Invasive North American Research Articles

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.

Diversity and origins of Butomus umbellatus (flowering rush) invasion in North America

Flowering rush (Butomus umbellatus) is an invasive aquatic plant in northern USA and southern Canada. To better understand the pattern of invasion in North America and implications for management, we investigated genetic diversity and population structure of the more recent western North American invasion and compared it to the earlier eastern North America invasion using 80 variable AFLP loci. We found six invasive genotypes, indicating multiple founding events, with primarily monotypic populations indicating clonal reproduction. The genetic makeup and ploidy of the western North America populations is distinct from the earlier eastern North American invasion, with different genotypes and ploidy levels dominating different regions. Flowering rush is under consideration for classical biological control, and initial studies show that some genotypes are resistant or tolerant to a proposed plant pathogen. To inform biological control development and direct foreign exploration, we compared genetic data with Eurasian native samples and found an exact genetic match for the common western North American genotype in the Netherlands, and propose best estimates of origins for the other invasive genotypes. The different genetic makeup of the invasion at regional scales, and their differing phenotypes in terms of reproductive mode and susceptibility to highly host-specific biological control supports the investigation of specialized management programs for different portions of the North American invasion.

Natural strongholds for red squirrel conservation in Scotland

The Eurasian Red Squirrel (Sciurus vulgaris) is under threat from the invasive North American eastern Grey Squirrel (Sciurus carolinensis) with 80% of the remaining red squirrel populations in the British Isles found in Scotland. In this study we develop a spatially explicit mathematical model of the red and grey squirrel system and use it to assess the population viability of red squirrels across Scotland. In particular, we aim to identify existing forests – natural strongholds for red squirrels – that can successfully support red squirrels under UK Forestry Standard management and protect them from potential disease-mediated competition from grey squirrels. Our model results indicate that if current levels of grey squirrel control, which restrict or reduce the distribution of grey squirrels, are continued then there will be large expanses of forests in northern Scotland that support viable red squirrel populations. Model results that represent (hypothetical) scenarios where grey squirrel control no longer occurred indicated that grey squirrel range expansion and the process of red squirrel replacement would be slow. Model results for an assumed worst-case scenario where grey squirrels have expanded to all regions in Scotland identified forest regions – denoted natural strongholds – that could currently support red squirrels under UK Forestry Standard management practice. The results will be used to inform forest management policy and support a strategic review of red squirrel management by land management agencies and other stakeholders.

Penestragania apicalis (Osborn & Ball, 1898) (Hemiptera: Cicadellidae, Iassinae) – a new invasive phytophages of honey locust in Eastern Europe

In July 2020, in the course of insect collection by light trapping within the city area of Donetsk, the invasive North American leafhopper Penestragania apicalis (Osborn & Ball, 1898) (Hemiptera: Cicadellidae: Iassinae) was first recorded for Eastern Europe. This is the third specialized phytophagous species of honey locust (Gleditsia triacanthos L.) introduced to Europe. The distribution of P. apicalis within Europe is still not known, this species is most likely to be widespread throughout the places of honey locust cultivation. The main vector of invasion of P. apicalis is unintended introduction with planting material and by way of self -spread of adults. The penetration of another one specialized phytophage of honey locust into the steppe zone of Eastern Europe requires additional researching of its distribution. Registration of P. apicalis at a considerable distance from the previously known habitat indicates its wide distribution in Europe. Since it is difficult to survey the crowns of tall trees, we recommend using light traps as the simplest and most effective method for leafhoppers detecting. The level of species harmfulness in the territory of its natural range and in Euro pe has not been assessed so far; therefore, the organization of work on a detailed study of its ecological and biological characteristics is required. The formation of a multispecies complex of specialized pests can have a negative impact on the plantings of honey locust in the zone of its introduction. In this regard, the state of the P. apicalispopulation requires constant monitoring along with other invasive phytophages of Gleditsia – leaf gall midge D.gleditchiae and seed-beetle M. dorsalis.

