Contribution of host species and pathogen clade to snake fungal disease hotspots in Europe.

Infectious diseases are influenced by interactions between host and pathogen, and the number of infected hosts is rarely homogenous across the landscape. Areas with elevated pathogen prevalence can maintain a high force of infection and may indicate areas with disease impacts on host populations. However, isolating the ecological processes that result in increases in infection prevalence and intensity remains a challenge. Here we elucidate the contribution of pathogen clade and host species in disease hotspots caused by Ophidiomyces ophidiicola, the pathogen responsible for snake fungal disease, in 21 species of snakes infected with multiple pathogen strains across 10 countries in Europe. We found isolated areas of disease hotspots in a landscape where infections were otherwise low. O. ophidiicola clade had important effects on transmission, and areas with multiple pathogen clades had higher host infection prevalence. Snake species further influenced infection, with most positive detections coming from species within the Natrix genus. Our results suggest that both host and pathogen identity are essential components contributing to increased pathogen prevalence.

Climatic conditions and prevalence of melanistic snakes-contrasting effects of warm springs and mild winters.

Climate change is one of the greatest challenges that wildlife is facing. Rapid shifts in climatic conditions may accelerate evolutionary changes in populations as a result of strong selective pressure. Most studies focus on the impact of climatic conditions on phenologies and annual cycles, whereas there are fewer reports of empirical support for climate-driven changes in the phenotypic variability of free-living populations. We investigated whether climatic variables explain the prevalence of colour polymorphism in a population of the grass snake (Natrix natrix) with two morphotypes, the melanistic and non-melanistic ones, in the period 1981-2013. We found that the prevalence of the black phenotype was negatively related to spring temperature and winter harshness, expressed as the number of snow days. According to the thermal melanism hypothesis, a high predation rate during warmer springs may override relaxed thermal benefits and vice versa, i.e. black individuals may perform better than typical ones when thermal conditions in spring are unfavourable. In turn, because they are smaller, melanistic individuals may be exposed to a higher risk of winter mortality, particularly during longer winters. We highlight the need for more studies on the effects of climatic conditions on temporal variation in melanism prevalence in other populations and species as well as in various geographic regions.

The influence of local environmental factors in southwestern Poland on the abundance of Ixodes ricinus and prevalence of infection with Borrelia burgdorferi s.l. and B. miyamotoi.

Ticks are important ectoparasites and vectors of pathogens that cause disease in humans and animals. The natural habitat of Ixodes ricinus ticks is forests, which are convenient habitats to search for hosts, including reservoir hosts, and therefore can be an important habitat source of tick-borne pathogens. The aim of the study was to assess the usefulness of detailed forest habitat-type maps to estimate the tick-borne risk at a local scale (Lower Silesia, SW Poland). For the purposes of estimating tick abundance, we used the land cover maps available from the Forest Data Bank. For I. ricinus collection, nine sites located in three forest habitat types were chosen: broadleaf forest, mixed broadleaf and coniferous forest and coniferous forest. Ticks were collected once a month from April to June 2018 and 2019 using the standard flagging method. At each of the nine sites, ticks were collected in four plots, of 100 m2 each. Tick abundance was analysed using general linear mixed models (GLMM). A total of 2196 (10.1/100 m2) ticks were collected, including 2093 Ixodes ricinus (95.3%; 9.6/100 m2), 46 Dermacentor reticulatus (2.1%; 0.2/100 m2) and 57 Haemaphysalis concinna (2.6%; 0.3/100 m2). Among the collected I. ricinus were 589 larvae (28.1%; 2.7/100 m2), 1261 nymphs (60.3%; 5.8/100 m2), 128 females (6.1%; 0.6/100 m2) and 115 males (5.5%; 0.5/100 m2). We found a highly significant effect of forest habitat type on the density of ticks for broadleaf forest (coefficient = 1.87267, p-value = 2.79e - 07). Additionally, a significant influence of air temperature and relative humidity on the abundance of ticks was observed. During spring, the peak activity of I. ricinus was recorded in May and June. For DNA amplification of Borrelia burgdorferi s.l., a nested PCR method was used. Out of 494 I. ricinus, 83 (16.8%) were positive for Borrelia spp. The RFLP method showed the occurrence of five species including four belonging to the B. burgdorferi s.l. complex: B. afzelii (30.1%), B. garinii (38.6%), B. valaisiana (2.4%) and B. lusitaniae (18.1%). Furthermore, B. miyamotoi (9.6%), a species belonging to bacteria that cause relapsing fever as well as co-infection of B. miyamotoi/B.lusitaniae (1.2%) were found. The differences in the infection level of Borrelia spp. between broadleaf forest and mixed broadleaf and coniferous forest were statistically significant.

