Genetic variation in Drechslera teres populations as indicated by RAPD markers

Random amplified polymorphic DNA (RAPD) was used to assess genetic variation among 48 isolates of Drechslera teres originating from different sites in Finland. RAPD profiles were generated with five arbitrary 10-mer primers and revealed polymorphisms suitable for screening differentiation in this fungal population. Using UPGMA clustering analysis, a similarity coefficient of approximately 63% was observed between all D. teres isolates studied. The variation was, however, distributed on a small scale as different genotypes were found from the same plant. The isolates could not be grouped according to geographic origin, aggressiveness, growth rate or morphological features, indicating that the primers used in this study were neutral markers for these characters. The primers were, however, able to differentiate between isolates of Helminthosporium species (D. teres, Drechslera graminea and Bipolaris sorokiniana).     

内蒙古大庙中新世小哺乳动物化石埋藏学研究

捕食是小哺乳动物死亡最常见的原因,也导致被捕食动物遗骸发生明显改变.动物死亡后的风化、踩踏、搬运等过程也会改变动物的骨骼并影响到化石组合的形成.本文研究了内蒙古大庙三个中新世化石地点,时代从早中新世到晚中新世早期(约21～11.6 Ma).通过分析各小哺乳动物化石组合的沉积背景以及埋藏学特征识别化石埋藏的主要成因.结果显示出捕食是三个地点小哺乳动物化石埋藏的基本成因,而在两个年轻的地点中也有流水搬运与可能的踩踏因素的叠加.三个地点可能存在不一样的捕食者:早中新世地点以猫头鹰捕食为主,中、晚中新世地点则以日间活动的鸟类或哺乳类为主要捕食者.研究还显示小哺乳动物的系统发掘是可行的,在一定程度上可以减少采样过程中产生的破坏.     

Social dominance in free-living Willow Tits Parus montanus: determinants and some implications of hierarchy

Several features of social dominance among Willow Tit Parus montanus winter flocks were examined during a four-winter study. Birds of both sexes were evenly distributed over the 33 flocks studied. In nearly half of the flocks there was an adult pair accompanied by yearlings, but one-third of the flocks consisted of more than two adults with yearlings. Males were found to be dominant over and larger than females. Within a sex, yearlings were usually subordinate to adults. The effect of size on dominance, after controlled for sex and age, remained obscure in our field data. The hierarchical status of an individual was found to rise or at least stay the same in different years, which supports the "hopeful dominants" hypothesis, i.e. birds stay in flocks hoping to achieve a higher status in the future. The ranks of mates correlated highly significantly, implying that high-ranking birds were paired with other high-ranking birds and low-ranking birds with other low-ranking birds. Birds of different age and sex did not show any differences in the proportion of initiated aggressive encounters directed at other individuals. However, males were more aggressive to other males than to females and also tended to behave less aggressively towards their own mates than towards other individuals in the flock. This could be a male strategy to strengthen the pair-bond and to enhance mate protection described earlier in     

Differential expression of phenylalanine ammonia-lyase genes in barley induced by fungal infection or elicitors

Gene-specific probes were used to assess the expression patterns of four different phenylalanine ammonia-lyase ( pal ) genes in infected or elicitor-treated leaves and suspension-cultured cells of barley. Genes corresponding to hpal2 , hpal3 , hpal4 , and hpal6 were all induced by mercuric chloride and fungal infection by Bipolaris sorokiniana Sacc. (Shoem.) in barley ( Hordeum vulgare L. cv. Pokko) leaves, but with considerable variation in their expression level and timing. The expression patterns of hpal2 and hpal6 were similar, both showing a rapid, strong induction after treatment with mercuric chloride and a slower induction after fungal inoculation, whereas the more divergent hpal3 was induced at a later time and at a lower level after both treatments. Hpal4 was expressed with timing like that of hpal2 and hpal6 in infected or mercuric chloride-treated leaves but its expression was much weaker. Hpal2 and hpal4 were induced in elicitor-treated, suspension-cultured barley cells, whereas the expression of hpal3 was nearly undetectable, and hpal6 was strongly and constitutively present. All pal genes except hpal4 were developmentally regulated, but differentially expressed in various barley tissues. The results suggest that the four pal genes studied here might be responsible for the activation of different branches in the phenylpropanoid biosynthesis of barley.     

