Isolation and characterization of polymorphic microsatellite markers in the wall lizard Podarcis erhardii (Squamata: Lacertidae)

Five polymorphic microsatellite loci (containing di‐ and penta‐nucleotide repeats) were developed for the Erhard's wall lizard, Podarcis erhardii, an endemic species of southern Balkan Peninsula. The number of alleles ranged from five to 17. Observed and expected heterozygosities ranged from 0.28 to 0.92 and 0.57 to 0.91, respectively. These markers will provide a valuable tool for population genetics analyses and can contribute to the evaluation of conservation programs.     

Patterns of cranial ontogeny in lacertid lizards: morphological and allometric disparity

We explored the ontogenetic dynamics of the morphological and allometric disparity in the cranium shapes of twelve lacertid lizard species. The analysed species (Darevskia praticola, Dinarolacerta mosorensis, Iberolacerta horvathi, Lacerta agilis, L. trilineata, L. viridis, Podarcis erhardii, P. melisellensis, P. muralis, P. sicula, P. taurica and Zootoca vivipara) can be classified into different ecomorphs: terrestrial lizards that inhabit vegetated habitats (habitats with lush or sparse vegetation), saxicolous and shrub‐climbing lizards. We observed that there was an overall increase in the morphological disparity (MD) during the ontogeny of the lacertid lizards. The ventral cranium, which is involved in the mechanics of jaw movement and feeding, showed higher levels of MD, an ontogenetic shift in the morphospace planes and more variable allometric patterns than more conserved dorsal crania. With respect to ecology, the allometric trajectories of the shrub‐climbing species tended to cluster together, whereas the allometric trajectories of the saxicolous species were highly dispersed. Our results indicate that the ontogenetic patterns of morphological and allometric disparity in the lacertid lizards are modified by ecology and functional constraints and that the identical mechanisms that lead to intraspecific morphological variation also produce morphological divergence at higher taxonomic levels.     

Aegean wall lizards switch foraging modes,diet, and morphology in a human‐built environment

Foraging mode is a functional trait with cascading impacts on ecological communities. The foraging syndrome hypothesis posits a suite of concurrent traits that vary with foraging mode; however, comparative studies testing this hypothesis are typically interspecific. While foraging modes are often considered typological for a species when predicting foraging‐related traits or mode‐specific cascading impacts, intraspecific mode switching has been documented in some lizards. Mode‐switching lizards provide an opportunity to test foraging syndromes and explore how intraspecific variability in foraging mode might affect local ecological communities.Because lizard natural history is intimately tied to habitat use and structure, I tested for mode switching between populations of the Aegean wall lizard, Podarcis erhardii, inhabiting undisturbed habitat and human‐built rock walls on the Greek island of Naxos. I observed foraging behavior among 10 populations and tested lizard morphological and performance predictions at each site. Furthermore, I investigated the diet of lizards at each site relative to the available invertebrate community.I found that lizards living on rock walls were significantly more sedentary—sit and wait—than lizards at nonwall sites. I also found that head width increased in females and the ratio of hindlimbs to forelimbs in both sexes increased as predicted. Diet also changed, with nonwall lizards consuming a higher proportion of sedentary prey. Lizard bite force also varied significantly between sites; however, the pattern observed was opposite to that predicted, suggesting that bite force in these lizards may more closely relate to intraspecific competition than to diet.This study demonstrates microgeographic variability in lizard foraging mode as a result of human land use. In addition, these results demonstrate that foraging mode syndromes can shift intraspecifically with potential cascading effects on local ecological communities.     

