Reconstructing the Origin of Helianthus deserticola: Survival and Selection on the Desert Floor

Gross,; Kane,; Lexer,; Ludwig, None; Rosenthal,; Donovan,; Rieseberg,

doi:10.2307/3473435

Cited by 39 publications

(82 citation statements)

References 27 publications

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“…This requirement does appear to be met in Helianthus. All pollen and seed fertility estimates for F 1 's between the hybrid species and their parents fall below 11%, and we have previously documented the occurrence of strong ecological selection in the habitats of all three hybrid species (Lexer et al 2003a,b;Gross et al 2004;Ludwig et al 2004).…”

Section: Discussionmentioning

confidence: 99%

“…All five taxa occur in very different habitats and reciprocal transplant experiments demonstrate adaptive ecological divergence (Lexer et al 2003b;Gross et al 2004;Ludwig et al 2004). Previous mapping studies (Rieseberg et al 1995;Burke et al 2004) indicate that the genomes of H. annuus, H. anomalus, and H. petiolaris are extensively rearranged and pollen viability of F 1 hybrids from all three cross-combinations is ,5% (Rieseberg 2000).…”

Section: Methodsmentioning

confidence: 99%

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Extensive Chromosomal Repatterning and the Evolution of Sterility Barriers in Hybrid Sunflower Species

et al. 2005

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New species may arise via hybridization and without a change in ploidy. This process, termed homoploid hybrid speciation, is theoretically difficult because it requires the development of reproductive barriers in sympatry or parapatry. Theory suggests that isolation may arise through rapid karyotypic evolution and/or ecological divergence of hybrid neospecies. Here, we investigate the role of karyotypic change in homoploid hybrid speciation by generating detailed genetic linkage maps for three hybrid sunflower species, Helianthus anomalus, H. deserticola, and H. paradoxus, and comparing these maps to those previously generated for the parental species, H. annuus and H. petiolaris. We also conduct a quantitative trait locus (QTL) analysis of pollen fertility in a BC 2 population between the parental species and assess levels of pollen and seed fertility in all cross-combinations of the hybrid and parental species. The three hybrid species are massively divergent from their parental species in karyotype; gene order differences were observed for between 9 and 11 linkage groups (of 17 total), depending on the comparison. About one-third of the karyoypic differences arose through the sorting of chromosomal rearrangements that differentiate the parental species, but the remainder appear to have arisen de novo (six breakages/six fusions in H. anomalus, four breakages/three fusions in H. deserticola, and five breakages/five fusions in H. paradoxus). QTL analyses indicate that the karyotypic differences contribute to reproductive isolation. Nine of 11 pollen viability QTL occur on rearranged chromosomes and all but one map close to a rearrangement breakpoint. Finally, pollen and seed fertility estimates for F 1 's between the hybrid and parental species fall below 11%, which is sufficient for evolutionary independence of the hybrid neospecies.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Extensive Chromosomal Repatterning and the Evolution of Sterility Barriers in Hybrid Sunflower Species

et al. 2005

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“…Helianthus anomalus persists throughout the summer growing season and reproduces in late summer and fall, which is an unusual strategy for a desert summer annual. In contrast, H. deserticola is endemic to the lower water availability offdune habitat and appears to follow a more traditional desert annual strategy, flowering significantly earlier and completing its life cycle before soil moisture limitations become extreme (Rosenthal et al 2002;Gross et al 2004). The differences in flowering phenology between the H. anomalus and H. deserticola habitats may reflect differing adaptive strategies in light of the seasonal difference in soil and plant water status.…”

Section: Consequences For Plant Strategiesmentioning

confidence: 99%

Plant Responses to an Edaphic Gradient across an Active Sand Dune/Desert Boundary in the Great Basin Desert

