Ecosystem engineers in the extreme: The modest impact of marmots on vegetation cover and plant nitrogen and phosphorus content in a cold, extremely arid mountain environment

Burrowing mammals strongly impact plant communities. One of the main effects is accelerating nutrient cycling and thus promoting plant growth. This mechanism is well-studied in grasslands and alpine habitats, but less is known about this phenomenon in arid, cold mountain environments. We studied ecosystem engineering by long-tailed marmots (Marmota caudata) by measuring the content of plant nitrogen and phosphorus, as well as nitrogen stable isotopes in plant biomass and marmot feces in a distance gradient up to 20 m from marmot burrows in an extremely arid glacier valley in Eastern Pamir, Tajikistan. We also captured aerial images of the area inhabited by marmots to study the spatial distribution of vegetation. There was a weak relationship between the presence of burrows and vegetation cover on soil not covered by burrow material. Burrow mounds were not colonized by plants, as opposed to other studies, where mounds are often microhabitats that enhance plant diversity. A significant increase in N and P in aboveground green plant biomass in the proximity of burrows was found in one out of six studied plant species. Contrary to our expectations, stable N isotopes did not give further insight into N routing. We assume that plant growth is strongly limited by water availability, which prevents them from utilizing the local increase in nutrients, certainly provided by marmot activity. The results are contrary to numerous studies, which showed that the role of burrowing animals as ecosystem engineers increases with increasing abiotic stress, including aridity. This shows a lack of this type of study at the end of the gradient of abiotic factors.

Does the American mink displace the European polecat? A need for more research on interspecific competition between invasive and native species

Introduced alien species can negatively affect native competitors by reducing their populations or eliminating them from ecosystems. However, studies do not always find evidence for anticipated impacts, and changes in native populations can be difficult to estimate. Interactions between the invasive American mink Neovison vison and native European polecat Mustela putorius have been studied in several countries, but the mink’s impact on polecat populations at a large spatiotemporal scale remains unclear. In the years 1995–2018, we live-trapped mink and polecats at 60 study sites in Poland, and we analysed hunting bags of mink and polecats from the years 2009–2018. During 13,766 trap-nights, we captured 905 individuals. Mink comprised 91.2% and polecats 8.8% of trapped animals. The mean mink and polecat trappability was 6 and 0.6 individuals per 100 trap-nights, respectively. At rivers, polecat and mink trappability were negatively correlated, whereas at lakes, they were not correlated. The sex ratio of trapped polecats was more skewed toward males than that of mink. Mink comprised 63.6% and polecats 36.4% of 59,831 animals killed by hunters. Over 10 years, the numbers of mink shot annually increased slightly, whereas the numbers of polecat decreased slightly. There was a positive correlation between numbers of mink and polecats shot annually. We found weak evidence that at a large spatiotemporal scale, the invasion of mink has led to a decline in polecat numbers. Although the datasets we analysed were based on large samples, they were insufficient to show evidence of competitive interactions between these two mustelids.

Performance of detection dogs and visual searches for scat detection and discrimination amongst related species with identical diets

Ecology often faces the problem that many threatened species are highly elusive but also conflict-laden. Thus, proper monitoring data are inevitable for their conservation and management. Indirect monitoring through scats is frequently used for such species, but scats of related species or species with similar diet are often visually indistinguishable. Since genetic methods for species identification are time-consuming and cost-intensive, a verification of the target species beforehand would be extremely beneficial in reducing effort to the analysis of the target species only. Such species discrimination could be provided through species-specific scat detection dogs. Therefore, we evaluated the reliability of species-specific scat detection dogs for two mustelid species feeding on identical diets: the Eurasian otter (Lutra lutra) and the American mink (Neovison vison), both of which are conflict-laden and increasing their populations and distribution ranges in central Europe. Their scats resemble each other in morphology and odour, exacerbating the differentiation even for experts. To evaluate whether detection dogs can reliably discriminate between related species feeding on similar diets and if their use would be beneficial, we tested their abilities against those of humans. We first proved that scat characteristics are not statistically different between species. Likewise, visual species identification through people with different experience levels was only partly successful. Experts showed higher average accuracy (0.89) than non-experts (0.72 and below), but detection dogs (4 dogs) were able to discriminate otter and mink scats under laboratory conditions with an accuracy of 0.95. Moreover, otter scat detection dogs found up to four times more scat samples in the field, were twice as fast as human searchers and found an almost equal number of scats with different characteristics, while humans mostly found older and larger scats placed on hotspots. We conclude that using detection dogs for species identity will allow subsequent laboratory analyses to be species-specific and avoid spending time and money on laboratory work of the wrong species. It also provides more precise and unbiased information about the target species.

Results of liver transplantation in the Department of General, Transplant and Liver Surgery at the Medical University of Warsaw in patients with chronic hepatitis B and C viruses infection

INTRODUCTION

Cirrhosis related to hepatitis C virus (HCV) and hepatitis B virus (HBV) infection is the most frequent indication for liver transplantation worldwide. Progress in prophylaxis of posttransplant HBV recurrence has led to major improvements in long-term outcomes of patients after liver transplantation. Conversely, impaired posttransplant survival of patients with HCV infection was reported in several studies, mainly due to recurrence of viral infection. The purpose of this study was to compare long-term results of liver transplantation between patients with HBV monoinfection, HCV monoinfection and HBV/HCV coinfection.

MATERIAL AND METHODS

A total of 1090 liver transplantations were performed in the Department of General, Transplant and Liver Surgery in cooperation with the Department of Immunology, Internal Medicine, and Transplantology at the Transplantation Institute Medical University of Warsaw between December 1994 and May 2012. After exclusion of patients with cirrhosis of non-viral etiology, patients with malignant tumors, and patients with acute liver failure, the final study cohort comprised 209 patients with HBV (HBV+/HCV- subgroup; n = 56) or HCV (HBV-/HCV+ subgroup; n = 119) monoinfection or HBV/HCV coinfection (HBV+/HCV+; n = 34). These subgroups of patients were compared in terms of long-term results of transplantations, defined by 5-year patient and 5-year graft survival estimates.

RESULTS

Overall and graft survival rates after 5-years for the whole study cohort were 74.5% and 72.6%, respectively. Five-year overall survival was 70.4% for patients within the HBV+/HCV- subgroup, 77.8% for patients within the HBV-/HCV+ subgroup, and 68.5% for patients within the HBV+/HCV+ subgroup. The corresponding rates of graft survival were 67.0%, 76.3%, and 68.5% for patients within the HBV+/HCV-, HBV-/ HCV+, and HBV+/HCV+ subgroups, respectively. Observed differences were non-significant, both in terms of overall (p = 0.472) and graft (p = 0.461) survival rates.

CONCLUSIONS

Both overall and graft survival rates after liver transplantations performed in the Department of General, Transplant and Liver Surgery in cooperation with the Department of Immunology, Internal Medicine, and Transplantology at the Transplantation Institute Medical University of Warsaw in patients with HBV and HCV infection are comparable to those reported by other European and American centers. In contrast to other studies, obtained results do not confirm the negative impact of HCV infection on long-term outcomes of patients.