نوع مقاله : مقاله پژوهشی
نویسندگان
گروه گیاهپزشکی، دانشکده کشاورزی، دانشکدگان کشاورزی و منابع طبیعی دانشگاه تهران، کرج، ایران
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
Cannibalism, killing and consuming conspecific individuals is a widespread phenomenon that happens in many species. In this study we have investigated the effect of domatia on the cannibalism behavior of the Phytoseiid predatory mites, Phytoseiulus persimilis and Amblyseius swirskii, on sweet pepper leaves with and without domatia. The without-domatia leaves were prepared by banning the domatium with glue. To avoid the unwanted effect of glue, we put the same glue drops next to each domatium. The experiment about the effect of domatia on the cannibalism rate of predatory mites on detached leaf disks showed that for P. persimilis, the presence of domatia significantly reduced the cannibalism rate (P < 0.05). In contrast, when we changed the predator species to A. swirskii, no significant effect was recorded (P > 0.05). To investigate the effect of domatia on the establishment rate of the predator, we used the pair of detached leaves with and without domatia connected through a plastic bridge. The predators were released in the middle of the bridge. The results showed that in both predator species, the presence rate of female predators on patches with domatia was significantly higher in comparison with those without domatia (P < 0.05). The probable reasons for the difference in predator behavior are discussed.
کلیدواژهها [English]
Extended Abstract
Introduction
Cannibalism as killing and consuming conspecific individuals is considered a widespread phenomenon that happens in more than 1300 animal taxa. Cannibalism affects the animal population dynamics and might both result in population extinction and persistence. The family Phytoseiidae is known as arthropods for cannibalism behavior. Here we have investigated the effect of domatia on the cannibalistic behavior of the predatory mites, Amblyseius swirskii (Athias- Henriot) and Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseiidae) on the sweet pepper plant leaves with and without domatia. A. swirskii is related to generalist predators that have been extensively used for thrips and whitefly control, while P. persimilis is considered a specialist predator of Tetranychus.
Materials and methods
We used sweet pepper plants with natural domatia for experiments. The treatments without domatia were prepared by blocking the domatium with glue drops. The same glue drops were put on the treated leaves next to each domatium to avoid the probable influence of glue on predator behavior. The effect of domatia presence on the cannibalism rate of predatory mites was performed in a Petri dish on pepper detached leaves put upside down on water-saturated cotton. Each leaf possessed four domatia. To start the experiment, one female predator was introduced along with five same-aged conspecific larvae. The number of killed (eaten) larva were checked after 12 hours. To assay the effect of domatia on the settlement rate of the predatory mite, two experimental arenas (leaves with and without domatia each contained five predator larvae from either species and 10 T. urticae eggs) were connected through a plastic bridge on which the searching predator was released just previous the experiment got started. Monitoring was performed every 15 minutes and the predator presence on each of the arenas was recorded.
Results and discussion
Our results showed that when P. persimilis was selected as the predator, the cannibalism rate decreased significantly in the presence of domatia (P < 0.01) while switching the predator species to A. swirskii, we observed no significant difference (P > 0.05). Rasmy et al. (2004) reported that A. swirskii showed a higher tendency to feed on its conspecifics in comparison with the other same-type predator species, so the non-significant cannibalism rate in this species could not be due to less cannibalism tendency of A. swirskii comparing with P. persimilis but according to the present study, selecting a host plant without domatia could not be an appropriate solution for reducing the cannibalism rate in this species. To study the effect of domatia presence on the settling rate of the predatory mites, paired detached pepper leaves with and without domatia were connected through plastic bridges. Five predator larvae (conspecific with the introduced predator) along with 10 Tetranychus urticae eggs as the main prey were transferred to each leaf disc. The experiment was started by introducing the female predator in the middle of the plastic bridge. Regular monitoring was performed every 15 minutes for two hours and the patch in which the predator was selected to settle was recorded. The experiment was performed in 15 replicates for each predator species. The results showed that the presence rate of both predator species was significantly higher on the patches with domatia (P < 0.05).
Conclusion
We concluded that the domatia presence could decrease the rate of cannibalism in the predatory mites P. persimilis as a specialist predator. Although when A. swirskii was chosen as intraguild prey, no difference was recorded between the eaten conspecific larvae on leaves either with or without domatia. The data related to the settlement experiment showed that both predator species preferred the leaves with domatia. The effect of domatia on the biological traits of predators needs to be further investigated.
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