A PRELIMINARY TAXONOMIC REVISION OF THE BRITISH WHITEFISH WITH ESPECIAL REFERENCE TO THE GWYNIAD OF LLYN TEGID (BALA)

The paper deals with a biometrical analysis of forty-one specimens of the Gwyniad, Coregonus clupeoides pennantii (Cuv. et Val.) of Bala Lake, (Llyn Tegid) North Wales. Tho Gwyniad shows the greatest relationship to the continental coregonids Coregonus lavaretus . It is proposed that the taxonomy of the British whitefishes be revised and that the Gwyniad be classified as Coregonus lavaretus pennantii (Cuv. et Val.). Similarly, it is proposed that the Powan of Loch Lomond be classified as Coregonus lavaretus clupeoides Lacépède. The classification of the Schelly from the English Lake District needs further investigation.     

Evidence for independent origin of two spring‐spawning ciscoes (Salmoniformes: Coregonidae) in Germany

Combined analyses of mitochondrial DNA (mtDNA) and microsatellite loci were performed to assess the genetic differentiation of two spring‐spawning ciscoes from each other and from sympatric Coregonus albula in two German lakes. Polymorphism was screened at six microsatellite loci and mtDNA for a total of 247 and 94 ciscoes, respectively. Microsatellite data showed a weak differentiation between spring‐spawning Coregonus fontanae and sympatric C. albula in Lake Stechlin ( F _ST = 0–0·008), whereas a significant differentiation was observed between spring‐spawning Coregonus lucinensis and sympatric C. albula in Lake Breiter Luzin ( F _ST = 0·013–0·039). A more pronounced genetic difference was observed between both spring‐spawning species ( F _ST = 0·05–0·128). Shared mtDNA haplotypes among sympatric species within both Lake Stechlin and Lake Breiter Luzin were observed, whereas no haplotype was shared between C. fontanae and C. lucinensis . These results suggest an independent origin for spring‐spawning ciscoes in each lake. Evidence is also provided for mtDNA introgression of Coregonus sardinella into C. lucinensis and C. albula in Lake Breiter Luzin. Postglacially, this species or at least a population which showed mtDNA introgression has colonized the Baltic Sea basin up to the glacial margin that was located between Lakes Stechlin and Breiter Luzin.     

Confirmation of the presence of schelly, Coregonus lavaretus, in Brotherswater, U.K.

The presence of the nationally-rare schelly. Coregonus lavaretus , in Brotherswater, a small lake in the English Lake District, was confirmed in the summer of 1992. However, pronounced deepwater oxygen depletion may pose a threat to the continued survival of this seventh U.K. population.     

Chemistry of sediments from two linked lakes in North Wales

SUMMARY. Cores of sediment from Llyn Peris and Llyn Padarn, two linked lakes in North Wales, are described. Dating of sediments by ¹⁴C techniques, investigations of remanent geomagnetism and estimates of recent deposition rates from measurements of ¹³⁷Cs, indicate that in Padarn an unbroken record of the last 7000 years has been obtained. In Peris, the upper lake, the rate of sediment accumulation is greater than in Padarn and the sediment has been considerably disturbed. Sediment chemistry is related to the climatic and industrial history of the area. Some features of the chemical profiles in Padarn are similar to those of lakes in the English Lake District, and there is evidence to suggest that erosion has increased in the catchment since c . 3500 years ago. This is more recent than similar increases in erosion reported for the English Lake District. In Peris, industrial activity during the past few hundred years has resulted in high levels of copper and calcium in the surface regions of sediment profiles.     

Systematics of the Irish pollan (Coregonus pollan Thompson): an electrophoretic comparison with other Holarctic Coregoninae

Evidence is presented on the genetic relationships of 35 coregonine populations from Alaska, Britain, Ireland, Finland and Sweden. This evidence is derived from an electrophoretic analysis of 27 enzyme loci and additional 'general protein loci'. The Irish pollan C. pollan and the Alaskan C. autumnalis gave identical electrophoretic patterns for all proteins suggesting that they are conspecific and separated only since the last glaciation. C. peled, C. albula and the ' C. lavaretus' complex gave unique patterns for a number of proteins. The F_n C. oxyrhynchus X C albula hybrids, from a lake where no other coregonines occur gave a unique pattern for the enzyme phosphoglucose isomerase but all other enzymes were electrophoretically identical to the C. oxyrhynchus parent and the mean gill raker number was closer to this species than in the F₁ hybrid.     

Studies on grayling, Thymallus thymallus L., in Llyn Tegid and the upper River Dee, North Wales.

