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At least 19 recordsLinked to original sources

PubMed2006

Regeneration of interspecific somatic hybrids between Helianthus annuus L. and Helianthus maximiliani (Schrader) via protoplast electrofusion.

Helianthus maximiliani is one of the wild Helianthus species with the genes for resistance to many pathogens including Sclerotinia sclerotiorum. Unfortunately, a transfer of disease resistance genes from this species into the cultivated sunflower is limited by its poor crossability with the cultivated sunflower and sterility of interspecific hybrids. To overcome this problem, mesophyll protoplasts of Sclerotinia sclerotiorum-resistant clone of H. maximiliani were electrically fused with etiolated hypocotyl protoplasts of the cultivated sunflower inbred line PH-BC1-91A. Fusion products were embedded in agarose droplets and subjected to different regeneration protocols. Developed microcalluses were released from the agarose and transferred into solid media. Shoot regeneration was achieved by culture of calluses on regeneration medium containing 2.2 mg l(-1) BAP and 0.01 mg l(-1) NAA after the treatment with a high concentration of 2,4 D for a limited period of time. A morphological and RAPD analysis confirmed a hybrid nature of the regenerated plants.

Cell Fusion↗

PubMed1990

Helianthus annuus ssp. texanus has chloroplast DNA and nuclear ribosomal RNA genes of Helianthus debilis ssp. cucumerifolius.

Heiser [Heiser, C. B. (1951) Evolution 5, 42-51] hypothesized that Helianthus annuus ssp. texanus was derived by the introduction of H. annuus into Texas and subsequent introgression of genes from Helianthus debilis ssp. cucumerifolius into H. annuus. Although often considered to be one of the best cases of introgression in plants, alternative hypotheses to introgression, such as convergence or the joint retention of the ancestral condition, could not be ruled out in the original study. To test for the occurrence of introgression we examined 14 populations of H. annuus ssp. texanus, 14 allopatric populations of H. annuus, and three populations of H. debilis ssp. cucumerifolius with reference to diagnostic chloroplast DNA and nuclear ribosomal DNA markers. Thirteen of the 14 populations of H. annuus ssp. texanus had chloroplast DNA and/or ribosomal DNA markers of H. debilis ssp. cucumerifolius. In contrast, no chloroplast DNA or ribosomal DNA markers of H. debilis ssp. cucumerifolius were found in the 14 allopatric populations of H. annuus. Our findings provide strong support, therefore, for the hypothesized introgressive origin of H. annuus ssp. texanus.

Journal Article↗

PubMed2005

Hybridization and genome size evolution: timing and magnitude of nuclear DNA content increases in Helianthus homoploid hybrid species.

Hybridization and polyploidy can induce rapid genomic changes, including the gain or loss of DNA, but the magnitude and timing of such changes are not well understood. The homoploid hybrid system in Helianthus (three hybrid-derived species and their two parents) provides an opportunity to examine the link between hybridization and genome size changes in a replicated fashion. Flow cytometry was used to estimate the nuclear DNA content in multiple populations of three homoploid hybrid Helianthus species (Helianthus anomalus, Helianthus deserticola, and Helianthus paradoxus), the parental species (Helianthus annuus and Helianthus petiolaris), synthetic hybrids, and natural hybrid-zone populations. Results confirm that hybrid-derived species have 50% more nuclear DNA than the parental species. Despite multiple origins, hybrid species were largely consistent in their DNA content across populations, although H. deserticola showed significant interpopulation differences. First- and sixth-generation synthetic hybrids and hybrid-zone plants did not show an increase from parental DNA content. First-generation hybrids differed in DNA content according to the maternal parent. In summary, hybridization by itself does not lead to increased nuclear DNA content in Helianthus, and the evolutionary forces responsible for the repeated increases in DNA content seen in the hybrid-derived species remain mysterious.

DNA, Plant↗

PubMed2006

Helianthus nighttime conductance and transpiration respond to soil water but not nutrient availability.

