S-Space College of Agriculture and Life Sciences (농업생명과학대학) Dept. of Agricultural Biotechnology (농생명공학부) Theses (Ph.D. / Sc.D._농생명공학부)
Overwintering ecology and population genetics of Lycorma delicatula (Hemiptera: Fulgoridae) in Korea
- 농업생명과학대학 농생명공학부
- Issue Date
- 서울대학교 대학원
- 학위논문 (박사)-- 서울대학교 대학원 : 농생명공학부, 2015. 2. 이준호.
- Lycorma delicatula (White) (Hemiptera: Fulgoridae) was recently introduced to an invasive alien species, and was also agricultural pest in particular grape vine, in Korea.
Overwintering is a key element of survival for L. delicatula. Ability for cold tolerance showed the temporal changes during the overwintering season of L. delicatula, in Korea. In the field, hatching rate (%) of egg masses showed 72.1, 33.1, 84.3 and 52.3 % in 2010, 2011, 2012, and 2013, respectively. January was well explained time by following population size of 1st nymph in Korea. Therefore, I suggested the relationship between hatchability and temperature in January. The hatching rate of 1st nymph L. delicatula in field was well predicted in these models.
Diapause development was applied for the hatching model of overwintering L. delicatula eggs. The relationship between egg developmental rate and temperature was described in a linear model and a non-linear model. The lower developmental threshold temperature was 11.13 C, and the thermal constant was at 293.26 degree days. Hatching model was well validated in 1st nymph of L. delicatula collected in field.
Seasonal occurrence of L. delicatula was investigated among three host plants (Vitis vinifera, Ailanthus altissima and Morus alba). Female ratio of L. delicatula sampled from A. altissima was ranged from 35 to 45 %. The occurrence data were fitted to the logistic model based on the degree days (base 11.13 C). Therefore, accumulated degree days were calculated as 271, 492, 620 and 908 DD, at 1st, 2nd, 3rd and 4th instar nymph in the peak time of A. altissima, respectively. This model was not incorporated into adult stage of L. delicatula, because of its dispersal behavior on A. altissima.
We isolated and characterized eight microsatellite loci for L. delicatula by using a hybridization-biotin enrichment method. Population genetic structure was conducted among nine locations in Korea. Isolation by distance (IBD) suggested that populations in South Korea have not yet reached genetic equilibrium, also genetic differentiation (global FST=0.0474) indicated in range expansion recently. Bayesian-based clustering analysis indicated the presence of at least three genetically unique populations in Korea, which showed a distinct genetic background in Cheonan and Samcheok. The assignment test suggested that long-distance dispersal of L. delicatula may have occurred over large areas of South Korea. More complex dispersal patterns may have occurred during L. delicatula invasion of heterogeneous landscapes in South Korea.
Also, we evaluated the sink-source metapopulations at four locations (Cheonan, Daegu, Suwon and Gwangju) in Korea. Cheonan showed relatively larger effective population size (Ne) and lower immigration rate (m) than other regions. A comparison among life stages, AMOVA showed different genetic variation between nymph and post-oviposition populations. Also, subgraph was constructed by post-oviposition in full graph with 29 edges. Therefore, genetic parameters were partially implied by the oviposition and were triggered for active dispersal of L. delicatula.
Integrated genetics and population ecology may provide the improved management plans and insight for hidden invasion phenomena of L. delicatula in Korea.