Non-native Habitats Research Articles

Adaptation in the Anthropocene: How behavioural choice and colour change enables chameleon prawns to camouflage on non-native seaweeds.

Animals combine colour change and behavioural choices to enhance concealment and adapt to changes in habitat in time and space. However, non-native and invasive habitat-forming plants and seaweeds can change the landscape, challenging animals to remain camouflaged, especially when the colour of the new habitat differs from the native backgrounds.The chameleon prawn (Hippolyte varians) exhibits remarkable colour variation and effective camouflage against different native seaweeds in shallow tidepools. Individuals optimize crypsis by choosing colour-matching seaweeds and changing colour over time. In some locations, the prawn's native habitats are now replaced by non-native seaweeds of different coloration and structure, making it important to understand whether substrate choice and colour change facilitates the occupation of these seaweeds and enables prawns to camouflage against new backgrounds.Using image analysis and visual modelling of a fish predator, we assessed the colour variation and camouflage of chameleon prawns occupying the non-native seaweeds brown wireweed (Sargassum muticum) and pink harpoon weed (Asparagopsis armata) in southwest UK. We performed laboratory trials to examine whether prawns maintain their preference for colour-matching native substrates when given a choice between them and non-native seaweeds, and if they can change their coloration to improve camouflage against non-native substrates.Prawns exhibit phenotypic diversity and camouflage that varied with the non-native seaweed species, with low colour variation and effective camouflage on pink harpoon weed, but high colour diversity and reduced concealment against brown wireweed. Prawns choose non-native seaweeds when the alternative native substrate provides mismatching coloration, but they did not exhibit any preference between colour-matching native and non-native seaweeds. Once in non-native habitats, prawns change their appearance over a few days to match the background, sometimes faster than when changing on native seaweeds of contrasting coloration.Although human activities considerably modify the coloration of marine landscapes by increasing the establishment of non-native seaweeds, the impacts of those changes appear less severe for colour-changing species, such as chameleon prawns, and will depend on the similarity between the colour of the new substrates and the original native backgrounds, and how animals use behaviour and physiology to match new habitats.

Resilience of Pinus pinea L. Trees to Drought in Central Chile Based on Tree Radial Growth Methods

The increasing occurrence of dry and hot summers generates chronic water deficits that negatively affect tree radial growth. This phenomenon has been widely studied in natural stands of native species but not in commercial plantations of exotic tree species. In central Chile, where the species is increasingly planted, the dynamics of stone pine (Pinus pinea L.) growth under drought have been little explored. We studied the impact of drought on four stone pine plantations growing in central Chile. We sampled and cross-dated a total of 112 trees from four sites, measured their tree-ring width (RWL) series, and obtained detrended series of ring width indices (RWIs). Then, we calculated three resilience indices during dry years (Rt, resistance; Rc, recovery; and Rs, resilience), and the correlations between the RWI series and seasonal climate variables. We found the lowest growth rate (1.94 mm) in the driest site (Peñuelas). Wet conditions in the previous winter and current spring favored growth. In the wettest site (Pastene), the growth rates were high (4.87 mm) and growth also increased in response to spring thermal amplitude. Overall, fast-growing trees were less resilient than slow-growing trees. Drought reduced stone pine stem growth and affected tree resilience to hydric deficit. At the stand level, growth rates and resistance were driven by winter and spring precipitation. Fast-growing trees were more resistant but showed less capacity to recover after a drought. In general, stone pine showed a high post-drought resilience due to a high recovery after drought events. The fact that we found high resilience in non-native habitats, opens new perspectives for stone pine cropping, revealing that it is possible to explore new areas to establish the species. We conclude that stone pine shows a good acclimation in non-native, seasonally dry environments.

Assessing the Impacts of Adaptation to Native-Range Habitats and Contemporary Founder Effects on Genetic Diversity in an Invasive Fish.

