Impact Of Alien Species Research Articles

The old and the new on threats to high-mountain lakes in the Alps: A comprehensive examination with future research directions

The high-mountain lakes of the Alps, perched like glistening gems in the cradle of Europe’s most formidable mountain range, have for generations epitomized nature’s majesty. These remote and pristine bodies of water have served as invaluable sentinels of global change, repositories of geological history, and sources of freshwater for the surrounding regions. Yet, despite their seemingly imperturbable beauty and seclusion, these high-mountain lakes are not immune to the evolving forces of our changing world. Re-emerging threats, exacerbated by the relentless march of climate change and intensified human activities, cast a shadow over their future, posing profound challenges that demand our attention. The aim of this perspective is to shed light on the main emerging threats, raise awareness, and advocate for proactive actions aimed at preserving and protecting high-mountain lakes. These threats include climate change, retreat of glaciers, UV radiation, long-range transport of contaminants, impact of alien species and water usage for Alpine storage power stations. Additionally, increased tourism and recreational activities in these pristine environments can cause habitat disturbance, further endangering these unique ecosystems. The present perspective article also offers valuable perspectives on the necessity of monitoring and research efforts in high-mountain lakes. Such actions are crucial for comprehending the ecological well-being of these ecosystems, evaluating the consequences of environmental shifts, and devising successful conservation strategies.

Intraspecific variation of invaded pollination networks – the role of pollen-transport, pollen-transfer and different levels of biological organization

•Pollination networks have long been studied by quantifying plant-flower visitor species interactions. Despite making considerable contributions, this ignores important steps of pollen movement from anthers to receptive stigmas and neglects the intraspecific variation of the interacting partners. Addressing specialization and niche partitioning regarding heterospecific pollen transport and transfer, is fundamental to untangle the mechanisms behind contrasts seen in the impact of alien species on native communities.•We used two well-sampled datasets on pollen-transport and pollen-transfer networks to test how intraspecific variation in interaction specialisation affects invaded pollination networks. We considered different levels of biological organization: from species- to individual-based networks.•We found significant intraspecific variation in the pollen loads and pollen deposition of the invasive plant Impatiens glandulifera; thus only a few individual pollinators and plant stigmas carried large amounts of alien pollen grains, potentially functioning as super-spreaders driving the invading process. Consequently, most individuals carried only a few, or no alien pollen at all, possibly buffering the negative effects of invasive plants at the population and community levels.•Node and structural specialization were higher for individual-based and pollen-transfer networks, suggesting a lack of dominant, highly generalist links when downscaling from pollen-transport to pollen-transfer, and from species to individual-based networks.•The high specialization, selectiveness and niche partitioning of plants, pollinators and their interaction revealed at the different stages of the pollination process and across distinct levels of biological organization, suggest important mechanisms associated with the (re) organization of population niches. Moreover, these mechanisms provide a promising approach towards a more comprehensive understanding of the dynamics of invasion biology from population to community and ecosystem functioning.

Global distribution and richness of terrestrial mammals in tidal marshes

AbstractAimUnderstanding the determinants of species distribution and richness is key to explaining global ecological patterns. We examined the current knowledge about terrestrial mammals in tidal marshes and evaluated whether species richness increased with the marsh surface area and/or with their proximity to the equator and whether species distribution ranges decreased with latitude.LocationGlobal.MethodsWe reviewed the existing literature on terrestrial mammals in tidal marshes. We examined their ecological characteristics (e.g. habitat specialists, native or alien), predicted their variation in species richness and range size along latitude, and explored factors, such as surface area, underlying the global patterns found.ResultsWe found 962 records, describing 125 mammalian species using tidal marshes worldwide, also including several alien species. Most species (95%) were not marsh specialized, and some (18%) were of conservation concern. There were information gaps in South America, Africa, Australia and Asia, and a lack of information about mammalian ecological roles worldwide. We found that species richness increased with surface area, and showed a bimodal pattern peaked between 40° and 50° latitude in each hemisphere. We found no relationship between latitude and species range size.Main conclusionsOur worldwide findings revealed a broader range of tidal marshes inhabited by terrestrial mammals, and higher values of species richness than previously reported. The bimodal pattern of species richness was consistent with the species–area hypothesis, but it also suggested that further studies of species distribution in relation to historical and environmental factors will yield significant insights about variables driving richness in tidal marshes. Despite terrestrial mammal ubiquitous distribution in these ecosystems, there are considerable geographic gaps as regards knowledge about their functional importance and the impact of alien species on tidal marsh functioning. Consequently, extending our research efforts is key to planning the conservation of these coastal ecosystems.

