Wildlife forensics. Genomics has become a powerful tool to inform conservation measures

Genomics has become a powerful tool for conservationists to track individual animals, analyse populations and inform conservation management. But as helpful as these techniques are, they are not a substitute for stricter measures to protect threatened species.You might call him Queequeg. Like Herman Melville''s character in the 1851 novel Moby Dick, Howard Rosenbaum plies the seas in search of whales following old whaling charts. Standing on the deck of a 12 m boat, he brandishes a crossbow with hollow-tipped darts to harpoon the flanks of the whales as they surface to breathe (Fig 1). “We liken it to a mosquito bite. Sometimes there''s a reaction. Sometimes the whales are competing to mate with a female, so they don''t even react to the dart,” explained Rosenbaum, a conservation biologist and geneticist, and Director of the New York City-based Wildlife Conservation Society''s Ocean Giants programme. Rosenbaum and his colleagues use the darts to collect half-gram biopsy samples of whale epidermis and fat—about the size of a human fingernail—to extract DNA as part of international efforts to save the whales.Open in a separate windowFigure 1Howard Rosenbaum with a crossbow to obtain skin samples from whales. © Wildlife Conservation Society.Like Rosenbaum, many conservation biologists and wildlife managers increasingly rely on DNA analysis tools to identify species, determine sex or analyse pedigrees. George Amato, Director of the Sackler Institute for Comparative Genomics at the American Museum of Natural History in New York, NY, USA, said that during his 25-year career, genetic tools have become increasingly important for conservation biology and related fields. Genetic information taken from individual animals to the extent of covering whole populations now plays a valuable part in making decisions about levels of protection for certain species or populations and managing conflicts between humans and conservation goals.[…] many conservation biologists and wildlife managers increasingly rely on DNA analysis tools to identify species, determine sex or analyse pedigreesMoreover, Amato expects the use and importance of genetics to grow even more, given that conservation of biodiversity has become a global issue. “My office overlooks Central Park. And there are conservation issues in Central Park: how do you maintain the diversity of plants and animals? I live in suburban Connecticut, where we want the highest levels of diversity within a suburban environment,” he said. “Then, you take this all the way to Central Africa. There are conservation issues across the entire spectrum of landscapes. With global climate change, techniques in genetics and molecular biology are being used to look at issues and questions across that entire landscape.”Rosenbaum commented, “The genomic revolution has certainly changed the way we think about conservation and the questions we can ask and the things we can do. It can be a forensic analysis.” The data translates “into a conservation value where governments, conservationists, and people who actively protect these species can use this information to better protect these animals in the wild.”“The genomic revolution has certainly changed the way we think about conservation […]”Rosenbaum and colleagues from the Wildlife Conservation Society, the American Museum of Natural History and other organizations used genomics for the largest study so far—based on more than 1,500 DNA samples—about the population dynamics of humpback whales in the Southern hemisphere [1]. The researchers analysed population structure and migration rates; they found the highest gene flow between whales that breed on either side of the African continent and a lower gene flow between whales on opposite sides of the Atlantic, from the Brazilian coast to southern Africa. The group also identified an isolated population of fewer than 200 humpbacks in the northern Indian Ocean off the Arabian Peninsula, which are only distantly related to the humpbacks breeding off the coast of Madagascar and the eastern coast of southern Africa. “This group is a conservation priority,” Rosenbaum noted.He said the US National Oceanographic and Atmospheric Administration is using this information to determine whether whale populations are recovering or endangered and what steps should be taken to protect them. Through wildlife management and protection, humpbacks have rebounded to 60,000 or more individuals from fewer than 5,000 in the 1960s. Rosenbaum''s data will, among other things, help to verify whether the whales should be managed as one large group or divided into subgroups.He has also been looking at DNA collected from dolphins caught in fishing nets off the coast of Argentina. Argentine officials will be using the data to make recommendations about managing these populations. “We''ve been able to demonstrate that it''s not one continuous population in Argentina. There might be multiple populations that merit conservation protection,” Rosenbaum explained.The sea turtle is another popular creature that is high on conservationists'' lists. To get DNA samples from sea turtles, population geneticist and wildlife biologist Nancy FitzSimmons from the University of Canberra in Australia reverts to a simpler method than Rosenbaum''s harpoon. “Ever hear of a turtle rodeo?” she asked. FitzSimmons goes out on a speed boat in the Great Barrier Reef with her colleagues, dives into the water and wrangles a turtle on board so it can be measured, tagged, have its reproductive system examined with a laparoscope and a skin tag removed with a small scissor or scalpel for DNA analysis (Fig 2).Open in a separate windowFigure 2Geneticist Stewart Pittard measuring a sea turtle. © Michael P. Jensen, NOAA.Like Rosenbaum, she uses DNA as a forensic tool to characterize individuals and populations [2]. “That''s been a really important