Scale and length/weight data from 2071 Llyn Tegid grayling and 1803 River Dee grayling were used for age and growth determinations. The time of scale annulus formation varied from autumn in some years to spring in other years. Seasonal changes in length, weight and the condition factor were described. The main growth period was from spring to autumn with very little growth occurring during the winter. Annual growth in length was back-calculated from scale measurements, and von Bertalanffy's model was fitted to the resulting length for age data. Comparisons were made between the specific growth rates and ultimate lengths ( L_x ) of Llyn Tegid and River Dee grayling, and between the growth of male and female grayling. Males grew faster than females after the onset of sexual maturity. Calculated lengths were converted to weights using a combined length/weight relationship for Llyn Tegid and River Dec grayling. Changes were evident in this relationship throughout the life of the fish.     

Is coexistence mediated by microhabitat segregation? An in-depth exploration of a fish invasion

Vendace Coregonus albula has invaded the subarctic Pasvik hydrosystem, northern Norway and Russia, after being translocated from its native Finnish range into Lake Inari (Finland), upstream of Pasvik. The development of the invader and the effects on two native lake communities in the upstream and downstream part of the hydrosystem, respectively, have been monitored since 1991. In the upstream lake location, the invader relegated the native whitefish Coregonus lavaretus from the pelagic habitat within a few years. An expected similar development in the downstream location was, however, not observed. Data are presented on the diet and microhabitat use (vertical pelagic zone) for three types of replicated situation: (1) the invader v. the native species, (2) upstream v . downstream lakes and (3) early and late invasion stages, to explore the outcome of the competitive interactions. The use of different microhabitats available within the deeper pelagic zone in the downstream location was observed to have delayed the negative effects on native whitefish, possibly enabling a persistent coexistence between the two species in the pelagic zone of this lake.     

Genetic changes in a vendace Covegonus albula (L.) population, 92 years after introduction

The Osensjmn vendace, Coregonus albula (L.), population was founded in 1895 by introduction of about 90 000 fry from Lake Mjøsa. After 92 years, or about 46 generations of isolation, remarkable genetic changes were evident among the transplants compared to their source population. Electrophoresis of 33 enzyme loci revealed that allele frequencies differed significantly in eight of the 10 polymorphic loci. Nei's unbiased genetic distance was D = 0.012, representing the level of population differentiation usually observed among distant watercourses in vendace. Genetic variability was clearly higher among the transplants: average observed heterozygosity was 14.8% compared with 11.2% among Lake Mjøsa vendace. The high genetic variation among Osensjoen vendace shows that the divergence is not due to a small number of founders or bottlenecks in later generations. Selection by the contrasting environmental conditions between the habitats of the donor and transplanted populations is the most plausible hypothesis to explain the genetic changes in the Osensjsen vendace.     

Mitochondrial DNA analysis distinguishes between British populations of the whitefish

The whitefish Coregonus lavaretus is confined to two Scottish lochs and four English and one Welsh lake in the British Isles. Restriction fragment length polymorphisms (RFLPs) in the mitochondrial (mt) DNA have been used to analyse variability within and between populations. The 14 restriction enzymes employed in this study examined approximately 3% of the mt genome and revealed 15 haplotypes among 156 fish. Haplotype diversity within populations was generally low except for the Welsh population where nine haplotypes were found among 30 fish examined. The haplotypes clustered into three distinct groups corresponding to Scottish, English and Welsh populations. No haplotypes were shared among the three groups. Possible alternative explanations for these findings are introgression from another species, stochastic lineage sorting from a polymorphic ancestral gene pool and/or separate colonizations following the last glaciation.     

Eighteen new tetranucleotide microsatellite DNA markers for Coregonus lavaretus cloned from an alpine lake population

We developed 18 polymorphic microsatellite markers for Coregonus lavaretus from genomic libraries enriched for (GACA)(n) and (GATA)(n) repeat sequences. Emphasis was placed on developing highly polymorphic, perfect repeats. These loci were screened in 69 individuals from two alpine populations in Austria. Allelic variation was high with nine to 37 alleles per locus and expected heterozygosities ranging from 0.37 to 0.95. The high level of polymorphism revealed by these loci will be relevant for population studies in context to the evolutionary history of this species.     

The effect of natural selection on estimates of genetic divergence among populations of the Atlantic salmon

The effect of natural selection on the _mMEP-2 * locus on measures of genetic divergence among Atlantic salmon populations was investigated by examining the pattern of change in the level of genetic differentiation (F_ST) averaged over loci when data on the _mMEP-2 * locus were either included or excluded. The level of F_ST among populations at various geographic scales was estimated from allele frequencies at up to four loci (_s AAT-4 *, IDDH-1 *, IDHP-3 *, and _mMEP-2 *). At smaller geographic scales (within river systems or limited geographic regions) levels of variance in _mMEP-2 * allele frequencies were reduced relative to mean levels. At larger geographic scales (across continents or the species range) variation in _mMEP-2 * allele frequencies was greater than mean levels. These results suggest an a priori hypothesis for the effect of selection on the _mMEP-2 * locus which may be applied in future studies on variation in protein coding or other (e.g. mini- and microsatellite) loci in the Atlantic salmon. It is recommended that estimates of gene flow among populations of the Atlantic salmon based on mean F _ST estimates which include data on the _mMEP-2 * locus should be viewed with caution.     

