European Minnow Phoxinus Research Articles

The role of geography and ecology in shaping repeated patterns of morphological and genetic differentiation between European minnows (Phoxinus phoxinus) from the Pyrenees and the Alps

Neutral and selective processes c an drive repeated patterns of evolu tion in dif ferent groups of populationsexp eriencing similar ecol ogica l gradients. In this paper, we used a combinat ion of nucl ear and mitochondrialDNA markers, as well as geometric morphometrics, to investigate repeated patterns of morphological andgenetic divergence of E uropean minnows in two mountain ranges : the Pyrenees and the Al ps. Europeanminnows (Phoxinus phoxinus) are cyprinid fish i nha bitin g most freshwater bodies in Europe, including those indifferent mountain r anges that could act as major geographical barriers to gene flow. We explored patterns ofP. phoxinus phenotypic and genetic di versi fication along a gradi ent of alti tude common to the two mountainranges, and tested for isolation by distance (IBD), isolation by environment (IBE) and isolation by adaptation(IBA). The results indicated that populations from the Pyr enees a nd the Alps bel ong to two well differentiated,reciprocally monophyletic mt DNA lineages. Substantial genetic differentiation due to geographical isolationwithin and between populations from the Pyrenees and the Alps was also found using rapidly evolving AFLPsmarkers (isolation by distance or IBD), as well as morphological differences between mountain ranges. Als o,morphology varied strong ly with elevation and so did genetic differentiation to a lower extent. Despitemoderate evidence for IBE and IBA, and therefore of repeated evolution, substantial population heterogeneitywas found at the genetic level, suggesting that selection and population specific genetic drift act in concert toaffect genetic divergence.

Infection ecology of Philometra ovata (Nematoda: Philometridae) in a wild European minnow (Phoxinus phoxinus) population in Finland.

Seasonal life cycle of body cavity dwelling (BCD) Philometra ovata (Nematoda: Philometridae) has been reported in southern and central European countries, but its swim bladder dwelling (SBD) stage and northern populations have remained unstudied. In this study, we investigated the seasonal life cycle and infection ecology of P. ovata in both swim bladder and body cavity in the European minnow (Phoxinus phoxinus) in Finland. The larval P. ovata infected the swim bladder of minnows mainly in August. Female SBD P. ovata emigrated to body cavity mostly in September, grew to their full size by the end of the next June, and evacuated from minnows in July. In addition, female SBD P. ovata retarding their development and staying in swim bladder were found commonly in minnows, thus the mean monthly prevalence (6·7±3·9%) and mean intensity (1·4±0·8) of BCD P. ovata was lower than that of SBD P. ovata (37·8±15·1% and 2·0±1·5, respectively). Finally, despite the large size of BCD individuals, infection of P. ovata did not impair body condition and relative gonad size of minnows, but increased the mortality and caused physical damages in their hosts during the evacuation period.

The Norwegian reference lake ecosystem, Øvre Heimdalsvatn

The subalpine lake, Ovre Heimdalsvatn and its catchment, situated in the mountains of southern Norway, has been the subject of extensive ecosystem studies over the last 50 years covering a wide range of disciplines. The lake is located at 1,088 m a.s.l., has an area of 0.78 km2, a maximum depth of 13 m, and a catchment area of 23.6 km2. It lies more or less on the limit of the birch forest, while the catchment extends up over 1,800 m a.s.l. and into the high alpine zone. The valley is little influenced by human activity and there is no permanent habitation, although the area is used for grazing of domestic livestock during summer. Otherwise the lake and its catchment have always been important for fish and game. The catchment also received major radionuclide fallout from the Chernobyl accident in 1986. The studies include Quaternary history, the development of algorithms for remote sensing of snow conditions, long-term changes in lake ice cover and temperature, the zooplankton and benthic communities, as well as the uptake of Chernobyl radionuclides and mercury by the biota. The consequences of the introduction of the European minnow (Phoxinus phoxinus) on the benthos, zooplankton and the brown trout (Salmo trutta) have also been investigated. The lake and its catchment are widely used in university teaching and thesis work. On account of the substantial knowledge base, Ovre Heimdalsvatn is well suited to long-term monitoring.

