抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

The Theory of Island Biogeography

I. the origin of species by means of natural selection

We redescribe the only previously known species of Myrsidea from bulbuls, M. pycnonoti Eichler. Sixteen new species are described; they and their type hosts are: M. phillipsi ex Pycnonotus goiavier goiavier (Scopoli), M. gieferi ex P. goiavier suluensis Mearns, M. kulpai ex P. flavescens Blyth, M. finlaysoni ex P. finlaysoni Strickland, M. kathleenae ex P. cafer (L.), M. warwicki ex Ixos philippinus (J. R. Forster), M. mcclurei ex Microscelis amaurotis (Temminck), M. zeylanici ex P. zeylanicus (Gmelin), M. plumosi ex P. plumosus Blyth, M. eutiloti ex P. eutilotus (Jardine and Selby), M. adamsae ex P. urostictus (Salvadori), M. ochracei ex Criniger ochraceus F. Moore, M. borbonici ex Hypsipetes borbonicus (J. R. Forster), M. johnsoni ex P. atriceps (Temminck), M. palmai ex C. ochraceus, and M. claytoni ex P. eutilotus. A key is provided for the identification of these 17 species.

A new species

What is ecological speciation

The seasonal marine feeding pattern of sea trout was studied from March to December 2001 in two large fjords situated at latitudes 69°N and 66°N in the northern part of Norway. Despite low sea temperatures and high salinity, sea running trout were caught during all sampling occasions in both fjords. The trout had fed extensively on marine crustaceans (shrimps, amphipods, and krill) and polychaetes during early and late winter, and had a stable or increasing condition factor during this period. In summer and autumn, the trout fed predominantly on fish, mainly juvenile herring. Food consumption rates were lowest during late autumn and early winter (October-December) in both fjords, while trout in the southernmost fjord had the highest consumption rates from April to August and trout in the northernmost fjord from May to September. These patterns in both fjords matched the seasonal variations in condition factor and relative lipid content of the fish during the same periods. The marine winter migration of these northern sea trout populations appears to be a feeding migration in which the fish maintain or increase their body condition, representing a previously undocumented alternative to the more common life history strategy of over-wintering and starvation in freshwater at the northern distribution of this species.

Seasonal marine feeding and body condition of sea trout ( Salmo trutta ) at its northern distribution

The relationship between infection with the food-transmitted parasites Diphyllobothrium dendriticum, D. ditremum (Cestoda) and Cystidicola farionis (Nematoda) and prey selection was studied in individual Arctic charr from Lake Takvatn, northern Norway. There was no correlation between parasites transmitted throughout prey organisms from benthic habitats (amphipods) and pelagic habitats (copepods). A strong relationship between infection with a parasite species and the corresponding intermediate host from the stomach content of individual charr, indicated an individual feeding specialization. Independent of size, charr specialized on the intermediate hosts of all three parasite species. Some charr maintained this specialization on specific prey items throughout the winter period. These parasite species are considered to be useful indicators of past prey selection. ? 1996 The Fisheries Society of the British Isles

Parasites as indicators of individual feeding specialization in Arctic charr during winter in northern Norway

Significant genetic differences (FST = 0·032) were found between littoral and profundal morphs of Arctic charr Salvelinus alpinus from Fjellfrosvatn, northern Norway, using microsatellite DNA analysis. The morphs had strong reproductive isolation in time and space; the segregation of a separate profundal morph is rare in postglacial lakes.

Genetic differences between two sympatric morphs of Arctic charr confirmed by microsatellite DNA

Morphological divergence was evident among three sympatric morphs of Arctic charr (Salvelinus alpinus (L.)) that are ecologically diverged along the shallow-, deep-water resource axis in a subarctic postglacial lake (Norway). The two deep-water (profundal) spawning morphs, a benthivore (PB-morph) and a piscivore (PP-morph), have evolved under identical abiotic conditions with constant low light and temperature levels in their deep-water habitat, and were morphologically most similar. However, they differed in important head traits (e.g., eye and mouth size) related to their different diet specializations. The small-sized PB-morph had a paedomorphic appearance with a blunt head shape, large eyes, and a deep body shape adapted to their profundal lifestyle feeding on submerged benthos from soft, deep-water sediments. The PP-morph had a robust head, large mouth with numerous teeth, and an elongated body shape strongly related to their piscivorous behavior. The littoral spawning omnivore morph (LO-morph) predominantly utilizes the shallow benthic-pelagic habitat and food resources. Compared to the deep-water morphs, the LO-morph had smaller head relative to body size. The LO-morph exhibited traits typical for both shallow-water benthic feeding (e.g., large body depths and small eyes) and planktivorous feeding in the pelagic habitat (e.g., streamlined body shape and small mouth). The development of morphological differences within the same deep-water habitat for the PB- and PP-morphs highlights the potential of biotic factors and ecological interactions to promote further divergence in the evolution of polymorphism in a tentative incipient speciation process. The diversity of deep-water charr in this study represents a novelty in the Arctic charr polymorphism as a truly deep-water piscivore morph has to our knowledge not been described elsewhere.

/pdf/morphological-divergence-between-three-arctic-charr-morphs-4nvs4g5r47.pdf

Morphological divergence between three Arctic charr morphs - the significance of the deep-water environment.

Hypothesis: The opportunity for inter-individual niche differences in contrasting resource environments can induce divergent natural selection in trophic morphology within single gene pools. Organisms: Arctic charr (Salvelinus alpinus) caught in the littoral and pelagic habitats of two neighbouring sub-arctic lakes. Field sites: Two post-glacial lakes (Fjellfrøsvatn and Lille Rostavatn, North Norway) of similar size and physical structures, but with different fish diversities (two and six species, respectively). Methods: Analysis and comparison of trophic niche (habitat and diet usage) and trophic morphology (body form and head structure) data from individual fish. Only immature charr 19–25 cm long were used to reduce the effects of allometric growth and secondary sex traits. Conclusions: The utilization of multiple resource types has facilitated incipient steps towards the evolution of polymorphism in one lake, but not in the other. In Fjellfrøsvatn, individual specializations in benthivore and planktivore diet niches are correlated with inter-individual morphological differentiation. In contrast, the Arctic charr in Lille Rostavatn were restricted to zooplanktivory, and distinct morphological diversification was absent. We conclude that the two lakes have dissimilar opportunities for individual niche specialization and evolution of polymorphism.

http://www.evolutionary-ecology.com/issues/v09n06/kkar2172.pdf

Rune Knudsen

Papers

Seasonal marine feeding and body condition of sea trout ( Salmo trutta ) at its northern distribution

Parasites as indicators of individual feeding specialization in Arctic charr during winter in northern Norway

Genetic differences between two sympatric morphs of Arctic charr confirmed by microsatellite DNA

Morphological divergence between three Arctic charr morphs - the significance of the deep-water environment.

Contrasting niche-based variation in trophic morphology within Arctic charr populations