Traits Of Invasive Species Research Articles

Invasions cause biodiversity loss and community simplification in vertebrate food webs

Global change is increasing the occurrence of perturbation events on natural communities, with biological invasions posing a major threat to ecosystem integrity and functioning worldwide. Most studies addressing biological invasions have focused on individual species or taxonomic groups to understand both, the factors determining invasion success and their effects on native species. A more holistic approach that considers multispecies communities and species’ interactions can contribute to a better understanding of invasion effects on complex communities. Here we address biological invasions on species‐rich food webs. We performed in silico experiments on empirical vertebrate food webs by introducing virtual species characterised by different ecological roles and belonging to different trophic groups. We varied a number of invasive species traits, including their diet breadth, the number of predators attacking them, and the bioenergetic thresholds below which invader and native species become extinct. We found that simpler food webs were more vulnerable to invasions, and that relatively less connected mammals were the most successful invaders. Invasions altered food web structure by decreasing species richness and the number of links per species, with most extinctions affecting poorly connected birds. Our food web approach allows identifying the combinations of trophic factors that facilitate or prevent biological invasions, and it provides testable predictions on the effects of invasions on the structure and dynamics of multitrophic communities.

Strength in numbers: Large and permanent colonies have higher queen oviposition rates in the invasive Argentine ant (Linepithema humile, Mayr)

Polydomy associated with unicoloniality is a common trait of invasive species. In the invasive Argentine ant, colonies are seasonally polydomous. Most follow a seasonal fission–fussion pattern: they disperse in the spring and summer and aggregate in the fall and winter. However, a small proportion of colonies do not migrate; instead, they inhabit permanent nesting sites. These colonies are large and highly polydomous. The aim of this study was to (1) search for differences in the fecundity of queens between mother colonies (large and permanent) and satellite colonies (small and temporal), (2) determine if queens in mother and satellite colonies have different diets to clarify if colony size influences social organization and queen feeding, and (3) examine if colony location relative to the invasion front results in differences in the queen’s diet. Our results indicate that queens from mother nests are more fertile than queens from satellite nests and that colony location does not affect queen oviposition rate. Ovarian dissections suggest that differences in ovarian morphology are not responsible for the higher queen oviposition rate in mother vs. satellite nests, since there were no differences in the number and length of ovarioles in queens from the two types of colonies. In contrast, the higher δ15N values of queens from mother nests imply that greater carnivorous source intake accounts for the higher oviposition rates.

Litter Fall and Its Decomposition inSapium sebiferumRoxb.: An Invasive Tree Species in Western Himalaya

Recognizing that high litter fall and its rapid decomposition are key traits of invasive species, litter fall and its decay inSapium sebiferumRoxb. were studied in Palampur. For this, litter traps of dimension 50 × 50 × 50 cm3were placed in under-canopy and canopy gap of the species. Litter fall was monitored monthly and segregated into different components. For litter decay studies, litter bags of dimension 25 × 20 cm2with a mesh size 2 mm were used and the same were analyzed on a fortnightly basis. Litter fall in both under-canopy and canopy gap was highest in November (1.16 Mg ha−1 y−1in under-canopy and 0.38 Mg ha−1 y−1in canopy gap) and lowest during March. Litter production in under-canopy and canopy gap was 4.04 Mg ha−1 y−1and 1.87 Mg ha−1 y−1, respectively. These values are comparable to sal forest (1.7 t C ha−1 y−1), chir pine-mixed forest (2.1 t C ha−1 y−1), and mixed oak-conifer forest (2.8 t C ha−1 y−1) of the Western Himalaya. The decay rate, 0.46% day−1in under-canopy and 0.48% day−1in canopy gap, was also fast. Owing to this the species may be able to modify the habitats to its advantage, as has been reported elsewhere.

