Comparative genetic and epigenetic of the Sphagneticola trilobata (L.) Pruski from different regions in China

BACKGROUND

Sphagneticola trilobata (L.) Pruski is a prevalent and widely distributed invasive plant in South China. To investigate the molecular mechanisms underlying its rapid adaptation, we employed DNA methylation-sensitive amplified polymorphism (MSAP) and simple sequence repeat (SSR) analysis to study 60 S. trilobata individuals collected from Fuzhou (FZ), Haikou (HK), Jinghong (JH) and Guangzhou (GZ).

RESULTS

In this study, we computed the Shannon diversity index (I) of SSR and MSAP as 0.354 and 0.303, respectively. The UPGMA phylogenetic tree and PCoA analyses showed that MSAP had a better discriminatory power to distinguish populations from different regions. Notably, the GZ population was found to be the most distinct from the other three populations. Moreover, Mantel analysis revealed a significantly higher correlation between epigenetic distance and geographic distance as compared to genetic distance and geographic distance. Consequently, the correlation between epigenetic distance and geographic distance observed to be markedly stronger than that between genetic distance and geographical distance on Mantel analysis.

CONCLUSIONS

The S. trilobata populations in various regions displayed a high of complementary genetic and epigenetic diversity, which was a key feature contributing to their rapid invasion. Interestingly, the correlation between epigenetics and geographical distance was significantly stronger than that observed for genetics and geographical distance. These findings indicated that the epigenetic mechanism of S. trilobar exhibited high plasticity, leading to significant differences in methylation pattern across different populations.

Pangenomics of the death cap mushroom Amanita phalloides, and of Agaricales, reveals dynamic evolution of toxin genes in an invasive range

The poisonous European mushroom Amanita phalloides (the "death cap") is invading California. Whether the death caps' toxic secondary metabolites are evolving as it invades is unknown. We developed a bioinformatic pipeline to identify the MSDIN genes underpinning toxicity and probed 88 death cap genomes from an invasive Californian population and from the European range, discovering a previously unsuspected diversity of MSDINs made up of both core and accessory elements. Each death cap individual possesses a unique suite of MSDINs, and toxin genes are significantly differentiated between Californian and European samples. MSDIN genes are maintained by strong natural selection, and chemical profiling confirms MSDIN genes are expressed and result in distinct phenotypes; our chemical profiling also identified a new MSDIN peptide. Toxin genes are physically clustered within genomes. We contextualize our discoveries by probing for MSDINs in genomes from across the order Agaricales, revealing MSDIN diversity originated in independent gene family expansions among genera. We also report the discovery of an MSDIN in an Amanita outside the "lethal Amanitas" clade. Finally, the identification of an MSDIN gene and its associated processing gene (POPB) in Clavaria fumosa suggest the origin of MSDINs is older than previously suspected. The dynamic evolution of MSDINs underscores their potential to mediate ecological interactions, implicating MSDINs in the ongoing invasion. Our data change the understanding of the evolutionary history of poisonous mushrooms, emphasizing striking parallels to convergently evolved animal toxins. Our pipeline provides a roadmap for exploring secondary metabolites in other basidiomycetes and will enable drug prospecting.

Testing differences of marine non-indigenous species diversity across Macaronesia using a standardised approach

The introduction of non-indigenous species (NIS) induces severe impacts on marine biodiversity and ecosystems. Macaronesia is an ecologically relevant region where several NIS were detected recently. For the first time, a standard experimental approach was designed to examine biofouling assemblages and investigate NIS across the region. In this context, sessile biofouling assemblages were examined in four recreational marinas in all the Macaronesian archipelagos from 2018 to 2020: the Azores, Madeira, Canary Islands, and Cabo Verde. We hypothesised that NIS numbers, abundance, and recruitment differed in each location due to abiotic and biotic features. From the Azores (higher latitudes) to Cabo Verde (lower latitudes), NIS recruitment and percentage cover decreased following a partial latitude gradient. The present study unveiled 25 NIS, with new records for the Azores (two cryptogenic species), Canary Islands (one NIS and two cryptogenic species), and Cabo Verde (three NIS and three cryptogenic species). The present research represents a pioneer and relevant step in advancing our current understanding of marine biological invasions in Macaronesia, employing a standard and low-cost approach.

Genomic insights into the postintroduction failure of the Asian icefish Protosalanx chinensis in China

Biological introductions provide a natural ecological experiment unfolding in a recent historical timeframe to elucidate how evolutionary processes (such as founder effects, genetic diversity and adaptation) shape the genomic landscape of populations postintroduction. The Asian icefish, Protosalanx chinensis, is an economically important fishery resource, deliberately introduced into dozens of provinces across China for decades. However, while invading and disturbing the local ecosystem, many introduced populations declined, disappearing mysteriously in a very short time. The way in which various evolutionary forces integrate to result in invasion failure of an introduced population remains unknown. Here, we performed whole-genome sequencing of 10 species from the Salangidae family and 70 Asian icefish (Protosalanx chinensis) individuals from 7 geographic populations in China, aiming to characterize the evolutionary fate of introduced populations. Our results show that compared to other Salangidae species, P. chinensis has low genetic diversity, potentially due to the long-lasting decline in population size. In a recently introducted population, Lugu lake, severe sampling effects and a strong bottleneck further deteriorated the genomic landscape. Although the introduced population showed signs of reduced genetic load, the purging selection efficiency was low. Our selective sweep analysis revealed site frequency changes in candidate genes, including gata1a and hoxd4b, which could be associated with a decrease in dissolved oxygen in the deep-water plateau lake. These findings caution against the widespread introduction of P. chinensis in China and lay the groundwork for future use of this economically species.

Evidence of a compensatory response in invasive Rusty Crayfish (Faxonius rusticus) following intensive harvest removal from northern Lake Michigan fish spawning reefs

The goal of most invasive species suppression programs is to achieve long-term sustained reductions in population abundance, yet removal programs can be stymied by density-dependent population responses. We tested a harvest removal strategy for invasive Rusty Crayfish (Faxonius rusticus) at two nearshore native fish spawning habitats in northern Lake Michigan. Changes in average Rusty Crayfish densities were evaluated with a before-after reference-impact study design. We removed 3182 Rusty Crayfish, primarily adults (> 20 mm carapace length), at two sites over two harvest seasons, expending 17,825 trap days in effort. Generalized linear modeling results suggested a statistically significant reduction in Rusty Crayfish densities was achieved at one reef, Little Traverse Bay (LTB Crib). Reduced densities were sustained over the egg maturation period for native fish and into the following year after removal ceased. By late summer/early fall, between consecutive suppression efforts in 2018 and 2019, we observed a threefold increase in pre-removal densities. Size-frequency histograms from diver quadrat surveys showed higher abundances of juvenile (< 20 mm carapace length) size classes the following spring and summer at LTB Crib compared to its paired reference site. Stock-recruit curves fit to count data, pooled across all sites, provided further evidence of density-dependence. With a proviso that we only conducted two seasons of consecutive suppression, this study highlights an important aspect of invasive species management and raises questions about the efficacy of adult-only crayfish removal strategies.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10530-023-03076-6.

