BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.

The strength of a population resides in the resilience of its individuals and is closely related to the stability of its habitat. Stream macro-invertebrates are sensitive to environmental changes concerning habitat stability; thus, they require shelter to prevent drift during severe floods. We propose a novel approach to estimate the impact of flash floods upon the substrate, by introducing a variable named 'flash-flood potential' (FFP), which accounts for the site slope and the average slope of the upstream catchment. We investigate the impact of this variable on the distribution of two important crayfish species, Austropotamobius torrentium and Astacus astacus, in Romania. We focus on the connection between crayfish abundance and FFP, and also on the role of the individuals' body size in shelter allocation, considering shelter stability as a key factor in coping with the disturbances. The results show that both species are sensitive to influence of the FFP, A. torrentium apparently having a slight advantage. The size of populations visibly decreased with the increase of FFP, those in the upper range having few individuals, which were mainly found in very stable shelters. Individual analyses reveal that the most durable shelters were generally occupied by the largest crayfish. We hypothesize that the competition for shelter is an indirect driver for preventing the drift of crayfish populations.

No abstract

The long-term survival of a species requires, among other things, gene flow between populations. Approaches for the evaluation of fragmentation in the frame of freshwater habitats consider only a small amount of the information that combined demography and geography are currently able to provide. This study addresses two species of Austropotamobius crayfish in the light of population genetics, spatial ecology and protected areas of the Carpathians. Advancing the classical approaches, we defined ecological distances upon the rasterised river network as a surrogate of habitat resistance to migration, quantifying the deviations from the species´ suitability range for a set of relevant geospatial variables in each cell of the network. Molecular analyses revealed the populations of the two Austropotamobius crayfish species are clearly distinct, lacking hybridisation. Comparing pairs of populations, we found, in some cases, a strong disagreement regarding genetic and ecological distances, potentially due to human-mediated translocations or the geophysical phenomena of regressive erosion, which may have led to unexpected colonisation routes. Protected areas were found to offer appropriate local habitat conditions but failed to ensure connectivity. The methodology applied in this study allowed us to quantify the contribution of each geospatial (environmental) variable to the overall effect of fragmentation, and we found that water quality was the most important variable. A multilevel approach proved to reveal a better understanding of drivers behind the distribution patterns, which can lead to more adequate conservation measures.

Caddisflies are often used in studies on freshwater ecosystem ecology because of their aquatic-dependent larvae. The present study addresses the ecological affinities of larvae of Hydropsyche incognita in terms of the pattern of distribution of this species in the Romanian Carpathians using a boosted regression trees (BRT) model. A population cluster located in the western Romanian Carpathians was identified by the spatial analysis. The statistical model revealed that this species prefers a neutral to low-alkaline pH, high levels of dissolved oxygen, low conductivity, fast flowing water, moderate sized rivers at an altitude below 600 m a.s.l. and low concentrations of organic pollutants. An eastward decrease in the frequency of H. incognita populations was recorded along rivers in the Carpathians. The predictions derived from the BRT model on sites outside the population cluster suggest that many locations in the central and eastern Romanian Carpathians are suitable for H. incognita. However, this species was found at only a few of these locations. In contrast, some populations in this area were found in habitats predicted as unsuitable. There are several possible explanations of this, one of which is random dispersion of the species by flying adults.