Species invading non-native habitats can cause irreversible environmental damage and economic harm. Yet, how introduced species become widespread invaders remains poorly understood. Adaptation within native-range habitats and rapid adaptation to new environments may both influence invasion success. Here, we examine these hypotheses using 7058 SNPs from 36 native, 40 introduced and 19 farmed populations of tench, a fish native to Eurasia. We examined genetic structure among these populations and accounted for long-term evolutionary history within the native range to assess whether introduced populations exhibited lower genetic diversity than native populations. Subsequent to infer genotype-environment correlations within native-range habitats, we assessed whether adaptation to native environments may have shaped the success of some introduced populations. At the broad scale, two glacial refugia contributed to the ancestry and genomic diversity of tench. However, native, introduced and farmed populations of admixed origin exhibited up to 10-fold more genetic diversity (i.e., observed heterozygosity, expected heterozygosity and allelic richness) compared to populations with predominantly single-source ancestry. The effects of introduction to a new location were also apparent as introduced populations exhibited fewer private alleles (mean = 9.9 and 18.9 private alleles in introduced and native populations, respectively) and higher population-specific Fst compared to native populations, highlighting their distinctiveness relative to the pool of allelic frequencies across tench populations. Finally, introduced populations with varying levels of genetic variation and similar genetic compositions have become established and persisted under strikingly different climatic and ecological conditions. Our results suggest that lack of prior adaptation and low genetic variation may not consistently hinder the success of introduced populations for species with a demonstrated ability to expand their native range.

Integrating otolith and genetic tools to reveal intraspecific biodiversity in a highly impacted salmon population.

Intraspecific biodiversity is vital for species persistence in an increasingly volatile world. By embracing methods that integrate information at different spatiotemporal scales, we can directly monitor and reconstruct changes in intraspecific biodiversity. Here we combined genetics and otolith biochronologies to describe the genotypic and phenotypic diversity of Chinook salmon (Oncorhynchus tshawytscha) in the Yuba River, California, comparing cohorts that experienced a range of hydroclimatic conditions. Yuba River salmon have been heavily impacted by habitat loss and degradation, and large influxes of unmarked hatchery fish each year have led to concern about introgression and uncertainty around the viability of its wild populations, particularly the rarer spring-run salmon. Otolith strontium isotopes showed that Yuba River origin fish represented, on average, 42% (range 7%-73%) of spawners across six return years (2009-2011, 2018-2020), with large interannual variability. The remainder of adult Chinook salmon in the river were primarily strays from the nearby Feather River hatchery, and since 2018 from the Mokelumne River hatchery. Among the Yuba-origin spawners, on average, 30% (range 14%-50%) exhibited the spring-run genotype. The Yuba-origin fish also displayed a variety of outmigration phenotypes that differed in the timing and size at which they left the Yuba river. Early-migrating fry dominated the returns (mean 59%, range 33%-89%), and their contribution rates were negatively correlated with freshwater flows. It is unlikely that fry survival rates are elevated during droughts, suggesting that this trend reflects disproportionately low survival of larger later migrating parr, smolts, and yearlings along the migratory corridor in drier years. Otolith daily increments indicated generally faster growth rates in non-natal habitats, emphasizing the importance of continuing upstream restoration efforts to improve in-river growing conditions. Together, these findings show that, despite a long history of habitat degradation and hatchery introgression, the Yuba River maintains intraspecific biodiversity that should be taken into account in future management, restoration, and reintroduction plans. The finding that genotypic spring-run are reproducing, surviving, and returning to the Yuba River every year suggests that re-establishment of an independent population is possible, although hatchery-wild interactions would need to be carefully considered. Integrating methods is critical to monitor changes in key genetic, physiological, and behavioral traits to assess population viability and resilience.

Trophic niche partitioning and intraspecific variation in food resource use in the genus Pangasianodon in a reservoir revealed by stable isotope analysis of multiple tissues.

