Non-native Range Research Articles

Using RAD-seq to develop sex-linked markers in a haplodiplontic alga.

For many taxa, including isomorphic haplodiplontic macroalgae, determining sex and ploidy is challenging, thereby limiting the scope of some population demographic and genetic studies. Here, we used double-digest restriction site-associated DNA sequencing (ddRAD-seq) to identify sex-linked molecular markers in the widespread red alga Agarophyton vermiculophyllum. In the ddRAD-seq library, we included 10 female gametophytes, 10 male gametophytes, and 16 tetrasporophytes from one native and one non-native site (N=40 gametophytes and N=32 tetrasporophytes total). We identified seven putatively female-linked and 19 putatively male-linked sequences. Four female- and eight male-linked markers amplified in all three life cycle stages. Using one female- and one male-linked marker that were sex-specific, we developed a duplex PCR and tested the efficacy of this assay on a subset of thalli sampled at two sites in the non-native range. We confirmed ploidy based on the visual observation of reproductive structures and previous microsatellite genotyping at 10 polymorphic loci. For 32 vegetative thalli, we were able to assign sex and confirm ploidy in these previously genotyped thalli. These markers will be integral to ongoing studies of A. vermiculophyllum invasion. We discuss the utility of RAD-seq over other approaches previously used, such as RAPDs (random amplified polymorphic DNA), for future work designing sex-linked markers in other haplodiplontic macroalgae for which genomes are lacking.

Manipulation of cytosine methylation does not remove latitudinal clines in two invasive goldenrod species in Central Europe.

Invasive species frequently differentiate phenotypically in novel environments within a few generations, often even with limited genetic variation. For the invasive plants Solidagocanadensis and S.gigantea, we tested whether such differentiation might have occurred through heritable epigenetic changes in cytosine methylation. In a 2-year common-garden experiment, we grew plants from seeds collected along a latitudinal gradient in their non-native Central European range to test for trait differentiation and whether differentiation disappeared when seeds were treated with the demethylation agent zebularine. Microsatellite markers revealed no population structure along the latitudinal gradient in S.canadensis, but three genetic clusters in S.gigantea. Solidagocanadensis showed latitudinal clines in flowering phenology and growth. In S.gigantea, the number of clonal offspring decreased with latitude. Although zebularine had a significant effect on early growth, probably through effects on cytosine methylation, latitudinal clines remained (or even got stronger) in plants raised from seeds treated with zebularine. Thus, our experiment provides no evidence that epigenetic mechanisms by selective cytosine methylation contribute to the observed phenotypic differentiation in invasive goldenrods in Central Europe.

Reproduction in an Introduced Population of <i>Elaphe schrenckii</i> (Strauch, 1873) in Eelde, the Netherlands

In 1994 an unknown number of captive bred Russian rat snakes, Elaphe schrenckii (Strauch, 1873) were introduced near Groningen Airport Eelde (Drenthe Province), the Netherlands. Research in 2016/2017 confirmed that the species has become established and is expanding slowly, as recent sightings are known at distances up to 5.3 km from the initial release site. Although the continuous presence over two decades and sightings of different life stages of E. schrenckii specimens indicate successful reproduction, no reproductive data existed. To gain more insight, we conducted field surveys between 2014 and 2016 to collect data on oviposition sites and reproduction. Eggs of E. schrenckii were encountered in three compost heaps. Twenty-two clutches were found in these heaps in total, comprising a total of 332 eggs. Additionally, 42 loose eggs were found, totaling the number of retrieved eggs to 374. Minimum clutch sizes range from 10 – 21 eggs and average 15.1 ± 3.2 eggs (N = 22). Total individual egg hatching rate is 87.8% (N = 271). Clutch hatching rate varied between 46.2% and 100% with a mean value of 86.7 ± 18.8% (N = 16). Our findings indicate the importance of compost heaps for this species regarding reproduction as suitable sites for oviposition within this non-native range. Also, fecundity does not seem to be negatively affected by conditions in its invasive range; clutch size is on the high side. Because hatching rates can be high, its reproduction does not seem to be a limiting factor for further expansion within Eelde and surroundings.

