從埃及斑蚊成蟲腹部背板白鱗、成蟲表皮正烷類、隨機增幅多型性基因組DNA探討在台灣之族群間差異

Abstract

依據埃及斑蚊成蟲腹部背板白色鱗片的分佈情形可將其區分為三型：1.模式型（the type form），為 Ae. aegypti aegypti之一型，廣佈於全球熱帶、亞熱帶地區，其各腹節除了基部有白色鱗片帶外，白色鱗片在各節往後延伸的情形僅發生於第一腹節上，在CKM系統上被區分為CKM1；2.淡色型（the pale form），為 Ae. aegypti aegypti之另一型，腹節背板白色鱗片往後延伸的情形可以連續發生於各腹節上，屬於CKM2-7的等級；3.深色型（the dark form），為 Ae. aegypti formosus,，分佈於非洲南部撒哈拉地區以及印度洋島嶼，各腹節完全沒有往後延伸的白色鱗片，屬於CKM0的等級。以RAPD-PCR的方法隨機擴增CKM1-7品系之基因組 DNA，並分析其間的差異後發現，模式型與淡色型雖然具有類似之生態席位，但在RAPD的形質上可以明顯的區分開來。分析CKM1-7之埃及斑蚊不同品系之正烷類表皮碳氫化合物的結果來看，在定性上之組成皆為n-C18至n-C36共19種化合物，但成蟲體表白色鱗片的分佈與數量造成化合物定量上的差異，n-C18至n-C27之平均含量會隨著CKM值的增加而變多，而n-C29至n-C36會變少。 台灣西南部和東南部沿海共9個埃及斑蚊族群的個體屬於模式型與淡色型混棲的形式，未發現深色型的個體。並檢視其白鱗分佈的情形，發現雄性成蟲其CKM值的變化程度較雌性成蟲低。台灣東南部埃及斑蚊族群其淡色型個體比例較西南部族群多，在室內採集的成蟲淡色型比例亦比室外採集者多。分析這些成蚊之族群表皮正烷類結果發現，n-C18至n-C36的平均含量在蟲體上隨著碳數增多而增加，而各族群內孳生於室內者其淡色型比例較孳生於室外者高，且在n-C18至n-C27的平均含量較室外品系多。亦野外族群表皮正烷類的含量比實驗室品系少。族群間RAPD形質的差異明顯的將9個埃及斑蚊族群歸類為三群，依照地理位置可分為：台灣西南部偏北族群、西南部偏南族群、台灣東南部族群，西南部族群的族群有效範圍為33 km，有效密度為2.9 mosquitoes / km。

There are some variation, in the distribution of white scale on the abdominal tergites of Aedes aegypti. The C. K.Meek’s (CKM) classification system was used to identify and rank eight classes in the abdominal scale patterns, including CKM0 which was generalized as the dark form of Ae. aegypti formosus, CKM1 as the type form of Ae. aegypti aegypti and CKM2-7 as the other pale form of Ae. aegypti aegypti. The RAPD fragments profiles of seven CKM laboratory selected strains were analyzed and genetic similarities were estimated, the UPGMA dendrogram assorted these strains into two major groups: the type form and the pale form. The dendrogram was detected based on n-alkane cuticular hydrocarbon profiles of seven CKM strains. All nineteen n-alkanes (n-C18 to n-C36) were shared from female adult’s epicuticle among seven CKM strains, but varied quantitatively. The mosquito with CKM values of 2-7 strains had more abundance of components n-C18 to n-C27 than CKM 1, less abundance of n-C29 to n-C36. The scale patterns of field collected Ae. aegypti were found to have the type form and the pale form, those were mixed in the similar niche in Taiwan. The female mosquitoes within populations exhibited greater variation in scale pattern than males. The frequency CKM value in female individual was used for cluster analyses, that generated a dendrogram depicting the branches of populations. The nine populations assorted into two clusters that correspond geographically with southwestern and southeastern area in Taiwan. We also found that the southeastern mosquito populations exhibited high frequency of pale form than that of southwestern. The similar phenomenon was observed in indoor breeding populations than outdoors. Therefore, the cuticular n-alkane hydrocarbons of adults from southeastern Taiwan and indoor breeding populations were analyzed, we found these mosquitoes contained larger amount of n-C18 to n-C27. Nineteen types of n-alkanes were identified using gas chromatography electron impact-mass spectrometry. Dendrogram obtained from cluster analysis showed that grouping associated on the frequencies of pale form but not with geographic distribution. Differences in the frequencies of RAPD markers were detected among populations. Cluster analyses revealed, there were two groups separated by the Central Mountain Range. Regression analysis of geographic distances and pairwise Fst values estimated from RAPD markers showed that southwestern populations were isolated by distance of 33 km within southwestern populations and 29 km within southeastern in Taiwan.