Understanding the mechanism by which non-native fish species integrate into native communities is crucial for evaluating the possibility of their establishment success. The genus Pangasianodon, comprising Pangasianodon gigas and Pangasianodon hypophthalmus, has been introduced into reservoirs, which are non-native habitats, for fishery stock enhancement. P. gigas and P. hypophthalmus often successfully establish and co-occur in several Thai reservoirs, but there is little information on differences in food resource use between the two species. To investigate the trophic niche width of P. gigas and P. hypophthalmus in a Thai reservoir, we conducted stable carbon and nitrogen ratio (δ13C and δ15N) analyses. We examined the degree of individual specialization in both species using the δ13C and δ15N values of muscle and liver tissues, which provides long- and short-term diet information. The isotopic niches did not overlap between P. gigas and P. hypophthalmus. The δ15N value of P. gigas was significantly higher than that of P. hypophthalmus, whereas the δ13C value did not significantly differ between the two species. The isotopic niche sizes were larger in P. hypophthalmus than in P. gigas. Individual specialization was observed in P. hypophthalmus but not in P. gigas, indicating that intraspecific variation in food resource use was larger in P. hypophthalmus compared to P. gigas. These findings suggest that trophic niche partitioning was one of the factors facilitating the establishment success of P. gigas and P. hypophthalmus in a reservoir, but the establishment process may differ between the two species.

Comparative Biological Study on the Shrimp Scad Alepes djedaba Between Its Native and Non-Native Habitats, Egypt

Comparative Biological Study on the Shrimp Scad Alepes djedaba Between Its Native and Non-Native Habitats, Egypt

Experimental evidence for adaptive divergence in response to a warmed habitat reveals roles for morphology, allometry and parasite resistance.

Ectotherms are expected to be particularly vulnerable to climate change-driven increases in temperature. Understanding how populations adapt to novel thermal environments will be key for informing mitigation plans. We took advantage of threespine stickleback (Gasterosteus aculeatus) populations inhabiting adjacent geothermal (warm) and ambient (cold) habitats to test for adaptive evolutionary divergence using a field reciprocal transplant experiment. We found evidence for adaptive morphological divergence, as growth (length change) in non-native habitats related to head, posterior and total body shape. Higher growth in fish transplanted to a non-native habitat was associated with morphological shape closer to native fish. The consequences of transplantation were asymmetric with cold sourced fish transplanted to the warm habitat suffering from lower survival rates and greater parasite prevalence than warm sourced fish transplanted to the cold habitat. We also found divergent shape allometries that related to growth. Our findings suggest that wild populations can adapt quickly to thermal conditions, but immediate transitions to warmer conditions may be particularly difficult.

Signatures of local adaptation to current and future climate in phenology-related genes in natural populations of Quercus robur

BackgroundLocal adaptation is a key evolutionary process that enhances the growth of plants in their native habitat compared to non-native habitats, resulting in patterns of adaptive genetic variation across the entire geographic range of the species. The study of population adaptation to local environments and predicting their response to future climate change is important because of climate change.ResultsHere, we explored the genetic diversity of candidate genes associated with bud burst in pedunculate oak individuals sampled from 6 populations in Poland. Single nucleotide polymorphism (SNP) diversity was assessed in 720 candidate genes using the sequence capture technique, yielding 18,799 SNPs. Using landscape genomic approaches, we identified 8 FST outliers and 781 unique SNPs in 389 genes associated with geography, climate, and phenotypic variables (individual/family spring and autumn phenology, family diameter at breast height (DBH), height, and survival) that are potentially involved in local adaptation. Then, using a nonlinear multivariate model, Gradient Forests, we identified vulnerable areas of the pedunculate oak distribution in Poland that are at risk from climate change.ConclusionsThe model revealed that pedunculate oak populations in the eastern part of the analyzed geographical region are the most sensitive to climate change. Our results might offer an initial evaluation of a potential management strategy for preserving the genetic diversity of pedunculate oak.

The conversion of native savannah into pasturelands does not affect exclusively species diversity: Effects on physiological condition of a highly abundant dung beetle species.

