Non-native Flora Research Articles

Non-native flora changes in rural gardens of China: the role of tourism

Human cultivation facilitates the naturalization and subsequent invasion of non-native plant species through, for example, protection from predators or reducing environmental stochasticity. With the development of tourism, non-native plant species have been increasingly introduced into rural home gardens for landscape greening and amenity planting. However, few studies have examined non-native flora in rural home gardens, and in particular the importance of tourism in determining changes of garden non-native flora has not been scrutinized. In this study, we investigated non-native plant species in 135 home gardens across five rural tourism villages in tropical China. Attributes related to garden or household characteristics were also collected through interviews and questionnaires. A distance-based redundancy analysis was then performed to reveal the relationships between the non-native species composition and garden attributes. A total of 338 non-native plant species were recorded in the surveyed gardens. Among them, the majority (63%) were ornamentals, whereas 19% were for nutritional uses and 12% were spontaneous weeds. Gardening preference and distance to tourist attractions governed the non-native compositions, with gardens preferring cultural (ornamental) cultivation or gardens close to tourist attractions having more non-native species. These results highlight an increasing role of tourism in promoting non-native cultivation in rural gardens. Recommendations for species risk assessment, trade and supply regulation, and proper garden management are provided to help harness plant invasion along tourism development in rural China and other regions around the world.

Patterns and changes in the Nonnative Flora of Franklin County, Massachusetts

Patterns and changes in the Nonnative Flora of Franklin County, Massachusetts

Effect of introduction pathways on the invasion success of non-native plants along environmental gradients

Our understanding on the role of introduction pathways on plant invasions is incomplete because their interaction with other factors remains poorly studied. We contributed to filling this knowledge gap, by analysing temporal trends in pathway importance, pathway-specific differences in the invaded niche, and the effect of pathways on invasion success. We used the non-native flora of Catalonia (NE Spain) as a study system. The contribution of pathways to the non-native flora interacted with time: from before 1500 to the present, gardening replaced agriculture as the main donor of new plants, while the contribution of unintentional introductions fluctuated without a consistent trend. Among neophytes (plants introduced after 1500), introduction pathways influenced differences mainly in habitat type, and secondarily in elevation: natural habitats and high elevation promoted invasion by gardening plants over unintentionally introduced ones. These nuances were unrelated to interactions between environmental variables. Among neophytes, invasion success was unrelated to pathways and interactions between pathways and traits, but was positively related to minimum residence time: older introductions achieved greater area of occupancy, habitat range, and invaded climatic niche breadth. Our results suggest that non-native plants diversified their niches over time (1500-present), a process that resulted in similar area of occupancy and niche breadth across plants with different introduction pathways. This was accompanied by pathway-specific nuances in the type of invaded environmental conditions.

The Infrastructures of Plant-Hunting

The acquisition of nonnative flora and fauna was long framed by horticultural historians as the result of great British derring-do and hand-to-hand conflict. Yet nineteenth-century plant extraction actually involved comparatively few feats of physical bravery or scenes of Boys’ Own high drama. The letters of Victorian commercial plant-hunters reveal that the removal and exportation of plants entailed the deployment of emerging colonial and national infrastructures together with complex regional and local networks and knowledge systems. Much of a plant-hunter's day-to-day life, tellingly, involved paperwork: submitting drafts and bills of exchange, sending letters and cables to employers, and completing bills of lading to ship plants, in stages, to Europe, where they were received at customs houses before journeying on, by rail and by road, to nurseries, collectors, and auction houses. At the same time, emerging colonial infrastructures only took hunters so far; local and traditional knowledge systems were essential as well. Plant-hunting depended upon the support, expertise, knowledge, and traditions of local people—a fact the enduring narrative of hand-to-hand conflict and triumphant British vanquishing seems structured carefully to conceal.