We investigated the response of Helianthus species nighttime conductance (g(night)) and transpiration (E(night)) to soil nutrient and water limitations in nine greenhouse studies. The studies primarily used wild Helianthus annuus, but also included a commercial and early domesticate of H. annuus and three additional wild species (Helianthus petiolaris Nutt., Helianthus deserticola Heiser, and Helianthus anomalus Blake). Well-watered plants of all species showed substantial g(night) (0.023-0.225 mol m(-2) s(-1)) and E(night) (0.29-2.46 mmol m(-2) s(-1)) measured as instantaneous gas exchange. Based on the potential for transpiration to increase mass flow of mobile nutrients to roots, we hypothesized that g(night) and E(night) would increase under limiting soil nutrients but found no evidence of responses in all six studies testing this. Based on known daytime responses to water limitation, we hypothesized that g(night) and E(night) would decrease when soil water availability was limited, and results from all four studies testing this supported our hypothesis. We also established that stomatal conductance at night was on average 5 times greater than cuticular conductance. Additionally, g(night) and E(night) varied nocturnally and across plant reproductive stages while remaining relatively constant as leaves aged. Our results further the ability to predict conditions under which nighttime water loss will be biologically significant and demonstrate that for Helianthus, g(night) can be regulated.

Biomass↗

PubMed2006

Distribution of Ty3-gypsy- and Ty1-copia-like DNA sequences in the genus Helianthus and other Asteraceae.

Two repeated DNA sequences, pHaS13 and pHaS211, which revealed similarity to the int gene of Ty3-gypsy retrotransposons and the RNAse-H gene of Ty1-copia retroelements, respectively, were surveyed in Asteraceae species and within the genus Helianthus. Southern analysis of the genome of selected Asteraceae that belong to different tribes showed that pHaS13- and pHaS211-related subfamilies of gypsy- and copia-like retroelements are highly redundant only in Helianthus and, to a lesser extent, in Tithonia, a Helianthus strict relative. However, under low stringency posthybridization washes, bands were observed in almost all the other Asteraceae tested when pHaS13 was used as a probe, and in several species when pHaS211 was hybridized. FISH analysis of pHaS13 or pHaS211 probes was performed in species in which labelling was observed in Southern hybridizations carried out under high stringency conditions (Helianthus annuus, Tithonia rotundifolia, Ageratum spp., Leontopodium spp., Senecio vulgaris for pHaS13, and H. annuus, Tithonia rotundifolia, and S. vulgaris for pHaS211). Scattered labelling was observed over all metaphase chromosomes, indicating a large dispersal of both Ty3-gypsy- and Ty1-copia-like retroelements. However, preferential localization of Ty3-gypsy-like sequences at centromeric chromosome regions was observed in all of the species studies but one, even in species in which pHaS13-related elements are poorly represented. Ty1-copia-like sequences showed preferential localization at the chromosome ends only in H. annuus. To study the evolution of gypsy- and copia-like retrotransposons in Helianthus, cladograms were built based on the Southern blot hybridization patterns of pHaS13 or pHaS211 sequences to DNA digests of several species of this genus. Both cladograms agree in splitting the genomes studied into annuals and perennials. Differences that occurred within the clades of perennial and annual species between gypsy- and copia-like retroelements indicated that these retrotransposons were differentially active during Helianthus speciation, suggesting that the evolution of the 2 retroelement families was, within limits, independent.

Amino Acid Sequence↗

PubMed2005

Enhanced phytoextraction: II. Effect of EDTA and citric acid on heavy metal uptake by Helianthus annuus from a calcareous soil.

High biomass producing plant species, such as Helianthus annuus, have potential for removing large amounts of trace metals by harvesting the aboveground biomass if sufficient metal concentrations in their biomass can be achieved However, the low bioavailability of heavy metals in soils and the limited translocation of heavy metals to the shoots by most high biomass producing plant species limit the efficiency of the phytoextraction process. Amendment of a contaminated soil with ethylene diamine tetraacetic acid (EDTA) or citric acid increases soluble heavy metal concentrations, potentially rendering them more available for plant uptake. This article discusses the effects of EDTA and citric acid on the uptake of heavy metals and translocation to aboveground harvestable plant parts in Helianthus annuus. EDTA was included in the research for comparison purposes in our quest for less persistent alternatives, suitable for enhanced phytoextraction. Plants were grown in a calcareous soil moderately contaminated with Cu, Pb, Zn, and Cd and treated with increasing concentrations of EDTA (0.1, 1, 3, 5, 7, and 10 mmol kg(-1) soil) or citric acid (0.01, 0.05, 0.25, 0.442, and 0.5 mol kg(-1) soil). Heavy metal concentrations in harvested shoots increased with EDTA concentration but the actual amount of phytoextracted heavy metals decreased at high EDTA concentrations, due to severe growth depression. Helianthus annuus suffered heavy metal stress due to the significantly increased bioavailable metal fraction in the soil. The rapid mineralization of citric acid and the high buffering capacity of the soil made citric acid inefficient in increasing the phytoextracted amounts of heavy metals. Treatments that did not exceed the buffering capacity of the soil (< 0.442 mol kg(-1) soil) did not result in any significant increase in shoot heavy metal concentrations. Treatments with high concentrations resulted in a dissolution of the carbonates and compaction of the soil. These physicochemical changes caused growth depression of Helianthus annuus. EDTA and citric acid added before sowing of Helianthus annuus did not appear to be efficient amendments when phytoextraction of heavy metals from calcareous soils is considered.

