to phenology variability. We found that spatial variability in the phenology of herbaceous species was mainly driven by the variability in temperature but also photoperiod was an important driving factor for some phenological stages. In addition, we found that early-flowering and less competitive species characterised by small specific leaf area and vegetative height were more variable in their phenology. Our findings contribute to the field of phenology by showing that besides temperature, photoperiod and functional traits are important to be included when spatial variability of herbaceous species is investigated.

Functional traits influence patterns in vegetative and reproductive plant phenology - a multi-botanical garden study.

Phenology has emerged as key indicator of the biological impacts of climate change, yet the role of functional traits constraining variation in herbaceous species' phenology has received little attention. Botanical gardens are ideal places in which to investigate large numbers of species growing under common climate conditions. We ask whether interspecific variation in plant phenology is influenced by differences in functional traits. We recorded onset, end, duration and intensity of initial growth, leafing out, leaf senescence, flowering and fruiting for 212 species across five botanical gardens in Germany. We measured functional traits, including plant height, absolute and specific leaf area, leaf dry matter content, leaf carbon and nitrogen content and seed mass and accounted for species' relatedness. Closely related species showed greater similarities in timing of phenological events than expected by chance, but species' traits had a high degree of explanatory power, pointing to paramount importance of species' life-history strategies. Taller plants showed later timing of initial growth, and flowered, fruited and underwent leaf senescence later. Large-leaved species had shorter flowering and fruiting durations. Taller, large-leaved species differ in their phenology and are more competitive than smaller, small-leaved species. We assume climate warming will change plant communities' competitive hierarchies with consequences for biodiversity.

Tracking population genetic signatures of local extinction with herbarium specimens.

BACKGROUND AND AIMS: Habitat degradation and landscape fragmentation dramatically lower population sizes of rare plant species. Decreasing population sizes may, in turn, negatively affect genetic diversity and reproductive fitness, which can ultimately lead to local extinction of populations. Although such extinction vortex dynamics have been postulated in theory and modelling for decades, empirical evidence from local extinctions of plant populations is scarce. In particular, comparisons between current vs. historical genetic diversity and differentiation are lacking despite their potential to guide conservation management. METHODS: We studied the population genetic signatures of the local extinction of Biscutella laevigata subsp. gracilis populations in Central Germany. We used microsatellites to genotype individuals from 15 current populations, one ex situ population, and 81 herbarium samples from five extant and 22 extinct populations. In the current populations, we recorded population size and fitness proxies, collected seeds for a germination trial and conducted a vegetation survey. The latter served as a surrogate for habitat conditions to study how habitat dissimilarity affects functional connectivity among the current populations. KEY RESULTS: Bayesian clustering revealed similar gene pool distribution in current and historical samples but also indicated that a distinct genetic cluster was significantly associated with extinction probability. Gene flow was affected by both the spatial distance and floristic composition of population sites, highlighting the potential of floristic composition as a powerful predictor of functional connectivity which may promote decision-making for reintroduction measures. For an extinct population, we found a negative relationship between sampling year and heterozygosity. Inbreeding negatively affected germination. CONCLUSIONS: Our study illustrates the usefulness of historical DNA to study extinction vortices in threatened species. Our novel combination of classical population genetics together with data from herbarium specimens, an ex situ population and a germination trial underlines the need for genetic rescue measures to prevent extinction of B. laevigata in Central Germany.

Bracken fern does not diminish arbuscular mycorrhizal fungus inoculum potential in tropical deforested areas.

