東北大学 生物多様性進化分野 河田研究室

日時: 11月24日(火) 14:00 - 16:00 場所: 地学・生物共通講義室 (青葉山キャンパス)

14:00 - 15:00
Speaker: Jun Kitano (National Institute of Genetics)
Title: Genetic basis for colonization of new niches in sticklebacks

Abstract: Our research goal is to identify molecular changes underlying naturally occurring phenotypic variation and speciation and understand how such variations arise and spread within natural populations. In the seminar, I will present our recent studies on variation in the ability to colonize freshwater environments. Colonization of empty niches can trigger adaptive radiation. A remarkable example can be found in stickleback fishes. Marine ancestors have colonized newly formed freshwater environments and diversified. Not all lineages, however, have seized these ecological opportunities: all Japanese freshwater populations are derived from the Pacific Ocean lineage of Gasterosteus aculeatus rather than the Japan Sea lineage (G. nipponicus). Freshwater prey items usually have lower amounts of DHA, an essential polyunsaturated fatty acid, than freshwater prey items. We found that the two lineages differ in the ability to synthesize DHA. We also found copy number variation of a gene encoding an enzyme involved in DHA synthesis. Transgenic experiments also showed that copy number variation of this gene may explain some of the variation in the ability to colonize freshwater environments.

15:00 - 16:00
Speaker: Andreas Wallberg (Uppsala University, Sweden)
Title: The evolutionary history of the honeybee Apis mellifera reconstructed from a global survey of genome variation

Abstract: The European honeybee Apis mellifera is essential to ecology and agriculture due to its role as a pollinator and adapted to a wide range of environmental conditions. We have used population-scale genome sequencing to uncover population history, the genetic basis of local adaptation and the causes and consequences of high rates of recombination in this species. We sequenced the full genomes of 140 honeybees from a worldwide sample of 14 populations, identifying over 8.3 million SNPs. Levels of genetic variation are high, especially among African populations and show evidence of historical fluctuations correlated with past oscillations in the earth’s climate. We identify many genetic variants to diverge between honeybee populations, indicative of selection. These are distributed across thousands of genes, but enriched for developmental, worker-biased, immune and sperm mobility genes and form the basis for understanding the genetics of adaptation to pathogens and climate in honeybees. Recombination is crucial for sexual reproduction and has pervasive effects on genetic diversity. Honeybees has among the highest eukaryotic recombination rates. The reasons for these rates and their effects on genome evolution are unknown. We used our dataset to build a map of recombination from patterns of linkage disequilibrium. We find that recombination determines levels of genetic variation in honeybees. The site frequency spectrum is highly skewed towards the fixation of GC alleles, indicative of a major impact of GC-biased gene conversion. At such high rates, gBGC interferes with selection, resulting in fixation of deleterious alleles and altered nucleotide composition across the genome. Lastly, I will provide an overview of the honeybee genomics project at Uppsala University, including some ongoing projects about ancestry and selection mapping.


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Last-modified: 2015-11-13 (金) 16:44:11 (735d)