Intraspecific trait variation across elevation predicts a widespread tree species' climate niche and range limits

Global change is widely altering environmental conditions which makes accurately predicting species range limits across natural landscapes critical for conservation and management decisions. If climate pressures along elevation gradients influence the distribution of phenotypic and genetic variation of plant functional traits, then such trait variation may be informative of the selective mechanisms and adaptations that help define climatic niche limits. Using extensive field surveys along 16 elevation transects and a large common garden experiment, we tested whether functional trait variation could predict the climatic niche of a widespread tree species (Populus angustifolia) with a double quantile regression approach. We show that intraspecific variation in plant size, growth, and leaf morphology corresponds with the species' total climate range and certain climatic limits related to temperature and moisture extremes. Moreover, we find evidence of genetic clines and phenotypic plasticity at environmental boundaries, which we use to create geographic predictions of trait variation and maximum values due to climatic constraints across the western US. Overall, our findings show the utility of double quantile regressions for connecting species distributions and climate gradients through trait‐based mechanisms. We highlight how new approaches like ours that incorporate genetic variation in functional traits and their response to climate gradients will lead to a better understanding of plant distributions as well as identifying populations anticipated to be maladapted to future environments.     

Genetic variation in a geographically restricted and two widespread species of South American Nothofagus

The amount and distribution of genetic variation is compared using starch gel electrophoresis among populations of the three evergreen species of South American Nothofagus : the geographically restricted Nothofagus nitida (Phil.) Krasser and the widespread Nothofagus betuloides (Mirb.) Oerst. and Nothofagus dombeyi (Mirb.) Oerst. Ten enzyme systems were resolved coding for fifteen putative genetic loci. N. betuloides and N. dombeyi were more genetically variable than N. nitida ; they had higher total number of alleles, mean number of alleles per locus, percent of polymorphic loci, mean expected heterozygosity, and mean total genetic diversity. These results are in agreement with the hypothesis that widespread species are often associated with historically large and more continuously distributed populations which in turn can maintain higher levels of genetic variation. Conversely, the genetic structure of N. nitida including its low genetic identity with the other two species and the presence of four unique alleles support the hypothesis that N. nitida has been isolated from the other two species for a considerable period of time. Genetic data in concert with the fossil record indicate that these taxa may be members of a pre-Pleistocene flora and consequently their genetic structures reflect a more ancient evolutionary history than previously hypothesized.     

Effect of volcanic ash deposition on length and radial growths of a deciduous montane tree (Nothofagus pumilio)

Extreme environmental events such as volcanic eruptions can trigger plant responses that largely exceed those recorded for moderate‐intensity disturbances. We assessed the effects of the June 2011 eruption of the Puyehue – Cordón Caulle volcano on the length and radial growths of juvenile Nothofagus pumilio trees at two sites located 20 (with >40 cm ash accretion) and 75 (without ash) km from the volcano. Variations in length and radial growth were evaluated for the periods 1999–2013 and 1993–2013 respectively; pre‐ and post‐eruption growth rates were computed. The length growth of the N. pumilio trees located close to the volcano increased significantly after the eruption: shoot extensions during the growing season after the eruption were, on average, two to three times longer than average according to ontogenetic growth trends. Variations in radial growth after the eruption were comparatively less noticeable than those in length growth. No significant effects of the eruption were observed in those trees located 75 km from the volcano. In order to explain the exceptionally positive response of N. pumilio's length growth to the volcanic eruption, three non‐exclusive explanations were proposed: (i) thick ash layers increase water retention in the soil; (ii) volcanic ash facilitates the access of plants to nutrients; and (iii) volcanic ashes decrease herbivory and competition. The comparatively lower sensitivity of radial growth to this extreme volcanic event is also noteworthy. These findings highlight the need to further examine how large‐scale volcanic events influence structure and/or functioning of ecosystem in the Patagonian forest.     

