優雅角鴞分子生態研究

Molecular Ecology of Elegant Scops Owl (Otus elegans)

許育誠(Yu-Cheng Hsu)

指導教授 ： 林曜松

共同指導教授 ： 劉小如(Lucia Liu Severinghaus)

國立臺灣大學/生命科學院/生態學與演化生物學研究所/博士(2005年)

https://doi.org/10.6342/NTU.2005.01853

摘要

本論文的主要內容，在於利用分子遺傳標記，探討優雅角鴞（Elegant Scops Owl, Otus elegans）的遺傳配對系統和族群遺傳結構。第一章首先以優雅角鴞的蘭嶼亞種（即蘭嶼角鴞O. e. botelensis）為對象，開發出具有多型性的微隨體DNA（microsatellite）。微隨體為基因組中一段以數個鹼基為單元重複出現的DNA片段。其具高度多型性、雙系遺傳且符合孟德爾遺傳定律、易於判讀等特性，使其在近年來大量被應用在親子鑑定、親屬關係與族群遺傳結構等相關研究上。 藉由強化（enrichment）的分子選殖技術，共篩選出18組具多型性的微隨體基因座，平均每基因座中具有10個對偶基因、實測雜合度（observed heterozygosity）為0.771。為測試這18組基因座在其他鴟鴞科鳥類的適用性，另外又針對四種鴟鴞科鳥類進行多型性測試。結果顯示受試物種與蘭嶼角鴞的親源關係越遠，這些微隨體基因座的適用性和多型性就越低。
第二章的研究即以12組前述所篩選出的微衛星基因座作為遺傳標記，進行蘭嶼角鴞的親子鑑定，其目的在瞭解蘭嶼角鴞在高繁殖密度與頻繁的偶外交配（extra-pair copulation）中，是否有子代是經由偶外受精（extra-pair fertilization）所產生。比對來自108個家庭、共200隻幼鳥的基因型，一共只發現來自二個家庭的三隻幼鳥，其基因型和餵養牠們的親鳥不相符。配合野外調查的記錄，並比對所有成鳥的微衛星基因型資料，確認其中一巢的一隻幼鳥是母鳥和該樹洞的前擁有者發生偶外受精所產生。另一巢的二隻庶出幼鳥，則是來自鄰近樹洞的繁殖鳥。這些結果顯示：儘管繁殖密度高並有頻繁的偶外交配，蘭嶼角鴞的遺傳配對系統仍屬於一夫一妻制，故野外調查的繁殖資料，已可充分反應個體實際的繁殖成功率。
第三章的研究範圍則擴展至優雅角鴞大部分的分佈區，研究目的在於探討在琉球群島和蘭嶼各島上，優雅角鴞各島嶼族群的遺傳多樣性和親源地理。本章主要以粒線體DNA的序列作為遺傳標記，並加入13組微衛星基因座的資料進行分析。分析這些分子資料發現優雅角鴞在北部島嶼內的遺傳多樣性較高、偏遠島嶼內的族群遺傳多性較低。所有樣本可以分成南北二大系群，顯示南北二族群曾經過很長期的隔離。大部分島嶼族群間有明顯的族群分化，以MDIV軟體估算相鄰島嶼族群間的分化時間和基因交流程度，發現此二因子對於造成族群分化的影響程度在各島之間的重要性各不相同。以FLUCTUATE軟體估算族群成長率，顯示自最近一次冰期結束迄今，在南、北琉球的角鴞族群量都呈現成長的趨勢，推測可能是因為冰期結束後，這些地區降雨量增加，造成適合優雅角鴞棲息的森林增加所致。

關鍵字

優雅角鴞 ； 蘭嶼角鴞 ； 偶外受精 ； 族群遺傳

並列摘要

Chapter 1
Isolation and characterization of microsatellite DNA markers from the Lanyu Scops Owl (Otus elegans botelensis) and their cross-species application in four species of strigidae

Abstract
From a genomic library enriched for GATA/CTAT and GAAA/CTTT repeats, eighteen polymorphic microsatellite markers were developed for the Lanyu Scops Owl (Otus elegans botelensis). Polymorphism of these loci was evaluated in a sample of 100 adult individuals of unknown relationship. The allele numbers of each locus were from 5 to 28 and the observed heterozygosity of each locus ranges from 0.59 to 0.95. All loci conformed to Hardy-Weinberg expectations. In addition, we cross-species tested these microsatellite primer pairs on four other species of owls (O. lettia, O. spilocephalus, O. sunia, and Ninox scutulata). Results showed that the degree of polymorphism decreased with increasing phylogenetic distance to O. elegans. Most loci (12, 15, and 18) were polymorphic in the three Otus owls but only five loci were polymorphic in N. scutulata. These microsatellites should be very useful genetic markers in studying the mating system, population genetics, and conservation genetics of other little studied Old World Otus owls.

Chapter 2
Genetic mating system of Lanyu Scops Owls (Otus elegans botelensis)
Abstract
The genetic mating system is known for only a few species of owls. Most of them are genetically monogamous. The Lanyu Scops Owl (Otus elegans botelensis) breeds in high density in the forests of Lanyu (Orchid Island), southeast of Taiwan. Because extra-pair copulations (EPCs) have frequently been observed, we suspected a high degree of extra-pair fertilizations (EPFs). Using a set of 12 microsatellite loci, we assigned the parentage of 200 offspring from 108 families collected between 1999 and 2004. Parentage analysis revealed only two cases of parentage mismatch among 108 broods. The first case was most likely a case of brood usurpation, which would be the first case reported in the Strigidae. The second case was an EPF resulting in one offspring. Our study found that Lanyu Scops Owls are essentially genetically monogamous. Therefore, field monitoring data has provided reliable estimates of the lifetime reproductive success of this species.

Chapter 3
Phylogeography of the Elegant Scops Owl (Otus elegans) on East Asian Islands
Abstract
The phylogeography of birds reflects the influence of both the geographic history of the area and the dispersal ability of the species. Islands have proven to be ideal sites for such studies due to the nature of their isolation. Elegant Scops Owl (Otus elegans) is a small owl found only in the forests of some East Asian islands. We used complete mitochondrial DNA (mtDNA) cytochrome b and NADH dehydrogenase subunit 6 genes (1665 bp in total) and 13 polymorphic microsatellite loci to analyze the population genetic structure of this owl on 10 islands in the Ryukyu Archipelago, Japan and on Lanyu (Orchid Island), Taiwan, in an attempt to infer the genetic diversity, population differentiation, gene flow, and demographic history of this species. Based on blood samples from 164 owls, we found higher genetic diversity on more northerly islands than on more southerly islands. No mtDNA variations were detected in remote island populations (Minami Daito and Lanyu). Pairwise Fst values between islands showed population differentiation on most islands. A deep divergence between northern and southern Ryukyu populations indicated a long period of north-south isolation. Bayesian estimation using the MDIV program revealed that the divergent time and the rate of gene flow differed among island pairs. Maximum likelihood estimates using MIGRATE found that the gene flow between islands was low and directionally asymmetrical, with a more northerly migration than the reverse. Maximum likelihood analysis using FLUCTUATE revealed that Ryukyu owl population sizes have been increasing since the last glaciation, but the rate of increase are lower in the north than in the south.

並列關鍵字

Otus elegans ； Lanyu Scops Owl ； extra-pair fertilization ； population genetics

參考文獻

Wu T-Y (2001) Nest-site selection of Lanyu Scops Owl (Otus elegans botelensis). Master's thesis, National Taiwan University, Taipei. (in Chinese).

Chapter 1

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