Tropical montane forests are threatened by uncontrolled fire events because of agricultural expansion. Consequently, deforested areas frequently are dominated by the bracken fern, Pteridium spp., for long periods, and forest regeneration is limited. Despite considerable research on bracken-dominated ecosystems, little is known about the relationship between bracken mycorrhizal fungi and tree seedlings. Arbuscular mycorrhizal fungi (AMF) form symbiotic relationships with terrestrial plants, providing nutrients and protection against pathogens and promoting seedling growth and establishment. Therefore, AMF inoculum have high potential for forest restoration programs. Here, we compare the species diversity of AMF spores, root colonization, and seedling growth of Clusia trochiformis 1 year after the addition of different liquefied root inocula: forest conspecific, forest heterospecific, and from Pteridium rhizomes. Thirteen morphospecies of arbuscular mycorrhizal fungi were identified on the roots of C. trochiformis, and Glomus spp. were the most abundant in all treatments. No differences were observed in spore species richness and diversity among treatments, but spore density was the highest subsequent to the Pteridium inoculum. There was no significant difference in mycorrhizal root colonization and seedling growth of C. trochiformis among inoculated treatments. We found a positive relation between root colonization and total biomass. This study shows that the AMF communities in bracken areas and forests present similar characteristics and that the bracken fern does not limit AMF inoculum potential, favouring seedling growth of Clusia.

Functionally specialised birds respond flexibly to seasonal changes in fruit availability.

Interactions between resource and consumer species result in complex ecological networks. The overall structure of these networks is often stable in space and time, but little is known about the temporal stability of the functional roles of consumer species in these networks. We used a trait-based approach to investigate whether consumers (frugivorous birds) show similar degrees of functional specialisation on resources (plants) in ecological networks across seasons. We additionally tested whether closely related bird species have similar degrees of functional specialisation and whether birds that are functionally specialised on specific resource types within a season are flexible in switching to other resource types in other seasons. We analysed four seasonal replicates of two species-rich plant-frugivore networks from the tropical Andes. To quantify fruit preferences of frugivorous birds, we projected their interactions with plants into a multidimensional plant trait space. To measure functional specialisation of birds, we calculated a species' functional niche breadth (the extent of seasonal plant trait space utilised by a particular bird) and functional originality (the extent to which a bird species' fruit preference functionally differs from those of other species in a seasonal network). We additionally calculated functional flexibility, i.e. the ability of bird species to change their fruit preference across seasons in response to variation in plant resources. Functional specialisation of bird species varied more among species than across seasons, and phylogenetically similar bird species showed similar degrees of functional niche breadth (phylogenetic signal λ = 0·81) and functional originality (λ = 0·89). Additionally, we found that birds with high functional flexibility across seasons had narrow functional niche breadth and high functional originality per season, suggesting that birds that are seasonally specialised on particular resources are most flexible in switching to other fruit resources across seasons. The high flexibility of functionally specialised bird species to switch seasonally to other resources challenges the view that consumer species rely on functionally similar resources throughout the year. This flexibility of consumer species may be an important, but widely neglected mechanism that could potentially stabilise consumer-resource networks in response to human disturbance and environmental change.

Mechanisms driving diversity-productivity relationships differ between exotic and native communities and are affected by gastropod herbivory.

Biodiversity experiments have shown that productivity usually increases with plant species richness. However, most of those studies disregarded the importance of trophic interactions to the diversity-productivity relationship, and focused on the loss of native species while ignoring invasions by exotic species. Yet, as functional complementarity and the impact of plant antagonists are likely to differ between native and exotic communities, the diversity-productivity relationship may change when native communities are invaded by exotic species. We conducted a mesocosm experiment to test how diversity effects, evenness, and productivity differed between exotic and native assemblages of grassland plants, and how these communities were influenced by slug herbivory. In line with other experiments, we found higher productivity in exotic than in native communities. However, different mechanisms (complementarity vs. selection effect) contributed to the positive diversity-productivity relationships in exotic vs. native communities. Against expectations, native communities showed much lower evenness and a greater selection effect, suggesting that competitive dominance among native species may be even stronger than among exotic species. Slug herbivory decreased productivity independently of species origin and species diversity. However, exotic communities showed a threefold higher complementarity effect than native communities in the absence of slugs, which was mainly driven by differences in the responses of native and exotic legumes and nonleguminous herbs. Our results imply that underlying mechanisms for the positive diversity-productivity relationship differ between native and exotic communities in the early stages of community development, and that differential responses of plant functional groups to generalist herbivory can contribute to this pattern.