part, to be able to tell people who are doing the management, ‘This population is different from that one, and you need to manage them appropriately,''” FitzSimmons explained. The researchers have characterized the turtle''s feeding grounds around Australia to determine which populations are doing well and which are not. If they see that certain groups are being harmed through predation or being trapped in ‘ghost nets'' abandoned by fishermen, conservation measures can be implemented.FitzSimmons, who started her career studying the genetics of bighorn sheep, has recently been using DNA technology in other areas, including finding purebred crocodiles to reintroduce them into a wetland ecosystem at Cat Tien National Park in Vietnam. “DNA is invaluable. You can''t reintroduce animals that aren''t purebred,” she said, explaining the rationale for looking at purebreds. “It''s been quite important to do genetic studies to make sure you''re getting the right animals to the right places.”Geneticist Hans Geir Eiken, senior researcher at the Norwegian Institute for Agricultural and Environmental Research in Svanvik, Norway, does not wrestle with the animals he is interested in. He uses a non-intrusive method to collect DNA from brown bears (Fig 3). “We collect the hair that is on the vegetation, on the ground. We can manage with only a single hair to get a DNA profile,” he said. “We can even identify mother and cub in the den based on the hairs. We can collect hairs from at least two different individuals and separate them afterwards and identify them as separate entities. Of course we also study how they are related and try to separate the bears into pedigrees, but that''s more research and it''s only occasionally that we do that for [bear] management.”Open in a separate windowFigure 3Bear management in Scandinavia. (A) A brown bear in a forest in Northern Finland © Alexander Kopatz, Norwegian Institute for Agricultural and Environmental Research. (B) Faecal sampling. Monitoring of bears in Norway is performed in a non-invasive way by sampling hair and faecal samples in the field followed by DNA profiling. © Hans Geir Eiken. (C) Brown-bear hair sample obtained by so-called systematic hair trapping. A scent lure is put in the middle of a small area surrounded by barbed wire. To investigate the smell, the bears have to cross the wire and some hair will be caught. © Hans Geir Eiken. (D) A female, 2.5-year-old bear that was shot at Svanvik in the Pasvik Valley in Norway in August 2008. She and her brother had started to eat from garbage cans after they left their mother and the authorities gave permission to shoot them. The male was shot one month later after appearing in a schoolyard. © Hans Geir Eiken.Eiken said the Norwegian government does not invest a lot of money on helicopters or other surveillance methods, and does not want to not bother the animals. “A lot of disturbing things were done to bears. They were trapped. They were radio-collared,” he said. “I think as a researcher we should replace those approaches with non-invasive genetic techniques. We don''t disturb them. We just collect samples from them.”Eiken said that the bears pose a threat to two million sheep that roam freely around Norway. “Bears can kill several tons of them everyday. This is not the case in the other countries where they don''t have free-ranging sheep. That''s why it''s a big economic issue for us in Norway.” Wildlife managers therefore have to balance the fact that brown bears are endangered against the economic interests of sheep owners; about 10% of the brown bears are killed each year because they have caused damage, or as part of a restricted ‘licensed'' hunting programme. Eiken said that within two days of a sheep kill, DNA analysis can determine which species killed the sheep, and, if it is a bear, which individual. “We protect the females with cubs. Without the DNA profiles, it would be easy to kill the females, which also take sheep of course.”Wildlife managers […] have to balance the fact that brown bears are endangered against the economic interests of sheep owners…It is not only wildlife management that interests Eiken; he was part of a group led by Axel Janke at the Biodiversity and Climate Research Centre in Frankfurt am Main, Germany, which completed sequencing of the brown bear genome last year. The genome will be compared with that of the polar bear in the hope of finding genes involved in environmental adaptation. “The reason why [the comparison is] so interesting between the polar bear and the brown bear is that if you look at their evolution, it''s [maybe] less than one million years when they separated. In genetics that''s not a very long time,” Eiken said. “But there are a lot of other issues that we think are even more interesting. Brown bears stay in their caves for 6 months in northern Norway. We think we can identify genes that allow the bear to be in the den for so long without dying from it.”Like bears, wolves have also been clashing with humans for centuries. Hunters exterminated the natural wolf population in the Scandinavian Peninsula in the late nineteenth century as governments protected reindeer farming in northern Scandinavia. After the Swedish government finally banned wolf hunting in the 1960s, three wolves from Finland and Russia immigrated in the 1980s, and the population rose to 250, along with some other wolves that joined the highly inbred population. Sweden now has a database of all individual wolves, their pedigrees and breeding territories to manage the population and resolve conflicts with farmers. “Wolves are very good at causing conflicts with people. If a wolf takes a sheep or cattle, or it is in a recreation area, it represents a potential conflict. If a wolf is identified as a problem, then the local authorities may issue a license to shoot that wolf,” said Staffan Bensch, a molecular ecologist and ornithologist at Lund University in Sweden.Again, it