Karyotypic and Molecular Analysis of Pterygoplichthys pardalis (Castelnau 1855) from the Lower Amazon River

Pterygoplichthys pardalis is an armored catfish native to South America and an important resource for the ornamental fish industry. Recently, several exotic populations have been introduced into rivers on five continents. Despite its commercial and environmental importance, P. pardalis is poorly studied from a genetic perspective. In this study, we analyzed the karyotype of P. pardalis from the Amazon River and molecular variations in the mitochondrial gene Cytochrome oxidase I (COI) between native and exotic populations. The karyotype presented diploid number 2n = 52 and NF = 100 without cytogenetic variation between males and females. Nucleolus organizer regions (Ag-NOR) in the distal region of the long arm of pair 12 coincided with the 18S hybridization signal, whereas 5S was syntenic to this chromosome but localized in the short arm. The constitutive heterochromatin was restricted in the distal regions of pairs 4, 12, 25, and 26. Telomeric probes showed only distal hybridization signals. The karyotype of P. pardalis diverged from that of its congeners, and COI molecular variation revealed four haplotypes. The Philippine population revealed the greatest diversity with three haplotypes, while haplotype H1 was the most abundant and observed in both native and exotic populations. This new genetic data contributes to species management and provides useful information from an aquaculture perspective.

Implications of taxonomic misidentification for future invasion predictions: Evidence from one of the most harmful invasive marine algae

Invasive species have been a focus of concern in recent decades, becoming more problematic due to the cumulative impacts of climate change. Understanding the interactions among stress factors is essential to anticipate ecosystems' responses. Hereby, robust modeling frameworks must be able to identify the environmental drivers of invasion and forecast the current and future of their potential distribution. These studies are essential for the management of invasions and to be prepared for the future we are facing. Here we demonstrate that taxonomic misidentifications may lead to absolutely erroneous predictions, by using as an example one of the worst invasive species in the Mediterranean Sea (Lophocladia lallemandii), which has been misidentified for three decades and now is correctly identified. Consequently, and bearing in mind overall trends in species misidentification due to the loss of taxonomic expertise and the presence of cryptic species, among others, attempts to understand and predict species involved in invasion processes must always first consider taxonomic studies.

Trophic ecology of co-occurring fishes in the Sundays River Valley irrigation ponds, assessed using stable isotope and gut content analyses

The analysis of food web structures has increased the understanding of the dynamics of organisms belonging to different trophic levels. In this study, the diet of two native species, Glossogobius callidus and Gilchristella aestuaria, was assessed in the presence of two non-native species, Oreochromis mossambicus and Gambusia affinis, in irrigation ponds, Eastern Cape Province, South Africa. The proportion of dietary items consumed and assimilated by the four fish species were inferred from gut contents and carbon and nitrogen stable isotope analysis. Stable isotope analysis revealed that both G. affinis and O. mossambicus had a larger isotopic niche size than G. callidus and G. aestuaria. Although G. callidus fed on benthic resources and G. aestuaria fed on phytoplankton, gut content analysis showed that G. callidus, O. mossambicus and G. affinis fed predominantly on benthic resources, whereas G. aestuaria fed mainly on plankton resources. Considerable niche overlap corroborates the view that resource competition is a major factor shaping the composition of the four fish species. This study highlighted the low diversity of the food web within the Sundays River Valley irrigation ponds, where food items are shared by all the small-bodied fishes.

Osmia taurus (Hymenoptera: Megachilidae): A Non-native Bee Species With Invasiveness Potential in North America

Bees are important pollinators and are essential for the reproduction of many plants in natural and agricultural ecosystems. However, bees can have adverse ecological effects when introduced to areas outside of their native geographic ranges. Dozens of non-native bee species are currently found in North America and have raised concerns about their potential role in the decline of native bee populations. Osmia taurus Smith (Hymenoptera: Megachilidae) is a mason bee native to eastern Asia that was first reported in the United States in 2002. Since then, this species has rapidly expanded throughout the eastern part of North America. Here, we present a comprehensive review of the natural history of O. taurus, document its recent history of spread through the United States and Canada, and discuss the evidence suggesting its potential for invasiveness. In addition, we compare the biology and history of colonization of O. taurus to O. cornifrons (Radoszkowski), another non-native mason bee species now widespread in North America. We highlight gaps of knowledge and future research directions to better characterize the role of O. taurus in the decline of native Osmia spp. Panzer and the facilitation of invasive plant-pollinator mutualisms.

Multiple mating by both sexes in an invasive insect species, Aethina tumida (Coleoptera: Nitidulidae)

Multiple mating by both sexes is common among sexually reproducing animals. Small hive beetles (SHB), Aethina tumida, are parasites of bee nests endemic to sub-Saharan Africa and have become a widespread invasive species. Despite the considerable economic damages they can cause, their basic biology remains poorly understood. Here we show that male and female small hive beetles can mate multiple times, suggesting that costs for mating are low in this species. In an invasive A. tumida population in the United States, a combination of laboratory experiments for males and paternity analysis with eight polymorphic DNA microsatellite markers for field-caught females were used to estimate the number of mating by both sexes. The data show that females and males can mate multiple times-females mated with up to eight males, whereas males mated with at least seven females. The results also showed that A. tumida displayed a skewed paternity, although this was not consistent among the tested females. Thus, first or last male advantage seem to be unlikely in A. tumida. Our observations that individuals of both sexes of A. tumida can mate multiple times opens new research avenues for examining drivers of multiple mating and determining the role it may play in promoting biological invasions.

Sex-specific outbreeding advantages and sexual dimorphism in the seedlings of dioecious trees

PREMISE

Dioecious trees are important components of many forest ecosystems. Outbreeding advantage and sexual dimorphism are two major mechanisms that explain the persistence of dioecious plants; however, they have rarely been studied in dioecious trees.

METHODS

We investigated the influence of sex and genetic distance between parental trees (GDPT) on the growth and functional traits of multiple seedlings of a dioecious tree, Diospyros morrisiana.

RESULTS

We found significant positive relationships between GDPT and seedling sizes and tissue density. However, the positive outbreeding effects on seedling growth mainly manifested in female seedlings, but were not prominent in males. Among seedlings, the male ones generally had higher biomass and leaf area than female seedlings, but such differences diminished as GDPT increased.