Desert pumpkinseed: diet composition and breadth in a Moroccan river

The widely invasive North American pumpkinseed sunfish, Lepomis gibbosus, is currently established in desert rivers in Morocco. The success of pumpkinseed in novel ecosystems has been associated with its generalist diet, but this trait remains unevaluated in arid regions. Desert rivers are harsh environments with limited water and prey availability which may adversely constrain the diet of fish. Here we studied the diet of pumpkinseed across 4 sites in the Draa River, embracing a 450 m elevational gradient covering from extremely dry lowlands to relatively humid highlands. We described pumpkinseed diet through the analysis of stomach contents of 82 individuals, collected in the fall of 2013. Pumpkinseed diet was dominated by Chironomidae in dry lowlands, while Ephemeroptera, Heteroptera, Trichoptera and Odonata were relevant prey in more humid highlands. Population diet breadth expanded with elevation, but individual specialization in diet was low among all sites. Our results highlight considerable changes in diet composition and breadth with aridity, suggesting that feeding plasticity and use of exclusive, locally abundant prey rather than generalized feeding may be associated with the success of pumpkinseed in most arid areas in desert rivers.

Reproductive Possibilities of Alien Species Fraxinus pennsylvanica Marsh. in the Forest Stands of the City of Bryansk

The invasive North American species Fraxinus pennsylvanica Marsh. has a high reproductive potential in natural and urban habitats. The species is characterized by intense seed reproduction and the active distribution of seeds. However, their germination requires quite specific conditions, which are found mainly in floodplain ecosystems and occasionally in mesophytic and xerophytic urban habitats. Intense vegetative renewal allows ash trees to linger in their habitats for a long time, including after disturbances, but it is ineffective for the rapid spread of the species and occupation of new territories. F. pennsylvanica actively penetrates into natural and seminatural communities, acts as an edifier and dominant, displaces, and (or) prevents the regeneration of species of natural flora. However, these features are not pronounced in all habitats, but mainly in river valleys, including forest cultures with a simplified structure. The possible spread of F. pennsylvanica diaspores into the river floodplains by birds and humans (randomly) is of concern, because it can lead to the mass distribution of the species with a subsequent threat to the biodiversity of river valleys.

On the North American invasion of the House Sparrow and its absence in the Yucatan Peninsula

Peña-Peniche, A., C. Mota-Vargas, M. García-Arroyo, and I. MacGregor-Fors. 2021. On the North American invasion of the House Sparrow and its absence in the Yucatan Peninsula. Avian Conservation and Ecology 16(1):18. https://doi.org/10.5751/ACE-01835-160118

Comparison of native and non-native predator consumption rates and prey avoidance behavior in North America and Europe.

Novel predator–prey interactions can contribute to the invasion success of non‐native predators. For example, native prey can fail to recognize and avoid non‐native predators due to a lack of co‐evolutionary history and cue dissimilarity with native predators. This might result in a competitive advantage for non‐native predators. Numerous lady beetle species were globally redistributed as biological control agents against aphids, resulting in novel predator–prey interactions. Here, we investigated the strength of avoidance behavior of the pea aphid (Acyrthosiphon pisum) toward chemical cues of native lady beetles and non‐native Asian Harmonia axyridis and European Coccinella septempunctata and Hippodamia variegata in North America, hypothesizing that cues of non‐native lady beetles induce weaker avoidance behavior than cues of co‐evolved native lady beetles. Additionally, we compared aphid consumption of lady beetles, examining potential predation advantages of non‐native lady beetles. Finally, we compared cue avoidance behavior between North American and European pea aphid populations and aphid consumption of native and non‐native lady beetles in North America and Europe. In North America, pea aphids avoided chemical cues of all ladybeetle species tested, regardless of their origin. In contrast to pea aphids in North America, European pea aphids did not avoid cues of the non‐native H. axyridis. The non‐native H. axyridis and C. septempunctata were among the largest and most voracious lady beetle species tested, on both continents. Consequently, in North America non‐native lady beetle species might have a competitive advantage on shared food resources due to their relatively large body size, compared to several native American lady beetle species. In Europe, however, non‐native H. axyridis might benefit from missing aphid cue avoidance as well as a large body size. The co‐evolutionary time gap between the European and North American invasion of H. axyridis likely explains the intercontinental differences in cue avoidance behavior and might indicate evolution in aphids toward non‐native predators.

