Effects of transgenic American chestnut leaf litter on growth and survival of wood frog larvae

Abstract

Biotechnology offers a new approach for the restoration of tree species affected by exotic pathogens; however, nontarget impacts of this novel strategy on other organisms have not been comprehensively assessed. We evaluated the effect of transgenic American chestnut (Castanea dentata) leaf litter on the growth and survival of larval wood frogs (Lithobates sylvaticus), a forest-dwelling amphibian species widely sympatric with American chestnut, that forage almost entirely on periphyton and litter detritus that accumulate in temporary vernal pools in forests. We reared wood frog larvae on Castanea leaf litter (American chestnut genetically engineered for blight tolerance, nontransgenic American chestnut, Chinese chestnut [Castanea mollissima], and an American-Chinese chestnut hybrid) and litter from two non-Castanea, nontransgenic "control" tree species, coupled with two levels of supplementary food. We observed no differences in growth or survival of wood frog larvae reared on transgenic versus nontransgenic American chestnut leaves. Without supplementary food, wood frog larvae provided leaves from American chestnut (both types) developed faster and grew larger than those exposed to other leaf litter treatments. Results of this study provide preliminary evidence that (1) American chestnut may have formerly been an important source of food for forest-dwelling amphibians and (2) transgenic American chestnut litter generated as part of chestnut restoration efforts is unlikely to present direct novel risks to developing amphibian larvae in the forest environment.

Developing Blight-Tolerant American Chestnut Trees

“…The final petition will include an extensive background on the biology and ecology of American chestnut, molecular characterization of the transgenic events, enzyme quantification, blight tolerance assays, growth comparisons, and several ecological studies. Two such ecological studies published recently are a wood frog tadpole experiment observing feeding on chestnut leaf litter (Goldspiel et al 2018) and another examining native seed germination and mycorrhizal root colonization in the presence of transgenic chestnut tissue (Newhouse et al 2018). To date, no significant environmental differences have been found between the transgenic and wild-type American chestnut.…”

Improving Ex Vitro Rooting and Acclimatization Techniques for Micropropagated American Chestnut1

“…Borkh.] on tadpoles (Goldspiel et al 2018), honeybees (Newhouse, in preparation), mycorrhizae (D'Amico et al 2015), native seed germination (Newhouse et al 2018), and other organisms all required plants produced through tissue culture.…”

Transgenic American Chestnuts Do Not Inhibit Germination of Native Seeds or Colonization of Mycorrhizal Fungi

“…Along with the previous mycorrhizal experiments referenced above, collaborators have preliminarily evaluated aquatic and terrestrial insect feeding on transgenic chestnut leaves and natural introgression of plants near field-planted transgenic chestnut trees (unpublished). Additionally, Gray (2015) and Gray and Briggs (2015) compared transgenic and non-transgenic chestnut leaf decomposition, and Goldspiel et al (in press ) tested wood frog tadpole growth and survival with transgenic chestnut leaves. In each of these cases, transgenic chestnuts showed negligible differences compared to non-transgenic American chestnuts, or smaller differences than traditionally-bred hybrid or Chinese chestnuts.…”