Behavioral syndrome in a native and an invasive hymenoptera species

Recent studies have focused on the role of behavior in biological invasions. Individuals may differ consistently in time for several behavioral traits (personality) which covary (behavioral syndrome) resulting in different behavioral types, some of them favoring invasion. Social hymenopterans have a strong potential to be invaders and their success depends primarily on the foundresses’ ability to found viable colonies. They are expected to be active, explorative and bold for optimally establishing their nest. In Europe, 2 hornet species coexist: the native Vespa crabro and the invasive Vespa velutina. These 2 species may compete for nesting sites and we suggest that the initial success of V. velutina has been favored by its behavior in outperforming V. crabro for the traits involved in nest initiation. Here, we (i) defined the personality of V. crabro and V. velutina, (ii) tested for the existence of behavioral syndrome in these species, and (iii) compared their performances using an open‐field test. Our results show that V. crabro foundresses behave consistently but not V. velutina; this lack of consistency being mainly due to reduced variance among individuals. This result questions the possibility of detecting consistent behavioral differences in species having recently undergone a strong bottleneck. Both species exhibit the same correlations between activity, boldness and exploration and V. velutina clearly outperforms V. crabro for all traits. Our results suggest that activity, boldness, and exploration are implicated in both hornet nest initiation and invasion process which contributed to explain why social hymenopterans are so successful at colonization.     

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.     

Conspicuous male coloration impairs survival against avian predators in Aegean wall lizards,Podarcis erhardii

Animal coloration is strikingly diverse in nature. Within‐species color variation can arise through local adaptation for camouflage, sexual dimorphism and conspicuous sexual signals, which often have conflicting effects on survival. Here, we tested whether color variation between two island populations of Aegean wall lizards (Podarcis erhardii) is due to sexual dimorphism and differential survival of individuals varying in appearance. On both islands, we measured attack rates by wild avian predators on clay models matching the coloration of real male and female P. erhardii from each island population, modeled to avian predator vision. Avian predator attack rates differed among model treatments, although only on one island. Male‐colored models, which were more conspicuous against their experimental backgrounds to avian predators, were accordingly detected and attacked more frequently by birds than less conspicuous female‐colored models. This suggests that female coloration has evolved primarily under selection for camouflage, whereas sexually competing males exhibit costly conspicuous coloration. Unexpectedly, there was no difference in avian attack frequency between local and non‐local model types. This may have arisen if the models did not resemble lizard coloration with sufficient precision, or if real lizards behaviorally choose backgrounds that improve camouflage. Overall, these results show that sexually dimorphic coloration can affect the risk of predator attacks, indicating that color variation within a species can be caused by interactions between natural and sexual selection. However, more work is needed to determine how these findings depend on the island environment that each population inhabits.     

Testing the hypothesis of greater eurythermality in invasive than in native ladybird species: from physiological performance to life‐history strategies

1. Global warming and biological invasions are important threats to biodiversity. Nonetheless, there is little information on how these factors influence performance or life‐history traits of invasive and native species. 2. The effects of temperature on physiological and fitness traits of two invasive alien species (Harmonia axyridis and Hippodamia variegata) and one native species (Eriopis chilensis) of coccinellid were evaluated, testing a model of eurythermality. Eggs of all species were exposed to four temperature treatments (20, 24, 30 and 33 °C). In adult F₂ we measured fecundity, locomotor performance, development time (total and per life stage), survival, and preferred body temperature in a thermal gradient. 3. It was found that H. axyridis had comparatively better performance at low temperatures (i.e. 20 °C), while the performance of H. variegata and E. chilensis did not change with temperature or was better at higher temperatures (30 °C). The standardised Levins index showed that all species are eurythermic. E. chilensis had a high niche overlap with the invasive alien ladybird species, rejecting the hypothesis of greater eurythermality of invasive species than native species. 4. Although there were differences in the temperature preferences and in the response of some physiological and life‐history traits of ladybirds to temperature, both the native and invasive alien species are eurythermic, contrary to the prediction. The better performance of H. axyridis at lower temperatures may result in displacement of its current distribution, and thus not all invasive species will respond favourably to global warming.     