Fish distribution in a mountain area in south-eastern Norway: human introductions overrule natural immigration

The aim of this study is to examine the impact of man’s interventions on the present day distribution of fish in a mountain area in southern Norway, the Atna river system. River Atna originates in the Rondane mountains at altitudes of nearly 1600 m a.s.l., and joins River Glomma at 300 m a.s.l. There are 98 lakes in the watercourse (701–1565 m a.s.l.). Lake Atnsjoen is the largest lake (5.0 km2). Data on the occurrence, origin and status of fish in lakes were obtained by means of interviews, questionnaires and written sources. Occurrence in rivers and streams was surveyed by electrofishing. While the lower reaches of River Glomma contain most of the freshwater fish species found in Norway, the Atna watercourse has a poor fish fauna. Physical conditions, e.g. steep river gradients and several impassable waterfalls have prevented fish from reaching most lakes and river stretches after the deglaciation some 6000 years ago. Five species of fish are regarded as native to the area; brown trout (Salmo trutta), Arctic charr (Salvelinus alpinus), grayling (Thymallus thymallus), Siberian sculpin (Cottus poecilopus) and European minnow (Phoxinus phoxinus). Although only native species are found in the area, the present distribution of these species within the watercourse is to a very large extent a result of human interventions during the past 100–130 years. Brown trout were originally found in the main branch of the river, including Lake Atnsjoen and a few small lakes (n<5) further upstream, but it is now found in 65 lakes. Arctic charr were native only to Lake Atnsjoen, but now inhabit 20 lakes. Grayling remains restricted to River Atna below the waterfall at the outlet of Lake Atnsjoen. The natural distribution of Siberian sculpin is restricted to the main river below Liafossen waterfall (14 km above Lake Atnsjoen). During the 1890s, this species was accidentally introduced to Lake Setningsjoen, and subsequently spread to another three lakes further upstream. The European minnow was native only to the River Atna below Lake Atnsjoen, but was accidentally introduced to seven lakes in the course of this century. There are 24 fishless lakes in the watershed, mainly mountain lakes between 1033 and 1587 m a.s.l.

Status of Zoobenthos and Fish Populations in Subarctic Rivers of the Northernmost Finland: Possible Effects of Acid Emissions from Russian Kola Peninsula

In 1990, a monitoring programme was initiated to survey the status of benthic invertebrate communities and fish populations over a wide range of subarctic rivers in northernmost Finnish Lapland (68°15′–70°N). A special emphasis was placed on detecting possible effects of acidification through sulfur emissions from Russian Kola Peninsula. Sampling in 13 rivers within four major river systems covered watercourses from small brooks to large 7th order rivers, and watersheds with different distances from the emission sources. The community structure of zoobenthos and the occurrence of acid-sensitive indicator species were assessed in 90 sampling sites. Sensitive fluvial fish species, including Atlantic salmon (Salmo salar), brown trout (Salmo trutta), European minnow (Phoxinus phoxinus) and burbot (Lota lota), were monitored by studying their occurrence, abundance and juvenile recruitment. No signs of acid-induced failure in juvenile recruitment were detected in salmonid populations. The occurrence of minnow and burbot covered all the systems studied. In parallell, the structure of benthic communities with relatively high species diversity and wide distribution of a highly acid-sensitive caddisfly indicated no effects of acidification.

The Effect of Group Size on Relative Competitive Ability

Recent influential models of the distribution of foraging animals have recognised the importance of individual variation in competitive ability, but have assumed that this property is intrinsic to the individual. However, Tregenza et al. suggested that in continuous input situations (where resources are supplied at a steady rate and utilised immediately) the relative competitive ability of an individual may be affected by competitor density. We therefore examined the effect of group size (which was equivalent to competitor density) on relative competitive abilities within a shoal of European minnows (Phoxinus phoxinus) exploiting a single, continuous-input food patch. In partial agreement with Tregenza et al. and in contrast to Sutherland and Parker's 'Phenotype scales intercept' model of the ideal free distribution (IFD) with competitive asymmetries, we found two processes which act in opposite directions. These effects can cancel each other out to give the misleading idea that there is no effect of group size upon relative competitive ability. These effects were dependent upon the difference in body size between the two fish in a pair, but this difference itself had no direct effect on relative competitive ability. The reasons for the differences between our results and those of Tregenza et al. are discussed.