Wing shape variation of Finnish and Central European Willow Warblers Phylloscopus trochilus and Chiffchaffs P. collybita

Wing shape variation of European Willow Warblers Phylloscopus trochilus and Chiffchaffs P. collybita was studied using indices calculated from wing formulae. Our data were from free-living local populations of P. t. acredula and P. c. abietinus from southern Finland, and P. t. trochilus and P. c. collybita from southwestern Germany.
There were no significant shape differences between the subspecies of the Willow Warbler in which sexual dimorphism was pronounced. The subspecies of the Chiffchaff were significantly different while the sexes were not. There were also significant differences between adult and immature individuals in the autumn. The intrapopulation variation must be considered in attempts to recognize different subspecies or populations in data on birds caught during migration.
In the Willow Warbler at least, the difference between age-groups was larger in males than in females. If the change in wing formula due to the complete pre-nuptial moult is similar in both sexes, juvenile males intermediate between adult females and adult males suffer disproportionately high mortality. It was earlier suggested that sexual selection increases body size in Willow Warbler males, but the present results imply additional selection pressures for increasing sexual dimorphism.     

集合种群动态:理论与应用

集合种群是指一相对独立地理区域内各个局域种群的集合,这些局域种群通过一定程度的个体迁移而连结在一起。集合种群理论是生态学最新分支领域——空间生态学的主要研究途径之一;它关注的是局域种群之间个体迁移的动力学后果,以及具有不稳定局域种群物种的区域续存的条件。本文较为全面地介绍了集合种群理论的基本内容,并展望其应用前景。     

Fitness differences associated with Pgi SNP genotypes in the Glanville fritillary butterfly (Melitaea cinxia)

Allozyme variation at the phosphoglucose isomerase (PGI) locus in the Glanville fritillary butterfly (Melitaea cinxia) is associated with variation in flight metabolic rate, dispersal rate, fecundity and local population growth rate. To map allozyme to DNA variation and to survey putative functional variation in genomic DNA, we cloned the coding sequence of Pgi and identified nonsynonymous variable sites that determine the most common allozyme alleles. We show that these single‐nucleotide polymorphisms (SNPs) exhibit significant excess of heterozygotes in field‐collected population samples as well as in laboratory crosses. This is in contrast to previous results for the same species in which other allozymes and SNPs were in Hardy–Weinberg equilibrium or exhibited an excess of homozygotes. Our results suggest that viability selection favours Pgi heterozygotes. Although this is consistent with direct overdominance at Pgi, we cannot exclude the possibility that heterozygote advantage is caused by the presence of one or more deleterious alleles at linked loci.     

Climate change and cyclic predator–prey population dynamics in the high Arctic

The high Arctic has the world's simplest terrestrial vertebrate predator–prey community, with the collared lemming being the single main prey of four predators, the snowy owl, the Arctic fox, the long-tailed skua, and the stoat. Using a 20-year-long time series of population densities for the five species and a dynamic model that has been previously parameterized for northeast Greenland, we analyzed the population and community level consequences of the ongoing and predicted climate change. Species' responses to climate change are complex, because in addition to the direct effects of climate change, which vary depending on species' life histories, species are also affected indirectly due to, e.g., predator–prey interactions. The lemming–predator community exemplifies these complications, yet a robust conclusion emerges from our modeling: in practically all likely scenarios of how climate change may influence the demography of the species, climate change increases the length of the lemming population cycle and decreases the maximum population densities. The latter change in particular is detrimental to the populations of the predators, which are adapted to make use of the years of the greatest prey abundance. Therefore, climate change will indirectly reduce the predators' reproductive success and population densities, and may ultimately lead to local extinction of some of the predator species. Based on these results, we conclude that the recent anomalous observations about lack of cyclic lemming dynamics in eastern Greenland may well be the first signs of a severe impact of climate change on the lemming–predator communities in Greenland and elsewhere in the high Arctic.     

