Trait differences between and within ranges of an invasive legume species

Novel ecological interactions can drive natural selection in non-native species and trait evolution may increase the likelihood of invasion. We can gain insight into the potential role of evolution in invasion success by comparing traits of successful individuals in the invasive range with the traits of individuals from the native range in order to determine which traits are most likely to allow species to overcome barriers to invasion. Here we used Medicago polymorpha , a non-native legume species from the Mediterranean that has invaded six continents around the world, to quantify differences in life history traits among genotypes collected from the native and invasive range and grown in a common greenhouse environment. We found significant differences in fruit and seed production and biomass allocation between invasive and native range genotypes. Invasive genotypes had greater fecundity, but invested more energy into belowground growth relative to native genotypes. Beyond the variation between ranges, we found additional variation among genotypes within each range in flowering phenology, total biomass, biomass allocation, and fecundity. We found non-linear relationships between some traits and fitness that were much stronger for plants from the invasive range. These trait differences between ranges suggest that stabilizing selection on biomass, resource allocation, and flowering phenology imposed during or after introduction of this species may increase invasion success.

Large Individual-Level Variability in Diel Activity and Depth Use for the Common Lionfish (Pterois miles)

The common lionfish, Pterois miles, a notoriously invasive species known for its harmful effect on native fish communities in the Atlantic Ocean, has recently begun spreading across the Mediterranean Sea. The wide niche breadth of the lionfish has been hypothesized to facilitate its invasion success. However, it is unclear to what extent this wide niche-breadth is associated with individual-level variation and repeatable behavior over time. Large individual-level behavioral variations may allow individuals to adapt quickly to local conditions, increasing the species’ chance of invasion success and complicating mitigation efforts. In this study, we used an acoustic telemetry system in P. miles’ native Red Sea environment to explore individual-level variation in depth preference and diel activity. A wide depth range may indicate an ability to tolerate a variety of biotic and abiotic conditions, and variability in diel activity may indicate an ability to exploit multiple diet sources. We found large individual-level variability in P. miles’ activity hours; although all tracked fish were active during both sunrise and sunset, certain individuals had prolonged activity hours to variable extents. Moreover, individuals often change their patterns over time, showing low repeatability. We also found that individuals had different depth preferences and commuted between shallow and deep waters over short periods of time. This study is one of the first to explore diel activity as an individual-level trait in wild fish. The variability found in depth and diel activity is likely one of the reasons P. miles has been so successful in invading the Mediterranean Sea. In addition, this variability may impact mitigation efforts within the Mediterranean Sea as nocturnal individuals from deeper waters might replenish diurnally culled shallow-water populations.

Interactive Regulations of Dynamic Methylation and Transcriptional Responses to Recurring Environmental Stresses During Biological Invasions

Deoxyribonucleic acid methylation and gene transcription have been proved as two underlying mechanisms involved in rapid plastic response to environmental stresses. However, it remains elusive on how DNA methylation regulates gene transcription under acute and recurring environmental challenges to form the stress memory, further contributing to invasion success during range expansions. Using a model invasive species Ciona robusta, we investigated the regulatory roles of DNA methylation on gene transcription and their contribution to the formation of stress memory at 30 genes under acute and recurring osmotic challenges simulated during the invasion process. We found the bimodal distribution of methylation level for the 68 mCpGs identified across all the genes after challenges, but only five sites were significantly correlated with the expression of their corresponding genes. These genes participated in the biological processes of Ca2+ transport and metabolism of lipid and proline. At the DNA methylation level, we found two early-responding and four tardy-responding sites of stress memory and these sites were functionally related to genes involved in the biosynthesis of proline, metabolism of lipid, and transport of taurine and Ca2+. At the transcriptional level, three tardy-responding and five early-responding memory genes were involved in the transport of ions, regulation of water channels, biosynthesis of taurine, and metabolism of lipid. Altogether, the findings here suggest that DNA methylation and gene transcription should work in concert to facilitate the formation of stress memory, thus further improving the performance of invaders under recurring environmental challenges during biological invasions.

Invasive slipper limpets Crepidula fornicata act like a sink, rather than source, of Vibrio spp.