Pleistocene climatic oscillations rather than recent human disturbance influence genetic diversity in one of the world's highest treeline species.

PREMISE OF THE STUDY: Biological responses to climatic change usually leave imprints on the genetic diversity and structure of plants. Information on the current genetic diversity and structure of dominant tree species has facilitated our general understanding of phylogeographical patterns. METHODS: Using amplified fragment length polymorphism (AFLPs), we compared genetic diversity and structure of 384 adults of P. tarapacana with those of 384 seedlings across 32 forest sites spanning a latitudinal gradient of 600 km occurring between 4100 m and 5000 m a.s.l. in Polylepis tarapacana (Rosaceae), one of the world's highest treeline species endemic to the central Andes. KEY RESULTS: Moderate to high levels of genetic diversity and low genetic differentiation were detected in both adults and seedlings, with levels of genetic diversity and differentiation being almost identical. Four slightly genetically divergent clusters were identified that accorded to differing geographical regions. Genetic diversity decreased from south to north and with increasing precipitation for adults and seedlings, but there was no relationship to elevation. CONCLUSIONS: Our study shows that, unlike the case for other Andean treeline species, recent human activities have not affected the genetic structure of P. tarapacana, possibly because its inhospitable habitat is unsuitable for agriculture. The current genetic pattern of P. tarapacana points to a historically more widespread distribution at lower altitudes, which allowed considerable gene flow possibly during the glacial periods of the Pleistocene epoch, and also suggests that the northern Argentinean Andes may have served as a refugium for historical populations.

Staged invasions across disparate grasslands: effects of seed provenance, consumers and disturbance on productivity and species richness.

Exotic plant invasions are thought to alter productivity and species richness, yet these patterns are typically correlative. Few studies have experimentally invaded sites and asked how addition of novel species influences ecosystem function and community structure and examined the role of competitors and/or consumers in mediating these patterns. We invaded disturbed and undisturbed subplots in and out of rodent exclosures with seeds of native or exotic species in grasslands in Montana, California and Germany. Seed addition enhanced aboveground biomass and species richness compared with no-seeds-added controls, with exotics having disproportionate effects on productivity compared with natives. Disturbance enhanced the effects of seed addition on productivity and species richness, whereas rodents reduced productivity, but only in Germany and California. Our results demonstrate that experimental introduction of novel species can alter ecosystem function and community structure, but that local filters such as competition and herbivory influence the magnitude of these impacts.

Functional importance of avian seed dispersers changes in response to human-induced forest edges in tropical seed-dispersal networks.

Although seed-dispersal networks are increasingly used to infer the functioning of ecosystems, few studies have investigated the link between the properties of these networks and the ecosystem function of seed dispersal by animals. We investigate how frugivore communities and seed dispersal change with habitat disturbance and test whether relationships between morphological traits and functional roles of seed dispersers change in response to human-induced forest edges. We recorded interaction frequencies between fleshy fruited plants and frugivorous bird species in tropical montane forests in the Bolivian Andes and recorded functional bird traits (body mass, gape width and wing tip length) associated with quantitative (seed-removal rate) and qualitative (seed-deposition pattern) components of seed-dispersal effectiveness. We found that the abundance and richness of frugivorous birds were higher at forest edges. More fruits were removed and dispersed seeds were less clustered at edges than in the interior. Additionally, functional and interaction diversity were higher at edges than in the interior, but functional and interaction evenness did not differ. Interaction strength of bird species increased with body mass, gape width and wing tip length in the forest interior, but was not related to bird morphologies at forest edges. Our study suggests that increases in functional and interaction diversity and an even distribution of interaction strength across bird morphologies lead to enhanced quantity and tentatively enhanced quality of seed dispersal. It also suggests that the effects of species traits on ecosystem functions can vary along small-scale gradients of human disturbance.

Plant species phenology differs between climate and land-use scenarios and relates to plant functional traits.

