INVASÃO POR GRAMÍNEAS EXÓTICAS EM CAMPOS SOBRE PALEODUNAS: EFEITOS NA DIVERSIDADE FLORÍSTICA

O Refúgio de Vida Silvestre Banhado dos Pachecos localiza-se sobre a Coxilha das Lombas, Viamão/RS, e encontra-se em processo de invasão biológica por gramíneas exóticas na área de campo seco. Este fragmento de vegetação campestre sobre paleodunas é habitat da espécie endêmica Ctenomys lami (Rodentia, Ctenomydae) e apresenta composição florística peculiar em relação a maioria das áreas naturais dos Campos Sulinos, com espécies de Asteraceae sendo dominantes em comparação às espécies de Poaceae. Com o objetivo de caracterizar a composição florística e avaliar o grau e efeitos da invasão biológica sobre a comunidade de campo seco foi realizado um levantamento quantitativo. Foram amostradas 31 parcelas de 1 x 1 m e levantados dados de cobertura e altura da vegetação, solo descoberto e serrapilheira. Foram calculados parâmetros fitossociológicos para cada espécie. As parcelas foram classificadas quanto ao nível de invasão por gramíneas exóticas. O efeito da invasão sobre a composição e estrutura da vegetação foi avaliado a partir de Análise de Coordenadas Principais, regressão linear e análise de variância. As gramíneas exóticas invasoras Urochloa decumbens e Digitaria eriantha subsp. pentzii foram dominantes em grande parte da vegetação campestre, modificando a estrutura e composição vegetal conforme o nível de invasão. Cerca de um terço da área encontra-se altamente invadida. Ações de remoção e controle de invasoras se fazem urgentes, considerando que este é um dos poucos fragmentos de ecossistemas naturais abertos na Coxilha das Lombas e abriga espécies ameaçadas de extinção. INVASION BY EXOTIC GRASSES IN GRASSLAND ON PALAEODUNES: EFFECTS ON FLORISTIC DIVERSITY. The Banhado dos Pachecos Wildlife Refuge, located in the Coxilha das Lombas, in Viamão/RS, Brazil, is under a process of invasion by alien grasses in its areas of dry grassland. The grassland on palaeo-dunes is the habitat of the endemic species Ctenomys lami (Rodentia, Ctenomydae) and presents a peculiar floristic composition in relation to most natural grasslands in southern Brazil, with species of the Asteraceae dominating in comparison to grasses. In order to characterize the floristic composition and to evaluate the degree and effects of biological invasion on the grassland community, a quantitative vegetation survey was carried out. In 31 plots of 1 x 1 m, data on cover and height of vegetation, bare soil and litter were collected. Phytosociological parameters were calculated for each species. The plots were classified according to the level of invasion by exotic grasses and Principal Coordinate Analysis, linear regression and Analysis of Variance were performed to observe the species distribution in the community and the effects of the invasion on the richness and structure of the vegetation. The invasive exotic grasses Urochloa decumbens and Digitaria eriantha subsp.pentzii were dominant in grassland vegetation, modifying plant structure and composition according to the level of invasion. About a third of the area is heavily invaded. Invasive removal and control actions are urgent as this is one of the few fragments of natural grasslands in the Coxilha das Lombas and is habitat to species threatened with extinction.

Invasive exotic plant monitoring at Dinosaur National Monument: Results of the 2019 field season on the Green River, and the third completed monitoring rotation

