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Ecological Studies of Periphyllus koelreuteriae (Takahashi) (Homoptera: Chaitophoridae) in Taiwan
Periphyllus koelreuteriae (Takahashi)
holocyclic life cycle
|摘要:||本試驗於臺灣首度發現欒樹圓尾蚜 (Periphyllus koelreuteriae (Takahashi))之有性世代，並完成有性世代之發育及繁殖試驗，卵於低溫5℃及高溫25〜30℃時無法孵化；卵生雌蚜 (oviparous female)及雄蚜 (male)於30℃時無法完成發育，幹母 (fundatrix)僅於15℃及20℃時能完成世代。越夏型 (aestivating form)僅於20℃及25℃時能完成世代；正常型 (normal form)則於5〜30℃各定溫下均能完成幼期發育，正常型發育時間以5℃時最長，為54.21天，30℃時最短，為6.37天，整個幼期之臨界低溫與總積溫分別為3.82℃與186.57DD，成蚜壽命以10℃最長，為23.42天，繁殖率以20℃之35.07隻子代/雌蚜為最高。卵生雌蚜幼期發育時間以5℃時之49.75天為最長，而以25℃時之10.47天為最短，發育臨界低溫為 1.48℃，整個幼期之總積溫為259.07DD，壽命以10℃最長，為15.68天，繁殖率以20℃之5.88卵/雌蚜為最高。雄蚜幼期發育時間以5℃時之45.75天為最長，而以25℃時9.40天為最短，發育臨界低溫為1.43℃，整個幼期之總積溫為238.10DD，壽命以20℃之9.33天為最長。幹母卵期以10℃時需60.25天為最長，20℃時之30天為最短，幼期發育時間以15℃時之81.40天為最長，而以20℃時之50.71天為最短，壽命以15℃最長，為18.80天，繁殖率以20℃之45.43隻子代/雌蚜為最高。越夏型一齡若蚜之發育臨界低溫及總積溫分別為7.93℃及140.85DD，壽命以25℃之9.60天為最長，繁殖率以25℃之25.00隻子代/雌蚜為最高。
欒樹圓尾蚜於5℃〜30℃定溫下之生命表顯示，正常型及有性型之齡期頻度分布各齡期間具重疊現象，若蚜期所佔日齡範圍均較成蚜為小。幹母以卵期所佔日齡範圍最大，越夏型以一齡若蚜之日齡範圍最大。齡別存活率於溫度愈低時其齡別存活率 (lx)曲線愈延長，齡別繁殖率 (mx)於雌蚜開始產若蚜後皆隨年齡之增加而產若蚜數增加。正常型之內在增殖率 (r)均大於0，淨增殖率 (R0)均大於0，終極增殖率 (λ)皆大於1。有性型僅於15℃時之r值為正值，R0及λ均大於1。幹母及越夏型之r值均大於0，R0及λ均大於1。各型蚜之平均世代時間 (T)以幹母於15℃時之85.20天為最長，正常型於25℃時之14.85天為最短。年齡－齡期繁殖值 (Rij)之高峰發生於成蚜初期，正常型以20℃之平均每天每一雌蚜產16.73隻子代為最高，有性型則以15℃時平均每一雌蚜產3.78隻子代為最高。齡別期望壽命 (Ex) 正常型以5℃時之99天為最長，以25℃時之29天為最短，有性型則以10℃時之59天為最長，25℃時之19天為最短。
自1997年7月至2000年6月底，於臺中大坑地區臺灣欒樹上連續三年所作之族群變動調查顯示，欒樹圓尾蚜於田間之發生時間均集中於每年9月底至隔年6月底間，其族群高峰均發生於1-2月間。樹冠不同方位及不同層次均以下層之族群數量最高，正常型無翅雌蚜之數量遠多於有翅雌蚜。越夏型僅出現於每年3〜6月間，其發生高峰為4〜5月間。有性型發生於寄主植物落葉期，卵生雌蚜出現於每年12月底至次年2月中旬，雄蚜則發生於1月中旬至2月中旬。天敵以六條瓢蟲 (Menochilus sexmaculatus)居多，於每年12月底至次年6月底間均可發現，其發生高峰於1-2月間。欒樹圓尾蚜族群總數之變動經分析主要受到西向樹冠之欒樹圓尾蚜總數的正影響。幼期各齡期及多態型各型蚜與溫度及光照呈負相關，1-2齡若蚜、3-4齡若蚜、蚜蟲總數、無翅雌蚜及有翅雌蚜呈正相關；越夏型若蚜與各因子間均無相關性。卵生雌蚜與蚜蟲總數及有翅雌蚜呈正相關，所有蚜蟲總數之負相關因子為溫度、光照、天敵數及雄蟲數，正相關因子則為1-2齡若蚜、3-4齡若蚜、有翅雌蚜、無翅雌蚜及卵生雌蚜。|
The sexual life cycle of Periphyllus koelreuteriae (Takahashi) has been observed and recorded for the first time in Taiwan by this study. P. koelreuteriae (Takahashi) completes it's life cycle on the host plant, Koelreuteriae formosana (Hayata), all year round. The asexual cycle of viviparous generations occurs in spring, summer and autumn, while the sexual oviparous generations appear in winter with eggs as the overwintering form. Nymphs of aestivating form are produced in summer. Both winged and wingless viviparae can be found in the field throughout the year, except from July to September when the aphid population is extremely low. The wingless oviparous females appear in the period of foliage falling of the host plants (December to February) accompanied by the lowest temperature of the year. Males and eggs are found from mid-January to early February; and nymphs of aestivating form emerge from March to June. About 20 overlapping generations of this aphid occur each year. Developmental time of each instar of Periphyllus koelreuteriae (Takahashi) nymphs at six constant temperatures of 5, 10, 15, 20, 25 and 30℃ were significantly different. Developmental time of each instar reduced with the increasing of temperatures. The longest development time for normal form was 54.21 days at 5℃ and the shortest was 6.37 days at 30℃. For aestivating form, only at 20℃ and 25℃ the aphids could complete their developmental stages, whereas at lower temperatures, 10℃ and 15℃, no further development was observed after first instar. In comparison of the developmental time of first instar nymph of normal form with aestivating form, there were significantly different at temperatures of 10℃ and 15℃. The low developmental threshold temperature of first instar for normal form and aestivating form were 4.06 and 7.93℃, respectively, and the thermal summation were 44.86 and 140.85DD, respectively. The low developmental threshold temperature and the thermal summation of first instar of aestivating form were higher than those of the normal form, showing that was an obviously diapause in the first instar nymph of aestivating form. The low developmental threshold and thermal summation of normal form nymphal stage were 3.82℃ and 186.57 DD, respectively. The adult longevity and fecundity of normal form and aestivating form were 14.28 and 7.50 days, 35.07 and 9.40 offspring/♀, respectively, at 20℃, and showing significantly different in longevity and fecundity. However, there was no significantly different in longevity and fecundity at 25℃. In comparison of the body size of each instar of both forms reared at given constant temperatures, the aestivating form nymphs were shorter and wider than the normal form. The work reported here represents the first study of the development, longevity and