When invasion may not be harmful: niche relations in a lizard assemblage

Some studies have suggested that non‐native species invasions may threaten local diversity by creating homogenized environments. However, many studies have been based on limited or anecdotal data, and/or have failed to consider the influence of habitat modification together with possible influences of non‐native species on native ones. Hemidactylus mabouia (Squamata, Gekkonidae) likely invaded natural environments in Brazil hundreds of years ago. Yet, little is known about whether it affects native lizard fauna. We tested whether H. mabouia negatively influences native lizard species richness and abundance on a regional scale and locally through niche overlap. We analyzed species abundance and richness of nine lizard assemblages, in five of which H. mabouia occurred. We evaluated niche overlap of species in a lizard assemblage with high H. mabouia abundance through null models. Niche axes included spatial use, temporal activity and diet. Although species abundance did not differ among sites with and without the invasive species, the presence of H. mabouia seems constrained to the richer assemblages sampled. We observed significantly higher niche overlap in spatial (?_obs = 0.63; ?_exp = 0.37; P_obs ≥ P_exp = 0.0002) and trophic axes (?_obs = 0.46; ?_exp = 0.17; P_obs ≥ P_exp < 0.001), but not in activity. When we considered all axes (three‐dimensional niche), there was no overlapping among the lizard species. Our findings did not support the hypothesis that this non‐native species negatively influences other sympatric lizard species.     

Predation on the Invasive Copepod,Pseudodiaptomus forbesi,and Native Zooplankton in the Lower Columbia River: An Experimental Approach to Quantify Differences in Prey-Specific Feeding Rates

Invasive planktonic crustaceans have become a prominent feature of aquatic communities worldwide, yet their effects on food webs are not well known. The Asian calanoid copepod, Pseudodiaptomus forbesi, introduced to the Columbia River Estuary approximately 15 years ago, now dominates the late-summer zooplankton community, but its use by native aquatic predators is unknown. We investigated whether three species of planktivorous fishes (chinook salmon, three-spined stickleback, and northern pikeminnow) and one species of mysid exhibited higher feeding rates on native copepods and cladocerans relative to P. forbesi by conducting `single-prey’ feeding experiments and, additionally, examined selectivity for prey types with `two-prey’ feeding experiments. In single-prey experiments individual predator species showed no difference in feeding rates on native cyclopoid copepods (Cyclopidae spp.) relative to invasive P. forbesi, though wild-collected predators exhibited higher feeding rates on cyclopoids when considered in aggregate. In two-prey experiments, chinook salmon and northern pikeminnow both strongly selected native cladocerans (Daphnia retrocurva) over P. forbesi, and moreover, northern pikeminnow selected native Cyclopidae spp. over P. forbesi. On the other hand, in two-prey experiments, chinook salmon, three-spined stickleback and mysids were non- selective with respect to feeding on native cyclopoid copepods versus P. forbesi. Our results indicate that all four native predators in the Columbia River Estuary can consume the invasive copepod, P. forbesi, but that some predators select for native zooplankton over P. forbesi, most likely due to one (or both) of two possible underlying casual mechanisms: 1) differential taxon-specific prey motility and escape responses (calanoids > cyclopoids > daphnids) or 2) the invasive status of the zooplankton prey resulting in naivety, and thus lower feeding rates, of native predators feeding on invasive prey.     

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

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

Demographic Consequences of Predators on Prey: Trait and Density Mediated Effects on Mosquito Larvae in Containers