Flood dynamics dictate distributions of Elaeagnus angustifolia L. (Russian olive) on a riverine floodplain

North American invasions of Elaeagnus angustifolia L. (Russian olive) are still expanding, and hydrochory could be increasing invasion impacts along rivers. Spatial association between riverine flood-inundation patterns and E. angustifolia distributions suggests a link between seed movement potential and invasion patterns in time and space. Using output from hydraulic inundation models, we mapped inundation zones associated with successive flood return intervals within 10.81 km2 of the estimated 500-year floodplain of the Yellowstone River, Montana, USA. We then evaluated spatial relationships among inundation zones and E. angustifolia distribution. Elaeagnus angustifolia was highly spatially associated with frequent flood return intervals: 80% of E. angustifolia exists within a subset of the floodplain predicted to flood every 10 years or less, with the highest occupancy in the 1.5- to 5-year return zones. Within frequently inundated areas, floodplain occupancy of E. angustifolia was distributed in patterns consistent with likely areas of sediment deposition. Thus, existing predictions of invasion timelines are likely to improve with explicit consideration of dispersal opportunities associated with hydrochory during flooding. In particular, if hydrochory is a significant secondary dispersal mechanism, then seed immigration at flood intervals of 5 years or less could lead to substantially shorter invasion lags than currently predicted.

A layover in Europe: Reconstructing the invasion route of asexual lineages of a New Zealand snail to North America.

Non-native invasive species are threatening ecosystems and biodiversity worldwide. High genetic variation is thought to be a critical factor for invasion success. Accordingly, the global invasion of a few clonal lineages of the gastropod Potamopyrgus antipodarum is thus both puzzling and has the potential to help illuminate why some invasions succeed while others fail. Here, we used SNP markers and a geographically broad sampling scheme (N=1617) including native New Zealand populations and invasive North American and European populations to provide the first widescale population genetic assessment of the relationships between and among native and invasive P. antipodarum. We used a combination of traditional and Bayesian molecular analyses to demonstrate that New Zealand populations harbour very high diversity relative to the invasive populations and are the source of the two main European genetic lineages. One of these two European lineages was in turn the source of at least one of the two main North American genetic clusters of invasive P. antipodarum, located in Lake Ontario. The other widespread North American group had a more complex origin that included the other European lineage and two New Zealand clusters. Altogether, our analyses suggest that just a small handful of clonal lineages of P. antipodarum were responsible for invasion across continents. Our findings provide critical information for prevention of additional invasions and control of existing invasive populations and are of broader relevance towards understanding the establishment and evolution of asexual populations and the forces driving biological invasion.

Evolution of starvation resistance in an invasive insect species, Aethina tumida (Coleoptera: Nitidulidae).

Starvation resistance, or the ability to survive periods without food, can shed light on selection pressure imposed by food scarcity, including chances to invade new regions as a result of human transport. Surprisingly, little information is known about starvation resistance for invasive insect species. Given that native and invasive populations differ in starvation resistance, this would suggest different selection scenarios and adaptive shifts fostering invasion success. Here, we show striking differences in starvation resistance of adult small hive beetles Aethina tumida (SHB) between native and invasive populations. In the laboratory, starvation resistance of freshly emerged laboratory‐reared and field‐collected adult females and males was evaluated in the beetle's native African range and in their invasive North American range. SHB in their native African range survived longer than SHB in their invasive North American range. Across ranges, females survived longer than males. Field‐collected SHB survived in Africa longer than freshly emerged ones, but not in the invasive range. This suggests no selection for starvation resistance in the invasive range, possibly due to differences between African and European‐derived honey bee hosts facilitating a trade‐off scenario between reproduction and starvation resistance. The ability of adult females to survive up to two months without food appears to be one factor contributing to the invasion success of this species. Assuming food availability is usually high in the invasive ranges, and trade‐offs between starvation resistance and fecundity/reproduction are common, it seems as if selection for starvation resistance during transport could set up potential trade‐offs that enhance reproduction after invasion. It would be interesting to see if this is a possible general pattern for invasive insect species.