Impact of plant invasions on functional diversity in the vegetation of Central Europe

AbstractQuestionsHow is the loss of plant species richness, associated with invasions, related to changes in functional diversity? What is the relationship between the traits of invasive species and those of invaded communities?LocationDifferent Central European vegetation types within the Czech Republic.MethodsFunctional diversity was calculated for 260‐paired relevés, half non‐invaded and half invaded by one of 13 widespread invasive species in Central Europe. Four traits (height, SLA, seed mass and clonal index) were considered as a way to understand the functional space occupied by native and alien species in the data set (410 species altogether).ResultsSome of the functional diversity (FD) indices used (mean trait dissimilarity, mean nearest neighbour dissimilarity and SD of the mean nearest neighbour dissimilarity) revealed higher trait diversity for the invaded vegetation and negative relationship with species richness, while functional richness and evenness gave higher values for the uninvaded vegetation and positive relationship with species richness. Adding hypothetically the invader into the FD calculations for the uninvaded vegetation was found to increase most of the FD indices used, while excluding it from the FD calculations of the invaded vegetation decreased functional richness and also mean trait dissimilarity.ConclusionsResults suggest that invading aliens tend to be functionally different from native species and are therefore likely to occupy an empty niche in the invaded vegetation. Similarly, the resident species in the non‐invaded communities are not likely to occupy the whole potential niche space, which could remain available for the invasive species with different traits. This study suggests that the probability of a successful invasion is related to functional dissimilarities between the alien invader and native species of the resident communities.

Establishment of an Invasive Plant Species (Conium maculatum) in Contaminated Roadside Soil in Cook County, Illinois

Interactions between environmental variables in anthropogenically disturbed environments and physiological traits of invasive species may help explain reasons for invasive species' establishment in new areas. Here we analyze how soil contamination along roadsides may influence the establishment of Conium maculatum (poison hemlock) in Cook County, IL, USA. We combine analyses that: (1) characterize the soil and measure concentrations of heavy metals and polycyclic aromatic hydrocarbons (PAHs) where Conium is growing; (2) assess the genetic diversity and structure of individuals among nine known populations; and (3) test for tolerance to heavy metals and evidence for local soil growth advantage with greenhouse establishment experiments. We found elevated levels of metals and PAHs in the soil where Conium was growing. Specifically, arsenic (As), cadmium (Cd), and lead (Pb) were found at elevated levels relative to U.S. EPA ecological contamination thresholds. In a greenhouse study we found that Conium is more tolerant of soils containing heavy metals (As, Cd, Pb) than two native species. For the genetic analysis a total of 217 individuals (approximately 20–30 per population) were scored with 5 ISSR primers, yielding 114 variable loci. We found high levels of genetic diversity in all populations but little genetic structure or differentiation among populations. Although Conium shows a general tolerance to contamination, we found few significant associations between genetic diversity metrics and a suite of measured environmental and spatial parameters. Soil contamination is not driving the peculiar spatial distribution of Conium in Cook County, but these findings indicate that Conium is likely establishing in the Chicago region partially due to its ability to tolerate high levels of metal contamination.

A global assessment of invasive plant impacts on resident species, communities and ecosystems: the interaction of impact measures, invading species' traits and environment

With the growing body of literature assessing the impact of invasive alien plants on resident species and ecosystems, a comprehensive assessment of the relationship between invasive species traits and environmental settings of invasion on the characteristics of impacts is needed. Based on 287 publications with 1551 individual cases that addressed the impact of 167 invasive plant species belonging to 49 families, we present the first global overview of frequencies of significant and non-significant ecological impacts and their directions on 15 outcomes related to the responses of resident populations, species, communities and ecosystems. Species and community outcomes tend to decline following invasions, especially those for plants, but the abundance and richness of the soil biota, as well as concentrations of soil nutrients and water, more often increase than decrease following invasion. Data mining tools revealed that invasive plants exert consistent significant impacts on some outcomes (survival of resident biota, activity of resident animals, resident community productivity, mineral and nutrient content in plant tissues, and fire frequency and intensity), whereas for outcomes at the community level, such as species richness, diversity and soil resources, the significance of impacts is determined by interactions between species traits and the biome invaded. The latter outcomes are most likely to be impacted by annual grasses, and by wind pollinated trees invading mediterranean or tropical biomes. One of the clearest signals in this analysis is that invasive plants are far more likely to cause significant impacts on resident plant and animal richness on islands rather than mainland. This study shows that there is no universal measure of impact and the pattern observed depends on the ecological measure examined. Although impact is strongly context dependent, some species traits, especially life form, stature and pollination syndrome, may provide a means to predict impact, regardless of the particular habitat and geographical region invaded.

Genetic and maternal effects on tail spine and body length in the invasive spiny water flea (Bythotrephes longimanus).