Genus Acacia in Mainland Portugal: Knowledge and Experience of Stakeholders in Their Management

The global rise in issues related to the invasion of alien tree species is becoming increasingly prominent. Genus Acacia is one of the most pervasive invaders among the non-native flora introduced to Portugal over the centuries. This research aimed to pinpoint the key players engaged in its management, their expertise, and the methodologies applied to control acacias or decrease affected regions. Data were gathered via an online survey and subjected to diverse statistical analyses. Numerous stakeholders have emerged in recent decades, employing various methods to fight acacia invasion. Mechanical, chemical, and combined methods are the most frequently applied. The findings highlight the need for continued funding for long-term acacia control in the same invaded areas, increased training actions and best practices demonstration in the field and increased public awareness and engagement in local communities and the general public.

Phylogenetic relationships of invasive plants are useful criteria for weed risk assessments

AbstractRisk assessments are conservation tools used to prevent the introduction of invasive species. Many assessments ask whether a taxon has invasive close relatives, but it is unclear whether this phylogenetic information is useful, and which taxonomic scales (e.g., genus, family) are most predictive of risk. Combining phylogenetic clustering analyses with models predicting invasion risk, we found invasive plants were clustered within nonnative flora of the conterminous United States. Taxonomic information in models improved their predictive capacity; invasion risk for taxa with invasive confamilials, congeners, or sister taxa increased by 9%, 16%, and 19% respectively. Phylogenetic information did not improve inference for species without any congeners, or those from large genera. The most common approach—assessing congeners—is well suited to identify invaders, particularly for genera with 2–10 established species. While existing phylogenetic information can enhance assessments of invasion risk, biologists and regulators should collaborate to improve nonnative species phylogenies.

Non-native vascular flora of alpine areas in the White Mountains, New Hampshire, USA

ABSTRACT Arctic-alpine vegetation in the eastern United States is unique to northern New England and New York and is disjunct from similar areas in eastern Canada. We present the first study of the non-native flora in the region, specifically focusing on New Hampshire’s White Mountains. By combining literature and herbaria searches, field surveys, and a seventeen-year evaluation at an alpine hut in a hypothesis-driven framework, we document the composition, chronology, and persistence of non-native plant species establishments, regress richness in relation to elevation and disturbed area, and evaluate similarities to nineteen other alpine floras globally. Our results indicate that the White Mountains support one of the most species-rich non-native alpine floras known in the world, with 58 species detected at thirty-one sites since 1874, comprising 19 percent of 300 species documented in New Hampshire’s 22 km2 of alpine tundra. There is a negative relationship between non-native alpine plant richness and elevation along a mountain road on Mt. Washington. Moreover, elevation predicts richness per unit area in proximity to clusters of built structures in alpine areas. The compositions, geographic origins, and dominant ruderal strategies of non-native species are similar to those of Arctic and other alpine non-native floras globally. Sørenson similarity index and nonmetric multidimensional scaling ordination of twenty alpine regions reveals the White Mountains have highest similarity with widely separated mountain regions in Australia, Hawaii, the Rocky Mountains, the Andes, Southern Africa, and Iceland, driven by shared species of Eurasian origin. We report the unexpected discovery of Plagiobothrys hispidulus, a borage native to western North America not previously reported from New Hampshire. These findings have important implications for managers of alpine areas in eastern North America and may facilitate the early detection, monitoring, and control of non-native species, minimizing their establishment and spread.

Hidden cargo: The impact of historical shipping trade on the recent-past and contemporary non-native flora of northeastern United States.