Dung beetles are efficient indicators to obtain responses regarding the effects of land use change on biodiversity. Although the biological consequences of Cerrado conversion into pasture have been observed at the assemblage scale, there are no cues regarding the effects of tropical savanna conversion into pasture on physiological condition of dung beetle individuals. In this study, we evaluated whether native and non-native habitats in Cerrado affect the physiological condition and body traits of males and females of Phanaeus palaeno. The individuals were collected from a Cerrado fragment (sensu stricto) and an exotic pasture (Urochloa spp.). Physiological condition was assessed through the estimation of individuals' dry body mass, fat mass, and muscle mass. Body traits were estimated through individual body size and males' horn length. We did not find differences between dung beetle morphological traits between Cerrado and pastures. However, individuals collected in exotic pastures had lower dry mass and fat mass, but higher muscle mass, than in conserved Cerrado. Understanding how the land use change affects individuals' body condition is essential to maintain abundant and healthy populations of dung beetles in human-modified landscapes. Although the estimation of physiological condition is logistically more complex than species body traits, future studies aiming to present complex and finer ecological responses of dung beetles should incorporate physiological data to their approaches.

Skin lipids alone enable conspecific tracking in an invasive reptile, the Argentine black and white tegu lizard (Salvator merianae).

Locating potential mates in non-native habitats is one of the most important challenges faced by invasive vertebrate species. The Argentine black and white tegu lizard (Salvator merianae) is a major invasive reptile species in the contiguous United States and is rapidly expanding its range across Florida and the Southeast, in part due to inadequate management strategies and tools. Because a wide array of reptiles, especially squamates (snakes and lizards), have been well-studied for their reliance on chemical cues to locate conspecifics, our project aimed to isolate chemical cues from tegus and assess the ability of adult males and females to use only these cues to make navigation decisions within a Y-maze. Previously, we found that both males and females can follow conspecific scent trails, but the nature of the specific cues used by the tegus was unknown. In this study, we extracted skin lipids from male and female shed skins acquired during the breeding season then tested the extracts for bioactivity at different dilutions prior to Y-maze trials. Both sexes showed positive reactions (e.g., tongue-flicking, nose taps, scratching) to 2:1 skin lipid:hexane dilutions. In the Y-maze, males (n = 7) and females (n = 7) were run in three types of trailing scenarios with these skin lipid extracts: Male-only (pooled lipid extracts from male shed skins), Female-only (extracts from female shed skins), and Male vs. female. Regardless of the tegu lipid type present, tegus preferred to follow the conspecific lipid trail when paired with a neutral control (peanut oil; 2:1 dilution). They also preferred opposite-sex skin lipid trails when paired with same-sex skin lipid trails. We analyzed our results further by comparing them to those of Richard, Bukovich, et al. (2020). We found a synchronization effect of the skin lipids: sex differences in behavior detectable in the scent trail trials were absent when only conspecific skin lipids were present in the environment. Our results indicate that skin lipids alone are sufficient to facilitate mate tracking in S. merianae, these chemical cues induce reliable behavior, and extracted skin lipids have potential for modifying movement patterns of an invasive reptile in their non-native range. If leveraged in concert with current tegu management strategies (i.e., trapping), extracted skin lipids have the potential to bolster management efficacy but field trials are a requisite next step.

An overview of the distribution and ecology of the alien cyanobacteria species Raphidiopsis raciborskii, Sphaerospermopsis aphanizomenoides and Chrysosporum bergii in Europe

Cyanobacteria can form blooms and pose a threat to the functioning of freshwater ecosystems. Cyanobacterial invasions are expected to increase due to climate change. Alien species cause a decline in biodiversity by displacing native species, lead to extinctions, affect food webs, and produce cyanotoxins which potentially impact the environment and human health. Three species, Raphidiopsis raciborskii, Sphaerospermospis aphanizomenoides and Chrysosporum bergii, are considered non-native to European waters. Recently, they have expanded their native habitats and become established in temperate lakes. In this article, we provide a detailed overview of the countries where they are distributed and the occurrence of the blooms in Europe. We discuss the biotic and abiotic environmental factors that influence their establishment, as well as the characteristics of the species that make them so adaptable in non-native habitats. Understanding the interplay of these factors will allow us to better recognise patterns of invasiveness and predict their future threats to ecosystems.