Invasive exotic plant (IEP) species are a significant threat to natural ecosystem integrity and biodiversity, and controlling them is a high priority for the National Park Service. The Northern Colorado Plateau Network (NCPN) selected the early detection of IEPs as one of 11 monitoring protocols to be implemented as part of its long-term monitoring program. We also calculated a patch management index (PMI) to quantify the extent and density of invasive patches into a single value that helps identify the scale of the problem. Park managers can use this tool to help prioritize IEP treatment. At Dinosaur National Monument, the NCPN monitors IEPs in the Green and Yampa river corridors. This report summarizes data from monitoring on the Green River in 2019, and monitoring on the Yampa River in 2017, to represent the completion of the third monitoring rotation of the entire river corridor (2002–2005, 2010–2011, 2017–2019). During surveys conducted from June 26 to July 2, 2019, NCPN staff detected 12 priority IEP species and two non-priority species in a 84.6-hectare (209-acre) area along 74.4 kilometers of the Green River above (“upper”) and below (“low-er”) its confluence with the Yampa. A total of 2,535 IEP patches were detected. Of those patches, 24.2% and 15.6% were smaller than 40 m2 on the upper and lower Green River reaches, respectively. The patch management index (PMI) was low or very low for 95.7% of patches on the upper Green River and 90.9% of patches on the lower Green River. Tamarisk (Tamarix sp.), broad-leaf pepperwort (Lepidium latifolium), and yellow sweetclover (Meli-lotus officinalis) were the most widespread species. For the first time, NCPN monitoring detected teasel (Dipsacus sylvestris) on the upper Green River. Yellow sweetclover has increased on all three river reaches during the survey years. Musk thistle (Carduus nutans) was found at considerably lower levels than yellow sweetclover but has also increased on all three river reaches. Leafy spurge is increasing on the lower Green River and Yampa River. Cheatgrass was not monitored in the first rotation, but increased substantially in cover and percent frequency on all three river sections from 2010–2011 to 2017–2019. This increase may be due to a lack of recent high-flow scouring events. The highly regulated upper Green River generally has the highest number of IEPs, while the lower Green River has a moderate amount of IEPs. The largely unregulated flows of the Yampa River continue to result in a lower number of patches per kilometer, lower percent cover, and lower percent frequency than the upper or lower Green River. Network staff will return to the monument in 2022 to begin the fourth monitoring rotation.

Genomic Biosurveillance Detects A Sexual Hybrid in the Sudden Oak Death Pathogen

Invasive exotic pathogens pose a threat to trees and forest ecosystems worldwide1, hampering the provision of essential ecosystem services such as carbon sequestration and water purification2. Hybridization is a major evolutionary force that can drive the emergence of pathogens3. Phytophthora ramorum, an emergent pathogen that causes the sudden oak and larch death, spreads as reproductively isolated divergent clonal lineages. Sexual recombination has never been reported in this pathogen under natural conditions and laboratory crosses have yielded unfit progenies, suggesting postzygotic barriers to hybridization. Here we report the discovery in a plant nursery of novel variants of P. ramorum that are the result of homoploid hybridization via sexual recombination between North American and European lineages of the pathogen. We show that these hybrids are viable, can infect plants and produce spores for long-term survival and propagation. Genome sequencing revealed novel genotypic combinations, not present in the parental lineages, at 54,515 single nucleotide polymorphism loci. More than 6000 of the novel genotypes at these loci are predicted to have a functional impact in genes associated with host infection, including effectors, carbohydrate-active enzymes and proteases. We also observed post-meiotic mitotic recombination that could generate additional genotypic and phenotypic variation and contribute to homoploid hybrid speciation. Our study highlights the importance of plant pathogen biosurveillance to detect novel variants and inform management and control.

Review of Existing Knowledge and Practices of Tarping for the Control of Invasive Knotweeds

Managing invasive exotic plant species is a complex challenge, especially for Asian knotweeds (Reynoutria spp.). Tarping is a regularly cited but poorly documented control method, which consists of covering the ground with a tarp (agricultural tarp, geotextile, geomembrane, etc.) to create a physical barrier to hinder plant growth and deprive the plants of light in order to deplete their rhizomatous reserves. To improve our knowledge of tarping in order to identify the key factors of its success or failure, we reviewed the relevant grey and scientific literature and conducted an international survey among managers to collect feedback on tarping experiments. In the literature, as well as in the field, practices are quite heterogeneous, and the method’s effectiveness is highly contrasted. A better consideration of knotweed biology may improve the efficacy of the method. Based on the bibliography and survey work, we propose practical recommendations including covering the entire stand, extending the tarping up to 2.5 m beyond its edges for a period of at least six years, and ensuring regular monitoring. Even though tarping does not seem to be a one-size-fits-all solution to eradicate knotweed, it could still be a useful control method once knotweed has become a critical management issue.

Standardized invasive species terminology for effective education of Floridians

In this document we introduce a standardized set of seven terms compiled by the members of the UF|IFAS Invasive Species Council that can describe most situations involving invasive species. We do so to promote a common language among Florida’s Extension and outreach professionals. This will limit confusion caused by excessive jargon used to describe invasive species and the fact that much of this jargon is used incorrectly. This confusion hinders stakeholder understanding of environmental and economic impacts caused by invasive species which can prevent stakeholders from adopting behaviors that can both limit the introduction of new invasive species and decrease the impacts of those already established. The seven terms we propose are “native”, “nonnative”, “introduced”, “established”, “invasive”, “nuisance”, and “range change”. We also list six terms to avoid due to their tendency to create confusion and/or be misused and misinterpreted (“native invasive”, “invasive exotic”, “invasive weed”, “alien”, “foreign”, and “nonindigenous”) as well as precise definitions of common legal terms (“noxious weed”, “injurious”, “prohibited”, and “conditional/restricted”). By speaking this common language, Florida’s Extension and outreach professionals can deliver a simplified and unified message about the impacts of invasive species and how to best prevent and control them, potentially increasing the environmental and socioeconomic benefits of invasive species Extension and outreach programs.

