Macoma balthica in the White and Barents Seas: properties of a widespread marine hybrid swarm (Mollusca: Bivalvia)

A main molecular subdivision in the circumpolar Macoma balthica complex has been described between Atlantic and Pacific taxa. In NE Europe, the clams of the White and Barents Seas, however, show deviant genetic structures. Using allozyme and mitochondrial DNA data, we explore the hypothesis that these deviations result from hybridization between an Atlantic (M. b. rubra) and an invading Pacific (M. b. balthica) lineage. A practically pure Atlantic Macoma extends from France north to the Varanger Peninsula (NE Norway), whereas populations farther east have genetic compositions intermediate between true Atlantic and true Pacific. Admixture estimates range from 32 to 90% Pacific contribution, with a notable deviation in a nearly pure Atlantic outpost in the Mezen Bay (NE White Sea). The pattern of variation is not one of a simple collinear mixing however. Different characters exhibit different degrees of introgression, and the relative introgression varies regionally. Yet, there are practically no interlocus genotypic disequilibria between the diverged loci, which brings out the White Sea-Barents Sea M. balthica as the best-documented marine animal hybrid swarms so far, arisen through amalgamation of genomes previously isolated since pre-Pleistocene times. On top of the main admixture pattern, strong geographical structuring is also seen in characters unrelated to the principal systematic distinction. The persistence of the regional patterns indicates restricted gene flow at the present time, despite the high dispersal potential of the species. The causes of this structuring could be in a complex history of colonization events and features of local hydrography enhancing isolation and divergence of populations.     

The soy effect in the disease models of nonbacterial prostatitis and obstructive voiding

The goal of this study was to improve the understanding of the potential significance of dietary soy for human health by investigating its effects in the animal models of nonbacterial prostatitis and urethral obstruction. Nonbacterial prostatitis was induced in adult Noble rats with the combined treatment of testosterone and 17beta-estradiol. The inflammatory foci categorized into three forms were counted and correlated with expression of an estrogen-responsive gene, progesterone receptor (PR), in the dorsolateral lobes of the rats on soy (+) and soy (-) diets. Development of obstructive voiding after neonatal estrogenization of Noble rats (NeoDES rats) was followed with urodynamic measurements in rats on soy (+) and soy (-) diets. The amounts of genistein and daidzein, two major soy-derived isoflavones, were measured in the urine of Noble rats by the high-performance liquid chromatography-photodiodearray method. Dietary soy decreased the total number of inflammatory foci while no demonstrable effects were seen on the cellular composition of the infiltrates. Soy did not increase the weights of the pituitary gland, testes, or sex accessory glands, but it did increase the number of PR-positive epithelial cells in the dorsolateral prostate. It also decreased the bladder pressures in NeoDES rats but did not increase the flow rates. The soy effects may be mediated by the strong estrogen influence involved in the animal models. Dietary soy had anti-inflammatory effects in the prostate but only marginal effects on the development of obstructive voiding in Noble rats. The anti-inflammatory effects of soy may contribute to the lower prevalence of prostatitis-like symptoms and the historically lower risk of benign prostatic hyperplasia in Japan; however, no evidence was found that regular consumption of soy influences the age-related development of lower urinary tract symptoms or decline of flow rate.     

Scaling distributional patterns of butterflies across multiple scales: Impact of range history and habitat type

Aim

Assessing the threat status of declining but yet widespread species poses a challenge to applied ecologists. Previous studies using a common metric to describe the spatial aggregation of occurrences across multiple scales, the fractal dimension D_ij, have suggested that species’ distributional trends may be deduced from readily understandable spatial patterns: Expanding species are expected to show more aggregated spatial distributions (higher value of D_ij) than declining species (lower value of D_ij). Here, we revisited these predictions using a large‐scale empirical dataset on Finnish butterflies.

Location

Finland.

Methods

For each butterfly species (n = 97) and across three spatial scales (grid squares of 10 km, 50 km and 100 km), we calculated the area of occupancy (AOO_i) as the sum of occupied grid squares. We employed values of AOO_i to derive the D_ij for each butterfly species. We then used these metrics to compare the changes in spatial patterns of distribution (?AOO_i and ?D_ij) between two time periods, 2000–2002 and 2009–2011.

Results

Majority of the studied butterfly species showed declining areas of occupancy (at the scale of 10 km, ?AOO₁₀) and fractal dimensions (across the scales from 10 km to 100 km, ?D_10–100) between the two study periods. In contrast to predictions, AOO₁₀ and D_10–100 showed negative impacts on the ?AOO₁₀, an observation that may be explained by the high proportion of declining species in our data. Butterfly species with the greatest fractal dimensions at regional scales (D_10–100) in the years 2000–2002 showed both positive long‐term distributional trends and most notable northern recent range limit shifts.