Understanding establishment and spread of non-native plants is important in the face of a homogenizing global flora. While many studies focus on successful, invasive species, fewer have studied failed plant introductions. Until the early 1900s, large quantities of ship ballast, often containing foreign plant propagules, were deposited in New Jersey (USA). The resulting ballast flora is documented in extensive herbarium records, providing us a unique opportunity to analyze successes and failures of novel plant species introductions. We used digitized specimens from 75 herbaria to study 264 non-native species introduced into New Jersey through 19th century ballast deposition. We used spatial (density-based clustering; HDBSCAN) and temporal analyses of species retention and geographic spread to quantify disappearance rate, survival, and dispersion through time and define trajectory groups. Four distinct trajectory groups were identified: waif (only present during import; 32% of species), short-term (disappeared quickly; 20%), established-limited spread (survives locally, 30%), and established-widespread (widespread, 18%). Species disappearance rate was highest during ballast deposition and decreased soon after deposition stopped around 1900. Spatial patterns showed a strong association with 19th century railroads for inland dispersal from ports. The disappearance rate and spatial analyses are robust to herbarium collection bias. This study using New Jersey as a model is one of the few documenting multispecies successes and failures in inadvertent plant introductions. Results reveal distinct trends in species establishment and geographic spread and highlight the utility of herbarium specimens in answering questions that span large time scales.

Complex preference relationships between native and non-native angiosperms and foraging insect visitors in a suburban greenspace under field and laboratory conditions

The introduction and spread of non-native flora threatens native pollinators and plants. Non-native angiosperms can compete with native plants for pollinators, space, and other resources which can leave native bees without adequate nutritional or nesting resources, particularly specialist species. In the current study, we conducted flower preference experiments through field observations and controlled binary choice tests in an artificial arena to determine the impact of field vs. laboratory methods on flower preferences of native bees for native or non-native flowers within their foraging range. We conducted counts of insect pollinators foraging on the flowers of three plant species in a suburban green belt including one native (Arthropodium strictum) and two non-native (Arctotheca calendula and Taraxacum officinale) plant species. We then collected native halictid bees foraging on each of the three plant species and conducted controlled binary tests to determine their preferences for the flowers of native or non-native plant species. In the field counts, halictid bees visited the native plant significantly more than the non-native species. However, in the behavioural assays when comparing A. strictum vs. A. calendula, Lasioglossum (Chilalictus) lanarium (Family: Halictidae), bees significantly preferred the non-native species, regardless of their foraging history. When comparing A. strictum vs. T. officinale, bees only showed a preference for the non-native flower when it had been collected foraging on the flowers of that plant species immediately prior to the experiment; otherwise, they showed no flower preference. Our results highlight the influence that non-native angiosperms have on native pollinators and we discuss the complexities of the results and the possible reasons for different flower preferences under laboratory and field conditions.

The non-native flora of Redberry Lake Biosphere Reserve, Canada

A checklist of alien plants of Redberry Lake Biosphere Reserve in the province of Saskatchewan, Canada is presented for the first time. By way of field surveys and herbarium research, 121 alien taxa (22.1% of the regional flora) were recorded. The most species rich families are Poaceae (24 taxa, 19.8%) and Asteraceae (22, 18.2%). Species richness is about evenly distributed across genera with Rumex, Artemisia and Poa (each contains 3 taxa or 2.5%) making up those with the greatest number of species. Concerning plant growth habits, the two dominant groups are forbs (94 taxa, 77.7%) and graminoids (23 taxa, 19%). Regarding habitat preferences, most alien plants occur in natural and seminatural habitats (48 taxa, 39.7%), ruderal places (43 taxa, 35.5%) and agricultural lands (30 taxa, 24.8%). In relation to the state of spread, invasive (63 taxa, 52%) and naturalised (48 taxa, 39.7%) species prevail. In terms of geographical origin, most alien plants are native to Eurasia–Africa (49 taxa, 40.5%) and Eurasia (34 taxa, 28.1%). The biosphere reserve is increasingly being invaded by alien plants whose introduction and distributions can be explained by intense agricultural pressure which resulted in extensive habitat alteration and proliferation of invasive species. URL: https://www.upjs.sk/pracoviska/botanicka-zahrada/odborne-aktivity/contents-abstracts/

