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Strasburg, J. L., Scotti-Saintagne, C., Scotti, I., Lai, Z., & Rieseberg, L. H. (2009). Genomic Patterns of Adaptive Divergence between Chromosomally Differentiated Sunflower Species. Mol. Biol. Evol., 26(6), 1341–1355.
Abstract: Understanding the genetic mechanisms of speciation and basis of species differences is among the most important challenges in evolutionary biology. Two questions of particular interest are what roles divergent selection and chromosomal differentiation play in these processes. A number of recently proposed theories argue that chromosomal rearrangements can facilitate the development and maintenance of reproductive isolation and species differences by suppressing recombination within rearranged regions. Reduced recombination permits the accumulation of alleles contributing to isolation and adaptive differentiation and protects existing differences from the homogenizing effects of introgression between incipient species. Here, we examine patterns of genetic diversity and divergence in rearranged versus collinear regions in two widespread, extensively hybridizing sunflower species, Helianthus annuus and Helianthus petiolaris, using sequence data from 77 loci distributed throughout the genomes of the two species. We find weak evidence for increased genetic divergence near chromosomal break points but not within rearranged regions overall. We find no evidence for increased rates of adaptive divergence on rearranged chromosomes; in fact, collinear chromosomes show a far greater excess of fixed amino acid differences between the two species. A comparison with a third sunflower species indicates that much of the nonsynonymous divergence between H. annuus and H. petiolaris probably occurred during or soon after their formation. Our results suggest a limited role for chromosomal rearrangements in genetic divergence, but they do document substantial adaptive divergence and provide further evidence of how species integrity and genetic identity can be maintained at many loci in the face of extensive hybridization and gene flow.
Keywords: species boundaries; chromosomal rearrangements; positive selection; hybridization; sunflowers; Helianthus
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Franklin, J., Andrade, R., Daniels, M. L., Fairbairn, P., Fandino, M. C., Gillespie, T. W., et al. (2018). Geographical ecology of dry forest tree communities in the West Indies. J Biogeogr, 45(5), 1168–1181.
Abstract: Abstract Aim Seasonally dry tropical forest (SDTF) of the Caribbean Islands (primarily West Indies) is floristically distinct from Neotropical SDTF in Central and South America. We evaluate whether tree species composition was associated with climatic gradients or geographical distance. Turnover (dissimilarity) in species composition of different islands or among more distant sites would suggest communities structured by speciation and dispersal limitations. A nested pattern would be consistent with a steep resource gradient. Correlation of species composition with climatic variation would suggest communities structured by broad-scale environmental filtering. Location The West Indies (The Bahamas, Cuba, Hispaniola, Jamaica, Puerto Rico, US Virgin Islands, Guadeloupe, Martinique, St. Lucia), Providencia (Colombia), south Florida (USA) and Florida Keys (USA). Taxon Seed plants?woody taxa (primarily trees). Methods We compiled 572 plots from 23 surveys conducted between 1969 and 2016. Hierarchical clustering of species in plots, and indicator species analysis for the resulting groups of sites, identified geographical patterns of turnover in species composition. Nonparametric analysis of variance, applied to principal components of bioclimatic variables, determined the degree of covariation in climate with location. Nestedness versus turnover in species composition was evaluated using beta diversity partitioning. Generalized dissimilarity modelling partitioned the effect of climate versus geographical distance on species composition. Results Despite a set of commonly occurring species, SDTF tree community composition was distinct among islands and was characterized by spatial turnover on climatic gradients that covaried with geographical gradients. Greater Antillean islands were characterized by endemic indicator species. Northern subtropical areas supported distinct, rather than nested, SDTF communities in spite of low levels of endemism. Main conclusions The SDTF species composition was correlated with climatic variation. SDTF on large Greater Antillean islands (Hispaniola, Jamaica and Cuba) was characterized by endemic species, consistent with their geological history and the biogeography of plant lineages. These results suggest that both environmental filtering and speciation shape Caribbean SDTF tree communities.
Keywords: beta diversity; Caribbean; community composition; seasonally dry tropical forest; species turnover; tropical dry forest; West Indies
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Fukami, T., Nakajima, M., Fortunel, C., Fine, P. V. A., Baraloto, C., Russo, S. E., et al. (2017). Geographical variation in community divergence: insights from tropical forest monodominance by ectomycorrhizal trees. American Naturalist, 190, S105–S122.