is the application of genomics tools that informs conservation management for the Scandinavian wolf population. Bensch, who is best known for his work on population genetics and genomics of migratory songbirds, was called to apply his knowledge of microsatellite analysis. The investigators collect saliva from the site where a predator has chewed or bitten the prey, and extract mitochondrial DNA to determine whether a wolf, a bear, a fox or a dog has killed the livestock. The genetic information potentially can serve as a death warrant if a wolf is linked with a kill, and to determine compensation for livestock owners.The genetic information potentially can serve as a death warrant if a wolf is linked with a kill…Yet, not all wolves are equal. “If it''s shown to be a genetically valuable wolf, then somehow more damage can be tolerated, such as a wolf taking livestock for instance,” Bensch said. “In the management policy, there is genetic analysis of every wolf that has a question on whether it should be shot or saved. An inbred Scandinavian wolf has no valuable genes so it''s more likely to be shot.” Moreover, Bensch said that DNA analysis showed that in at least half the cases, dogs were the predator. “There are so many more dogs than there are wolves,” he said. “Some farmers are prejudiced that it is the wolf that killed their sheep.”According to Dirk Steinke, lead scientist at Marine Barcode of Life and an evolutionary biologist at the Biodiversity Institute of Ontario at the University of Guelph in Canada, DNA barcoding could also contribute to conservation efforts. The technique—usually based on comparing the sequence of the mitochondrial CO1 gene with a database—could help to address the growing trade in shark fins for wedding feasts in China and among the Chinese diaspora, for example. Shark fins confiscated by Australian authorities from Indonesian ships are often a mess of tissue; barcoding helps them to identify the exact species. “As it turns out, some of them are really in the high-threat categories on the IUCN Red List of Threatened Species, so it was pretty concerning,” Steinke said. “That is something where barcoding turns into a tool where wildlife management can be done—even if they only get fragments of an animal. I am not sure if this can prevent people from hunting those animals, but you can at least give them the feedback on whether they did something illegal or not.”Steinke commented that DNA tools are handy not only for megafauna, but also for the humbler creatures in the sea, “especially when it comes to marine invertebrates. The larval stages are the only ones where they are mobile. If you''re looking at wildlife management from an invertebrate perspective in the sea, then these mobile life stages are very important. Their barcoding might become very handy because for some of those groups it''s the only reliable way of knowing what you''re looking at.” Yet, this does not necessarily translate into better conservation: “Enforcement reactions come much quicker when it''s for the charismatic megafauna,” Steinke conceded.“Enforcement reactions come much quicker when it''s for the charismatic megafauna”Moreover, reliable identification of animal species could even improve human health. For instance, Amato and colleagues from the US Centers for Disease Control and Prevention demonstrated for the first time the presence of zoonotic viruses in non-human primates seized in American airports [3]. They identified retroviruses (simian foamy virus) and/or herpesviruses (cytomegalovirus and lymphocryptovirus), which potentially pose a threat to human health. Amato suggested that surveillance of the wildlife trade by using barcodes would help facilitate prevention of disease. Moreover, DNA barcoding could also show whether the meat itself is from monkeys or other wild animals to distinguish illegally hunted and traded bushmeat—the term used for meat from wild animals in Africa—from legal meats.Amato''s group also applied barcoding to bluefin tuna, commonly used in sushi, which he described as the “bushmeat of the developed world”, as the species is being driven to near extinction through overharvesting. Developing barcodes for tuna could help to distinguish bluefin from yellowfin or other tuna species and could assist measures to protect the bluefin. “It can be used sort of like ‘Wildlife CSI'' (after the popular American TV series),” he said.As helpful as these technologies are […] they are not sufficient to protect severely threatened species…In fact, barcoding for law enforcement is growing. Mitchell Eaton, assistant unit leader at the US Geological Survey New York Cooperative Fish and Wildlife Research Unit in Ithaca, NY, USA, noted that the technique is being used by US government agencies such as the FDA and the US Fish & Wildlife Service, as well as African and South American governments, to monitor the illegal export of pets and bushmeat. It is also used as part of the United Nations'' Convention on Biological Diversity for cataloguing the Earth''s biodiversity, identifying pathogens and monitoring endangered species. He expects that more law enforcement agencies around the world will routinely apply these tools: “This is actually easy technology to use.”In that way, barcoding as well as genetics and its related technologies help to address a major problem in conservation and protection measures: to monitor the size, distribution and migration of populations of animals and to analyse their genetic diversity. It gives biologists and conservations a better picture of what needs extra protective measures, and gives enforcement agencies a new and reliable forensic tool to identify and track illegal hunting and trade of protected species. As helpful as these technologies are, however, they are not sufficient to protect severely threatened species such as the bluefin tuna and are therefore not a substitute for more political action and stricter enforcement.     