The value of the species interaction-abiotic stress hypothesis (SIASH) for invasion biology: using native latitude to explain non-native latitudinal range sizes

Establishment and spread of introduced species are difficult to predict because they are subject to a myriad of factors. A hypothesis which integrates multiple ecological processes, such as the species interaction-abiotic stress hypothesis (SIASH), may improve our ability to predict introduction success (i.e. establishment and spread). SIASH postulates that, along an environmental gradient, species’ range limits are set by abiotic stress at the environmentally harsh end of that gradient and by species interactions at the environmentally benign end of the gradient. Given that species richness increases nearer the equator and that climate becomes harsher (colder) nearer the poles, latitude represents a useful gradient with which to test simple predictions of SIASH. In order to test whether non-native ranges conform to the predictions of SIASH, we evaluated non-native latitudinal range size data for 195 cross-continental, naturalized introductions of 140 animal and plant species. Median latitude of native range was positively related to range size in the introduced zone, such that species native to high latitudes occupied larger introduced ranges than species native to low latitudes. Furthermore, temperate native species occupied larger latitudinal ranges when introduced to tropical and subtropical zones than did tropical native species introduced to temperate zones. Our results suggest that where a species originates is as important as where it is introduced for predicting introduction success. Abiotic stress from cold more strongly constrains the range extents of introduced species than species interactions, which is particularly pronounced for species originating from tropical regions. Future work should determine how species interactions and abiotic stress jointly explain other components of non-native species’ success across different spatial gradients to better integrate SIASH into invasion biology.

Habitat utilization and feeding ecology of small round goby in a shallow brackish lagoon

We examined small-scale distribution and feeding ecology of a non-native fish species, round goby (Neogobius melanostomus (Pallas, 1814)), in different habitats of a coastal lagoon situated in the south-western Baltic Sea. First observations of round goby in this lagoon were reported in 2011, 3 years before the current study was conducted, and information on this species’ basic ecology in different habitats is limited. We found that mainly juvenile round gobies are non-randomly distributed between habitats and that abundances potentially correlate positively with vegetation density and thus structural complexity of the environment. Abundances were highest in shallower, more densely vegetated habitats indicating that these areas might act as a refuge for small round gobies by possibly offering decreased predation risk and better feeding resources. Round goby diet composition was distinct for several length classes suggesting an ontogenetic diet shift concerning crustacean prey taxa between small (≤ 50 mm total length, feeding mainly on zooplankton) and medium individuals (51–100 mm, feeding mainly on benthic crustaceans) and another diet shift of increasing molluscivory with increasing body size across all length classes. Differences in round goby diet between habitats within the smallest length class might potentially be related to prey availability in the environment, which would point to an opportunistic feeding strategy. Here, we offer new insights into the basic ecology of round goby in littoral habitats, providing a better understanding of the ecological role of this invasive species in its non-native range, which might help to assess potential consequences for native fauna and ecosystems.

Escape from natural enemies depends on the enemies, the invader, and competition.

The enemy release hypothesis (ERH) attributes the success of some exotic plant species to reduced top‐down effects of natural enemies in the non‐native range relative to the native range. Many studies have tested this idea, but very few have considered the simultaneous effects of multiple kinds of enemies on more than one invasive species in both the native and non‐native ranges. Here, we examined the effects of two important groups of natural enemies–insect herbivores and soil biota–on the performance of Tanacetum vulgare (native to Europe but invasive in the USA) and Solidago canadensis (native to the USA but invasive in Europe) in their native and non‐native ranges, and in the presence and absence of competition.In the field, we replicated full‐factorial experiments that crossed insecticide, T. vulgare–S. canadensis competition, and biogeographic range (Europe vs. USA) treatments. In greenhouses, we replicated full‐factorial experiments that crossed soil sterilization, plant–soil feedback, and biogeographic range treatments. We evaluated the effects of experimental treatments on T. vulgare and S. canadensis biomass.The effects of natural enemies were idiosyncratic. In the non‐native range and relative to populations in the native range, T. vulgare escaped the negative effects of insect herbivores but not soil biota, depending upon the presence of S. canadensis; and S. canadensis escaped the negative effects of soil biota but not insect herbivores, regardless of competition. Thus, biogeographic escape from natural enemies depended upon the enemies, the invader, and competition. Synthesis: By explicitly testing the ERH in terms of more than one kind of enemy, more than one invader, and more than one continent, this study enhances our nuanced perspective of how natural enemies can influence the performance of invasive species in their native and non‐native ranges.