Biodegradation, Environmental↗

PubMed2007

Genetic architecture of leaf ecophysiological traits in Helianthus.

We investigated quantitative trait loci (QTLs) for several leaf chemistry traits in early-generation hybrids between Helianthus annuus and Helianthus petiolaris, the parental species of the ancient diploid hybrid sunflower species Helianthus anomalus, Helianthus deserticola, and Helianthus paradoxus. We grew individuals of a second-generation backcross (BC(2)) toward H. petiolaris under optimum conditions in a glass house experiment. Trait values were measured once for each individual. In addition, genotypic data previously determined for each individual were employed for composite interval mapping of QTLs. We detected QTLs for leaf carbon concentration, leaf nitrogen concentration, leaf nitrogen per unit area, and photosynthetic nitrogen use efficiency. Leaf carbon isotope discrimination (delta(13)C) and leaf nitrogen isotopic composition (delta(15)N) were analyzed, but no significant QTLs were found for these traits. Interestingly, two neighboring loci explained a relatively large percentage of the variation in leaf nitrogen per unit area. This was notable because leaf nitrogen has been shown to strongly affect the fitness of early-generation sunflower hybrids in the H. anomalus habitat, and QTLs of large effect are expected to respond relatively quickly to selection. We speculate that the genetic architecture underlying leaf nitrogen may have facilitated the colonization of active desert sand dunes by H. anomalus.

Carbon↗

PubMed1978

Effect on sphingomyelin-containing liposomes of phospholipase D from Corynebacterium ovis and the cytolysin from Stoichactis helianthus.

The toxic, sphingomyelin-specific phospholipase D (phosphatidylcholine phosphatidohydrolase EC 3.1.4.4) from Corynebacterium ovis was purified to near homogeneity. It has a molecular weight of 31 000 and a pI of approx. 9.8. Although not cytolytic itself, it protected red cells from hemolysis by staphylococcal sphingomyelinase (beta-hemolysin) and helianthus toxin. The apparently non-enzymatic cytolysin (helianthus toxin) from the sea anemone Stoichactis helianthus also interacts with membrane sphingomyelin. C. ovis and helianthus toxins were compared with regard to their effects on liposome model membranes, and they were found both to produce changes analogous to those in erythrocytes. Only helianthus toxin caused release of trapped glucose marker, but liposomes could be protected from release by pretreatment with C. ovis toxin. Both toxins demonstrated binding to sphingomyelin-containing liposomes, but only the bacterial sphingomyelinase catalyzed the release of choline from these vesicles.

Corynebacterium↗

PubMed2026

Contrasting redox-related physiological responses associated with HaGATA23 and HaGATA36 during Orobanche cumana parasitism in sunflower (Helianthus annuus L.).

Helianthus annuus is an economically important Asteraceae species used for seed oil production and ornamental purposes, but its production is seriously affected by the root-parasitic plant Orobanche cumana. GATA transcription factors are zinc-finger DNA-binding regulators involved in plant development and stress adaptation. However, the molecular characteristics of GATA transcription factors in Helianthus annuus and their contribution to Helianthus annuus -Orobanche cumana interaction remain poorly understood. Here, 36 HaGATA members were retrieved from the Helianthus annuus genome and classified into four phylogenetic clades. Chromosomal placement, collinearity, gene structure, motif composition, and promoter elements varied among the 36 HaGATA members, indicating evolutionary conservation coupled with functional diversification. Expression analysis and RT-qPCR analyses revealed differential expression patterns among HaGATA genes under O. cumana stress, with HaGATA23 markedly downregulated and HaGATA36 strongly upregulated. Overexpression of HaGATA23 was associated with increased malondialdehyde (MDA) accumulation and unfavorable changes in antioxidant enzyme activities, whereas its silencing showed the opposite physiological tendency. In contrast, overexpression of HaGATA36 reduced malondialdehyde accumulation, increased peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD) activities, while its silencing showed the reverse tendency. These results indicate that HaGATA23 and HaGATA36 are candidate genes associated with contrasting redox-related physiological responses during O. cumana stress. This work provides evidence that GATA transcription factors are associated with redox-related physiological responses in sunflower under O. cumana treatment and identifies HaGATA23 and HaGATA36 as functionally divergent candidate genes for further validation.