Social personality polymorphism and the spread of invasive species: a model

Ecological invasions are a major worldwide problem exacting tremendous economic and ecological costs. Efforts to explain variability in invasion speed and impact by searching for combinations of ecological conditions and species traits associated with invasions have met with mixed success. We use a simulation model that integrates insights from life-history theory, animal personalities, network theory, and spatial ecology to derive a new mechanism for explaining variation in animal invasion success. We show that spread occurs most rapidly when (1) a species includes a mix of life-history or personality types that differ in density-dependent performance and dispersal tendencies, (2) the differences between types are of intermediate magnitude, and (3) patch connections are intermediate in number and widely spread. Within-species polymorphism in phenotype (e.g., life-history strategies or personality), a feature not included in previous models, is important for overcoming the fact that different traits are associated with success in different stages of the invasion process. Polymorphism in sociability (a personality type) increases the speed of the invasion front, since asocial individuals colonize empty patches and facilitate the local growth of social types that, in turn, induce faster dispersal by asocials at the invasion edge. The results hold implications for the prediction of invasion impacts and the classification of traits associated with invasiveness.     

Genomic tools for evolution and conservation in the chimpanzee: Pan troglodytes ellioti is a genetically distinct population

In spite of its evolutionary significance and conservation importance, the population structure of the common chimpanzee, Pan troglodytes, is still poorly understood. An issue of particular controversy is whether the proposed fourth subspecies of chimpanzee, Pan troglodytes ellioti, from parts of Nigeria and Cameroon, is genetically distinct. Although modern high-throughput SNP genotyping has had a major impact on our understanding of human population structure and demographic history, its application to ecological, demographic, or conservation questions in non-human species has been extremely limited. Here we apply these tools to chimpanzee population structure, using ～700 autosomal SNPs derived from chimpanzee genomic data and a further ～100 SNPs from targeted re-sequencing. We demonstrate conclusively the existence of P. t. ellioti as a genetically distinct subgroup. We show that there is clear differentiation between the verus, troglodytes, and ellioti populations at the SNP and haplotype level, on a scale that is greater than that separating continental human populations. Further, we show that only a small set of SNPs (10-20) is needed to successfully assign individuals to these populations. Tellingly, use of only mitochondrial DNA variation to classify individuals is erroneous in 4 of 54 cases, reinforcing the dangers of basing demographic inference on a single locus and implying that the demographic history of the species is more complicated than that suggested analyses based solely on mtDNA. In this study we demonstrate the feasibility of developing economical and robust tests of individual chimpanzee origin as well as in-depth studies of population structure. These findings have important implications for conservation strategies and our understanding of the evolution of chimpanzees. They also act as a proof-of-principle for the use of cheap high-throughput genomic methods for ecological questions.     

Trying to collapse a population for conservation: commercial trade of a marine invasive species by artisanal fishers