Multi-scale assessment of roost selection by 'ōpe'ape'a, the Hawaiian hoary bat (Lasiurus semotus).

The Hawaiian hoary bat (Lasiurus semotus; Chiroptera: Vespertilionidae), commonly and locally known as 'ōpe'ape'a, is a solitary, insectivorous, and foliage-roosting species distributed across a wide range of habitats in lowland and montane environments. The species, as with many others in the Hawaiian archipelago, are facing a suite of challenges due to habitat loss and degradation, introduced predators and pests, and climate change. An understanding of the roost requirements of foliage-roosting tree bats is critical to their conservation as these habitats provide several important benefits to survival and reproduction. Because little is known about 'ōpe'ape'a roost ecology and considerable effort is needed to capture and track bats to roost locations, we examined resource selection at multiple spatial scales-perch location within a roost tree, roost tree, and forest stand. We used a discrete choice modeling approach to investigate day-roost selection and describe attributes of roost trees including those used as maternity roosts. 'Ōpe'ape'a were found roosting in 19 tree species and in an assortment of landcover types including native and non-native habitats. Our results are largely consistent with findings of other studies of foliage-roosting, insectivorous tree bats where bats selected roost locations that may offer protection and thermoregulatory benefits.

Ecological Strategies for Resource Use by Three Bromoviruses in Anthropic and Wild Plant Communities.

Ecological strategies for resource utilisation are important features of pathogens, yet have been overshadowed by stronger interest in genetic mechanisms underlying disease emergence. The purpose of this study is to ask whether host range and transmission traits translate into ecological strategies for host-species utilisation in a heterogeneous ecosystem, and whether host utilisation corresponds to genetic differentiation among three bromoviruses. We combine high-throughput sequencing and population genomics with analyses of species co-occurrence to unravel the ecological strategies of the viruses across four habitat types. The results show that the bromoviruses that were more closely related genetically did not share similar ecological strategies, but that the more distantly related pair did. Shared strategies included a broad host range and more frequent co-occurrences, which both were habitat-dependent. Each habitat thus presents as a barrier to gene flow, and each virus has an ecological strategy to navigate limitations to colonising non-natal habitats. Variation in ecological strategies could therefore hold the key to unlocking events that lead to emergence.

Reproduction and growth of the Red Sea goatfish Parupeneus forsskali in its new environment (Cyprus, eastern Mediterranean Sea)

In the Mediterranean Sea, six species of Mullidae have been recorded, four of them being alien to the area. The most recent arrival in the Mediterranean is the Red Sea goatfish (Parupeneus forsskali), which was first spotted there in the year 2000. Although P. forsskali is endemic to the Red Sea and the Gulf of Aden, it has recently expanded its distribution; it was confirmed in Cyprus in 2014. Since then, it has established a thriving population around the island, and is now commercially important. In the present study, the spawning season and gonad development of P. forsskali off the coast of Cyprus were studied, along with important biological parameters. Macroscopic and histological analyses of the gonads indicated five maturity phases for both ovaries and testes. The gonadal maturity phases and the gonadosomatic index indicated that P. forsskali spawns in the summer months, with the peak of the spawning season in July. Males were bigger, heavier, and more abundant than females, and the length-weight relationship was found to be TW=0.0065 TL3.17 for males and TW=0.0086 TL3.07 for females, both indicating positive allometric growth. The size at first sexual maturity (LM) was 14.2 cm for males and 11.8 cm for females. Five age groups were identified from the length-frequency distribution (0-4 years old). Age group 1 was the most dominant one, containing almost 60% of the sampled individuals. Natural mortality (M) declined with age, and the mean natural mortality coefficient across ages was 0.563 year-1. Overall, this is the first study that provides important information on the spawning season of the Red Sea goatfish and other estimations on various biological traits in its non-native habitat that can be of great importance for fisheries management.

