Ecological Responses To High Temperature In Plutella Xylostella And Database Of Heat-related Gene In Insects

Extremely hot events are expected to increase in frequency under global warming. The impact ofthese events is generally overlooked in insect population prediction, since they are unlikely to causewidespread mortality. Here we use the diamondback moth, Plutella xylostella, the most destructive pestof cruciferous crops as our model organism. We analyzed the occurrence characteristics of hot events inmain hazard area by P. xylostella. Then we simulated these different patterns of hot events experiencedunder field conditions and examined the temperature effects on the reproductive performance of P.xylostella. The main results were shown as follows:1. A single hot event that does not affect survival but decreases reproduction in the diamondbackmoth. Daily maximum ambient temperatures near Changjiang River often exceeded40oC. Hightemperatures under field conditions might only occur on a single day and last for3-5hours. This eventhad no detrimental effects on immediate mortality, copulation duration, mating success, longevity orlifetime fecundity, but stressed females produced21%fewer hatched eggs. Female heat exposure led toa lager effect on fertile egg production than male heat treatment. Exposure on female or male or bothsex extended pre-mating period for4-7hours.2. With an increase of exposure time at40oC, the survival rates of P. xylostella in differentdevelopment stage signigiantly declined. Different development stage of P. xylostella had significantvariance in thermal tolerance against to40oC.3rdinstar larva had the strongest thermal resistance to40oC, followed by pupa and adult.1stinstar larva and egg is most thermal sensitive. After acomprehensive analysis of thermal tolerance in other insects, we do not find any consistent difference indevelopment stages.3. Daily mean temperature near Changjiang River often exceeded30oC. Organisms were likelyto experience very different temperature regimes during their life-cycle, both in the timing and duration.High temperature in larval stage could shorten male longevity and decline the lifetime fecundity.Furthermore, we found these temperature effects by larva stress often depended on pupa or adulttemperature. The negative effects by larva high temperature could be exacerbated by pupa heattreatment, but they could be overwhelmed by high adult temperature. Interestingly, we find that thenumber of total egg production declines linearly as a increasing of the exposure time across the lifestages. Stressed females when exposed to30oC in a generation lay fewest eggs with a reduction in28.6%.4. Egg stress at40oC for3-7hours could decline the pupation rate and emerenge rate. Thedecline in lifetime fecundity at25oC could be induced by a decrease in pupa weight after egg treatments.Furthermore, we found these temperature effects by egg stress often depended on subsequentdevelopment temperatures. Modest high development temperature could increase the survival rate inpupation and emergence after egg stress. The negative effects by egg stress could be overwhelmed by high development temperature.5. We searched185papers (published from1990to2014) related to the underlying mechanismsof insects in high temperatures. We exploited the information from these papers, including thermal oreclolgical response to high temperatures, gene expressoion and sequence infromation. A total number of762items were derived from these literatures. Finally, we build a database of heat-related gene ininsects on the MySQL server.