Dispersal in the Glanville fritillary butterfly in fragmented versus continuous landscapes: comparison between three methods

1. Habitat fragmentation may lead to natural selection on dispersal rate and other life‐history traits. Both theoretical analyses and empirical studies suggest that habitat fragmentation may select either for increased or decreased dispersal depending on the traits of the species and the characteristics of the landscape. 2. Dispersal and movement rates in Glanville fritillary butterflies (Melitaea cinxia) originating from a continuous landscape in China and from a highly fragmented landscape in Finland were compared using three different methods. 3. The methods included replicated mark‐release‐recapture (MRR) experiments conducted in the natural environments in China and Finland, tracking with harmonic radar of captive‐reared but free‐flying butterflies in a common environment in the field, and replicated common garden experiments in a large outdoor population cage. 4. The results were largely consistent, showing that butterflies from the more continuous landscape in China had a lower movement rate than butterflies originating from the fragmented landscape in Finland. Butterflies originating from newly‐established populations in Finland moved significantly longer distances than butterflies originating from old populations in Finland or from China, demonstrating significant intra‐specific variation in dispersal rate in Finland. These results are consistent with model predictions for the Glanville fritillary. 5. The tracking experiment revealed a result that would have been impossible to obtain with MRR experiments: movement rate was influenced by a significant interaction between population origin (China vs. Finland) and ambient air temperature.     

Metapopulation dynamics: brief history and conceptual domain

We review the early development of metapopulation ideas, which culminated in the well-known model by Levins in 1969. We present a survey of metapopulation terminology and outline the kinds of studies that have been conducted on single-species and multispecies metapopulations. Metapopulation studies have important conceptual links with the equilibrium theory of island biogeography and with studies on the dynamics of species living in patchy environments. Metapopulation ideas play an increasingly important role in landscape ecology and conservation biology.     

Heritability of and strong single gene (Pgi) effects on life‐history traits in the Glanville fritillary butterfly

We estimated broad‐sense heritabilities (H²) of 13 female and seven male life‐history traits of the Glanville fritillary butterfly (Melitaea cinxia) under semi‐natural conditions in a large outdoor population cage. The analysis was based on full‐sib families collected as young larvae in the field and reared under common garden conditions. We found significant genetic variance in female lifespan, fecundity, number of matings and host‐plant preference as well as in male body mass and mobility. Apart from host‐plant preference, female traits that were more strongly correlated with lifetime reproductive success (LRS; measured as total number of eggs laid) had higher H². LRS itself exhibited significant heritability. Host‐plant preference had very high H², consistent with a previously reported genetically determined geographical cline in host‐plant preference in the study area. Lifespan and egg hatching rate were significantly associated with a SNP in the coding region of the Pgi gene, for which there is previous evidence for balancing selection. Selection on Pgi, which furthermore shows spatial and temporal variation, may maintain genetic variance in fitness‐related life‐history traits. In contrast, we found no strong evidence for life‐history trade‐offs.     

Changing Environmental Effects on Frost Hardiness of Scots Pine During Dehardening

The effects of raised temperature and extended photoperiod onthe dehardening of quiescent and winter-hardy Scots pine saplingswere examined in an open-top-chamber experiment. The saplingswere exposed during winter to natural, square-curve fluctuating(between 1 and 11 °C with a 14 d interval), and constant(6 °C) temperatures with a natural and an extended (17 h)photoperiod. Frost hardiness of needles was determined by controlledfreezing tests and visual damage scoring. The constant 6 °Ctemperature treatment caused a gradual dehardening of needleswhereas under fluctuating temperatures the level of frost hardinessfluctuated. Trees exposed to extended photoperiods were lesshardy than under natural photoperiods after the initiation ofshoot elongation, but before this there were no clear differencesin frost hardiness between different photoperiodic treatments.The results indicate that the frost hardening competence ofScots pine changes during quiescence. Climate change; frost hardiness; hardening competence; photoperiod; Pinus sylvestris, Scots pine; temperature