Abstract: Convergence occurs in both species traits and community structure, but how convergence at the two scales influences each other remains unclear. To address this question, we focus on tropical forest monodominance, in which a single, often ectomycorrhizal (EM) tree species occasionally dominates forest stands within a landscape otherwise characterized by diverse communities of arbuscular mycorrhizal (AM) trees. Such monodominance is a striking potential example of community divergence resulting in alternative stable states. However, it is observed only in some tropical regions. A diverse suite of AM and EM trees locally codominate forest stands elsewhere. We develop a hypothesis to explain this geographical difference using a simulation model of plant community assembly. Simulation results suggest that in a region with a few EM species (e.g., South America), EM trees experience strong selection for convergent traits that match the abiotic conditions of the environment. Consequently, EM species successfully compete against other species to form monodominant stands via positive plant-soil feedbacks. By contrast, in a region with many EM species (e.g., Southeast Asia), species maintain divergent traits because of complex plant-soil feedbacks, with no species having traits that enablemonodominance. An analysis of plant trait data from Borneo and Peruvian Amazon was inconclusive. Overall, this work highlights the utility of geographical comparison in understanding the relationship between trait convergence and community convergence. © 2017 by The University of Chicago.
Keywords: Community assembly; Mycorrhizae; Plant traits; Plant-soil feedback; Priority effects; Species pools
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Chartier, M., Pélozuelo, L., Buatois, B., Bessière, J. - M., & Gibernau, M. (2013). Geographical variations of odour and pollinators, and test for local adaptation by reciprocal transplant of two European Arum species. Funct. Ecol., 27(6), 1367–1381.
Abstract: Interactions between entomophilous plants and their pollinators are one of the major factors shaping the evolution of floral features. As species are distributed in more or less connected populations, they have evolved in a geographical mosaic of co-evolution were the outcome of the plant-pollinator interaction is likely to vary as a result of local adaptations. Arum italicum and Arum maculatum are two species of Araceae which deceive their fly pollinators by mimicking the odour of their oviposition sites. Whereas A. italicum is known to be pollinated by flies belonging to different families (i.e. opportunist), A. maculatum relies on only two pollinating species of the family Psychodidae throughout its European repartition area (i.e. specialist). The interannual and geographical variations of pollinators and pollinator-attractive odours were described in several populations of the two species over two consecutive years. Furthermore, local adaptation to pollinators was tested by transplanting inflorescence-bearing plants between two different sites and by recording the number and composition of the insect fauna trapped inside the inflorescences during anthesis as a measure of a fitness component. Pollinators and pollinator-attractive odours of the two Arum species varied in time and space, but there was no clear odour structure between populations. When transplanted, inflorescences of both species trapped the same composition and number of insects as native inflorescences at a given site; this indicates that pollinator composition is highly dependent on the local availability of insects. No pattern of local adaptation was found for these two species, but local pollination conditions were shown to strongly affect the degree of geographical variations of these interactions. The lack of a clear odour geographical structure might be due to high gene flow or to similar selective pressures exerted by pollinators, and the high interindividual odour variation may be linked to the deceptive strategy adopted by the two plant species. © 2013 British Ecological Society.
Keywords: Deception; Diptera; Floral scent; Geographical mosaic; Psychodidae; Sapromyophily; Transplant experiment
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Guitet, S., Pélissier, R., Brunaux, O., Jaouen, G., & Sabatier, D. (2015). Geomorphological landscape features explain floristic patterns in French Guiana rainforest. Biodiversity and Conservation, 24(5), 1215–1237.
Abstract: Geomorphic landscape features have been suggested as indicators of forest diversity. However, their explanatory power has not yet been explicitly tested at a regional scale in tropical rainforest. We used forest inventories conducted according to a stratified sampling design (3,132 plots in 111 transects at 33 sites) and holistic multi-scale geomorphological mapping derived from a Shuttle Radar Topography Mission digital elevation model to describe and explain spatial patterns in floristic composition across French Guiana (80,000 km2). We measured and identified 123,906 trees with DBH ≥20 cm and used constrained and unconstrained ordinations to analyze variations in the abundance of 221 taxa and 51 families. Variance partitioning and variograms were used to detect spatial patterns in species composition, compare the explanatory power of spatial and environmental factors, and select the variables that best explain forest composition. Strong floristic patterns corresponded to a major latitudinal gradient and significant sub-regional floristic structure. Geomorphological landscapes shaped by historic climate fluctuations and major geological events successfully captured these patterns and explained the variation in abundance of 80 taxa, corresponding to 65 % of the inventoried trees. Our findings suggest that long-term forest dynamics are under substantial “geomorphographic control”. A geomorphological perspective on landscapes that incorporates current and past environmental filters and historical biogeographical processes could thus be used more systematically in tropical regions for regional planning and forest conservation. © 2014, Springer Science+Business Media Dordrecht.
