Non-native Vertebrates Research Articles

Widespread population of invasive ferrets Mustela furo (Carnivora: Mustelidae) on the island of Madeira, Macaronesia

Abstract Invasive mammalian predators are arguably the most damaging group of alien animals for global biodiversity and their impacts are particularly damaging in endemic-rich insular ecosystems. Ferrets (Mustela furo) are well-known for their potential to establish self-sustaining feral populations. Yet, knowledge about their distribution and trophic interactions is scarce. Here, we provide ample evidence of a well-established and widespread population of ferrets on the subtropical island of Madeira (Portugal). Ferrets are using natural and human-dominated habitats, where they are preying on both native (e.g., Cory’s shearwaters (Calonectris borealis) and the endemic and IUCN Endangered Zino’s petrel (Pterodroma madeira)) and non-native vertebrates.

Current patterns of non-native vertebrate introductions in Brazil: introduction pathways and the contribution of niche dynamics in understanding the invasion process

Current patterns of non-native vertebrate introductions in Brazil: introduction pathways and the contribution of niche dynamics in understanding the invasion process

Diet, predators, and defensive behaviors of New Zealand harvestmen (Opiliones: Neopilionidae)

The Neopilionidae is a highly diversified harvestman family in New Zealand, comprising eight genera and 28 species. Although individuals of many species are abundant in the field, basic information on their natural history is absent. Here we describe the diet, predators, and defensive behaviors of 13 species across three genera, Forsteropsalis Taylor, 2013, Mangatangi Taylor, 2013, and Pantopsalis Simon, 1879. Using three years of field observations, we first identify food items for this family, finding that New Zealand neopilionids are opportunistic, generalist foragers with a diet composed of a wide variety of prey and scavenged soft-bodied invertebrates, including worms, amphipods, species from nine orders of insects, and two orders of arachnids (including conspecifics). We then describe the first known invertebrate predators of New Zealand harvestmen, including seven spider species, and conduct a review of the literature to collate a list of 32 species of native and non-native vertebrates (frogs, lizards, fish, birds, and mammals) that prey on harvestmen, including neopilionids. Finally, we describe the defensive behaviors of neopilionids, providing the first reports of autotomy and thanatosis in the family. In general, the diet of New Zealand neopilionids is similar to other harvestman species, and the list of predators includes mostly insectivorous taxa known to feed on harvestmen elsewhere. The defensive repertoire of neopilionids includes behaviors recorded for other species of Eupnoi, such as leg autotomy, but also unique behaviors that are only known for species of Dyspnoi and Laniatores, such as thanatosis.

Does the Introduction of Alien Species Represent a Sanitary Threat for Native Species? The Case of the Eastern Cottontail Sylvilagus floridanus in Italy.

Introduction of alien species is a well-known threat to biodiversity. Where newly introduced, alien species may pose a risk for the local ecological community by competing for resources or by introducing pathogens. Sylvilagus floridanus is an American lagomorph introduced into Europe in the second half of 20th century, for hunting. This study evaluated the structure and epidemiological characteristics of the gastrointestinal parasite community in an introduced population of S. floridanus in the Province of Alessandria (Piedmont Region—Italy). Three alien parasites were reported out of 271 animals: Obeliscoides cuniculi in the stomach, Trichostrongylus calcaratus in the small intestine, and Passarulus nonnanulatus in the large intestine. All these nematodes are commonly reported in S. floridanus in its natural range, but they represent alien species in Europe. The report of these alien parasites is an example of the unexpected consequences caused by the introduction of non-native vertebrates. The documented introduction of new pathogens may alter the parasite community of the native lagomorphs, with possible long-term effects on local ecological dynamics.

Natural history collections are critical resources for contemporary and future studies of urban evolution.