Invasive exotic plant monitoring at Colorado National Monument: 2019 field season

Invasive exotic plant (IEP) species are a significant threat to natural ecosystem integrity and biodiversity, and controlling them is a high priority for the National Park Service. The North-ern Colorado Plateau Network (NCPN) selected the early detection of IEPs as one of 11 monitoring protocols to be implemented as part of its long-term monitoring program. This report represents work completed at Colorado National Monument during 2019. During monitoring conducted June 12–19, a total of 20 IEP species were detected on monitoring routes and transects. Of these, 12 were priority species that accounted for 791 separate IEP patches. IEPs were most prevalent along riparian areas. Yellow sweetclover (Melilotis officinale) and yellow salsify (Tragopogon dubius) were the most commonly detected priority IEPs along monitoring routes, representing 73% of all priority patches. Patches of less than 40 m2 were typical of nearly all priority IEP species except yellow sweetclover. A patch management index (PMI) was created by combining patch size class and percent cover for each patch. In 2019, a large majority of priority IEP patches were assigned a PMI score of low (46%) or very low (50%), indicating small and/or sparse patches where control is generally still feasible. This is similar to the numbers for 2017, when 99% of patches scored low or very low in PMI. Seventy-eight percent of tree patches were classified as seedlings or saplings, which require less effort to control than mature trees. Cheatgrass (Anisantha tectorum) was the most common IEP recorded in transects, found in 30–77% of transects across the different routes. It was the only species found in transects on all monitoring routes. When treated and untreated extra areas near the West Entrance were compared, the treated area had comparable or higher lev-els of IEPs than the untreated area. When segments of monitoring routes conducted between 2003 and 2019 were compared, results were mixed, due to the different species monitored in different time periods. But in general, the number of IEPs per 100 meters is increasing or remaining constant over time. There were notable increases in IEP patches per 100 meters on several routes in 2019: field bindweed (Convolvulus arvensis) along East Glade Park Road; Siberian elm (Ulmus pumila) in Red Canyon; yellow salsify along East Glade Park Road, No Thoroughfare Canyon, No Thoroughfare Trail, and Red Canyon; and yellow sweetclover in No Thoroughfare Canyon and Red Canyon. Network staff will return to re-sample monitoring routes in 2021.

Invasive exotic plant monitoring in Capitol Reef National Park: 2019 field season, Scenic Drive and Cathedral Valley Road

Invasive exotic plant (IEP) species are a significant threat to natural ecosystem integrity and biodiversity, and controlling them is a high priority for the National Park Service. The North-ern Colorado Plateau Network (NCPN) selected the early detection of IEPs as one of 11 monitoring protocols to be implemented as part of its long-term monitoring program. From May 30 to June 1, 2019, network staff conducted surveys for priority IEP species along the Scenic Drive and Cathedral Valley Road monitoring routes at Capitol Reef National Park. We detected 119 patches of six priority IEP species along 34 kilometers of the two monitor-ing routes. There were more patches of IEPs, and a higher percentage of large patches, than in previous years. This indicates that previously identified infestations have expanded and grown. The most common (47.1%) patch size among priority species was 1,000–2,000 m2 (0.25–0.5 acre). The vast majority (93.2%) of priority patches ranked either low (58.8%) or very low (34.4%) on the patch management index scale. Tamarisk (Tamarix sp., 72 patches) was the most prevalent priority IEP species. African mustard (Malcolmia africana, 32 patch-es), field bindweed (Convolvulus arvensis, 9 patches), and Russian olive (Elaeagnus angusti-folia, 3 patches) occurred less commonly. Together, these four species represented 97.5% of all patches recorded in 2019. Four IEP species were found on the monitored routes for the first time: Russian olive (Elaeagnus angustifolia), quackgrass (Elymus repens), Siberian elm (Ulmus pumila), and African mustard (Malcolmia africana, not on the priority species list before 2019). Cathedral Valley Road had higher IEP priority patches per kilometer (5.68) than the Scenic Drive (2.05). IEP species were found on 37.9% (25 of 66) of monitored transects. Almost all these detections were Russian thistle (Salsola sp.). Russian thistle was widespread, present in 33.3% of transects, with an estimated cover of 0.2% across all transects sampled. Across routes monitored in all three rotations (2012, 2015, and 2019), Russian thistle has increased in frequency. However, its frequency remained about the same from 2015 to 2019, and percent cover remains low. Tamarisk and field bindweed have both increased in preva-lence since monitoring began, with tamarisk showing a dramatic increase in the number and size of patches. Immediate control of tamarisk and these other species is recommended to reduce their numbers on these routes. The NCPN plans to Capitol Reef in 2020 to monitor Oak and Pleasant creeks, completing the third rotation of invasive plant monitoring.