Comparisons of isotopic niche widths of some invasive and indigenous fauna in a South African river

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Wider spectrum of fruit traits in invasive than native floras may increase the vulnerability of oceanic islands to plant invasions

Plant–animal mutualisms such as seed dispersal can play an important role in enabling some species to become invasive. For example, an introduced species could become invasive because birds prefer its fruits to those of native plants. To investigate this possibility, we compared various measures of fruit quality of 22 of the most common native and invasive woody species on the oceanic island Mahé (Seychelles, Indian Ocean). Individual measures of food quality tended to vary much more amongst invasive species than amongst native species; thus, whereas for particular traits the fruits of some invasive species had higher values than any native species, others had relatively low values. However, invasive species consistently produced fruits with a lower water content, resulting in a higher relative yield (i.e. dry pulp weight to total wet fruit weight ratio), and a higher energy content. The fruits of the most abundant invasive tree Cinnamomum verum (Lauraceae) were of particularly high nutritional quality, with individual berries containing 3.5 times more protein and 55 times more lipid than the median values of the native species. We suggest that our results may reflect a general tendency for island plants to produce fruits of low energy content, perhaps reflecting reduced competition for dispersal agents on isolated islands. In addition, we argue that inconsistent results on the relevance of fruit quality for plant invasions reported in the literature may be resolved by comparing the widths of trait spectra for native and alien floras rather than average values. Gaps in the native fruit trait spectrum may provide opportunities for particular invasive species, and weaken the resistance of regional floras to invasions. Such empty niche opportunities may occur for several reasons, including generally broader trait spectra in globally assembled alien than regional native floras (especially on oceanic islands), or the loss of native species due to human activities. More generally, a focus on trait variation rather than average trends may help to advance generalisation in invasion biology.     

The bioinvasion of Guam: inferring geographic origin,pace, pattern and process of an invasive lizard (<Emphasis Type="Italic">Carlia</Emphasis>) in the Pacific using multi-locus genomic data

Invasive species often have dramatic negative effects that lead to the deterioration and loss of biodiversity frequently coupled with the burden of expensive biocontrol programs and subversion of socioeconomic stability. The fauna and flora of oceanic islands are particularly susceptible to invasive species and the increase of global movements of humans and their products since WW II has caused numerous anthropogenic translocations and increased the ills of human-mediated invasions. We use a multi-locus genomic dataset to identify geographic origin, pace, pattern and historical process of an invasive scincid lizard (Carlia) that has been inadvertently introduced to Guam, the Northern Marianas, and Palau. This lizard is of major importance as its introduction is thought to have assisted in the establishment of the invasive brown treesnake (Boiga irregularis) on Guam by providing a food resource. Our findings demonstrate multiple waves of introductions that appear to be concordant with movements of Allied and Imperial Japanese forces in the Pacific during World War II.     

Ecologically heterogeneous populations of the invasive ant Wasmannia auropunctata within its native and introduced ranges

Abstract 1. The biology of most invasive species in their native geographical areas remains largely unknown. Such studies are, however, crucial in shedding light on the ecological and evolutionary processes underlying biological invasions. 2. The present study focuses on the little fire ant Wasmannia auropunctata, a species native to Central and South America that has been widely introduced and which has become invasive throughout the tropics. We characterise and compare several ecological traits of native populations in French Guiana with those in one of its introduced ranges, New Caledonia. 3. We found ecologically heterogeneous populations of W. auropunctata coexisting in the species’ native geographical area. First, we found populations restricted to naturally perturbed areas (particularly floodplains) within the primary forest, and absent from the surrounding forest areas. These populations were characterised by low nest and worker densities. Second, we found dominant populations in recent anthropogenic areas (e.g. secondary forest or forest edge along road) characterised by high nest and worker densities, and associated with low ant species richness. The local dominance of W. auropunctata in such areas can be due to the displacement of other species (cause) or the filling‐up of empty habitats unsuitable to other ants (effect). With respect to their demographic features and ant species richness, the populations of native anthropogenic habitats were to a large extent similar to the invasive populations introduced into remote areas. 4. The results point to the need for greater research efforts to better understand the ecological and demographic features of invasive species within their native ranges.     