Helianthus↗

PubMed2003

Analysis of a dehydrin encoding gene and its phylogenetic utility in Helianthus.

Dehydrins are ubiquitous plant proteins, synthesized in late stages of plant embryo development and following any environmental stress involving dehydration. With the aim to study the evolution of such a stress-responsive gene within Helianthus and to test the possibility of using this gene for phylogenetic studies, fragments of the same dehydrin gene were isolated by PCR and sequenced in 16 wild Helianthus species or subspecies. All isolated sequences included the typical dehydrin domains (Y, S and K), a portion of 3'-UTR and an intron, inserted in the same position within the S domain-encoding region. The number of nucleotide substitutions (both synonymous and nonsynonymous) was calculated keeping separate the different gene regions, and differences occur even among coding domains, indicating that evolutionary constraints act differently on each region. The occurrence of indels and/or insertions was also observed. At the deduced protein level, the calculation of isoelectric point, molecular weight and the percentage of alpha-helix showed a diversification of biochemical properties of this protein between annual and perennial Helianthus species. Phylogenetic trees were built by the maximum-likelihood, maximum-parsimony, and neighbor-joining methods. In all cases the same topology was observed; perennial and annual species form a supported clade, and H. annuus was separated from the other annuals and from perennials. These data support the use of this stress-responsive gene to study the phylogeny of Helianthus.

Amino Acid Sequence↗

PubMed2004

Reconstructing the origin of Helianthus deserticola: survival and selection on the desert floor.

The diploid hybrid species Helianthus deserticola inhabits the desert floor, an extreme environment relative to its parental species Helianthus annuus and Helianthus petiolaris. Adaptation to the desert floor may have occurred via selection acting on transgressive, or extreme, traits in early hybrids between the parental species. We explored this possibility through a field experiment in the hybrid species' native habitat using H. deserticola, H. annuus, H. petiolaris, and two populations of early-generation (BC(2)) hybrids between the parental species, which served as proxies for the ancestral genotype of the ancient hybrid species. Character expression was evaluated for each genotypic class. Helianthus deserticola was negatively transgressive for stem diameter, leaf area, and flowering date, and the latter two traits are likely to be advantageous in a desert environment. The BC(2) hybrids contained a range of variation that overlapped these transgressive trait means, and an analysis of phenotypic selection revealed that some of the selective pressures on leaf size and flowering date, but not stem diameter, would move the BC(2) population toward the H. deserticola phenotype. Thus, H. deserticola may have originated from habitat-mediated directional selection acting on hybrids between H. annuus and H. petiolaris in a desert environment.

Adaptation, Physiological↗

PubMed1994

Pattern of cross-sensitivity between 4 Compositae plants, Parthenium hysterophorus, Xanthium strumarium, Helianthus annuus and Chrysanthemum coronarium, in Indian patients.

To assess the pattern of cross-sensitivity between 4 members of the Compositae family, namely Parthenium hysterophorus L., Xanthium strumarium L., Helanthus annuus L. and Chrysanthemum coronarium L., 63 patients clinically diagnosed to have airborne contact dermatitis, and 51 controls having well-defined patterns of contact dermatitis caused by agents other than plants, were patch tested with measured amounts of standardized aqueous extracts of these plants. Positive reactions were obtained in 62 patients and 13 controls with Parthenium hysterophorus, in 47 patients and 9 controls with Xanthium strumarium, in 7 patients and 2 controls with Helianthus annuus, and in 13 of the 57 patients and one out of 28 controls tested with Chrysanthemum coronarium. 2 patients were allergic to all 4 of the plants; 14 patients to 3 plants, namely Parthenium, Xanthium and Chrysanthemum in 9 cases and Parthenium, Xanthium and Helianthus in 5 cases; 32 patients to 2 plants, namely Parthenium and Xanthium in 30 cases, and Parthenium and Chrysanthemum, and Xanthium and Chrysanthemum in 1 case each; 15 patients were allergic to 1 plant only, that being Parthenium. All the 47 patients allergic to Xanthium, 13 patients allergic to Chrysanthemum and 7 patients allergic to Helianthus were positive with some other plant as well. There was 1 patient who was allergic to Xanthium and Chrysanthemum but not to Parthenium. The titre of contact hypersensitivity (TCH) determined in the patients allergic to Parthenium, Xanthium and Helianthus showed values that varied widely with each plant in different patients, and there was no parallelism between the TCH with various plants.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed2002

Occurrence of partial hybrids in wide crosses between sunflower ( Helianthus annuus) and perennial species H. mollisand H. orgyalis.