Environmental factors affecting the distributions of the native Eurasian beaver and the invasive North American beaver in Finland

When planning conservation and reintroductions of native species and control of invasive species, it is important to understand the environmental factors affecting species distributions. Habitat suitability largely determines where species can occur, but in addition to habitat and food resources, it is important to also consider human disturbance and climate when mapping possible distributions. We studied the environmental factors affecting the present distribution of the native Eurasian beaver (Castor fiber) and the invasive North American beaver (C. canadensis) in Finland. We compared the role of food resources, aquatic habitat type, anthropogenic disturbance and climate for beaver occurrence with species distribution models. We created maps of suitable areas for the two species and compared how the results would change if these two ecologically similar species were modelled together. We found that aquatic habitat type and climate largely explain the present distributions of the species. In addition, there were differences between the species in their preference for food resources, aspen, birch and grey alder. However, we suspect that the species' reintroduction history, i.e. the differences in the present environment, much explain the differences found between the species. We conclude that when planning possible reintroductions for the Eurasian beaver, factors other than food resources should also be considered. We also suggest that studies on habitat suitability should consider the history of the species and include data from different environments. Thus, more comprehensive information for management planning would be achieved and a better ability to predict the location of optimal areas for the species.

Looking for the North American Invasion in Mexico City

Abstract At a time when Latinxs play an increasingly important role in U.S. society, a group of teachers seek out places in Mexico City connected to the U.S. Invasion of 1847–1848, hoping to understand how it is remembered there today. Museums and memorials commemorate the sacrifices made by a wronged nation and honor the legendary figures who have come to dominate its popular narrative of the war, Los Niños Héroes and the San Patricios. By contrast, the historic landscape is nearly silent on Santa Anna and the Treaty of Guadalupe Hidalgo. Back home, the group incorporates the places they visited into their classrooms through images and stories. Finally, they consider how the war’s place in the teaching of Texas and U.S. history is changing and offer Elliott West’s Greater Reconstruction thesis as a framework for reimagining the nation’s history by focusing on how the expansion of this period affected the peoples over whom the border crossed and reoriented national attention toward Latin America and the Pacific. Throughout the essay, a Mexican American reflects on his first encounter with the capital of his ancestral homeland.

Scaphoideus titanus Ball, 1932 (Hemiptera: Cicadellidae) - a new invasive pest of grapes on the territory of the Donbass

In August 2019, in the course of reconnaissance monitoring of insect pest complex of grapevine in the territory of the Donbass, the invasive North American grapevine leafhopper Scaphoideus titanus Ball, 1932 (Hemiptera: Cicadellidae) was first recorded. A pest outbreak has been registered in the territory of the Novoazovsk region. A targeted search for the species in other areas ended up with a negative result. Scaphoideus titanus is a specialized pest of grapevine and a pathogenic agent of Grapevine flavescence doree - phytoplasma 'Candidatus Phytoplasma vitis' (Phytoplasma vitis), included in the list of pests of the European and Mediterranean Plant Protection Organization (EPPO) and the Common List of Quarantine Pests of the Eurasian Economic Union. The paper presents information on the history of invasion and distribution of this leafhopper throughout Europe, host plants, biology, life cycle and pathways of phytoplasma ‘ Candidatus Phytoplasma vitis’. The range expansion of S. titanus threatens with penetration of the causative agent of grapevine flavescence doree into the Donbass and requires purposeful studies on the features of biology, distribution and population condition of grapevine leafhopper in the region.