Assessment and impact of alien species - Mimosa invisa L. on the biodiversity and pattern of vegetation at Dhoni hills, Western Ghats of Palakkad, Kerala-A case study

Mimosa invisa is a widely adapted weed from tropical America that has invaded the Dhoni hills of Palakkad District, Kerala. They were established as monocultures in grasslands, agricultural fields, plantations and forest areas of Palakkad, causing threats to other species. In this juncture, the present study was conducted to evaluate the impact of Mimosa invisa on the natural biodiversity and floristic compositions of native species of Dhoni hills, Palakkad. Vegetation analysis was carried out using random-systematic design and gradient methods, including the importance value index, species richness, dominance index, diversity, similarity and dissimilarity index, using standard protocols, followed by soil parameters such as pH and nutrient content and phenols in the invaded and uninvaded areas. It was noticed that in the Mimosa invaded area, the mean species number and the α diversity declined by 32.10% and 41.21%, respectively. Similarly, fresh and dry plant weight displayed remarkable variation (decreased by 35.9 and 49.9%, respectively) in the intruded zones. Out of 135 species recorded, 63 species were common in the control and intruded zones. Eleven species were growing exclusively in the invaded areas. The total phenolic content was 45%, the ion conductivity was 32%, the % of organic carbon and organic matter was 51%, the nitrogen content was 55.7%, and the phosphorus, potassium and sodium contents were 48, 38.5 and 24.4%, respectively, in the invaded soil compared to the control. Similarly, the calcium, magnesium and chloride contents were increased by 38.4, 30.6 and 33.5% respectively. Hence, it could be concluded that the invasion of M. invisa drastically affected the productivity and diversity of the invaded areas in the Dhoni hills of Palakkad.

A classification system for predicting invasiveness using climatic niche traits and global distribution models: application to alien plant species in Chile

Functional traits that predict plant invasiveness are a central issue in invasion ecology. However, in many cases they are difficult to determine, especially for a large set of species. Climatic niche traits can overcome this problem due to the ease of acquiring them for a large number of species. This effort is critical given that knowledge of species invasiveness is necessary (although not sufficient) to anticipate/manage invasive species. In this study, we examined thermal and hydric niche traits to predict plant invasiveness. We used a set of 49 alien plant species, representative of the alien flora of Chile. Niche traits were obtained using environmental information (WorldClim) and global occurrences. Invasiveness was estimated using global niche models and projection of the potential distribution in Chile. As a final step, we reviewed the literature for a subset of species, documenting their impacts on a) biodiversity, b) crop agriculture and c) livestock. Thermal niche breadth and thermal niche position were the most important niche traits to predict potential distribution (a proxy of invasiveness). Using thermal niche breadth and niche position traits, we constructed a graphical model that classifies alien species as highly invasive (wide thermal niche breadth and low niche position) or low potential to be invasive (narrow niche breadth and high niche position). We also found no association between our invasiveness classification and the documented impact of alien species.

Impact of alien species on species composition, floristic and functional diversity of aquatic and terrestrial ecosystems

Biotic homogenization is a major component of current biodiversity crisis involving increase in floristic, functional and genetic similarity of biotas resulting from species invasions and extirpations. Since habitat type is a good predictor of success of biological invasion at local scale, we studied distribution and abundance of native and alien plant species in eight habitat types namely lakes, wetlands, riparian, roadsides, orchards, grasslands, scrubs, and forests (06 sites each giving a total of 48 sites). For estimating taxonomic homogenization index, we calculated Jaccard’s similarity index separately for native, alien and alien + native species. We also calculated functional α, β, and γ diversity for three functional traits in three different ways i.e. with all species included, with only native species included and with only alien species included. We observed that habitats differ with respect to functional and floristic diversity. Aquatic habitats (species poor) were found to be more homogenous (average βA = 0.58) than terrestrial habitats (average βA = 0.68) with man-managed habitats (orchards) being taxonomically (average βA = 0.59) and functionally (FβA = 0.04) most homogenous among terrestrial habitats. Present study revealed that traits of alien plant species play an important role in determining the homogenization potential as invasives (in comparison to naturalized and casuals), perennials (in comparison to annual/biennials), herbaceous (in comparison to shrubs/sub-shrubs/lianas and trees) and submerged plants (in comparison to free floating, rooted floating and emergents) were found more homogenizing. These observations are crucial in understanding the homogenizing effects of alien species and in particular the underlying impact of taxonomic homogenization on functional stability of ecosystems.

