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Comparison of ornamental and wild saltcedar (Tamarix SPP.) along Eastern Montana, USA riverways using chloroplast and nuclear DNA sequence markers

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Abstract

Saltcedars (Tamarix ramosissima, T. chinensis, and their hybrids) have invaded riverways and lakeshores across the western USA and northern Mexico. In Montana, ornamental plantings of saltcedar have been hypothesized, to varying degrees, to be the origin of nearby, wild populations. To examine this hypothesis, we compared chloroplast and nuclear DNA sequences from 36 ornamental and 182 wild saltcedars from Montana, North Dakota, and Wyoming, USA. We found that ornamental and wild population genotype frequencies were highly dissimilar. Also, genotype frequencies of hypothetical propagule populations under scenarios of random mating, self-fertilization, and clonal reproduction in the ornamental population were highly dissimilar to the genotype frequencies of the wild populations. Assignment tests indicated that the majority of wild genotypes originated from other wild plants, not from ornamental plants. However, ornamental plants could not be excluded as contributors to wild populations because all chloroplast and nuclear haplotypes found in the ornamental plants were found at some frequency in the wild. These findings suggest that while ornamental saltcedars are not the sole source of wild saltcedar, they do have potential to contribute genetic material to an invasion or re-establish a population after existing wild saltcedars are removed.

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... Leaf tissue was collected from ten individuals grown from the T. chinensis and T. ramosissima on 27 January 2014. Tamarix species identities were determined through Amplified Fragment Length Polymorphism (AFLP) analyses performed at the USDA Northern Plains Agricultural Research Laboratory in Sidney, MT, USA [56]. ...
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Tamarix spp. (saltcedar) were introduced from Asia to the southern United States as windbreak and ornamental plants and have spread into natural areas. This study determined differential gene expression responses to water deficit (WD) in seedlings of T. chinensis and T. ramosissima from established invasive stands in New Mexico and Montana, respectively. A reference de novo transcriptome was developed using RNA sequences from WD and well-watered samples. Blast2GO analysis of the resulting 271,872 transcripts yielded 89,389 homologs. The reference Tamarix (Tamaricaceae, Carophyllales order) transcriptome showed homology with 14,247 predicted genes of the Beta vulgaris subsp. vulgaris (Amaranthaceae, Carophyllales order) genome assembly. T. ramosissima took longer to show water stress symptoms than T. chinensis. There were 2068 and 669 differentially expressed genes (DEG) in T. chinensis and T. ramosissima, respectively; 332 were DEG in common between the two species. Network analysis showed large biological process networks of similar gene content for each of the species under water deficit. Two distinct molecular function gene ontology networks (binding and transcription factor-related) encompassing multiple up-regulated transcription factors (MYB, NAC, and WRKY) and a cellular components network containing many down-regulated photosynthesis-related genes were identified in T. chinensis, in contrast to one small molecular function network in T. ramosissima.
... Hybridization can also provide novel gene combinations that may promote adaptations to specific ecological problems in the new range that were not expressed by either parental lineage, as well as help overcome genetic bottlenecks that arise from founder effects (Anderson, 1953;Dlugosch and Parker, 2008). Furthermore, studies have shown that most naturalized Tamarix are more closely related to other wild naturalized Tamarix than they are to nearby ornamental populations, suggesting that most recent recruitment has occurred from naturalized individuals, despite potential gene flow between ornamental and naturalized populations (Gaskin and Kazmer, 2006). This suggests that naturalized genetic sources may be better adapted for successful invasion into these ecosystems than cultivated genetic lineages. ...
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Patterns of woody-plant mortality have been linked to global-scale environmental changes, such as extreme drought, heat stress, more frequent and intense fires, and episodic outbreaks of insects and pathogens. Although many studies have focussed on survival and mortality in response to specific physiological stresses, little attention has been paid to the role of genetic heritability of traits and local adaptation in influencing patterns of plant mortality, especially in non-native species. Tamarix spp. is a dominant, non-native riparian tree in western North America that is experiencing dieback in some areas of its range due to episodic herbivory by the recently introduced northern tamarisk leaf beetle (Diorhabda carinulata). We propose that genotype × environment interactions largely underpin current and future patterns of Tamarix mortality. We anticipate that (i) despite its recent introduction, and the potential for significant gene flow, Tamarix in western North America is generally adapted to local environmental conditions across its current range in part due to hybridization of two species; (ii) local adaptation to specific climate, soil and resource availability will yield predictable responses to episodic herbivory; and (iii) the ability to cope with a combination of episodic herbivory and increased aridity associated with climate change will be largely based on functional tradeoffs in resource allocation. This review focusses on the potential heritability of plant carbon allocation patterns in Tamarix, focussing on the relative contribution of acquired carbon to non-structural carbohydrate (NSC) pools versus other sinks as the basis for surviving episodic disturbance. Where high aridity and/or poor edaphic position lead to chronic stress, NSC pools may fall below a minimum threshold because of an imbalance between the supply of carbon and its demand by various sinks. Identifying patterns of local adaptation of traits related to resource allocation will improve forecasting of Tamarix population susceptibility to episodic herbivory. © The Author 2017. Published by Oxford University Press and the Society for Experimental Biology.
