A gall-inducing arthropod drives declines in canopy tree photosynthesis
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Mature forest canopies sustain an enormous diversity of herbivorous arthropods; however, with the exception of species that exhibit large-scale outbreaks, canopy arthropods are thought to have relatively little influence on overall forest productivity. Diminutive gall-inducing mites (Acari; Eriophyoidae) are ubiquitous in forest canopies and are almost always highly host specific, but despite their pervasive occurrence, the impacts of these obligate parasites on canopy physiology have not been examined. We have documented large declines in photosynthetic capacity (approx. 60%) and stomatal conductance (approx. 50%) in canopy leaves of mature sugar maple (Acer saccharum) trees frequently galled by the maple spindle gall mite Vasates aceriscrumena. Remarkably, such large impacts occurred at very low levels of galling, with the presence of only a few galls (occupying approx. 1% of leaf area) compromising gas-exchange across the entire leaf. In contrast to these extreme impacts on the leaves of adult trees, galls had no detectible effect on the gas-exchange of maple saplings, implying large ontogenetic differences in host tolerance to mite galling. We also found a significant negative correlation between canopy tree radial increment growth and levels of mite galling. Increased galling levels and higher physiological susceptibility in older canopy trees thus suggest that gall-inducing mites may be major drivers of “age-dependent” reductions in the physiological performance and growth of older trees.
KeywordsAcer saccharum Eriophyoid mite Galls Herbivory Ontogeny Gas-exchange
We thank Haliburton Forest & Wildlife Reserve for their support with funding and field logistics, and Y. S. Hossain, J. Colgan, M. Luksenberg, S. Shujah, I. Nikoloska, and A. Karve for their technical assistance. F. Beaulieu confirmed the identification of V. aceriscrumena. Voucher specimens have been placed in the Canadian National Collection of Insects, Arachnids, and Nematodes (Ottawa, Canada).
- Fay PA, Hartnett DC, Knapp AK (1993) Increased photosynthesis and water potentials in Silphium integrifolium galled by cynipid wasps. Oecologia 93:114–120Google Scholar
- Field CB (1991) Ecological scaling of carbon gain to stress and resource availability. In: Mooney HA, Winner WE, Pell EJ (eds) Integrated responses of plants to stress. Academic Press, San Diego, pp 35–65Google Scholar
- Jeppson LR, Keifer HH, Baker EW (1975) Mites injurious to economic plants. University of California Press, BerkleyGoogle Scholar
- Kozlowski TT, Ward RC (1957) Seasonal height growth of deciduous trees. For Sci 3:168–174Google Scholar
- Lewis SL, Lopez-Gonzalez G, Sonke B, Affum-Baffoe K, Baker TR, Ojo LO, Phillips OL, Reitsma JM, White L, Comiskey JA, Djuikouo MN, Ewango CEN, Feldpausch TR, Hamilton AC, Gloor M, Hart T, Hladik A, Lloyd J, Lovett JC, Makana JR, Malhi Y, Mbago FM, Ndangalasi HJ, Peacock J, Peh KSH, Sheil D, Sunderland T, Swaine MD, Taplin J, Taylor D, Thomas SC, Votere R, Woll H (2009) Increasing carbon storage in intact African tropical forests. Nature 457:1003–1007PubMedCrossRefGoogle Scholar
- Mattson WJ, Addy ND (1975) Phytophagous insects as regulators of forest primary production. Science 190:515–522Google Scholar
- R Development Core Team (2009) R: a language and environment for statistical computing. R Foundation for Statistical Computing, ViennaGoogle Scholar
- Santos JC, Fernandes GW (2010) Mediation of herbivore attack and induced resistance by plant vigor and ontogeny. Acta Oecol 36:617–625Google Scholar
- Welter SC (1989) Arthropod impact on plant gas exchange. In: Bernays EA (ed) Insect–plant interactions. CRC, Boca Raton, pp 135–150Google Scholar