Hybridisation between the annual diploid sunflower ( Helianthus annuus)and the perennial diploid species Helianthus mollis and Helianthus orgyalis was obtained by means of a normal crossing procedure or embryo rescue. Hybridisation success was low. All plants examined cytologically appeared to be diploid. However, the phenotypes of these diploids were not intermediate between the parents and, despite great variation, they resembled the female parent-type predominantly. Thirty five percent of plants issued from sunflower pollinated with perennial Helianthus had a phenotype resembling the female sunflower parent. On average, only 5% of the minimum number of expected RAPD and RFLP bands from male parents were recovered in plants produced from mature seeds after pollination of sunflower by H. mollis. More hybrids were found among plants obtained from embryo rescue, with an average of 25% of the male parent bands recovered per plant. Analysis of individual plants indicated the occurrence of various levels of hybridisation. There was a significant positive correlation between the number of phenotype traits related to hybrid status and the number of bands derived from the male parent. A single hybrid plant might possibly represent the product of a 'normal' hybridisation event. The mechanisms behind these unusual events and the consequences for the breeder are discussed.

Journal Article↗

PubMed2002

Molecular mapping of the Rf1 gene restoring pollen fertility in PET1-based F1 hybrids in sunflower (Helianthus annuus L.).

Up to now a single cytoplasmic male sterility (CMS) source, PET1, is used worldwide for hybrid breeding in sunflower. Introgression of the restorer gene Rf1, responsible for fertility restoration, into new breeding material requires tightly linked markers to perform an efficient marker-assisted selection. A survey of 520 decamer primers by bulked segregant analyses identified five RAPD markers linked to the restorer gene Rf1. In a F(2) population of 183 individuals one of the RAPD markers, OPK13_454, mapped 0.8 cM from Rf1, followed by OPY10_740 with 2 cM. Bulked segregant analyses using 48 AFLP primer combinations identified 17 polymorphisms, which could be mapped in the same linkage group as Rf1. E33M61_136, and E41M48_113 were mapped 0.3 cM and 1.6 cM from the gene, respectively. Conversion of E41M48_113 into a sequence-specific marker resulted in a monomorphic pattern. However, two of the RAPD markers, OPK13_454 and OPY10_740, were successfully converted into SCAR markers, HRG01 and HRG02, which are now available for marker-assisted selection. To investigate the utility of these SCAR markers in other cross-combinations they were tested in a set of 20 lines. Comparison of the patterns of 11 restorer and nine maintainer lines of PET1 demonstrated that the markers OPK13_454/HRG01 and HRG02 were absent in all maintainer lines but present in all restorer lines, apart from the high oleic line RHA348 and the dwarf line Gio55. In addition, restorer lines developed from the interspecific hybrids Helianthus annuus x Helianthus mollis and H. annuus x Helianthus rigidus gave the same characteristic amplification products.

Chromosome Mapping↗

PubMed2006

Adaptive introgression of herbivore resistance traits in the weedy sunflower Helianthus annuus.

The role of hybridization in adaptive evolution is contentious. While many cases of adaptive trait introgression have been proposed, the relevant traits have rarely been identified, resulting in a lack of clear examples of this process. Here, we examine a purported case of adaptive introgression in which the annual sunflower Helianthus annuus annuus has captured alleles from a congener (Helianthus debilis) to form a stabilized hybrid, Helianthus annuus texanus. We tested the hypotheses that herbivore resistance traits have introgressed from H. debilis to H. annuus and have increased adaptation in the latter. In two common gardens, fitness (estimated by seed production) was on average 55% higher in H. a. texanus than in H. a. annuus. For H. a. texanus, three damage traits (of seven tested) differed significantly from the H. a. annuus parent in one or both sites and were shifted in the direction of the more resistant H. debilis. Natural selection favored H. a. annuusxH. debilis BC(1) hybrids (synthesized to mimic the ancestors of H. a. texanus) with H. debilis-like resistance to seed midges Neolasioptera helianthis and to receptacle/seed feeding Lepidoptera at one or both sites. Assuming similar herbivore pressures in the past, these results suggest that introgression of biotic resistance traits was important in the adaptation of H. annuus to central and southern Texas.

