Aquatic Invasions (2015) Volume 10, Issue 3: 339–346 doi: http://dx.doi.org/10.3391/ai.2015.10.3.09 Open Access © 2015 The Author(s). Journal compilation © 2015 REABIC Research Article Complex interactions between native and invasive species: investigating the differential displacement of two topminnows native to Nebraska David A. Schumann1a*, W. Wyatt Hoback1b and Keith D. Koupal2 1University of Nebraska at Kearney, Department of Biology, 2401 11th Avenue, Kearney, Nebraska 68849, USA 2Nebraska Game and Parks Commission, Kearney Field Office, 1617 1st Avenue, Kearney, Nebraska 68847, USA aCurrent address: Natural Resource Management, South Dakota State University, Box 2140B, SNP 138, Brookings, South Dakota 57007-1696, USA bCurrent address: Entomology and Plant Pathology, Oklahoma State University, 127 Noble Research Center, Stillwater, Oklahoma 74078-3033, USA *Corresponding author E-mail:
[email protected] Received: 7 July 2014 / Accepted: 23 March 2015 / Published online: 7 April 2015 Handling editor: Kit Magellan Abstract The establishment of nonnative species and subsequent replacement of native species is among the greatest threats to freshwater biodiversity worldwide. However, little is known of the effects that invasive species have on individual species and specific mechanisms by which species displacement occurs. The expansion of western mosquitofish Gambusia affinis beyond its native range has commonly been thought to cause shifts in species assemblages throughout the United States. Although plains topminnow Fundulus sciadicus populations have declined as the range of western mosquitofish in Nebraska has expanded, long-term co-existence of mosquitofish with the closely related northern plains killifish Fundulus kansae has been observed within the same systems.