Current Zoology 57 (5): 630−641, 2011 Received Oct. 14; 2010; accepted Mar. 08, 2011. ∗ Corresponding author. E-mail: burksr@southwestern.edu © 2011 Current Zoology Prime waterfront real estate: Apple snails choose wild taro for oviposition sites Colin H. KYLE 1, 2 , Alexis W. KROPF 2 , Romi L. BURKS 2* 1 Department of Ecology and Evolution, University of Chicago, Chicago, IL 60637, USA 2 Department of Biology, Southwestern University, Georgetown, TX 78626, USA Abstract While difficult to prevent introductions, scientific research can help guide control efforts of exotic, invasive species. South American island apple snails Pomacea insularum have quickly spread across the United States Gulf Coast and few control measures exist to delay their spread. Usually occupying cryptic benthic habitats, female apple snails crawl out of the water to de- posit large, bright pink egg clutches on emergent objects. To help identify the most likely place to find and remove clutches, we conducted four lab experiments to investigate what specific object qualities (i.e. material; shape and height; plant species; natural and artificial) attracted P. insularum females to lay clutches. In our fourth experiment, we specifically examined the relationship between female size and reproductive output. To further understand reproductive output, we quantified experimental clutch chara- cteristics (height above water, dimensions, mass, approximate volume, number of eggs, hatching efficiency). Pomacea insu- larum females laid more clutches on plant material, chose round over flat surfaces and failed to differentiate between tall and short structures. In comparison to a common native plant in the eastern US, Pontederia cordata, snails clearly preferred to lay clutches on a widely distributed exotic, invasive plant (wild taro, Colocasia esculenta). Unexpectedly, smaller snails showed higher overall total fecundity as well as more eggs per clutch than larger snails. Therefore, hand removal efforts of large fe- males may not be enough to slow down clutch production. Collectively, our results indicate that conservationists and managers should search emergent plants for P. insularum clutches carefully to guard against established populations [Current Zoology 57 (5): 630–641, 2011]. Keywords Colocasia, Wild taro, Fecundity, Substrate, Reproduction, Facilitation Stopping the invasion process of exotic invasive species (EIS) begins with preventing the introduction of exotic organisms (Lodge et al., 2006). Although most introductions fail (Kolar and Lodge, 2001), the few that succeed require control measures to lessen their ecological and economic damage (Pimentel et al., 2005). To successfully battle already established EIS populations and detect new introductions, managers and conservationists need to understand the ecology of these biological threats and have access to well-researched, efficient pest population control strategies (Lodge et al., 2006). Recently, new methods for EIS detection have emerged, such as using envi- ronmental DNA to test for the presence of invasive Asian carps (Hypophthalmichthys molitrix or H. nobi- lis) in the Great Lakes (Jerde et al., 2011). However, for most EIS, we do not have the genetic sequences or resources to employ these new high-tech molecular means of detection. Instead, most control efforts must still occur at the ground level. South American apple snails (Ampullariidae) repre- sent a notorious group containing invaders with the ability to disrupt ecosystems (Carlsson et al., 2004), consume substantial amounts of aquatic plants (Qiu and Kwong, 2009), spread disease (Rawlings et al., 2007), and out-compete native species (Morrison and Hay, 2011). Using mitochondrial DNA haplotype compari- sons, scientists recently confirmed the identity of chan- neled apple snail populations along the coast of the Southeastern U.S. (Fig. 1A; Rawlings et al., 2007) and Southeastern Asia (Hayes et al., 2008) as P. insularum (d’Orbigny 1835), the island apple snail− a close rela- tive of another channeled species, the better known golden apple snail P. canaliculata (Lamarck 1828). Although only recently recognized as an environ- mental threat, scientists have documented early impacts of P. insularum which include consumption of native Florida plants (Baker et al., 2010), competition with the native Florida apple snail P. paludosa (Connor et al., 2008; Morrison and Hay, 2011), and the ability to ex- Downloaded from https://academic.oup.com/cz/article/57/5/630/1785829 by guest on 27 October 2023