Primary production studies in two linked but contrasting Welsh lakes

SUMMARY. Llyn Padarn and Llyn Peris have distinct phytoplankton populations. During 1975–76, the standing crop measured as chlorophyll- a was 5.5 times greater in Padarn than in Peris and the production rate, determined by the ¹⁴CO₂ method, was faster by 3.4 times. These differences were attributed to the higher concentrations of phosphorus in the lower lake caused by treated sewage effluent. Incident light intensity, which was slightly lower in Peris due to mountain shading, and temperature, which was 1–4°C higher in Padarn, made little significant contribution to these differences during the summer. The reduced transparency of Padarn water, compared with that of Peris, resulted from denser phytopiankton crops in Padarn. During the summer, Padarn exhibited carbon dioxide depletion which correlated with the chlorophyll concentration. Light inhibition at the surfaces of both lakes correlated with solar radiation intensity. However, the relationship between pigment content and maximum photosynthetic rate was poor. Extracellular products accounted for about 16% of the total production in the lakes. Uptake of ¹⁴C-labelled acetate was low compared with that of ¹⁴CO₂ uptake.     

Some observations on the food of the gwyniad Coregonus clupeoides pennantii Valenciennes of Llyn Tegid (Lake Bala), North Wales

The seasonal variations in the diet of adult gwyniad Coregonus clupeoides pennantii=C. lavaretus from Llyn Tegid, North Wales were studied. Stomachs were examined to determine fullness, volume and identity of contents.
A clear seasonal cycle in food intake was found. Feeding rates were low from January to April but increased during the summer (May-June) and remained at a high level until December. The period of low feeding intensity coincided with the time of spawning and the time of annulus formation of both scales and otoliths. The diet showed seasonal changes and two main periods were distinguished : December to July, when the fish fed mainly on bottom fauna, and August to November, when the diet included both bottom fauna and midwater and surface foods.
The gwyniad were shown to be opportunistic in feeding, the composition of the diet reflecting availability of food items rather than selective feeding on the part of the fish.     

Allozyme variation and population structure of the very narrow endemic Seseli farrenyi (Apiaceae)

Analyses have been made of allozyme variation of the narrow endemic species Seseli farrenyi Molero & J. Pujadas (Apiaceae), which has only three known populations in Catalonia with a total of around 2000 individuals. All three populations were sampled and subjected to starch gel electrophoresis. Nine enzymes were resolved and 14 loci were interpreted. We detected high values of polymorphism ( P = 83.3%, A = 3.0, H _e = 0.297), far exceeding those expected for endemic species ( P = 26.3%, A = 1.39, H _e = 0.063). Genetic diversity was greater within populations than among populations, and the value of gene flow was very high ( Nm = 5.85). Most loci showed deviations from Hardy– Weinberg equilibrium, possibly due to the presence of subpopulations. The main threats to this species are human activities (tourism, fires), while natural threats are minimal due to its high genetic diversity. Finally, we propose some conservation measures which include both in situ and ex situ strategies. © 2000 The Linnean Society of London, Botanical Journal of the Linnean Society , 2002, 138 , 305–314.     

Allozymic variation and relationships of the endangered cyprinodontid genus Valencia and its implications for conservation

Allozyme analysis was used to determine patterns of genetic variation and relationships within the genus Valencia , a group with two allopatric species, V. letourneuxi inhabiting the Balkan Peninsula, and V. hispanica which is endemic to the Iberian Peninsula. Products of 25 gene loci were analysed with AK *, FH *, LDH -1* and LDH -2* monomorphic when Fundulus heteroclitus macrolepidotus was not taken into account. Nine loci were diagnostic for both species of the genus Valencia . Levels of genetic variation of V. hispanica ( P =0·416, H ^e=0·118) and V. letourneuxi ( P =0·160, H _e=0·040) were higher than values reported previously. High population subdivision ( F _st=0·321) among V. hispanica populations indicates a clear interruption of genetic exchange among populations. High genetic variation and differentiation exhibited by populations of V. hispanica suggest that a recovery program should be carried out with natural stocks from the same localities.     

