Danijel Ivajnšič

Low phenotypic variation in eastern common hamsters Cricetus cricetus

Abstract. We studied 468 museum specimens of the common hamster (387 skins and 204 skulls) collected in Belarus, Ukraine, Russia and Kazakhstan. Besides a standard tricolour type which prevailed, we identified six colour variants: stavropolicus with reduced white spots, and a bicolour entirely devoid of spots, white, piebald, dark-black (atypical melanistic) and intense dark (melanistic). The overall proportion of variant hamsters was estimated at 4.3 %. Colour variants were significantly more diverse and more frequent in Europe. The presence of melanistic hamsters was positively associated with high temperatures and high levels of precipitation. Cranial traits were largely invariant and the only significant trend was a slight increase in zygomatic width with longitude. We found no evidence of geographically contiguous clusters of populations which would be homogeneous enough or distinct from other similar clusters to be formally recognized as a distinct subspecies. The western segment of the common hamsters range (to the west of the Carpathian Mts.) is the most diverse genetically and morphologically while the populations to the east of the Carpathians are rather uniform. This homogeneity is further intensified on the eastern side of the Urals.

Habitat Changes Caused by Sea Level Rise, Driven by Climate Change in the Northern Adriatic Coastal Wetlands, Slovenia

The constantly increasing anthropogenic pressure on coastal habitats is additionally intensified by climate change effects. Sea level rise is a major threat to the two most important coastal wetlands in Slovenian seacoast, Secovlje Salina (Secoveljske soline) and Skocjan Inlet (Skocjanski zatok). Different methods from field vegetation mapping, field geodetic measurements, LIDAR scanning to spatial statistics were used to study effects of rising sea levels. They revealed that the spatial distribution of habitat types follows the micro-elevations. Therefore a habitat transition model could be developed for Secovlje Salina (Secoveljske soline) and Skocjan Inlet (Skocjanski zatok). Different scenarios of sea level rise where analysed. The prediction model demonstrated to which degree, how and where coastal habitats will shift to each other and decrease their surfaces in total.

Facts and misconceptions on the Palaearctic existence of the striped ground squirrel

Abstract The striped ground squirrel has a wide distribution in the Ethiopian region but is restricted to a small isolated area in Palaearctic Africa. This fragment was first recorded in the late 1940s in the Souss Valley (Morocco), however, not a single new observation has been published in the following decades. In September 2016 we surveyed the Souss Valley and found squirrels at 43 sites within the triangle between Agadir–Taroudant–Tiznit. Occupied sites were not distributed at random but occurred between an altitude of 45–254 m and on a substrate with coarse texture containing >65% sand. The vast majority of the sites with squirrels (69%) were classified as suburban, cultivated or both. Habitat suitability was estimated by applying geographically weighted logistic regression analysis. The influence of local predictor variables varied across the study area indicating the heterogeneous effects on the determination of the occurrence of the species. The modelled highly suitable habitat area for the striped ground squirrel in Morocco covers almost 690 km2 and only marginally overlaps the range for the species reported in the literature.

Relation between plant species diversity and landscape variables in Central-European dry grassland fragments and their successional derivates

Abstract A systematic field survey of an area of 843 ha in the traditional Central-European agricultural landscape of Goričko Nature Park in Slovenia revealed 80 fragments of dry semi-natural grasslands. Vascular plant species diversity was studied in relation to landscape variables and to threat (Slovenian red-listed species). Our results show that fragment size does not affect plant species diversity. In addition, fragment shape index is not related to Alpha diversity. Higher Alpha diversity was observed for abandoned grassland fragments. The lowest Alpha diversity was perceived on more mesic fragments, where habitat specialists are much scarcer. It was confirmed that the highest diversity of specialists are in the driest fragments, both still mowed and abandoned. With an increase in the number of distinctly different bordering habitat types, the total number of species per fragment generally does not increase, except in the case of those fragments that are already in different succession stages. Abandoned and typical dry grasslands are associated with a higher number of bordering habitats. Typical dry grassland fragments and abandoned ones, which probably derived mostly from drier (less productive) grasslands, are found on lower altitude and have a lower shape index. Habitat specialists Sedum sexangulare, Polygala vulgaris and Spiranthes spiralis have higher frequency in fragments with a lower shape index. This means that these oligotrophic specialists occur in smaller fragments. But Orchis morio has higher frequencies of occurrence on polygons with a higher shape index, which confirms the observation that this species occurs in larger and more irregular fragments, as well as close to houses and fields and along the roads.

Reproduction Biology of an Alien Invasive Plant: A Case of Drought-Tolerant Aster squamatus on the Northern Adriatic Seacoast, Slovenia

To understand changes in biodiversity, we must take into consideration at least the effects of global warming like increased droughts, the shift in plant phenology with the lengthened vegetation period, and the possibility that alien species might benefit from them. For better predictions whether non-native species could benefit from global change and turn into invasive alien species we chose to study Aster squamatus, alien that is already present in Slovenia and is currently regarded as non-invasive. We studied the species’ reproductive success and micro-scale habitat properties. Results show high reproductive potential of A. squamatus and it is necessary to constrain accumulation of seeds in the soil seed bank for future invasions. According to habitat properties, especially C:N ratio, we can regard A. squamatus as an engineering species, fertilising its own habitat. Climate change, prolonging the vegetation period, would enable more biomass accumulation followed by rapid decomposition. Released nutrients can be better used by fast-growing species that start their development slightly later in the season than early spring species, which begin to grow by utilising nutrients from their storage organs. In such cases of engineering alien species, adapted management is needed.

Spatio-temporal patterns along a primary succession on alluvial sediments

Dynamic alluvial landscapes offer many possibilities to study primary succession processes on newly developed habitats. However, within the Central European environmental conditions, where watercourses and their riparian spaces are under severe anthropogenic pressures — water regulation, deforestation, lowering of groundwater — natural processes are limited. We studied primary succession on alluvial stream deposits in an artificial lake, where we aimed to follow the terrestrialisation rate and habitat turnover, along with plant species richness and composition across successional stages. In 30 years, a pristine white-willow riparian forest developed. One half of the initially aquatic habitat became terrestrial. The frequency of change, studied on 11250 quadrats 10×10 m each (on a scale from “no change” to 8 changes) and the mean of change per habitat type (most of the habitats changed 2 to 3 times) revealed only one successional trajectory. The percentage flow chart showed a deterministic pathway of succession. The “time since formation” of a terrestrial habitat shows that more than 20% of the lake was terrestrialised within in the first ten years. We studied species richness and composition along three composed transects, following successional stages. We found that the newly assembled riparian white willow woodland has a surprisingly low colonisation rate of plant species.