Species interactions contribute to the success of a global plant invader

Biological invasions are ubiquitous ecological phenomena that often impact native ecosystems. Some introduced species have evolved traits that enhance their ability to compete and dominate in recipient communities. However, it is still unknown if introduced species can evolve traits that may enhance their species interactions to fuel invasion success. We tested whether Centaurea solstitialis (yellow starthistle) from introduced populations have greater performance than native counterparts, and whether they generate more beneficial plant-soil interactions. We used common garden and plant-soil feedback experiments with soils and seeds from native Eurasian and introduced Californian populations. We found that performance of Centaurea did not differ among source genotypes, implying that the success of this invasive species is not due to evolutionary changes. However, Centaurea grew significantly larger in soils from introduced regions than from native regions, indicating a reduction in natural enemy pressure from native populations. We conclude that species interactions, not evolution, may contribute to Centaurea’s invasion success in introduced populations.     

Genetic variation in photosynthetic characteristics among invasive and native populations of reed canarygrass (Phalaris arundinacea)

With the extensive spread of invasive species throughout North America and Europe there is an urgent need to better understand the morphological and physiological characteristics of successful invasive plants and the evolutionary mechanisms that allow introduced species to become invasive. Most ecological studies have focused on morphological differences and changes in community dynamics, and physiological studies have typically explored the differences between native and invasive species. In this study, 15 different genotypes of Phalaris arundinacea from both its native (European) and invasive (North American) range were grown in a common garden experiment to monitor the physiological differences between native and invasive genotypes. Here we present data that suggests high variability exists in the physiological traits among genotypes of P. arundinacea, yet genotypes from the native range are not necessarily physiologically inferior to the hybridized invasive genotypes. Previous work has shown that multiple introductions of P. arundinacea from various European locations to the United States resulted in numerous hybridization events, yielding more genetic variability and phenotypic plasticity in the invasive range. Of the genotypes studied, both morphological and physiological traits of genotypes with French origin were significantly different from the plants from the Czech Republic, North Carolina, and Vermont. The lack of clear differences between native and invasive genotypes indicates that physiological traits may be highly conserved in P. arundinacea and enhanced photosynthetic rates are not indicative of successful invasive genotypes. Instead, morphological traits and defensive secondary compound metabolism may play a more important role in the success of P. arundinacea within its invasive range, and patterns of genetic variation in physiological traits between invasive and native range may be more important than the mean traits of each region when explaining reed canarygrass’ invasive potential in North America.     

Native and invasive hosts play different roles in host–parasite networks

Parasites are often key players in biological invasions since they can mediate the impact of host invasions or can themselves become invasive species. However, the nature and extent of parasite-mediated invasions are often difficult to delineate. Here, we used individual-based, weighted bipartite networks to study the roles (degrees of interactions of individuals in a modular network according to their within- and among-module connections) played by native and invasive host individuals to their parasite communities. We studied two phylogenetically and ecologically close fish species, Mugil cephalus s.l. and Planiliza haematocheilus (Teleostei: Mugilidae). Planiliza haematocheilus is native to the Sea of Japan and invasive in the Sea of Azov whereas, M. cephalus s.l. is native to both seas. Based on the common evolutionary history that drives native host–parasite networks, we hypothesised that 1) native networks have higher modularity than invaded ones; and 2) invasive hosts in the invaded area play a peripheral role to structure parasite communities. We analysed the whole parasite community and subsets based on transmission strategy and host specificity of the parasite species to establish whether modularity and host roles are related to these features in the native and invaded areas. All networks were found to be modular. However, modularity tended to be higher in networks of the native area rather than those of the invaded area. Host individuals of both fish species played similar roles in the native area, whereas invasive hosts played a peripheral role in the networks of the invaded area. We propose that long-term monitoring of the roles of invasive hosts in parasite communities can be a useful proxy for estimating the maturity of the establishment of the invasive hosts in an ecosystem.     