CONCLUSIONS

Our research highlights that outbreeding advantage in plants can be sex-specific and that sexual dimorphism begins from the seedling stage of dioecious trees.

A lack of population structure characterizes the invasive Lonicera japonica in West Virginia and across eastern North America

Invasive plant species cause massive ecosystem damage globally, yet represent powerful case studies in population genetics and rapid adaptation to new habitats. The availability of digitized herbarium collections data, and the ubiquity of invasive species across the landscape make them highly accessible for studies of invasion history and population dynamics associated with their introduction, establishment, spread, and ecological interactions. Here we focus on Lonicera japonica, one of the most damaging invasive vine species in North America. We leveraged digitized collections data and contemporary field collections to reconstruct the invasion history and characterize patterns of genomic variation in the eastern USA, using a straightforward method for generating nucleotide polymorphism data and a recently published, chromosome-level genome for the species. We found an overall lack of population structure among sites in northern West Virginia, USA, as well as across sites in the central and eastern USA. Heterozygosity and population differentiation were both low based on Fst, analysis of molecular variance, principal components analysis, and cluster-based analyses. We also found evidence of high inbreeding coefficients and significant linkage disequilibrium, in line with the ability of this otherwise outcrossing, perennial species to propagate vegetatively. Our findings corroborate earlier studies based on allozyme data, and suggest that intentional, human-assisted spread explains the lack of population structure, as this species was planted for erosion control and as an ornamental, escaping cultivation repeatedly across the USA. Finally, we discuss how plant invasion genomics can be incorporated into experiential undergraduate education as a way to integrate teaching and research.

Population genetic structure of a recent insect invasion: a gall midge, Asynapta groverae (Diptera: Cecidomyiidae) in South Korea since the first outbreak in 2008

Outbreaks of Asynapta groverae, an invasive mycophagous gall midge, in South Korea have been repeatedly reported since the first occurrence in 2008. This species is a nuisance to residents owing to its mass emergence from newly built and furnished apartments. Here, the levels of genetic diversity, divergence, and structure of invasive A. groverae populations were investigated to understand their ability to survive in novel locations. Population genetic analyses were performed on seven invasive populations, including the first outbreak, sporadically emerged, and two laboratory-isolated (quarantined) populations, using the mitochondrial COI sequences and the ten novel microsatellite markers developed in this study. Non-indigenous A. groverae managed to maintain their populations for 12 years despite decreased genetic polymorphisms resulting from multiple incidences of founder effects by a small number of colonists. Additionally, the advantageous sustainability of A. groverae in the particle boards from which they emerge suggests that human-mediated dispersal is plausible, which may allow for the successful spread or invasion of A. groverae to new locations. This study is one of the few examples to demonstrate that an insect species successfully invaded new regions despite exhibiting decreased genetic diversity that was maintained for a decade. These findings indicate that the high genetic diversity of the initial founding population and asexual reproduction would contribute to the successful invasion of A. groverae in novel environments.

Confirmation of the local establishment of alien invasive turtle, Pseudemys peninsularis, in South Korea, using eggshell DNA

Alien invasive species are posing conservation challenges worldwide. Pet trade, one of the many ways, is worsening the situation. Especially, pet turtles have been released into nature due to their longer life span and peoples' religious and traditional beliefs. In addition, unwanted and undesired pets are also released. While information on the successful local establishment and subsequent dispersal into new habitats is required to designate an invasive and ecosystem-disturbing species, alien freshwater turtle nests have always been hard to find and identify in nature. Because one should identify nests by the eggs, which do not always guide properly, as adults abandon the sites quickly. We thought the recent advancement in DNA technology may help improve the situation. We studied Pseudemys peninsularis, one of the most traded freshwater turtle pet species, which has already been reported from a wide range of wild areas in South Korea. Yet, it is not designated as ecosystem-disturbing species due to a lack of adequate information on their local reproduction and establishment. We conducted surveys and found two nests in Jeonpyeongje Neighborhood Park, Maewol-dong, Seo-gu, Gwangju. We developed the methodology for extracting DNA from the eggshells and successfully identified the nests by phylogenetic analysis and verified through egg characteristics and morphological features of artificially hatched juveniles. This was the first successful initiative to extract DNA from freshwater turtle eggshells. We believe it will help future researchers identify the alien invasive turtle nests and develop their control and management policies. In addition, our study also included comparative descriptions and schematic diagrams of the eggs of eight freshwater turtles, including a native and three ecosystem-disturbing species, from South Korea. We urged an immediate designation of P. peninsularis as an ecosystem-disturbing species considering its local establishment, distribution range, and potential negative impact on native ecosystems.

Mitochondrial genome sequencing and analysis of the invasive Microstegium vimineum: a resource for systematics, invasion history, and management

Premise of the Research

Plants remain underrepresented among species with sequenced mitochondrial genomes (mitogenomes), due to the difficulty in assembly with short-read technology. Invasive species lag behind crops and other economically important species in this respect, representing a lack of tools for management and land conservation efforts.

Methodology

The mitogenome of Microstegium vimineum, one of the most damaging invasive plant species in North America, was sequenced and analyzed using long-read data, providing a resource for biologists and managers. We conducted analyses of genome content, phylogenomic analyses among grasses and relatives based on mitochondrial coding regions, and an analysis of mitochondrial single nucleotide polymorphism in this invasive grass species.

Pivotal Results

The assembly is 478,010 bp in length and characterized by two large, inverted repeats, and a large, direct repeat. However, the genome could not be circularized, arguing against a "master circle" structure. Long-read assemblies with data subsets revealed several alternative genomic conformations, predominantly associated with large repeats. Plastid-like sequences comprise 2.4% of the genome, with further evidence of Class I and Class II transposable element-like sequences. Phylogenetic analysis placed M. vimineum with other Microstegium species, excluding M. nudum, but with weak support. Analysis of polymorphic sites across 112 accessions of M. vimineum from the native and invasive ranges revealed a complex invasion history.

Conclusions

We present an in-depth analysis of mitogenome structure, content, phylogenetic relationships, and range-wide genomic variation in M. vimineum's invasive US range. The mitogenome of M. vimineum is typical of other andropogonoid grasses, yet mitochondrial sequence variation across the invasive and native ranges is extensive. Our findings suggest multiple introductions to the US over the last century, with subsequent spread, secondary contact, long-distance dispersal, and possibly post-invasion selection on awn phenotypes. Efforts to produce genomic resources for invasive species, including sequenced mitochondrial genomes, will continue to provide tools for their effective management, and to help predict and prevent future invasions.

