間歇性遷入與染色體倒位共同影響尼泊爾埋葬蟲種內遺傳多樣性及環境適應

Abstract

生物如何適應環境是研究生物多樣性形成的核心問題之一。適應性遺傳變異來源可以是新形成的突變或是既有的遺傳變異（standing genetic variation），我們對於兩者的重要性及他們如何共同作用的理解仍然不足。同時，我們也需要更多的實證研究來釐清生物如何在基因流下達成地區性適應（local adaptation）。了解這兩個生物適應的問題能增加我們對生物多樣性形成的基本原理。本研究我們以在臺灣表現出生殖光週期的地區性適應現象的尼泊爾埋葬蟲為對象，透過比較全年繁殖及季節性繁殖個體間的遺傳差異，我們發現不同族群透過不同的遺傳機制決定生殖光週期的表現型。而重建親緣關係樹的結果顯示，臺灣現今的尼泊爾埋葬蟲族群是由多次的遷入事件所構成。族群遺傳結構分析的結果則顯示染色體倒位幫助了維持族群間的遺傳差異。我們認為多次遷入與染色體倒位共同導致了多種遺傳調控機制的現象，並且也使得新突變與既有遺傳變異共同幫助了基因流下的本地適應。本篇研究展示了複雜的族群形成歷史與染色體倒位在地區性適應中扮演的角色，為生物多樣性的起源機制提供了新的觀點。

How organisms adapt to their environment is one of the core questions in studying the formation of biological diversity. The source of adaptive genetic variation can either be newly formed mutations or standing genetic variations. Our understanding of the importance of these two and how they interact is still insufficient. Simultaneously, we also need more empirical research to clarify how organisms achieve local adaptation under gene flow. Understanding these two questions about biological adaptation can enhance our basic principles of the formation of biological diversity. In this study, we focused on the Nicrophorus nepalensis, which exhibits locally adapted reproductive photoperiodism in Taiwan. By comparing the genetic differences between individuals who reproduce throughout the year and those who reproduce seasonally, we found that different populations regulate the phenotype of reproductive photoperiodism through different genetic mechanisms. The results of reconstructing the phylogenetic tree show that the current N. nepalensis populations in Taiwan are composed of multiple immigration events. The results of population genetic structure analysis reveal that chromosomal inversion helps to maintain genetic differences between populations. We believe that multiple migrations and chromosomal inversions have collectively led to the phenomenon of multiple genetic regulatory mechanisms. Additionally, they have allowed new mutations and standing genetic variations to jointly assist in local adaptation under gene flow. This research demonstrates the roles of complex population formation history and chromosomal inversion in local adaptation, providing new perspectives on the mechanisms of origin of biological diversity.