Feeding preferences of Melanoplus femurrubrum grasshoppers on native and exotic grasses: behavioral and molecular approaches

Generalist insect herbivores, such as grasshoppers, may either avoid feeding on exotic plants, potentially enabling these plants to become invasive in the introduced range, or insects may incorporate exotic plants into their diet, contributing to the biotic resistance of native communities and potentially preventing plant invasions. Accurate determination of insect diet preferences with regard to native and exotic plants can be challenging, but this information is critical for understanding the interaction between native herbivores and exotic plants, and ultimately the mechanisms underlying plant invasions. To address this, we combined behavioral and molecular approaches to accurately compare food consumption of the polyphagous red‐legged grasshopper, Melanoplus femurrubrum (De Geer) (Orthoptera: Acrididae), on native [Andropogon gerardii Vitman and Bouteloua curtipendula (Michx.) Torr.] and exotic, potentially invasive grasses [Miscanthus sinensis Andersson and Bothriochloa ischaemum (L.) Keng] (all Poaceae). We found that M. femurrubrum grasshoppers demonstrated strong feeding preferences toward exotic grasses in experiments with intact plants under both field and greenhouse conditions, but they showed no preference in experiments with clipped leaves. Additionally, we sampled the gut contents of M. femurrubrum collected in the field and identified the ingested plant species based on DNA sequences for the non‐coding region of the chloroplast trnL (UAA) gene. We found that exotic plants were prevalent in the gut contents of grasshoppers collected at study sites in Ohio and Maryland, USA. These results suggest that the generalist herbivore M. femurrubrum does not avoid feeding on exotic grasses with which they do not share coevolutionary history. In addition, by demonstrating greater food consumption of exotic plants, these grasshoppers potentially provide biotic resistance should these grasses escape cultivation and become invasive in the introduced range.     

Competitive interactions between co-occurring invaders: identifying asymmetries between two invasive crayfish species

Ecosystems today increasingly suffer invasions by multiple invasive species. Complex interactions between invasive species can have different fitness implications for each invader, which can in turn determine the future progression of their invasions and result in differential impacts on native species and ecosystems. To this end, through pair-wise and group scale experiments, we examined possible interaction outcomes, competition effects and their potential fitness implications for two widespread invasive species of crayfish that increasingly co-occur in freshwater ecosystems of Europe (Pacifastacus leniusulus and Orconectes limosus). In all trials, P. leniusculus demonstrated the potential to outcompete O. limosus in both staged encounters and direct resource competition, being more likely to win heterospecific agonistic encounters and to acquire shelters at a higher rate. Observed dyadic dominance was translated to a broader social context of group-scale experiments, in which dominance of P. leniusculus was further strengthened by size differential between species. O. limosus was not able to compensate for competitive pressure by the dominant P. leniusculus and suffered wet weight loss and more frequent injuries in the presence of P. leniusculus. While both species are detrimental to native ecosystems, the ability of P. leniusculus to withstand competition pressure from another successful invasive species underscores its potential to establish dominant populations. Our results highlight the importance of understanding interspecies competition in prioritizing potential management activities or control efforts in contact zones.     

Do invasive plants structure microbial communities to accelerate decomposition in intermountain grasslands?

Invasive plants are often associated with greater productivity and soil nutrient availabilities, but whether invasive plants with dissimilar traits change decomposer communities and decomposition rates in consistent ways is little known. We compared decomposition rates and the fungal and bacterial communities associated with the litter of three problematic invaders in intermountain grasslands; cheatgrass (Bromus tectorum), spotted knapweed (Centaurea stoebe) and leafy spurge (Euphorbia esula), as well as the native bluebunch wheatgrass (Pseudoroegneria spicata). Shoot and root litter from each plant was placed in cheatgrass, spotted knapweed, and leafy spurge invasions as well as remnant native communities in a fully reciprocal design for 6 months to see whether decomposer communities were species‐specific, and whether litter decomposed fastest when placed in a community composed of its own species (referred to hereafter as home‐field advantage–HFA). Overall, litter from the two invasive forbs, spotted knapweed and leafy spurge, decomposed faster than the native and invasive grasses, regardless of the plant community of incubation. Thus, we found no evidence of HFA. T‐RFLP profiles indicated that both fungal and bacterial communities differed between roots and shoots and among plant species, and that fungal communities also differed among plant community types. Synthesis. These results show that litter from three common invaders to intermountain grasslands decomposes at different rates and cultures microbial communities that are species‐specific, widespread, and persistent through the dramatic shifts in plant communities associated with invasions.     