Phenological shifts due to changing climate are often highly species and context specific. Land-use practices such as mowing or grazing directly affect the phenology of grassland species, but it is unclear if plants are similarly affected by climate change in differently managed grassland systems such as meadows and pastures. Functional traits have a high potential to explain phenological shifts and might help to understand species-specific and land-use-specific phenological responses to changes in climate. In the large-scale field experiment Global Change Experimental Facility (GCEF), we monitored the first flowering day, last flowering day, flowering duration, and day of peak flowering, of 17 herbaceous grassland species under ambient and future climate conditions, comparing meadows and pastures. Both climate and land use impacted the flowering phenology of plant species in species-specific ways. We did not find evidence for interacting effects of climate and land-use type on plant phenology. However, the data indicate that microclimatic and microsite conditions on meadows and pastures were differently affected by future climate, making differential effects on meadows and pastures likely. Functional traits, including the phenological niche and grassland utilization indicator values, explained species-specific phenological climate responses. Late flowering species and species with a low mowing tolerance advanced their flowering more strongly under future climate. Long flowering species and species following an acquisitive strategy (high specific leaf area, high mowing tolerance, and high forage value) advanced their flowering end more strongly and thus more strongly shortened their flowering under future climate. We associated these trait-response relationships primarily with a phenological drought escape during summer. Our results provide novel insights on how climate and land use impact the flowering phenology of grassland species and we highlight the role of functional traits in mediating phenological responses to climate.

Habitat fragmentation and recent bottlenecks influence genetic diversity and differentiation of the Central European halophyte Suaeda maritima (Chenopodiaceae).

PREMISE OF THE STUDY: Central European salt habitats are mainly restricted to the maritime coast but scattered occurrences can also be found inland. In inland habitats, human activities have caused losses and reductions in the size of natural salt sites but have also created new anthropogenic habitats around potash mining dumps colonized by halophytic species in the last 30 yr. We aimed to investigate the effects of bottlenecks, isolation, and ongoing habitat fragmentation on the genetic variation of a species commonly growing in these special habitats. METHODS: We used 10 microsatellite markers to compare genetic diversity and differentiation of 31 populations of Suaeda maritima (Chenopodiaceae) from Central European coasts and inland habitats. Two approaches were applied to analyze the tetraploid data based on allele frequencies directly derived from microsatellite data and from transformed binary data. KEY RESULTS: In comparison to the coastal populations from the North Sea and the English Channel, significantly reduced genetic variation and increased between-population differentiation was revealed for populations from the German inland and the Baltic Sea coast. Genetic structure analyses clearly separated coastal and inland populations. CONCLUSIONS: Our results indicate that gene flow is restricted among populations from inland salt sites and the Baltic Sea coast, presumably due to their isolation, small sizes, genetic bottlenecks and/or founder events. Patterns of allele distribution indicate some occasional genetic exchange among habitat types in the past. Anthropogenic salt sites may facilitate gene flow among inland salt habitats preventing endangered inland halophyte populations from genetic erosion.

Gene flow and genetic diversity in cultivated and wild cacao (Theobroma cacao) in Bolivia.

PREMISE OF THE STUDY: The role of pollen flow within and between cultivated and wild tropical crop species is little known. To study the pollen flow of cacao, we estimated the degree of self-pollination and pollen dispersal distances as well as gene flow between wild and cultivated cacao (Theobroma cacao L.). METHODS: We studied pollen flow and genetic diversity of cultivated and wild cacao populations by genotyping 143 wild and 86 cultivated mature plants and 374 seedlings raised from 19 wild and 25 cultivated trees at nine microsatellite loci. KEY RESULTS: A principal component analysis distinguished wild and cultivated cacao trees, supporting the notion that Bolivia harbors truly wild cacao populations. Cultivated cacao had a higher level of genetic diversity than wild cacao, presumably reflecting the varied origin of cultivated plants. Both cacao types had high outcrossing rates, but the paternity analysis revealed 7-14% self-pollination in wild and cultivated cacao. Despite the tiny size of the pollinators, pollen was transported distances up to 3 km; wild cacao showed longer distances (mean = 922 m) than cultivated cacao (826 m). Our data revealed that 16-20% of pollination events occurred between cultivated and wild populations. CONCLUSIONS: We found evidence of self-pollination in both wild and cultivated cacao. Pollination distances are larger than those typically reported in tropical understory tree species. The relatively high pollen exchange from cultivated to wild cacao compromises genetic identity of wild populations, calling for the protection of extensive natural forest tracts to protect wild cacao in Bolivia.