The relationship between Invasive Alien Solanum elaeagnifolium Cav. characters and impacts in different habitats

Invasive alien plants are one of the most serious threats to agriculture. The growth traits of Solanum elaeagnifolium Cav. in crops and their demographics in invaded vs non-invaded communities were examined. The majority of S. elaeagnifolium germination was observed in the spring compared to the summer. Five stages were distinguished, which started with a short time of seedling and juvenile stages, extended flowering, and fruiting stages, and seed dispersion in the winter season. An increase in shoots/roots ratio, leaf area ratio and leaf mass fraction during growth with the varied rate was proved. The accumulation coefficient of dry mass exceeded 0.93 and was significant (P > 0.001) with great variability within plant parts, and stage intervals. While the high growth rate is influenced by the stages and habitats. The recipient communities are affected negatively by S. elaeagnifolium invasion which is associated with lower diversity, richness, and evenness vs non-invaded communities. High similarities were found in the invaded area and communities. Finally, high and varied growth and plasticity of S. elaeagnifolium characterized their invasion behavior via different habitats. There were suitable determinants indices of diversity that can be used in the comparison between invaded and non-invaded communities. This knowledge may be useful for use in agro-environment protection and to improve the management methods of invasive alien species.

Human-mediated dispersal drives the spread of the spotted lanternfly (Lycorma delicatula)

The spotted lanternfly (Lycorma delicatula) is a novel invasive insect from Asia now established and spreading throughout the United States. This species is of particular concern given its ability to decimate important crops such as grapes, fruit trees, as well as native hardwood trees. Since its initial detection in Berks County, Pennsylvania in 2014, spotted lanternfly infestations have been detected in 130 counties (87 under quarantine) within Connecticut, Delaware, Indiana, Maryland, New Jersey, New York, Ohio, Virginia, and West Virginia. Compounding this invasion is the associated proliferation and widespread distribution of the spotted lanternfly's preferred host plant, the tree-of-heaven (Ailanthus altissima). While alternate host plant species have been observed, the tree-of-heaven which thrives in disturbed and human-dominated areas (e.g., along roads and railways) is likely facilitating the population growth rates of spotted lanternfly. We simulated the population and spread dynamics of the spotted lanternfly throughout the mid-Atlantic USA to help determine areas of risk and inform continued monitoring and control efforts. We tested the prediction that spotted lanternfly spread is driven by human-mediated dispersal using agent-based models that incorporated information on its life-history traits, habitat suitability, and movement and natural dispersal behavior. Overwhelmingly, our results suggest that human-mediated dispersal (e.g., cars, trucks, and trains) is driving the observed spread dynamics and distribution of the spotted lanternfly throughout the eastern USA. Our findings should encourage future surveys to focus on human-mediated dispersal of egg masses and adult spotted lanternflies (e.g., attachment to car or transported substrates) to better monitor and control this economically and ecologically important invasive species.

Genetic Signature of Pinctada fucata Inferred from Population Genomics: Source Tracking of the Invasion in Mischief Reef of Nansha Islands

Among the anthropogenic stresses that marine ecosystems face, biological invasions are one of the major threats. Recently, as a result of increasingly intense anthropogenic disturbance, numerous marine species have been introduced to their non-native ranges. However, many introduced species have uncertain original sources. This prevents the design and establishment of methods for controlling or preventing these introduced species. In the present study, genomic sequencing and population genetic analysis were performed to detect the geographic origin of the introduced Pinctada fucata population in the Mischief Reef of the South China Sea. The results of population genetic structure analysis showed a close relationship between the Mischief Reef introduced population and the Lingshui population, indicating that Lingshui may be the potential geographical origin. Furthermore, lower heterozygosity and nucleotide diversity were observed in the introduced population in Mischief Reef, indicating lower genetic diversity than in other native populations. We also identified some selected genomic regions and genes of the introduced population, including genes related to temperature and salinity tolerance. These genes may play important roles in the adaptation of the introduced population. Our study will improve our understanding of the invasion history of the P. fucata population. Furthermore, the results of the present study will also facilitate further control and prevention of invasion in Mischief Reef, South China Sea.

Plasticity in oviposition and foraging behavior in the invasive pest Drosophila suzukii across natural and agricultural landscapes

The effects and extent of the impacts of agricultural insect pests in and around cropping systems is a rich field of study. However, little research exists on the presence and consequence of pest insects in undisturbed landscapes distant from crop hosts. Research in such areas may yield novel or key insights on pest behavior or ecology that is not evident from agroecosystem-based studies. Using the invasive fruit pest Drosophila suzukii (Matsumura) as a case study, we investigated the presence and resource use patterns of this agricultural pest in wild blackberries growing within the southern Appalachian Mountain range of North Carolina over 2 years. We found D. suzukii throughout the sampled range with higher levels of infestation (D. suzukii eggs/g fruit) in all ripeness stages in natural areas when compared with cultivated blackberry samples, but especially in under-ripe fruit. We also explored a direct comparison of oviposition preference between wild and cultivated fruit and found higher oviposition in wild berries when equal weights of fruit were offered, but oviposition was higher in cultivated berries when fruit number was equal. Forest populations laid more eggs in unripe wild-grown blackberries throughout the year than populations infesting cultivated berries. This suggests D. suzukii may change its oviposition and foraging behavior in relation to fruit type. Additionally, as D. suzukii exploits a common forest fruit prior to ripeness, further research is needed to explore how this affects wild food web dynamics and spillover to regional agroecosystems.

Genetic variation of Amaranthus retroflexus L. and Chenopodium album L. (Amaranthaceae) suggests multiple independent introductions into Iran

Amaranthus retroflexus L. and Chenopodium album L. (Amaranthaceae) are weedy plants that cause severe ecological and economic damage. In this study, we collected DNA from three different countries and assessed genetic diversity using inter-simple sequence repeat (ISSR) markers. Our analysis shows both weed species have low genetic diversity within a population and high genetic diversity among populations, as well as a low value of gene flow among the populations. UPGMA clustering and principal coordinate analysis indicate four distinct groups for A. retroflexus L. and C. album L. exist. We detected significant isolation-by-distance for A. retroflexus L. and no significant correlation for C.album L. These conclusions are based data from 13 ISSR primers where the average percentage of polymorphism produced was 98.46% for A. retroflexus L. and 74.81% for C. album L.These data suggest that each population was independently introduced to the location from which it was sampled and these noxious weeds come armed with considerable genetic variability giving them the opportunity to manifest myriad traits that could be used to avoid management practices. Our results, albeit not definitive about this issue, do not support the native status of C. album L. in Iran.