Integrating expert knowledge at regional and national scales improves impact assessments of non-native species

Knowledge of the impacts of invasive species is important for their management, prioritisation of control efforts and policy decisions. We investigated how British and Irish botanical experts assessed impacts at smaller scales in areas where they were familiar with the flora. Experts were asked to select the 10 plants that they considered were having the largest impacts in their areas. They also scored the local impacts of 10 plant species that had been previously scored to have the highest impacts at the scale of Great Britain. Impacts were scored using the modified classification scheme of the EICAT framework (Environmental Impact Classification for Alien Taxa). A total of 782 species/score combinations were received, of which 123 were non-native plants in 86 recording areas. Impatiens glandulifera, Reynoutria japonica and Rhododendron ponticum were the three species considered to have the highest impacts across all regions. Four of the species included in the list of the 10 highest impact species in Great Britain were also in the top 10 of species reported in our study. Species in the higher impact categories had, on average, a wider distribution than species with impacts categorised at lower levels. The main habitat types affected were woodlands, followed by linear/boundary features and freshwater habitats. Thirty-nine native plant species were reported to be negatively affected. In comparison to the overall non-native flora of Britain and Ireland, the lifeform spectrum of the species reported was significantly different, with higher percentages of aquatic plants and trees, but a lower proportion of annuals. The study demonstrates the value of local knowledge and expertise in identifying invasive species with negative impacts on the environment. Local knowledge is useful to both confirm national assessments and to identify species and impacts on native species and habitats that may not have gained national attention.

The naturalization of the almond Prunus dulcis in different ecological contexts in the Mediterranean: An underestimated process?

Although Prunus dulcis has been frequently listed in non-native floras all around the world, its naturalization has been rarely studied in the field. Probably, because this species has generally invaded synanthropic habitats. We assessed the density of natural regeneration of almond, biometric parameters (height and basal stem diameter), and the distribution in life stage classes in three different ecological contexts in Sicily (Mediterranean Italy): one natural habitat (maquis), one pine afforestation and two prickly pear orchards. We recorded 236 naturally regenerating almond individuals, with density ranging from 140 individuals per hectare (prickly pear orchard 1) up to 2,400 individuals per hectare (pine afforestation). Despite the higher density, almond individuals presented the lowest height and basal stem diameter under pine afforestation, suggesting a more recent establishment. Reproductive individuals were dominant (67.8%), followed by pre-reproductive (22.1%), and juveniles (10.1%). Although the naturalization of the almond in Mediterranean contexts is not new, in the last two decades there is evidence of an increasing trend. Most importantly, for the first time, we found the almond thriving within a natural habitat in large areas covered by Mediterranean maquis. Since the almond appears to be perfectly integrated within local plant communities, the origin and meaning of this peculiar vegetation aspect deserve to be further deepened.

New Zealand's non-native flora – friends or foes?

New Zealand is acutely aware of the threats posed by invasive non-native plants. Nonnative species make up nearly ninety percent of the country's flora. Succulents, numbering over a hundred, constitute a relatively small proportion of the total. Most, if not all, of the country's non-native succulents are a consequence of introduction, escape from cultivation or careless disposal. Carpobrotus edulis and its hybrids pose a threat to native flora. The poisonous Cotyledon orbiculata poses a threat to livestock. These two species are controlled, to some extent, by restrictions on sale and distribution. Conservation measures, other than those applied to these species, are limited. The conservation authorities in New Zealand should be alert of the potential threats from some other succulent plants, especially at local level.

