Gut content analysis is a useful tool when studying arthropod predator-prey interactions. We used polymerase chain reaction （PCR） technique to examine how detection of prey DNA in the gut content of predators was in...Gut content analysis is a useful tool when studying arthropod predator-prey interactions. We used polymerase chain reaction （PCR） technique to examine how detection of prey DNA in the gut content of predators was influenced by digestion time and temperature. Such knowledge is critical before applying PCR-based gut content analysis to field collected predators. Larvae of the two-spotted ladybeetle （Adalia bipunctata L.） were fed with the bird cherry-oat aphid （Rhopalosiphum padi L.） at either 21℃ or 14℃. After consuming one aphid, the predators were allowed to digest the prey for a range of time periods up to 24 hours. The influence of temperature on A. bipunctata feeding behavior was also recorded. From the fed larvae, total DNA was extracted and PCR reactions with R. padi specific primers were run. The number ofA. bipunctata that tested positive for R. padi DNA was negatively related to the length of digestion time. Temperature influenced larval feeding behavior but did not have a significant effect on R. padi DNA detection. After pooling the data from both temperature treatments we estimated the time point when R. padi DNA could be amplified from 50% of the fed A. bipunctata by PCR to be 4.87 hours. With such a rapid decrease in prey DNA detection success, positive PCR reactions will most likely be the result of predation events occurring shortly before capture. If a defined digestion temperature range has proven not to influence prey detection, PCR data obtained from predators collected within that particular range can be interpreted in the same way.展开更多
The common nettle （Urtica dioica L.） is a perennial and cosmopolitan plant species and is known to be the source of food for a great diversity of insects. To understand the importance of the nettle in agro-ecosystem...The common nettle （Urtica dioica L.） is a perennial and cosmopolitan plant species and is known to be the source of food for a great diversity of insects. To understand the importance of the nettle in agro-ecosystems, a field experiment was carried out in an experimental farm at Gembloux （Belgium） to study the effect of nettle margin strips on aphid and aphidophagous populations in close field crops, namely wheat （Triticum aestivum L.）, green pea （Pisum sativum L.） and rape （Brassicae napus L.）. The aphids and related beneficial populations were weekly assessed, from March to August 2005, by visual observations in two plots per field crop. A higher abundance of aphidophagous beneficials was collected in nettle strips when compared to the field crops. Particularly, the presence of predatory anthocorids, mirids and green lacewings was observed on nettle only. Nevertheless, the most abundant aphid predatory family, the Coccinellidae, was distributed in both environments, in nettle strips and in crop fields. The field margin supported a significantly higher density ofHarmonia axyridis than the field crops. In contrast, the field crops, green pea particularly, supported a higher density of Coccinella septempunctata. The distribution of the aphidophagous species, mainly the ladybirds, was discussed in relation to the host plant and related aphid species and their potential effect on integrated pest management.展开更多
The ability to recognize aphidophages is one of the key points in the protection ants provide aphids against their natural enemies. Behavior of honeydew collectors from nature （＂field,＂ control） and laboratory rea...The ability to recognize aphidophages is one of the key points in the protection ants provide aphids against their natural enemies. Behavior of honeydew collectors from nature （＂field,＂ control） and laboratory reared ＂naive＂ ants of Formica pratensis Retzius, which had never met either ＂mature＂ workers or aphids and aphidophages, was observed during their pairwise interactions with ladybird imagines and hoverfly larvae. The majority of the ＂naive＂ ants perceived ladybirds as an enemy at their first encounter attacking them immediately without any prior antennation. Ants seem to have a certain innate ＂enemy image＂ that lets them react very quickly to protect aphids. Hoverfly larvae were rarely attacked by both ＂field＂ and ＂naive＂ ants （〉 15%）. During tests with ladybirds ants from nature attacked them and also demonstrated the most aggressive reactions （series of bites and ＂death grip＂） less frequently than the ＂naive＂ ants. The percentage of ants avoiding aphidophages after a contact with their chemical defense （reflex bleeding and glue-like saliva） was significantly higher in the control group. Whereas the ＂naive＂ ants did not learn to avoid danger, foragers from nature usually tried to avoid negative experience and used tactics of ＂short bites.＂ Overall, experience has been proved to be unimportant for displaying key behavioral reactions underlying ant-ladybird interaction. However, accumulation of experience has been assumed to play an important role in the formation of behavioral strategy that allows honeydew collectors to drive aphidophages away with lower energy costs and avoid or minimize negative consequences of aphidophages＇ chemical defense.展开更多
