切尔诺贝利核事故以来隔离区动物生态的研究概况

综述了切尔诺贝利核事故以来乌克兰Schmalhausen动物研究所(SIZ)对核工厂周围隔离区(exclusionzone ,EZ)的野生动物所进行的长达20年的放射生态学调查研究。基于乌克兰以往鸟类迁移的观察资料,评估了137Cs和 90Sr在隔离区候鸟体内的含量。而且还选择一些动物物种作为环境状况的标准指示生物,目的是为了阐明1 37Cs在隔离区脊椎动物体内的污染情况;整个第聂伯河流域、基辅行政区和隔离区软体动物贝壳内 90Sr的β活性。结果表明不同物种相对放射性核累积、迁移和累积因素呈有规律的季节性和长期性变化趋势,这些参数的运用可以大大地减少数据的波动和复杂性。直接辐射毁坏森林后,营养链的崩溃和病死树昆虫害虫的爆发导致了其次级生态变化。99 %的隔离区并不直接受辐射的影响,人员撤离、农业和森林管理停止以及大规模排除污染是这些区域生态变化的主要因素。在初始变化之后,由于自然资源、捕食者和偷猎者等的限制,隔离区的动物密度和分布达到一个稳定的极限值。数年前成功地在隔离区引入了一群蒙古野马,该群体保持了稳定增长。重新评估了以前划定的若干自然保护位点目前的保护状况,并提出了建议扩大这些自然保护区的范围等保护措施。     

Evidence of wolf dispersal in anthropogenic habitats of the Polish Carpathian Mountains

In the course of their maturation, most young wolves leave their natal pack and disperse in search for mating partners, improved food availability and new territories. We investigated whether this dispersal is affected by anthropogenic infrastructure in a 5,000 km2 area of the eastern region of the Polish Carpathian Mountains occupied by wolves. A radio-collared male wolf covered 230 km while dispersing through forested hills and densely populated valleys. To test if such dispersal is common in the population we analysed by microsatellite genotyping 39 samples taken from live-trapped wolves or wolves found dead in the study area. Although the obtained genotypes were assigned to different clusters in Bayesian tests, we could not ascribe this structure to landscape features, but rather to shared ancestry of wolf individuals found in distant locations. Moreover, we could not detect a spatial genetic structure in the wolf population, indicating a random occurrence of genotypes within the study area. Observation of the dispersing wolf and the absence of spatial genetic structure imply that wolves are still able to roam the entire area despite high densities of roads and a dense human population. Thus, we concluded that the existing anthropogenic infrastructure does not restrict wolf dispersal in the area and the studied wolves represent a coherent part of the Polish Carpathian wolf population.     

Evidence for long-distance dispersal in a sedentary passerine, Gymnorhina tibicen (Artamidae)

Australian magpies (Gymnorhina tibicen) are group-living birds found across much of mainland Australia. Adults commonly remain in a breeding territory until death. Young of the year either remain on the natal (birth) site or are forced by their parents to disperse. Observational studies in south-eastern Australia suggest that most dispersing juveniles settle within 7 km of their natal territory. Therefore, despite potential for considerable gene flow (via flight), social organization predisposes magpies towards local population structuring. In this study, we measured genetic variation at both nuclear (allozyme) and mitochondrial loci and found evidence of substantial gene flow over very large distances (up to 1599 km). Thus, some juvenile magpies may disperse much greater distances than was previously thought. For mtDNA, geographic and genetic distance were strongly correlated, consistent with a pattern of isolation by distance. Therefore, although female gene flow is substantial it is apparently geographically restricted over large distances, in approximately a stepping-stone fashion. We conclude that a strong relationship between gene flow and geographic distance can develop even over large distances if populations have experienced no major historical disturbances to gene flow.     

Mechanisms of long-distance seed dispersal

Growing recognition of the importance of long-distance dispersal (LDD) of plant seeds for various ecological and evolutionary processes has led to an upsurge of research into the mechanisms underlying LDD. We summarize these findings by formulating six generalizations stating that LDD is generally more common in open terrestrial landscapes, and is typically driven by large and migratory animals, extreme meteorological phenomena, ocean currents and human transportation, each transporting a variety of seed morphologies. LDD is often associated with unusual behavior of the standard vector inferred from plant dispersal morphology, or mediated by nonstandard vectors. To advance our understanding of LDD, we advocate a vector-based research approach that identifies the significant LDD vectors and quantifies how environmental conditions modify their actions.     

The establishment of plants following long-distance dispersal

Long-distance dispersal (LDD) beyond the range of a species is an important driver of ecological and evolutionary patterns, but insufficient attention has been given to postdispersal establishment. In this review, we summarize current knowledge of the post-LDD establishment phase in plant colonization, identify six key determinants of establishment success, develop a general quantitative framework for post-LDD establishment, and address the major challenges and opportunities in future research. These include improving detection and understanding of LDD using novel approaches, investigating mechanisms determining post-LDD establishment success using mechanistic modeling and inference, and comparison of establishment between past and present. By addressing current knowledge gaps, we aim to further our understanding of how LDD affects plant distributions, and the long-term consequences of LDD events.     