Thirty-nine newly documented plant species of Great Nicobar, India

A constituent of the Sundaland Biodiversity Hotspot, Great Nicobar in the Nicobar group of islands, India, is known for rich floristic diversity. As this geographically distinct and southernmost island of India has not been surveyed for plant genetic resources, three survey-cum-exploration trips were undertaken during 2017–2019 to make an inventory of the taxa of importance for food and agriculture, besides their collection for ex situ conservation. These surveys revealed the new distribution of 39 taxa (belonging to 37 genera, 24 families) in this island, including 14 new to the Nicobar group of islands and one to Andaman & Nicobar Islands. Among the 39 taxa, 16 have the importance of being wild relatives of 15 crop species. Fourteen species are classified as naturalized ones (including four globally recognized invasive species); some of them pose potential threat to the ecosystem of this fragile island. Detailed field studies in this remote island will help in better understanding of phytogeography in general and impact of alien species on native plant diversity in particular.

More widespread alien tree species do not have larger impacts on regeneration of native tree species in a tropical forest reserve.

There is insufficient information regarding the factors affecting the environmental impacts of alien species. In particular, little is known about whether there is any relationship between the invasiveness (establishment and spread) of an introduced species and its per capita impact. We experimentally assessed the relationship between the extent of spread of up to 29 alien plant species and their impact on recruitment of native tree species in Amani Botanical Garden, Tanzania. We also studied the effects of allelochemicals of selected alien on native plant species to assess potential mechanisms of impact. We found no relationship between the extent of spread of an alien tree species and their impact on seed germination, seedling survival, and seedling communities of native trees in their understory, and no indication that allelochemicals consistently explain their effects on recruitment of the studied species. These results suggest that extent of spread cannot be used as a proxy for impact. Hence, managers should continue assessing both the spread and the impact of alien species when prioritizing alien species for management.

Alien species and the EU Water Framework Directive: a comparative assessment of European approaches

Although the European Water Framework Directive (WFD) does not refer explicitly to alien species (AS), it is clear that invasive AS (IAS) are considered a pressure on WFD water bodies. This article discusses the results of a questionnaire sent to all EU Member States, demonstrating considerable variability in the way that AS data are used in implementing the WFD. Responses were received from 18 countries.Most countries define AS in a similar way, but there are discrepancies, for example, in the use of historical dates to determine whether or not a species is considered non-native biogeographically. All countries have developed lists of AS, but those specific for WFD assessments are only used at present in the UK and the Republic of Ireland.Few countries monitor AS specifically for the WFD, or assess the risk that IAS are likely to cause water bodies to fail to achieve Good Ecological Status. This article discusses the results of a questionnaire sent to all EU Member States, demonstrating considerable variability in the way that AS data are used in implementing the WFD. Perhaps the most important difference among countries is in the use of AS data in WFD classification; many countries assume that classification methods take account of the impacts of AS, whereas separate ‘downgrading’ procedures that modify classification based on the presence and impact of IAS are used more rarely. New approaches merit further consideration, such as the application of ‘biopollution indices’ to highlight the impact of AS without affecting WFD classification. Alien species feature to some extent in river basin management plans, but more emphasis on action is needed. In addition, closer links with the Marine Strategy Framework Directive and with the 2014 EU Regulation on alien species are required to improve the control of aquatic AS.

