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Potravní chování nepůvodních druhů hlaváčovitých ryb
GEBAUER, Radek
Global homogenisation of biota is observed at an ever-increasing rate, causing environmental and economic losses as well as emerging health risks. Ecological and economic consequences of biological invasions fuel the need for an urgent targeted and cost-effective management given the amount of invaders, vectors and pathways. We examined the effects of environmental and human-related factors on distribution of alien animal species richness in the Czech Republic (Central Europe). We compiled a set of maps showing the level of invasion of six categories of alien animal species in each of 628 grid cells (ca. 12.0 × 11.1 km) covering the Czech Republic. Relationships between alien species richness and 12 variables characterizing climatic conditions, topography, land cover, and human population size were calculated using the generalized least squares method. Species richness of all aliens, of invertebrates, and of terrestrial species showed the strongest positive relationship with mean annual temperature, while the number of black and grey (proposed prominent invaders) and aquatic species was most closely related to the presence of large rivers. Alien vertebrates showed a strong negative relationship with annual precipitation. The highest alien animal species richness was found in and near large population centres and in agricultural landscapes in warm and dry lowlands. The gateways for alien aquatic species are rather large rivers over sport fishing and aquaculture import. Two benthic fish species, round goby Neogobius melanostomus and western tubenose goby Proterorhinus semilunaris have recently expanded beyond their native ranges. Both species exert a detrimental effect on fish communities' structure directly via predation on fish eggs and indirectly via alterations of food webs. We quantified and compared the foraging behavior and efficiency of invasive N. melanostomus and alien P. semilunaris upon common carp Cyprinus carpio larvae at two temperature levels (20 and 25 °C) and in three different habitat structures (sand, cobbles, cobbles with artificial plant) using the functional response approach. Both alien predators showed type II FR in all temperature and habitat treatments. Intra-specific comparison showed no significant temperature dependency on assessed FR parameters, attack rate and handling time, suggesting broad temperature tolerance of both tested predators. The handling time did not differ between predators suggesting similar per capita ecological impact at high prey densities. Proterorhinus semilunaris showed a lower maximum feeding rate at 25 °C compared to the rest of treatments suggesting a lower temperature optima compared to N. melanostomus. Interspecific comparison showed similar values of handling time in cobble substrate and cobbles with artificial plant suggesting similar per capita ecological impacts of both aliens. Intraspecific comparison showed significantly lower values of handling time in both predators in habitat with cobbles reflecting higher maximum feeding rate. Therefore, impact of both invaders in such environment could elevate. Neogobius melanostomus showed higher attack rate in sandy habitat compared to P. semilunaris, while no significant differences were observed in other habitat treatments.
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