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We determined genetic variance and gene flow across multiple scales (reaches, headwater segments, and catchments) to examine the dispersal ability of the flatworm Polycelis coronata along the Wasatch Mountains of Utah. Multiple models predict patterns of genetic differentiation in stream invertebrates based on dispersal traits and the spatial connectivity of the habitat. The stream hierarchy model predicts genetic differentiation to be low and gene flow to be high between reaches nested in segments, moderate among segments within catchments, and differentiation to be highest and gene flow lowest among catchments, whereas the headwater model predicts the greatest differentiation between headwater segments. Our objective was to determine which model best described genetic patterns observed in P. coronata. Using a nested hierarchical sampling design ensured that if limitations to dispersal had an effect on genetic differentiation, we would be able to identify at what scale these processes operate. We hypothesized genetic variation would be small within headwater segments and reach maximum levels between headwater segments with no increase in differentiation with increasing distance between headwater patches or between drainages. We do not expect high dispersal along the stream network or across the terrestrial environment (actively or passively).We generated DNA sequence data (mitochondrial COI) from 50 sites nested within 24 segments, which were nested in four adjacent catchments. We identified 134 haplotypes from 506 individuals using a 763 bp fragment of mtDNA. Genetic patterns did not conform to the SH model. Evidence from one drainage (Provo River) was consistent with the headwater model. However, high differentiation within sites suggested that the genetic patterns we uncovered may be representative of high ancestral polymorphism among pre-fragmented populations that were historically widespread. Large effective population sizes and no evidence of bottleneck events suggest incomplete lineage cannot be discounted as an explanation of high differentiation at the smallest scales.

This work focuses on food preferences of freshwater triclad Crenobia alpina and its position in spring food web. It explores the ability of C. alpina to capture living prey, considers ability of C. alpina and to survive feeding on several types of food. Furthermore it gives view on its occurence and ecological preferences in context of other spring species. One chapter is concerned with taxonomy, anatomy and ecology of Tricladida and C. alpina itself. Short term food-preference experiments show the ability of C. alpina to capture living Lumriculidae and larvae of Ephemeroptera. We don't confirm feeding of C. alpina on living Gammarus, although their occurence in our springs and ecological preferences are similar. C. alpina feeds significantly more on damaged prey without substantial afinity to any species. A year-long experiment on C. alpina in lab conditions finds that this flatworm is able to survive and even breed with nothing but filtred water. This fact connected with the observation of huge densities of flatworms in spring source, opens up a question whether C. alpina can be considered a real predator. Key words: Crenobia alpina, triclad flatworms, food preferences, spring

Flatworms, or planarian, have a high potential for regeneration and have been used as a model to investigate regeneration and stem cell biology for over a century. Chemicals, temperature, and seasonal factors can influence planarian regeneration. Caffeine and ethanol are two widely used drugs and their effect on flatworm regeneration was evaluated in this experiment. Non-toxic levels of caffeine, a stimulant, and ethanol, a depressant, were determined. The tails of the flatworms were removed and the regeneration stage was analyzed every 3 days for 15 days to see the effect of these drugs alone and in combination on regeneration. For day 3 and day 6, there was a significant difference between the ethanol treatment and the other treatments (positive control, caffeine treatment, and combined treatment). The ethanol treatment showed a delay in the initiation of regeneration but caught up to the other treatments by day 15.