Associations Between Winter Temperatures and the Timing and Duration of Annual Larval Recruitment of a Non-native Anomuran Crab

The green porcelain crab, Petrolisthes armatus, a subtropical/tropical species, was first recorded on intertidal oyster reefs in South Carolina in 1995. Since then, its range has expanded north in a series of surges and setbacks that appear to be associated with particularly cold winters that may cause mortality. Petrolisthes armatus reproduces year-round in its native range whereas its reproductive season in the non-native range is limited to warmer months. Variation in the timing and duration of larval recruitment is not known for the non-native range and these factors may affect further range expansion. To determine whether P. armatus larval recruitment is related to temperature variation, in particular, the severity of winter temperatures, archival biweekly (every 2 weeks) larval samples collected 1994–2018 near its northern range limit in the North Inlet Winyah Bay National Estuarine Research Reserve (NERR) were examined. The goal was to determine whether the timing and duration of larval ingress varied over time and was related to temperature variation. Petrolisthes armatus larvae were first observed in samples collected in 1995. There was considerable interannual variability in the timing of the start of recruitment (coefficient of variation 29%), which ranged from the last week of March at the earliest to the last week of July at the latest, for all years but one. Earlier annual recruitment was positively correlated with a longer recruitment duration. The timing of first larval recruitment was also related to the severity of the preceding winter, with later larval recruitment occurring in years with several consecutive days of cold temperatures. Cold winter temperatures appear to affect overwintering populations and their ability to reproduce in the early spring. A decreasing frequency of severe winters along the coastal South Atlantic Bight may promote further poleward range expansion of P. armatus.

Non-native populations and global invasion potential of the Indian bullfrog Hoplobatrachus tigerinus: a synthesis for risk-analysis

Invasive amphibians have considerable ecological and socio-economic impact. However, strong taxonomic biases in the existing literature necessitate synthesizing knowledge on emerging invaders. The Indian bullfrog, Hoplobatrachus tigerinus, a large dicroglossid frog (snout to vent length: up to 160 mm), is native to the Indian sub-continent. Despite the high likelihood of invasion success for H. tigerinus, based on the species’ natural history traits and human use, the status of its non-native populations and global invasion potential has not yet been assessed. In this paper, we provide a profile of H. tigerinus as an invasive species to aid in risk analyses and management of existing populations. We review the available knowledge on non-native populations of H. tigerinus and model its potential distribution in the non-native range and globally; finally, we evaluate its ecological and socio-economic impact using standard impact classification schemes. We confirm successful invasions on the Andaman archipelago and Madagascar. The ensemble species distribution model, with ‘good’ predictive ability and transferability, predicts tropical regions of the world to be climatically suitable for the species. Considering potential for propagule pressure, we predict the climatically suitable Mascarene Islands, Malaysia and Indonesia, and East Africa to likely be recipients of bridgehead invasions. We assign the species two impact scores: both socio-economic and environmental scores were ‘moderate’ with ‘medium’ confidence levels in our assessment. Finally, this synthesis outlines the invasion process of the genus Hoplobatrachus, which is an emerging group of amphibian invaders.

Drivers of richness and community composition of fungal endophytes of tree seeds.

