Kristin Saltonstall

Cryptic invasion by a non-native genotype of the common reed, Phragmites australis, into North America

Cryptic invasions are a largely unrecognized type of biological invasion that lead to underestimation of the total numbers and impacts of invaders because of the difficulty in detecting them. The distribution and abundance of Phragmites australis in North America has increased dramatically over the past 150 years. This research tests the hypothesis that a non-native strain of Phragmites is responsible for the observed spread. Two noncoding chloroplast DNA regions were sequenced for samples collected worldwide, throughout the range of Phragmites. Modern North American populations were compared with historical ones from herbarium collections. Results indicate that an introduction has occurred, and the introduced type has displaced native types as well as expanded to regions previously not known to have Phragmites. Native types apparently have disappeared from New England and, while still present, may be threatened in other parts of North America.

Expansion of Phragmites australis into tidal wetlands of North America

Phragmitesexpansion into tidal wetlands of North America is most extensive along the northern and middle Atlantic coasts, but over 80% of the US coastal wetland area occurs along the Gulf of Mexico and southern Atlantic coasts and may be susceptible to ongoing expansion. Rapid spread of Phragmiteshas been documented in freshwater (<0.5 ppt), oligohaline (0.5‐5 ppt) and mesohaline (5‐18 ppt) tidal wetlands. The advance of Phragmites into tidal wetlands of North America may have been facilitated by widespread coastal changes since European settlement, including disturbance of hydrologic cycles and nutrient regimes; the presence of Phragmiteshas become a signature of tidal wetland alteration. Although ploidy levels from 2n = 36 to 72 have been documented for Phragmites throughout the continent, no genetics research to date has tested whether recent introduction of aggressive clones could account for Phragmites expansion. A fundamental concern regarding Phragmitesexpansion, particularly into tidal freshwater wetlands, is the observed reduction in biodiversity as many native species of plants are replaced by a more cosmopolitan species. Commensurate with a shift in habitat type is a reduction in insect, avian and other animal assemblages. Ecosystem services, including support of higher trophic levels, enhancement of water quality and sediment stabilization, however, are not diminished when a tidal wetland becomes dominated by Phragmites, provided that tidal flooding is retained. ©1999 Elsevier Science B.V. All rights reserved.

Genetic Variation among North American Populations of Phragmites australis: Implications for Management

Over the past century, the distribution and abundance ofPhragmites australis (common reed) has dramatically increased in both freshwater and brackish wetlands throughout North America. It has been hypothesized that the increased competitive ability ofPhragmites could be the result of an introduction of a more aggressive genotype. Sequence data from 2 noncoding regions of the chloroplast genome show that, historically, 11 native haplotypes were found across North America and population-structuring distinguishing samples from the Atlantic Coast, Midwest, West, and Gulf Coast regions of the continent was evident. Today a single genetically-distinct haplotype dominates the Atlantic Coast and is also found across the continent in lower frequencies; this type is common in Europe and Asia and has most likely been introduced to North America. Comparisons of modern populations with historic samples show that along the Atlantic Coast, this cosmopolitan type has replaced native haplotypes and it is invading new sites throughout the rest of the country. In the Midwest and West, native populations are still common but introduced populations are found along roadsides throughout the area. Gulf Coast populations are dominated by another population type that is genetically distinct from all other North American population types.

A rapid method for identifying the origin of North American Phragmites populations using RFLP analysis

The common reed,Phragmites australis, is a common feature in wetlands across North America. Recent studies have suggested that the widespread invasions of this species may be due to the introduction of a non-native strain from EurAsia. Since native population types is needed to facilitate management of ulations are also found, a method for distinguishing population persist in many areas where introduced populations are also found, a method for distinguishing population types is needed to facilitate management of the species. A restriction fragment length polymorphism (RFLP) assay was developed to distinguish native, non-native, and Gulf Coast type populations ofPhragmites from each other. Two amplified non-coding chloroplast DNA regions are each cut with one restriction enzyme, allowing the distinction of native, non-native and Gulf Coast haplotypes from each other. When used together, these cut sites provide a low cost, rapid way of determining the origin ofPhragmites populations.

Survey of Grauer's gorillas (Gorilla gorilla graueri) and eastern chimpanzees (Pan troglodytes schweinfurthi) in the Kahuzi-Biega National Park lowland sector and adjacent forest in eastern Democratic Republic of Congo

We describe the distribution and estimate densities of Grauers gorillas (Gorilla gorilla graueri) and eastern chimpanzees (Pan troglodytes schweinfurthi) in a 12,770-km2area of lowland forest between the Lowa, Luka, Lugulu, and Oku rivers in eastern Democratic Republic of Congo, the site of the largest continuous population of Grauers gorillas. The survey included a total of 480 km of transects completed within seven sampling zones in the Kahuzi-Biega National Park lowland sector and adjacent Kasese region and approximately 1100 km of footpath and forest reconnaissance. We estimate total populations of 7670 (4180–10,830) weaned gorillas within the Kahuzi-Biega lowland sector and 3350 (1420–5950) individuals in the Kasese survey areas. Within the same area, we estimate a population of 2600 (1620–4500) chimpanzees. Ape nest site densities are significantly higher within the Kahuzi-Biega lowland sector than in the more remote Kasese survey area in spite of a significantly higher encounter rate of human sign within the lowland sector of the park. Comparison of our data with information obtained by Emlen and Schaller during the first rangewide survey of Grauers gorillas in 1959 suggests that gorilla populations have remained stable in protected areas but declined in adjacent forest. These findings underscore the key role played by national parks in protecting biological resources in spite of the recent political and economic turmoil in the region. We also show that forest reconnaissance is a reliable and cost-effective method to assess gorilla densities in remote forested areas.

