Stress tolerance and population stability of rock pool Daphnia in relation to local conditions and population isolation

Small fragmented populations can lose genetic variability, which reduces population viability through inbreeding and loss of adaptability. Current and previous environmental conditions can also alter the viability of populations, by creating local adaptations that determine responses to stress. Yet, most studies on stress tolerance usually consider either the effect of genetic diversity or the local environment, missing a more holistic perspective of the factors contributing to stress tolerance among natural populations. Here, we studied how salinity stress affects population growth of Daphnia longispina, Daphnia magna, and Daphnia pulex from rock pools with varying degrees of population isolation and salinity conditions. Standing variation of in situ rock pool salinity conditions explained more variation in salt tolerance than the standing variation of population isolation or genetic diversity, in both a pulse and a press disturbance experiment. This indicates that the level of stress, which these natural populations experience, influences their response to that stress, which may have important consequences for the conservation of fragmented populations. However, long-term population stability in the field decreased with population isolation, indicating that natural populations experience a variety of stresses; thus, population isolation and genetic diversity may stabilize population dynamics over larger spatiotemporal scales.     

Effect of high-lysine mutations on the protein fractions of barley grain

We have studied the effects of six high-lysine barley mutations (Risø mutants 1508 and 56, Notch 1 and 2, lys 95 and 449) on the protein fractions of the grain. All mutants had a decreased relative and total amount of the lysine-poor hordein fraction, but only in Risø 1508 and 56 was the polypeptide composition of this fraction greatly affected. In all the mutants there were increases in the lysine-rich glutelin proteins and in nonprotein N while in Risø 1508 and the Notch mutants the total amount of salt-soluble proteins was also increased and their relative polypeptide composition substantially altered.This work was supported by EEC Contract No. 473 under the common program on plant protein improvement.     

Adaptive major histocompatibility complex (MHC) and neutral genetic variation in two native Baltic Sea fishes (perch Perca fluviatilis and zander Sander lucioperca) with comparisons to an introduced and disease susceptible population in Australia (P. fluviatilis): assessing the risk of disease epidemics

This study assessed the major histocompatibility complex (MHC) and neutral genetic variation and structure in two percid species, perch Perca fluviatilis and zander Sander lucioperca, in a unique brackish ecosystem, the Baltic Sea. In addition, to assess the importance of MHC diversity to disease susceptibility in these populations, comparisons were made to an introduced, disease susceptible, P. fluviatilis population in Australia. Eighty‐three MHC class II B exon 2 variants were amplified: 71 variants from 92 P. fluviatilis samples, and 12 variants from 82 S. lucioperca samples. Microsatellite and MHC data revealed strong spatial genetic structure in S. lucioperca, but not P. fluviatilis, across the Baltic Sea. Both microsatellite and MHC data showed higher levels of genetic diversity in P. fluviatilis from the Baltic Sea compared to Australia, which may have facilitated the spread of an endemic virus, EHNV in the Australian population. The relatively high levels of genetic variation in the Baltic Sea populations, together with spatial genetic structure, however, suggest that there currently seems to be little risk of disease epidemics in this system. To ensure this remains the case in the face of ongoing environmental changes, fisheries and habitat disturbance, the conservation of local‐scale genetic variation is recommended.     

Changes in the sugar content of barley anthers during culture on different carbohydrates

The quantity of glucose liberated by an anther homogenate from nine different carbon substrates, was examined to elucidate the rate of carbohydrate breakdown by anther tissues in culture. The possible relationship between these results and development in culture was examined by extraction, and HPLC analysis of the soluble sugars from anthers cultured on medium containing one of four of the previously tested carbon substrates. Similarly, sugars from anthers subjected to one of three different inductive pretreatments, were analysed and compared with extracts from fresh anthers. The most successful carbon source in culture, when measured by fresh, and dry weight gain of the developing anthers, were the diglucoses maltose and cellobiose. Glucose was probably liberated from these diglucose substrates at a similar rate to that at which it could be utilized during the development of microspore derived structures. Pretreatments were shown to increase the glucose content of anthers, providing a pulse of the sugar at the start of culture. This effect was particularly pronounced when anthers were preincubated on a medium containing mannitol, and this type of pretreatment was found to be the most successful in promoting the development of microspore derived structures (measured by gain in fresh and dry weight) when subsequently cultured on medium containing maltose.     

Using the International Classification of Functioning,Disability and Health (ICF) to Describe Children Referred to Special Care or Paediatric Dental Services

