Cryptic invasion drives phenotypic changes in central European threespine stickleback

Cryptic invasions are commonly associated with genetic changes of the native species or genetic lineage that the invaders replace. Phenotypic shifts resulting from cryptic invasions are less commonly reported given the relative paucity of historical specimens that document such phenotypic changes. Here, I study such a case in two populations of threespine stickleback from central Europe, comparing contemporary patterns of gene flow with phenotypic changes between historical and contemporary population samples. I find gene flow from an invasive lineage to be associated with significant phenotypic changes, where the degree of phenotypic change corresponds with the level of gene flow that a population receives. These findings underline the utility of combining genetic approaches with phenotypic data to estimate the impact of gene flow in systems where anthropogenic alterations have removed former geographic barriers promoting cryptic invasions

Sometimes Sperm Whales (Physeter macrocephalus) Cannot Find Their Way Back to the High Seas: A Multidisciplinary Study on a Mass Stranding

BACKGROUND: Mass strandings of sperm whales (Physeter macrocephalus) remain peculiar and rather unexplained events, which rarely occur in the Mediterranean Sea. Solar cycles and related changes in the geomagnetic field, variations in water temperature and weather conditions, coast geographical features and human activities have been proposed as possible causes. In December 2009, a pod of seven male sperm whales stranded along the Adriatic coast of Southern Italy. This is the sixth instance from 1555 in this basin. METHODOLOGY/PRINCIPAL FINDINGS: Complete necropsies were performed on three whales whose bodies were in good condition, carrying out on sampled tissues histopathology, virology, bacteriology, parasitology, and screening of veins looking for gas emboli. Furthermore, samples for age determination, genetic studies, gastric content evaluation, stable isotopes and toxicology were taken from all the seven specimens. The animals were part of the same group and determined by genetic and photo-identification to be part of the Mediterranean population. Causes of death did not include biological agents, or the "gas and fat embolic syndrome", associated with direct sonar exposure. Environmental pollutant tissue concentrations were relatively high, in particular organochlorinated xenobiotics. Gastric content and morphologic tissue examinations showed a prolonged starvation, which likely caused, at its turn, the mobilization of lipophilic contaminants from the adipose tissue. Chemical compounds subsequently entered the blood circulation and may have impaired immune and nervous functions. CONCLUSIONS/SIGNIFICANCE: A multi-factorial cause underlying this sperm whales' mass stranding is proposed herein based upon the results of postmortem investigations as well as of the detailed analyses of the geographical and historical background. The seven sperm whales took the same "wrong way" into the Adriatic Sea, a potentially dangerous trap for Mediterranean sperm whales. Seismic surveys should be also regarded as potential co-factors, even if no evidence of direct impact has been detected

Interspecific Hybridization and Mitochondrial Introgression in Invasive Carcinus Shore Crabs

Interspecific hybridization plays an important role in facilitating adaptive evolutionary change. More specifically, recent studies have demonstrated that hybridization may dramatically influence the establishment, spread, and impact of invasive populations. In Japan, previous genetic evidence for the presence of two non-native congeners, the European green crab Carcinus maenas and the Mediterranean green crab C. aestuarii, has raised questions regarding the possibility of hybridization between these sister species. Here I present analysis based on both nuclear microsatellites and the mitochondrial cytochrome C oxidase subunit I (COI) gene which unambiguously argues for a hybrid origin of Japanese Carcinus. Despite the presence of mitochondrial lineages derived from both C. maenas and C. aestuarii, the Japanese population is panmictic at nuclear loci and has achieved cytonuclear equilibrium throughout the sampled range in Japan. Furthermore, analysis of admixture at nuclear loci indicates dramatic introgression of the C. maenas mitochondrial genome into a predominantly C. aestuarii nuclear background. These patterns, along with inferences drawn from the observational record, argue for a hybridization event pre-dating the arrival of Carcinus in Japan. The clarification of both invasion history and evolutionary history afforded by genetic analysis provides information that may be critically important to future studies aimed at assessing risks posed by invasive Carcinus populations to Japan and the surrounding region

Increase of organochlorines and mercury levels in common guillemots <i>Uria aalge</i> during winter in the southern North Sea

Beached seabirds, mainly common guillemots Uria aalge, were collected on the Belgian coast during winter from 1990 to 1995. Concentrations of total and organic mercury, and of organochlorines (PCBs and pesticides) were determined in muscle, liver and kidney. They were high compared to summer data (up to one order of magnitude), and increased during winter. This increase is not due to changes of total body weight nor polar lipid content, and thus reflects an actual increase of the seabirds' contamination while wintering in the southern North Sea. The observed annual cycle can be understood by assuming differences in prey contamination: higher during winter in the southern North Sea ecosystem than during summer in the Atlantic water ecosystem

Mercury and organochlorines in four sperm whales stranded on the Belgian coast, November 1994

