Extracts of the invasive shrub Lonicera maackii increase mortality and alter behavior of amphibian larvae

Abstract

Water-soluble phytochemicals produced by invasive plants may represent novel elements of invaded ecosystems that can precipitate a variety of direct and indirect effects on native organisms. Phenolic compounds in particular are a common plant defense, and these compounds may have disproportionate impacts on amphibians compared to other taxa. We coupled an exploration of invasive plant extract effects on larvae of four amphibian species (the salamander Ambystoma maculatum, the toad Anaxyrus americanus, and the frogs Hyla sp. and Lithobates blairi) with behavioral observations designed to determine whether behavior can ameliorate the negative effects of exposure to invasive plant extracts. Larvae were reared in extracts of the widespread invasive Amur honeysuckle (Lonicera maackii), mixed native leaf litter, and a water control. Anaxyrus americanus tadpoles reared in L. maackii extracts were more likely to die than tadpoles reared in native extracts, but differences in mortality following rearing in native and exotic extracts were not significant for the other three species. Anaxyrus americanus and L. blairi tadpoles made more trips to the surface in L. maackii extracts than in native extracts, consistent with the hypothesis that exotic extracts may interfere with respiratory physiology and suggesting that L. blairi can behaviorally ameliorate the negative effects of L. maackii extracts. Our study highlights both a direct and indirect pathway by which invasive plant extracts may alter the ecological dynamics of native fauna.

Seed bank survival of an invasive species, but not of two native species, declines with invasion

“…Lonicera maackii is native to Asia and first introduced to North America in 1897 (Luken and Thieret 1996). The invasion of L. maackii across the eastern and midwestern US is associated with reduced cover (Hutchinson and Vankat 1997), richness, and abundance (Collier et al 2002) of native understory vegetation, as well as important changes in the abundance and behavior of native organisms (Allan et al 2010;Conley et al 2011;Dutra et al 2011;Mattos and Orrock 2010;McKinney and Goodell 2010;Watling et al 2011a). Lonicera maackii invasion may be promoted by the widespread dispersal of its seeds by frugivorous birds (Bartuszevige and Gorchov 2005;Watling and Orrock 2010) and its success in direct competition with understory species (Gorchov and Trisel 2003).…”

Does removal of invasives restore ecological networks? An experimental approach

“…Honeysuckle was first introduced to North America from Asia in the 1800s as an ornamental plant and since then has become a dominant plant in many forest and shrubland systems, particularly in the eastern US (Hutchison and Vankat 1997). Numerous studies have documented the negative consequences of honeysuckle to native plants (Gould andGorchov 2000, Collier et al 2002), animals (Schmidt & Whelan 1999, Watling et al 2011), ecosystem processes (Ehrenfeld et al 2001, Ehrenfeld 2003, ecological services such as pollination (McKinney & Goodell 2010), and even human health (Allan et al 2010).…”

Earthworm, microbial biomass, and leaf litter decay responses after invasive honeysuckle shrub removal from urban woodlands.

“…Conversely, laboratory experiments conducted by Watling et al (2011a) showed that extracts from L. maackii increased mortality in American toad tadpoles and increased surfacing trips by American toad and plains leopard frog (Lithobates blairi) tadpoles. Watling et al (2011b) reported lower amphibian species richness and evenness in forested areas invaded by L. maackii.…”