Predators may affect prey population growth and community diversity through density mediated lethal and trait mediated non-lethal effects that influence phenotypic traits of prey. We tested experimentally the roles of thinning the density of prey (lethality) in the absence of predator cues and density and trait mediated effects (lethality + intimidation) of predatory midge Corethrella appendiculata on competing native and invasive mosquito prey. Predator-mediated reductions in prey and density reductions in the absence of C. appendiculata resulted in lower percent survivorship to adulthood and estimates of the finite rate of increase (λ′) for invasive mosquito Aedes albopictus relative to that of controls. In most instances, thinning the density of prey in the absence, but not in the presence, of C. appendiculata cues resulted in lower survivorship to adulthood and λ′ for native mosquito Aedes triseriatus relative to that of controls. Together, these results suggested trait mediated effects of C. appendiculata specific to each species of mosquito prey. Release from intraspecific competition attributable to density reductions in the absence, but not in the presence, of C. appendiculata enhanced growth and lengthened adult lifespan relative to that of controls for A. albopictus but not A. triseriatus. These results show the importance of predator-mediated density and trait mediated effects on phenotypic traits and populations of invasive and native mosquitoes. Species-specific differences in the phenotypic responses of prey may be due, in part, to longer evolutionary history of C. appendiculata with A. triseriatus than A. albopictus.     

History of canids in Chile and impacts on prey adaptations

Artiodactyl prey species of Chile, especially guanacos (Lama guanicoe), are reported to be very susceptible to predation by pack‐hunting feral dogs. It has been previously suggested that guanacos and endemic South American deer may have evolved in the absence of pack‐hunting cursorial predators. However, the paleoecology of canid presence in southern South America and Chile is unclear. Here, we review the literature on South American and Chilean canids, their distributions, ecologies, and hunting behavior. We consider both wild and domestic canids, including Canis familiaris breeds. We establish two known antipredator defense behaviors of guanacos: predator inspection of ambush predators, for example, Puma concolor, and rushing at and kicking smaller cursorial predators, for example, Lycalopex culpaeus. We propose that since the late Pleistocene extinction of hypercarnivorous group‐hunting canids east of the Andes, there were no native species creating group‐hunting predation pressures on guanacos. Endemic deer of Chile may have never experienced group‐hunting selection pressure from native predators. Even hunting dogs (or other canids) used by indigenous groups in the far north and extreme south of Chile (and presumably the center as well) appear to have been used primarily within ambush hunting strategies. This may account for the susceptibility of guanacos and other prey species to feral dog attacks. We detail seven separate hypotheses that require further investigation in order to assess how best to respond to the threat posed by feral dogs to the conservation of native deer and camelids in Chile and other parts of South America.     

In situ adaptation and ecological release facilitate the occupied niche expansion of a non‐native Madagascan day gecko in Florida

AimTo investigate whether the frequently advocated climate‐matching species distribution modeling approach could predict the well‐characterized colonization of Florida by the Madagascar giant day gecko Phelsuma grandis.LocationMadagascar and Florida, USA.MethodsTo determine the climatic conditions associated with the native range of P. grandis, we used native‐range presence‐only records and Bioclim climatic data to build a Maxent species distribution model and projected the climatic thresholds of the native range onto Florida. We then built an analogous model using Florida presence‐only data and projected it onto Madagascar. We constructed a third model using native‐range presences for both P. grandis and the closely related parapatric species P. kochi.ResultsDespite performing well within the native range, our Madagascar Bioclim model failed to identify suitable climatic habitat currently occupied by P. grandis in Florida. The model constructed using Florida presences also failed to reflect the distribution in Madagascar by overpredicting distribution, especially in western areas occupied by P. kochi. The model built using the combined P. kochi/P. grandis dataset modestly improved the prediction of the range of P. grandis in Florida, thereby implying competitive exclusion of P. grandis by P. kochi from habitat within the former''s fundamental niche. These findings thus suggest ecological release of P. grandis in Florida. However, because ecological release cannot fully explain the divergent occupied niches of P. grandis in Madagascar versus Florida, our findings also demonstrate some degree of in situ adaptation in Florida.Main conclusionsOur models suggest that the discrepancy between the predicted and observed range of P. grandis in Florida is attributable to either in situ adaptation by P. grandis within Florida, or a combination of such in situ adaptation and competition with P. kochi in Madagascar. Our study demonstrates that climate‐matching species distribution models can severely underpredict the establishment risk posed by non‐native herpetofauna.     