Intraspecific trait variation increases species diversity in a trait‐based grassland model

Intraspecific trait variation (ITV) is thought to play a significant role in community assembly, but the magnitude and direction of its influence are not well understood. Although it may be critical to better explain population persistence, species interactions, and therefore biodiversity patterns, manipulating ITV in experiments is challenging. We therefore incorporated ITV into a trait‐ and individual‐based model of grassland community assembly by adding variation to the plants’ functional traits, which then drive life‐history tradeoffs. Varying the amount of ITV in the simulation, we examine its influence on pairwise‐coexistence and then on the species diversity in communities of different initial sizes. We find that ITV increases the ability of the weakest species to invade most, but that this effect does not scale to the community level, where the primary effect of ITV is to increase the persistence and abundance of the competitively‐average species. Diversity of the initial community is also of critical importance in determining ITV's efficacy; above a threshold of interspecific diversity, ITV does not increase diversity further. For communities below this threshold, ITV mainly helps to increase diversity in those communities that would otherwise be low‐diversity. These findings suggest that ITV actively maintains diversity by helping the species on the margins of persistence, but mostly in habitats of relatively low alpha and beta diversity.     

Intraspecific trait variation of woody species reduced in a savanna community,southwest China

Plants deploy various ecological strategies in response to environmental heterogeneity. In many forest ecosystems, plants have been reported to have notable inter- and intra-specific trait variation, as well as clear phylogenetic signals, indicating that these species possess a degree of phenotypic plasticity to cope with habitat variation in the community. Savanna communities, however, grow in an open canopy structure and exhibit little species diversification, likely as a result of strong environmental stress. In this study, we hypothesized that the phylogenetic signals of savanna species would be weak, the intraspecific trait variation (ITV) would be low, and the contribution of intraspecific variation to total trait variance would be reduced, owing to low species richness, multiple stresses and relatively homogenous community structure. To test these hypotheses, we sampled dominant woody species in a dry-hot savanna in southwestern China, focusing on leaf traits related to adaptability of plants to harsh conditions (year-round intense radiation, low soil fertility and seasonal droughts). We found weak phylogenetic signals in leaf traits and low ITV (at both individual and canopy-layer levels). Intraspecific variation (including leaf-, layer- and individual-scales) contributed little to the total trait variance, whereas interspecific variation and variation in leaf phenology explained substantial variance. Our study suggests that intraspecific trait variation is reduced in savanna community. Furthermore, our findings indicate that classifying species by leaf phenology may help better understand how species coexist under similar habitats with strong stresses.     

Isozyme polymorphisms provide evidence of clinal variation with elevation in Nothofagus pumilio

Variable physical conditions along elevational gradients strongly influence patterns of genetic differentiation in tree species. Here, the hypothesis is tested that different growth forms of Nothofagus pumilio, which characterizes the subalpine forests in the southern Andes, will display continuous genetic variation with elevation. At each of four elevational strips in three different mountain ranges, fresh leaf tissue was sampled from 30 randomly selected individuals to be analyzed by protein electrophoresis. Allelic frequencies were used to test for heterogeneity across populations and to classify populations into different elevational strips by discriminant analysis. The degree of population divergence was estimated by F(ST). Clinical variation on within-population genetic characteristics was analyzed by linear regressions against elevation. Seven enzyme systems coded for 14 putative isozyme loci, 57% of which were polymorphic in at least one population. Allele frequencies significantly varied with elevation and discriminant analysis separated populations at different elevational strips. Among-population divergence within any mountain range was small, but greater than among different mountain ranges. Overall, low-elevation populations were more variable than high-elevation populations, and regression analyses suggested continuous variation in populations of N. pumilio 100 m apart. Marked stepwise phenological differences on mountain slopes are most probably responsible for the isolation of nearby populations.     