El cadete Agustín Melgar y la atención del trauma vascular periférico militar durante la Batalla de Chapultepec

Trauma to peripheral vascular organ is a very frequent condition during military conflicts. Fortunately, comprehensive understanding of local and systemic pathophysiology, in addition to the development of innovative surgical techniques and technological advances, have improved the outcome regarding to survival and anatomic and functional conservation of the limbs. In this manuscript, we perform an historical and state of the art review related to the approach of the peripheral vascular trauma, on the basis of an heroical episode from the Mexico City's Campaign, during North American invasion 1846-1848: the defense of Chapultepec's Castle by cadet Agustin Melgar.

Minimizing Risk and Maximizing Spatial Transferability: Challenges in Constructing a Useful Model of Potential Suitability for an Invasive Insect

AbstractForecasting the spread and potential impacts of invasive, alien species is vital to relevant management and policy decisions. Models that estimate areas of potential suitability are useful to guide early detection and eradication, inform effective budget allocations, and justify quarantine regulations. Machine-learning is a rapidly emerging technology with myriad applications, including the analysis of factors that govern species’ distributions. However, forecasts for invasive species often require extrapolation into novel spaces, which may severely erode model reliability. Using the popular machine-learning platform, MaxEnt, we integrate numerous tools and recommendations to demonstrate a method of rigorous model development that emphasizes assessment of model transferability. Our models use Lymantria dispar dispar (L.) (Lepidoptera: Erebidae), an insect brought to the United States in the late 1860s from Europe and subsequently well monitored in spread. Recent genetic analyses provide evidence that the eastern North American population originated in Germany, France, and northern Italy. We demonstrate that models built and assessed using typical methodology for invasive species (e.g., using records from the full native geographic range) showed the smallest extent of extrapolation, but the worst transferability when validated with independent data. Conversely, models based on the purported genetic source of the eastern North American populations (i.e., a subset of the native range) showed the greatest transferability, but the largest extent of extrapolation. Overall, the model that yielded high transferability to North America and low extrapolation was built following current recommendations of spatial thinning and parameter optimization with records from both the genetic source in Europe and early North American invasion.

Seasonal and directional dispersal behavior in an ongoing dove invasion

Range expansions require the dispersal of individual organisms, but dispersal behavior is notoriously difficult to study. Eurasian collared‐doves have colonized both Europe and North America this century, with both initial invasions proceeding northwestward via ‘jump’ dispersal. The European population has reached carrying capacity, but in the Americas, where exponential population growth continues, little is known about dispersal behavior. I queried citizen science field notes to investigate Eurasian collared‐dove dispersal behavior in North America along the Pacific Ocean, a natural barrier to northwestward landbird dispersal. I examined coastal and pelagic records of Eurasian collared‐doves to determine the seasonality and directionality of dispersal flights and to assess changes in the frequency of dispersal‐related behavior across years. Most reports of Eurasian collared‐doves flying in flocks along the coast and most pelagic sightings were in March–May, mirroring the spring natal dispersal documented during the European invasion. Almost all spring coastal flocks were flying north, consistent with the overall northwestward direction of the initial North American invasion and northward deflection of northwest‐bound birds upon encountering the Pacific Ocean. Spring flying flock observations showed no significant change in frequency from 2010 to 2018 after controlling for overall increases in spring collared‐dove reports. This refined understanding of Eurasian collared‐dove dispersal behavior informs full life cycle management of this rapidly increasing invader in the Americas, raises new questions about evolutionary mechanisms driving this spectacular invasion, and illustrates the potential power of citizen science field notes for documenting dispersal behavior, a longstanding challenge in ecology.