Prey naïveté rather than enemy release dominates the relation of an invasive spider toward a native predator

Ecosystems may suffer from the impact of invasive species. Thus, understanding the mechanisms contributing to successful invasions is fundamental for limiting the effects of invasive species. Most intuitive, the enemy release hypothesis predicts that invasive species might be more successful in the exotic range than resident sympatric species owing to the absence of coevolution with native enemies. Here, we test the enemy release hypothesis for the invasion of Europe by the North American spider Mermessus trilobatus. We compare the susceptibility of invasive Mermessus trilobatus and a native species with similar life history to a shared predator with which both species commonly co‐occur in Europe. Contrary to our expectations, invasive Mermessus trilobatus were consumed three times more frequently by native predators than their native counterparts. Our study shows that invasive Mermessus trilobatus is more sensitive to a dominant native predator than local sympatric species. This suggests that the relation between the invasive spider and its native predator is dominated by prey naïveté rather than enemy release. Further studies investigating evolutionary and ecological processes behind the invasion success of Mermessus trilobatus, including testing natural parasites and rapid reproduction, are needed to explain its invasion success in Europe.     

Preliminary assessment of cavity‐nesting Hymenopterans in a low‐intensity agricultural landscape in Transylvania

In this study, our aim was to assess several traits of cavity‐nesting Hymenopteran taxa in a low‐intensity agricultural landscape in Transylvania. The study took place between May and August 2018 at eight study sites in the hilly mountainous central part of Romania, where the majority of the landscape is used for extensive farming or forestry. During the processing of the trap nest material, we recorded several traits regarding the nests of different cavity‐nesting Hymenopteran taxa and the spider prey found inside the nests of the spider‐hunting representatives of these taxa. We also evaluated the relationship between the edge density and proportion of low‐intensity agricultural areas surrounding the study sites and some of these traits.The majority of nests were built by the solitary wasp genus Trypoxylon, followed by the solitary wasp taxa Dipogon and Eumeninae. Solitary bees were much less common, with Hylaeus being the most abundant genus. In the nests of Trypoxylon, we mostly found spider prey from the family of Araneidae, followed by specimens from the families of Linyphiidae and Theridiidae. In the nests of Dipogon, we predominantly encountered spider prey from the family of Thomisidae. We found significant effects of low‐intensity agricultural areas for the genera of Auplopus, Megachile, Osmia, and the Thomisid prey of Dipogon. We also found that the spider prey of Trypoxylon was significantly more diverse at study sites with higher proportions of low‐intensity agricultural areas.Our results indicate that solitary bees seem to be more abundant in areas, where the influence of human activities is stronger, while solitary wasps seem to rather avoid these areas. Therefore, we suggest that future studies not only should put more effort into sampling in low‐intensity agricultural landscapes but also focus more on solitary wasp taxa, when sampling such an area.     

Dietary characterization of the endangered salt marsh harvest mouse and sympatric rodents using DNA metabarcoding

The salt marsh harvest mouse (Reithrodontomys raviventris; RERA) is an endangered species endemic to the coastal wetlands of the San Francisco Estuary, California. RERA are specialized to saline coastal wetlands, and their historical range has been severely impacted by landscape conversion and the introduction of non‐native plant and rodent species. A better understanding of their diet is needed to assess habitat quality, particularly in relation to potential competitors. We investigated three questions using DNA metabarcoding with ITS2 and trnL markers: (1) Do RERA specialize on the native plant, pickleweed (Salicornia pacifica), (2) Do RERA consume non‐native plants, and (3) What is the dietary niche breadth and overlap with three sympatric native and non‐native rodents? RERA diet was dominated by two plants, native Salicornia and non‐native salt bush (Atriplex spp.), but included 48 plant genera. RERA diet breadth was narrowest in fall, when they consumed the highest frequencies of Salicornia and Atriplex, and broadest in spring, when the frequencies of these two plants were lowest. Diet breadth was slightly lower for RERA than for co‐occurring species in pairwise comparisons. All four species consumed similarly high frequencies of wetland plants, but RERA consumed fewer grasses and upland plants, suggesting that it may be less suited to fragmented habitat than sympatric rodents. Diet overlap was lowest between RERA and the native California vole (Microtis californicus). In contrast, RERA diet overlapped substantially with the native western harvest mouse (R. megalotis) and non‐native house mouse (Mus musculus), suggesting potential for competition if these species become sufficiently abundant.     

