研究生:周惠君Hui-Chun Chou




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種棉蚜(Aphis gossypii Glover(Homoptera: Aphididae))寄主植物上棉蚜小蜂Aphelinus gossypii Timberlake(Hymenoptera: Aphelinidae)之發育時間、功能反應及族群變動之研究

Developmental Time, Functional Responses and Population Fluctuations of Aphelinus gossypii Timberlake (Hymenoptera : Aphelinidae) on three Host Plants of the Cotton Aphid, Aphis gossypii Glover (Homoptera: Aphididae)




研究生:周惠君Hui-Chun Chou


指導教授:賴博永、彭仁君Po-Yung Lai、Jen-Jiun Perng

摘要

棉蚜小蜂(Aphelinus gossypii Timberlake)具有寄生及取食寄主蚜蟲之雙重剝削寄主現象,乃野外棉蚜(Aphis gossypii)族群的重要天敵之一。棉蚜之寄主植物廣泛,本研究調查比較蚜小蜂在三種植物番石榴Psidium guajava L.(Myrtaceae)、紫花霍香薊Ageratum houstonianum Mill.(Compositae)及大花咸豐草Bidens pilosa L. var. radiata(B1)Sherff(Compositae)上之族群變動,並利用在三種不同植物上生長之棉蚜,來探討棉蚜小蜂發育時間及功能反應之差異。

在田間三種植物上,棉蚜寄生蜂之族群密度與種類具有明顯差異。番石榴上共採有初級寄生蜂5種,其中以Aphelinus gossypii為最多,其族群密度在11月為最多,5-9月為最少。

蚜小蜂族群密度主要受番石榴上棉蚜數量的正影響(R2=0.2951,p=0.0184)。大花咸豐草採有初級寄生蜂兩種,為Aphelinus gossypii 及Aphelinus sp.,但取樣數量明顯偏低共僅14隻。紫花霍香薊則有包括A. gossypii在內的三種初級寄生蜂,其中以Aphelinus sp.為最多,其族群密度在1-3月為最多,與溫度變化關係最高(r=-0.8722,P=0.0002)。

在三種寄主植物上,棉蚜小蜂之發育時間皆有顯著差異。從產卵至化蛹之發育時間,以在番石榴上最短為5.6天,在大花咸豐草上最長為6.8天;從化蛹至羽化之發育時間,以在紫花霍香薊上最短為6.4天,在大花咸豐草上最長為6.8天;從產卵至羽化之發育時間,以在番石榴上最短為12.3天,在大花咸豐草上最長為13.7天。

於定溫25℃下,分別在約60㎝2之番石榴、紫花霍香薊及大花咸豐草三種植物葉片上,以棉蚜小蜂對8個不同棉蚜密度(2, 4, 8, 16, 32, 64, 128, 160隻/葉),處理24小時,比較寄主取食、寄生及總消耗三種棉蚜小蜂之功能反應型式。棉蚜小蜂寄主取食蚜蟲量隨棉蚜密度增加,呈現Holling第Ⅱ型功能反應型式,至160蚜蟲密度時,達到取食上限(紫花霍香薊5.75隻、大花咸豐草8.75隻、番石榴6.88隻);在寄生作用上,其寄生量亦隨棉蚜密度增加至128蚜蟲密度時,達寄生上限(紫花霍香薊25.13隻、番石榴38.13隻),大花咸豐草則至160蚜蟲密度時,才達寄生上限25.5隻,亦較符合Holling第Ⅱ型功能反應型式;包含取食及寄生之總消耗量隨寄主密度增加至128、160及128蚜蟲密度時,達寄主消耗上限(紫花霍香薊29.88隻、大花咸豐草34.25隻、番石榴44.38隻),符合Holling之第Ⅱ型功能反應模式。