Expansion Speed as a Generic Measure of Spread for Alien Species

The ecological impact of alien species is a function of the area colonised. Impact assessments of alien species are thus incomplete unless they take the spatial component of invasion processes into account. This paper describes a measure, termed expansion speed, that quantifies the speed with which a species increases its spatial presence in an assessment area. It is based on the area of occupancy (AOO) and can be estimated from grid occupancies. Expansion speed is defined as the yearly increase in the radius of a coherent circle having the same area as the AOO, irrespective of whether the increase is due to natural dispersal or anthropogenic transport. Two methods for estimating expansion speed are presented: one that requires several years of spatio-temporal observation data and explicitly takes detection rates into account; and one that can be used under a situation with sparse data. Using simulations and real-world data from natural history collections, it is shown that the method provides a good fit to observational datasets. Expansion speed has several valuable properties. Being based on AOO, it is an intuitive measure; as it only requires occupancy data, it is comparatively easy to estimate; and because it is a quantitative and generic measure, it increases the testability and comparability of impact assessments of alien species.

What are We Conserving? A Case Study of Mentha longifolia and Allied Species from Lithuania

AbstractAssessment of the conservation status of a species, first, should be based on its clearly defined taxonomic identity. Insufficient knowledge of certain taxonomic groups may lead to misidentifications, misinterpretations and become an obstacle for conservation. Mentha longifolia, listed as a protected plant species of Lithuania since 1981, belongs to a taxonomically complex group of species. The aim of this research was to examine available herbarium specimens of M. longifolia and verify their identification, specify distribution of this species in Lithuania and evaluate its conservation status in the country. The study was based on the analysis of herbarium specimens and information provided in references and databases. We studied a total of 93 specimens initially identified as M. longifolia. Morphological features of 30 leaves (leaf length, leaf width, petiole length, distance from leaf base to the widest place, length of leaf tooth) of both M. longifolia and M. ×villosa were measured on herbarium specimens. After the revision of herbarium specimens, we revealed that 37.6% of specimens initially identified as M. longifolia belong to other species (mostly to M. ×villosa) and 29.0% of specimens cannot be identified precisely because of the early stage of development. Only 33.4% of M. longifolia specimens were identified precisely. Thus, M. longifolia, previously supposed as quite widespread in Lithuania, after the revision appeared to be restricted mainly to the southern and south-eastern parts of the country. Applying the IUCN criteria, M. longifolia was evaluated as data deficient (DD) species. Analysis of leaf morphological traits revealed that M. longifolia and M. ×villosa can be differentiated by the length and the width of leaf blade, the distance from leaf base to the widest part of leaf and by the ratio between the length and the width of middle cauline leaves. This study revealed that taxonomic revision of the genus Mentha in Lithuania is required. Distribution of species, ecology and state of populations, impact of alien species on native congeners should be estimated in the future.

Aliens are moving to the Arctic frontiers: an integrative approach reveals selective expansion of androgenic hybrid Corbicula lineages towards the North of Russia

Increases in human activity and climate change are factors that are expected to augment the number and impact of alien species in the northern regions. In the present paper, we report the discovery of a population of Asian Corbicula clams in the North of Russia near the Arctic frontier (64°N, 40°E), which is the most northern record of these invaders in the world. This population contains two distinct lineages that are living in sympatry in a man-made channel of the Arkhangelsk thermal power plant. The first lineage belongs to the morphotype Rlc by shell morphology but reveals the FW5 mtDNA haplotype (COI and 16S rRNA genes), which was typically recorded in the morphotype R. The second lineage reveals the shell morphological pattern of the morphotype R but has the FW17 mtDNA haplotype, which usually occurs in specimens of the morphotype S. Both forms that were identified, based on conchological and anatomical features and differences in mtDNA haplotypes, reveal the same 28S rDNA sequences but show intragenomic nDNA variability with two different variants of the 28S rDNA gene within each individual (allelic sequence heterogeneity). The discrepancy between mtDNA data and shell morphology could be explained by the well-known mechanism that is associated with androgenesis together with “egg parasitism” (mitochondrial genome-capture) in invasive Corbicula clams. The intragenomic 28S rDNA variability may be due to a hybridization event which can join different alleles from the two diploid (or polyploid) parental taxa to an allopolyploid descendant. We found that the lineages that rarely occur in European populations are exclusively established in a population near the Arctic frontier. Moreover, specimens belonging to the R-morphotype with the FW17 mtDNA haplotype that has sporadic occurrences in central Europe is prevalent (> 90% of a total sample) in a mollusk assemblage at the studied site in northern Russia. Additionally, we show that the life span of Corbicula clams in high latitudes may be longer than 1 year. Isolated Corbicula populations in artificially heated or geothermal reservoirs may therefore be primary sources for a broad invasion to seasonal waterbodies of the high-latitude regions in the future as climate warming progresses.