... In fact, the selectivity for T. ramosissima (sensu lato) over T. parviflora by D. carinulata may be a positive trait for implementation of the saltcedar biocontrol program. Ornamental saltcedars are planted throughout the western states for landscaping purposes, and T. parviflora is often used for this purpose (Gaskin & Kazmer 2006, T. Dudley, personal observations). It may be that the horticultural value of this form outweighs the impacts of its limited invasion, and avoidance mitigates the need to protect landscape plants from herbivory by applying insecticides. ...
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... T. ramosissima), a xero-halophyte shrub or small tree, is widely distributed in the drought-prone and saline lands in Central Asia and China. It is an economically important species used as fodder (dry young branches), as ornamental plant, in making farming tools, medium-density particle board, fire-proof plywood board and as fuel wood in the local area (Song et al., 2003; Gaskin & Kazmer, 2006; Zheng et al., 2006). Recent research has showed that T. chinensis can be used as host for the parasite Cistanche tubulosa,which yields expensive Chinese natural medicine (Ma et al., 2005). ...
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Saltcedar (Family Tamaricaceae) is an invasive species in the U.S. Two species, Tamarix ramosissima and T. parviflora, are present in the southwestern and western U.S. Saltcedar was first reported in the U.S. in 1837 and was planted to stabilize stream banks. It now occupies over 1.5 million acres of riparian habitat in the West. Approximately 29,000 acres on 33 national wildlife refuges; managed by the U.S. Fish and Wildlife Service strictly for conservation of fish, wildlife, and plants, and their habitats; are impact-ed by saltcedar. All four priorities of the Director-U.S. Fish and Wildlife Service, concern wildlife habitats and invasive species in some manner. Saltcedar weed management is tied to each of these four priories. The Saltcedar Consortium (consisting of private organiza-tions; local, state, and federal agencies; and academia) has been developed to provide sci-ence-based leadership on saltcedar biological control. The U.S. Fish and Wildlife Service provided consultation, under authority of the Endangered Species Act for the endangered southwestern willow flycatcher, Empidonax traillii extimus, with the U.S. Dept. Agriculture-Animal and Plant Health Inspection Service for release of two saltcedar bio-logical control insects (saltcedar leaf beetle, Diorhabda elongata and mealybug, Trabutina mannipara) in the western U.S. On-going and future biological control of weeds work demands continuing discussions between scientists to meet Endangered Species Act requirements; one place of contact for such communication is with the region-al integrated pest and weed management coordinators together with aquatic nuisance species coordinators in the U.S. Fish and Wildlife Service.
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Introduced saltcedar (Tamarix ramosissima, T. chinensis, and their hybrids) reaches its northward distribution in the Great Plains in Montana, USA. We mapped the locations, patterns of abundance, and ages of saltcedar along the Musselshell River and Fort Peck Reservoir in northeastern Montana to identify concentrations of plants that could be used to infer introduction location, establishment year, and mechanisms of dispersal. We estimated the presence of 24,500 plants on the Musselshell River over a river distance of 240 km, with concentrations at three nodes close to Roundup (2,000 plants, seedlings to 24 years), Melstone (6,000 plants, seedlings to 23 years), and the mouth of the river at Fort Peck Reservoir (10,000 plants, seedlings to at least 11 years). Concentrations at Roundup and Melstone probably originated from urban plantings in the 1960s. The third concentration may have established from seeds and plant pieces washed downriver during floods and deposited in the hydraulic backwater of the Musselshell River delta at Fort Peck Reservoir. We believe there may be one-half to one million plants on Fort Peck Reservoir, with concentration nodes at recreation areas on the south shore. We estimated 3,500 mature saltcedar to be present at the Devils Creek Recreation Area, more than 11,000 plants at Hell Creek Recreation Area, and more than 40,000 plants at 6 sites at the south end of Dry Arm close to the Nelson Creek Recreation Area and mouth of Big Dry Creek. The oldest plants on the reservoir were 21 to 33 years old in 2001. Based on these ages, we suggest that saltcedar arrived at the south shore of Fort Peck Reservoir in the mid- to late 1960s, which means that it must have dispersed from the Bighorn/Yellowstone River system soon after it became established in southern Montana. Although wind dispersal and ornamental plantings cannot be ruled out as primary transport mechanisms to the reservoir, the concentrations and ages of saltcedar at recreation areas suggest that seeds and other plant propagules were also transported to the reservoir by earth-moving equipment during site construction between 1966 and the mid-1980s and later by boats and their towing vehicles. Saltcedar was dispersed away from these nodes by wind and water. As Tamarix ramosissima and T. chinensis originated in the cold dry deserts of northeastern Asia, saltcedar may not be limited in its northward expansion by the cold winters, short growing seasons, and periodic droughts characteristic of the northern Great Plains in Canada.
