The effects of selection,drift and genetic variation on life‐history trait divergence among insular populations of natterjack toad,Bufo calamita

Although loss of genetic variation is frequently assumed to be associated with loss of adaptive potential, only few studies have examined adaptation in populations with little genetic variation. On the Swedish west coast, the northern fringe populations of the natterjack toad Bufo calamita inhabit an atypical habitat consisting of offshore rock islands. There are strong among‐population differences in the amount of neutral genetic variation, making this system suitable for studies on mechanisms of trait divergence along a gradient of within‐population genetic variation. In this study, we examined the mechanisms of population divergence using Q_ST–F_ST comparisons and correlations between quantitative and neutral genetic variation. Our results suggest drift or weak stabilizing selection across the six populations included in this study, as indicated by low Q_ST–F_ST values, lack of significant population × temperature interactions and lack of significant differences among the islands in breeding pond size. The six populations included in this study differed in both neutral and quantitative genetic variation. Also, the correlations between neutral and quantitative genetic variation tended to be positive, however, the relatively small number of populations prevents any strong conclusions based on these correlations. Contrary to the majority of Q_ST–F_ST comparisons, our results suggest drift or weak stabilizing selection across the examined populations. Furthermore, the low heritability of fitness‐related traits may limit evolutionary responses in some of the populations.     

de novo转录组学分析华南地区入侵植物五爪金龙代谢特征

为探究华南地区严重入侵植物五爪金龙(Ipomoea cairica)生物入侵的分子机制,对五爪金龙及其近缘种七爪金龙(I. digitata)和裂叶牵牛(I. nil)进行de novo转录组测序和组装,得到56551条unigenes,其中56522条得到注释,7815条GO注释,15615条COG注释,180201条KEGG数据库注释。转录组分析结果表明,五爪金龙氮代谢通路关键酶基因的表达高于对照。次生代谢关键酶(PAL、4CL、CAD、查耳酮合酶、苯基丙乙烯酮异构酶、槲皮黄3-O-甲基转移酶等)基因在五爪金龙与七爪金龙及裂叶牵牛中均得到协同性的差异表达,而这些代谢通路指导的产物合成对五爪金龙的抗逆境能力、生长、化感作用等均起关键作用。关键基因的RT-qPCR验证结果与转录组结果具有一致性。因此,这从分子生物学层面上对解释五爪金龙在华南地区的入侵机制提供了新的证据。     

Features of the underwater light climate just below the surface in some New Zealand inland waters

1. Using sampling rates of 8–64 Hz we found clear indications of extensive and high frequency fluctuations of underwater photosynthetically active radiation (PAR) just below the surface (0.016–1.1 m) in some New Zealand water bodies. High variability and flashing occurred down to at least 3 m depth.
2. PAR variability increased under the influence of bright sunshine if wind roughening of the surface took place. Concomitantly, the average PAR levels declined by about 10%. However, even when the surface was shaded, high variability of PAR persisted.
3. Under a calm surface, PAR irradiance followed a log normal distribution. This occurred independently of the presence of direct sunlight. However, when the surface was roughened by wind in sunshine, PAR immediately switched to a Gumbel (extreme value type EV1) distribution.
4. Neither wave action nor wave focusing of incident irradiance would explain the wide range of PAR close to the water surface, although both factors add to the PAR variability.
5. The data indicate that transmittance through the surface is highly variable at the temporal and spatial scales studied, and that the irregularity of the air–water interface is instrumental in bringing about the observed fluctuations of PAR just below the surface.     

Colonization in metapopulations: a review of theory and observations

In metapopulation dynamics turnover of populations in isolated patches may be frequent. Regional survival of a species in such a system with frequent extinctions hinges on its colonization ability. Colonization is more than just dispersal; when a propagule reaches a new patch it faces higher extinction probabilities than does an established population. Extinction models as well as empirical data suggest that a large propagule with a potential for rapid increase in a varying environment, or with a low mortality rate in an environment perceived as constant, has a higher probability of successful colonization. Large variation in population size when it is still small increases the risk of failure. Factors introducing such variation are demographic stochasticity and environmental variation. It is hard to single out demographic traits that ensure good colonizing ability, since colonization can be achieved in many different ways, but generalists and species with self-fertilization seem to be superior.     