Implementing new and effective control strategies to reduce populations of invasive species is needed to offset their negative impacts worldwide. The spread of Indo-Pacific lionfish (Pterois sp.) through much of the western Atlantic has been one of the most publicized marine invasions globally, and is considered a major biodiversity threat whose longer-term impacts are still uncertain. Marine managers have explored several strategies to control lionfish, such as fishing tournaments (derbies) and commercial fisheries. Commercial fisheries for invasive species are controversial because they could create perverse incentives to maintain these populations, and they have never been demonstrated to successfully control target populations. We analyzed the development and impacts of an opportunistic fishing operation aimed at commercializing invasive lionfish in the Mexican Caribbean. We examined official lionfish landings and compared them to catches from lionfish derbies and lionfish densities from locations in the state of Quintana Roo, Mexico. We found that commercial fishers, particularly from one fishing cooperative on Cozumel Island, were effective at catching lionfish, with landings peaking at 20,000 individuals in 2014. This number is comparable to the number of lionfish caught in derbies across the entire Caribbean in the same year. Ecological survey data suggest a?~?60% reduction in lionfish density on Cozumel reefs over two years (2013–2015), matching the peak landings in the lionfish fishing operation. However, the fishery’s apparent success as a control tool during the time window analyzed seemed to trigger its own demise: a decline in landings was followed by evaporating market interest and loss of economic viability. If fisheries are to be established and used as management strategies to control future invasions, managers must develop strategic collaboration plans with commercial fishing partners.

     

Optimizing the location of watercraft inspection stations to slow the spread of aquatic invasive species

The accidental spread of aquatic invasive species (AIS) by recreational boaters is a major concern of state and county environmental planners in the USA. While programs for watercraft inspection to educate boaters and slow AIS spread are common practice, large numbers of boats and waterbodies, together with limited budgets, make program design difficult. To facilitate program design, we developed an integer programming model for allocation of scarce inspection resources among lakes. Our model uses species-specific infestation status of lakes and estimates of boat movement between lakes. The objective is to select lakes for inspection stations to maximize the number of risky boats inspected, where risky boats are ones that move from infested to uninfested lakes. We apply our model in Stearns County in central Minnesota, USA, to prioritize lakes for inspection stations and evaluate alternative management objectives. With an objective of protecting uninfested lakes within and outside Stearns County, the optimal policy is to locate stations at infested lakes having the most boats departing for uninfested lakes inside and outside the county. With an objective of protecting only Stearns County lakes, the optimal policy is to locate stations at both infested and uninfested lakes having the riskiest boats arriving from within and outside the county and departing to in-county lakes. The tradeoff between these objectives is significant.

     

The potential efficacy and application of freshwater and hypersaline immersion to control the spread of a marine invasive species

Introduced into New Zealand waters in 2008, the polychaete worm Sabella spallanzanii (Gmelin, 1791) is a marine invasive species with potential for significant ecological and economic impact. Within New Zealand, efforts to cope with this pest have focused on containment as efficacious control methods are in their infancy. To remedy this, we tested the efficacy of hyper-saline (50‰) and hypo-saline (0‰) baths as a potential control method for this species. Specimens of S. spallanzanii were collected from within the Auckland region and exposed to salinity treatments for up to 1440 min (24 h) and mortality rates were compared using LT₅₀ i.e. number of minutes taken for 50% of worms to die. Specimens subjected to hypo-saline conditions resulted in an LT₅₀ of 31.0 min compared to 132.0 min for hyper-saline conditions. Accordingly, hypo-saline dips have potential as an environmentally safe and cost-effective management method for maintenance of recreational vessels and other marine structures (e.g. aquaculture gear and shellfish stocks) that are heavily fouled with S. spallanzanii.     

Natives adapting to invasive species: ecology,genes, and the sustainability of conservation

Contemporary anthropogenic evolution is common. Biological invasions are an especially dynamic form of novel selection. This paper considers how native species evolve in response to biological invasions and the potential consequences of such evolution. Among numerous recent cases, the most widely reported instances are of phytophagous insects shifting onto introduced host plants. For example, our studies show that in North America and Australia, soapberry bugs evolved substantially after colonizing introduced hosts. Such cases permit close estimation of evolution’s direction and rate, and we have used cross-rearing studies of derived and ancestral-type populations to measure changes in reaction norms and performance tradeoffs. Different fitness traits have followed very different paths in evolving to their current phenotypic values. Our hybridization studies show that the genetic architecture of these adaptations involves a surprising degree of non-additive variation (epistasis, dominance). The importance of non-additive genetic variation in rapid evolution will be clarified as more studies take advantage of similar situations. As appreciation grows for the deep contemporary interplay of evolution and ecology, debate about qualitative terms describing evolution’s rate will become less relevant. From a conservation standpoint, contemporary evolution in native species presents challenges for ecologically appropriate and sustainable management. Evolving natives and invaders may reconfigure contemporary and future communities. Adaptive evolution may also enhance native communities’ capacity to control invasive populations.     