Children in dentistry are traditionally described in terms of medical diagnosis and prevalence of oral disease. This approach gives little information regarding a child’s capacity to maintain oral health or regarding the social determinants of oral health. The biopsychosocial approach, embodied in the International Classification of Functioning, Disability and Health - Child and Youth version (ICF-CY) (WHO), provides a wider picture of a child’s real-life experience, but practical tools for the application of this model are lacking. This article describes the preliminary empirical study necessary for development of such a tool - an ICF-CY Core Set for Oral Health. An ICF-CY questionnaire was used to identify the medical, functional, social and environmental context of 218 children and adolescents referred to special care or paediatric dental services in France, Sweden, Argentina and Ireland (mean age 8 years ±3.6yrs). International Classification of Disease (ICD-10) diagnoses included disorders of the nervous system (26.1%), Down syndrome (22.0%), mental retardation (17.0%), autistic disorders (16.1%), and dental anxiety alone (11.0%). The most frequently impaired items in the ICF Body functions domain were ‘Intellectual functions’, ‘High-level cognitive functions’, and ‘Attention functions’. In the Activities and Participation domain, participation restriction was frequently reported for 25 items including ‘Handling stress’, ‘Caring for body parts’, ‘Looking after one’s health’ and ‘Speaking’. In the Environment domain, facilitating items included ‘Support of friends’, ‘Attitude of friends’ and ‘Support of immediate family’. One item was reported as an environmental barrier – ‘Societal attitudes’. The ICF-CY can be used to highlight common profiles of functioning, activities, participation and environment shared by children in relation to oral health, despite widely differing medical, social and geographical contexts. The results of this empirical study might be used to develop an ICF-CY Core Set for Oral Health - a holistic but practical tool for clinical and epidemiological use.     

Genetic Diversity and Hybridisation between Native and Introduced Salmonidae Fishes in a Swedish Alpine Lake

Understanding the processes underlying diversification can aid in formulating appropriate conservation management plans that help maintain the evolutionary potential of taxa, particularly under human-induced activities and climate change. Here we assessed the microsatellite genetic diversity and structure of three salmonid species, two native (Arctic charr, Salvelinus alpinus and brown trout, Salmo trutta) and one introduced (brook charr, Salvelinus fontinalis), from an alpine lake in sub-arctic Sweden, Lake Ånn. The genetic diversity of the three species was similar and sufficiently high from a conservation genetics perspective: corrected total heterozygosity, H’_T = 0.54, 0.66, 0.60 and allelic richness, A_R = 4.93, 5.53 and 5.26 for Arctic charr, brown trout and brook charr, respectively. There were indications of elevated inbreeding coefficients in brown trout (G_IS = 0.144) and brook charr (G_IS = 0.129) although sibling relationships were likely a confounding factor, as a high proportion of siblings were observed in all species within and among sampling locations. Overall genetic structure differed between species, Fst = 0.01, 0.02 and 0.04 in Arctic charr, brown trout and brook charr respectively, and there was differentiation at only a few specific locations. There was clear evidence of hybridisation between the native Arctic charr and the introduced brook charr, with 6% of individuals being hybrids, all of which were sampled in tributary streams. The ecological and evolutionary consequences of the observed hybridisation are priorities for further research and the conservation of the evolutionary potential of native salmonid species.     

Genetic and morphological divergence along the littoral–pelagic axis in two common and sympatric fishes: perch,Perca fluviatilis (Percidae) and roach,Rutilus rutilus (Cyprinidae)

Individuals are constantly in competition with one another and, on both ecological and evolutionary timescales, processes act to reduce this competition and promote the gain of fitness advantages via diversification. Here we have investigated the genetic (AFLP) and morphological (geometric morphometrics) aspects of the littoral–pelagic axis, a commonly observed resource polymorphism in freshwater fishes of postglacial lakes. We found a large degree of variation in the genetic and morphological divergence between littoral and pelagic perch and roach across Swedish lakes. Although there was evidence of assortative mating (elevated kinship values) in both species, we could not find any significant coupling of morphology and genetic divergence. Instead, there was evidence that the extent of resource polymorphism may be largely caused by phenotypic plasticity. These results suggest that assortative mating, which can lead to genetically determined adaptive divergence, does occur in these species, particularly perch, but not according to genetically fixed morphological traits. The behavioural mechanisms facilitating associative mating need to be investigated to explore the interaction between phenotypic plasticity and adaptive genetic divergence and their roles in diversification. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114 , 929–940.     

Islands of water in a sea of dry land: hydrological regime predicts genetic diversity and dispersal in a widespread fish from Australia's arid zone, the golden perch (Macquaria ambigua)

Rivers provide an excellent system to study interactions between patterns of biodiversity structure and ecological processes. In these environments, gene flow is restricted by the spatial hierarchy and temporal variation of connectivity within the drainage network. In the Australian arid zone, this variability is high and rivers often exist as isolated waterholes connected during unpredictable floods. These conditions cause boom/bust cycles in the population dynamics of taxa, but their influence on spatial genetic diversity is largely unknown. We used a landscape genetics approach to assess the effect of hydrological variability on gene flow, spatial population structure and genetic diversity in an Australian freshwater fish, Macquaria ambigua. Our analysis is based on microsatellite data of 590 samples from 26 locations across the species range. Despite temporal isolation of populations, the species showed surprisingly high rates of dispersal, with population genetic structure only evident among major drainage basins. Within drainages, hydrological variability was a strong predictor of genetic diversity, being positively correlated with spring-time flow volume. We propose that increases in flow volume during spring stimulate recruitment booms and dispersal, boosting population size and genetic diversity. Although it is uncertain how the hydrological regime in arid Australia may change under future climate scenarios, management strategies for arid-zone fishes should mitigate barriers to dispersal and alterations to the natural flow regime to maintain connectivity and the species' evolutionary potential. This study contributes to our understanding of the influence of spatial and temporal heterogeneity on population and landscape processes.