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。     

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.     

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     

Small spermatophore size and reduced female fitness in an isolated butterfly population

1. The Glanville fritillary butterfly (Melitaea cinxia L.) has a small population (N_e ～ 100) on the small island of Pikku Tytärsaari (PT) in the Gulf of Finland. The population has remained completely isolated for ～100 generations, which has resulted in greatly reduced genetic variation and high genetic load (low fitness). In particular, females lay small egg clutches with a low egg‐hatching rate in comparison with a large reference population in the Åland Islands (ÅL). 2. In the present study, to what extent egg clutch size and egg‐hatching rate are influenced by male population and spermatophore size was analysed. 3. Spermatophore size increases with male body size, is smaller after the first mating, and is smaller in the small PT population. In the ÅL population but not in the PT population, the egg‐hatching rate increases with spermatophore size. The egg‐hatching rate of PT females is higher when mated with ÅL males than when mated with PT males (heterosis), but there is no such effect on clutch size. The clutch size of ÅL females is, however, reduced when mated with PT males. 4. These results indicate that both male and female traits contribute to reduced reproductive fitness in the small isolated population.     

Complex competitive interactions in four species of Lucilia blowflies

Abstract.

• 1 The effects of intraspecific and interspecific larval competition on larval survival, adult size, adult longevity and fecundity were quantified in four species of coexisting Lucilia blowflies: illustris, silvarum, sericata and caesar.
• 2 There was a general negative effect of increasing density on larval and adult survival, size and fecundity. Additionally, complex species-specific and frequency-dependent responses were identified, which were not expected in these biologically and morphologically closely similar species.
• 3 Lucilia illustris, the numerically dominant species in the natural community, was a superior competitor to L.silvarum at intermediate densities but an inferior competitor at high density. Such nonlinear responses may be related to differences in the life histories and larval behaviour of the species (bigger eggs and more contest-type outcome of competition in L.silvarum).
• 4 We parameterized a model of interspecific competition on a subdivided resource in an attempt to reconcile the conflicting results on larval competitive abilities and the abundances of the species in the field. Using laboratory and field-estimated parameter values the model predicted coexistence of L.illustris and L.silvarum and the observed numerical dominance of the former species. The average densities of flies in the field are limited to relatively low levels, apparently preventing L.silvarum (the superior competitor at high density) from dominating and excluding L. illustris.

     

Single-species metapopulation dynamics: concepts, models and observations

This paper outlines a conceptual and theoretical framework for single-species metapopulation dynamics based on the Levins model and its variants. The significance of the following factors to metapopulation dynamics are explored: evolutionary changes in colonization ability; habitat patch size and isolation; compensatory effects between colonization and extinction rates; the effect of immigration on local dynamics (the rescue effect); and heterogeneity among habitat patches. The rescue effect may lead to alternative stable equilibria in metapopulation dynamics. Heterogeneity among habitat patches may give rise to a bimodal equilibrium distribution of the fraction of patches occupied in an assemblage of species (the core-satellite distribution). A new model of incidence functions is described, which allows one to estimate species' colonization and extinction rates on islands colonized from mainland. Four distinct kinds of stochasticity affecting metapopulation dynamics are discussed with examples. The concluding section describes four possible scenarios of metapopulation extinction.     

A Simulation Model for the Annual Frost Hardiness and Freeze Damage of Scots Pine

The changes in the frost hardiness of Scots pine were modelledby a dynamic model where the input variables were temperatureand photoperiod and the phase of annual development. The damagecaused by freezing was described by the sigmoidal relationshipbetween the relative needle damage and freezing temperature.The model simulations were carried out using temperature datafrom two sites in central Finland—Suonenjoki and Tampere.The validity of the frost hardiness model was tested with measuredfrost hardiness data from Suonenjoki. The effects of climaticwarming were also simulated by increasing temperature of thelong-term climatic data. Genotypic differences in chilling requirement,which determines the timing of the reduction of hardening competence,were included in the simulations. The simulated needle damageincreased as a result of climatic warming, and the differencesin the chilling requirement had a stronger effect on the amountof damage in the warmed climate than in the present climate.A large variation between years was found in the level of damage. Annual development; climatic change; dynamic model; freeze damage; frost hardiness,Pinus sylvestris ; Scots pine