How reproductive ecology contributes to the spread of a globally invasive fish

Invasive freshwater fish represent a major threat to biodiversity. Here, we first demonstrate the dramatic, human-mediated range expansion of the Trinidadian guppy (Poecilia reticulata), an invasive fish with a reputation for negatively impacting native freshwater communities. Next, we explore possible mechanisms that might explain successful global establishment of this species. Guppies, along with some other notable invasive fish species such as mosquitofish (Gambusia spp.), have reproductive adaptations to ephemeral habitats that may enable introductions of very small numbers of founders to succeed. The remarkable ability of single pregnant guppies to routinely establish viable populations is demonstrated using a replicated mesocosm set up. In 86% of cases, these populations persisted for two years (the duration of the experiment). Establishment success was independent of founder origin (high and low predation habitats), and there was no loss of behavioural performance amongst mesocosm juveniles. Behavioural "signatures" of the founding locality were, however, evident in mesocosm fish. Our results demonstrate that introductions consisting of a single individual can lead to thriving populations of this invasive fish and suggest that particular caution should be exercised when introducing this species, or other livebearers, to natural water bodies.     

The habitat and conduit functions of roads in the spread of three invasive plant species

Nonnative plant species commonly occur along roadsides, and populations are often assumed to invade by spread along the road axis. To distinguish between the function of roadsides as movement corridors and as habitat, nonnative plant species were surveyed along roads in deciduous forest sites in southeastern Ohio, USA. The importance of road proximity was tested by comparing nonnative species abundance in 100 m transects along roads with transects in undisturbed forest. Nonnative species were most abundant and most frequently observed in roadside sites in valleys. Three common species were chosen for closer scrutiny. In a seed sowing experiment roads and open sites proved to be better locations for the germination and growth of Microstegium vimineum than non-roadside and closed-canopy sites. Tussilago farfara and Rosa multiflora occurred in a small number of disjunct patches suggesting infrequent arrival in the sampled transects. Both species were strongly clustered at scales consistent with diffusive spread by vegetative growth and short-range seed dispersal. Comparisons of distributions parallel and perpendicular to roads showed no evidence for enhanced dispersal along the road axis. Microstegium distributions were correlated with local light availability implying site saturation. Microstegium micro-distributions suggested that spread along the road axis was facilitated by movement of dormant seeds in road maintenance. Thus, roadsides appear to function as both habitat and a conduit for population expansion, with the rate of spread dependent on the life history of the individual species. These results suggest a hierarchical process of regional invasion, with different dispersal mechanisms functioning at different spatial scales.     

Estimating the financial costs of freshwater invasive species in Great Britain: a standardized approach to invasive species costing

Both ecological and economic impacts factor into invasive alien species (IAS) management considerations; however, economic impacts are often difficult to assess, much less quantify. Studies frequently aggregate identified financial costs as a proxy for IAS economic impacts, but these aggregate figures are often generated in an ad hoc fashion. Such estimates typically sum disparate costs, which might vary with respect to precision, accuracy, and scope. A standardized approach for IAS costing would better enable the comparison of cost estimates between taxa and across studies by controlling for surveying and scaling inconsistencies. This study develops a simple, survey-based approach to generate economic cost estimates for non-native freshwater invasive species (FIS) in Great Britain. The approach scales an average cost for each species by a ratio of management effort, thereby estimating the actual, annual expenditures incurred by a variety of stakeholders. The Great Britain-wide cost of controlling FIS is estimated to be approximately ￡26.5 million year⁻¹; however, the costs of control could total ￡43.5 million year⁻¹ if management efforts were undertaken at all FIS infested locations. Cost estimates are highest for Canadian pondweed (Elodea canadensis), a particularly widespread species, and for the zebra mussel (Dreissena polymorpha), which adversely impacts both industrial water users and boaters. This assessment of the relative economic impacts between species provides policy-makers with a monetary basis for rank-ordering species’ economic impacts and prioritizing management efforts. In addition, the cost assessment approach developed in this study could serve as a model for IAS economic impact assessments elsewhere.     

Control of invasive species for the conservation of biodiversity in Mediterranean islands. The LIFE PonDerat project in the Pontine Archipelago,Italy

We present the EU LIFE PonDerat project, which is aimed at restoring the natural ecosystems of the Pontine Archipelago, a group of islands located off the western coast of Italy. The spread of invasive species is a major environmental threat on these islands, which are rich in rare habitats and endemic species and are important sites for the conservation of Mediterranean biodiversity. The project focuses on the conservation of species and habitats that are protected by EU laws but are currently threatened by introduced plants and animals. The main targets of the control measures are black rats, feral goats, mouflons and invasive plants of the genus Carpobrotus. Conservation measures focus on the shearwaters Puffinus yelkouan and Calonectris diomedea, which are endemic to the Mediterranean and are listed in Annex I of the European Bird Directive. Conservation measures also focus on island habitats of great biogeographical value, which are listed in Annex I of the European Habitats Directive and are seriously threatened by introduced herbivores and by invasive plants. The main outcome expected from this project is that the restoration of ecosystem functions will enhance the breeding success and population size of shearwaters and lead to the recovery of target habitats.     

