29 research outputs found
Cross-Attraction between an Exotic and a Native Pine Bark Beetle: A Novel Invasion Mechanism?
Aside from the ecological impacts, invasive species fascinate ecologists because of the unique opportunities that invasives offer in the study of community ecology. Some hypotheses have been proposed to illustrate the mechanisms that allow exotics to become invasive. However, positive interactions between exotic and native insects are rarely utilized to explain invasiveness of pests.Here, we present information on a recently formed association between a native and an exotic bark beetle on their shared host, Pinus tabuliformis, in China. In field examinations, we found that 35-40% of P. tabuliformis attacked by an exotic bark beetle, Dendroctonus valens, were also attacked by a native pine bark beetle, Hylastes parallelus. In the laboratory, we found that the antennal and walking responses of H. parallelus to host- and beetle-produced compounds were similar to those of the exotic D. valens in China. In addition, D. valens was attracted to volatiles produced by the native H. parallelus.We report, for the first time, facilitation between an exotic and a native bark beetle seems to involve overlap in the use of host attractants and pheromones, which is cross-attraction. The concept of this interspecific facilitation could be explored as a novel invasive mechanism which helps explain invasiveness of not only exotic bark beetles but also other introduced pests in principle. The results reported here also have particularly important implications for risk assessments and management strategies for invasive species
Aphid Wing Induction and Ecological Costs of Alarm Pheromone Emission under Field Conditions
The pea aphid, Acyrthosiphon pisum Harris, (Homoptera: Aphididae) releases the volatile sesquiterpene (E)-β-farnesene (EBF) when attacked by a predator, triggering escape responses in the aphid colony. Recently, it was shown that this alarm pheromone also mediates the production of the winged dispersal morph under laboratory conditions. The present work tested the wing-inducing effect of EBF under field conditions. Aphid colonies were exposed to two treatments (control and EBF) and tested in two different environmental conditions (field and laboratory). As in previous experiments aphids produced higher proportion of winged morphs among their offspring when exposed to EBF in the laboratory but even under field conditions the proportion of winged offspring was higher after EBF application (6.84±0.98%) compared to the hexane control (1.54±0.25%). In the field, the proportion of adult aphids found on the plant at the end of the experiment was lower in the EBF treatment (58.1±5.5%) than in the control (66.9±4.6%), in contrast to the climate chamber test where the numbers of adult aphids found on the plant at the end of the experiment were, in both treatments, similar to the numbers put on the plant initially. Our results show that the role of EBF in aphid wing induction is also apparent under field conditions and they may indicate a potential cost of EBF emission. They also emphasize the importance of investigating the ecological role of induced defences under field conditions
Transgenerational effects and the cost of ant tending in aphids
In mutualistic interactions, partners obtain a net
benefit, but there may also be costs associated with the
provision of benefits for a partner. The question of whether
aphids suffer such costs when attended by ants has been
raised in previous work. Transgenerational effects, where
offspring phenotypes are adjusted based on maternal
influences, could be important in the mutualistic interaction between aphids and ants, in particular because aphids have telescoping generations where two offspring generations can be present in a mature aphid. We investigated the immediate and transgenerational influence of ant tending on aphid life history and reproduction by observing the interaction between the facultative myrmecophile Aphis fabae and the ant Lasius niger over 13 aphid generations in the laboratory. We found that the effect of ant tending changes dynamically over successive aphid generations after the start of tending. Initially, total aphid colony weight, aphid adult weight and aphid embryo size decreased compared with untended aphids, consistent with a cost of ant association, but these differences disappeared within four generations of interaction. We conclude that transgenerational effects are important in the aphid–ant interactions and that the costs for aphids of being tended by ants can vary over generations
Evidences that human disturbance simplify the ant fauna associated a Stachytarpheta glabra Cham. (Verbenaceae) compromising the benefits of ant-plant mutualism
Interaction among species, like ants and plants through extrafloral nectaries (EFNs), are important components of ecological communities’ evolution. However, the effect of human disturbance on such specific interactions and its ecological consequences is poorly understood. This study evaluated the outcomes of mutualism between ants and the EFN-bearing plant Stachytarpheta glabra under anthropogenic disturbance. We compared the arthropod fauna composition between two groups of twenty plant individuals, one in an area disturbed by human activities and one in a preserved area. We also check the plant investment in herbivory defense and the consequential leaf damage by herbivore. Our results indicate that such disturbances cause simplification of the associated fauna and lack of proper ant mutualist. This led to four times more herbivory on plants of disturbed areas, despite the equal amount of EFN and ant visitors and low abundance of herbivores. The high pressure of herbivory may difficult the re-establishment of S. glabra, an important pioneer species in ferruginous fields, therefore it may affect resilience of this fragile ecological community.As interações entre espĂ©cies, como por exemplo formigas e plantas atravĂ©s de nectários extraflorais (NEFs), sĂŁo importantes componentes na evolução das comunidades. Entretanto, pouco Ă© conhecido sobre os efeitos dos impactos antrĂłpicos em interações especĂficas e suas consequĂŞncias ecolĂłgicas. Este estudo avaliou os resultados do mutualismo entre formigas e NEF em Stachytarpheta glabra em área impactada pela atividade humana. NĂłs comparamos a composição e estrutura da fauna de artrĂłpodes, em quarenta plantas de dois grupos, um impactado por atividades humanas e o outro preservado. NĂłs tambĂ©m avaliamos o investimento da planta em defesas contra herbĂvoros e os danos foliares causados por herbĂvoros. Nossos resultados indicam que os distĂşrbios causam a simplificação da fauna associada e a ausĂŞncia de uma formiga mutualista anti-herbĂvoros. Isto leva a quatro vezes mais herbivoria nas plantas da área impactada, a despeito da mesma quantidade encontrada para NEF e formigas visitantes. A grande pressĂŁo de herbivoria pode dificultar o reestabelecimento de S. glabra, uma espĂ©cie pioneira importante nos campos ferruginosos, dessa forma, afetando a resiliĂŞncia dessa comunidade ecolĂłgica ameaçada