Urban environments are among the fastest changing habitats on the planet, and this change has evolutionary implications for the organisms inhabiting them. Herein, we demonstrate that natural history collections are critical resources for urban evolution studies. The specimens housed in these collections provide great potential for diverse types of urban evolution research, and strategic deposition of specimens and other materials from contemporary studies will determine the resources and research questions available to future urban evolutionary biologists. As natural history collections are windows into the past, they provide a crucial historical timescale for urban evolution research. While the importance of museum collections for research is generally appreciated, their utility in the study of urban evolution has not been explicitly evaluated. Here, we: (a) demonstrate that museum collections can greatly enhance urban evolution studies, (b) review patterns of specimen use and deposition in the urban evolution literature, (c) analyze how urban versus rural and native versus nonnative vertebrate species are being deposited in museum collections, and (d) make recommendations to researchers, museum professionals, scientific journal editors, funding agencies, permitting agencies, and professional societies to improve archiving policies. Our analyses of recent urban evolution studies reveal that museum specimens can be used for diverse research questions, but they are used infrequently. Further, although nearly all studies we analyzed generated resources that could be deposited in natural history collections (e.g., collected specimens), a minority (12%) of studies actually did so. Depositing such resources in collections is crucial to allow the scientific community to verify, replicate, and/or re‐visit prior research. Therefore, to ensure that adequate museum resources are available for future urban evolutionary biology research, the research community—from practicing biologists to funding agencies and professional societies—must make adjustments that prioritize the collection and deposition of urban specimens.

Potential problems of removing one invasive species at a time: a meta-analysis of the interactions between invasive vertebrates and unexpected effects of removal programs.

Although the co-occurrence of nonnative vertebrates is a ubiquitous global phenomenon, the study of interactions between invaders is poorly represented in the literature. Limited understanding of the interactions between co-occurring vertebrates can be problematic for predicting how the removal of only one invasive—a common management scenario—will affect native communities. We suggest a trophic food web framework for predicting the effects of single-species management on native biodiversity. We used a literature search and meta-analysis to assess current understanding of how the removal of one invasive vertebrate affects native biodiversity relative to when two invasives are present. The majority of studies focused on the removal of carnivores, mainly within aquatic systems, which highlights a critical knowledge gap in our understanding of co-occurring invasive vertebrates. We found that removal of one invasive vertebrate caused a significant negative effect on native species compared to when two invasive vertebrates were present. These unexpected results could arise because of the positioning and hierarchy of the co-occurring invasives in the food web (e.g., carnivore–carnivore or carnivore–herbivore). We consider that there are important knowledge gaps to determinate the effects of multiple co-existing invaders on native ecosystems, and this information could be precious for management.

Replacement of native by non-native animal communities assisted by human introduction and management on Isla Victoria, Nahuel Huapi National Park.

One of the possible consequences of biological invasions is the decrease of native species abundances or their replacement by non-native species. In Andean Patagonia, southern Argentina and Chile, many non-native animals have been introduced and are currently spreading. On Isla Victoria, Nahuel Huapi National Park, many non-native vertebrates were introduced ca. 1937. Records indicate that several native vertebrates were present before these species were introduced. We hypothesize that seven decades after the introduction of non-native species and without appropriate management to maintain native diversity, non-native vertebrates have displaced native species (given the known invasiveness and impacts of some of the introduced species). We conducted direct censuses in linear transects 500 m long (n = 10) in parallel with camera-trapping (1,253 camera-days) surveys in two regions of the island with different levels of disturbance: high (n = 4) and low (n = 6) to study the community of terrestrial mammals and birds and the relative abundances of native and non-native species. Results show that currently non-native species are dominant across all environments; 60.4% of census records and 99.7% of camera trapping records are of non-native animals. We detected no native large mammals; the assemblage of large vertebrates consisted of five non-native mammals and one non-native bird. Native species detected were one small mammal and one small bird. Species with the highest trapping rate were red and fallow deer, wild boar, silver pheasant (all four species are non-native) and chucao (a native bird). These results suggest that native species are being displaced by non-natives and are currently in very low numbers.

