JOHN A. NOVAK (Professor) Department of Biology, Colgate University Phone: 315.228.7341 Fax: 315.228.7997 E-Mail: JNovak@mail.colgate.edu Research Interests: Animal behavior; environmental studies; invertebrate zoology; tropical ecology. [Details] Teaching Interests: Ecology [Details] Publications Colgate Teaching & Research Directory

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John Novak

Research Interests: 

        Predation tactics of downy woodpeckers and black-capped chickadees on golden rod galls caused by the gall fly Eurosta solidaginis; the significance of immature stages of holometabolous insects in evaluating classification schemes based on adult insects.

        My current research activity centers upon the autecology of the goldenrod gallfly, Eurosta solidaginis, which is a system composed of complex and dynamic evolutionary pressures which provides a model to study fundamental ecological principles.  The goldenrod plant (Solidago altissima and S. gigantea) acts as a host for the parasitic gallfly larva which causes the host plant to produce a spherical gall that encapsulates the larva, thus providing it with a protective environment to develop and overwinter.  While developing inside the gall the larva often falls prey to a number of other parasites and predators.  These enemies attack the gallfly larvae with varying intensities based upon several different ecological factors including gall size, climate and geographical location.  Gall size is a heritable pressure upon the gallfly population, which may drive evolutionary shifts.

        There exist five main natural enemies of the goldenrod gallfly.  There are two wasp parasites, Eurytoma gigantea and a beetle predator Mordellistena unicolor, and two avian predators, primarily Downy woodpeckers (Dendrocopus  pubescens) and occasionally Black-capped chickadees (Parus atricapillus), which feed upon gallfly larva inside the galls.  Recent studies have found Gray squirrels (Sciurus carolinesis) may feed upon gallfly larvae as well.  It has been noted that the wasp E. obtrusiventris and the beetle M. unicolor, attack galls of all sizes due to their predation techniques, E. obtrusiventris, parisitizes the gallmaker larva before the onset of gall formation, while the beetle burrows throughout the stem of the plant to enter the gall.  Thus in each case, there is no opportunity for the predator to discriminate its prey based on its gall size.  On the other hand, it is  known that larvae occupying small galls are more prone to attack by E. gigantea. E. gigantea parasites the gallfly larva by ovipositing an egg into the center chamber of the gall, which hatches and consumes the Eurosta larva. Thus ovipositor length limit E. gigantea to the size of the gall they can penetrate.  Local gallfly populations are examined to compare predation patterns in nature.

 
 

           Figure 2.  Typical gall characteristics following attack, from left to right, by Gray squirrels, Black-capped chickadees and Downy woodpeckers.  Only squirrels severed the galls from the stem.

 
Teaching Interests: Animal behavior, environmental studies, vertebrate biology, Comparative Health Care, China Extended Study

Recent Publications: 

Richard W. Merritt, JoAnna L. Lessard, Kelly J. Wessell, Osvaldo Hernandez, Martin B. Berg, John R. Wallace, John A. Novak, John Ryan, and Brett W. Merritt. 2005. Lack of effects of Bacillus Sphaericus (Vectolex) on nontarget organisms in a mosquito-control program in Southeastern Wisconsin: A 3-year study. Journal of the American Mosquito Control Association. 21(2):201-212.

Merritt. R. W., K. W. Cummins, M. B. Berg, J. A. Novak, M. J. Higgins, K. J. Wessell, J. L. Lessard. 2002.  Development and application of a macroinvertebrate functional group approach in the bioassessment of remnant river oxbows in southwest Florida.  Journal of North American Benthological Society. 21: 290-310.

Shealer, D. A., J. P. Snyder, V. C. Driesback, D. F. Sunderlin and J. A. Novak.  1999.  Foraging patterns of gray squirrels (Sciurus carolinensis) on goldenrod gall insects, a potentially important winter food resource. American Midland Naturalist. 142:102-109.

Novak, J. A. l995. Index in Merritt, R. W. and K. W. Cummins, An Introduction to the Aquatic Insects of North America. Kendall/Hunt Pub. Co. pp.880.

Cowie, R. J. and J. A. Novak. 1990. Incubation patterns of blue tits (Parus caeruleus).  Pages 345-356 in J. Blondel et al., eds. Population Biology of Passerine Birds, Springer-Verlag, New York. ISBN-3-540-51759-6.