The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
John R Pannell - One of the best experts on this subject based on the ideXlab platform.
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small scale and regional spatial dynamics of an Annual Plant with contrasting sexual systems
Journal of Ecology, 2017Co-Authors: Marcel E Dorken, Robert P Freckleton, John R PannellAbstract:1. Plant demography is known to depend on both spatial dynamics and life history, but how these two factors interact is poorly understood. We conducted a longitudinal study of the wind-pollinated Annual Plant Mercurialis annua that varies geographically in its sexual system to investigate this interaction. 2. Metapopulation demographic models predict that regular population turnover should be a more common feature of monomorphic than dimorphic populations because males and females cannot found new populations by selfing but hermaphrodites can. We tested the prediction that rates of population turnover would be higher in monomorphic compared to dimorphic regions. 3. We surveyed 356 populations of M. annua along five regional transects in Morocco and the Iberian Peninsula over a 3-year period to examine their demography and persistence. Each transect crossed a transition in the sexual system, from a monomorphic region where almost all populations were hermaphroditic to a dimorphic one in which most populations had separate sexes (males with females or hermaphrodites). 4. As predicted, rates of local apparent extinctions (i.e., the disappearance of adult Plants) were nearly 50% higher in monomorphic compared to dimorphic regions. Local extinctions appeared to be driven by changes in vegetation cover, with extinctions tending to occur in sites in which perennial cover also declined. This suggests that disturbance is a primary agent of local extinctions. 5. We further examined the influence of regional dynamics on local demographic properties by investigating patterns of spatial autocorrelation in population density across years. We found positive spatial autocorrelations in Plant densities within regions for both sexual systems. However, these positive autocorrelations extended over shorter distances in monomorphic regions, perhaps as a result of greater population flux in these regions. 6. Synthesis. Our study shows that population dynamics may be influenced by processes acting at a range of spatial scales: within patches, across patches within sites, and across sites within regions, as well as by life-history variation. In Mercurialis annua, regional variation in apparent extinction rates is affected by life history and implicated in regulating the geographical distribution of populations with different sexual systems.
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sexual systems and measures of occupancy and abundance in an Annual Plant testing the metapopulation model
The American Naturalist, 2007Co-Authors: Sarah M Eppley, John R PannellAbstract:Abstract: The need for reproductive assurance during dispersal, along with the pressure of local mate competition, means that the importance of frequent or repeated colonization is implicit in the sexual‐system evolution literature. However, to date there have been few empirical tests of the association between colonization and the sexual system in Plants. Here we provide such a test by comparing occupancy and abundance of populations of the European Plant Mercurialis annua across regions characterized by different sexual systems. Specifically, we predicted that monomorphic, hermaphroditic populations, which are thought to have evolved under selection for reproductive assurance during repeated bouts of colonization, would be smaller and their suitable habitat less frequently occupied than dimorphic populations, where males co‐occur with either females or hermaphrodites. We show that both of these predictions are upheld. We evaluate our results against competing hypotheses for the occupancy‐abundance relat...
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sexual systems and population genetic structure in an Annual Plant testing the metapopulation model
The American Naturalist, 2006Co-Authors: Darren J Obbard, Stephen A Harris, John R PannellAbstract:Abstract: The need for reproductive assurance during dispersal, along with the pressure of local mate competition, means that the importance of frequent or repeated colonization is implicit in the literature on sexual system evolution. However, there have been few empirical tests of the association between colonization history and sexual system in Plants, and none within a single species. Here we use patterns of genetic diversity to provide such a test in the Mercurialis annua species complex, which spans the range of systems from self‐compatible monoecy through androdioecy to dioecy. This variation has been hypothesized to result from differing patterns of metapopulation turnover and recolonization. Because monoecy should be favored during colonization, androdioecy and dioecy will be maintained only in regions with low rates of local extinction and recolonization, and these differences should also be reflected in patterns of neutral genetic diversity. We show that monoecious populations of M. annua displ...
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Sexual Systems and Population Genetic Structure in an Annual Plant: Testing the Metapopulation Model
The American naturalist, 2006Co-Authors: Darren J Obbard, Stephen Harris, John R PannellAbstract:The need for reproductive assurance during dispersal, along with the pressure of local mate competition, means that the importance of frequent or repeated colonization is implicit in the literature on sexual system evolution. However, there have been few empirical tests of the association between colonization history and sexual system in Plants, and none within a single species. Here we use patterns of genetic diversity to provide such a test in the Mercurialis annua species complex, which spans the range of systems from self-compatible monoecy through androdioecy to dioecy. This variation has been hypothesized to result from differing patterns of metapopulation turnover and recolonization. Because monoecy should be favored during colonization, androdioecy and dioecy will be maintained only in regions with low rates of local extinction and recolonization, and these differences should also be reflected in patterns of neutral genetic diversity. We show that monoecious populations of M. annua display lower within-population genetic diversity than androdioecious populations and higher genetic differentiation than dioecious and androdioecious populations, as predicted by metapopulation models. In contrast, regional diversity in M. annua appears to be primarily a product of postglacial range expansion from two refugia in the eastern and western Mediterranean Basin.
