Impact of invasive plant species on the livelihoods of farming households: evidence from Parthenium hysterophorus invasion in rural Punjab, Pakistan

Impact of Parthenium hysterophorus L. on floristic diversity in Dhauladhar foothills of Himachal Pradesh

Parthenium hysterophorus L. has become a weed of global concern owing to its fast expansion and invasive character. In order to study the status of this noxious weed and its impact on floristic diversity in Dhauladhar foothills, the study was conducted during the year 2021-2022 in culturable wastelands of Dhauladhar ranges in Kangra district of Himachal Pradesh, India. The impact of Parthenium hysterophorus L. on associated species at different altitudes and aspects was observed. Our observations depicted that Parthenium hysterophorus L. has been growing more vigorously in the northern aspect than the southern aspect with the density of 37.78 m-2 and 21.62 m-2, respectively. The highest density of this noxious weed was recorded in the altitudinal range of 600-1200 m (34.32 m-2) while it was not observed beyond 1805 m above sea level. The invasion of Parthenium hysterophorus L. significantly affected the plant density of other species. The descending order of the species as per dominance was observed as Cynodon dactylon, Trifolium repens, Oxalis latifolia, Parthenium hysterophorus L., and Ageratum houstonianum. The average number of species and species density were observed more in non-invaded sites (9.35 and 27.67 m-2) than in invaded sites (7.10 and 20.60 m-2). Species abundance and plant cover were observed more in non-invaded sites (28.73 and 657.90 m2 ha-1) than in invaded sites (22.70 and 322.30 m2 ha-1). Species diversity, richness, and evenness were reported to decline in invaded sites (1.56, 0.95, and 0.81, respectively) with respect to the non-invaded sites (1.94, 1.16, and 0.88, respectively). The study highlights the significant concerns associated with the invasive weed within the plant communities. Understanding its invasive status holds considerable implications for local afforestation initiatives, forest management strategies, and conservation policies. Furthermore, this investigation lays a foundational groundwork for implementing effective measures to get rid of this alien weed.

Microplastics meet invasive plants: Unraveling the ecological hazards to agroecosystems

The objective of this study was to assess the combined impact of environmental microplastic pollution and biological invasion which represent critical global eco-environmental challenges. The invasion of Solidago canadensis L. and soil microplastic contamination in the agroecosystem pose severe hazards to soil and plant ecology and human health. Oryza sativa L. (rice) was examined after individual and combined exposure to Solidago canadensis L. invasion (SI) and soil polyethylene microplastic contamination (MPc). Comparing the individual and combination treatments to the control, leaf biomass decreased, with varying changes in carbon, nitrogen, and phosphorus. Antioxidant enzyme activity and reactive oxygen species levels were significantly reduced following SI exposure and increased following the combined treatment (SI × MP). In contrast, ascorbate peroxidase and catalase activities were reduced after the combined treatment. Due to the confluence of various abiotic stressors, the combined treatment had a higher impact on leaf metabolites than the singular SI and MPc treatments. However, in comparison, the combined treatment significantly influenced the metabolic profile. In conclusion, the interaction between SI and MPc resulted in significant metabolic alterations. These changes were characterized by shifts in metabolite pools influenced by antioxidant enzyme activities and nutrient content, ultimately enhancing defense mechanisms within rice crops. Consequently, these stressors threaten the food safety, sustainability, and agricultural output of crops. The co-exposure of invasive plants and microplastics sheds light on the bio-ecological risks associated with microplastics in staple foods and offers valuable insights into the phytotoxicity of invasive plants in the presence of polyethylene microplastics.

Public Health Implications of Invasive Plants: A Scientometric Study

Movements of organisms through distinct places can change the dynamics of ecological interactions and make the habitat conducive to the spread of diseases. Faced with a cyclical scenario of invasions and threats in a One Health context, we conducted a scientometric study to understand how disturbances in environments with invaded vegetation affect the incidence of parasites and disease prevalence rates. The search was carried out in Web of Science and Scopus databases, with keywords delimited by Boolean operators and based on the PRISMA protocol. Thirty-sixarticles were full-read to clarify the interaction between diseases and invaded areas. The analysis covered publications from 2005 to 2022, with a considerable increase in the last ten years and a significant participation of the USA on the world stage. Trends were found in scientific activities, and we explored how invasive species can indirectly damage health, as higher concentrations of pathogens, vectors, and hosts were related to structurally altered communities. This paper reveals invaded plants threats that enhance disease transmission risks. It is likely that, with frequent growth in the number of introduced species worldwide due to environmental disturbances and human interventions, the negative implications will be intensified in the coming years.

Combined Inhibitory Effect of Canada Goldenrod Invasion and Soil Microplastics on Rice Growth

Alien plant invasion and residual soil microplastics (MPs) are growing threats to agricultural crop production. This study determined the adverse effects of Canadian goldenrod (Solidago canadensis L.) invasion and residual soil MPs on rice growth and development. The biomass, phenological indices, photosynthetic parameters, and antioxidant enzyme activities of rice were measured on the 50th and 80th day of post-plantation. Biomass and phenotypic results indicated the more harmful effects of the combination of S. canadensis invasion and residual soil MPs compared to S. canadensis invasion or residual soil MPs effects alone. Moreover, the interaction effect of S. canadensis invasion and residual soil MPs markedly reduced the ascorbate peroxidase and catalase belowground, while they increased in the aboveground parts of the rice. However, the S. canadensis invasion and residual soil MPs interactive treatments lowered the superoxide dismutase concentrations in the belowground parts of the rice plants while elevating the peroxidase and reactive oxygen species concentrations in both the belowground and aboveground parts compared to the other treatments. Among all treatments, S. canadensis invasion alone had the most negligible negative impact on rice biomass and growth indices. Our study suggests that soil MPs could negatively affect crop production with invasive alien plants, and the combined effects were more harmful than either of the single factors. Our findings will lay the groundwork for analyzing the impacts of invasive alien plants on rice crops.