Using predictive models to estimate effects of flow regulation on net-spinning caddis larvae in North Swedish rivers

1. Effects of flow regulation on abundance and richness of net-spinning caddis larvae (Hydropsychoidea; Trichoptera) were examined in fifty-two North Swedish rivers. Models based on conditions at unregulated sites were used to predict densities at impacted sites and the residuals, i.e. the differences between observed and predicted numbers, were used as measures of the effects.
2. Two broad categories of impacted sites were identified. Sites with regulated but unreduced flow often have reduced seasonal flow variation and slightly enhanced short-term variation, while those with reduced flow usually have long periods of low and stable flow occasionally interrupted by short periods of violently fluctuating flow.
3. The abundance of net-spinning caddis larvae was significantly lower than predicted at both types of sites (reduction 30%), while richness was significantly reduced only at sites with reduced flow (reduction 20%).
4. A subsequent analysis of the relationship between the effects and variables altered by flow regulations, e.g. flow magnitude and flow variation, indicated that species richness was primarily affected by the occurrence of periods with zero flow, while negative effects of abundance were associated with high flow variability.
5. Significant negative effects on the abundance of individual taxa were observed for Cheumatopsyche lepida and Hydropsyche pellucidula at sites with regulated but unreduced flow.
6. Analyses of the relationships between the effects and regulation-related variables suggest that H. siltalai was significantly negatively affected by the occurrence of zero flow and that negative effects on Arctopsyche ladogensis were associated with flow reduction and high flow variability.     

A novel disorder caused by defective biosynthesis of N-linked oligosaccharides due to glucosidase I deficiency

Glucosidase I is an important enzyme in N-linked glycoprotein processing, removing specifically distal alpha-1,2-linked glucose from the Glc3Man9GlcNAc2 precursor after its en bloc transfer from dolichyl diphosphate to a nascent polypeptide chain in the endoplasmic reticulum. We have identified a glucosidase I defect in a neonate with severe generalized hypotonia and dysmorphic features. The clinical course was progressive and was characterized by the occurrence of hepatomegaly, hypoventilation, feeding problems, seizures, and fatal outcome at age 74 d. The accumulation of the tetrasaccharide Glc(alpha1-2)Glc(alpha1-3)Glc(alpha1-3)Man in the patient's urine indicated a glycosylation disorder. Enzymological studies on liver tissue and cultured skin fibroblasts revealed a severe glucosidase I deficiency. The residual activity was <3% of that of controls. Glucosidase I activities in cultured skin fibroblasts from both parents were found to be 50% of those of controls. Tissues from the patient subjected to SDS-PAGE followed by immunoblotting revealed strongly decreased amounts of glucosidase I protein in the homogenate of the liver, and a less-severe decrease in cultured skin fibroblasts. Molecular studies showed that the patient was a compound heterozygote for two missense mutations in the glucosidase I gene: (1) one allele harbored a G-->C transition at nucleotide (nt) 1587, resulting in the substitution of Arg at position 486 by Thr (R486T), and (2) on the other allele a T-->C transition at nt 2085 resulted in the substitution of Phe at position 652 by Leu (F652L). The mother was heterozygous for the G-->C transition, whereas the father was heterozygous for the T-->C transition. These base changes were not seen in 100 control DNA samples. A causal relationship between the alpha-glucosidase I deficiency and the disease is postulated.     

Genetic and morphological variation in Dunlin Calidris alpina breeding in the Palearctic tundra

The extensive overlap in morphological characters between populations of Dunlin Calidris alpina imposes problems of determining the origin of migrating and wintering birds. The morphology of the birds also varies between the sexes, and the sex of a Dunlin may often be difficult to determine. To clarify if mitochondrial DNA can be used to identify which breeding areas migrating Dunlin come from, we investigated the occurrence of different mtDNA haplotypes in Dunlin from eight breeding areas on the Russian and Siberian tundra. Four haplotypes were found and at most sites more than one haplotype occurred. The European haplotype predominated in the area west of the Taymyr Peninsula, the Siberian haplotype in central Siberia (from the Taymyr Peninsula to the Lopatka Peninsula) and the Beringian haplotype in eastern Siberia. One individual of an Alaskan haplotype, not detected previously among breeding birds outside North America, was found on Wrangel Island. The sex of each bird was identified genetically and the morphology of males and females was analysed separately. Birds with the European haplotype were generally smaller than birds with the Beringian or Alaskan haplotypes. Birds possessing the Siberian haplotype showed intermediate values in most cases. After compensating for differences between sites, males with the Siberian haplotype had significantly longer bills than males having the European haplotype. Multiple regressions indicate that mitochondrial DNA analysis improves models estimating the breeding origin of migrating Dunlin.