Recent studies revealed a high diversity of fungal endophytes in traded tree seeds, including potential plant pathogens. The factors determining richness and composition of seed mycobiomes are poorly understood, but might be an important determinant for tree health. We assessed the relative impact of host identity, site, several site-specific environmental factors, and whether the host was sampled in its native or non-native distribution range, on the richness and composition of fungal seed endophytes of nine tree species across 15 sites in Europe and North America. Our results show that fungal richness was affected by host identity, but not by environmental variables or host distribution range. Fungal community composition was primarily driven by host identity, and to a lesser extent by environment. Around 25% of the 2147 amplicon sequence variants (ASVs) were generalists appearing on both continents and in both gymnosperms and angiosperms. Around 63% of the ASVs appeared in only gymnosperms or angiosperms, and 33% of the ASVs were associated with a single host species, while none were found in all tree species. Our results suggest that although seed trade might facilitate movements of fungi, their establishment and spread in the new environment might be limited by host availability.

Soil origin corresponds with variation in growth of an invasive Centaurea, but not of non-invasive congeners.

Why only a small proportion of exotic species become invasive is an unresolved question. Escape from the negative effects of soil biota in the native range can be important for the success of many invasives, but comparative effects of soil biota on less successful exotic species are poorly understood. Studies of other mechanisms suggest that such comparisons might be fruitful. Seeds of three closely related Centaurea species with overlapping distributions in both their native range of Spain and their nonnative range of California were grown to maturity in pots to obtain an F1 generation of full sibling seeds with reduced maternal effects. Full sibling F1 seeds from both ranges were subsequently grown in pots with inoculations of soil from either the native or nonnative ranges in a fully orthogonal factorial design. We then compared plant biomass among species, regions, and soil sources. Our results indicate that escape from soil pathogens may unleash the highly invasive Centaurea solstitialis, which was suppressed by native Spanish soils but not by soils from California. In contrast, the two non-invasive Centaurea species grew the same on all soils. These results add unprecedented phylogenetically controlled insight into why some species invade and others do not.

Why did the invasive walking catfish cross the road? Terrestrial chemoreception described for the first time in a fish.

Clarias batrachus (walking catfish) is an invasive species in Florida, renowned for its air-breathing and terrestrial locomotor capabilities. However, it is unknown how this species orients in terrestrial environments. Furthermore, while anecdotal life history information is widespread for this species in its nonnative range, little of this information exists in the literature. The goals of this study were to identify sensory modalities that C. batrachus use to orient on land, and to describe the natural history of this species in its nonnative range. Fish (n = 150) were collected from around Ruskin, FL, and housed in a greenhouse, where experiments took place. Individual catfish were placed in the center of a terrestrial arena and were exposed to nine treatments: two controls, L-alanine, quinine, allyl isothiocynate, sucrose, volatile hydrogen sulphide, pond water and aluminium foil. These fish exhibited significantly positive chemotaxis toward alanine and pond water, and negative chemotaxis away from volatile hydrogen sulphide, suggesting chemoreception - both through direct contact and through the air - is important to their terrestrial orientation. Additionally, 88 people from Florida wildlife-related Facebook groups who have personal observations of C. batrachus on land were interviewed for information regarding their terrestrial natural history. These data were combined with observations from 38 YouTube videos. C. batrachus appear to emerge most frequently during or just after heavy summer rains, particularly from stormwater drains in urban areas, where they may feed on terrestrial invertebrates. By better understanding the full life history of C. batrachus, we can improve management of this species.

Nutrient fluctuation has different effects on a tropical invader in communities from the native and non-native range

Invader success might depend on both nutrient availability and species richness of the resident community. Here, we combine these ideas in a single experiment, testing whether the Fluctuating resource and biotic resistance hypotheses might be contingent upon one another. The fluctuating resource hypothesis proposes that resource fluctuation might facilitate the successful invasion of exotic plants if invaders are better than natives at taking advantage of resource pulses. The biotic resistance hypothesis proposed that more species rich communities might be more resistant to invasion, due to greater competition for resources with greater native richness. Here, we use an experiment with the invader, Chromolaena odorata in 315 artificial communities with resident plants from native and non-native ranges. We found that resident origin, nutrient treatment and species richness of artificial community have significant effects on invasion success of C. odorata. The effect of nutrient fluctuation on invasion success was contingent on resident origin (native vs. non-native range), and this effect was weaker in more species rich communities. In addition, the invasion success of C. odorata was negatively related with biomass of resident plants, suggesting competition as a mechanism governing invader success. Our results suggest a novel twist on the fluctuating resource hypothesis: fluctuating resources may favor invaders more in species poor communities of non-native origin. This also suggests that competition for fluctuating resources may be one mechanism governing biotic resistance because the effects of richness were greater when resources were fluctuating. Our results suggest that the fluctuating resource hypothesis will apply only to resident communities with lower resource acquisition strategies, relative to the invader.