Main conclusions

Our results were in most cases congruent with the prediction of higher fractal dimension values in expanding compared to declining species. As a novel observation, many butterflies expanded northwards in spite of their occurrences getting simultaneously more scattered, particularly in southern Finland.

     

Population structure of a threatened plant, Pulsatilla patens, in boreal forests: modelling relationships to overgrowth and site closure

Pulsatilla patens (L.) Mill. (Ranunculaceae) is a threatened plant which in Fennoscandia favours south-facing, warm slopes of pine-dominated esker forests. The cessation of cattle grazing, modern forestry practices, and especially efficient fire prevention have resulted in closure of undergrowth vegetation in these forests. Using generalized linear models (GLM), we studied the relationships between habitat factors (covers of field and ground layer and amount of litter) and the population structure of P. patens in 48 populations in Finland in order to identify favourable conditions for regeneration. The largest populations occurred at sites with intermediate values of both ground and field layer. The number of juvenile plants was also highest at intermediate values of ground layer. Dense moss layer and abundant litter had a negative effect on the flowering of P. patens. In conclusion, creation and maintenance of habitat heterogeneity to prevent the closure of undergrowth vegetation is of paramount importance for the successful reproduction of P. patens.     

Extinction Events Can Accelerate Evolution

Extinction events impact the trajectory of biological evolution significantly. They are often viewed as upheavals to the evolutionary process. In contrast, this paper supports the hypothesis that although they are unpredictably destructive, extinction events may in the long term accelerate evolution by increasing evolvability. In particular, if extinction events extinguish indiscriminately many ways of life, indirectly they may select for the ability to expand rapidly through vacated niches. Lineages with such an ability are more likely to persist through multiple extinctions. Lending computational support for this hypothesis, this paper shows how increased evolvability will result from simulated extinction events in two computational models of evolved behavior. The conclusion is that although they are destructive in the short term, extinction events may make evolution more prolific in the long term.     

Relaxation Along a Fictitious Field (RAFF) and Z-spectroscopy using Alternating-Phase Irradiation (ZAPI) in Permanent Focal Cerebral Ischemia in Rat

Cerebral ischemia alters the molecular dynamics and content of water in brain tissue, which is reflected in NMR relaxation, diffusion and magnetization transfer (MT) parameters. In this study, the behavior of two new MRI contrasts, Relaxation Along a Fictitious Field (RAFF) and Z-spectroscopy using Alternating-Phase Irradiation (ZAPI), were quantified together with conventional relaxation parameters (T₁, T₂ and T_1ρ) and MT ratios in acute cerebral ischemia in rat. The right middle cerebral artery was permanently occluded and quantitative MRI data was acquired sequentially for the above parameters for up to 6 hours. The following conclusions were drawn: 1) Time-dependent changes in RAFF and T_1ρ relaxation are not coupled to those in MT. 2) RAFF relaxation evolves more like transverse, rather than longitudinal relaxation. 3) MT measured with ZAPI is less sensitive to ischemia than conventional MT. 4) ZAPI data suggest alterations in the T₂ distribution of macromolecules in acute cerebral ischemia. It was shown that both RAFF and ZAPI provide complementary MRI information from acute ischemic brain tissue. The presented multiparametric MRI data may aid in the assessment of brain tissue status early in ischemic stroke.     

Spatial consistency in susceptibility of prey species to predation by two Accipiter hawks

Predators impose strong selection on their prey, regulate prey populations and engage in coevolutionary interactions with their prey. The intensity of selection and the strength of coevolutionary interactions will depend on how stringent predators are in their choice of prey. We estimated susceptibility of different species of birds to predation by two common raptors, the northern goshawk Accipiter gentilis and the Eurasian sparrowhawk A. nisus, in an agricultural landscape in Denmark and boreal forests in Finland. We estimated susceptibility to predation as the deviation of the log₁₀‐transformed observed frequency of prey of different species from the log₁₀‐transformed expectation based on population density during the breeding season. We found a high degree of consistency in susceptibility to predation by the goshawk in two areas in Finland. More importantly, there was significant consistency in susceptibility to predation between Denmark and Finland, albeit the degree of consistency in the goshawk was higher than in the sparrowhawk. There was considerable overlap in susceptibility to predation between goshawk and sparrowhawk in Denmark, but not in Finland, implying differences in intensity of interspecific competition as reflected by a much higher extent of goshawk predation on sparrowhawks in Denmark than in Finland. Our findings suggest that hawks impose similar selection pressures on their prey populations, and that the degree of consistency has implications for intensity of interspecific killing.