FunAndes - A functional trait database of Andean plants.

We introduce the FunAndes database, a compilation of functional trait data for the Andean flora spanning six countries. FunAndes contains data on 24 traits across 2,694 taxa, for a total of 105,466 entries. The database features plant-morphological attributes including growth form, and leaf, stem, and wood traits measured at the species or individual level, together with geographic metadata (i.e., coordinates and elevation). FunAndes follows the field names, trait descriptions and units of measurement of the TRY database. It is currently available in open access in the FIGSHARE data repository, and will be part of TRY's next release. Open access trait data from Andean plants will contribute to ecological research in the region, the most species rich terrestrial biodiversity hotspot.

Increased genetic differentiation but no reduced genetic diversity in peripheral vs. central populations of a steppe grass.

PREMISE OF THE STUDY: Intraspecific genetic variation is essential for the performance and evolution of species. Populations at a species' geographic range periphery receive considerable attention in biogeography and conservation because they are smaller and spatially more isolated than central populations, a pattern expected to lead to higher genetic differentiation and lower within-population genetic diversity. We tested these predictions in central and peripheral populations of the Eurasian steppe grass Stipa capillata. METHODS: We analyzed AFLP fingerprint patterns in 319 individuals from 20 large and abundant populations in the core, in Kazakhstan, and 23 small and isolated populations at the periphery, in Central Europe. We calculated different genetic diversity estimates and assessed genetic differentiation among populations by examining F(ST) values, a neighbor-net network, and an AMOVA. KEY RESULTS: As expected, genetic differentiation among populations was significantly larger at the range periphery (F(ST) = 0.415) than in the range core (F(ST) = 0.164). In contrast to predictions, however, we found similarly low genetic diversity within central (proportion of polymorphic bands = 21.9%) and peripheral (20%) populations. CONCLUSIONS: Higher genetic differentiation in the small and spatially isolated peripheral populations is likely driven by genetic drift and reduced gene flow due to a complex landscape structure and the abandonment of traditional management regimes. With regard to unchanged genetic diversity, it appears that life-history traits like longevity or sufficiently large population sizes could allow S. capillata to escape deleterious effects at the range edge.

Range-wide genetic structure and diversity of the endemic tree line species Polylepis australis (Rosaceae) in Argentina.

PREMISE OF THE STUDY: Knowledge on the range-wide distribution of genetic structure and diversity is required to facilitate the understanding of historical tree migration and for predicting responses to current climate change. With respect to post-glacial migration patterns known from the northern hemisphere, we tested the prediction that the southernmost populations of a subtropical tree line species have lower within-population genetic diversity and higher genetic differentiation than the central and northernmost populations. METHODS: We used AFLP to assess the genetic structure of 18 populations of the wind-pollinated Polylepis australis (Rosaceae) sampled over its entire distributional range in three Argentinean high mountain regions. Genetic diversity was calculated as a percentage of polymorphic bands (P) and Nei's expected heterozygosity (He); genetic differentiation was assessed using AMOVA, Φ(ST)--statistics, and Bayesian cluster analysis. KEY RESULTS: Contrary to our expectations, the northernmost Polylepis australis stands had lower within-population genetic diversity and higher genetic differentiation than the central and southernmost stands. Populations grouped into two major clusters, the first containing the southern populations and four central populations and the second containing the northern and one central population. CONCLUSIONS: Patterns of Polylepis australis genetic structure and diversity differ from historical migration scenarios observed for the northern hemisphere. The decline in genetic diversity toward the north may point to an equatorward migration following past climatic changes. Populations within the south and central part appear to be connected by effective long-distance pollination while gene flow in the northern part is probably hampered by geographic isolation.

