Species tree estimation of diploid <i>Helianthus</i> (Asteraceae) using target enrichment

Stephens, Jessica D.; Rogers, Willie L.; Mason, Chase M.; Donovan, Lisa A.; Malmberg, Russell L.

doi:10.3732/ajb.1500031

Cited by 63 publications

(106 citation statements)

References 69 publications

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“…The annual sunflower species tree revealed by the SNP data agreed with previously published taxonomic reports for the system (Timme et al ., ; Moody & Rieseberg, ; Stephens et al ., ; Fig. ).…”

Section: Resultsmentioning

confidence: 93%

“…Annual sunflowers in the genus Helianthus are an excellent system with which to address questions about cytonuclear discordance for a number of reasons. Previous studies have noted cytonuclear discordance in parts of the range of this group (Rieseberg et al ., ,b; Dorado et al ., ; Stephens et al ., ). Recent divergence and large population sizes (Sambatti et al ., ) make incomplete lineage sorting a viable explanation for this discordance.…”

Section: Introductionmentioning

confidence: 97%

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An evaluation of alternative explanations for widespread cytonuclear discordance in annual sunflowers (Helianthus)

et al. 2018

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Cytonuclear discordance is commonly observed in phylogenetic studies, yet few studies have tested whether these patterns reflect incomplete lineage sorting or organellar introgression. Here, we used whole-chloroplast sequence data in combination with over 1000 nuclear single-nucleotide polymorphisms to clarify the extent of cytonuclear discordance in wild annual sunflowers (Helianthus), and to test alternative explanations for such discordance. Our phylogenetic analyses indicate that cytonuclear discordance is widespread within this group, both in terms of the relationships among species and among individuals within species. Simulations of chloroplast evolution show that incomplete lineage sorting cannot explain these patterns in most cases. Instead, most of the observed discordance is better explained by cytoplasmic introgression. Molecular tests of evolution further indicate that selection may have played a role in driving patterns of plastid variation - although additional experimental work is needed to fully evaluate the importance of selection on organellar variants in different parts of the geographic range. Overall, this study represents one of the most comprehensive tests of the drivers of cytonuclear discordance and highlights the potential for gene flow to lead to extensive organellar introgression in hybridizing taxa.

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Section: Resultsmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 97%

An evaluation of alternative explanations for widespread cytonuclear discordance in annual sunflowers (Helianthus)

et al. 2018

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“…(a) Principal components analysis shows continuous variation among species across multivariate trait space (left), as well as a lack of prominent axes of variation across leaf‐level defenses and the HeliaMet metrics of average number of compounds and HeliaMet subset PC 1 (right). (b) Comparison of phylogentic relationships (left, Stephens et al ., ) with dendrogram of defense trait similarity using Ward's clustering algorithm on standardized data (right). Similarity profiling ( SIMPROF ) yields no significant clustering of species (π = 2.55; P = 0.432).…”

Section: Resultsmentioning

confidence: 99%

Macroevolution of leaf defenses and secondary metabolites across the genus Helianthus

et al. 2015

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SummaryLeaf defenses are widely recognized as key adaptations and drivers of plant evolution. Across environmentally diverse habitats, the macroevolution of leaf defenses can be predicted by the univariate trade-off model, which predicts that defenses are functionally redundant and thus trade off, and the resource availability hypothesis, which predicts that defense investment is determined by inherent growth rate and that higher defense will evolve in lower resource environments.Here, we examined the evolution of leaf physical and chemical defenses and secondary metabolites in relation to environmental characteristics and leaf economic strategy across 28 species of Helianthus (the sunflowers).Using a phylogenetic comparative approach, we found few evolutionary trade-offs among defenses and no evidence for defense syndromes. We also found that leaf defenses are strongly related to leaf economic strategy, with higher defense in more resource-conservative species, although there is little support for the evolution of higher defense in low-resource habitats.A wide variety of physical and chemical defenses predict resistance to different insect herbivores, fungal pathogens, and a parasitic plant, suggesting that most sunflower defenses are not redundant in function and that wild Helianthus represents a rich source of variation for the improvement of crop sunflower.

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“…Phoebanthus tenuifolius seeds were also collected for inclusion in the study as an outgroup for Helianthus (Mason and Donovan ; Stephens et al. ). Of the 58 populations collected in total, 48 were directly collected from wild populations, while 10 were obtained from USDA accessions (nine of which were also directly collected from wild populations; i.e., they had not yet been regrown to maintain seed stocks).…”

Section: Methodsmentioning

confidence: 99%

Fine root tradeoffs between nitrogen concentration and xylem vessel traits preclude unified whole‐plant resource strategies in Helianthus

Bowsher

Mason

Goolsby

et al. 2016

Ecology and Evolution

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Recent work suggests variation in plant growth strategies is governed by a tradeoff in resource acquisition and use, ranging from a rapid resource acquisition strategy to a resource‐conservative strategy. While evidence for this tradeoff has been found in leaves, knowledge of root trait strategies, and whether they reflect adaptive differentiation across environments, is limited. In the greenhouse, we investigated variation in fine root morphology (specific root length and tissue density), chemistry (nitrogen concentration and carbon:nitrogen), and anatomy (root cross‐sectional traits) in populations of 26 Helianthus species and sister Phoebanthus tenuifolius. We also compared root trait variation in this study with leaf trait variation previously reported in a parallel study of these populations. Root traits varied widely and exhibited little phylogenetic signal, suggesting high evolutionary lability. Specific root length and root tissue density were weakly negatively correlated, but neither was associated with root nitrogen, providing little support for a single axis of root trait covariation. Correlations between traits measured in the greenhouse and native site characteristics were generally weak, suggesting a variety of equally viable root trait combinations exist within and across environments. However, high root nitrogen was associated with lower xylem vessel number and cross‐sectional area, suggesting a tradeoff between nutrient investment and water transport capacity. This led to correlations between root and leaf traits that were not always consistent with an acquisition–conservation tradeoff at the whole‐plant level. Given that roots must balance acquisition of water and nutrients with functions like anchorage, exudation, and microbial symbioses, the varied evidence for root trait covariation likely reflects the complexity of interacting selection pressures belowground. Similarly, the lack of evidence for a single acquisition–conservation tradeoff at the whole‐plant level likely reflects the vastly different selection pressures shaping roots and leaves, and the resources they are optimized to obtain.

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Species tree estimation of diploid Helianthus (Asteraceae) using target enrichment

Cited by 63 publications

References 69 publications

An evaluation of alternative explanations for widespread cytonuclear discordance in annual sunflowers (Helianthus)

An evaluation of alternative explanations for widespread cytonuclear discordance in annual sunflowers (Helianthus)

Macroevolution of leaf defenses and secondary metabolites across the genus Helianthus

Fine root tradeoffs between nitrogen concentration and xylem vessel traits preclude unified whole‐plant resource strategies in Helianthus

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