Intraspecific trait variation and the differential decline of meadow species during conifer encroachment

Conifer encroachment has reduced the extent and habitat quality of mountain meadows throughout western North America. Past studies in the Cascade Range of Oregon reveal surprising variation in the pace at which meadow species are lost to encroachment. We hypothesized that this variation relates to intraspecific variability in plant functional traits that are adaptive as light levels decline during the transition from open meadow to closed forest. For 13 meadow species with varying sensitivities to encroachment, we compared how the rate of decline in abundance relates to intraspecific variation in three morphological traits (specific leaf area, shoot/root ratio, and shoot height) and to clonal ability (no, limited, or strong potential for vegetative spread). For each species, we computed an index of sensitivity to encroachment, ISE, the coefficient of variation in cover across the light gradient. For each trait of each species, we computed an index of variation, the linear slope of the relationship between trait values and available light. For most traits, the correlation between ISE and trait variation (or clonality) was weak. Although specific leaf area increased in the shade for all species, the magnitude of increase did not correlate with ISE. Only variability in leaf area was positively correlated with ISE, increasing in the shade for less sensitive species and decreasing for more sensitive species. Responses to encroachment may reflect differences in species’ physiological rather than morphological variability, or species may be responding to changes in resources other than, or in addition to, light.     

Floral trait variation in fourCyclamen (Primulaceae) species

The purpose of this study is to examine floral trait variation between fourCyclamen species that show variation in their ability to reproduce in the absence of pollinators and in levels of inbreeding. Pollen and ovule production, pollen/ovule ratio, pollen volume, petal length and width, diameter of the corolla mouth, pistil and stamen length, and stigma-anther separation varied significantly between the four study species. Flower, pollen and ovule production, pollen volume and corolla size were generally highest inC. hederifolium, the species with the lowest level of inbreeding (mean F_is = 0.329), intermediate in both species with relatively high levels of pollinator-mediated inbreeding,C. repandum (mean F_is = 0.658) andC. creticum (mean F_is = 0.748), and lowest in the highly inbredC. balearicum (mean F_is = 0.930). The two species with the most different inbreeding coefficients,C. hederifolium andC. balearicum, had lower pollen-ovule ratios and shorter longevities of stigma receptivity and pollen viability thanC. creticum andC. repandum. These patterns of variation in floral traits are discussed in relation to the relatedness, pollination ecology and levels of inbreeding of the four species.     

New Cortinarius species from Nothofagus forests in South Chile

Four new Cortinarius species are described from Nothofagus forests in South Chile. Cortinarius aurantiorufus and C. punctatisporus, subgenus Phlegmacium, stirps Inflatipes, are mainly characterized by a viscid to glutinous pileus and a bulbous whitish stipe. They differ in the color of the pileus, and shape, ornamentation, and size of the basidiospores. Futhermore, C. punctatisporus has a translucently striate pileus. Cortinarius rubrivelatus and C. parahumilis belong to subgenus Telamonia, stirps Brunneivelatus and Scabrisporus, respectively. Cortinarius rubrivelatus has a reddish veil, a viscid pileus, and large, ellipsoid to amygdaliform basidiospores. Cortinarius parahumilis has small, subglobose to broadly elliptical, minutely verrucose basidiospores and a viscid pileus.     

Intraspecific variation and species coexistence

We use a two-species model of plant competition to explore the effect of intraspecific variation on community dynamics. The competitive ability ("performance") of each individual is assigned by an independent random draw from a species-specific probability distribution. If the density of individuals competing for open space is high (e.g., because fecundity is high), species with high maximum (or large variance in) performance are favored, while if density is low, species with high typical (e.g., mean) performance are favored. If there is an interspecific mean-variance performance trade-off, stable coexistence can occur across a limited range of intermediate densities, but the stabilizing effect of this trade-off appears to be weak. In the absence of this trade-off, one species is superior. In this case, intraspecific variation can blur interspecific differences (i.e., shift the dynamics toward what would be expected in the neutral case), but the strength of this effect diminishes as competitor density increases. If density is sufficiently high, the inferior species is driven to extinction just as rapidly as in the case where there is no overlap in performance between species. Intraspecific variation can facilitate coexistence, but this may be relatively unimportant in maintaining diversity in most real communities.     