Alien and native tree species having extrafloral nectaries as favorite hunting area for arboreal endemic Philippine tiger beetles (Coleoptera: Cicindelidae) in human‐disturbed habitat in Lanao del Sur Province,Mindanao, Philippines

To document a relation between abundance of arboreal, predatory tiger beetles, their ant prey, and extrafloral nectaries attracting the ants, we gathered data from more than 10 species of native and introduced trees and large, tree‐like perennial plants in Lanao del Sur Province, Mindanao, Philippines. All specimens of tiger beetles (two Tricondyla and two Neocollyris species, all endemic to the country) were noted on five tree species characterized by presence of extrafloral nectaries, including three alien/invasive and two native ones. Invasive Spathodea campanulata and native Hibiscus tiliaceus were the most inhabited ones (respectively, 56% and 19% of beetles). Presence of tiger beetles on these trees most probably depends on high abundance of ants, which are typical prey for arboreal Cicindelidae, while occurrence of ants can result from presence of extrafloral nectaries on different parts of the plants. This suggests a new mutualistic insect–plant interaction between native and invasive species.     

Adjustments in physiological and morphological traits suggest drought‐induced competitive release of some California plants

Drought and competition affect how morphological and physiological traits are expressed in plants. California plants were previously found to respond less negatively to resource limitation compared to invasive counterparts. In a glasshouse in Santa Cruz, CA, USA, we exposed five native California C₃ grassland species to episodic drought and competition (via five locally invasive species). We hypothesized that leaf morphology would be more affected by competition, and leaf photosynthetic gas exchange more so by drought, consistent with optimal partitioning and environmental filter theories. We expected that traits would exhibit trade‐offs along a spectrum for resource conservatism versus acquisition. Bromus carinatus had greater photosynthetic recovery, while Diplacus aurantiacus had lower percent loss of net assimilation (PLA) and intrinsic water‐use efficiency (iWUE) during drought and competition simultaneously compared to just drought. Stipa pulchra and Sidalcea malviflora gas exchange was unaffected by drought, and leaf morphology exhibited drought‐related adjustments. Lupinus nanus exhibited trait adjustments for competition but not drought. Functional traits sorted onto two principal components related to trade‐offs for resource conservatism versus acquisition, and for above‐ versus belowground allocation. In summary, morphological traits were affected by competition and drought, whereas physiological traits, like leaf gas exchange, were primarily affected by drought. The grassland plants we studied showed diverse responses to drought and competition with trait trade‐offs related to resource conservatism versus acquisition, and for above‐ versus belowground allocation consistent with optimal partitioning and environmental filter theories. Diplacus aurantiacus experienced competitive release based on greater iWUE and lower PLA when facing drought and competition.     

Match and mismatch: Integrating consumptive effects of predators,prey traits,and habitat selection in colonizing aquatic insects

