台灣產溪狡蛛(跑蛛科，狡蛛屬)之族群遺傳及親緣地理關係之探討

Study on population genetic structure and phylogeography of Dolomedes raptor (Araneae, Pisauridae) in Taiwan

羅英元(Ying-Yuan Luo)

指導教授 ： 陳世煌

國立臺灣師範大學/理學院/生命科學研究所/碩士(2006年)

摘要

地理隔離造成生物族群間的分化，一直是近年來生物學上亟欲探討的問題之一。台灣的中央山脈地形崎嶇且縱貫台灣，加上河流東西走向的切割，對於台灣許多物種而言都是天然的地理屏障。由於台灣的蜘蛛學研究處於剛起步階段，對於蜘蛛是否會因台灣地形的阻隔而有族群分化的現象，仍須進一步探討。溪狡蛛（Dolomedes raptor B?senberg & Strand, 1906）為一中大型蜘蛛，廣泛分布於台灣中低海拔各地，平時不結網，棲息環境侷限於溪流、溪澗等有流水的環境。一般認為許多昆蟲和蜘蛛具有良好的擴散能力而較不易被地形所阻隔，但溪狡蛛由於生活環境侷限、加上沒有牽絲空飄的行為，種種特性顯示其擴散能力不佳，因此可能受到台灣地形隔離而影響族群間的交流，正好適合作為探討族群遺傳以及親緣地理的材料。
本研究利用粒線體中cytochrome oxidase subunit I（COI）部分序列來進行族群遺傳結構之探討，共分析了21個樣點、153隻個體，取得序列長度617bp，包括34個變異位點、23個基因型。由AMOVA分析得知台灣地區溪狡蛛的遺傳結構在族群間有顯著的差異，由neighbor-joining以及maximum parsimony親緣關係樹型圖皆顯示可將台灣地區溪狡蛛分為北部、中南部和東部三大系群，除了中部和南部、中部和中北部族群間的遺傳分化指數較低（FST = 0.10299~ 0.26042）之外其餘族群間遺傳分化指數都偏高，特別是東部與其他族群間的遺傳分化指數皆大於0.79，顯示台灣地區溪狡蛛族群間基因交流受到山脈和水系的阻隔而有類似台灣一些初級性淡水魚「區域性分化」的現象，表示溪狡蛛的分化模式和人面蜘蛛這類結網性、具有良好擴散能力的物種截然不同。中部和南部族群間的基因交流順暢，推測和中南部地勢平坦、水系複雜以及人工渠道的開鑿有關。
由minimum spanning network顯示東部族群是由北部擴散而來，且遺傳多樣性較低，推測過去曾受到強烈瓶頸效應和創始者效應的影響。
溪狡蛛大多分布在中央山脈以西且和生活習性相似的褐腹狡蛛少有共域棲息的現象，推測可能因為溪狡蛛較不適應東部湍急溪流、以及擴散到東部不易等因素所造成。溪狡蛛已有顯著遺傳結構的分化，因此棲地的保存仍為當務之急。

關鍵字

親緣地理 ； 族群遺傳結構 ； 基因交流 ； 族群分化 ； 溪狡蛛

並列摘要

The Central Mountain Range (CMR) and rivers in Taiwan form a natural geographic barrier for many organisms. However, study of Araneae is insufficient in Taiwan. We would investigate the differentiation of spiders that were resulted from geographic barriers in Taiwan. Generally we regard that many spiders and insects possess strongly dispersal ability. However, Dolomedes raptor may have weak dispersal ability resulting from their habitats restricted in the streams or creeks, without the ballooning behavior, and their distribution limited at low or medium elevations. Therefore, the gene flow between populations of D. raptor may be prohibited by the geographic barriers in Taiwan. Therefore, I chose D. raptor to investigate the population genetics and phylogeography of Taiwan.
The partial sequence of mtDNA cytochrome oxidase subunitⅠ(COI) was used as a genetic marker for these purpose in this study. Totally, 153 specimens were obtained from 21 localities in Taiwan. The length of sequenced COI gene was 617bp, including 34 polymorphism sites and 23 haplotypes. Analysis of AMOVA indicates that genetic structures are different significantly among populations. Phylogenetic trees generated from both the NJ and MP methods showed that D. raptor in Taiwan could be grouped into three major lineages, namely northern, eastern and central-southern lineages. All the FST values are high between populations, except for those between the central and southern, the central and central-northern populations (FST =0.10299~0.26042). Additionally, the east population has the highest FST when compare to any other populations. It indicates populations of D. raptor in Taiwan exhibited genetic differentiation that are resulted from both isolations by the mountains and the lands between basins. The differentiation model of D. raptor is similar to that of primary freshwater fishes, but not Nephila pilipes, an orb-web spider, with strongly dispersal ability. Moreover, the gene flow between south and contral populations was not isolated. It might be resulted from the southern and central parts of Taiwan that have a smooth topology, with complex drainage systems for agriculture and are frequently irrigated by the people.
Minimum spanning network showed that the eastern population was derived from the northern population. However, the genetic diversity in eastern population showed low indicates that it might have undergone the strong founder event and the bottleneck effect.
Most D. raptor populations are distributed in the western Taiwan, and had less sympatric habitats with D. mizhoanus. I consider the phenomenon was due to the microhabitat selection and the strongly geographical barriers for D. raptor to move in the eastern Taiwan.

並列關鍵字

phylogeography ； population genetic structure ； gene flow ； population differentiation ； Dolomedes raptor

參考文獻

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