Jitka Horáčková

Mollusc succession of a prehistoric settlement area during the Holocene: A case study of the České středohoří Mountains (Czech Republic)

Some Central European areas were attractive for the first agricultural settlements due to their suitable natural conditions. The Holocene development of such areas was thus under long-term human pressure, whose impact on the whole landscape is still poorly understood. One of such areas is the České středohoří Mountains. While pollen analyses can provide the general pattern of the landscape development, the analyses of mollusc succession provide landscape details, which are important primarily in landscapes with high habitat diversity. Based on the study of 11 mollusc successions situated at the České středohoří Mountains, we describe the postglacial development of the area and show the moderate fluctuation of woodland, wetland and open country habitats without any distinct succession peaks of particular habitat types during the whole Holocene. However, a detailed look of species exchange has provided additional information of succession pattern. The impoverishment of woodland communities is probably caused by human pressure, not natural processes, because fully developed woodland assemblages had occurred there during the past interglacials. It seems for now that humans had affected the whole landscape of the prehistoric settlement area, including hard-to-access sites, not only the nearby surroundings of their settlement.

Invasiveness Does Not Predict Impact: Response of Native Land Snail Communities to Plant Invasions in Riparian Habitats

Studies of plant invasions rarely address impacts on molluscs. By comparing pairs of invaded and corresponding uninvaded plots in 96 sites in floodplain forests, we examined effects of four invasive alien plants (Impatiens glandulifera, Fallopia japonica, F. sachalinensis, and F.×bohemica) in the Czech Republic on communities of land snails. The richness and abundance of living land snail species were recorded separately for all species, rare species listed on the national Red List, and small species with shell size below 5 mm. The significant impacts ranged from 16–48% reduction in snail species numbers, and 29–90% reduction in abundance. Small species were especially prone to reduction in species richness by all four invasive plant taxa. Rare snails were also negatively impacted by all plant invaders, both in terms of species richness or abundance. Overall, the impacts on snails were invader-specific, differing among plant taxa. The strong effect of I. glandulifera could be related to the post-invasion decrease in abundance of tall nitrophilous native plant species that are a nutrient-rich food source for snails in riparian habitats. Fallopia sachalinensis had the strongest negative impact of the three knotweeds, which reflects differences in their canopy structure, microhabitat humidity and litter decomposition. The ranking of Fallopia taxa according to the strength of impacts on snail communities differs from ranking by their invasiveness, known from previous studies. This indicates that invasiveness does not simply translate to impacts of invasion and needs to be borne in mind by conservation and management authorities.

River Floodplains as Habitat and Bio-Corridors for Distribution of Land Snails: Their Past and Present

Abstract River floodplains of Czech rivers serve as refugia to woodland or hydrophilous gastropods, in current intensively agriculturally utilised, urbanised and largely fragmented landscape. This habitat often form one of the last refuge and replace the natural habitat of these species. River floodplains also represent linear bio-corridors in landscape and allow gastropods to spread through the landscape in both directions, up and down the stream. We showed based on available fossil mollusc successions that development of the floodplain mollusc fauna took place quite different way in various river floodplains, depending on their specifics and geographical location, because especially the ones situated in the chernozem area of the Czech Republic had very different history in comparison with those in higher altitudes. The species richness and composition of recent floodplain malacofauna arises from historical development of particular area/site and depends also on environmental factors such as an elevation, humidity gradient, vegetation type and its biomass, light conditions of the site and soil reaction. Recently, the invasive plants represent a serious problem for current floodplain ecosystems; species richness and abundances of terrestrial mollusc floodplain assemblages are changing due to their effect. The impact on gastropods is species-specific and was described for the following species: Impatiens glandulifera, Fallopia japonica subsp. japonica, F. sachalinensis, F. ×bohemica.

Early postglacial recolonisation, refugial dynamics and the origin of a major biodiversity hotspot. A case study from the Malá Fatra mountains, Western Carpathians, Slovakia

While general trends in Central European postglacial recolonisation dynamics are relatively well known, we often lack studies on intermediate (meta-population, landscape) scales. Such studies are needed to increase our understanding of, for example, the location of refugia; emergence of endemism, rates and trajectories of postglacial migrations; and anthropogenic landscape changes. Here, we focused on the outer Western Carpathian mountain chain Malá Fatra, which is currently characterised by high biodiversity and endemism and is thus considered a likely refugium of the Last Glacial period for the temperate biota of Eastern–Central Europe. We used molluscs and vascular plants as reference taxonomic groups and supported palaeoenvironmental interpretations of their (sub)fossil assemblages using high-resolution geochemical data. Generally, postglacial biotic successions from the study region fit the standard developmental pattern well in Middle and Eastern European uplands. Nevertheless, we found important biogeographically based peculiarities. In total, more than 50 species per (sub)fossil community at the reference site Valča, including 30 woodland species and 11 Carpathian endemites, make site of the highest known Holocene mollusc species diversity in Europe. Our palaeoecological analysis of this long-term biodiversity hotspot suggests that the Western Carpathians were likely an important source of the postglacial recolonisation of Central Europe by forest biota and, at the same time, an area of refugium-based endemism.