Invasive Species Removal Promotes Habitat Restoration but Does Not Immediately Improve the Condition of a Threatened Plant Subspecies

Impacts of invasive species on rare species are relevant to conservation. We studied the response of Leedy’s roseroot Rhodiola integrifolia subsp. leedyi, a subspecies listed as threatened under the Endangered Species Act, to removal of the invasive species Japanese knotweed Fallopia japonica. Japanese knotweed has invaded the largest known population of Leedy’s roseroot, affecting about 10% of all Leedy’s roseroot in the world. Japanese knotweed shaded Leedy’s roseroot, but the two did not share belowground resources because of their position on cliffs. To study this interaction and, ultimately, to restore Leedy’s roseroot habitat to an open, high-light condition, we removed Japanese knotweed in a three-treatment block design. We measured Leedy’s roseroot abundance, growth, and reproduction in treatment blocks and in uninvaded areas before and after treatment. Compared with uninvaded areas, Japanese knotweed invasion negatively affected Leedy’s roseroot abundance, growth, and reproduction. Light interception by Japanese knotweed degraded the habitat for Leedy’s roseroot. Herbicide removal of Japanese knotweed resulted in increased light and temperature compared with untreated invaded plots but did not affect Leedy’s roseroot abundance, growth, or reproduction over the 2 y of our study. These results show that invasive species removal is conducive to restoring Leedy’s roseroot habitat, but recovery in the subspecies may lag behind restoration of the habitat, suggesting that additional action or time may be required to restore preinvasion performance of Leedy’s roseroot. Results of this study may inform restoration efforts for other systems and contribute to the literature on interspecific interactions

Recovery of Forest Floor Diversity After Removal of the Nonnative, Invasive Plant Euonymus fortunei

The vine Euonymus fortunei (Turcz.) Hand.-Mazz. is invading forests of the eastern United States; as a result, removal of E. fortunei has become a priority of resource managers. This study examined the effectiveness of five techniques for eliminating E. fortunei, restoring plant species richness, and enhancing recolonization by woody species. In 2003, the following five treatments were applied: burn with a propane torch, light exclusion by plastic tarp, burn and glyphosate application, cut (simulated grazing) and glyphosate application, mow and glyphosate application, plus an untreated control. Each treatment was replicated four times in a randomized block design located in a heavily E. fortunei–invaded forest remnant in Lexington, KY. Vegetation was surveyed in 2004, 2005, 2006, 2007, and 2013. Across years, most treatments were associated with reduced E. fortunei cover and increased total species richness. Over time, E. fortunei cover increased across treatments, such that by 2013, no difference in E. fortunei cover was detectible among treatments. Some differences in total and native species richness among treatments were still perceptible by 2013. Increased E. fortunei cover was correlated with decreased ground-layer species richness, native species richness, sapling richness, and sapling density. Light exclusion by plastic tarp, a method absent from many management recommendations, was unique in its long-term reduction of E. fortunei cover and its association with increased total species richness, but use of plastic tarps may have drawbacks. This study quantified the long-term community effects of removing an established invasive species from a mature, urban forest. Removal allowed native plants, notably woody species, to reestablish. Because richness continues to decline as E. fortunei reinhabits plots, land managers seeking to conserve biodiversity under conditions similar to those within our study site should maintain proactive E. fortunei removal plans

Does habitat stability structure intraspecific genetic diversity? It’s complicated...

Regional phylogeographic studies have long been conducted in the southeastern United States for a variety of species. With some exceptions, many of these studies focus on single species or single clades of organisms, and those considering multiple species tend to focus on deep historical breaks causing differentiation. However, in many species more recent factors may be influencing genetic diversity. To understand the roles of historic and contemporary processes in structuring genetic diversity, we reanalyzed existing genetic data from Southeast of North America using approaches gleaned from phylogeographic and landscape genetic literature that were implemented across species including AMOVAs, PCoAs, Species Distribution Modelling, and tests of isolation by distance, environment, and habitat instability. Genetic variance was significantly partitioned by ecoregions, watersheds, and across phylogeographic breaks in the majority of species. Similarly, genetic variation was significantly associated with some combination of geographic or environmental distance or habitat instability in most species. Patterns of genetic variation were largely idiosyncratic across species. While habitat instability over time is significantly correlated with genetic diversity in some species, it appears generally less important than isolation by geographic or environmental distance. Our results suggest that many factors, both historical and contemporary, impact genetic diversity within a species, and more so, that these patterns aren’t always similar in closely related species. This supports the importance of species- specific factors and cautions against assumptions that closely related species will respond to historical and contemporary forces in similar ways