Differential hypogeous sporocarp production from Nothofagus dombeyi and N. pumilio forests in southern Argentina

Mycorrhizal fungi that form hypogeous sporocarps are an important component of the temperate forest soil community. In many regions, such as the Nothofagus forest in the Patagonian Andes, this group of fungi has been poorly studied. Here we examined the spring and autumn community composition of "sequestrate fungi", based on sporocarp production in pure forests of Nothofagus dombeyi (evergreen) and N. pumilio (deciduous). We investigated the possible relationships between these communities and environmental factors over 2 y. The rarefaction curves and the minimal richness estimates converged at nearly the same level for each forest type, and the asymptotes suggested that the sampling effort was sufficient to capture most of the hypogeous sporocarp richness in these forest stands. In total 27 species were recovered. Basidiomycota, Ascomycota and Glomeromycota respectively accounted for nine, two and one genera. Species richness of hypogeous sporocarps varied in relation to forest type but not to season (fall and spring), whereas sporocarp biomass varied according to an interaction between season and forest type. Species richness and sporocarp biomass were positively correlated with rainfall and negatively correlated with altitude. In addition sporocarp species richness was positively related to number of trees per transect. We found that two different forest stands, each dominated by different species of Nothofagus, exhibited different hypogeous sporocarp communities.     

Intraspecific trait variation and allocation strategies of calcareous grassland species: Results from a restoration experiment

Intra- and interspecific trait variation express the response of plants dealing with different environmental conditions. We measured root and leaf traits on 14 species of calcareous grasslands in a restoration experiment. We aimed at identifying intraspecific differences in biomass allocation and functional plant traits under contrasting soil conditions by comparing plants growing in ancient grassland and two restored grasslands on ex-arable land, one of them with topsoil removal. Relative importance of trait variation within and among species, and among site was assessed by variance partitioning. Interspecific variation was more important than intraspecific variation, but the contribution of the latter to total variation was considerable, especially for specific leaf area. Changes in soil properties due to topsoil removal resulted in lower values of plant height, specific leaf area and specific root length compared to the control (ancient grassland). Soil fertility found in the treatment without top soil removal did not affect plant plasticity compared to the control. The study species showed two allocation strategies in relation to resource stress, while the responses of individual traits to the soil treatments were consistent across species. We conclude that caution must be taken when using mean trait values for plastic species or when working with environmental gradients.     

Geographic variation in a widespread neotropical species,Mouriri myrtilloides (Melastomataceae)

Geographic variation inMouriri myrtilloides (Swartz) Poiret is analyzed on a morphological basis. Plants from Central America have medium puberulence, long calyx lobes, and short petioles and pedicels; those from Jamaica and Haiti are glabrous and have short calyx lobes, petioles, and pedicels; while those from Cuba have maximum puberulence, medium calyx lobes and pedicels, and long petioles. Glabrous or near-glabrous plants also appear rarely and more or less at random in Central and South America. Distribution in South America is limited to the northwest quarter of the continent. Most plants of this region are similar to those of Central America except that they have slightly shorter calyx lobes. However, the very short calyx lobes of plants from Jamaica and Haiti often occur in South America and rarely in Panama. Furthermore, most features of the Cuban plants appear in those of the Orinoco Basin, while individuals with one of these features, strong puberulence, are occasional elsewhere in South America. It is suggested that the complex originated in northwest South America and diversified there, subsequently radiating north and west. Considerations and problems related to such a dispersal are discussed. Taxonomically the complex is treated as consisting of four subspecies: ssp.parvifolia of Central America and much of the north-west quarter of South America, ssp.myrtilloides of Jamaica and southwest Haiti, ssp.acuta of Cuba, and ssp.orinocensis of the Orinoco Basin, the latter being a new taxon.     

Intraspecific trait variation in three common grass species reveals finescale species adjustment to local environmental conditions

Aims Studies along environmental gradients have shown that intraspecific trait variation (ITV) may contribute considerably to community-level trait variation. However, we lack knowledge about how the extent of ITV varies on a local scale and whether a varying extent of ITV is related to differences in local environmental site and plant community characteristics.     