Links between two interacting factors, novel habitats and non-native predators, and aquatic invertebrate communities in a dryland environment

In dryland regions, increased demand for water has led to the reduction of natural aquatic habitats and threatens persisting aquatic habitats. In the Madrean Sky Islands (MSI), water demands have also resulted in the creation of novel aquatic habitats, including stock ponds. Stock ponds are important surrogate habitat for native species, yet little is known about the aquatic invertebrates utilizing these habitats. Additionally, stock ponds support non-native vertebrate predators including American bullfrogs (Lithobates catesbeiana) and Western mosquitofish (Gambusia affinis), and the effects of these predators on invertebrate communities in stock ponds are unknown. We explored similarities in invertebrate communities in stream pools and stock ponds and compared aquatic invertebrate community composition, abundance, and richness in stock ponds with and without non-native predators. We found that despite considerable functional (trait-based) overlap in aquatic invertebrate communities, a large majority (81%) of taxa were exclusive to either stock ponds or stream pools. Additionally, we observed few differences in aquatic invertebrate community composition, abundance, and richness in stock ponds with and without non-native predators. We discuss ecological implications of our observations, limitations of our approach, and the importance of future work in determining the role of stock ponds in conservation of the region’s aquatic invertebrates.

A Program to Eradicate Twenty-Four Nonnative Invasive Plant Species from Santa Cruz Island

Abstract. Santa Cruz Island, California, has been free of nonnative vertebrates since 2007, but nonnative invasive plants remain one of the most significant threats to the recovery of the island's native ecosystems. Just over one-fourth of the island's flora is comprised of nonnative, naturalized plant species. In 2007, an island-wide invasive plant survey indicated that several species were candidates for eradication based on factors such as their distribution, abundance, invasiveness, and known or projected harmful impacts on the native biota. In 2008, The Nature Conservancy (TNC) and Native Range, Inc., initiated a program to eliminate 15 invasive plant species from TNC's portion (76%) of the 246-km2 island. An additional 9 species were targeted in subsequent years. As of 2012, a total of 882 populations of 24 weed species have been mapped and treated, and 73% of these populations are considered inactive (dead), with no aboveground living biomass. The majority of the remaining active infestations are d...

Impacts of Wetland Restoration Efforts on an Amphibian Assemblage in a Multi-invader Community

The success of restoration in attaining wildlife conservation goals can be strongly dependent on both site-scale and landscape-scale habitat characteristics, particularly for species with complex life cycles. Wetland management activities typically target plant communities, and bottom-up responses in higher trophic levels may be dependent on spatially explicit habitat use. We surveyed plant and amphibian assemblages at 26 sites enrolled in the Wetlands Reserve Program (WRP) in the Willamette Valley, Oregon to determine the relative influence of plant management, non-native species, and surrounding landscape on amphibian counts across multiple life history stages. Explanatory variables negatively associated with native anuran counts included percent invasive plant cover, non-native fish presence, invasive bullfrog counts, and area of urban land cover. In addition, native anurans were positively associated with WRP site age, suggesting that the benefits of restored wetlands may increase over time. This study emphasized the importance of adaptive approaches to maintaining diverse communities in restored habitats by considering impacts of synergistic stressors in a multi-invader context. Although invasive plant management provided indirect benefits to native amphibians, the most effective way to enhance native amphibian populations may be through eliminating the strong top-down forces exerted by non-native vertebrates.

Effects of Native and Non-Native Vertebrate Mutualists on Plants

Extinctions can leave species without mutualist partners and thus potentially reduce their fitness. In cases where non-native species function as mutualists, mutualism disruption associated with species' extinction may be mitigated. To assess the effectiveness of mutualist species with different origins, we conducted a meta-analysis in which we compared the effectiveness of pollination and seed-dispersal functions of native and non-native vertebrates. We used data from 40 studies in which a total of 34 non-native vertebrate mutualists in 20 geographic locations were examined. For each plant species, opportunistic non-native vertebrate pollinators were generally less effective mutualists than native pollinators. When native mutualists had been extirpated, however, plant seed set and seedling performance appeared elevated in the presence of non-native mutualists, although non-native mutualists had a negative overall effect on seed germination. These results suggest native mutualists may not be easily replaced. In some systems researchers propose taxon substitution or the deliberate introduction of non-native vertebrate mutualists to reestablish mutualist functions such as pollination and seed dispersal and to rescue native species from extinction. Our results also suggest that in places where all native mutualists are extinct, careful taxon substitution may benefit native plants at some life stages.