Identifying Abiotic and Biotic Factors Associated with Leedy's Roseroot (Rhodiola integrifolia subsp. leedyi (Rosend. & J.W. Moore) Kartesz) at Glenora Cliffs, Glenora, New York

Leedy’s roseroot (Rhodiola integrifolia subsp. leedyi) is a cliff-dwelling glacial relict federally-listed as threatened in the U.S. This research investigated abiotic and biotic factors correlated with Leedy’s roseroot at Glenora Cliffs, Glenora, NY. Results of censuses (2003-2015) showed decreased Leedy’s roseroot flowering in some sections of Glenora Cliffs. Abiotic factors correlated with Leedy’s roseroot occurrence included increased seepage, light, and summer temperatures, decreased weathering, and lower heights on the cliff. Analysis of the Glenora Cliffs community suggested Leedy’s roseroot co-occurs with other cliff-dwelling species. Experimental removal of Japanese knotweed (Fallopia japonica var. japonica) in a three-treatment block design revealed Japanese knotweed was associated with decreased flowering in Leedy’s roseroot. Herbicide removal of Japanese knotweed did not restore Leedy’s roseroot flowering, but was associated with increased temperature and light and shorter Leedy’s roseroot stems. Continued monitoring of Glenora Cliffs is recommended

Invasive Species Removal Promotes Habitat Restoration but Does Not Immediately Improve the Condition of a Threatened Plant Subspecies

Impacts of invasive species on rare species are relevant to conservation. We studied the response of Leedy’s roseroot Rhodiola integrifolia subsp. leedyi, a subspecies listed as threatened under the Endangered Species Act, to removal of the invasive species Japanese knotweed Fallopia japonica. Japanese knotweed has invaded the largest known population of Leedy’s roseroot, affecting about 10% of all Leedy’s roseroot in the world. Japanese knotweed shaded Leedy’s roseroot, but the two did not share belowground resources because of their position on cliffs. To study this interaction and, ultimately, to restore Leedy’s roseroot habitat to an open, high-light condition, we removed Japanese knotweed in a three-treatment block design. We measured Leedy’s roseroot abundance, growth, and reproduction in treatment blocks and in uninvaded areas before and after treatment. Compared with uninvaded areas, Japanese knotweed invasion negatively affected Leedy’s roseroot abundance, growth, and reproduction. Light interception by Japanese knotweed degraded the habitat for Leedy’s roseroot. Herbicide removal of Japanese knotweed resulted in increased light and temperature compared with untreated invaded plots but did not affect Leedy’s roseroot abundance, growth, or reproduction over the 2 y of our study. These results show that invasive species removal is conducive to restoring Leedy’s roseroot habitat, but recovery in the subspecies may lag behind restoration of the habitat, suggesting that additional action or time may be required to restore preinvasion performance of Leedy’s roseroot. Results of this study may inform restoration efforts for other systems and contribute to the literature on interspecific interactions

Genetic and Morphological Comparisons of Lesser Celandine (Ficaria verna) Invasions Suggest Regionally Widespread Sexual Reproduction

Both asexual and sexual reproduction can provide important keys to the success of invasive species. A species with potential for both is lesser celandine (Ficaria verna), a European native with multiple subspecies that have been introduced in North America as ornamentals and escaped cultivation. Asexual reproduction via bulbils is prolific in many introduced populations of lesser celandine, with sexual reproduction reportedly rare. Although genetic and morphological diversity of European celandine has been studied, few have examined invasive North American populations. We aimed to document introduced genotypic and phenotypic diversity at a regional scale. We first compared sequence-related amplified polymorphism (SRAP) genotypes of 64 individuals collected from Columbus, Cincinnati, and Cleveland, OH. In a second experiment, we phenotyped 129 individuals from the same regions and from Louisville, KY, measuring traits in an outdoor common garden experiment. The SRAP markers were highly polymorphic and revealed surprising genetic differentiation. Genetic and trait variation were both structured across regions, but we also saw high variation within regions. Cleveland populations differed the most genetically and morphologically. Nearly every individual made asexual bulbils, and many individuals that flowered produced expanded achenes. Trait data suggested subspecies verna or ficariiformis occur in these regions. Genetic admixture within regions and within individuals, along with achene expansion, suggests sexual reproduction may be widespread. Sexual and asexual propagules may spread by different vectors, and our resistance analyses indicated water dispersal and habitat availability contribute to genetic structure. These findings suggest that celandine has substantial potential for further spread and evolutionary change