Genic introgression from an invasive exotic fungal forest pathogen increases the establishment potential of a sibling native pathogen

Significant hybridization between the invasive North American fungal plant pathogen Heterobasidion irregulare and its Eurasian sister species H. annosum is ongoing in Italy. Whole genomes of nine natural hybrids were sequenced, assembled and compared with those of three genotypes each of the two parental species. Genetic relationships among hybrids and their level of admixture were determined. A multi-approach pipeline was used to assign introgressed genomic blocks to each of the two species. Alleles that introgressed from H. irregulare to H. annosum were associated with pathways putatively related to saprobic processes, while alleles that introgressed from the native to the invasive species were mainly linked to gene regulation. There was no overlap of allele categories introgressed in the two directions. Phenotypic experiments documented a fitness increase in H. annosum genotypes characterized by introgression of alleles from the invasive species, supporting the hypothesis that hybridization results in putatively adaptive introgression. Conversely, introgression from the native into the exotic species appeared to be driven by selection on genes favoring genome stability. Since the introgression of specific alleles from the exotic H. irregulare into the native H. annosum increased the invasiveness of the latter species, we propose that two invasions may be co-occurring: the first one by genotypes of the exotic species, and the second one by alleles belonging to the exotic species. Given that H. irregulare represents a threat to European forests, monitoring programs need to track not only exotic genotypes in native forest stands, but also exotic alleles introgressed in native genotypes.

A Trait-Based Protocol for the Biological Control of Invasive Exotic Plant Species

Selecting appropriate native species for the biological control of invasive exotic plants is a recurring challenge for conservationists, ecologists, and land managers. Recently developed trait-based approaches may be an effective means of overcoming this challenge. However, we lack a protocol and software platform that can be used to quickly and effectively select potential native plant species for performing biological control of the invasive exotic plant species. Here, our study introduces a protocol and a software program that can be used for trait-based selection of appropriate native plant species for performing biocontrol of invasive exotic plant species. In particular, we illustrate the effectiveness of this software program and protocol by identifying native species that can be used for the biological control of Leucaena leucocephala (Lam.) de Wit, a highly invasive plant species found in many parts of the world. Bougainvillea spectabilis was the only native species selected by our software program as a potential biocontrol agent for L. leucocephala. When separately planting 4 seedlings of B. spectabilis and two unselected species (Bombax ceiba, and Ficus microcarpa) as neighbors of each individual of L. leucocephala for 3 years, we found that B. spectabilis, which was functionally similar to the invasive L. leucocephala, significantly limited the invasion of the latter, while the unselected native plant species could not. That was because all the seedling of B. spectabilis survived, while half seedlings of unselected species (B. ceiba and F. microcarpa) died, during the experimental period when planted with L. leucocephala seedlings. Moreover, the growth of L. leucocephala was restricted when planted with B. spectabilis, in contrast B. ceiba and F. microcarpa did not influence the growth of L. leucocephala. Overall, our software program and protocol can quickly and efficiently select native plant species for use in the biological control of invasive exotic plant species. We expect that this work will provide a general protocol to perform biological control of many different types of invasive exotic plant species.

Rhaponticum repens (Russian knapweed).

R. repens is a deep rooted perennial that is native to Eurasia. It was accidentally introduced into North America as a contaminant of seed and spread rapidly. R. repens can be a serious crop pest in its native range and elsewhere. It forms large monotypic stands that reduce diversity and degrade forage quality on rangelands. As it is allelopathic and survives under a variety of conditions, it has been become an invasive exotic wherever it is imported. It has been declared a noxious weed in 18 US states (USDA-NRCS, 2016) and four Canadian provinces (Rice, 2003).