New records of Asteraceae for the non-native flora of Tunisia and north Africa with some nomenclatural remarks

Sixteen new Asteraceae are added to the non-indigenous flora of Tunisia. Six of them (Dimorphotheca ecklonis, Gaillardia pulchella, Gazania linearis var. linearis, Guizotia abyssinica, Rudbeckia triloba and Tithonia diversifolia) are also new for the flora of North Africa. Chrysanthemum morifolium is here first reported for the Mediterranean Basin. Seven genera (Argyranthemum, Bidens, Dimorphotheca, Gaillardia, Guizotia, Rudbeckia and Tithonia) are recorded for the first time for the vascular flora of Tunisia. Most of these species escaped from gardens and pots and became casual along roadsides and/or disturbed areas after cypsela dispersion (except for Chrysanthemum morifolium). Some species, even though appearing to be well established locally and are potentially invasive at a worldwide level, still do not behave so in Tunisia. In addition to the floristic notes, the typification of the names Dimorphotheca ecklonis, Gorteria linearis and Mirasolia diversifolia are discussed.

Tropical islands of the Anthropocene: Deep histories of anthropogenic terrestrial–marine entanglement in the Pacific and Caribbean

Islands are useful model systems for examining human–environmental interactions. While many anthropogenic effects visible in the archaeological and paleoecological records are terrestrial in nature (e.g., clearance of tropical forests for agriculture and settlement; introduction of nonnative flora and fauna), native peoples also relied heavily on marine environments for their subsistence and livelihood. Here we use two island case studies—Palau (Micronesia) and the Lesser Antilles (Caribbean)—and approach their long-term settlement history through a “ridge-to-reef” perspective to assess the role that human activity played in land- and seascape change over deep time. In particular, we examine the entanglement of terrestrial and marine ecosystems resulting from anthropogenic effects and cultural responses to socio-environmental feedback. We suggest that on the humanized tropical islands of the Anthropocene, mangroves, near shore and littoral areas, and coral reefs were major sites of terrestrial–marine interface chronicling and modulating anthropogenic effects.

Semi-desert fruit farms harbor more native flora than Mediterranean climate farms in central Chile

Understanding the factors that affect native plant communities is essential to protect floristic diversity, particularly in Mediterranean agroecosystems. The Chilean Mediterranean-climate area supports high species richness and levels of endemism, and harbors the main fruit production. We investigated whether the richness of native and non-native flora differs between two Mediterranean climate areas of Chile with contrasting rainfall levels in both cultivated and uncultivated habitats. Thirteen fruit farms under conventional management were prospected in the spring of 2015 and of 2016 by sampling in square meter quadrants (N = 3,630). A total of 191 vascular plants were found, 48.2 % of them native, 50.3 % non-native and 1.6 % not identified. Species richness was low in both areas and habitat types. However, there were more native species in uncultivated habitats in the Mediterranean-to-desert transition area than in the mesic Mediterranean area, and the contrary was observed for non-native species. Our results suggest that wetter Mediterranean climate areas are more prone to the establishment of non-native plant species.

Time since first record and population density influence range sizes of non-native plants, but also of native plants, in a chronically overgrazed island

Background and aims − Humans are increasingly introducing species to new regions. It is necessary to understand the processes that drive the expansion of non-native species into these new habitats across multiple spatiotemporal scales.Material and methods − We studied the spatial distribution of the non-native flora (39 species) of Guadalupe Island (246 km2) in the Mexican Pacific. We analyzed how residence time (time since first report in historical sources, 1875–2004) and species attributes (population density, flowering phenology, and individual height) are related with range sizes of non-native plants. To test whether the residence time – range size relationship of non-native plants can result from other factors besides time since their arrival, we compared it to the residence time – range size relationship of native plants. Range sizes were obtained using herbarium data and a systematic field sampling of 110 transects (50 × 2 m) throughout the entire island. We used beta regression to analyze the relationship of range sizes with residence time and species attributes.Key results − Range sizes of non-natives showed a positive relationship with residence time, flower phenology, and notably with plant density, but not with individual height. However, similar relationships were found for native species, casting doubts on whether our results reflect the range expansion rates of non-native species. Conclusions − Our results suggest that the production of large numbers of propagules, both as a result of long reproductive periods and large population sizes, determines to a large extent the rates of range size expansion of non-native species. However, the relationship we found between time since discovery and range size may arise from sampling biases, biological processes, or – most likely – both. This highlights the need for new approaches that allow us to discern the relative contributions of bias and process in our study of non-native species expansion.