Decline in body size and female fraction in the grass snake (Natrix natrix, Linnaeus 1758) population after 40 years (Southern Poland).

Depletion of free-living populations is often associated with changes in fitness-related traits, e.g., body size. Ongoing decrease in body size has been reported in most vertebrates, but reptiles remain understudied. Moreover, sexual size dimorphism, commonly observed in reptiles, indicates that environmental pressures on body size may appear sex-specific. This can also result in shifts in sex ratio, an aspect even less studied. We investigated body size and sex ratio in population of grass snake (Natrix natrix) surveyed over 40 years ago in comparison with the current state. We found that both sexes express similar magnitude in body size decline. The current sex ratio does not deviate from 1:1, while in the past, females outnumbered males. The observed changes are likely an outcome of several non-mutually exclusive factors. In the studied area, an increase in road traffic and human presence and a drop in prey availability have been documented. Both factors may exert higher pressure on larger individuals, particularly females, due to their high costs of reproduction. It is recorded here that increase in ambient temperatures and summer duration may additionally enhance the mortality risk and resource requirements. Shifts in body size and sex ratio can catalyze further declines in abundance and reproductive potential of the population.

The local-scale expansion of Dermacentor reticulatus ticks in Lower Silesia, SW Poland.

The range of D. reticulatus is discontinuous in Europe, with a gap between the Western and Eastern European populations. Recent studies have shown, however, a decrease in the gap as a consequence of D. reticulatus spreading to new areas. This study aims to analyze the dynamic of local-scale changes in the D. reticulatus range in Lower Silesia, SW Poland. All sites of D. reticulatus presence recognized in our research were located in the north-western part of the study area (Wroclaw and its surroundings), whereas the south-eastern part was found to be free of these ticks. However, a five-year observation period (2014-2019) indicates the expansion of D. reticulatus on a local scale, with a general tendency to expand to the east, with northerly or southerly deviations from year to year. The settled sites differed in distance to the nearest built-up area, the density of resident population, as well as land development intensity in the immediate vicinity. The 100% probability isolines of D. reticulatus presence in Wroclaw and its surroundings allowed the determination of the rate of range change, which turned out to be uneven in terms of direction and speed. The average rate of change in the range of tick occurrence was estimated at 7 km in 3 years. A more accurate analysis of the estimated range changes-made using modeling and verification of predicted changes in the field-showed that the likely rate of range change can be estimated at around 0.6-2.3 km/year.

Age-Dependent Utilization of Shelters and Habitat in Two Reptile Species with Contrasting Intraspecific Interactions.

Reptiles undergo worldwide decline driven mostly by habitat change. Detailed recognition of factors underlying spatial structure and habitat utilization is therefore a prerequisite of effective conservation of this group. While the body of data on spatial ecology of reptiles is rapidly growing, studies on social factors remain still underrepresented. We studied age-specific patterns of shelter use, range size, and habitat preferences in the context of intraspecific interactions in the smooth snake Coronella austriaca-known to exhibit intraspecific predation-and the limbless lizard slow worm Anguis fragilis-with no such behavior observed. Despite smaller availability of preferred microhabitats, juveniles of smooth snakes occupied habitat and shelters located at the edge of the population range that did not overlap with adults. No such pattern was observed in the slow worm. Our study indicates that intraspecific interactions affect the spatial ecology of squamates. Passive and active protection of habitat must include wide buffers to preserve the poorly detectable young fraction of the population.