Why adopt double standards for alien fish and homoeothermic vertebrates? A reply to Fenoglio, Delmastro, and Boano (2018)

In order to mitigate the ecological impact of alien species there is a need to control or eradicate those species that are causing a loss of biodiversity. However, such conservation actions can lack public support. In their editorial to The European Zoological Journal (Vol. 85, pp. 227–228), Fenoglio and co-authors observe that public opinion is little concerned about fish welfare and, therefore, is less likely to oppose alien fish than alien bird and mammal eradications. Alien fish management is presented as a science-driven model to which the management of alien birds and mammals should aspire, and public education is identified as a solution for the social conflicts inherent to alien species management. This reflects the authors’ opinion that a unitary, integrally scientific strategy would be the best one to counter biological invasions. However, a more flexible strategy including societal inclinations might be considered too, to avoid sabotage of the conservation actions by several predictable opponents, including animal rights movements. Moving from the latter opinion, the present reply aims at providing additional examples and argumentations on (i) why double or multiple management standards could be the only viable strategy to counter alien species, (ii) why alien fish management is not a good model, and (iii) why education cannot be the only solution for social conflicts inherent to alien species management.

Past Arctic aliens have passed away, current ones may stay

Increased human activity and climate change are expected to increase the numbers and impact of alien species in the Arctic, but knowledge of alien species is poor in most Arctic regions. Through field investigations over the last 10 years, and review of alien vascular plant records for the high Arctic Archipelago Svalbard over the past 130 years, we explored long term trends in persistence and phenology. In total, 448 observations of 105 taxa have been recorded from 28 sites. Recent surveys at 18 of these sites revealed that alien species had disappeared at half of them. Investigations at a further 49 sites characterised by former human activity and/or current tourist landing sites did not reveal any alien species. Patterns of alien species distribution suggest that greater alien species richness is more likely to be aligned with ongoing human inhabitation than sites of transient use. The probability of an alien species being in a more advanced phenological stage increased with higher mean July temperatures. As higher mean July temperatures are positively correlated with more recent year, the latter finding suggests a clear warming effect on the increased reproductive potential of alien plants, and thus an increased potential for spread in Svalbard. Given that both human activity and temperatures are expected to increase in the future, there is need to respond in policy and action to reduce the potential for further alien species introduction and spread in the Arctic.

Assemblage structure: an overlooked component of human-mediated species movements among freshwater ecosystems

The spread and impact of alien species among freshwater ecosystems has increased with global trade and human movement; therefore, quantifying the role of anthropogenic and ecological factors that increase the risk of invasion is an important conservation goal. Two factors considered as null models when assessing the potential for invasion are colonization pressure (i.e., the number of species introduced) and propagule pressure [i.e., the number (propagule size), and frequency (propagule number), of individuals of each species introduced]. We translate the terminology of species abundance distributions to the invasion terminology of propagule size and colonization size (PS and CS, respectively). We conduct hypothesis testing to determine the underlying statistical species abundance distribution for zooplankton assemblages transported between freshwater ecosystems; and, on the basis of a lognormal distribution, construct four hypothetical assemblages spanning assemblage structure, rank-abundance gradient (e.g., even vs uneven), total abundance (of all species combined), and relative contribution of PS vs CS. For a given CS, many combinations of PS and total abundance can occur when transported assemblages conform to a lognormal species abundance distribution; therefore, for a given transportation event, many combinations of CS and PS are possible with potentially different ecological outcomes. An assemblage exhibiting high PS but low CS (species poor, but highly abundant) may overcome demographic barriers to establishment, but with lower certainty of amenable environmental conditions in the recipient region; whereas, the opposite extreme, high CS and low PS (species rich, but low abundance per species) may provide multiple opportunities for one of n arriving species to circumvent environmental barriers, albeit with lower potential to overcome demographic constraints. Species abundance distributions and the corresponding influence of CS and PS are some of many influential factors (e.g., demographic and genetic stochasticity, environmental variability, composition of recipient ecosystems) that will help refine an understanding of establishment risk following the human-mediated movement of species.