Methods to maximize environmental DNA (eDNA) for detection the presence of Alligator Gar (Atractosteus spatula)

Introduction of alligator gar (Atractosteus spatula) into a new range of its distribution has been reported in several freshwater ecosystems. The presence of alligator gar in Indonesia has been recorded in Jakarta during big flood in 2007. The concern about introducing this species is because of its predatory behavior and can impact the trophic system in freshwater ecosystem in its non-native range. Here, we demonstrated two methods, conventional and kit method, to maximize eDNA concentration in addition to detect the presence of alligator gar in freshwater ecosystem. We used mesocosm study to mimic the real condition of freshwater system in tropic region. We found that both methods can extract eDNA from water samples. The kit showed better yield of eDNA with average concentration 62.28 ± 22.27 ng/μL than conventional method with average concentration 19.35 ± 9.89 ng/μL. Another advantage of the kit method was better purity of eDNA, with average purity 1.92 ± 0.05 compared to conventional method with average purity 2.23 ± 0.42. The better concentration and purity of eDNA could be advantageous for further analyses such as PCR and DNA sequencing.

Sea lamprey (Petromyzon marinus) transit of a ramp equipped with studded substrate: Implications for fish passage and invasive species control

Anguilliform-swimming fishes (eels, lampreys) are undergoing large and global declines due partly to an inability to pass dams via traditional fishways. The installation of “eel ladders” (wetted, studded/bristle substrates that permit these fishes to climb over obstructions) offer a potential solution.We examined the behaviour of migrating sub-adult sea lamprey (Petromyzon marinus) as they approached and attempted to ascend a 45° studded ramp in a mesocosm placed in a river. We also examined motivation to use the ramp in the presence of a conspecific alarm cue that signals predation risk.Entrance (75%) and attraction efficiency (85%) were high, but reduced by the presence of alarm cue. In total, 98% of sea lamprey attracted to the base of the ramp ascended, and alarm cue had no effect. Time to ascend the ramp (post-release) was variable (1–521 min) and on average was 119 min (50% probability = 35 min). Few sea lamprey required multiple attempts to ascend (19.8%) and was more likely during longer transit times, with multiple ramp attachments, and with higher body mass. Propensity to attach to the ramp increased with number of attempts. The high efficacy of this design, compared to poor-mediocre efficiencies of similar designs in previous studies, may be related to water velocity and depth, geometry of substrate studs, substrate presentation (horizontal/vertical, and incline), and length of studded substrate.Studded ramps represent a substantial opportunity for managers attempting to selectively pass anguilliform fishes over dams, aiding conservation efforts. Applications to the management of sea lamprey include removal in their non-native Great Lakes range, and fish passage in their native range.

Oviposition response of the biocontrol agent Rhinocyllus conicus to resource distribution in its invasive host, Carduus nutans

Musk thistle, Carduus nutans, is a major noxious weed throughout its non-native range. The flower head weevil, Rhinocyllus conicus, deemed likely to be a strong candidate for biocontrol based on laboratory tests, has proven variable in its efficacy, suggesting a possible influence of ecological context. To improve our understanding of the dynamics of this system, we examined how R. conicus responds to the spatial distribution of musk thistle individuals. We manipulated the size and density of host plant patches to determine their effect on weevil oviposition. Neither patch size nor plant density significantly affected the number of eggs laid by R. conicus. However, plant characteristics such as flower head size, as well as plant height and number of flower heads per plant, significantly influenced oviposition. Although larger thistle flower heads provide more sites for oviposition, there is also more seed production in these heads. Thus, while R. conicus oviposition is highest in larger flower heads, the surplus of seed offsets the effectiveness of biological control. This observation may in part explain the variable levels of control by this biological control agent and ascertains circumstances when augmentative management procedures may be needed.