Interest in the evolution of invasive species has grown in recent years, yet few studies have investigated sources of variation in invasive species traits experiencing natural selection. The spiny water flea, Bythotrephes longimanus, is an invasive zooplankton in the Great Lakes that exhibits seasonal changes in tail spine and body length consistent with natural selection. Evolution of Bythotrephes traits, however, depends on the presence and magnitude of quantitative genetic variation, which could change within or across years. Clonal analysis of wild-captured Bythotrephes indicated that variance components for distal spine length were variable among but not within years. Spine length was always heritable but was not always influenced by maternal effects. In contrast, variance components for body length varied both within and among years, but likewise body length was always heritable and not always influenced by maternal effects. Results indicate that important Bythotrephes traits have heritable variation comparable to native species and other invasive species that would enable an evolutionary response to natural selection. This evolutionary capacity could contribute to the widespread success and dramatic effects of Bythotrephes invasion in systems with diverse biotic and abiotic conditions.

Trait divergence and the ecosystem impacts of invading species

Trait divergence and the ecosystem impacts of invading species

Maladaptive traits in invasive species: in Australia, cane toads are more vulnerable to predatory ants than are native frogs

1. If a species is translocated outside its native range, some of its traits (evolved to match conditions in the ancestral range) likely will be maladaptive. Identifying ways in which the invader are poorly suited to its new range might provide novel opportunities for biocontrol. 2. The spread of cane toads (Bufo marinus, native to central and South America) through tropical Australia has created major ecological problems. Although many native predators cannot deal with the toxins of the invasive toads, 'meat ants' (Iridomyrmex reburrus) kill and consume many metamorph toads. Might this be a mismatch between the invader and its newly invaded range, whereby the morphology, locomotor ability and/or behaviour of cane toads renders them vulnerable to a predator that poses little danger to native anurans? 3. To explore this possibility, we measured habitat use and activity patterns in meat ants, metamorph cane toads and metamorphs of seven native frog species (Litoria bicolor, L. caerulea, L. dahlii, L. nasuta, L. rothii, Limnodynastes convexiusculus, Opisthodon ornatus) in standardized enclosures in the laboratory. 4. Unlike the frogs, (1) toads selected open microhabitats and were active diurnally, thus increasing encounter rates with meat ants; (2) toads failed to detect and evade approaching ants; (3) toads exhibited poor locomotor ability (short slow hops, reflecting their small size and short limbs); and (4) toads frequently relied on an ineffective defence mechanism (crypsis) when attacked. 5. In combination, these traits rendered cane toad metamorphs far more susceptible to predation by meat ants than were any of the native frogs tested. That vulnerability presumably reflects lack of coevolution between cane toads and Australian ants. 6. The inability of invasive toads to escape predatory native ants might be exploited to reduce cane toad numbers, by manipulating ant densities and/or locations during periods of toad metamorph emergence.

Specific leaf area relates to the differences in leaf construction cost, photosynthesis, nitrogen allocation, and use efficiencies between invasive and noninvasive alien congeners

Comparisons between invasive and native species may not characterize the traits of invasive species, as native species might be invasive elsewhere if they were introduced. In this study, invasive Oxalis corymbosa and Peperomia pellucida were compared with their respective noninvasive alien congeners. We hypothesized that the invasive species have higher specific leaf (SLA) than their respective noninvasive alien congeners, and analyzed the physiological and ecological consequences of the higher SLA. Higher SLA was indeed the most important trait for the two invaders, which was associated with their lower leaf construction cost, higher nitrogen (N) allocation to photosynthesis and photosynthetic N use efficiency (PNUE). The higher N allocation to photosynthesis of the invaders in turn increased their PNUE, N content in photosynthesis, biochemical capacity for photosynthesis, and therefore light-saturated photosynthetic rate. The above resource capture-, use- and growth-related traits may facilitate the two invaders' invasion, while further comparative studies on a wider range of invasive and noninvasive congeners are needed to understand the generality of this pattern and to fully assess the competitive advantages afforded by these traits.

High seedling relative growth rate and specific leaf area are traits of invasive species: phylogenetically independent contrasts of woody angiosperms

Understanding causal factors of exotic species invasions is important not only for prevention and prioritizing control efforts, but also for providing valuable insights into the underlying biology of contrasting life-history strategies. In seedling growth analyses, invasive woody species were compared with less-invasive woody species commonly cultivated in California using phylogenetically corrected procedures (12 phylogenetically independent contrasts). Invasive species were hypothesized to have higher seedling relative growth rates (RGRs) and specific leaf areas (SLAs) than did related less-invasive species. In phylogenetically independent contrasts conducted among taxa within families, high seedling RGRs and SLAs have significant positive associations with woody plant invasiveness. For contrasts containing species invasive in mediterranean regions, invasive species had significantly larger root biomass allocation than did less-invasive species. Optimization of fast seedling growth (high RGR) associated with opportunistic resource acquisition (high SLA) and increased root allocation to survive summer drought may be critical for the success of plant invaders in regions with mediterranean climates.