Keywords: Geodiversity; Geomorphology; Landscapes; Species distribution; Tree community
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Thomas, H. J. D., Bjorkman, A. D., Myers-Smith, I. H., Elmendorf, S. C., Kattge, J., Diaz, S., et al. (2020). Global plant trait relationships extend to the climatic extremes of the tundra biome. Nat. Commun., 11(1351).
Abstract: The majority of variation in six traits critical to the growth, survival and reproduction of plant species is thought to be organised along just two dimensions, corresponding to strategies of plant size and resource acquisition. However, it is unknown whether global plant trait relationships extend to climatic extremes, and if these interspecific relationships are confounded by trait variation within species. We test whether trait relationships extend to the cold extremes of life on Earth using the largest database of tundra plant traits yet compiled. We show that tundra plants demonstrate remarkably similar resource economic traits, but not size traits, compared to global distributions, and exhibit the same two dimensions of trait variation. Three quarters of trait variation occurs among species, mirroring global estimates of interspecific trait variation. Plant trait relationships are thus generalizable to the edge of global trait-space, informing prediction of plant community change in a warming world. © 2020, Crown.
Keywords: biome; climate change; extreme event; global change; growth; interspecific interaction; plant community; tundra; article; plant community; prediction; tundra; warming; classification; climate; ecosystem; genetics; plant; plant development; Climate; Ecosystem; Plant Development; Plants; Tundra
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Öpik, M., Zobel, M., Cantero, J. J., Davison, J., Facelli, J. M., Hiiesalu, I., et al. (2013). Global sampling of plant roots expands the described molecular diversity of arbuscular mycorrhizal fungi. Mycorrhiza, 23(5), 411–430.
Abstract: We aimed to enhance understanding of the molecular diversity of arbuscular mycorrhizal fungi (AMF) by building a new global dataset targeting previously unstudied geographical areas. In total, we sampled 96 plant species from 25 sites that encompassed all continents except Antarctica. AMF in plant roots were detected by sequencing the nuclear SSU rRNA gene fragment using either cloning followed by Sanger sequencing or 454-sequencing. A total of 204 AMF phylogroups (virtual taxa, VT) were recorded, increasing the described number of Glomeromycota VT from 308 to 341 globally. Novel VT were detected from 21 sites; three novel but nevertheless widespread VT (Glomus spp. MO-G52, MO-G53, MO-G57) were recorded from six continents. The largest increases in regional VT number were recorded in previously little-studied Oceania and in the boreal and polar climatic zones – this study providing the first molecular data from the latter. Ordination revealed differences in AM fungal communities between different continents and climatic zones, suggesting that both biogeographic history and environmental conditions underlie the global variation of those communities. Our results show that a considerable proportion of Glomeromycota diversity has been recorded in many regions, though further large increases in richness can be expected in remaining unstudied areas. © 2013 Springer-Verlag Berlin Heidelberg.
Keywords: 454-sequencing; Biogeography; Database; Diversity; Fungal macroecology; Glomeromycota
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Bruelheide, H., Dengler, J., Purschke, O., Lenoir, J., Jiménez-Alfaro, B., Hennekens, S. M., et al. (2018). Global trait–environment relationships of plant communities. Nature Ecology & Evolution, 2(12), 1906–1917.
Abstract: Plant functional traits directly affect ecosystem functions. At the species level, trait combinations depend on trade-offs representing different ecological strategies, but at the community level trait combinations are expected to be decoupled from these trade-offs because different strategies can facilitate co-existence within communities. A key question is to what extent community-level trait composition is globally filtered and how well it is related to global versus local environmental drivers. Here, we perform a global, plot-level analysis of trait–environment relationships, using a database with more than 1.1 million vegetation plots and 26,632 plant species with trait information. Although we found a strong filtering of 17 functional traits, similar climate and soil conditions support communities differing greatly in mean trait values. The two main community trait axes that capture half of the global trait variation (plant stature and resource acquisitiveness) reflect the trade-offs at the species level but are weakly associated with climate and soil conditions at the global scale. Similarly, within-plot trait variation does not vary systematically with macro-environment. Our results indicate that, at fine spatial grain, macro-environmental drivers are much less important for functional trait composition than has been assumed from floristic analyses restricted to co-occurrence in large grid cells. Instead, trait combinations seem to be predominantly filtered by local-scale factors such as disturbance, fine-scale soil conditions, niche partitioning and biotic interactions.