Nested communities,invasive species and Holocene extinctions: evaluating the power of a potential conservation tool

General ecological methods and models that require a minimum amount of information yet are still able to inform conservation planning are particularly valuable. Nested subset analysis has been advocated as such a tool for the prediction of extinction-prone species and populations. However, such advocacy has not been without skepticism and debate, and in the majority of published examples assessing extinction vulnerability, actual extinctions are based on assumptions rather than direct evidence. Here, we empirically test the power of nested subset analysis to predict extinction-prone species, using documented Holocene insular mammal extinctions on three island archipelagos off the west coast of North America. We go on to test whether the introduction of invasive mammals promotes nestedness on islands via extinction. While all three archipelagos were significantly nested before and after the extinction events, nested subset analysis largely failed to predict extinction patterns. We also failed to detect any correlations between the degree of nestedness at the genus-level with area, isolation, or species richness and extinction risk. Biogeography tools, such as nested subset analysis, must be critically evaluated before they are prescribed widely for conservation planning. For these island archipelagos, it appears detailed natural history and taxa-specific ecology may prove critical in predicting patterns of extinction risk.     

Experimental tools to monitor the dynamics of endothelial barrier function: a survey of in vitro approaches

Endothelial cells line the inner surface of all blood vessels and constitute a selective barrier between blood and tissue. Permeation of solutes across the endothelial cell monolayer occurs either paracellularly through specialized endothelial cell-cell junctions or transcellularly via special transport mechanisms including transcytosis, via the formation of transcellular channels, or by cell membrane transport proteins. Several in vitro assays have been developed in the past few decades to analyze the molecular mechanisms of transendothelial permeability. Measurement of the electrical resistance of the cell monolayer has proven to be particularly suitable for analyzing paracellular barrier function with high-time resolution over long time periods. We review the various permeability assays and focus on the electrical impedance analysis of endothelial cell monolayers. We also address current progress in the development of techniques used to investigate endothelial permeability with high-lateral resolution and under mechanical loads.     

Impacts of the emerald ash borer (EAB) eradication and tree mortality: potential for a secondary spread of invasive plant species

Since the discovery of the emerald ash borer in 2002, eradication efforts have been implemented in an attempt to eliminate or contain the spread of this invasive beetle. The eradication protocol called for the removal of every ash tree within a 0.8 km radius around an infested tree. In 2005 this study was established to identify environmental changes attributed to the eradication program and measure subsequent shifts in forest community composition and structure. We conducted this study in Ohio and compared areas that received the eradication treatment (ash trees cut down), to areas that were left uncut, (ash still standing). The goal of this project was to identify how the plant community is responding in these two areas. The eradication protocol accelerated the formation and size of gaps within the forest and thus increased the duration and intensity of light penetrating through to the forest floor. In addition, the use of track vehicles for removal of cut trees resulted in significant soil compaction. The resultant plant community had greater species diversity (H′). When specific species composition differences were compared, an increase in the establishment of invasive plant species was detected in areas that received eradication efforts compared to those that did not. Invasive species accounted for 18.7% of the total herbaceous cover in this highly disturbed environment which included Cirsium arvense, Rhamnus cathartica and 2 species of Lonicera. In contrast, invasive species accounted for <1% of the total herbaceous cover in the undisturbed uncut areas.     

A test for a cost of opportunism in invasive species in the Commelinaceae

Many invasive species can respond opportunistically to favorable growing conditions. In a previous work, we found that invasive species in the family Commelinaceae were more opportunistic than their noninvasive congeners and could therefore outperform noninvasive relatives in an environment with abundant resources and no competition. Contrary to the expectation that superior performance under favorable conditions comes at the cost of reduced performance under stressful conditions, invasive species did not perform more poorly relative to noninvasive congeners under any conditions we examined. Here we expand our search for potential costs of opportunism in invasive species to additional environmental conditions in which invasive taxa have been shown or predicted to perform poorly. We grew four invasive and four noninvasive species in environments consisting of all possible combinations of high and low soil resources and presence and absence of clipping (removal of aboveground biomass). We also fed leaves of each species to a generalist herbivore to assess resistance to herbivory. We found that the advantage of invasive species is reduced but not eliminated by low soil resources and clipping. At low soil resources, invasive species produced softer leaves than noninvasive species and might therefore be less resistant to generalist herbivory than noninvasive species, although a direct comparison of resistance in a no-choice bioassay revealed no difference. The invasive species outperformed noninvasive species only under the most favorable conditions, and the noninvasive species did not outperform the invasive species in any environment.     