Plant naturalization trends reflect socioeconomic history and show a high likelihood of inter-island spread in Hawai‘i

AbstractThe composition of nonnative floras is influenced by a region’s socioeconomic history, yet rarely are these factors studied alongside plant naturalization rates over time. Such information is especially critical for archipelagos, which often host large numbers of nonnative plants and would benefit from prevention of inter-island spread. We compiled the first record of occurrence and first record of naturalization for all naturalized plants in Hawai‘i alongside data on their origin, native climate types, taxonomy, and likely introduction pathway and compared rates of naturalization with socioeconomic trends. We found that the rate of total plant naturalizations has increased at a roughly constant rate during the past century without any sign of plateauing. However, this relatively steady increase is underlain by notable fluctuations in naturalization rates for different introduction pathways, with ornamentals increasing recently, while agriculture-related plants have decreased. Furthermore, this trend mirrors a shift from an agriculture-dominated economy to a tourism-based one associated with increases in both resident and tourist populations as well as general economic well-being. We further found that the average naturalized species spreads at a rate of 1.86 islands per decade, eventually occupying most major islands in the archipelago, and the rate of spread appears to be increasing since Hawai‘i’s economic shift. Our findings also emphasize the diversity of Hawai‘i’s nonnative flora, which originates from a variety of climates, continents, and taxonomic groups. We demonstrated that many nonnative species have native ranges that include temperate climates, which is important, because these climates typically co-occur with higher-elevation, remnant patches of native-dominated ecosystems in Hawai‘i. This study reveals trends that may help predict a species’ ability to naturalize and spread within and between islands, and we discuss management implications that may be extended to other regions.

Impact of Parthenium hysterophorus L. invasion on soil nitrogen dynamics of grassland vegetation of Indo-Gangetic plains, India.

The noxious plant species Parthenium hysterophorus L. has become a major concern for the conservation of many natural and managed areas. The species is known for its various adverse effects on the invaded ecosystems, particularly in terms of biodiversity loss. Currently, P. hysterophorus is a leading invasive species widespread in the grasslands of productive and diversity rich Indo-Gangetic plains of India and is responsible for various changes in the ecosystem. The present study addresses the changes that P. hysterophorus can bring in the vegetation structure (species richness, species evenness, and species composition) of the grasslands of Indo-Gangetic plain. To broaden our understanding of the invasion success and facilitated expansion, we also focus on the variability of soil nitrogen pool and processes as a consequence of invasion. We report that in the presence of P. hysterophorus, the species diversity, evenness, composition and richness were altered, affecting many native and non-native flora of the ecosystem. The effect was more prominent during the second and third year of the study with more increase in the invasion outcomes. Significant changes in soil nitrogen (N) dynamics, particularly, increased available (N), N-mineralization and microbial biomass N have been found in the invaded plots along with changes in vegetation of the grassland community. Overall, the result suggested that the invasive species, P. hysterophorus, modifies the soil and this modification is correlated with changes in vegetation structure and this situation is likely to further facilitate severe alterations in the ecosystem and could favor encroachment of other non-native species in the area.

Further species within Arecaceae (Palmae; Coryphoideae) to non-native flora of Tunisia and North Africa

Abstract Five new alien taxa are here recorded from Tunisia. Reported taxa (Livistona chinensis, Phoenix canariensis, P. reclinata, P. theophrasti and Washingtonia robusta) belong to the subfamily Coryphoideae (Arecaceae). Updated nomenclature, brief descriptions, general and national distributions are provided for each species. Livistona chinensis and Phoenix theophrasti are here reported for the first time in North Africa. Identification keys are also provided.