RELATEDNESS AND ENVIRONMENT AFFECT TRAITS ASSOCIATED WITH INVASIVE AND NONINVASIVE INTRODUCED COMMELINACEAE

Understanding the traits of invasive species may improve the ability to predict, prevent, and manage invasions. I compared morphological and performance traits of five congeneric pairs of invasive and noninvasive Commelinaceae across a factorial experiment using a range of water and nutrient availabilities. Invasive species had greater fecundity and vegetative reproduction than their noninvasive relatives. The invasive species also had higher relative growth rates, greater specific leaf area, and more plastic root-to-shoot ratios than noninvasive species. However, whether a trait was associated with invasiveness often depended on both environment and relatedness. Invasives had greater sexual and vegetative reproduction, higher specific leaf area, and greater relative growth rates than noninvasive congeners, but only in some environments. Differences between invasive and noninvasive taxa were greatest at high nutrient availabilities. These results suggest that studies of invasive species' traits must incorporate information on conditions under which the trait was measured. In addition, incorporating information on relatedness improved our ability to detect associations between species traits, such as specific leaf area and relative growth rate, and invasiveness, suggesting that such information may be required for a complete understanding of what makes a species invasive.

Can Developmental and Behavioral Characteristics of the Multicolored Asian Lady Beetle Harmonia Axyridis Explain its Invasive Success?

Major impacts of biological invasions are widely recognized and underscore the need to understand the relation between life-history traits of invasive species and the invasion process. Growth of juveniles and adult survival of invasive species are key factors in invasion process. Life-history traits that increase juvenile fitness including increased rates of development and behavioral characteristics that facilitate competitive success such as increased predator efficiency and foraging ability may explain invasiveness of a species. Invasion of Harmonia axyridis Pallas (Coleoptera: Coccinellidae) in North America provides an opportunity to investigate life-history traits of juveniles of an invasive species. Here, we evaluate both developmental and behavioral traits that may explain the success of H. axyridis by comparing it to an ecologically similar indigenous species Coleomegilla maculata lengi Timberlake (Coleoptera: Coccinellidae). Three points may contribute to the invasiveness of H. axyridis. First, development of H. axyridis was faster during the 2nd larval instar than C. maculata, a characteristic that may reduce vulnerability at young instars. Second, H. axyridis reached the 4th instar more rapidly than C. maculata. The 4th instar of H. axyridis was also characterized by higher predation efficiency with increased voracity, lethal contact and search efficiency of pea aphids Acyrthosiphon pisum. Finally, surprisingly, a 5th larval instar occured in 33% of the individuals of H. axyridis and was characterized by the same developmental time, but with increased voracity and weight gain compared to 4th larval instars, suggesting an increased fitness of these individuals. These developmental characteristics coupled with increased predation efficiency and behavioral characteristics enhanced the juvenile growth and predatory abilities of this species and may contribute to the invasive ability of H. axyridis.

Profiling invasive fish species: the importance of phylogeny and human use

ABSTRACTUnderstanding the ecological differences between native and invasive species is of considerable scientific and practical interest. We examined such differences between native and invasive inland fish species from the Iberian Peninsula in order to analyse the importance of phylogenetic correction and variability (in addition to central tendency). We collected 26 quantitative and qualitative variables on the ecology, life‐history traits and human use of the 69 inland fish species of the Iberian Peninsula, including native, invasive and migratory species. The taxonomic distribution of invasive fish species deviated significantly from world freshwater richness and in contrast to native species, invasive fish belongs to only five taxonomic orders but to a wide spectrum of families not native to the Iberian Peninsula. Because the life‐history traits were highly dependent on taxonomy, the results, with or without applying phylogenetic methods, differed and after accounting for phylogeny, invasive species displayed higher and wider latitude in general and a different reproductive season mainly among salmonids and cyprinids. Human use was also significantly different between native and invasive fish species and produced more variability in life‐history traits of invasive species and uneven taxonomic distribution because of the high diversity of species introduced. We show that accounting for taxonomy and studying variability in addition to central tendency is important in the comparison of life‐history traits between native and invasive species.