Species traits explain recent range shifts of Finnish butterflies

This study provides a novel systematic comparative analysis of the species characteristics affecting the range margin shifts in butterflies towards higher latitudes, while taking phylogenetic relatedness among species into account. We related observed changes in the northern range margins of 48 butterfly species in Finland between two time periods (1992–1996 and 2000–2004) to 11 species traits. Species with positive records in at least ten 10 km × 10 km grid squares (in the Finnish National Butterfly Recording Scheme, NAFI) in both periods were included in the study. When corrected for range size change, the 48 butterfly species had shifted their range margins northwards on average by 59.9 km between the study periods, with maximum shifts of over 300 km for three species. This rate of range shifts exceeds all previously reported records worldwide. Our findings may be explained by two factors: the study region is situated in higher latitudes than in most previous studies and it focuses on the period of most prominent warming during the last 10–15 years. Several species traits exhibited a significant univariate relationship with the range margin shift according to generalized estimation equations (GEE) taking into account the phylogenetic relatedness among species. Nonthreatened butterflies had on average expanded their ranges strongly northwards (84.5 km), whereas the distributions of threatened species were stationary (−2.1 km). Hierarchical partitioning (HP) analysis indicated that mobile butterflies living in forest edges and using woody plants as their larval hosts exhibited largest range shifts towards the north. Thus, habitat availability and dispersal capacity of butterfly species are likely to determine whether they will be successful in shifting their ranges in response to the warming climate.     

Critical Social Learning: A Solution to Rogers's Paradox of Nonadaptive Culture

Alan Rogers (1988) presented a game theory model of the evolution of social learning, yielding the paradoxical conclusion that social learning does not increase the fitness of a population. We expand on this model, allowing for imperfections in individual and social learning as well as incorporating a "critical social learning" strategy that tries to solve an adaptive problem first by social learning, and then by individual learning if socially acquired behavior proves unsatisfactory. This strategy always proves superior to pure social learning and typically has higher fitness than pure individual learning, providing a solution to Rogers's paradox of nonadaptive culture. Critical social learning is an evolutionarily stable strategy (ESS) unless cultural transmission is highly unfaithful, the environment is highly variable, or social learning is much more costly than individual learning. We compare the model to empirical data on social learning and on spatial variation in primate cultures and list three requirements for adaptive culture.     

High survival rate and site fidelity in the Siberian Tit Parus cinctus, a focal species of the taiga

The Siberian Tit Parus cinctus population of Finland, and probably of the whole of Fennoscandia, has declined dramatically during this century. Understanding its population dynamics is essential for its conservation. We studied annual survival rate and dispersal distance of both breeding and fledgling Siberian Tits during 1989-97 in a moderately managed forest habitat near the southern border of its range in Kuusamo, northeastern Finland. Breeding density was low, averaging 0.51 pairs/km in a nestbox area of about 42 km². This was probably an underestimate, because we did not search for nests in natural holes. However, following its population decline, overall densities at the southern border of the range are low. The study area was, however, suitable breeding habitat as reflected by their high nesting success. Brood size at fledging averaged 7.45 young, and reproductive output was 6.16 young per breeding pair, including failed nests. Clutch size adjustment was successful among pairs producing fledglings because, on average, 92.6% of the eggs laid produced young in successful broods. Median distance between consecutive breeding attempts was 100 m for both males and females (range 0–2500 m and 0–6000 m, respectively). Natal dispersal distance was significantly longer in females than in males. We applied Cormack-Jolly-Seber modelling to estimate survival and recapture probabilities separately. Survival of breeding birds was not sex-related, averaging 0.69 annually. Some of the ringed fledglings (3.0%) were later captured as breeders in the area. This is an underestimate of local survival rate due to incomplete recapturing of breeding birds. The implications of these results with respect to the conservation status of the species are discussed.