A large knowledge gap exists regarding the disease profile and pathologic condition of the invasive, non-native, slipper limpet Crepidula fornicata. To help address this, we performed a yearlong health survey across two sites in South Wales UK, subtidal Swansea Bay and intertidal Milford Haven. In total, 1,800 limpets were screened systematically for haemolymph bacterial burdens using both general and vibrio-selective growth media (TSA +2% NaCl and TCBS, respectively), haemolymph (blood) inspection using microscopy, a PCR-based assay targeting Vibrio spp., and multi-tissue histology. Over 99% of haemolymph samples contained cultivable bacterial colony forming units, and 83% of limpets tested positive for the presence of vibrios via PCR (confirmed via Sanger sequencing). Vibrio presence did not vary greatly across sites, yet a strong temporal (seasonal) effect was observed - significantly higher bacterial loads during the summer. Binomial logistic regression models revealed larger (older) limpets were more likely to harbour vibrios, and the growth of bacteria on TCBS was a key predictor for PCR-based vibrio detection. Histological assessment of >340 animals revealed little evidence of inflammation, sepsis, or immune reactivity despite the gross bacterial numbers. We contend that slipper limpets are not susceptible to bacteriosis at either site surveyed, or do not to harbour vibrios known to be pathogenic to humans. The lack of susceptibility to local pathogenic bacteria may explain, in part, the invasion success of C. fornicata across this region.

Invasion genomics uncover contrasting scenarios of genetic diversity in a widespread marine invader

Invasion rates have increased in the past 100 y irrespective of international conventions. What characterizes a successful invasion event? And how does genetic diversity translate into invasion success? Employing a whole-genome perspective using one of the most successful marine invasive species world-wide as a model, we resolve temporal invasion dynamics during independent invasion events in Eurasia. We reveal complex regionally independent invasion histories including cases of recurrent translocations, time-limited translocations, and stepping-stone range expansions with severe bottlenecks within the same species. Irrespective of these different invasion dynamics, which lead to contrasting patterns of genetic diversity, all nonindigenous populations are similarly successful. This illustrates that genetic diversity, per se, is not necessarily the driving force behind invasion success. Other factors such as propagule pressure and repeated introductions are an important contribution to facilitate successful invasions. This calls into question the dominant paradigm of the genetic paradox of invasions, i.e., the successful establishment of nonindigenous populations with low levels of genetic diversity.

Dietary plasticity in an invasive species and implications for management: the case of the monk parakeet in a Mediterranean city

Behavioural flexibility may play a relevant role during invasion of a new habitat. A typical example of behavioural flexibility favouring invasion success refers to changes in foraging behaviour. Here we provide data on changes in the foraging strategies of monk parakeets Myiopsitta monachus over a period of 17 years (2001–2017) in Barcelona city. During this time, consumption of food on the ground increased by more than 25 % and the consumption of anthropogenic food increased by 8 %. Detailed information about the food consumed is provided. Feeding on the ground and consumption of low plants allow parakeets to reach not only anthropogenic food but also crops, thereby increasing the risk of crop damage as the invasion evolves. Early detection of damage to crops is crucial in order to prevent further harm, and makes the precautionary principle highly relevant.

Long-Term Coexistence of Two Invasive Vespid Wasps in NW Patagonia (Argentina)

In Patagonia (Argentina) two non-native vespid wasps became established in the last decades. Vespula germanica was first detected in 1980 while V. vulgaris arrived some 30 years later. Both species can have a strong negative impact on agriculture, natural environment and on outdoor human activities. Invasion success -the establishment and spread of a species- may be influenced negatively by the degree of interaction with the resident native community, and alien species already present. The sequential arrival of these two wasps allows us to understand key questions of invasion ecology. Additionally, recognizing the outcome of the invasion by vespids in Patagonia -a region lacking native social wasps-, may help plan species-focused mitigation and control strategies. We explored long term species coexistence through the deterministic Lotka-Volterra competition model, using site-specific field data on prey captured (to estimate niche overlap) and current nest densities in sites. Food items carried by workers were similar but there is some degree of segregation. V. germanica nest density in shared sites, and in sites without coexistence, were 3.14 and 3.5 respectively, being higher for V. vulgaris with 4.71 and 5.33. The model predicts stable co-existence of both species in the invaded range, yet a higher abundance of V. vulgaris should be expected. Added to evidence on other foraging behavioral attributes of both wasp species and the invasion patterns observed in other regions, it is likely that the prior presence of V. germanica does not contribute significantly to the biotic resistance of the invaded range for V. vulgaris