Population genetic analyses of an amphi-Atlantic species: Lychnis alpina (Caryophyllaceae)

Lychnis alpina is a perennial caryophyllaceous plant with an amphi-Atlantic distribution. 27 populations are described on the basis of allozyme data from 11 electro-phoretic loci. L. alpina has a relatively low level of genetic variation, 3 of the loci are polymorphic ( P.,_%= 20.2%) and the mean expected heterozygosity per indivindual is H³= 0.233 the three polymorphic loci included (H = 0.064, 11 loci included). Despite relatively low level of genetic variation, the genetic diversity among populations is relatively high with F_ST= 0.51. A hierarchial analysis of genetic diversity demonstrates that most of the genetic diversity exists as interpopulational, intra-regional diversity. Genetic identity is not associated with the intercontinental geographical distribution of the populations, neither is the diversity correspondant to taxonomic relationships.     

Diet of brown trout in relation to variation in abundance and size of pelagic fish prey

The seasonal diet of a predator, brown trout Salmo trutta [total length ( L _T) 17–69 cm] and simultaneous density and size‐structure of prey populations, vendace Coregonus albula and smelt Osmerus eperlanus (4–16 cm L _T), in a large boreal lake were analysed and compared in 2001 and 2002. The upper L _T limit for consumed prey was c . 40% of the predator L _T. All brown trout, however, preferred small (<10 cm L _T) and avoided large (≥10 cm L _T) prey. The results also suggested that equal densities of similar‐sized (4–10 cm L _T) fish of the two prey species led to random foraging on these species by brown trout, but if either one of the prey species predominated (>50%) in the lake, brown trout shifted to foraging on this species almost exclusively. Brown trout diets thus reflected the density dynamics of the two alternative prey species.     

Genetic Variation and Clonal Diversity of the Two Divergent Types of Clonal Populations of Leymus chinensis Tzvel on the Song Liao Steppe in the West of Northeastern China

The genetic variation and clonal diversity of two divergent types (grey-green and yellow-green) of clonal populations of Leymus chinensis Tzvel at 14 loci were compared. Total gene diversity (HT) and the coefficient of genetic differentiation (GST) were all higher for the yellow-green type (HT = 0.270; GST =0.186) than for the grey-green type (HT = 0.250; GST = 0.157) of L. chinensis. Rare alleles usually occurred as heterozygotes rather than homozygotes and significant deviations from Hardy-Weinberg equilibrium were found only at a few loci. This indicated that these two types of populations were mainly out-crossing. Clonal diversity, evenness of clones, and mean clone size were not significantly different between the two types. We found that differences between the clone size and genetic variation of the yellow-green type of populations occurred with different climate and habitat population groups. However, for the grey-green type of populations, these genetic variations decreased under conditions of different climate and habitat population groups.     

Genetic variation at isozyme loci in blue whiting from the north-east Atlantic

Genetic variation in blue whiting Micromesistius poutassou was investigated by starch gel electrophoresis of enzymes in tissue extracts. A total of 130 specimens from the spawning areas west of the British Isles were collected from trawl catches in 1990 ( n = 30) and 1992 ( n = 100). In 25 tissue enzyme loci screened for genetic variants in the 1990 sample, polymorphisms (0.95 criterion) were found at IDDH-2 *, IDHP-2 * and PGM-1 *, giving a frequency of polymorphic loci of P _0.95= 0.12. In pooled samples the average heterozygosity per locus was estimated at H _e =0.043 and the effective number of alleles per locus at 2.20, 1.45 and 1.53, respectively, for IDDH-2 *, IDHP-2 * and PGM-1 *.     

PATTERNS OF GENETIC ARCHITECTURE FOR LIFE-HISTORY TRAITS AND MOLECULAR MARKERS IN A SUBDIVIDED SPECIES

Abstract Understanding the utility and limitations of molecular markers for predicting the evolutionary potential of natural populations is important for both evolutionary and conservation genetics. To address this issue, the distribution of genetic variation for quantitative traits and molecular markers is estimated within and among 14 permanent lake populations of Daphnia pulicaria representing two regional groups from Oregon. Estimates of population subdivision for molecular and quantitative traits are concordant, with Q _ST generally exceeding G _ST. There is no evidence that microsatellites loci are less informative about subdivision for quantitative traits than are allozyme loci. Character-specific comparison of Q _ST and G _ST support divergent selection pressures among populations for the majority of life-history traits in both coast and mountain regions. The level of within-population variation for molecular markers is uninformative as to the genetic variation maintained for quantitative traits. In D. pulicaria , regional differences in the frequency of sex may contribute to variation in the maintenance of expressed within-population quantitative-genetic variation without substantially impacting diversity at the genic level. These data are compared to an identical dataset for 17 populations of the temporary-pond species, D. pulex .