Biogeographic variation in resistance of the invasive plant, Alliaria petiolata, to a powdery mildew fungus and effect of resistance on competitive dynamics

Garlic mustard is an invasive Eurasian biennial that has spread throughout the eastern United States and southern Canada. Populations of this plant vary in their susceptibility to Erysiphe cruciferarum, a causal agent of powdery mildew disease in Brassicaceous plants. We examined whether there were biogeographic patterns in the distribution of resistance in invasive North American and native European populations of this plant. We grew plants from 78 invasive and 20 native populations and screened them for powdery mildew resistance in the greenhouse. We found that populations were mostly monomorphic for either resistance or susceptibility but that some polymorphic populations were found from both continents. The proportion of populations showing resistance versus susceptibility was similar in both Europe and North America. Within continents, the spatial distribution of resistant and susceptible populations did not deviate significantly from random. We also examined whether the possession of the resistance trait alter intraspecific competitive dynamics. In two trials, we competed plants from resistant and susceptible populations in a target-neighbor design in the presence and absence of powdery mildew inoculum and examined the growth of the target plant. Target plants from resistant populations were overall larger than target plants from susceptible populations. Target plants were overall larger when grown in competition with susceptible neighbors. Further, resistant target plants showed a greater degree of release from competition when grown with a susceptible neighbor versus a resistant neighbor than the degree of release shown by susceptible target plants. This suggests a benefit of possessing the resistance trait with little apparent costs which should promote selection for this trait within plant populations.

Skewed adult sex ratios observed early in the North American invasion of Lycorma delicatula (Hemiptera: Fulgoridae)

Abstract The spotted lanternfly, Lycorma delicatula, (Hemiptera Fulgoridae) is an invasive pest in Korea and the United States, but originating from mainland Asia. Both tree of heaven, Ailanthus altissima, and grapevine (Vitis) are known to be preferred hosts of adults. However, much is unknown about its adult behavior with respect to mating or dispersal patterns. In 2015, just after it was discovered in the United States, we performed an observational study to elucidate movement by adults in relation to host plants. We noted weekly changes in their presence and sex ratio on host plants at four sites in a quarantine zone in Berks County, PA. Just after adult emergence, the trunks of large (>15 cm diameter at breast height) A. altissima hosted nearly exclusively females, while smaller A. altissima, Vitis, Salix nigra, and other less commonly inhabited tree species, had high proportions of males. By October 1st, greater proportions of males were observed on the trunks of the larger A. altissima trees. Pairings of males and females were observed most frequently on the smaller A. altissima and Vitis. At the very end of the season, a large mixed-sex population was found on Salix nigra, which was the only deciduous tree species in the area still bearing green leaves.

Scent-sniffing dogs can discriminate between native Eurasian and invasive North American beavers

The invasion of a species can cause population reduction or extinction of a similar native species due to replacement competition. There is a potential risk that the native Eurasian beaver (Castor fiber) may eventually be competitively excluded by the invasive North American beaver (C. canadensis) from areas where they overlap in Eurasia. Yet currently available methods of census and population estimates are costly and time-consuming. In a laboratory environment, we investigated the potential of using dogs (Canis lupus familiaris) as a conservation tool to determine whether the Eurasian or the North American beaver is present in a specific beaver colony. We hypothesized that dogs can discriminate between the two beaver species, via the odorant signal of castoreum from males and females, in two floor platform experiments. We show that dogs detect scent differences between the two species, both from dead beaver samples and from scent marks collected in the field. Our results suggest that dogs can be used as an “animal biosensor” to discriminate olfactory signals of beaver species, however more tests are needed. Next step should be to test if dogs discern between beaver species in the field under a range of weather conditions and habitat types and use beaver samples collected from areas where the two species share the same habitat. So far, our results show that dogs can be used as a promising tool in the future to promote conservation of the native beaver species and eradication of the invasive one. We therefore conclude that dogs may be an efficient non-invasive tool to help conservationist to manage invasive species in Europe, and advocate for European wildlife agencies to invest in this new tool.