Adaptation, Biological↗

PubMed2006

EST databases as a source for molecular markers: lessons from Helianthus.

Expressed sequence tag (EST) databases represent a potentially valuable resource for the development of molecular markers for use in evolutionary studies. Because EST-derived markers come from transcribed regions of the genome, they are likely to be conserved across a broader taxonomic range than are other sorts of markers. This paper describes a case study in which the publicly available cultivated sunflower (Helianthus annuus) EST database was used to develop simple sequence repeat (SSR) markers for use in the genetic analysis of a rare sunflower species, Helianthus verticillatus, as well as the more widespread Helianthus angustifolius. EST-derived SSRs were found to be more than 3 times as transferable across species as compared with anonymous SSRs (73% vs. 21%, respectively). Moreover, EST-SSRs whose primers were located within protein-coding sequence were more readily transferable than those derived from untranslated regions, and the former loci were no less variable than the latter. The utility of existing EST databases as a means for facilitating population genetic analyses in plants was further explored by cross-referencing publicly available EST resources against available lists of rare or invasive flowering plant taxa. This survey revealed that more than one-third of all plant-derived EST collections of sufficient size could conceivably serve as a source of EST-SSRs for the analysis of rare, endangered, or invasive plant species worldwide.

Asteraceae↗

PubMed2003

The origin of ecological divergence in Helianthus paradoxus (Asteraceae): selection on transgressive characters in a novel hybrid habitat.

Diploid hybrid speciation in plants is often accompanied by rapid ecological divergence between incipient neospecies and their parental taxa. One plausible means by which novel adaptation in hybrid lineages may arise is transgressive segregation, that is, the generation of extreme phenotypes that exceed those of the parental lines. Early generation (BC2) hybrids between two wild, annual sunflowers, Helianthus annuus and Helianthus petiolaris, were used to study directional selection on transgressive characters associated with the origin of Helianthus paradoxus, a diploid hybrid species adapted to extremely saline marshes. The BC2 plants descended from a single F1 hybrid backcrossed toward H. petiolaris. The strength of selection on candidate adaptive traits in the interspecific BC2 was measured in natural H. paradoxus salt marsh habitat. Positive directional selection was detected for leaf succulence and Ca uptake, two traits that are known to be important in salt stress response in plants. Strong negative directional selection operated on uptake of Na and correlated elements. A significant decrease in trait correlations over time was observed in the BC2 population for Na and Ca content, suggesting an adaptive role for increased Ca uptake coupled with increased net exclusion of Na from leaves. Patterns of directional selection in BC2 hybrids were concordant with character expression in the natural hybrid species, H. paradoxus, transplanted into the wild. Moreover, the necessary variation for generating the H. paradoxus phenotype existed only in the BC2 population, but not in samples of the two parental species, H. annuus and H. petiolaris. These results are consistent with the hypothesis that transgressive segregation of elemental uptake and leaf succulence contributed to the origin of salt adaptation in the diploid hybrid species H. paradoxus.

Adaptation, Biological↗

PubMed2006

Microsatellite signature of ecological selection for salt tolerance in a wild sunflower hybrid species, Helianthus paradoxus.

The hybrid sunflower species Helianthus paradoxus inhabits sporadic salt marshes in New Mexico and southwest Texas, USA, whereas its parental species, Helianthus annuus and Helianthus petiolaris, are salt sensitive. Previous studies identified three genomic regions - survivorship quantitative trait loci (QTLs) - that were under strong selection in experimental hybrids transplanted into the natural habitat of H. paradoxus. Here we ask whether these same genomic regions experienced significant selection during the origin and evolution of the natural hybrid, H. paradoxus. This was accomplished by comparing the variability of microsatellites linked to the three survivorship QTLs with those from genomic regions that were neutral in the experimental hybrids. As predicted if one or more selective sweeps had occurred in these regions, microsatellites linked to the survivorship QTLs exhibited a significant reduction in diversity in populations of the natural hybrid species. In contrast, no difference in diversity levels was observed between the two microsatellite classes in parental populations.

Adaptation, Biological↗