Recent invasions by non-native gobiid fish species that are ongoing in the Western European rivers Rhine and Meuse, will lead to interactions with native benthic fish species. Since both non-native gobiids and native ...Recent invasions by non-native gobiid fish species that are ongoing in the Western European rivers Rhine and Meuse, will lead to interactions with native benthic fish species. Since both non-native gobiids and native benthic species are bottom dwelling species with a preference for shelter during at least part of their life cycle, it is likely that competition for shelter will occur between these non-native and native species when shelter is a limiting factor. To investigate the importance of this mecha- nism for species replacements, various habitat choice experiments were conducted between two common native benthic fish spe- cies （Cottus perifretum and Barbatula barbatula） and four invasive non-native gobiid species （Proterorhinus semilunaris, Neogo- bius melanostomus, N. kessleri and N. fluviatilis）. The first series of single specimen experiments determined the habitat choice of each individual fish species. In a second series of competition experiments, shifts in habitat choice in comparison with the previ- ously observed habitat choice, were determined when a native benthic fish species co-occurred with non-native gobiid species. Native C. perifretum displayed a significant shift in habitat choice in co-occurrence with the gobiids N. kessleri or P. semilunaris. C. perifretum was outcompeted and moved from the available shelter place to less preferred habitat types. During the competition experiments no change in habitat choice of B. barbatula was shown. Our study therefore suggests that competition for shelter is likely to occur in rivers invaded by N. kessleri and P. semilunaris at sites where shelter is limiting展开更多
It is often assumed that birds are able to choose a breeding territory that will later on have the most food for nestlings. Studies on this essential question are, however, few. We studied territory choice of a long-d...It is often assumed that birds are able to choose a breeding territory that will later on have the most food for nestlings. Studies on this essential question are, however, few. We studied territory choice of a long-distance migrant, the pied flycatcher Ficedula hypoleuca in southwestern Finland. In one study area, we monitored the territory choice of males via the order of territory settlement. Female territory choice was studied experimentally in another study area where the correlation between male and territory quality was removed by not allowing males a free choice of territory. We defined several habitat characteristics and es- timated the abundances of invertebrate prey from air, ground and trees with appropriate traps from the surroundings of the nest sites in both study areas. Against the expectation that parent birds would choose an arthropod-rich territory, neither males nor females seemed to choose those territories that later had the most food for nestlings. There was, however, some evidence that more eggs were laid in territories with more aphids and that more fledglings were produced in territories with high ant abundance. Our findings thus suggest that while it would be beneficial for birds to be able to choose food-rich territories, they may not be able to detect the right cues for doing so early in the breeding season. The possibility and importance of detecting the territories with the best prospects of rearing young may, however, vary among and within seasons and more studies on this topic are clearly needed [Current Zoology 61 （4）： 604-613, 2015].展开更多
文摘Recent invasions by non-native gobiid fish species that are ongoing in the Western European rivers Rhine and Meuse, will lead to interactions with native benthic fish species. Since both non-native gobiids and native benthic species are bottom dwelling species with a preference for shelter during at least part of their life cycle, it is likely that competition for shelter will occur between these non-native and native species when shelter is a limiting factor. To investigate the importance of this mecha- nism for species replacements, various habitat choice experiments were conducted between two common native benthic fish spe- cies （Cottus perifretum and Barbatula barbatula） and four invasive non-native gobiid species （Proterorhinus semilunaris, Neogo- bius melanostomus, N. kessleri and N. fluviatilis）. The first series of single specimen experiments determined the habitat choice of each individual fish species. In a second series of competition experiments, shifts in habitat choice in comparison with the previ- ously observed habitat choice, were determined when a native benthic fish species co-occurred with non-native gobiid species. Native C. perifretum displayed a significant shift in habitat choice in co-occurrence with the gobiids N. kessleri or P. semilunaris. C. perifretum was outcompeted and moved from the available shelter place to less preferred habitat types. During the competition experiments no change in habitat choice of B. barbatula was shown. Our study therefore suggests that competition for shelter is likely to occur in rivers invaded by N. kessleri and P. semilunaris at sites where shelter is limiting
文摘It is often assumed that birds are able to choose a breeding territory that will later on have the most food for nestlings. Studies on this essential question are, however, few. We studied territory choice of a long-distance migrant, the pied flycatcher Ficedula hypoleuca in southwestern Finland. In one study area, we monitored the territory choice of males via the order of territory settlement. Female territory choice was studied experimentally in another study area where the correlation between male and territory quality was removed by not allowing males a free choice of territory. We defined several habitat characteristics and es- timated the abundances of invertebrate prey from air, ground and trees with appropriate traps from the surroundings of the nest sites in both study areas. Against the expectation that parent birds would choose an arthropod-rich territory, neither males nor females seemed to choose those territories that later had the most food for nestlings. There was, however, some evidence that more eggs were laid in territories with more aphids and that more fledglings were produced in territories with high ant abundance. Our findings thus suggest that while it would be beneficial for birds to be able to choose food-rich territories, they may not be able to detect the right cues for doing so early in the breeding season. The possibility and importance of detecting the territories with the best prospects of rearing young may, however, vary among and within seasons and more studies on this topic are clearly needed [Current Zoology 61 （4）： 604-613, 2015].