A simulation-based evaluation of methods for estimating census population size of terrestrial game species from genetically-identified parent-offspring pairs

Estimates of wildlife population size are critical for conservation and management, but accurate estimates are difficult to obtain for many species. Several methods have recently been developed that estimate abundance using kinship relationships observed in genetic samples, particularly parent-offspring pairs. While these methods are similar to traditional Capture-Mark-Recapture, they do not need physical recapture, as individuals are considered recaptured if a sample contains one or more close relatives. This makes methods based on genetically-identified parent-offspring pairs particularly interesting for species for which releasing marked animals back into the population is not desirable or not possible (e.g., harvested fish or game species). However, while these methods have successfully been applied in commercially important fish species, in the absence of life-history data, they are making several assumptions unlikely to be met for harvested terrestrial species. They assume that a sample contains only one generation of parents and one generation of juveniles of the year, while more than two generations can coexist in the hunting bags of long-lived species, or that the sampling probability is the same for each individual, an assumption that is violated when fecundity and/or survival depend on sex or other individual traits. In order to assess the usefulness of kin-based methods to estimate population sizes of terrestrial game species, we simulated population pedigrees of two different species with contrasting demographic strategies (wild boar and red deer), applied four different methods and compared the accuracy and precision of their estimates. We also performed a sensitivity analysis, simulating population pedigrees with varying fecundity characteristics and various levels of harvesting to identify optimal conditions of applicability of each method. We showed that all these methods reached the required levels of accuracy and precision to be effective in wildlife management under simulated circumstances (i.e., for species within a given range of fecundity and for a given range of sampling intensity), while being robust to fecundity variation. Despite the potential usefulness of the methods for terrestrial game species, care is needed as several biases linked to hunting practices still need to be investigated (e.g., when hunting bags are biased toward a particular group of individuals).

Population genomic insights into invasion success in a polyphagous agricultural pest, Halyomorpha halys

Invasive species are increasingly threatening ecosystems and agriculture by rapidly expanding their range and adapting to environmental and human-imposed selective pressures. The genomic mechanisms that underlie such rapid changes remain unclear, especially for agriculturally important pests. Here, we used genome-wide polymorphisms derived from native, invasive, and intercepted samples and populations of the brown marmorated stink bug (BMSB), Halyomorpha halys, to gain insights into population genomics processes that have promoted the successful global invasion of this polyphagous pest. Our analysis demonstrated that BMSB exhibits spatial structure but admixture rates are high among introduced populations, resulting in similar levels of genomic diversity across native and introduced populations. These spatial genomic patterns suggest a complex invasion scenario, potentially with multiple bridgehead events, posing a challenge for accurately assigning BMSB incursions to their source using reduced-representation genomic data. By associating allele frequencies with the invasion status of BMSB populations, we found significantly differentiated single nucleotide polymorphisms (SNPs) located in close proximity to genes for insecticide resistance and olfaction. Comparing variations in allele frequencies among populations for outlier SNPs suggests that BMSB invasion success has probably evolved from standing genetic variation. In addition to being a major nuisance of households, BMSB has caused significant economic losses to agriculture in recent years and continues to expand its range. Despite no record of BMSB insecticide resistance to date, our results show high capacity for potential evolution of such traits, highlighting the need for future sustainable and targeted management strategies.

Population genetic structure of the globally introduced big-headed ant in Taiwan

Global commerce and transportation facilitate the spread of invasive species. The African big-headed ant, Pheidole megacephala (Fabricius), has achieved worldwide distribution through globalization. Since the late 19th century, Taiwan has served as a major seaport because of its strategic location. The population genetic structure of P. megacephala in Taiwan is likely to be shaped by international trade and migration between neighboring islands. In this study, we investigated the population genetics of P. megacephala colonies sampled from four geographical regions in Taiwan and elucidated the population genetic structures of P. megacephala sampled from Taiwan, Okinawa, and Hawaii. We observed a low genetic diversity of P. megacephala across regions in Taiwan. Moreover, we noted low regional genetic differentiation and did not observe isolation by distance, implying that long-distance jump dispersal might have played a crucial role in the spread of P. megacephala. We sequenced the partial cytochrome oxidase I gene and observed three mitochondrial haplotypes (TW1-TW3). TW1 and TW3 most likely originated from populations within the species' known invasive range, suggesting that secondary introduction is the predominant mode of introduction for this invasive ant. TW2 represents a novel haplotype that was previously unreported in other regions. P. megacephala populations from Taiwan, Okinawa, and Hawaii exhibited remarkable genetic similarity, which may reflect their relative geographic proximity and the historical connectedness of the Asia-Pacific region.

Interspecific Competitions between Frankliniella intonsa and Frankliniella occidentalis on Fresh Lentil Bean Pods and Pepper Plants

BACKGROUND

Flower thrips (Frankliniella intonsa, IFT) and west flower thrips (Frankliniella occidentalis, WFT) are often found together on the host plant in China. WFT is an important invasive species that seems to outcompete the native IFT. In order to clarify the interspecific competitions between the two thrips, this study measured the population development of IFT and WFT under sexual and parthenogenetic reproductive modes on two hosts (fresh lentil bean pods with/without honey and pepper plants at seedling/flowering stages) in the laboratory.

RESULTS

When reared on fresh lentil bean pods (with/without honey), WFT population size was lower in mixed species populations compared to single species populations but the presence of WFT had nor negative effect on IFT population size. These results were dependent of the reproductive mode. When honey was supplied, the ratio of female-to-male in the progeny of WFT produced under sexual reproductive mode increased significantly in the presence of IFT. On pepper seedlings, mixed populations were more favorable to the population development of IFT at the seedling stage, but more favorable to WFT at the flowering stage.

CONCLUSIONS

In the early stage of WFT invasion and colonization, the emergence of flowering and honey (nectar) sources may have a positive effect on the population development of WFT.

The Feeding Behaviour of Gall Midge Larvae and Its Implications for Biocontrol of the Giant Reed: Insights from Stable Isotope Analysis

The gall midge Lasioptera donacis, whose larval stage interferes with the reed's leaf development, is a potential candidate agent for the biological control of Arundo donax. Reed infestation is always associated with the presence of a saprophytic fungus, Arthrinium arundinis, which is believed to provide food for the larvae. Larvae also interact with a parasitic nematode, Tripius gyraloura, which can be considered its natural enemy. To deepen our knowledge of the plant-fungus-insect trophic interactions and to understand the effects of the nematode on midge larval feeding behaviour, we applied stable isotope analysis, one of the most effective methods for investigating animal feeding preferences in various contexts. The results showed that on average the fungus accounted for 65% of the diet of the midge larvae, which however consumed the reed and the fungus in variable proportions depending on reed quality (expressed as the C:N ratio). No differences in feeding behaviour were observed between parasitised and non-parasitised midge larvae, indicating that nematodes have no effect in this regard. Due to its trophic habits, L. donacis could be an effective control agent of A. donax and these results need to be considered when implementing biological control measures.

