以微衛星體基因座及主要組織相容性複合體之異型合子度探討青背山雀之配對模式

Abstract

摘要 雌鳥可藉由雄鳥的表型為依據，選擇與能提供直接利益(子代較好的照顧及資源)、或間接利益(增加子代遺傳組成)之雄鳥配對以最大化本身的適應性。 Brown提出異型合子假說後，其衍生出的異型合子優勢假說及遺傳相容性假說提供檢測配偶選擇背後的遺傳機制之方向。本實驗以台灣中部青背山雀為例、使用十八個為衛星體基因座及主要組織相容複合體第一型為遺傳標記，以此兩種假說探討遺傳機制如何影響配偶選擇。結果顯示具有較高微衛星體基因座異型合子度及與雌性較低遺傳相似度的雄性有較高獲得繁殖的機會；而具有較高異型合子度之雌鳥較不容易獲得繁殖機會，並且當與第一型主要組織相容性複合體較不相似的雄鳥配對時，雌鳥會尋求偶外配對。本實驗說明雄鳥的多種遺傳因子及雌鳥本身的遺傳組成皆會影響配偶選擇。

Abstract By assessing the phenotypic traits of males, females may prefer to mate with males that provide direct benefits (e.g. high quality of parental care or better territory), as well as indirect or genetic benefits which maximize offspring’s viability and sexual attractiveness. Here, I used 18 microsatellite loci and MHC class I to test whether the green-backed tit mated randomly with individuals with higher genome-wide or MHC dissimilarity at central Taiwan. I also examined whether individuals with higher heterozygosity enjoyed the advantage to becoming breeders. My results suggested that more heterozygous males had better chances to breed, and tits mated nonrandomly with genetically dissimilar breeders. Our results also supported the optimal MHC-heterozygosity hypothesis in that, compared to non-breeders, female breeders had lower MHC-heterozygosity and females engaged extra-pair fertilization when mated with males sharing fewer MHC alleles. Taken together, I demonstrated both genetic heterozygote advantage and genetic compatibility effects at neutral as well as functional loci in the green-backed tits.