Evidence for phylogeographic structure in Lolium species related to the spread of agriculture in Europe. A cpDNA study

In order to explain the present distribution area of natural populations of two forage grasses species (Lolium perenne and L. rigidum), we studied genetic variation for maternally inherited chloroplast DNA (cpDNA) in 447 individual plants from 51 natural populations sampled throughout Europe and the Middle East. The detection of polymorphism by restriction analysis of PCR-amplified cpDNA fragments resulted in the identification of 15 haplotypes. Hierarchical analysis of chloroplastic diversity showed a high level of within-population diversity while, for both species, we found that about 40% of the total diversity still remains among populations. The use of previous isozymes data enabled us to estimate the pollen to seed flow ratio: pollen flow appears to be 3.5 times greater than seed flow for L. perenne and 2.2 times higher for L. rigidum. A stepwise weighted genetic distance between pairs of populations was calculated using the haplotypes frequencies of populations. A hierarchical clustering of populations clearly divides the two species, while two main clusters of L. perenne populations show a strong geographical structure. Different scenario are proposed for explaining the distribution area of the two species. Finally, evidence attesting that these geographical structures are related to the spread of agriculture in Europe are presented and discussed. Received: 5 November 1999 / Accepted: 24 November 1999     

Fluctuating asymmetry as a bio-marker to account for in conservation and management of cave-dwelling species

The applicability of fluctuating asymmetry (FA) in conservation biology as a bio-marker and an early warning system have been examined in various groups of animals. However, cave-dwelling invertebrates have gotten little attention and yet caves have no biological management. Thus, developing a bio-marker to identify early responses of cave-dwelling species to stress provides a valuable tool to account for in future conservation and management programs. We examined whether FA can be used as a bio-marker of relaxed selection for cave-dwelling invertebrates. Specifically, we compared FA levels of pedipalps and two segments of chelicerae (chelicel1 and chelicel2) between cave and surface habitats and among populations in a troglophilic harvestman specie, Paranemastoma sillii sillii (Herman, 1871). Under the assumption that cave environment exerts relaxed selection we hypothesised that cave-dwelling harvestmen express higher degree of FA than surface-dwelling harvestmen. Because female and male harvestmen use the pediplaps differently, we assumed sex-specific selective pressures and further examined the effect of sex and habitat (cave vs surface) and sex interaction on FA levels. We hypothesised no differences in the levels of FA among harvestman cave populations, because of the idea that relaxed selection is responsible for higher levels of FA in cave-dwelling harvestmen rather than environmental stress. We found significant habitat sex interactions in the FA of the pedipalp. Interactions of population and sex had a significant effect on pedipalp and chelicel2 FA. These results partially support the idea that FA responds to differences in the strength of selection. Although we cannot fully disentangle the mechanisms of natural selection affecting FA and the study of trait asymmetry should be combined with studies of other sources of stress (i.e. genetic stress, predation, prey availability) we conclude that FA could be a bioindicator to be used as a tool in conservation and management of cave.     

Reconstructing the history of introduction and spread of the invasive species, Lantana, at three spatial scales in India

This study sought to reconstruct the history of Lantana invasion and spread in India by considering two questions; (a) from where, by who, and when were Lantana species introduced into India? and (b) given its long history in the country, is it still spreading or more or less stable? We critically evaluated the archival and historical information on plant imports by the European powers into India during the period before and after British colonization. We then reconstructed the path of spread by analyzing the spatio-temporal patterns of occurrence and distribution of Lantana in India at both the national and local scale using a GIS platform. The spread of Lantana across the globe started as early as the 1690s. The European colonial powers moved the plants from Latin America to Europe and to their colonial countries in the early 1800s. Lantana species were introduced in India from 1807 onwards and thereafter the colonial powers moved this plant across the country. Following its introduction into India, the spread of Lantana across the country, either through subsequent multiple introductions from Europe to different British cantonments, or through moving the plants between cantonments within India, were reasonably rapid spanning only a few decades. In the absence of a rigorous control program, the spread of Lantana has gone on unabated and thereby impacting both wildlife and biodiversity.