Population genetics reveal multiple independent invasions of Spodoptera frugiperda (Lepidoptera: Noctuidae) in China

The fall armyworm (Spodoptera frugiperda), a destructive pest that originated in South and North America, spread to China in early 2019. Controlling this invasive pest requires an understanding of its population structure and migration patterns, yet the invasion genetics of Chinese S. frugiperda is not clear. Here, using the mitochondrial cytochrome oxidase subunit I (COI) gene, triose phosphate isomerase (Tpi) gene and eight microsatellite loci, we investigated genetic structure and genetic diversity of 16 S. frugiperda populations in China. The Tpi locus identified most S. frugiperda populations as the corn-strains, and a few were heterozygous strains. The microsatellite loci revealed that the genetic diversity of this pest in China was lower than that in South America. Furthermore, we found moderate differentiation among the populations, distinct genetic structures between adjacent populations and abundant genetic resources in the S. frugiperda populations from China sampled across 2 years. The survival rate of S. frugiperda was significantly higher when it was fed on corn leaves than on rice leaves, and the larval stage mortality rate was the highest under both treatments. Our results showed that S. frugiperda probably invaded China via multiple independent introductions and careful pesticide control, continuous monitoring and further studies will be needed to minimize its potential future outbreak.

Population genetics of an invasive mosquito vector, Aedes albopictus in the Northeastern USA

The Asian tiger mosquito (Aedes albopictus) arrived in the USA in the 1980’s and rapidly spread throughout eastern USA within a decade. The predicted northern edge of its overwintering distribution on the East Coast of the USA roughly falls across New York, Connecticut, and Massachusetts, where the species has been recorded as early as 2000. It is unclear whether Ae. albopictus populations have become established and survive the cold winters in these areas or are recolonized every year. We genotyped and analyzed populations of Ae. albopictus from the northeast USA using 15 microsatellite markers and compared them with other populations across the country and to representatives of the major global genetic clades to investigate their connectivity and stability. Founder effects or bottlenecks were rare at the northern range of the Ae. albopictus distribution in the northeastern USA, with populations displaying high levels of genetic diversity and connectivity along the East Coast. There is no evidence of population turnover in Connecticut during the course of three consecutive years, with consistent genetic structure throughout this period. Overall, these results support the presence of established populations of Ae. albopictus in New York, Connecticut, and Massachusetts, successfully overwintering and migrating in large numbers. Given the stability and interconnectedness of these populations, Ae. albopictus has the potential to continue to proliferate and expand its range northward under mean warming conditions of climate change. Efforts to control Ae. albopictus in these areas should thus focus on vector suppression rather than eradication strategies, as local populations have become firmly established and are expected to reemerge every summer.

Genetic diversity pattern reveals the primary determinant of burcucumber (Sicyos angulatus L.) invasion in Korea

Biological invasion is a complex process associated with propagule pressure, dispersal ability, environmental constraints, and human interventions, which leave genetic signatures. The population genetics of an invasive species thus provides invaluable insights into the patterns of invasion. Burcucumber, one of the most detrimental weeds for soybean production in US, has recently colonized Korea and rapidly spread posing a great threat to the natural ecosystem. We aim to infer the determinants of the rapid burcucumber invasion by examining the genetic diversity, demography, and spread pattern with advanced genomic tools. We employed 2,696 genome-wide single-nucleotide polymorphisms to assess the level of diversity and the spatial pattern associated with the landscape factors and to infer the demographic changes of 24 populations (364 genotypes) across four major river basins with the east coastal streams in South Korea. Through the approximate Bayesian computation, we inferred the likely invasion scenario of burcucumber in Korea. The landscape genetics approach adopting the circuit theory and MaxEnt model was applied to determine the landscape contributors. Our data suggested that most populations have experienced population bottlenecks, which led to lowered within-population genetic diversity and inflated population divergences. Burcucumber colonization in Korea has strongly been affected by demographic bottlenecks and multiple introductions, whereas environmental factors were not the primary determinant of the invasion. Our work highlighted the significance of preventing secondary introductions, particularly for aggressive weedy plants such as the burcucumber.

Designing a surveillance program for early detection of alien plants and insects in Norway

Naturalized species of alien plants and animals comprise < 3% of biodiversity recorded in Norway but have had major impacts on natural ecosystems through displacement of native species. Encroachment of alien species has been especially problematic for coastal sites close to transport facilities and urban areas with high density housing. The goal of our field project was to design and test a surveillance program for early detection of alien species of vascular plants and terrestrial insects at the first phase of establishment in natural areas. In our 3-year project (2018–2020), we sampled 60 study plots in three counties in the Oslofjord region of southern Norway. Study plots (6.25 ha) were selected by two criteria: manual selection based on expert opinion (27 plots) or by random selection based on weights from a hotspot analysis of occurrence of alien species (33 plots). Vascular plants were surveyed by two experienced botanists who found a total of 239 alien species of vascular plants in 95 rounds of surveys. Insects and other invertebrates were captured with a single Malaise trap per site, with 3–4 rounds of repeated sampling. We used DNA-metabarcoding to identify invertebrates based on DNA extractions from crushed insects or from the preservative media. Over 3500 invertebrate taxa were detected in 255 rounds of sampling. We recorded 20 alien species of known risk, and 115 species that were new to Norway, including several ‘doorknocker’ species identified by previous risk assessments. We modeled the probabilities of occupancy (ψ) and detection (p) with occupancy models with repeated visits by multiple observers (vascular plants) or multiple rounds of sampling (insects). The two probabilities covaried with risk category for alien organisms and both were low for species categorized as no known or low risk (range = 0.052–0.326) but were higher for species categorized as severe risk (range = 0.318–0.651). Selecting sites at random or manually did not improve the probability of finding novel alien species, but occupancy had a weak positive relationship with housing density for some categories of alien plants and insects. We used our empirical estimates to test alternative sampling designs that would minimize the combined variance of occupancy and detection (A-optimality criterion). Sampling designs with 8–10 visits per site were best for surveillance of new alien species if the probabilities of occupancy and detection were both low, and provided low conditional probabilities of site occupancy ($$\hat{\psi }_{condl}$$ ψ ^ condl ≤ 0.032) and a high probabilities of cumulative detection ($$\hat{p}*$$ p ^ ∗  ≥ 0.943). Our field results demonstrate that early detection is feasible as a key component of a national surveillance program based on early detection and rapid response.