Light-dependent leaf trait variation in 43 tropical dry forest tree species

Our understanding of leaf acclimation in relation to irradiance of fully grown or juvenile trees is mainly based on research involving tropical wet forest species. We studied sun-shade plasticity of 24 leaf traits of 43 tree species in a Bolivian dry deciduous forest. Sampling was confined to small trees. For each species, leaves were taken from five of the most and five of the least illuminated crowns. Trees were selected based on the percentage of the hemisphere uncovered by other crowns. We examined leaf trait variation and the relation between trait plasticity and light demand, maximum adult stature, and ontogenetic changes in crown exposure of the species. Leaf trait variation was mainly related to differences among species and to a minor extent to differences in light availability. Traits related to the palisade layer, thickness of the outer cell wall, and N(area) and P(area) had the greatest plasticity, suggesting their importance for leaf function in different light environments. Short-lived pioneers had the highest trait plasticity. Overall plasticity was modest and rarely associated with juvenile light requirements, adult stature, or ontogenetic changes in crown exposure. Dry forest tree species had a lower light-related plasticity than wet forest species, probably because wet forests cast deeper shade. In dry forests light availability may be less limiting, and low water availability may constrain leaf trait plasticity in response to irradiance.     

Simulated warming does not impair seedling survival and growth of Nothofagus pumilio in the southern Andes

It has been predicted that subalpine forests will be negatively affected by global warming; however, direct responses to experimental warming have been scarcely examined in these systems. In this study we evaluated the effects of higher temperatures with and without water addition on the survival and growth of recently emerged (small) and large seedlings of the widely distributed species Nothofagus pumilio in subalpine forests of the southern Chilean Andes. We also examined the variations in seedling traits related to carbon balance in order to infer the causal mechanisms of survival and growth responses. Treatments of open top chambers (OTCs) were combined with watering in two locations with differing climates: Antillanca (40°S, humid) and Cerro Castillo (46°S, drier). OTCs increased mean and maximum air temperatures by 0.6 °C and 2–3 °C, respectively, and decreased soil humidity by 56% in Antillanca and 30% in Cerro Castillo, fulfilling methodological expectations and climate model predictions. After two complete growing seasons, the survival, relative growth rate (RGR), biomass, and a suite of seedling traits were measured and analyzed using mixed-effects models. Warming and warming in combination with watering significantly increased large seedling survival in Cerro Castillo. In Antillanca, warmer conditions increased the height, biomass, and leaf area of small seedlings, and the RGR of large seedlings. In this location, warming also caused lower leaf carbon isotopic composition in both age classes and higher specific leaf area in small seedlings, suggesting whole-plant carbon gain improvements; warming did not produce any drought effects. Our results indicate that warming produces positive effects on the seedling establishment of N. pumilio in the southern Andes, highlighting the importance of site-specific effects in response to climate change in widespread species. Site-specific effects can most likely explain the discrepancies between the results of this study and the predictions outlined by previous studies for these forests.     

Genetic diversity in Nothofagus alessandrii (Fagaceae), an endangered endemic tree species of the coastal maulino forest of Central Chile

BACKGROUND AND AIMS: The endemic tree Nothofagus alessandrii (Fagaceae) has been historically restricted to the coastal range of Region VII of central Chile, and its forests have been increasingly destroyed and fragmented since the end of the 19th century. In this study, the patterns of within- and among-population genetic diversity in seven fragments of this endangered narrowly endemic tree were examined. METHODS: Allozyme electrophoresis of seven loci of N. alessandrii was used to estimate genetic diversity, genetic structure and gene flow. KEY RESULTS: High levels of genetic diversity were found as shown by mean expected heterozygosity (H(e) = 0.182 +/- 0.034), percentage of polymorphic loci (P(p) = 61.2 %), mean number of alleles per locus (A = 1.8) and mean number of alleles per polymorphic locus (A(p) = 2.3). Genetic differentiation was also high (G(ST) = 0.257 and Nm = 0.7). These values are high compared with more widespread congeneric species. CONCLUSIONS: Despite its endemic status and restricted geographical range N. alessandrii showed high levels of genetic diversity. The observed patterns of diversity are explained in part by historical processes and more recent human fragmentation.