reproduction of sexual form of aphids in Taiwan; and the effect of temperature was measured from 5℃ to 30℃ at intervals of five degrees. For Periphyllus koelreuteriae (Takahashi), the oviparous females and males could not complete their developmental stages at 30℃, and no eggs hatched at 5℃ or above 25℃; and the fundatrix completed their developmental stages only at 15℃ and 20℃. The developmental time of juvenile stages of oviparous females, males and fundatrix was reduced with increasing temperature. For oviparous females, the longest developmental time was 49.75 days at 5℃, and shortest was 10.47 days at 25℃; the low developmental threshold temperature was 1.48℃, and the thermal summation was 259.07 DD; the longest longevity of adults was 15.68 days at 10℃, and the highest fecundity, 5.88 egg/females was at 15℃. For males, the longest developmental time of juvenile stages was 45.745 days at 5℃, and the shortest was 9.40 days at 25℃; the low developmental threshold temperature was 1.43℃, and the thermal summation was 238.10 DD; the longest longevity of adults, 9.33 days, appeared at 20℃. For fundatrix, the longest hatching time of eggs required 60.25 days at 10℃, and the shortest was only 30 days at 20℃; the longest developmental time of juvenile stages was 81.40 days at 15℃, and the shortest was 50.71 days at 20℃; the longest longevity of adults was 18.80 days at 15℃, and the highest fecundity of adults was 45.43 offsprings/female at 20℃. Developmental time, survival rate and fecundity of polymorphic forms of Periphyllus koelreuteriae (Takahashi) were studied from 5℃ to 30℃ at intervals of five degrees. At l5℃and 10℃, no fundatrix and aestivating form could complete their development, and the developmental time of juvenile stages of normal form, oviparous female and male required 54.21, 49.75 and 45.75 days, respectively, at 5℃, and 31.00, 33.15 and 29.00 days, respectively at 10℃. At 20℃, the fundatrix required 50.71 days to complete their development while the aestivating form required 22.17 days. Eggs could not hatch at higher temperature of 25℃, and the aestivating form showed the longest developmental time of 22.17days at 20℃. At 30℃, only normal form completed their development, which took 6.38 days. The fundatrix could survive only at 15℃and 20℃, with the highest survival rate of 41.48% at 20℃. The survival rate varied widely from 5℃ to 30℃ for the normal form, with the highest rate at 15℃to 25℃. The surviving temperature for aestivating form was confined only from 20℃ to 25℃, with the highest survival rate of 33.33% at 25℃. The survival temperature of oviparous female and male ranged from 5℃ to 25℃, with the highest rate at 10℃ to 20℃ for the former and at 15℃ to 25℃ for the latter. The adult longevity for the normal form was the longest, 19.78 days, at 5℃, much longer than those of the oviparous female (3 days) and male (2 days); at 10℃, the longevity of normal form and oviparous female was significantly longer than that of the male. At 15℃, the longevity of the normal form (27.34 days) and the fundatrix (18.80 days) were longer than that of the oviparous female (10.13 days) and the male. The longevity of different forms of adults ranged from 7.5 to 14.28 days at 20℃, and 4.14 to 9.60 days at 25℃ and the differences among the forms were not significant at either temperature. The adult fecundity was not significantly different form 5℃ to 15℃. However, the fecundity of the fundatrix (45.43 offsprig/female) and normal form (35.07 offspring/female) was higher than that of the aestivating form (9.40 offspring/female) and the oviparous female (3.06 egg/female) at 20℃. At 25℃, both the normal form and aestivating form had the highest fecundity, 31.34 and 25.00 offspring/female, respectively. The life table of normal and sexual form of Periphyllus koelreuteriae (Takahashi) were studied from 5℃ to 30℃ at 5 degree intervals. It has been found that this species could not survive at 30℃. The stage frequency distribution of both forms was overlapped between stages, and the distribution of age frequency of adults was always wider than that of the nymphs. The fundatrix and the aestivating form could survive only at 15℃ to 20℃ and 20℃ to 25℃, respectively. The distribution of age frequency of egg stage was the widest among all stages for the former and that of the first nymphal stages was the widest for the latter. The results also showed that the fecundity (mx) of females, immediately after they started to produce, increased with age, and gradually reduced after reaching their reproductive peak. Both of the intrinsic rate of increase ( r ) and the reproductive rate (R0) of normal form were greater than 0, and