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1.
Proc Natl Acad Sci U S A ; 111(42): 15149-54, 2014 Oct 21.
Artigo em Inglês | MEDLINE | ID: mdl-25288748

RESUMO

The role of polyploidy, particularly allopolyploidy, in plant diversification is a subject of debate. Whole-genome duplications precede the origins of many major clades (e.g., angiosperms, Brassicaceae, Poaceae), suggesting that polyploidy drives diversification. However, theoretical arguments and empirical studies suggest that polyploid lineages may actually have lower speciation rates and higher extinction rates than diploid lineages. We focus here on the grass tribe Andropogoneae, an economically and ecologically important group of C4 species with a high frequency of polyploids. A phylogeny was constructed for ca. 10% of the species of the clade, based on sequences of four concatenated low-copy nuclear loci. Genetic allopolyploidy was documented using the characteristic pattern of double-labeled gene trees. At least 32% of the species sampled are the result of genetic allopolyploidy and result from 28 distinct tetraploidy events plus an additional six hexaploidy events. This number is a minimum, and the actual frequency could be considerably higher. The parental genomes of most Andropogoneae polyploids diverged in the Late Miocene coincident with the expansion of the major C4 grasslands that dominate the earth today. The well-documented whole-genome duplication in Zea mays ssp. mays occurred after the divergence of Zea and Sorghum. We find no evidence that polyploidization is followed by an increase in net diversification rate; nonetheless, allopolyploidy itself is a major mode of speciation.


Assuntos
Diploide , Especiação Genética , Pradaria , Poliploidia , Teorema de Bayes , Evolução Biológica , Biologia Computacional , Genes de Plantas , Genoma , Genômica , Funções Verossimilhança , Filogenia , Poaceae , Análise de Sequência de DNA
2.
Am J Bot ; 99(11): e443-6, 2012 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-23108465

RESUMO

PREMISE OF THE STUDY: Polyploidy is common in the grasses and low-copy nuclear loci are needed to further our understanding of phylogenetic relationships. METHODS AND RESULTS: Genetic and genomic resources were combined to identify loci known to influence plant and inflorescence architecture. Degenerate primers were designed and tested to amplify regions of 11 nuclear-encoded loci across the panicoid grasses. CONCLUSIONS: The primers designed in this study amplify regions of a diverse set of genes within the panicoid grasses. Properly employed, these markers will allow the identification of allopolyploid taxa and their diploid progenitors.


Assuntos
Núcleo Celular/genética , Genes de Plantas/genética , Filogenia , Poaceae/genética , Primers do DNA/genética , DNA de Plantas/química , DNA de Plantas/genética , Variação Genética , Dados de Sequência Molecular , Poaceae/classificação , Reação em Cadeia da Polimerase , Análise de Sequência de DNA , Especificidade da Espécie
3.
Science ; 360(6391)2018 05 25.
Artigo em Inglês | MEDLINE | ID: mdl-29798853

RESUMO

Hülsmann and Hartig suggest that ecological mechanisms other than specialized natural enemies or intraspecific competition contribute to our estimates of conspecific negative density dependence (CNDD). To address their concern, we show that our results are not the result of a methodological artifact and present a null-model analysis that demonstrates that our original findings-(i) stronger CNDD at tropical relative to temperate latitudes and (ii) a latitudinal shift in the relationship between CNDD and species abundance-persist even after controlling for other processes that might influence spatial relationships between adults and recruits.


Assuntos
Biodiversidade , Árvores , Densidade Demográfica , Plântula
4.
Science ; 360(6391)2018 05 25.
Artigo em Inglês | MEDLINE | ID: mdl-29798855

RESUMO

Chisholm and Fung claim that our method of estimating conspecific negative density dependence (CNDD) in recruitment is systematically biased, and present an alternative method that shows no latitudinal pattern in CNDD. We demonstrate that their approach produces strongly biased estimates of CNDD, explaining why they do not detect a latitudinal pattern. We also address their methodological concerns using an alternative distance-weighted approach, which supports our original findings of a latitudinal gradient in CNDD and a latitudinal shift in the relationship between CNDD and species abundance.


Assuntos
Biodiversidade , Árvores , Ecossistema , Plântula
5.
Science ; 356(6345): 1389-1392, 2017 06 30.
Artigo em Inglês | MEDLINE | ID: mdl-28663501

RESUMO

Theory predicts that higher biodiversity in the tropics is maintained by specialized interactions among plants and their natural enemies that result in conspecific negative density dependence (CNDD). By using more than 3000 species and nearly 2.4 million trees across 24 forest plots worldwide, we show that global patterns in tree species diversity reflect not only stronger CNDD at tropical versus temperate latitudes but also a latitudinal shift in the relationship between CNDD and species abundance. CNDD was stronger for rare species at tropical versus temperate latitudes, potentially causing the persistence of greater numbers of rare species in the tropics. Our study reveals fundamental differences in the nature of local-scale biotic interactions that contribute to the maintenance of species diversity across temperate and tropical communities.


Assuntos
Biodiversidade , Árvores/classificação , Antibiose , Ecossistema , Florestas , Geografia , Modelos Biológicos , Árvores/fisiologia , Clima Tropical
6.
J Ecol ; 104(2): 497-506, 2016 03.
Artigo em Inglês | MEDLINE | ID: mdl-27609991

RESUMO

Understanding the resilience of moist tropical forests to treefall disturbance events is important for understanding the mechanisms that underlie species coexistence and for predicting the future composition of these ecosystems. Here, we test whether variation in the functional composition of Amazonian forests determines their resilience to disturbance.We studied the legacy of natural treefall disturbance events in four forests across Amazonia that differ substantially in functional composition. We compared the composition and diversity of all free-standing woody stems 2-10 cm diameter in previously disturbed and undisturbed 20 × 20 m subplots within 55, one-hectare, long-term forest inventory plots.Overall, stem number increased following disturbance, and species and functional composition shifted to favour light-wooded, small-seeded taxa. Alpha-diversity increased, but beta-diversity was unaffected by disturbance, in all four forests.Changes in response to disturbance in both functional composition and alpha-diversity were, however, small (2 - 4% depending on the parameter) and similar among forests. Synthesis. This study demonstrates that variation in the functional composition of Amazonian forests does not lead to large differences in the response of these forests to treefall disturbances, and overall, these events have a minor role in maintaining the diversity of these ecosystems.

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