Predators are a particularly critical component of habitat quality, as they affect survival, morphology, behavior, population size, and community structure through both consumptive and non‐consumptive effects. Non‐consumptive effects can often exceed consumptive effects, but their relative importance is undetermined in many systems. Our objective was to determine the consumptive and non‐consumptive effects of a predaceous aquatic insect, Notonecta irrorata, on colonizing aquatic beetles. We tested how N. irrorata affected survival and habitat selection of colonizing aquatic beetles, how beetle traits contributed to their vulnerability to predation by N. irrorata, and how combined consumptive and non‐consumptive effects affected populations and community structure. Predation vulnerabilities ranged from 0% to 95% mortality, with size, swimming, and exoskeleton traits generating species‐specific vulnerabilities. Habitat selection ranged from predator avoidance to preferentially colonizing predator patches. Attraction of Dytiscidae to N. irrorata may be a natural ecological trap given similar cues produced by these taxa. Hence, species‐specific habitat selection by prey can be either predator‐avoidance responses that reduce consumptive effects, or responses that magnify predator effects. Notonecta irrorata had both strong consumptive and non‐consumptive effects on populations and communities, while combined effects predicted even more distinct communities and populations across patches with or without predators. Our results illustrate that an aquatic invertebrate predator can have functionally unique consumptive effects on prey, attracting and repelling prey, while prey have functionally unique responses to predators. Determining species‐specific consumptive and non‐consumptive effects is important to understand patterns of species diversity across landscapes.     

Pricklier with the proper predator? Predator‐induced small‐scale changes of spinescence in Daphnia

Phenotypic plasticity in defensive traits is a common response of prey organisms to variable and unpredictable predation regimes and risks. Cladocerans of the genus Daphnia are keystone species in the food web of lentic freshwater bodies and are well known for their ability to express a large variety of inducible morphological defenses in response to invertebrate and vertebrate predator kairomones. The developed defenses render the daphnids less susceptible to predation. So far, primarily large‐scale morphological defenses, like helmets, crests, and tail‐spines, have been documented. However, less is known on whether the tiny spinules, rather inconspicuous traits which cover many Daphnia’s dorsal and ventral carapace margins, respond to predator kairomones, as well. For this reason, we investigated two Daphnia species (D. magna and D. longicephala) concerning their predator kairomone‐induced changes in dorsal and ventral spinules. Since these small, inconspicuous traits may only act as a defense against predatory invertebrates, with fine‐structured catching apparatuses, and not against vertebrate predators, we exposed them to both, an invertebrate (Triops cancriformis or Notontecta maculata) and a vertebrate predator (Leucaspius delineatus). Our results show that the length of these spinules as well as spinules‐covered areas vary, likely depending on the predator the prey is exposed to. We further present first indications of a Daphnia species‐specific elongation of the spinules and an increase of the spinules‐bearing areas. Although we cannot exclude that spinescence is altered because it is developmentally connected to changes in body shape in general, our results suggest that the inducible alterations to the spinule length and spinules‐covered areas disclose another level of predator‐induced changes in two common Daphnia species. The predator‐induced changes on this level together with the large‐scale and ultrastructural defensive traits may act as the overall morphological defense, adjusted to specific predator regimes in nature.     

Therapeutic stem cell‐derived alveolar‐like macrophages display bactericidal effects and resolve Pseudomonas aeruginosa‐induced lung injury

Bacterial lung infections lead to greater than 4 million deaths per year with antibiotic treatments driving an increase in antibiotic resistance and a need to establish new therapeutic approaches. Recently, we have generated mouse and rat stem cell‐derived alveolar‐like macrophages (ALMs), which like primary alveolar macrophages (1''AMs), phagocytose bacteria and promote airway repair. Our aim was to further characterize ALMs and determine their bactericidal capabilities. The characterization of ALMs showed that they share known 1''AM cell surface markers, but unlike 1''AMs are highly proliferative in vitro. ALMs effectively phagocytose and kill laboratory strains of P. aeruginosa (P.A.), E. coli (E.C.) and S. aureus, and clinical strains of P.A. In vivo, ALMs remain viable, adapt additional features of native 1''AMs, but proliferation is reduced. Mouse ALMs phagocytose P.A. and E.C. and rat ALMs phagocytose and kill P.A. within the lung 24 h post‐instillation. In a pre‐clinical model of P.A.‐induced lung injury, rat ALM administration mitigated weight loss and resolved lung injury observed seven days post‐instillation. Collectively, ALMs attenuate pulmonary bacterial infections and promote airway repair. ALMs could be utilized as an alternative or adjuvant therapy where current treatments are ineffective against antibiotic‐resistant bacteria or to enhance routine antibiotic delivery.     