Impact of alien species on the distribution of native submerged macrophytes in small rivers and agricultural canals around Lake Mikata

Impact of alien species on the distribution of native submerged macrophytes in small rivers and agricultural canals around Lake Mikata

Current distribution of the southern barred minnow, Opsaridium peringueyi (Pisces: Cyprinidae), in South Africa:Is there reason for concern?

In South Africa, relatively small, but healthy populations of Opsaridium peringueyi remain in the middle reaches of the Luvuvhu, Blyde, Sabie and Pongolo Rivers. The species may be extinct in some rivers like the Shingwedzi and lower-Olifants and its status is uncertain in the Crocodile and lower Komati/Mlumati Rivers. In many cases the rivers are transformed by the combined impact of alien species, dams and weirs, water abstraction, water regulation, pollution from industrial, agricultural, mining, forestry and urban areas as well as by sedimentation. These factors have caused the species distribution to become fragmented and have made it vulnerable to possible extinction. Because of the transformed nature of river systems in South Africa, the use of older historical data for biodiversity planning and conservation assessments might increase the risk of underrating conservation status and risks.

Current Distribution of the Southern Barred Minnow,Opsaridium peringueyi(Pisces: Cyprinidae), in South Africa: Is there Reason for Concern?

In South Africa, relatively small, but healthy populations of Opsaridium peringueyi remain in the middle reaches of the Luvuvhu, Blyde, Sabie and Pongolo Rivers. The species may be extinct in some rivers like the Shingwedzi and lower-Olifants and its status is uncertain in the Crocodile and lower Komati/Mlumati Rivers. In many cases the rivers are transformed by the combined impact of alien species, dams and weirs, water abstraction, water regulation, pollution from industrial, agricultural, mining, forestry and urban areas as well as by sedimentation. These factors have caused the species distribution to become fragmented and have made it vulnerable to possible extinction. Because of the transformed nature of river systems in South Africa, the use of older historical data for biodiversity planning and conservation assessments might increase the risk of underrating conservation status and risks.

Recovery of native zooplankton associated with increased mortality of an invasive mussel

Impacts of alien species may change with time but there are few long‐term studies of invasions. Here, we present an example of a substantial change in the impact of an alien species that appeared more than a decade after initial invasion. We studied an invasion of zebra mussels (Dreissena polymorpha) into the Hudson River (New York, USA) over a 22 year period (1987–2008) including five years of pre‐invasion observations. Zebra mussels caused a substantial and sustained decline in phytoplankton, and until recently, zooplankton. However from 2005–2008, the abundance of copepods, copepod nauplii, and rotifers recovered while tintinnid ciliates partially recovered. These changes are consistent with an increased mortality of larger (> 20 mm) zebra mussels that has altered the filter‐feeding impact of the population. Large mussels had a threshold relationship with the abundance of nauplii, rotifers, and zebra mussel veligers suppressing these microzooplankton when filtration by large mussels was > 0.5 m3m−2d−1. Zooplankton biomass declined approximately 50% after the zebra mussel invasion but has recovered to pre‐invasion levels. Overall, while zebra mussels are still present and abundant in the Hudson River, their impact on zooplankton has significantly diminished.

Impact assessment revisited: improving the theoretical basis for management of invasive alien species

The theoretical underpinnings of the assessment of invasive alien species impacts need to be improved. At present most approaches are unreliable to quantify impact at regional scales and do not allow for comparison of different invasive species. There are four basic problems that need to be addressed: (1) Some impacted ecosystem traits are spatially not additive; (2) invader effects may increase non-linearly with abundance or there may be effect thresholds impairing estimates of linear impact models; (3) the abundance and impact of alien species will often co-vary with environmental variation; and (4) the total invaded range is an inappropriate measure for quantifying regional impact because the habitat area available for invasion can vary markedly among invasive species. Mathematical models and empirical data using an invasive alien plant species (Heracleum mantegazzianum) indicate that ignoring these issues leads to impact estimates almost an order of magnitude from the real values. Thus, we propose a habitat-sensitive formula for regional impact assessment that is unaffected by non-linearity. Furthermore, we make some statistical suggestions on how to assess invader effects properly and we discuss the quantification of the invaded range. These improvements are crucial for impact assessment with the overall aim of prioritizing management of invasive species.