John M Dwyer - One of the best experts on this subject based on the ideXlab platform.
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warmer seed environments increase germination fractions in australian winter Annual Plant species
Ecosphere, 2016Co-Authors: John M Dwyer, Todd E EricksonAbstract:Climate can influence Plant demographic processes and life stages in different ways, but such details are often ignored in analyses that focus on adult life stages and Annual climate averages. In particular, the effects of climate on seeds may be hugely important under climate change. Climate is known to influence seed survival and germination, which in turn can strongly affect population persistence and community dynamics. We investigated climate and other environmental effects on seed viability and germination probabilities of six winter Annual Plant species persisting in small, isolated habitat fragments in the Mediterranean-climate region of southwestern Australia. Seeds were collected from southern (cool) and northern (warm) bushland remnants and factorially placed into each location to assess the effects of natural dormancy alleviation via after-ripening. Seeds were then exposed to cool and warm germination treatments (representing average germination conditions in the two remnants). For five of the six species, seeds from warm maternal populations had higher germination probabilities (or germinated more seeds sooner). Regardless of maternal population, germination probabilities were higher (or germination was more rapid) for seeds that were after-ripened in the warm remnant for almost all species. For all species, germination was higher (or more rapid) under the warmer germination temperatures. We also found strong microsite effects on seed viability for some species. In the absence of adaptation in dormancy regulation and germination physiology, our results indicate that most of the winter Annual species studied will germinate higher fractions of seeds under future climate conditions due to the cumulative effects of warmer maternal, after-ripening, and germination environments. The fate of isolated populations under climate change may therefore depend strongly on postgermination survival and reproduction to prevent seed bank depletion.
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climate moderates release from nutrient limitation in natural Annual Plant communities
Global Ecology and Biogeography, 2015Co-Authors: John M Dwyer, Richard J Hobbs, Claire E Wainwright, Margaret M MayfieldAbstract:AimTo assess the combined influences of nutrient enrichment, invasive species and climate on assembly processes in natural Annual Plant communities.
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distinct invasion strategies operating within a natural Annual Plant system
Ecology Letters, 2015Co-Authors: Hao Ran Lai, John M Dwyer, Margaret M Mayfield, Justine Gaydescombes, Thomas SpiegelbergerAbstract:Alien Plant species are known to have a wide range of impacts on recipient communities, from resident species’ exclusions to coexistence with resident species. It remains unclear; however, if this variety of impacts is due to different invader strategies, features of recipient communities or both. To test this, we examined multiple Plant invasions of a single ecosystem in southwestern Australia. We used extensive community data to calculate pairwise segregation between target alien species and many co-occurring species. We related segregation to species’ positions along community trait hierarchies and identified at least two distinct invasion strategies: ‘exploiters’ which occupy high positions along key trait hierarchies and reduce local native species diversity (particularly in nutrient-enriched situations), and ‘coexisters’ who occupy intermediate trait positions and have no discernable impact on native diversity. We conclude that trait hierarchies, linked to measures of competition, can provide valuable insights about the processes driving different invasion outcomes.
Todd E Erickson - One of the best experts on this subject based on the ideXlab platform.
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warmer seed environments increase germination fractions in australian winter Annual Plant species
Ecosphere, 2016Co-Authors: John M Dwyer, Todd E EricksonAbstract:Climate can influence Plant demographic processes and life stages in different ways, but such details are often ignored in analyses that focus on adult life stages and Annual climate averages. In particular, the effects of climate on seeds may be hugely important under climate change. Climate is known to influence seed survival and germination, which in turn can strongly affect population persistence and community dynamics. We investigated climate and other environmental effects on seed viability and germination probabilities of six winter Annual Plant species persisting in small, isolated habitat fragments in the Mediterranean-climate region of southwestern Australia. Seeds were collected from southern (cool) and northern (warm) bushland remnants and factorially placed into each location to assess the effects of natural dormancy alleviation via after-ripening. Seeds were then exposed to cool and warm germination treatments (representing average germination conditions in the two remnants). For five of the six species, seeds from warm maternal populations had higher germination probabilities (or germinated more seeds sooner). Regardless of maternal population, germination probabilities were higher (or germination was more rapid) for seeds that were after-ripened in the warm remnant for almost all species. For all species, germination was higher (or more rapid) under the warmer germination temperatures. We also found strong microsite effects on seed viability for some species. In the absence of adaptation in dormancy regulation and germination physiology, our results indicate that most of the winter Annual species studied will germinate higher fractions of seeds under future climate conditions due to the cumulative effects of warmer maternal, after-ripening, and germination environments. The fate of isolated populations under climate change may therefore depend strongly on postgermination survival and reproduction to prevent seed bank depletion.