Four sperm whales (three subadult males stranded on the Belgian coast, a fourth older male found dead at sea) were analysed for total mercury, methylmercury and organochlorines. All four were part of a total of 24 sperm whales that stranded on the North Sea coasts over a period of six months, a highly unusual phenomenon. Total mercury levels ranged from 0.5 µg/g fw in kidney and 1 in muscle, up to 15 in liver. The finding of at least 90% of the mercury in its inorganic form confirms the existence of detoxification mechanisms in the liver of cetaceans. PCB concentrations in muscle, liver, kidney and blubber ranged from 10 to 25 µg/g lipids. These results are in the same order of magnitude as literature data, which however does not imply that there is no impact on the populations. Social affiliation with a particular adult bull rather than a direct effect of pollutants may have been the primary cause of the stranding of the three younger animals: they apparently remained close to the older one (the leader?) dead at sea, and stranded in very shallow water. Indirect impact of anthropogenic pollutants influencing the behaviour and/or the health of a social cluster is one plausible hypothesis to explain why a large number of sperm whales got trapped in the North Sea, but limited data available on the large bull fail to support this

A cryptic invasion within an invasion and widespread introgression in the European water frog complex: consequences of uncontrolled commercial trade and weak international legislation

In Western Europe, many pond owners introduce amphibians for ornamental purposes. Although indigenous amphibians are legally protected in most European countries, retailers are circumventing national and international legislation by selling exotic nonprotected sibling species. We investigated to what extent non-native species of the European water frog complex (genus Pelophylax) have become established in Belgium, using morphological, mitochondrial and nuclear genetic markers. A survey of 87 sampling sites showed the presence of non-native water frogs at 47 locations, mostly Marsh frogs (Pelophylax ridibundus). Surprisingly, at least 19% of all these locations also harboured individuals with mitochondrial haplotypes characteristic of Anatolian water frogs (Pelophylax cf. bedriagae). Nuclear genotyping indicated widespread hybridization and introgression between P. ridibundus and P. cf. bedriagae. In addition, water frogs of Turkish origin obtained through a licensed retailer, also contained P. ridibundus and P. cf. bedriagae, with identical haplotypes to the wild Belgian populations. Although P. ridibundus might have invaded Belgium by natural range expansion from neighbouring countries, our results suggest that its invasion was at least partly enhanced by commercial trade, with origins as far as the Middle East. Also the invasion and rapid spread of Anatolian lineages, masked by their high morphological similarity to P. ridibundus, is likely the result of unregulated commercial trade. We expect that Anatolian frogs will further invade the exotic as well as the native range of P. ridibundus and other Pelophylax species elsewhere in Western and Central Europe, with risks of large-scale hybridization and introgression.status: publishe

Marine mammals from northeast atlantic: relationship between their trophic status as determined by d¹³C and d¹⁵N measurements and their trace metal concentrations

The relationship between trophic position through d13C and d15N and trace metal concentrations (Zn, Cd, Cu and Hg) was investigated in the tissues of six marine mammal species from the Northeast Atlantic: striped dolphin Stenella coeruleoalba, common dolphin, Delphinus Delphis, Atlantic white-sided dolphin Lagenorhynchus acutus, harbour porpoise Phocoena phocoena, white beaked-dolphin Lagenorhynchus albirostris, grey seal Halichoerus grypus stranded on French Channel and Irish coasts. White-beaked dolphins, harbour porpoises, white-sided dolphins, common and striped dolphins display the same relative and decreasing trophic position, as measured by d15N values, along both the Irish and French channel coasts, reflecting conservative trophic habits between these two places. Hepatic and renal Cd concentrations were significantly correlated to muscle d13C and d15N values while Hg, Zn and Cu did not. These results suggest that Cd accumulation is partly linked to the diet while other factors such as age or body condition might explain Hg, Zn or Cu variability in marine mammals. Combined stable isotope and trace metal analyses appear to be useful tools for the study of marine mammal ecology

Trace metals in the harbour porpoise from the North Sea and adjacent areas: relationship with stable isotope measurements, the nutritional status, lesions of the respiratory system and parasitism.

Growing concern has been raised about the status and the long-term viability of the harbour porpoise (Phocoena phocoena) in the North Sea and adjacent areas. Sources of trace metal variations were investigated using a multidisciplinary approach. Porpoises from the Belgian coasts were compared to individuals from the German North Sea and Baltic coasts, Denmark, Norway and Iceland. Toxicological results (Hg, Zn, Cu, Cd and Se) were confronted to most common pathological findings, namely emaciation, lesions of the respiratory system or parasitism. Influence of diet through stable carbon and nitrogen analysis (d13C and d15N), age and sex have also been considered. As expected, the nutritional status of stranded harbour porpoise from the Southern North Sea is poor compared to by-caught individuals from Norway and Iceland, as reflected by their blubber thickness, weight to length ratio and hepatic to total body mass ratio. The porpoises collected along the Southern North Sea coast display higher Zn and Hg concentrations compared to individuals collected in more preserved areas from the North Atlantic. Moreover, significant Zn, Hg and Se levels were observed with increasing emaciation severity. Porpoises displaying severe bronchopneumonia also have higher Zn concentrations probably due to the association previously described of emaciation and bronchopneumonia. Hg is clearly linked to parasitism. These increasing concentrations are not related to a shrinking of liver mass as it remains unchanged during the emaciation. As a result, hepatic trace metal load increases also. These observations tend to indicate a general redistribution of heavy metals within the organs (muscles to livers), which results from protein catabolism. Such a re-distribution could well be an additional stress for porpoises already experiencing stressful conditions (organochlorines, etc…). In contrast, Cu and Cd were never associated to emaciation. Other parameters such as age class or diet are more likely to be involved