Nonnative species that cause damage to ecosystems to which they are introduced are considered in-vasive. Restoration of the original ecosystem after an invasive population has established is expensive and difficult but more likely to succeed when invasions are discovered early. Containment efforts to prevent the spread of known invasions also benefit from earlier knowledge of invaded sites. Environ-mental DNA (eDNA) techniques are emerging as a tool that can identify invasive species at a distinctly earlier time point than traditional methods of detection. I collected water samples from eight sites not known to be invaded by the freshwater New Zealand mud snail (NZMS). After filtering these samples to collect eDNA, I used a species-specific probe with qPCR to identify NZMS eDNA. I found evidence for NZMS invasion at five of the eight sites, with later physical confirmation of mud snails at one of these sites. This study is the first example of successful application of eDNA to detect new invasions of the freshwater New Zealand mud snail, setting the stage for further monitoring of at-risk sites to de-tect and control new invasions of this destructive snail.

L’étang de Berre est un écosystème lagunaire historiquement perturbé par de forts rejets industriels et par des apports importants en eau douce naturels et anthropiques (centrale hydroélectrique EDF). Alors que les politiques de réhabilitation initiées depuis 1994 commencent à enregistrer leurs premiers succès, l'introduction et la prolifération de Mnemiopsis leidyi en 2005 pourraient limiter leur efficacité. L’originalité de cette étude est d’associer océanographie et sociologie afin d’estimer l’impact de M. leidyi sur le fonctionnement de ce socio-écosystème. Nous avons pu montrer que la population de M. leidyi est capable de se maintenir sur une large gamme de températures (3°C-28°C) et de salinités (10-30), pour une quantité de carbone disponible > 3 µgC L-1, la température étant un facteur déterminant dans la dynamique de la population. L’absence Mnemiopsis au cours d’évènements froids et sa réapparition plusieurs mois après laissent penser soit à l’existence d’une zone refuge qui a été déterminée (étang de Vaine) favorable au maintien des cténaires. Les fortes proliférations de M. leidyi affectent principalement la pêche professionnelle (fort colmatage des filets, mutilation des prises, dégradation accélérée du matériel, augmentation de la pénibilité) induisant une perte économique annuelle estimée à 50 %. Dans le cadre interdisciplinaire, la compréhension des interactions biologiques et anthropiques a permis de montrer que Mnemiopsis présentait une entrave à la mise en œuvre des efforts de réhabilitation. / The Berre Lagoon is an ecosystem historically disturbed by strong industrial discharges and significant freshwaters inputs from both natural and anthropogenic (EDF hydroelectric power station) origins. While rehabilitation policies initiated in 1994 are already showing some success, the introduction and proliferation of Mnemiopsis leidyi since 2005 could limit their effectiveness. The originality of this study is to associate oceanography and sociology in order to estimate the impact of M. leidyi on the functioning of this socio-ecosystem. We were able to show that the population of M. leidyi is maintained within a large range of temperatures (3 °C-28 °C) and salinities (10-30), with a quantity of carbon available ~ 3 mg C L-1 or more, temperature being a determining factor in population dynamics. The absence of this ctenophore on during cold events and its recurrence several months later suggests either the existence of an external source or the presence of a refuge zone that has been determined (Vaine lagoon) favourable to the maintenance of the ctenophores. The strong proliferation of M. leidyi in the Berre lagoon mainly affects professional fishermen. The clogging of nets, the mutilation of catches, the accelerated degradation of the material and the increase in the strenuousness induce an annual economic loss estimated at 50 %. Here in our interdisciplinary framework, the understanding of the biological and the anthropogenic interactions has shown that Mnemiopsis is tempering with the implementation of the rehabilitation efforts.