Dietary analysis reveals differences in the prey use of two sympatric bat species

One mechanism for morphologically similar and sympatric species to avoid competition and facilitate coexistence is to feed on different prey items within different microhabitats. In the current study, we investigated and compared the diet of the two most common and similar‐sized bat species in Japan—Murina ussuriensis (Ognev, 1913) and Myotis ikonnikovi (Ognev, 1912)—to gain more knowledge about the degree of overlap in their diet and their foraging behavior. We found that both bat species consumed prey from the orders of Lepidoptera and Diptera most frequently, while the proportion of Dipterans was higher in the diet of M. ikonnikovi. Furthermore, we found a higher prey diversity in the diet of M. ikonnikovi compared to that of M. ussuriensis that might indicate that the former is a more generalist predator than the latter. In contrast, the diet of M. ussuriensis contained many Lepidopteran families. The higher probability of prey items likely captured via gleaning to occur in the diet of M. ussuriensis in contrast to M. ikonnikovi indicates that M. ussuriensis might switch between aerial‐hawking and gleaning modes of foraging behavior. We encourage further studies across various types of habitats and seasons to investigate the flexibility of the diet composition and foraging behavior of these two bat species.     

Genomic basis for an informed conservation management of Pelophylax water frogs in Luxembourg

Genetic identification methods have become increasingly important for species that are difficult to identify in the field. A case in point is Pelophylax water frogs. While their morphological determination is highly complex, they include species protected under EU law and some that are classified as invasive. Additionally, genetic data can provide insights into their complex breeding systems, which may or may not involve the reproductive dependency of one species on another. Here, we generate baseline data for water frog monitoring in Luxembourg. We applied a countrywide sampling approach and used SNPs generated by ddRAD sequencing to identify individuals and infer the breeding systems present in the country. We found Pelophylax lessonae and P. kl. esculentus throughout Luxembourg, mostly living in syntopy. In general, a reproductive dependency of P. kl. esculentus on P. lessonae (L‐E system) was revealed. Besides this general system, we detected triploid P. kl. esculentus in six ponds. This indicates a modified L‐E system with reproductive dependency of the triploids on the diploid P. kl. esculentus. The invasive P. cf. bedriagae was detected in three ponds in southern Luxembourg, with evidence for hybridization with native water frogs. In addition to the ddRAD data, we tested a simple genetic method for future monitoring based on the MND1 marker. It showed in almost all cases, an identical species identification as the ddRAD data and was successfully applied to DNA extracts from mouth swabs. Combining this method with our baseline data will enable informed choices for the protection of native water frog species in Luxembourg.     

Effect of plant VOCs and light intensity on growth and reproduction performance of an invasive and a native Phytolacca species in China

Invasive plants often pose great threats to the growth of co‐occurring native plant species. Identifying environmental factors that facilitate exotic plant invasion and native species decline are important. In this study, we measured the effects of plant volatile organic compounds (VOCs), light intensity, and their interactions on the growth and reproduction performance of indigenous Phytolacca acinosa, and invasive Phytolacca americana, which has largely replaced the former in China. VOCs of invasive P. americana and low light levels both had negative effects on P. acinosa morphological and reproductive traits (stem length, average leaf number, total number, and length of racemes), and biomass allocation (total biomass, and leaf and flower mass fraction); low light also affected photosynthesis‐related trait (specific leaf area) of P. acinosa. In contrast, VOCs of P. acinosa had no significant effect on P. americana, but low light levels adversely affected its morphological and reproductive traits (stem length, total number, and length of racemes) and biomass allocation (total biomass, stem, and leaf mass fraction). Interactions between plant VOCs and light intensity had no significant effects on P. acinosa or P. americana. Under all experimental treatments, stem length, average leaf area, total number, and length of racemes, Root/Shoot ratio, root and flower mass fraction of P. americana were higher than those of P. acinosa, while average leaf number, specific leaf area, and leaf mass fraction was lower. These results indicated that P. acinosa was sensitive to P. americana VOCs and low light, which might affect the growth of sympatric P. acinosa. P. americana was negatively influenced by low light, but higher plant height and more reproductive organ resource allocation relative to sympatric P. acinosa might contribute to invasion success.     