A case of visceral leishmaniosis in a gray wolf (Canis lupus) from Croatia

The southern habitats of Croatia's gray wolf (Canis lupus) population are found in central and southern parts of Dalmatia. This region is recognized as an endemic region for canine visceral leishmaniosis, caused by Leishmania infantum. In November 2003, a 4-yr-old male gray wolf was found dead in the northwestern border of this endemic region. Pathologic and parasitologic analysis, confirmed by polymerase chain reaction, indicated that lesions associated with infection by Leishmania infantum are, in this case, typical for visceral leshmaniosis commonly described in dogs. Review of the literature suggests that this is the first reported case of gray wolf death due to lesions caused by L. infantum.     

Microbial modification of host long-distance dispersal capacity

Background  

Dispersal plays a key role in shaping biological and ecological processes such as the distribution of spatially-structured populations or the pace and scale of invasion. Here we have studied the relationship between long-distance dispersal behaviour of a pest-controlling money spider,Erigone atra, and the distribution of maternally acquired endosymbionts within the wider meta-population. This spider persists in heterogeneous environments because of its ability to recolonise areas through active long-distance airborne dispersal using silk as a sail, in a process termed 'ballooning'.     

Predictors of long-distance dispersal in the Siberian flying squirrel

During dispersal the distances moved differ between individuals. The evolutionary causes of dispersal rate are much studied, for example, it is observed that dispersal is often a condition- and phenotype-dependent strategy. However, more empirical information is needed on factors affecting the dispersal distance. We study factors behind dispersal distance in the juvenile Siberian flying squirrel. The longer dispersing individuals abandoned natal site earlier in the season and were larger, perhaps being born earlier, than shorter dispersing individuals. These patterns did not hold between same-sex siblings, indicating that the early long-distance dispersal was more a between than a within-litter related phenomenon. Our results indicate differences between litters that are related to dispersal strategies of individuals. In flying squirrels, long-distance dispersal is not merely a secondary effect of short-distance dispersal. Instead, the distribution of dispersal distance is affected by factors enhancing long-distance dispersal.     

Variation in chronic radiation exposure does not drive life history divergence among Daphnia populations across the Chernobyl Exclusion Zone

Ionizing radiation is a mutagen with known negative impacts on individual fitness. However, much less is known about how these individual fitness effects translate into population‐level variation in natural environments that have experienced varying levels of radiation exposure. In this study, we sampled genotypes of the freshwater crustacean, Daphnia pulex, from the eight inhabited lakes across the Chernobyl Exclusion Zone (CEZ). Each lake has experienced very different levels of chronic radiation exposure since a nuclear power reactor exploded there over thirty years ago. The sampled Daphnia genotypes represent genetic snapshots of current populations and allowed us to examine fitness‐related traits under controlled laboratory conditions at UK background dose rates. We found that whilst there was variation in survival and schedules of reproduction among populations, there was no compelling evidence that this was driven by variation in exposure to radiation. Previous studies have shown that controlled exposure to radiation at dose rates included in the range measured in the current study reduce survival, or fecundity, or both. One limitation of this study is the lack of available sites at high dose rates, and future work could test life history variation in various organisms at other high radiation areas. Our results are nevertheless consistent with the idea that other ecological factors, for example competition, predation or parasitism, are likely to play a much bigger role in driving variation among populations than exposure to the high radiation dose rates found in the CEZ. These findings clearly demonstrate that it is important to examine the potential negative effects of radiation across wild populations that are subject to many and varied selection pressures as a result of complex ecological interactions.     

Genetic traces of recent long-distance dispersal in a predominantly self-recruiting coral

Background

Understanding of the magnitude and direction of the exchange of individuals among geographically separated subpopulations that comprise a metapopulation (connectivity) can lead to an improved ability to forecast how fast coral reef organisms are likely to recover from disturbance events that cause extensive mortality. Reef corals that brood their larvae internally and release mature larvae are believed to show little exchange of larvae over ecological times scales and are therefore expected to recover extremely slowly from large-scale perturbations.

Methodology/Principal Findings

Using analysis of ten DNA microsatellite loci, we show that although Great Barrier Reef (GBR) populations of the brooding coral, Seriatopora hystrix, are mostly self-seeded and some populations are highly isolated, a considerable amount of sexual larvae (up to ∼4%) has been exchanged among several reefs 10 s to 100 s km apart over the past few generations. Our results further indicate that S. hystrix is capable of producing asexual propagules with similar long-distance dispersal abilities (∼1.4% of the sampled colonies had a multilocus genotype that also occurred at another sampling location), which may aid in recovery from environmental disturbances.