High prevalence of diseases in two invasive populations of red-eared sliders (Trachemys scripta elegans) in southwestern Spain

Abstract Non-native turtles are susceptible to pathogenic infections that may be transmitted to native species. We performed hematological, biochemical, histopathological, and microbiological analyses in two invasive populations of red-eared sliders (Trachemys scripta elegans), which were living alongside native turtle species in southwestern Spain. The red-eared sliders that were captured had a healthy external appearance. However, the histopathological analyses revealed that up to 88% of these turtles had internal pathologies. The most common were hepatic lipidosis and chronic nephritis, which frequently co-occurred with each other or with pulmonary or pancreatic lesions. A high proportion of turtles were susceptible to infections caused by common bacteria in these habitats. We detected Herpesvirus, Mycoplasma spp. and more than 18 Gram-negative bacteria. The high prevalence of disease recorded in the two populations suggests that red-eared sliders are poorly suited to the conditions in their non-native range.

Residency and reproductive patterns of the green porcelain crab, Petrolisthes armatus, on an intertidal oyster reef in its non-native range

The green porcelain crab Petrolisthes armatus is an abundant invader on intertidal oyster reefs along the southeastern coast of the United States. Its range expansion appears to be thermally limited and is predicted to shift poleward as water temperatures rise. Little is known about how P. armatus' seasonal residency patterns affect its reproductive potential near its northern range limit. To study these factors, P. armatus was collected every two weeks over a 20-month period (April 2017 to November 2018) on an intertidal oyster reef within its non-native range in Charleston, SC. Crab abundance, size, sex, and ovigery status were recorded. In addition, a laboratory experiment was conducted to determine the time elapsed between broods for large vs. small adult females. Petrolisthes armatus abundances varied seasonally and were highest in the summers of both years. Adults were collected in April after a mild winter (2017), indicating overwintering occurred, but after a harsh winter (2018), no crabs were collected on the reef the following spring, with adults first collected in July. Peak ovigery rates reached 95% of adult female crabs in some summer months. Juvenile recruits matured and contributed to the reproductive population 6–8 weeks after first being collected in the intertidal oyster habitat. In the laboratory experiment, the median time between broods was 6 days (range 2–22 days). Females were observed with new broods immediately post-molt and also several days following their molt, suggesting mating occurs for females in intermolt and post-molt states. Study results indicate that overwintering success affects the timing of the start of the reproductive season, its duration, and total annual brood production. The laboratory observations suggest rapid sequential brood production occurs for this species in the non-native range. Brood production rates and evidence that females mate in intermolt and post-molt states are new information for this species and are consistent with previous observations of high reproductive output in the non-native range. Further poleward range expansion seems likely, in part due to high reproductive output and rapid recovery following harsh winters.

What happens in Europe stays in Europe: apparent evolution by an invader does not help at home.

Some invasive plant species rapidly evolve greater size and/or competitive ability in their nonnative ranges. However, it is not well known whether these traits transfer back to the native range, or instead represent genotype-by-environment interactions where traits are context specific to communities in the new range where the evolution occurred. Insight into transferability vs. context specificity can be tested using experiments performed with individuals from populations from the native and nonnative ranges of exotic invasive species. Using a widespread invasive plant species in Europe, Solidago gigantea, we established reciprocal common garden experiments in the native range (Montana, North America; n=4) and the nonnative range (Hungary, Europe; n=4) to assess differences in size, vegetative shoot number, and herbivory between populations from the native and nonnative ranges. In a greenhouse experiment, we also tested whether the inherent competitive ability of genotypes from 15 native and 15 invasive populations differed when pitted against 11 common native North American competitors. In common gardens, plants from both ranges considered together produced five times more biomass, grew four times taller, and developed five times more rhizomes in the nonnative range garden compared to the native range garden. The interaction between plant origin and the common garden location was highly significant, with plants from Hungary performing better than plants from Montana when grown in Hungary, and plants from Montana performing better than plants from Hungary when grown in Montana. In the greenhouse, there were no differences in the competitive effects and responses of S.gigantea plants from the two ranges when grown with North American natives. Our results suggest that S.gigantea might have undergone rapid evolution for greater performance abroad, but if so, this response does not translate to greater performance at home.