Rosenthal

Ludwig

Donovan

2005

International Journal of Plant Sciences

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In arid ecosystems, variation in precipitation causes broad-scale spatial heterogeneity in soil moisture, but differences in soil texture, development, and plant cover can also create substantial local soil moisture heterogeneity. The boundary between inland desert sand dunes and adjacent desert habitats exhibits abrupt changes in soil and vegetation characteristics that may be associated with differences in plant-available water and nutrients. We hypothesized that differences in plant water status between habitats would mirror changes in soil texture and vegetation cover. Because the dunes have higher water availability, we predicted that plants on dunes would have higher plant water potential (C) and be less water use efficient than plants off dunes. We tested these predictions for three species-Psoralidium lanceolatum (a C 3 perennial N-fixing subshrub), Stipa hymenoides (a C 3 perennial bunchgrass), and Salsola iberica (a C 4 annual)-on actively moving desert dunes and adjacent stabilized dunes at Little Sahara Dunes, Utah. Plants on the dunes maintained higher predawn (C pd ) water potentials (>ÿ1.5 MPa) throughout the summer season, whereas off-dune plants were water stressed from July on (C pd < ÿ1:5 MPa). Midday water potential (C md ) generally mirrored C pd . As predicted, off-dune plants were more water use efficient, on the basis of leaf carbon isotope ratios (d 13 C) for the C 3 species. The observed differences in soil particle size, soil water content, and the concomitant effect on soil C likely explain the observed differences in C pd . Soil N was significantly lower on dunes, while soil P was similar across habitats. In contrast, leaf N was similar across habitats, but leaf P was significantly higher on dunes, possibly because of species-specific differences in nutrient relations or differences in habitat nutrient availability. Abrupt changes in water and nutrient availability associated with soil texture are likely to be important selective forces shaping plants' strategies in this and other desert boundary communities.

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“…Despite the long history of hybridization, the two species remain morphologically (Rosenthal et al 2002, karyotypically (Burke et al 2004;Lai et al 2005b), and ecologically distinct (Gross et al 2004). H. annuus is the larger and more robust of the two species and predominates in the more mesic soils of the eastern Great Plains, while H. petiolaris is more frequent in the drier, sandier soils of the western Great Plains and intermountain regions (Figure 1).…”

mentioning

confidence: 99%

Rampant Gene Exchange Across a Strong Reproductive Barrier Between the Annual Sunflowers,Helianthus annuusandH. petiolaris

et al. 2007

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Plant species may remain morphologically distinct despite gene exchange with congeners, yet little is known about the genomewide pattern of introgression among species. Here we analyze the effects of persistent gene flow on genomic differentiation between the sympatric sunflower species Helianthus annuus and H. petiolaris. While the species are strongly isolated in testcrosses, genetic distances at 108 microsatellite loci and 14 sequenced genes are highly variable and much lower (on average) than for more closely related but historically allopatric congeners. Our analyses failed to detect a positive association between levels of genetic differentiation and chromosomal rearrangements (as reported in a prior publication) or proximity to QTL for morphological differences or hybrid sterility. However, a significant increase in differentiation was observed for markers within 5 cM of chromosomal breakpoints. Together, these results suggest that islands of differentiation between these two species are small, except in areas of low recombination. Furthermore, only microsatellites associated with ESTs were identified as outlier loci in tests for selection, which might indicate that the ESTs themselves are the targets of selection rather than linked genes (or that coding regions are not randomly distributed). In general, these results indicate that even strong and genetically complex reproductive barriers cannot prevent widespread introgression.

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Reconstructing the Origin of Helianthus deserticola: Survival and Selection on the Desert Floor

Cited by 39 publications

References 27 publications

Extensive Chromosomal Repatterning and the Evolution of Sterility Barriers in Hybrid Sunflower Species

Extensive Chromosomal Repatterning and the Evolution of Sterility Barriers in Hybrid Sunflower Species

Plant Responses to an Edaphic Gradient across an Active Sand Dune/Desert Boundary in the Great Basin Desert

Rampant Gene Exchange Across a Strong Reproductive Barrier Between the Annual Sunflowers,Helianthus annuusandH. petiolaris

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