Patterns of Performance Variation Between Animal Hybrids and their Parents: A Meta-analysis

Hybridization is a widespread phenomenon in animals, and hybrid heterosis/breakdown could be key processes determining the evolutionary dynamics of hybrids. Indeed, hybrids are not consistently disadvantaged compared to the parental lineages, as was historically assumed. Multiple processes could lead to performance differences between parental lineages and their hybrids. Despite many studies evaluated the performance of hybrids, a quantitative synthesis is required to assess the general pattern. Here we used meta-analytic and meta-regression approaches to quantify the fitness differences between parental lineages and their hybrids, and to identify possible processes that could lead to these differences. Specifically, we tested biological and methodological parameters that could determine differences in performance between hybrids and parental lineages. Hybrid performance was extremely variable across studies, being often significantly higher or lower compared to the mean performance of their parents. Nevertheless, the averaged hybrid performance was similar to the fitness of parental lineages, with differences across studies related to how performance was assessed. Genetic divergence between parental lineages, and the approach used to identify hybrids were the parameters most strongly related to variation in hybrid performance. Performance was lower for hybrids between distantly related lineages. Furthermore, study settings and the use of imprecise approaches for hybrid identification (e.g. morphology-based) can bias assessments of performance. Studies performed on wild populations and using genetic approaches for hybrid identification detected more often a decreased hybrid performance, compared to laboratory studies. We highlight the importance of appropriate settings for a realistic understanding of the evolutionary impacts of hybridization.

Surveillance for gastrointestinal, subcutaneous, and ectoparasites of invasive North American raccoons (Procyon lotor) in central Spain

The American raccoon (Procyon lotor) is an invasive meso-carnivore which has been introduced and established in many European countries. Although the presence of the raccoon in the Iberian Peninsula was confirmed around 20 years ago, there are few data on pathogens of these animals in this region. For this work, 72 American raccoons from two subpopulations in the central region of the Iberian Peninsula were examined for selected parasites. Ectoparasite species richness (both fleas and ticks) increased during the sampling season and was highest in the Henares subpopulation and on males. Similarly, ectoparasite abundance increased during the sampling season and was highest in Henares and on adult raccoons. Four species of ticks were detected including Rhipicephalus pusillus (71%), followed by R. sanguineus sensu lato (24%), Ixodes ventalloi (3%), and Dermacentor marginatus (1.4%). Four species of fleas were detected including Pulex irritans (44%), Ctenocephalides felis (3%), C. canis (1.4%), and Paraceras melis (1.4%) infestations. A subset of raccoons (n = 56) was examined for intestinal parasites; low prevalence and diversity were found including Strongyloides procyonis (4%), Dilepis sp. (5%), Plagiorchis sp. (2%), and Moniliformis moniliformis (2%). Importantly, Baylisascaris procyonis was not found. Finally, no subcutaneous nematodes (i.e., Dracunculus and Dirofilaria spp.) were found in the 56 raccoons examined. The results of this work show that the invasive North American raccoons currently are infected with few endoparasites but are commonly infested with native ectoparasites, several of which can transmit pathogens relevant for public and veterinary health. However, the geographically distinct populations of raccoons in Spain have different introduction histories, thus additional surveillance for parasites is warranted.

Co-introduction of Dolicirroplectanum lacustre, a monogenean gill parasite of the invasive Nile perch Lates niloticus: intraspecific diversification and mitonuclear discordance in native versus introduced areas

The Nile perch (Lates niloticus) is a notorious invasive species. The introductions of Nile perch into several lakes and rivers in the Lake Victoria region led to the impoverishment of trophic food webs, particularly well documented in Lake Victoria. Additionally, its parasites were co-introduced, including Dolicirroplectanum lacustre (Monogenea, Diplectanidae). Dolicirroplectanum lacustre is the single monogenean gill parasite of latid fishes (Lates spp.) inhabiting several major African freshwater systems. We examined the intra-specific diversification of D. lacustre from Lates niloticus in Lake Albert, Uganda (native range) and Lake Victoria (introduced range) by assessing morphological and genetic differentiation, and microhabitat preference. We expected reduced morphological and genetic diversity for D. lacustre in Lake Victoria compared with Lake Albert, as a result of the historical introductions. We found that D. lacustre displayed high morphological variability within and between African freshwaters, with two morphotypes identified, as in former studies. The single shared morphotype between Lake Albert and Lake Victoria displayed similar levels of haplotype and nucleotide diversity between the lakes. Mitonuclear discordance within the morphotypes of D. lacustre indicates an incomplete reproductive barrier between the morphotypes. The diversification in the mitochondrial gene portion is directly linked with the morphotypes, while the nuclear gene portions indicate conspecificity. Based on our results, we reported reduced genetic and morphological diversity, potentially being a result of a founder effect in Lake Victoria.

Natural Populations from the Phytophthora palustris Complex Show a High Diversity and Abundance of ssRNA and dsRNA Viruses

We explored the virome of the “Phytophthora palustris complex”, a group of aquatic specialists geographically limited to Southeast and East Asia, the native origin of many destructive invasive forest Phytophthora spp. Based on high-throughput sequencing (RNAseq) of 112 isolates of “P. palustris” collected from rivers, mangroves, and ponds, and natural forests in subtropical and tropical areas in Indonesia, Taiwan, and Japan, 52 putative viruses were identified, which, to varying degrees, were phylogenetically related to the families Botybirnaviridae, Narnaviridae, Tombusviridae, and Totiviridae, and the order Bunyavirales. The prevalence of all viruses in their hosts was investigated and confirmed by RT-PCR. The rich virus composition, high abundance, and distribution discovered in our study indicate that viruses are naturally infecting taxa from the “P. palustris complex” in their natural niche, and that they are predominant members of the host cellular environment. Certain Indonesian localities are the viruses’ hotspots and particular “P. palustris” isolates show complex multiviral infections. This study defines the first bi-segmented bunya-like virus together with the first tombus-like and botybirna-like viruses in the genus Phytophthora and provides insights into the spread and evolution of RNA viruses in the natural populations of an oomycete species.

Embryo, Relocation and Secondary Nests of the Invasive Species Vespa velutina in Galicia (NW Spain)

Invasive species become established in non-native areas due to their intrinsic characteristics and the ability to adapt to new environments. This work describes the characteristics of the nesting behavior of the invasive yellow-legged hornet (Vespa velutina nigrithorax) in Galicia (Northwest Spain). The first nest was detected in the area in 2012 and after that, the distribution pattern shows a species-invasion curve with slow progress at first but followed by rapid expansion. The nesting places for this hornet differ between the kinds of nests, while embryo nests are mainly found in buildings in spring, secondary nests are observed in vegetation in summer, autumn, and winter. The annual life cycle starts when the queen builds the embryo nests and starts to lay eggs. This leads to the emergence of the first workers, usually small in size, and sometimes a few males. After this stage, large nests called secondary nests are normally observed in most exposed sites. Relocation nests can also be observed; these are nests in the first stage of development presenting adults insects but without brood or meconium. The period of decline is characterized by the emergence of new queens and males, that are distinguishable even in the pupal stage, the appearance of two eggs per cell, and an irregular brood pattern.