Existing and emerging high impact invasive species are characterized by higher functional responses than natives

Predicting ecological impacts of invasive species and identifying potentially damaging future invaders are research priorities. Since damage by invaders is characterized by their depletion of resources, comparisons of the ‘functional response’ (FR; resource uptake rate as a function of resource density) of invaders and natives might predict invader impact. We tested this by comparing FRs of the ecologically damaging ‘world''s worst’ invasive fish, the largemouth bass (Micropterus salmoides), with a native equivalent, the Cape kurper (Sandelia capensis), and an emerging invader, the sharptooth catfish (Clarias gariepinus), with the native river goby (Glossogobius callidus), in South Africa, a global invasion hotspot. Using tadpoles (Hyperolius marmoratus) as prey, we found that the invaders consumed significantly more than natives. Attack rates at low prey densities within invader/native comparisons reflected similarities in predatory strategies; however, both invasive species displayed significantly higher Type II FRs than the native comparators. This was driven by significantly lower prey handling times by invaders, resulting in significantly higher maximum feeding rates. The higher FRs of these invaders are thus congruent with, and can predict, their impacts on native communities. Comparative FRs may be a rapid and reliable method for predicting ecological impacts of emerging and future invasive species.     

Condition and size of the non‐native pikeperch Sander lucioperca (Linnaeus, 1758) in Portuguese river basins

We studied life‐history traits focusing on the growth and condition of the pikeperch Sander lucioperca to evaluate its phenotypic plasticity when introduced to new environments. Pikeperch is a non‐native fish introduced to Iberian freshwater fauna in 1998 that quickly spread to other river basins through human‐mediated activities, occupying now a wide variety of habitats along mainland Portugal. Condition (K and SMI), fork length at age, and length–weight relationships were studied for Portuguese populations. Pikeperch fork length for ages 1, 2, 3, and 4 was different between several populations. We applied generalized linear models (GLM) to study the influence of habitat type, latitude, altitude, time after first detection, and fish prey richness on pikeperch populations size at age 4 and condition. We observed higher condition values on populations from lower altitudes at lentic systems more recently introduced. But higher fork length at age 4 was found in populations from higher altitudes, on older populations with higher prey richness. Habitat type, time since first detection, and fish fauna composition are discussed as the main environmental factors explaining the observed phenotypic plasticity with concerns on predatory impact on native fauna.     

Propagule pressure and an invasion syndrome determine invasion success in a plant community model

The success of species invasions depends on multiple factors, including propagule pressure, disturbance, productivity, and the traits of native and non‐native species. While the importance of many of these determinants has already been investigated in relative isolation, they are rarely studied in combination. Here, we address this shortcoming by exploring the effect of the above‐listed factors on the success of invasions using an individual‐based mechanistic model. This approach enables us to explicitly control environmental factors (temperature as surrogate for productivity, disturbance, and propagule pressure) as well as to monitor whole‐community trait distributions of environmental adaptation, mass, and dispersal abilities. We simulated introductions of plant individuals to an oceanic island to assess which factors and species traits contribute to invasion success. We found that the most influential factors were higher propagule pressure and a particular set of traits. This invasion trait syndrome was characterized by a relative similarity in functional traits of invasive to native species, while invasive species had on average higher environmental adaptation, higher body mass, and increased dispersal distances, that is, had greater competitive and dispersive abilities. Our results highlight the importance in management practice of reducing the import of alien species, especially those that display this trait syndrome and come from similar habitats as those being managed.