Conclusions/Significance

Patterns of connectivity in this and probably other GBR corals are complex and need to be resolved in greater detail through genetic characterisation of different cohorts and linkage of genetic data with fine-scale hydrodynamic models.     

The importance of long-distance dispersal in biodiversity conservation

Dispersal is universally considered important for biodiversity conservation. However, the significance of long‐ as opposed to short‐distance dispersal is insufficiently recognized in the conservation context. Long‐distance dispersal (LDD) events, although typically rare, are crucial to population spread and to maintenance of genetic connectivity. The main threats to global biodiversity involve excessive LDD of elements alien to ecosystems and insufficient dispersal of native species, for example, because of habitat fragmentation. In this paper, we attempt to bridge the gap in the treatment of LDD by reviewing the conservation issues for which LDD is most important. We then demonstrate how taking LDD into consideration can improve conservation management decisions.     

Unexplained patterns of grey wolf Canis lupus natal dispersal

Natal dispersal (movement from the site of birth to the site of reproduction) is a pervasive but highly varied characteristic of life forms. Thus, understanding it in any species informs many aspects of biology, but studying it in most species is difficult. In the grey wolf Canis lupus, natal dispersal has been well studied. Maturing members of both sexes generally leave their natal packs, pair with opposite-sex dispersers from other packs, near or far, select a territory, and produce their own offspring. However, three movement patterns of some natal-dispersing wolves remain unexplained: 1) long-distance dispersal when potential mates seem nearby, 2) round-trip travels from their natal packs for varying periods and distances, also called extraterritorial movements, and often not resulting in pairing, and 3) coincidental dispersal by individual wolves from a given area in the same basic directions and over the same long distances. This perspective article documents and discusses these unexplained dispersal patterns, suggests possible explanations, and calls for additional research to understand them more clearly.     

Retention time variability as a mechanism for animal mediated long-distance dispersal

Long-distance dispersal (LDD) events, although rare for most plant species, can strongly influence population and community dynamics. Animals function as a key biotic vector of seeds and thus, a mechanistic and quantitative understanding of how individual animal behaviors scale to dispersal patterns at different spatial scales is a question of critical importance from both basic and applied perspectives. Using a diffusion-theory based analytical approach for a wide range of animal movement and seed transportation patterns, we show that the scale (a measure of local dispersal) of the seed dispersal kernel increases with the organisms' rate of movement and mean seed retention time. We reveal that variations in seed retention time is a key determinant of various measures of LDD such as kurtosis (or shape) of the kernel, thinkness of tails and the absolute number of seeds falling beyond a threshold distance. Using empirical data sets of frugivores, we illustrate the importance of variability in retention times for predicting the key disperser species that influence LDD. Our study makes testable predictions linking animal movement behaviors and gut retention times to dispersal patterns and, more generally, highlights the potential importance of animal behavioral variability for the LDD of seeds.     

A case of recent long-distance dispersal in the Piriqueta caroliniana complex

We investigated restriction fragment length polymorphism (RFLP) variation in the chloroplast DNA regions trnS and trnC in 53 populations of the herbaceous perennial Piriqueta caroliniana complex, encompassing its known North American range. The goals of this study were to expand the geographic range of a previous study and to determine the origin of an apparently anomalous population, which possessed a phenotype that was incongruous with other populations in the region. The phylogeography of these populations was investigated with nested clade analysis of a one-step network phylogeny that was based on the RFLP variation of the chloroplast genome. We found evidence of restricted gene flow and past fragmentation, which is consistent with a previous study on the phylogeography of this species complex. The morphological and genetic profile of the one anomalous population indicates that it recently originated from south Florida. Given the urban location of this geographically disjunct population, it is probable that this is an example of a recent human-mediated long-distance dispersal event.     

Population genetics strategies to characterize long-distance dispersal of insects

Population genetics strategies offer an alternative and powerful approach for obtaining information about long-distance movement, and have been widely used for examining patterns and magnitude of insect dispersal over geographic and temporal scales. Such strategies are based on the principle that genetic divergence between local populations reflects the interplay between genetic drift and gene flow, and thus can function as an indicator of dispersal capacity. Relatively new approaches for inferring population history are widely applicable for documenting introduction routes of invasive or quarantine species. These approaches are based on genetic variability calculated from changes in gene frequency of subpopulations, measured using molecular genetic markers. Inferences from population genetics can supplement and corroborate conventional observational approaches for characterizing insect dispersal and have provided important clues to many questions raised in the field of behavior and ecology of insects. Here, we summarize our work on the boll weevil as a case study to illustrate the kinds of information on dispersal capacity and dispersal patterns that can be obtained from population genetics techniques that would be difficult or impossible to acquire in other ways. Then we provide examples of how the molecular markers and population genetics tools have been applied to answer immediate questions of relevance to eradication program managers. Though the latter are idiosyncratic to this particular pest, they demonstrate the kinds and range of problems that can be addressed in other systems through application of population genetics strategies.