Tracking non-native vertebrate species: indicator design for the United States of America

Basic information on the distribution, spread and impacts of non-native species in the USA is not available to those who shape national environmental policy. Although the USA spends billions of dollars annually on introduced species research, monitoring and control efforts, only a limited number of government agencies or private institutions are able to provide definitive reports on more than a handful of these species at a national scale. Research on invasive species is only of marginal practical value if the information cannot be succinctly and effectively transmitted to those who determine the management policies, budgets and objectives. To remedy this situation, a national-scale approach for monitoring established non-native species has been developed under the auspices of the Heinz Center as part of ‘The State of the Nation’s Ecosystems’ project. This paper specifically describes the strategies for reporting on indicators for non-native vertebrate species developed through inputs by experts from academia, industry, environmental organisations and government.

Distribution of Nonnative Aquatic Vertebrates in Western U.S. Streams and Rivers

AbstractNonnative aquatic vertebrates have been widely introduced across the western United States. We analyzed data from the Environmental Monitoring and Assessment Program's western pilot study to determine the occurrence of nonnative fish and amphibians and the proportion of stream length they occupied in streams of 12 conterminous western states. A total of 1,361 sites (including both probability sites and candidate reference sites) were sampled from 2000 to 2004. Of these, 711 probability sites had sufficient sampling effort and vertebrates present, representing a total assessed stream length of 213,600 km. Native and nonnative species numbers and proportionate abundances based on this stream length are reported for the entire study area, for three large‐scale ecoregions (Mountains, Xeric, and Plains), and for each state in the survey area. Sites with insufficient sampling effort or collection permit restrictions or in which no vertebrates were collected could not be assessed and represented an additional 90,000 km of stream length. An estimated 52 ± 4% (mean and 95% confidence interval) of the assessed stream length contained nonnative vertebrates. Nonnatives represented more than 50% of the individuals in 22 ± 3% of the assessed stream length. Nonnative vertebrates were present in 59 ± 10% of the assessed length represented by fourth‐order rivers and in 83 ± 6% of the assessed length represented by fifth‐order and larger rivers. From 30 to 33 nonnative species were found in each of the three ecoregions. Brook trout Salvelinus fontinalis, brown trout Salmo trutta, and rainbow trout Oncorhynchus mykiss were the most common nonnative aquatic vertebrates found in the study area based on the proportion of assessed stream length occupied. Of the 12 states surveyed, California accounted for the greatest number of nonnative taxa we collected (26) and Idaho the fewest (4).

Conservation Planning for US National Forests: Conducting Comprehensive Biodiversity Assessments

Abstract The US Forest Service has proposed new regulations under the National Forest Management Act that would replace a long-standing requirement that the agency manage its lands “to maintain viable populations of existing native and desired non-native vertebrate species.” In its place, the Forest Service would be obligated merely to assess ecosystem and species diversity. A landscape assessment process would rely on ecosystem-level surrogate measures, such as maps of vegetation communities and soils, to estimate species diversity. Reliance on such “coarse-filter” assessment techniques is problematic because there tends to be poor concordance between species distributions predicted by vegetation models and observations from species surveys. The proposed changes would increase the likelihood of continued declines in biodiversity and fail to address the original intent of the act. We contend that responsible stewardship requires a comprehensive strategy that includes not only coarse-filter, ecosystem-leve...

Pellet and bone accumulation at a colony of Western Gulls (Larus occidentalis)

Pellet and bone accumulation at a colony of Western Gulls (<i>Larus occidentalis</i>)