Invasive species introductions are associated with negative economic and environmental impacts, including reductions in native species populations. Successful invasive species populations often grow rapidly and a new food web equilibrium is established. Invasive, predatory northern pike (Esox lucius; hereafter pike) were detected in 2010 in Utah Lake, UT, a highly-degraded ecosystem home to the endemic, endangered June sucker (Chasmistes liorus). Here we test whether pike predation could hinder the restoration efforts of June sucker using the number of June sucker consumed by pike at various population densities as our metric. More specifically, we considered pike density at which the population could consume all June sucker stocked a critical threshold. Currently the number of naturally recruited June sucker is drastically lower than the number stocked. Thus, the metric we used to determine whether the pike population could hinder the June sucker restoration efforts is the number of pike that could consume the number of June sucker stocked. We combined pike growth and foraging observations with an energy-budget, bioenergetics consumption model to quantify lake-wide pike predation on June sucker. We also used an age-structured density dependent population model to estimate the pike population growth trajectory under various mitigation scenarios. Of 125 pike, we found an average pike consumes 0.8-1.0% June sucker and 40% sport fish. According to our bioenergetics model simulations, a population of adult pike at a very high density (60 pike per hectare) has the potential to consume nearly 6 million age-0 June sucker per year, which is likely more June sucker consumed than exist in the environment. In addition, our model suggests that an adult pike density greater than 1.5 pike per hectare has the potential to consume all June sucker stocked annually. Our age-structured population model suggests the pike population will reach equilibrium around 2026 at between 8 and 12 adult pike per hectare with the potential to consume between 0.8 and 1.2 million age-0 June sucker per year, respectively. The growing pike population could hamper restoration efforts and threaten endangered June sucker, a population with a mere 2,000 adults, in jeopardy of extinction. Our findings not only inform pike management efforts, but also highlight the importance of allocating resources toward habitat restoration to provide refuge for juvenile June sucker from predation, preventing the spread of aquatic invasive species, and the need for aquatic invasive species education.

A site within San Timoteo Canyon was revisited, 13-14 years after treatment, to look at long-term effects of Arundo donax removal. The data obtained were used to determine whether A. donax had re-invaded, other non-native species had established the area, or if native species were able to grow in place of the removed A. donax. The previous removals included a combination of grinding large patches of A. donax and then foliar spraying, foliar spraying of uncut plants, and direct spraying of hand cut stems, depending upon the location and size of the plant. The effects of the A. donax removals within San Timoteo Canyon were analyzed in relation to new percent cover of the plant species, other more recent removals, and areas that did no experience removal procedures. The project included the use of data provided by the Inland Empire Resource Conservation District (IERCD) as well as the collection of data from randomized plots to generate plant species percent cover. Plant percent cover data analyzed for this paper had been collected from eight 15 by 15 foot randomly selected plots within an overall project site of 42.3 acres. Additional sites were used to investigate what can happen if A. donax is not removed from an area into which it has been introduced., the short-term effects of A. donax removal methods, and the role the ever-changing characteristics of riparian areas can play in their own restoration. These additional sites included aerial photographs supplied by IERCD of an ecologically similar area, a plot with a more recent A. donax removal date, as well as photographs and data of a site subject to natural recovery. Based on these comparisons it is concluded that the treatment methods used led to a lessened presence of A. donax, and that other invasive species did not grow in its place. Further, as the removal procedures within the project area occurred approximately 13 to 14 years prior, it can be concluded that there is no regrowth of A. donax and that many native species have been able to re-inhabit those areas previously infested by A. donax. The treatment methods used were successful without the need to continually disrupt the habitat and allowed for the habitat to recover naturally once the invasive species had been removed.

acase@tulane.edu

Herbivory can have many effects on plant fitness, including altering plant-pollinator interactions and sexual reproduction in angiosperms. Pollinator-mediated interactions may be impacted when herbivores alter plant traits, such as floral display size, that can influence pollinator visitation rates, and, ultimately, the reproductive component of plant fitness. Here I describe an investigation into the indirect effects of feeding by beetles released as a biological control agent, Galerucella calmariensis and G. pusilla, on plant-pollinator interactions and reproductive output in the invasive plant Lythrum salicaria L. (purple loosestrife). During the summer of 2011, three treatments (low, ambient and mechanical herbivory) were applied to 105 plants during the pre-flowering period of growth. At the onset of flowering, a series of pollinator observations were conducted over the course of approximately 1.5 weeks. Several aspects of floral display were affected by the herbivory treatments, including increased inflorescence and flower production in the ambient and mechanical herbivory treatments, relative to the low herbivory treatment. Treatment type did not have a significant effect on the number of pollinator foraging bouts, but had marginally significant effects on the number of flowers probed per pollinator foraging bout and per 30-minutes. Moreover, treatment had a significant effect on the number of switches among the inflorescences on a single plant. I discuss the possibility that the differences in pollinator visitation were mediated by differences in the architecture and the size of floral display. There were no detectable differences in fruit or seed production (i.e., female fitness) among treatments. However, as I discuss, differences in pollinator visitation may affect other unmeasured aspects of fitness, such as the level of inbreeding or the number of seeds sired through male function.

