Forest Ecology Research Group

Research Note : Galling herbivory in Scotty Creek

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Galling herbivory in Scotty Creek

Numerous arthropod herbivores are found in the forest-wetland complex at Scotty Creek. One prominent guild of specialist arthropods found here are the group of gall-inducing arthropods (insects and mites).

Diversity of galling herbivory: An preliminary survey of galling herbivory revealed that a large majority of deciduous shrub species found here are galled by eriophyoid mites (Family: Eriophyoideae). These mites induce galls on species of willow (Salix), birch (Betula) and alder (Alnus). An initial assessment of gall-inducing insects indicates that insect gallers found on the various Salix species in this area are primarily sawflies (Hymenoptera: Tenthrenididae).

Impacts of galling herbivory in plant hosts: We examined leaf-level impacts of a gall-inducing mite (Vasates olfiedi) on birch (Betula) hosts in bogs, fens, and permafrost plateaus. This mite induces galls on leaves of Betula glandulosa (dwarf birch) growing in all three of the above habitats. Additionally, this mite also galls leaves of B. occidentalis (bog birch) and B. neoalaskana (Alaska white birch) on plateaus. We found that galling by this mite significantly reduced photosynthetic capacity in leaves of all three species found on upland permafrost plateaus. However, strong habitat-linked responses were seen in B. glandulosa leaves – while individuals of this species showed drastic declines in photosynthesis on plateaus, individual plants in bogs and fens showed no such responses. Based on these findings, is appears that the impacts of mite galling are variable, and are likely to be most pronounced in habitats and on individuals that are already exposed to abiotic stresses such as the cooler but more variable soil temperatures experienced by individuals on permafrost plateaus.

Leaves galled by Vasates olfieldi on A. Betula neoalaskana, B. B. occidentalis, and C. B. glandulosa from permafrost peat plateau sites at Scotty Creek, Northwest Territories.

Leaves galled by Vasates olfieldi on A. Betula neoalaskana, B. B. occidentalis, and C. B. glandulosa from permafrost peat plateau sites at Scotty Creek, Northwest Territories.

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