the finite rate of increase (λ) was greater than 1. The r value of sexual form was positive only at 15℃ and the R0 and λ were both greater than 1. The r value of the fundatrix and the aestivating form were greater than 0, while the R0 and λ were greater than 1. The mean generation time (T) of all forms was gradually reduced with increasing temperature, with the longest T of 85.20 days at 15℃ for the fundatrix and the shortest of 14.85 days for the normal form. Peaks of the age-stage specific reproductive values (Rij) appeared at the beginning of adult stage, with the highest daily reproduction of an average of 16.73 offspring/female for the normal form at 20℃, and 3.78 offspring/female for the sexual form at 15℃. The longest age-specific expectation of life (Ex), 99 days, was found at 5℃ for the normal form and the shortest was 29 days at 25℃; the longest Ex was 59 days for sexual form at 10℃ and the shortest was 19 days at 25℃. It has been found in this study that under constant photoperiods of 10L:14D and 12L:12D, changing the temperature alone could not induce the Periphyllus koelreuteriae (Takahashi) to produce aestivating form offspring. However, a shift of the photoperiod from 10L:14D to 12L:12D, simulating the lighting conditions in the beginning of summer at temperatures between 10℃ and 25℃, could induce the production of aestivating offspring. The percentage of aestivating form offspring produced would decrease with the days and the generations after the photoperiod was shifted. The highest percentage always appeared at 20℃: with 26.27% and 18.33% on the first day of the first and the second generations, respectively; however, no aestivating form was produced on the fifth day of these two generations. For the third generation, 2.44% aestivating form was produced only at 20℃ on the first day. The percentage of females that produced the aestivating form was the highest at 20℃, i.e., 53.33% and 40.00%, respectively, for the first and second generations. However, the percentage was reduced with temperatures lower or higher than 20℃; only 3.33% females of the third generation produced the aestivating form. The percentage of aestivating form in the offspring produced by each female was the highest at 20℃ in all generations, with 34.15% in the first generation and significant difference among different temperature treatments, and 25.82% for the second generation and no significant difference among temperature treatments. There was 20% aestivating form in the offspring produced by each female in the third generation at 20℃. The longest longevity of the females producing aestivating form was 8.09 days and 8.00 days in the first and second generations, respectively, at 15℃, and the shortest was 4.60 days and 4.00 days for the first and second generations, respectively, at 25℃. The longevity of the third generation females was 5.00 days at 20℃. A field investigation on the population fluctuations of Periphyllus koeleruteriae on host tree Koelreuteriae formosana was undertaken in Ta-Keng area of Taichung for three successive years form July 1997 to June 2000. It has been found that the occurrence of this aphid was concentrated in the cool season of September to the following June, with the population density reaching its peak in January and February. The highest population density was found in the lower layer and the lowest density in the upper layer of the canopy of host trees. Among the polymorphic forms of this species, the population size of the nymphal stage was always the largest and far more abundant than the apterous, and the alate of the normal form which also appeared in the field in the same season. The aestivating form occurred only from March to June and reached the peak in April to May. The wingless oviparous females of the sexual form appeared in December to the following February, the season when the foliage of host trees fell; and the males were found only in mid-January to mid-February. The natural enemies of this aphid, mainly the lady bird beetles, synchronized with the occurrence of the prey aphid, from December to the following June, with a peak of population in January to February. Factors causing the fluctuations of this aphid population were analyzed, and it is found that the total number of aphids in different directions and different layers of the canopy were the major factors. Populations of the 1-2 instar nymphs, 3-4 instar nymphs, alata, apterous and oviparous female were positively correlated to the total number of this aphids, while negatively correlated with temperature, light, number of natural enemy and number of males.
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