Biological invasions provide opportunities to study evolutionary processes occurring during contemporary time scales. Here, I combine a literature review of common garden studies of invasive plant species, with field and glasshouse experiments on populations of the outcrossing, perennial, wetland invader Lythrum salicaria (purple loosestrife - Lythraceae), to investigate the evolutionary genetics of local adaptation in reproductive and life-history traits. A review of 32 common garden studies of 28 introduced species identified previously unrecognized latitudinal clines in phenotypic traits in both native and introduced populations. To obtain direct evidence for clinal variation and local adaptation, I investigated populations of L. salicaria sampled along a latitudinal gradient of growing season length in eastern North America. Controlled pollinations of plants from 12 populations provided no evidence for the breakdown of self-incompatibility to self-compatibility towards the northern range limit. However, a quantitative genetic experiment involving 20 populations revealed latitudinal clines in population mean, variance and skew for days to flower and vegetative size. Broad-sense estimates of genetic variance were significant for most traits; however, strong inter-correlations among traits suggested that fitness trade-offs have constrained population divergence. The observed clines supported a model of selection for early flowering in northern populations constrained by a trade-off between age and size at flowering. A comparison of variance-covariance matrices of family and population means (G and D, respectively) of life-history traits demonstrated that populations have evolved in response to selection under genetic constraints, rather than through neutral processes. A reciprocal transplant experiment involving six populations and three common gardens spanning the latitudinal range provided direct evidence for local adaptation in flowering phenology. Populations maintained the same rank-order for time to flowering and vegetative size at each site, and southern populations had the highest fecundity at the southern site but the lowest at the northern site. Finally, a phenotypic selection analysis in each common garden involving 61 F2 families of crosses between a northern × southern populations confirmed that selection favours earlier flowering in northern populations. These results demonstrate that natural selection on reproductive phenology has accompanied the invasive spread of L. salicaria in eastern N. America.

Biological invasions provide opportunities to study evolutionary processes occurring during contemporary time scales. Here, I combine a literature review of common garden studies of invasive plant species, with field and glasshouse experiments on populations of the outcrossing, perennial, wetland invader Lythrum salicaria (purple loosestrife - Lythraceae), to investigate the evolutionary genetics of local adaptation in reproductive and life-history traits. A review of 32 common garden studies of 28 introduced species identified previously unrecognized latitudinal clines in phenotypic traits in both native and introduced populations. To obtain direct evidence for clinal variation and local adaptation, I investigated populations of L. salicaria sampled along a latitudinal gradient of growing season length in eastern North America. Controlled pollinations of plants from 12 populations provided no evidence for the breakdown of self-incompatibility to self-compatibility towards the northern range limit. However, a quantitative genetic experiment involving 20 populations revealed latitudinal clines in population mean, variance and skew for days to flower and vegetative size. Broad-sense estimates of genetic variance were significant for most traits; however, strong inter-correlations among traits suggested that fitness trade-offs have constrained population divergence. The observed clines supported a model of selection for early flowering in northern populations constrained by a trade-off between age and size at flowering. A comparison of variance-covariance matrices of family and population means (G and D, respectively) of life-history traits demonstrated that populations have evolved in response to selection under genetic constraints, rather than through neutral processes. A reciprocal transplant experiment involving six populations and three common gardens spanning the latitudinal range provided direct evidence for local adaptation in flowering phenology. Populations maintained the same rank-order for time to flowering and vegetative size at each site, and southern populations had the highest fecundity at the southern site but the lowest at the northern site. Finally, a phenotypic selection analysis in each common garden involving 61 F2 families of crosses between a northern × southern populations confirmed that selection favours earlier flowering in northern populations. These results demonstrate that natural selection on reproductive phenology has accompanied the invasive spread of L. salicaria in eastern N. America.