The importance of structural and functional characteristics of tidal channels to smooth cordgrass invasion in the Yellow River Delta, China: Implications for coastal wetland management

Understanding the spatiotemporal landscape dynamics and spread pathways of invasive plants, as well as their interactions with geomorphic landscape features, are of great importance for predicting and managing their future range-expansion in non-native habitats. Although previous studies have linked geomorphic landscape features such as tidal channels to plant invasions, the potential mechanisms and critical characteristics of tidal channels that affect the landward invasion by Spartina alterniflora, an aggressive plant in global coastal wetlands, remain unclear. Here, using high-resolution remote-sensing images of the Yellow River Delta from 2013 to 2020, we first quantified the evolution of tidal channel networks by analyzing the spatiotemporal dynamics of their structural and functional characteristics. The invasion patterns and pathways of S. alterniflora were then identified. Based on the above-mentioned quantification and identification, we finally quantified the influences of tidal channel characteristics on S. alterniflora invasion. The results showed that tidal channel networks presented increasing growth and development over time, and their spatial structure evolved from simple to complex. The external isolated expansion of S. alterniflora played a dominant role during the initial invasion stage, and then they connected the discrete patches into the meadow through marginal expansion. Afterwards, tidal channel-driven expansion gradually increased and became the primary way during the late invasion stage, accounting for about 47.3%. Notably, tidal channel networks with higher drainage efficiency (shorter OPL, higher D and E) attained larger invasion areas. The longer the tidal channels and the more sinuous the channel structure, the greater the invasion potential by S. alterniflora. These findings highlight the importance of structural and functional properties of tidal channel networks in driving plant invasion landward, which should be incorporated into future control and management of invasive plants in coastal wetlands.

Assessing the Impact of Biodiversity (Species Evenness) on the Trophic Position of an Invasive Species (Apple Snails) in Native and Non-Native Habitats Using Stable Isotopes

Invasive apple snails negatively impact non-native habitats and human well-being. Here, the trophic position of Pomacea canaliculata in native habitats (Maldonado, Uruguay) and non-native habitats (Hangzhou, China and Hawaii, USA) are compared. Detritus samples and tissue samples from apple snails were collected in all sites. Trophic levels were calculated as the difference between the mean δ15N values of detritus samples and corresponding apple snail tissue samples, divided by the mean δ15N fractionation for nitrogen per trophic level in freshwater habitats. The mean δ15N values of detritus in sites served as a baseline (i.e., zero trophic level), allowing direct comparisons. Linear regression analysis established a correlation between species evenness and apple snail trophic level (R2 = 0.8602) in line with a Pearson’s product-moment correlation value (−0.83) and 95% confidence interval (−0.87, −0.77). Normal quartile plots indicated two normally distributed subsets of apple snail trophic-level data: (1) a biodiverse subset containing the Uruguayan and Chinese lake sites and (2) the homogenized Hawaiian and Chinese creek sites. A precipice value for species evenness (separating biodiversity from homogenization), between (3.7) and (2.4), once descended to or surpassed separates statistically distinct, normal distributions of invasive apple snail trophic-level data from diverse versus homogenized habitats.

Predicting the Potential Distribution of the Alien Invasive Alligator Gar Atractosteus spatula in China

Alligator gar Atractosteus spatula originates from North America but has been introduced into China recently. Considered an invasive fish, it may cause losses in the diversity and number of local species and in fish catch due to its predation on numerous aquatic animals in non-native habitats. A comprehensive study of this alien invasive species’ existing spatial patterns in relation to climatic variables is critical to understanding the conditions amenable to its distribution and controlling its further spread into potential range areas. We used MaxEnt and QGIS species distribution modeling to estimate the likely biogeographical range of A. spatula in China based on 36 validated distribution records and seven selected environmental variables. The highly suitable area was found primarily in a series of provinces extending from inland to coastal regions, covering southwest to south, central and east China. The model identified the minimum temperature of the coldest month (Bio6) and mean temperature of the warmest quarter (Bio10) as the strongest predictors of A. spatula distribution. The findings could offer scientific guidance for managing and preventing the spread of this invasive fish and hint at controlling invasive aquatic fauna.