Chapter
Banquo’s metaphorical plea to the witches of Shakespeare’s play is echoed literally by managers of natural areas today. Invasive nonindigenous (NI) plants have an increasing presence in natural areas worldwide; it appears that there are virtually no nature reserves in the world that are immune from this problem (Usher 1988). As resource managers are faced with dwindling resources allocated to an increasing number of management problems, the ability to predict which introduced plant will become invasive (“which grain will grow and which will not”) would be of great value. We are beginning to develop such prescient ability.
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Direct sequencing of genomic DNA from diploid individuals leads to ambiguities on sequencing gels whenever there is more than one mismatching site in the sequences of the two orthologous copies of a gene. While these ambiguities cannot be resolved from a single sample without resorting to other experimental methods (such as cloning in the traditional way), population samples may be useful for inferring haplotypes. For each individual in the sample that is homozygous for the amplified sequence, there are no ambiguities in the identification of the allele's sequence. The sequences of other alleles can be inferred by taking the remaining sequence after "subtracting off" the sequencing ladder of each known site. Details of the algorithm for extracting allelic sequences from such data are presented here, along with some population-genetic considerations that influence the likelihood for success of the method. The algorithm also applies to the problem of inferring haplotype frequencies of closely linked restriction-site polymorphisms.
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Biological invasions are drastically altering natural habitats and threatening biodiversity on both local and global levels. In one of the United States' worst invasions, Eurasian Tamarix plant species have spread rapidly to dominate over 600,000 riparian and wetland hectares. The largest Tamarix invasion consists of Tamarix chinensis and Tamarix ramosissima, two morphologically similar species. To clarify the identity, origins, and population structuring of this invasion, we analyzed DNA sequence data from an intron of a nuclear gene, phosphoenolpyruvate carboxylase (PepC). This intron proved to be highly variable at the population level, and the 269 native and invasive specimens yielded 58 haplotypes, from which we constructed a gene genealogy. Only four of these haplotypes were common to both the U.S. and Eurasia. Surprisingly, we found that the most common plant in this U.S. invasion is a hybrid combination of two species-specific genotypes that were geographically isolated in their native Eurasian range. Less extensive hybrids exist in the invasion, involving combinations of T. ramosissima and T. chinensis with Tamarix parviflora and Tamarix gallica. The presence of potentially novel hybrids in the U.S. illustrates how importation of exotics can alter population structures of species and contribute to invasions.
Article
Summary 429 Acknowledgements 440 References 440 Genetically modified (GM) plants are rapidly becoming a common feature of modern agriculture. This transition to engineered crops has been driven by a variety of potential benefits, both economic and ecological. The increase in the use of GM crops has, however, been accompanied by growing concerns regarding their potential impact on the environment. Here, we focus on the escape of transgenes from cultivation via crop × wild hybridization. We begin by reviewing the literature on natural hybridization, with particular reference to gene flow between crop plants and their wild relatives. We further show that natural selection, and not the overall rate of gene flow, is the most important factor governing the spread of favorable alleles. Hence, much of this review focuses on the likely effects of transgenes once they escape. Finally, we consider strategies for transgene containment.
Division of Biological Sciences. Univer-sity of Montana
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Stellflug, and other county weed-coordinators kindly assisted in locating or collecting plant samples. T. Unruh, F. Ryan, and two anonymous reviewers provided helpful comments on earlier versions of the manuscript
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