Abundance, origin, and phylogeny of plants do not predict community-level patterns of pathogen diversity and infection.

Pathogens have the potential to shape plant community structure, and thus, it is important to understand the factors that determine pathogen diversity and infection in communities. The abundance, origin, and evolutionary relationships of plant hosts are all known to influence pathogen patterns and are typically studied separately. We present an observational study that examined the influence of all three factors and their interactions on the diversity of and infection of several broad taxonomic groups of foliar, floral, and stem pathogens across three sites in a temperate grassland in the central United States. Despite that pathogens are known to respond positively to increases in their host abundances in other systems, we found no relationship between host abundance and either pathogen diversity or infection. Native and exotic plants did not differ in their infection levels, but exotic plants hosted a more generalist pathogen community compared to native plants. There was no phylogenetic signal across plants in pathogen diversity or infection. The lack of evidence for a role of abundance, origin, and evolutionary relationships in shaping patterns of pathogens in our study might be explained by the high generalization and global distributions of our focal pathogen community, as well as the high diversity of our plant host community. In general, the community-level patterns of aboveground pathogen infections have received less attention than belowground pathogens, and our results suggest that their patterns might not be explained by the same drivers.

Release from natural enemies mitigates inbreeding depression in native and invasive Silene latifolia populations.

Inbreeding and enemy infestation are common in plants and can synergistically reduce their performance. This inbreeding ×environment (I × E) interaction may be of particular importance for the success of plant invasions if introduced populations experience a release from attack by natural enemies relative to their native conspecifics. Here, we investigate whether inbreeding affects plant infestation damage, whether inbreeding depression in growth and reproduction is mitigated by enemy release, and whether this effect is more pronounced in invasive than native plant populations. We used the invader Silene latifolia and its natural enemies as a study system. We performed two generations of experimental out- and inbreeding within eight native (European) and eight invasive (North American) populations under controlled conditions using field-collected seeds. Subsequently, we exposed the offspring to an enemy exclusion and inclusion treatment in a common garden in the species' native range to assess the interactive effects of population origin (range), breeding treatment, and enemy treatment on infestation damage, growth, and reproduction. Inbreeding increased flower and leaf infestation damage in plants from both ranges, but had opposing effects on fruit damage in native versus invasive plants. Inbreeding significantly reduced plant fitness; whereby, inbreeding depression in fruit number was higher in enemy inclusions than exclusions. This effect was equally pronounced in populations from both distribution ranges. Moreover, the magnitude of inbreeding depression in fruit number was lower in invasive than native populations. These results support that inbreeding has the potential to reduce plant defenses in S. latifolia, which magnifies inbreeding depression in the presence of enemies. However, future studies are necessary to further explore whether enemy release in the invaded habitat has actually decreased inbreeding depression and thus facilitated the persistence of inbred founder populations and invasion success.

Projected impacts of climate change on functional diversity of frugivorous birds along a tropical elevational gradient.

Climate change forces many species to move their ranges to higher latitudes or elevations. Resulting immigration or emigration of species might lead to functional changes, e.g., in the trait distribution and composition of ecological assemblages. Here, we combined approaches from biogeography (species distribution models; SDMs) and community ecology (functional diversity) to investigate potential effects of climate-driven range changes on frugivorous bird assemblages along a 3000 m elevational gradient in the tropical Andes. We used SDMs to model current and projected future occurrence probabilities of frugivorous bird species from the lowlands to the tree line. SDM-derived probabilities of occurrence were combined with traits relevant for seed dispersal of fleshy-fruited plants to calculate functional dispersion (FDis; a measure of functional diversity) for current and future bird assemblages. Comparisons of FDis between current and projected future assemblages showed consistent results across four dispersal scenarios, five climate models and two representative concentration pathways. Projections indicated a decrease of FDis in the lowlands, an increase of FDis at lower mid-elevations and little changes at high elevations. This suggests that functional dispersion responds differently to global warming at different elevational levels, likely modifying avian seed dispersal functions and plant regeneration in forest ecosystems along tropical mountains.