High dispersal rates in hybrids drive expansion of maladaptive hybridization

Hybridization between native and invasive species, a major cause of biodiversity loss, can spread rapidly even when hybrids have reduced fitness. This paradox suggests that hybrids have greater dispersal rates than non-hybridized individuals, yet this mechanism has not been empirically tested in animal populations. Here, we test if non-native genetic introgression increases reproductive dispersal using a human-mediated hybrid zone between native cutthroat trout (<i>Oncorhynchus clarkii</i>) and invasive rainbow trout (<i>Oncorhynchus mykiss</i>) in a large and connected river system. We quantified the propensity for individuals to migrate from natal rearing habitats (migrate), reproduce in non-natal habitats (stray), and the joint probability of dispersal as a function of genetic ancestry. Hybrid trout with predominantly non-native rainbow trout ancestry were more likely to migrate as juveniles and to stray as adults. Overall, hybrids with greater than 50% rainbow trout ancestry were 5.7 times more likely to disperse than native or hybrid trout with small amounts of rainbow trout ancestry. Our results show a genetic basis for increased dispersal in hybrids that is likely contributing to the rapid expansion of invasive hybridization between these species. Management actions that decrease the probability of hybrid dispersal may mitigate the harmful effects of invasive hybridization on native biodiversity.

Carbon and nitrogen isotopic similarity between the endangered Darwin’s fox (Lycalopex fulvipes) and sympatric free-ranging dogs in Chiloé Island, Chile

ABSTRACT Darwin’s fox is an opportunistic omnivorous predator native to Chile classified as endangered by the IUCN Red List. Habitat use by Darwin’s foxes can be negatively affected by the presence of free-ranging dogs that range freely across native and non-native habitats and can be a source of fox mortality. The objective of this study was to analyze the isotopic similarity of Darwin’s fox and sympatric free-ranging dogs in Chiloé Island to determine the impact of anthropogenic environmental alterations on wild predators. We use hair samples to characterise and compare their δ 13C and δ 15N values and to evaluate isotopic similarity and isotope niches overlap. A generalised linear model was used to associate the isotope value with landscape variables (forest cover and vegetation type) and distance to the nearest house. We found no significant differences in δ 13C or δ 15N values between foxes and dogs, and a marginally significant isotope niche overlap (59.4 %). None of the selected variables at landscape and site scale were related to isotope values. Although our study is not a probe of direct contact between foxes and free-ranging dogs, the high isotopic similarity highlights the risk of pathogen spillover from free-ranging dogs to Darwin’s foxes.

Diet composition of an escaped captive-born southern tamandua (Tamandua tetradactyla) in a nonnative habitat in Asia.

Studies on the role of natural predatory instincts in captive‐born mammalian myrmecophagy are rare. Consequently, researchers rely extensively on case reports to learn more about the contexts in which predatory behavior occurs among such animals. In this study, we recorded an uncommon case of a captive‐born southern tamandua (Tamandua tetradactyla) that accidentally escaped from a zoo into a nonnative habitat in Asia. The southern tamandua was found alive 3 months later. Two fresh fecal samples were obtained, and the diet composition was examined. Three termite species (one family, three genera), and 14 ant species (four subfamilies, nine genera) were identified in the fecal samples. The studied southern tamandua preyed on terrestrial and arboreal ants and termites, as the wild populations of its species do. Ants of the subfamily Myrmicinae and termites of the subfamily Nasutitermitinae were the most abundant prey items in the samples, which is consistent with related reports on the wild populations. Soldier ants constituted <1% of the prey items in the fecal samples, suggesting that the southern tamandua likely avoided preying on ants of the soldier caste. Fungus‐growing termites Odontotermes (Isoptera: Macrotermitinae), which are not native to neotropical regions, were also ingested by the southern tamandua. This study provides information on how a captive‐born mammalian myrmecophagy applies its natural feeding instincts in nonnative natural settings.