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Plant-Mediated Interaction : A First Record of Thrips Feeding on Hartigiola annulipes (Diptera: Cecidomyiidae) Galls

Pilichowski Sebastian, Ulitzka Manfred R., Jagiełło Radosław, Giertych Marian J.

Polish Journal of Ecology

2019

Vol. 67, nr 2

168--173

Galls formed by insects can act as sinks for nutrients and attract other herbivores to feed on gall tissues, which initiates interspecific competition, sometimes nurturing the herbivorous insects and restraining the gall-inducing insect, particularly when this competition is plant-mediated. Here, to our knowledge, we provide the first evidence of a close relationship between a gall insect, Hartigiola annulipes (Diptera: Cecidomyiidae), and a sap-sucking, Liothrips setinodis (Thysanoptera: Phlaeothripidae). The thrips were observed feeding on young H. annulipes galls, formed on the common beech (Fagus sylvatica) leaves during spring. Among randomly chosen beech trees, 100 current-year shoots were surveyed to determine the number of H. annulipes galls and the presence of thrips on the leaves. Our results show that L. setinodis specimens were found significantly more frequently on leaves infested by the galler than on uninfested leaves. The consequences of feeding thrips at the site of gall formation are not known yet, but it can be supposed that they are unfavourable to the gall insects and therefore could be beneficial for the host plant.

Differences in defence strategies against herbivores between two pioneer tree pecies: Alnus glutinosa (L.) Gaertn. and Betula pendula Roth.

Giertych Marian J., Karolewski Piotr, Żytkowiak Roma, Oleksyn Jacek

Polish Journal of Ecology

2006

Vol. 54, nr 2

181-187

The different defence strategies of trees against herbivores are very often connected with succession status, leaf life span and the level of secondary metabolites. We examined the effect of simulated leaf grazing on the differences in the leaf life span and defence chemistry of two pioneer tree species that belongs to the same family (Betulaceae), black alder (Alnus glutinosa (L.) Gaertn.) and European white birch (Betula pendula Roth.). At the beginning of the growing season, mature leaves were perforated using a paper punch. The holes removed about 10% of the leaf surface. Each species was represented by six trees - one branch was chosen for perforation and one branch as a control. All leaves were counted every week until their abscission. Additional damages caused by grazing insects were also noted.Undamaged birch leaves were held much longer than those of alder. The average difference in half leaf life span between control and perforated leaves was 28 days in birch and 6 in alder. The control unperforated alder leaves were significantly (P <0.05) more often grazed by insects than those that were perforated. Leaf perforation in alder increase phenolic concentrations in the new, young leaves. In birch we did not observe these changes.The comparison of alder and birch indicate that the species with similar successional status can have different strategies of leaf defence. The birch leaves were characterized by a longer leaf life span, constitutive defence, a lack of induced defence accumulation of phenolics and earlier shedding of damaged leaves in comparison to the control. The black alder foliage had a shorter leaf life span, induced defence reaction (producedmore phenolics after perforation), and only slightly earlier shedding of damaged leaves than the control.