Functional traits,growth patterns,and litter dynamics of invasive alien and co-occurring native shrub species of chir pine forest in the central Himalaya,India

Across the continents, plant invasion is identified as one of the main threats to ecosystem functioning and stability. The main objective of this research was to evaluate the differences in the functional traits between invasive alien (Ageratina adenophora (Spreng.) and Lantana camara L.) and native (Berberis asiatica Roxb. Ex DC., Pyracantha crenulata (D. Don.) M. Roemer and Rubus ellipticus Sm.) shrub species of chir pine (Pinus roxburghii Sarg.) forest in the central Himalaya. Three 0.5 hectare chir pine forest stands were selected and individuals of similar diameter were tagged for comparative studies of leaf traits, growth pattern, and biomass accumulation in structural organs of each invasive alien and native species. Our one-way ANOVA and Tukey’s post hoc test results showed that both the invasive alien species have significantly (p?<?0.05) higher SLA, LWC, total chlorophyll content, foliar nutrient (N and P), RGR, LMR, SMR, nutrient uptake, and nutrient use efficiencies than native species. Leaf litter decomposition rate and nutrient release were also significantly (p?<?0.05) higher in both the invasive alien species. Native species, R. ellipticus, shared some of the traits, such as leaf area, chlorophyll content, RGR, LAR, LMR, and nutrient uptake efficiency with invasive alien species. The majority of traits differed among invasive alien and native species, implying that the success of invasive alien species is best described by being functionally distinct from native species. These findings indicate that invasive alien species had advanced functional traits which may be playing an important role in a rapid spread in the central Himalaya.

     

Cryptic niche conservatism among evolutionary lineages of an invasive lizard

Aim There is increasing evidence that the quality and breadth of ecological niches vary among individuals, populations, evolutionary lineages and therefore also across the range of a species. Sufficient knowledge about niche divergence among clades might thus be crucial for predicting the invasion potential of species. We tested for the first time whether evolutionary lineages of an invasive species vary in their climate niches and invasive potential. Furthermore, we tested whether lineage‐specific models show a better performance than combined models. Location Europe. Methods We used species distribution models (SDMs) based on climatic information at native and invasive ranges to test for intra‐specific niche divergence among mitochondrial DNA (mtDNA) clades of the invasive wall lizard Podarcis muralis. Using DNA barcoding, we assigned 77 invasive populations in Central Europe to eight geographically distinct evolutionary lineages. Niche similarity among lineages was assessed and the predictive power of a combination of clade‐specific SDMs was compared with a combined SDM using the pooled records of all lineages. Results We recorded eight different invasive mtDNA clades in Central Europe. The analysed clades had rather similar realized niches in their native and invasive ranges, whereas inter‐clade niche differentiation was comparatively strong. However, we found only a weak correlation between geographic origin (i.e. mtDNA clade) and invasive occurrences. Clades with narrow realized niches still became successful invaders far outside their native range, most probably due to broader fundamental niches. The combined model using data for all invasive lineages achieved a much better prediction of the invasive potential. Conclusions Our results indicate that the observed niche differentiation among evolutionary lineages is mainly driven by niche realization and not by differences in the fundamental niches. Such cryptic niche conservatism might hamper the success of clade‐specific niche modelling. Cryptic niche conservatism may in general explain the invasion success of species in areas with apparently unsuitable climate.