Fabrice Roux - One of the best experts on this subject based on the ideXlab platform.
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cytonuclear interactions affect adaptive traits of the Annual Plant arabidopsis thaliana in the field
Proceedings of the National Academy of Sciences of the United States of America, 2016Co-Authors: Fabrice Roux, Romain Villoutreix, Tristan Maryhuard, Elise Barillot, Estelle Wenes, Lucy Botran, Stephanie Durand, Marielaure Martinmagniette, Christine Camilleri, Francoise BudarAbstract:Although the contribution of cytonuclear interactions to Plant fitness variation is relatively well documented at the interspecific level, the prevalence of cytonuclear interactions at the intraspecific level remains poorly investigated. In this study, we set up a field experiment to explore the range of effects that cytonuclear interactions have on fitness-related traits in Arabidopsis thaliana. To do so, we created a unique series of 56 cytolines resulting from cytoplasmic substitutions among eight natural accessions reflecting within-species genetic diversity. An assessment of these cytolines and their parental lines scored for 28 adaptive whole-organism phenotypes showed that a large proportion of phenotypic traits (23 of 28) were affected by cytonuclear interactions. The effects of these interactions varied from slight but frequent across cytolines to strong in some specific parental pairs. Two parental pairs accounted for half of the significant pairwise interactions. In one parental pair, Ct-1/Sha, we observed symmetrical phenotypic responses between the two nuclear backgrounds when combined with specific cytoplasms, suggesting nuclear differentiation at loci involved in cytonuclear epistasis. In contrast, asymmetrical phenotypic responses were observed in another parental pair, Cvi-0/Sha. In the Cvi-0 nuclear background, fecundity and phenology-related traits were strongly affected by the Sha cytoplasm, leading to a modified reproductive strategy without penalizing total seed production. These results indicate that natural variation in cytoplasmic and nuclear genomes interact to shape integrative traits that contribute to adaptation, thereby suggesting that cytonuclear interactions can play a major role in the evolutionary dynamics of A. thaliana.
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the genetics of intra and interspecific competitive response and effect in a local population of an Annual Plant species
Functional Ecology, 2015Co-Authors: Etienne Baron, Julien Richirt, Romain Villoutreix, Laurent Amsellem, Fabrice RouxAbstract:Summary While competition is recognized as a major factor responsible for Plant community dynamics, the genetics of intra- and interspecific competitive ability of a target species (i.e. level of intra-population genetic variation, identity of phenotypic traits under selection and genetic bases) still deserves a deeper investigation at the local spatial scale by considering both numerous genotypes and several interacting species. In this study, we tested whether the genetics of competitive response and effect in Arabidopsis thaliana was dependent on the competitive environment at both the intraspecific and interspecific levels. We used a mapping population of 48 accessions (i) that maximize the genetic diversity of a local population of A. thaliana and (ii) that have been genotyped for 168 503 single nucleotide polymorphisms. In a common garden experiment, those 48 accessions were grown in six competitive environments: the absence of competition, intraspecific competition and interspecific competition with four species frequently associated with A. thaliana in natural Plant communities (i.e. Poa annua, Stellaria media, Trifolium repens and Veronica arvensis). A suite of nine phenotypic traits, including a proxy of fitness, were scored on each target A. thaliana Plant and the above-ground dry biomass of its corresponding competitor was estimated. We first showed that crossing reaction norms of competitive response (A. thaliana performance) and effect (competitor biomass) might promote maintenance of genetic variation in a local population of A. thaliana and species coexistence at a fine spatial scale. By estimating genotypic gradients of selection, we then demonstrated that the optimal phenotypic strategies in response to competition depend on the identity of the competitor species. Finally, a genomewide association mapping approach highlighted that genomic regions associated with direct genetic effects were (i) dependent on the competitor species and (ii) different from genomic regions associated with interspecific indirect genetic effects. While a first step, this study highlighted the power of adding ecology to genomics in A. thaliana to identify genetic bases underlying micro-geographic adaptation to competition. Next-generation sequencing technologies will undoubtedly facilitate the discovery of molecular and genetic mechanisms underlying competitive ability in other Plant species, and thereby the prediction of evolutionary trajectories of Plant communities.
Amanda L. File - One of the best experts on this subject based on the ideXlab platform.
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Kin recognition in an Annual Plant
Biology Letters, 2007Co-Authors: Susan A. Dudley, Amanda L. FileAbstract:Kin recognition is important in animal social systems. However, though Plants often compete with kin, there has been as yet no direct evidence that Plants recognize kin in competitive interactions. Here we show in the Annual Plant Cakile edentula, allocation to roots increased when groups of strangers shared a common pot, but not when groups of siblings shared a pot. Our results demonstrate that Plants can discriminate kin in competitive interactions and indicate that the root interactions may provide the cue for kin recognition. Because greater root allocation is argued to increase below-ground competitive ability, the results are consistent with kin selection.