This study examined the existing, or potential, risk of invasion by street trees into an urban forested park (Breithaupt Park, a 32.5 hectare semi-forested park, and its surrounding residential neighbourhood in the City of Kitchener.). The primary research question is: What are the spatial distribution and dispersal patterns of street trees and park trees in urban areas? For street populations, height, crown spread, diameter at breast height (DBH), tree condition, trunk condition and foliage transparency were measured. Qualitative tree health indicators were used to gauge the condition of the street tree population only. For trees in Breithaupt Park, a point-quarter sampling method combined with a line-plot sampling method was used. There were 33 identified (and several unidentified) species of street trees and 24 identified species of forest trees. Acer platanoides was the most abundant street tree species, while Acer saccharum was the most abundant forest tree species. 52% of the street tree population and 9% of the forest tree population were exotic species; however, the exotics were mainly species not originating from the nearby streets (i.e. Rhamnus cathartica). Despite the well-established population of exotic invasive species such as Acer platanoides on the streets, spatial assessment of the nearby forested park revealed that relatively few exotic species had actually established there. Acer platanoides composed 1.9% of all trees, 3.2% of all saplings and 2.7% of all seedlings in the forest sample. The four possible sources of Acer platanoides seeds were trees planted on the street, trees planted in backyards, the leaf drop site in the parking lot of Breithaupt Park (only in the fall) and trees potentially planted directly in the forest. Explanations for the lack of invasion by Acer platanoides (in particular) include: 1) houses located between Acer platanoides street trees and Breithaupt Park functioning as a barrier to seed dispersal; 2) the highway traversing the northeast corner of the park; 3) the short length of time since Acer platanoides street trees reached their age of maturity to produce enough viable seeds to invade the forest and the lag time in the establishment phase; 4) unique park characteristics; and 5) opposing predominant wind directions. While Acer platanoides may be more invasive under different circumstances, it was concluded that Acer platanoides is not currently invading the park at a considerable rate but may be tending towards a future invasion. The main recommendations are: 1) to not cut down the Acer platanoides currently growing as street trees as they do not pose a high risk of invasion (though this is specific to the current study); 2) to manage the forest for invasive species and remove and restore the ecology of the forest as necessary; 3) to remove Acer platanoides currently growing in the forest; and 4) to replace dead street trees with non-invasive, hardy native trees instead of the historical planting of Acer platanoides and other exotics, in case the risk of invasion changes because of climate or urban design changes.

This study examined the existing, or potential, risk of invasion by street trees into an urban forested park (Breithaupt Park, a 32.5 hectare semi-forested park, and its surrounding residential neighbourhood in the City of Kitchener.). The primary research question is: What are the spatial distribution and dispersal patterns of street trees and park trees in urban areas? For street populations, height, crown spread, diameter at breast height (DBH), tree condition, trunk condition and foliage transparency were measured. Qualitative tree health indicators were used to gauge the condition of the street tree population only. For trees in Breithaupt Park, a point-quarter sampling method combined with a line-plot sampling method was used. There were 33 identified (and several unidentified) species of street trees and 24 identified species of forest trees. Acer platanoides was the most abundant street tree species, while Acer saccharum was the most abundant forest tree species. 52% of the street tree population and 9% of the forest tree population were exotic species; however, the exotics were mainly species not originating from the nearby streets (i.e. Rhamnus cathartica). Despite the well-established population of exotic invasive species such as Acer platanoides on the streets, spatial assessment of the nearby forested park revealed that relatively few exotic species had actually established there. Acer platanoides composed 1.9% of all trees, 3.2% of all saplings and 2.7% of all seedlings in the forest sample. The four possible sources of Acer platanoides seeds were trees planted on the street, trees planted in backyards, the leaf drop site in the parking lot of Breithaupt Park (only in the fall) and trees potentially planted directly in the forest. Explanations for the lack of invasion by Acer platanoides (in particular) include: 1) houses located between Acer platanoides street trees and Breithaupt Park functioning as a barrier to seed dispersal; 2) the highway traversing the northeast corner of the park; 3) the short length of time since Acer platanoides street trees reached their age of maturity to produce enough viable seeds to invade the forest and the lag time in the establishment phase; 4) unique park characteristics; and 5) opposing predominant wind directions. While Acer platanoides may be more invasive under different circumstances, it was concluded that Acer platanoides is not currently invading the park at a considerable rate but may be tending towards a future invasion. The main recommendations are: 1) to not cut down the Acer platanoides currently growing as street trees as they do not pose a high risk of invasion (though this is specific to the current study); 2) to manage the forest for invasive species and remove and restore the ecology of the forest as necessary; 3) to remove Acer platanoides currently growing in the forest; and 4) to replace dead street trees with non-invasive, hardy native trees instead of the historical planting of Acer platanoides and other exotics, in case the risk of invasion changes because of climate or urban design changes.