本研究顯示,棉蚜初級寄生蜂在番石榴作物上之族群密度與種類較其他兩種野草為高,且棉蚜小蜂之發育時間以在番石榴作物上之發育時間最短,而在兩種野草上之發育時間較長,可能與植物種類及葉片營養化學成分有關。棉蚜小蜂在三種棉蚜寄主植物上之功能反應,亦以在番石榴作物上有最高攻擊率、最短處理時間和最大消耗寄主棉蚜上限值,對棉蚜的寄生捕食作用要較在兩種野草上為好。但兩種野草或許能在缺乏作物或營養不足等不利條件下幫助維持棉蚜之族群,進而維繫其寄生蜂族群之存在,成為寄生蜂天敵替代生長之庇護所。

關鍵字:族群變動、棉蚜小蜂、寄主取食、功能反應、寄生、發育時間、植物

Abstract

The parasitoid, Aphelinus gossypii, can both parasitize and feed on its host aphids. It is an important natural enemy in regulating cotton aphid population.

In this study, we investigated the population fluctuations of aphid parasitoids on three different plants (Psidium guajava L., Ageratum houstonianum Mill, Bidens pilosa L.), and compared the developmental time and functional responses of A. gossypii among the three different plants. The species composition and population densities of parasitoids were distinctively different among the three different plants. There were 5 species of primary parasitoids collected on P. guajava, among them, A. gossypii was the most abundant. Its population density reached the highest level in November, and then dropped to the lowest level from May to September. A positive correlation was detected in the density fluctuations between A. gossypii and the cotton aphid on P. guajava(R2=0.2951,p=0.0184). Three species of primary parasitoids were found on A. houstonianum, of which, Aphelinus sp. was the most abundant. Its population density reached the highest level from January to March. Temperature showed a positive correlation in the density fluctuation of Aphelinus sp. on A. houstonianum(r=-0.8722,P=0.0002). On Bidens pilosa, two primary parasitoids, Aphelinus spp. were detected, but bolt were present at a very low level with only 14 individuals collected.

There were significant differences in developmental time of A. gossypii on the three different host plants. The developmental time from parasitization to mummification was the shortest on P. guajava at 5.63 days, and the longest on B. pilosa at 6.8 days. The developmental time from mummification to adult emergence was the shortest on A. houstonianum at 6.4 days, and the longest on B. pilosa at 6.8 days. The total developmental time from parasitization to adult emergence was the shortest on P. guajava at 12.3 days, and the longest on B. pilosa at 13.7 days.



At 25℃, a single female of A. gossypii was exposed to the cotton aphid at eight different densities (2, 4, 8, 16, 32, 64, 128, 160 per leaf disk) on three different plants for 24 hours, to determined its effectiveness in host feeding . The number of the cotton aphids fed by A. gossypii increased with the increase of aphid density. A. gossypii showed a Type Ⅱ functional response. The host-feeding number reached the upper limit when aphid density at 160 aphids per leave (5.75 aphids fed on A. houstonianum, 8.75 on B. pilosa, and 6.88 on P. guajava). The parasitized aphid number reached the upper limit at aphid density of 128 aphid per leave (25.13 aphids parasitized on A. houstonianum, and 38.13 on P. guajava). The aphids parasitized on B. pilosa  reached the upper limit (25.5 aphid per leaf) when aphid density increased to 160 aphids per leaf. The parasitized aphids by A. gossypii also showed a Type Ⅱ functional response type. The number of aphids consumed reached the upper limit when the aphid density at 128, 160 and 128 aphids per leaf (29.88 aphids consumed on A. houstonianum, 34.25 on B. pilosa, and 44.38 on P. guajava). The curve of consumed aphids by A. gossypii showed a Type Ⅱ functional response. Although A. gossypii showed a better performance both in predation and parasitism to cotton aphid on P. guajava, the parasitoid also has a high potential controlling the cotton aphids on the two different weeds.
Keywords: population fluctuation、Aphelinus gossypii、host-feeding、functional response、parasitization、developmental time、plant


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