Ecology and Impacts of the Large-Statured Invasive Grasses Arundo donax and Phragmites australis in North America

Abstract Large-statured invasive grasses (LSIGs) constitute a distinct functional group with characteristic life history traits that facilitate colonization and aggressive growth in aquatic ecosystems, particularly those modified by human activities. These species typically form monocultures in the systems they invade and have wide-ranging and negative impacts on biodiversity and ecosystem processes. In March 2008, a special symposium was held as part of the Western Society of Weed Scientists annual meeting to synthesize our current knowledge of the ecological impacts and management of two notorious LSIGs: Arundo donax and Phragmites australis. In this volume of Invasive Plant Science and Management, symposium participants provide articles summarizing existing knowledge, recent research progress, and research needs for these two taxa. Here, we summarize the basic biology of these species and suggest the use of a more holistic approach to deal with the effects and management of LSIG invasions. Nomenclature: Giant reed, Arundo donax L.; common reed, Phragmites australis (Cav.) Trin. ex Steud.

Paleoecological and genetic analyses provide evidence for recent colonization of native Phragmites australis populations in a Lake Superior wetland

Over the past several decades, populations of the common reed, Phragmites australis, have expanded rapidly in salt marshes of coastal North America, creating dramatic changes in community composition. Populations of Phragmites in coastal wetlands of the Great Lakes may similarly threaten the ecological integrity of these inland wetland communities. Strategies for the conservation of biodiversity in these wetlands should be informed by an understanding of both the recent trends and the historic role of Phragmites in these wetlands. A combination of paleoecological and genetic analyses was used to determine when Phragimites became established in a Lake Superior coastal wetland and whether the source of Phragmites was native or non-native populations. Radiocarbon-dated stratigraphic changes in the abundance of pollen and macroscopic plant remains were used to infer the timing of vegetation changes in the wetland. From about 1100–490 14C yr ago, low water levels were associated with a lowland conifer forest with wetland swales at this site. At about 490 BP, conifers became less common, and peatlands became established at the site, perhaps in response to higher water levels in the wetland. There is no evidence that Phragmites grew at the site until the last several decades, suggesting that it is not native to this wetland and that its recent expansion may create significant changes in the wetland community. However, genetic data from chloroplast DNA sequences and microsatellite markers indicate that it is a variety that is native to North America and common throughout the Midwest. Our results suggest that human-induced changes in the landscape in combination with long-term environmental changes may play an important role in the expansion of native Phragmites populations.

Genetics and Reproduction of Common (Phragmites australis) and Giant Reed (Arundo donax)

Abstract Genetic diversity and reproductive characteristics may play an important role in the invasion process. Here, we review the genetic structure and reproductive characteristics of common reed and giant reed, two of the most aggressive, large-statured invasive grasses in North America. Common reed reproduces both sexually and asexually and has a complex population structure, characterized by three subspecies with overlapping distributions; of which, one is introduced, one native, and the third is of unknown origins. These three subspecies show varying levels of genetic diversity, with introduced common reed having high levels of nuclear diversity, indicating that multiple introductions have likely occurred. In contrast, giant reed has low genetic diversity and appears to reproduce solely via asexual fragments yet is highly aggressive in parts of its introduced range. Both species are well-adapted for growth in human-dominated landscapes, which is presumably facilitated by their rhizomatous growth habit. Nomenclature: Common reed, Phragmites australis (Cav.) Trin. ex Steudel; giant reed, Arundo donax L

A Tale of Three Lineages: Expansion of Common Reed (Phragmites australis) in the U.S. Southwest and Gulf Coast

Abstract The common reed invasion in North America has spanned two centuries and is still ongoing. This expansion comprises two main forms: an introduced Eurasian lineage (identified here as “Introduced Phragmites”) and a Gulf Coast lineage of unknown origin (identified here as “Gulf Coast Phragmites”). Both lineages are spreading beyond their current ranges and are colonizing Southwestern and Gulf Coast ecosystems where they have not previously existed. As a result, the native North American lineage of common reed (hereafter “native Phragmites”) has declined in many places. The recent invasion of the U.S. Southwest by Introduced and Gulf Coast Phragmites lineages has made this the only region in the world colonized by all three lineages. Along the central Gulf Coast where Gulf Coast Phragmites remains the dominant form, Introduced Phragmites has also recently invaded the Mississippi River delta. The consequences of these new invasions are uncertain, but a rapid response is needed to protect native species and ecosystems and reduce future control costs. Nomenclature: Common reed, Phragmites australis (Cav.) Trin. ex Steud

Confirmed field hybridization of native and introduced Phragmites australis (Poaceae) in North America

PREMISE OF THE STUDY Intraspecific hybridization between native and introduced lineages of a species can increase invasiveness and may lead to the decline of native lineages. The introduction of Eurasian Phragmites australis has caused profound changes to wetland habitats across North America, yet evidence for hybridization between native and introduced Phragmites australis in North America is lacking and has puzzled researchers for over a decade. Here we present the first confirmed field hybridization event between the two lineages. METHODS Hybrid plants were initially recognized during field surveys by their intermediate morphology and distinct herbivore community. We verified hybrid status using chloroplast DNA haplotypes and microsatellite markers. KEY RESULTS Confirmed hybrid stems were restricted to one site and displayed morphological characteristics of both native and introduced P. australis. Based on their microsatellite profiles, all samples likely represent a single clone of a first generation hybrid. Sequencing of cpDNA indicates that the maternal parent is from the introduced lineage. CONCLUSIONS Identification of hybrid P. australis in the field is complex and requires multiple characters. All suspected hybrids should be verified using genetic techniques. Preventing the spread of introduced genes and genotypes through North America will require recognition and rapid management response to hybrid plants.