Eco-friendly management of Parthenium hysterophorus

In sub-Saharan Africa, the invasive plant Parthenium hysterophorus (Parthenium) is threatening ecosystem integrity, biodiversity, and smallholder livelihoods. But, there is no single effective method of controlling it. Desmodium intortum, Lablab purpureus, and Medicago sativa were tested for their capacity to suppress Parthenium, as well as the allelopathic potential of Desmodium uncinatum leaf crude (DuLc) extract. While the study investigated the effect of DuLc extract concentrations on seed germination and seedling growth in laboratory, pot, field plot, it also assessed the effect of selected suppressive plants on Parthenium growth. It was found that high levels of DuLc concentrations and suppressive plants inhibited Parthenium germination and growth. When Parthenium was grown with suppressive plants, its growth was inhibited compared to when it was grown alone. When grown with all three test plants, the stem height and total fresh biomass of Parthenium seedlings were lowered by more than 60% and 59% in pots, and 40% and 45% in plots, respectively. Parthenium seed germination was decreased by 57% in plots, 60% in pots, and 73% in petri dishes at higher DuLc concentrations (i.e. 75% and 100%). Parthenium seedling stem heights were 36% (in plots) and 30% (in pots) shorter when sprayed with higher concentrations of DuLc. Overall, the findings of this study suggest that suppressive plants and those containing allelochemicals can be employed as a management tool to combat Parthenium invasion in sub-Saharan Africa, notably in Tanzania.

Parapatric Genetic Lineages Persist in a Multiply Introduced Non-native Bush-Cricket

To understand colonization success of an invasive species we need to know the origin of the founders, where and when they were introduced, and how they spread from the introduction site(s) through the landscape. Admixture of different genetic lineages from multiple introductions is generally hypothesized to be beneficial to invasive species thanks to adaptive variation and heterozygosity-fitness correlations. In this study, population genetic and landscape data was gathered for Roesel’s bush-cricket, Roeseliana roeselii a small bush-cricket common in central and eastern Europe that currently is expanding its range in northern Europe. We examined how colonization history and landscape structure affect the spread of the species and its population genetic structure, as a consequence of multiple introductions. Using comprehensive information of the species ecology and dispersal, together with genetic structure inferred from samples from 29 locations in central Sweden (we employed data published by Preuss et al., 2015), we found that two parapatric founding lineages have coexisted with very little gene flow during a long time span. An isolation-by-distance pattern and a decrease of genetic diversity toward marginal areas were more pronounced in the lineage situated in forest dominated landscapes. Our findings are in strong contrast to the hypothesis that different genetic lineages will admix when introduced to the same area. The presence of the separate lineages decades after introduction and without physical barriers for gene flow shows that some mechanism prevents them from admixture. One possibility is that the lineages with different genetic setups have adapted independently to local conditions and their admixture resulted in loss of locally adapted genotypes and hybrid offspring, less viable than the respective ancestral genotypes. However, an alternative post-mating reproductive barrier and hybrid breakdown phenomenon should also be considered. Our data indicate that besides landscape characteristics, human transportation of agricultural goods may play an important role for the overall spatial genetic pattern of the species in the study area by aiding the spread of the species.

The Host Range and Risk Assessment of the Stem-Boring Weevil, Listronotus setosipennis (Coleoptera: Curculionidae) Proposed for the Biological Control of Parthenium hysterophorus (Asteraceae) in Pakistan

Parthenium, or Parthenium hysterophorus, has extended its range in Pakistan throughout Punjab and into Khyber Pakhtunkhwa, the Federally Administrated Tribal Areas, Azad Jammu and Kashmir, and Sindh Provinces. Without control measures against parthenium, the negative impacts of this weed will go unchecked having deleterious effects on native biodiversity, human and animal health, as well as crop productivity. The weevil Listronotus setosipennis was obtained and imported from the Plant Health and Protection of the Agricultural Research Council (ARC-PHP), in Cedara, South Africa, in April 2019. A total of 22 plant species or cultivars in the Asteraceae family were assessed during no-choice oviposition tests in Pakistan. During these tests, the only plant species accepted for oviposition were the 10 cultivars of Helianthus annuus that are grown in Pakistan. All cultivars were thus tested for development of L. setosipennis from egg to adult. Only three cultivars were able to support some larval development, but at such low levels that it is unlikely to be the basis of a viable population. To support this, a risk assessment was conducted to ascertain the probability of L. setosipennis being able to sustain viable populations in the field, the results of which concur with native (Argentina) and introduced (Australia) field host-range information where L. setosipennis has never been recorded as a pest of sunflowers. The results of laboratory-based host-range trials, together with host records from its native and introduced range, indicate that L. setosipennis is sufficiently specific to parthenium and is thus suitable for release in Pakistan.

Quantifying the social and economic benefits of the biological control of invasive alien plants in natural ecosystems

Invasive alien plants reduce ecosystem service delivery, resulting in environmental, economic and social costs. Here we review the returns on investment from biological control of alien plants that invade natural ecosystems. Quantifying the economic benefits of biological control requires estimates of the reductions in ecosystem goods and services arising from invasion. It also requires post-release monitoring to assess whether biological control can restore them, and conversion of these estimates to monetary values, which has seldom been done. Past studies, mainly from Australia and South Africa, indicate that biological control delivers positive and substantial returns on investment, with benefit:cost ratios ranging from 8:1 to over 3000:1. Recent studies are rare, but they confirm that successful biological control delivers attractive returns on investment, which increase over time as the value of avoided impacts accumulates.