Genetics reveals shifts in reproductive behaviour of the invasive bird parasite Philornis downsi collected from Darwin’s finch nests

Due to novel or dynamic fluctuations in environmental conditions and resources, host and parasite relationships can be subject to diverse selection pressures that may lead to significant changes during and after invasion of a parasite. Genomic analyses are useful for elucidating evolutionary processes in invasive parasites following their arrival to a new area and host. Philornis downsi (Diptera: Muscidae), the avian vampire fly, was introduced to the Galápagos Islands circa 1964 and has since spread across the archipelago, feeding on the blood of developing nestlings of endemic land birds. Since its discovery, there have been significant changes to the dynamics of P. downsi and its novel hosts, such as shifting mortality rates and changing oviposition behaviour, however no temporal genetic studies have been conducted. We collected P. downsi from nests and traps from a single island population over a 14-year period, and genotyped flies at 469 single nucleotide polymorphisms (SNPs) using restriction-site associated DNA sequencing (RADSeq). Despite significant genetic differentiation (FST) between years, there was no evidence for genetic clustering within or across four sampling years between 2006 and 2020, suggesting a lack of population isolation. Sibship reconstructions from P. downsi collected from 10 Darwin’s finch nests sampled in 2020 showed evidence for shifts in reproductive behaviour compared to a similar genetic analysis conducted in 2004–2006. Compared with this previous study, females mated with fewer males, individual females oviposited fewer offspring per nest, but more unique females oviposited per nest. These findings are important to consider within reproductive control techniques, and have fitness implications for both parasite evolution and host fitness.

Biotic resistance or invasional meltdown? Diversity reduces invasibility but not exotic dominance in southern California epibenthic communities

High community diversity may either prevent or promote the establishment of exotic species. The biotic resistance hypothesis holds that species-rich communities are more resistant to invasion than species-poor communities due to mechanisms including greater interspecific competition. Conversely, the invasional meltdown hypothesis proposes that greater exotic diversity increases invasibility via facilitative interactions between exotic species. To evaluate the degree to which biotic resistance or invasional meltdown influences marine community structure during the assembly period, we studied the development of marine epibenthic “fouling” communities at two southern California harbors. With a focus on sessile epibenthic species, we found that fewer exotic species established as total and exotic richness increased during community assembly and that this effect remained after accounting for space availability. We also found that changes in exotic abundance decreased over time. Throughout the assembly period, gains in exotic abundance were greatest when space was abundant and richness was low. Altogether, we found greater support for biotic resistance than invasional meltdown, suggesting that both native and exotic species contribute to biotic resistance during early development of these communities. However, our results indicate that biotic resistance may not always reduce the eventual dominance of exotic species.

Ternary network models for disturbed ecosystems

The complex network of interactions between species makes understanding the response of ecosystems to disturbances an enduring challenge. One commonplace way to deal with this complexity is to reduce the description of a species to a binary presence-absence variable. Though convenient, this limits the patterns of behaviours representable within such models. We address these shortcomings by considering discrete population models that expand species descriptions beyond the binary setting. Specifically, we focus on ternary (three-state) models which, alongside presence and absence, additionally permit species to become overabundant. We apply this ternary framework to the robustness analysis of model ecosystems and show that this expanded description permits the modelling of top-down extinction cascades emerging from consumer pressure or mesopredator release. Results therefore differ significantly from those seen in binary models, where such effects are absent. We also illustrate how this method opens up the modelling of ecosystem disturbances outside the scope of binary models, namely those in which species are externally raised to overabundance. Our method therefore has the potential to provide a richer description of ecosystem dynamics and their disturbances, while at the same time preserving the conceptual simplicity of familiar binary approaches.

Weedy and seedy: the rapid evolution of life-history characteristics in an introduced daisy

Despite the importance of life-history characteristics in determining a species' success, we still lack basic information about some fundamental life-history elements found across the life cycle of introduced plants. Our study assesses rapid evolutionary divergence in life-history characteristics of the beach daisy Arctotheca populifolia by comparing introduced Australian and source South African plants and measuring eight key variables including seed mass, germination, reproductive output and survival. This is the first study that compares the life history of an introduced plant species with its single original source population, providing a precise and powerful method for detecting evolutionary divergence. We found that introduced A. populifolia has evolved a suite of weedy life-history characteristics in less than 90 years: the introduced plants use a live-fast die-young strategy of germination and survival and produce significantly more inflorescences and more seeds that germinate faster. This knowledge adds to the remarkable data that we already have on the rapid evolutionary divergence occurring in the morphology, physiology and defence of this introduced plant and highlights the speed and scope of evolutionary divergence possible in plants. To fully understand and manage the future of our plant species, we must consider their potential for ongoing change in key aspects of life history.

Stay in shape: Assessing the adaptive potential of shell morphology and its sensitivity to temperature in the invasive New Zealand mud snail Potamopyrgus antipodarum through phenotypic plasticity and natural selection in Europe

Climate change may force organisms to adapt genetically or plastically to new environmental conditions. Invasive species show remarkable potential for rapid adaptation. The ovoviviparous New Zealand mud snail (NZMS), Potamopyrgus antipodarum, has successfully established across Europe with two clonally reproducing mitochondrial lineages since its arrival in the first half of the 19th century. Its remarkable variation in shell morphology was shown to be fitness relevant. We investigated the effects of temperature on shell morphology across 11 populations from Germany and the Iberian Peninsula in a common garden across three temperatures. We analyzed size and shape using geometric morphometrics. For both, we compared reaction norms and estimated heritabilities. For size, the interaction of temperature and haplotype explained about 50% of the total variance. We also observed more genotype by environment interactions indicating a higher degree of population differentiation than in shape. Across the three temperatures, size followed the expectations of the temperature‐size rule, with individuals growing larger in cold environments. Changes in shape may have compensated for changes in size affecting space for brooding embryos. Heritability estimates were relatively high. As indicated by the very low coefficients of variation for clonal repeatability (CV_A), they can probably not be compared in absolute terms. However, they showed some sensitivity to temperature, in haplotype t more so than in z, which was only found in Portugal. The low CV_A values indicate that genetic variation among European populations is still restricted with a low potential to react to selection. A considerable fraction of the genetic variation was due to differences between the clonal lineages. The NZMS has apparently not been long enough in Europe to accumulate significant genetic variation relevant for morphological adaptation. As temperature is obviously not the sole factor influencing shell morphology, their interaction will probably not be a factor limiting population persistence under a warming climate in Europe.