Biogeographical comparison of terrestrial invertebrates and trophic feeding guilds in the native and invasive ranges of Carpobrotus edulis

Plant invasions impact on biodiversity by altering the composition of native communities by disrupting taxonomic and functional diversity. Non-native plants are often released from their natural enemies, which might result in a reduction of the attack of primary consumers. However, they can also be exposed to the attack of new herbivores that they might not be able to tolerate. Hence, invertebrate communities can be influenced by invasive non-native plants, which in turn modify interactions and change environmental conditions. In this study, we examined the compositional and trophic diversity of invertebrate species, comparing ecosystems with and without the plant species Carpobrotus edulis in coastal areas in its native (South Africa) and introduced (Iberian Peninsula) ranges. Results show that C. edulis has a clear impact on invertebrate communities in its non-native range, reducing their abundance in invaded areas, and particularly affecting certain trophic groups. Invasive C. edulis also alters the invertebrate diversity by not only reducing abundance but also by altering species composition. Overall, the physical dominance of C. edulis modifies the co-occurrence of invertebrate assemblages, reducing the number of trophic groups and leading to substantial effects on primary consumers. Results suggest that the lack of natural enemies might be an important driver of the expansion of C. edulis in its introduced range. Further work is needed to examine long-term changes caused by non-native plants on invertebrate assemblages and the subsequent modification of biological interactions.

Geographic Distribution of Camponotus sexguttatus (Hymenoptera, Formicidae), a Neotropical Carpenter Ant Spreading in Florida

The Neotropical carpenter ant Camponotus sexguttatus (Fabricius) has widespread records from the West Indies, Mexico, Central America, and South America. Across its broad native range, C. sexguttatus shows great variation, most notably in color, ranging from almost black to pale yellow. Non-native populations of C. sexguttatus were recorded for the first time in Florida in 1993, and in the Bahamas in 1995. Here, I examine the known native and non-native geographic distribution of C. sexguttatus.I compiled and mapped C. sexguttatus specimen records from >850 sites, including my own records from 583 sites. Camponotus sexguttatus has West Indian range from Hispaniola, Puerto Rico, and the Virgin Islands in the Greater Antilles through all major islands of the Lesser Antilles. On at least ten islands of the Lesser Antilles, two distinctly different C. sexguttatus color morphs coexist, the typical dark brown/black form plus a lighter form, suggesting that there are at least two separate lines of C. sexguttatus on these islands. Light forms have been previously described on four of these islands as three different subspecies.Camponotus sexguttatus has a continental range from Mexico, through Central America, to subtropical parts of Argentina, Uruguay, and Brazil. Records from the northern parts of this range, however, are very sparse, e.g., just a single record each from Mexico, Belize, Guatemala, and Honduras, and no records from El Salvador. In addition to the typical C. sexguttatus sexguttatus, seven currently valid subspecies have been described from South America. Genetic analyses should examine whether the different subspecific forms in the West Indies and South America should be considered distinct species.In its non-native range in peninsular Florida, C. sexguttatus is now known from 16 counties (Brevard, Broward, Collier, Glades, Hendry, Highlands, Indian River, Lee, Martin, Miami-Dade, Monroe, Okeechobee, Orange, Osceola, Palm Beach, and St Lucie), where it is often one of the most common and conspicuous arboreal ants. Variation among C. sexguttatus populations in Florida suggest that they descend from introductions from at least two different source populations. In Bahamas, there are just five records of C. sexguttatus, all from New Providence. It is likely that C. sexguttatus will continue to spread in Florida and the Bahamas, possibly impacting both native and non-native arboreal ants.