文摘Gut content analysis is a useful tool when studying arthropod predator-prey interactions. We used polymerase chain reaction （PCR） technique to examine how detection of prey DNA in the gut content of predators was influenced by digestion time and temperature. Such knowledge is critical before applying PCR-based gut content analysis to field collected predators. Larvae of the two-spotted ladybeetle （Adalia bipunctata L.） were fed with the bird cherry-oat aphid （Rhopalosiphum padi L.） at either 21℃ or 14℃. After consuming one aphid, the predators were allowed to digest the prey for a range of time periods up to 24 hours. The influence of temperature on A. bipunctata feeding behavior was also recorded. From the fed larvae, total DNA was extracted and PCR reactions with R. padi specific primers were run. The number ofA. bipunctata that tested positive for R. padi DNA was negatively related to the length of digestion time. Temperature influenced larval feeding behavior but did not have a significant effect on R. padi DNA detection. After pooling the data from both temperature treatments we estimated the time point when R. padi DNA could be amplified from 50% of the fed A. bipunctata by PCR to be 4.87 hours. With such a rapid decrease in prey DNA detection success, positive PCR reactions will most likely be the result of predation events occurring shortly before capture. If a defined digestion temperature range has proven not to influence prey detection, PCR data obtained from predators collected within that particular range can be interpreted in the same way.
文摘The common nettle （Urtica dioica L.） is a perennial and cosmopolitan plant species and is known to be the source of food for a great diversity of insects. To understand the importance of the nettle in agro-ecosystems, a field experiment was carried out in an experimental farm at Gembloux （Belgium） to study the effect of nettle margin strips on aphid and aphidophagous populations in close field crops, namely wheat （Triticum aestivum L.）, green pea （Pisum sativum L.） and rape （Brassicae napus L.）. The aphids and related beneficial populations were weekly assessed, from March to August 2005, by visual observations in two plots per field crop. A higher abundance of aphidophagous beneficials was collected in nettle strips when compared to the field crops. Particularly, the presence of predatory anthocorids, mirids and green lacewings was observed on nettle only. Nevertheless, the most abundant aphid predatory family, the Coccinellidae, was distributed in both environments, in nettle strips and in crop fields. The field margin supported a significantly higher density ofHarmonia axyridis than the field crops. In contrast, the field crops, green pea particularly, supported a higher density of Coccinella septempunctata. The distribution of the aphidophagous species, mainly the ladybirds, was discussed in relation to the host plant and related aphid species and their potential effect on integrated pest management.
文摘The ability to recognize aphidophages is one of the key points in the protection ants provide aphids against their natural enemies. Behavior of honeydew collectors from nature （＂field,＂ control） and laboratory reared ＂naive＂ ants of Formica pratensis Retzius, which had never met either ＂mature＂ workers or aphids and aphidophages, was observed during their pairwise interactions with ladybird imagines and hoverfly larvae. The majority of the ＂naive＂ ants perceived ladybirds as an enemy at their first encounter attacking them immediately without any prior antennation. Ants seem to have a certain innate ＂enemy image＂ that lets them react very quickly to protect aphids. Hoverfly larvae were rarely attacked by both ＂field＂ and ＂naive＂ ants （〉 15%）. During tests with ladybirds ants from nature attacked them and also demonstrated the most aggressive reactions （series of bites and ＂death grip＂） less frequently than the ＂naive＂ ants. The percentage of ants avoiding aphidophages after a contact with their chemical defense （reflex bleeding and glue-like saliva） was significantly higher in the control group. Whereas the ＂naive＂ ants did not learn to avoid danger, foragers from nature usually tried to avoid negative experience and used tactics of ＂short bites.＂ Overall, experience has been proved to be unimportant for displaying key behavioral reactions underlying ant-ladybird interaction. However, accumulation of experience has been assumed to play an important role in the formation of behavioral strategy that allows honeydew collectors to drive aphidophages away with lower energy costs and avoid or minimize negative consequences of aphidophages＇ chemical defense.