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Poyatos, R., Granda, V., Flo, V., Adams, M. A., Adorjan, B., Aguadé, D., et al. (2021). Global transpiration data from sap flow measurements: the SAPFLUXNET database. Earth System Science Data, 13(6), 2607–2649.
Abstract: Plant transpiration links physiological responses of vegetation to water supply and demand with hydrological, energy, and carbon budgets at the land–atmosphere interface. However, despite being the main land evaporative flux at the global scale, transpiration and its response to environmental drivers are currently not well constrained by observations. Here we introduce the first global compilation of whole-plant transpiration data from sap flow measurements (SAPFLUXNET, https://sapfluxnet.creaf.cat/, last access: 8 June 2021). We harmonized and quality-controlled individual datasets supplied by contributors worldwide in a semi-automatic data workflow implemented in the R programming language. Datasets include sub-daily time series of sap flow and hydrometeorological drivers for one or more growing seasons, as well as metadata on the stand characteristics, plant attributes, and technical details of the measurements. SAPFLUXNET contains 202 globally distributed datasets with sap flow time series for 2714 plants, mostly trees, of 174 species. SAPFLUXNET has a broad bioclimatic coverage, with woodland/shrubland and temperate forest biomes especially well represented (80 % of the datasets). The measurements cover a wide variety of stand structural characteristics and plant sizes. The datasets encompass the period between 1995 and 2018, with 50 % of the datasets being at least 3 years long. Accompanying radiation and vapour pressure deficit data are available for most of the datasets, while on-site soil water content is available for 56 % of the datasets. Many datasets contain data for species that make up 90 % or more of the total stand basal area, allowing the estimation of stand transpiration in diverse ecological settings. SAPFLUXNET adds to existing plant trait datasets, ecosystem flux networks, and remote sensing products to help increase our understanding of plant water use, plant responses to drought, and ecohydrological processes. SAPFLUXNET version 0.1.5 is freely available from the Zenodo repository (https://doi.org/10.5281/zenodo.3971689; Poyatos et al., 2020a). The “sapfluxnetr” R package – designed to access, visualize, and process SAPFLUXNET data – is available from CRAN.
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Paine, C. E. T., Amissah, L., Auge, H., Baraloto, C., Baruffol, M., Bourland, N., et al. (2015). Globally, functional traits are weak predictors of juvenile tree growth, and we do not know why. Journal of Ecology, 103(4), 978–989.
Abstract: Plant functional traits, in particular specific leaf area (SLA), wood density and seed mass, are often good predictors of individual tree growth rates within communities. Individuals and species with high SLA, low wood density and small seeds tend to have faster growth rates. If community-level relationships between traits and growth have general predictive value, then similar relationships should also be observed in analyses that integrate across taxa, biogeographic regions and environments. Such global consistency would imply that traits could serve as valuable proxies for the complex suite of factors that determine growth rate, and, therefore, could underpin a new generation of robust dynamic vegetation models. Alternatively, growth rates may depend more strongly on the local environment or growth-trait relationships may vary along environmental gradients. We tested these alternative hypotheses using data on 27 352 juvenile trees, representing 278 species from 27 sites on all forested continents, and extensive functional trait data, 38% of which were obtained at the same sites at which growth was assessed. Data on potential evapotranspiration (PET), which summarizes the joint ecological effects of temperature and precipitation, were obtained from a global data base. We estimated size-standardized relative height growth rates (SGR) for all species, then related them to functional traits and PET using mixed-effect models for the fastest growing species and for all species together. Both the mean and 95th percentile SGR were more strongly associated with functional traits than with PET. PET was unrelated to SGR at the global scale. SGR increased with increasing SLA and decreased with increasing wood density and seed mass, but these traits explained only 3.1% of the variation in SGR. SGR-trait relationships were consistently weak across families and biogeographic zones, and over a range of tree statures. Thus, the most widely studied functional traits in plant ecology were poor predictors of tree growth over large scales. Synthesis. We conclude that these functional traits alone may be unsuitable for predicting growth of trees over broad scales. Determining the functional traits that predict vital rates under specific environmental conditions may generate more insight than a monolithic global relationship can offer. The most widely studied functional traits in plant ecology, specific leaf area, wood density and seed mass, were only weakly associated with tree growth rates over broad scales. Assessing trait-growth relationships under specific environmental conditions may generate more insight than a global relationship can offer. © 2015 British Ecological Society.
Keywords: Functional ecology; FunDivEurope; Growth; Hierarchical models; Plant population and community dynamics; Relative growth rate; Size-standardized growth rate; TreeDivNet
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