Am. Midi. Nat. (2013) 169:345-353
Laboratory Competition Hierarchies between Potentially Invasive Rusty Crayfish (Orconectes rusticus) and Native Crayfishes of Conservation Concern KAREN SZELA AND WILLIAM L. PERRY'""^
Department of Biolo^cal Sciences, Behavior, Ecology, Evolution and Systematics Section, Illinois State University Normal 61790-4120
ABSTRACT.—Introduced crayfishes represent a serious threat to the endangered aquatic fauna of North America and Europe. We used small-scale competition assay experiments to examine competitive hierarchies in the laboratory between male and female Orconectes rusticus and Orconectes illinoiensis, Orconectes indianensis, and Orconectes placidus from southern Illinois.
These species are considered threatened in Illinois and there is a potential for O. rusticus to become established in drainages inhabited by these species. Using sex and size-matched laboratory competition trials for a limited food resource, we found that both male and female O. rusticus were competitively dominant to O. placidus, O. illinoiensis and O. indianenús (P < 0.05). Male 0. placidus, O. illinoiensis, and O. indianensis áhpXsyeA no competitive hierarchies (P > 0.05). Eemale 0. placidus viere, however, competitively dominant to O. illinoiensis which was dominant to O. indianensis (P < 0.05). These simple laboratory competition experiments have been used to explore competition hierarchies involved in both North American and European crayfish invasions to understand observed and potential invasion success. These experiments, although presenting only one small aspect of the many mechanisms involved in the invasion and displacement of a resident species, can aid in predicting the potential effects of introduced species prior to an introduction. Our work indicates that the invasion of O. rusticus could have negative consequences for native crayfish species in southern Illinois.
INTRODUCTION
Introduced species can lead to extirpation of resident crayflshes and alter the biodiversity of other components of stream food webs (Charlebois and Lamberti, 1996; Olden et al, 2006). Crayfish invasions have occurred within North America and around the globe (Lodge et al, 2000; Olden et al, 2006; Holdich et al, 2009), and are often facilitated by the bait trade (Taylor et al, 1996). In many lakes and streams of the northeastern United States and southern Canada, where the rusty crayfish Orconectes rusticus has been introduced, resident species have been driven locally extinct (Buuer and Stein, 1985; Olden et al, 2006). A wide range of factors can influence the outcome of crayfish invasions. The successful extirpation of resident species Orconectes propinquus and O. virilis by O. rusticus has been attributed primarily to the latter's larger body size, faster growth rate, and higher fecundity (Hill et al, 1993). Orconectes rusticus is also less susceptible to prédation than resident crayfishes due to larger chelae (Roth and Kitchell, 2005). Other North American crayfishes, e.g., Procambarus clarkii and Padfastacus leniusculus, have been introduced into Europe an are vectors of the crayfish plague, Aphanomyces astad, which infects and kills nonresistant European species in most cases but can also displace resident species through ecological
' Present address: Behavior, Ecology, Evolution and Systematics Section, School of Biological Sciences, Campus Box 4120, Illinois State University, Normal, Illinois 61790-4120. Telephone (309)4388160; FAX (309)438-8160; e-mail:
[email protected] ^ Corresponding author
345
346
T H E AMERICAN MIDLAND NATURALIST
169(2)
mechanisms (Holdich and Domaniewski, 1995; Söderback, 1995; Vorburger and Ribi, 1999). It is important to predict the potential consequences of introduced species before, rather than after, an introduction and laboratory experiments can offer some initial insights into potential species interactions. Laboratory and mesocosm sttidies of competitive hierarchies and prédation sensitivity have been largely consistent with the observed replacement patterns in the field (Garvey et al, 1994; Olsen et al, 1991; Roth and Kitchell, 2005). Laboratory experiments have shown that larger Orconectes rusticus were competitively dominant to smaller O. propinquus for food and shelter, conoborating observed displacement patterns of O. propinquus in northern Wisconsin lakes (Hill and Lodge, 1999). However, there appears to be population level differences within O. virilis such that they are able to coexist with O. rusticus, and laboratory and mesocosm trials examining competition and grovrth rates were consistent with observed patterns in nature (Hayes et al, 2009). Laboratory experiments with Pacifastacus leniusculus, Procambarus clarhii, and several native European crayfishes have shown that the North American species were competitively dominant and posed a significant ecological threat in addition to enabling disease transmission (Vorburger and Ribi, 1999; Gherardi and Daniels, 2004; Gherard, 2006). Plague-free populations of P. leniusculus have been found replacing populations of Astacus astacus and Auslropotamobius pallipes, reaffirming that ecological mechanisms identified in the laboratory may be sufficient for species replacements (Holdich and Domaniewski, 1995; Söderback, 1995). Thus, results from laboratory experiments are often consistent with species replacements in nature, even though they represent only one small mechanism involved in a species invasion and replacement. The objective of this study was to use laboratoiy trials to examine competitive hierarchies in advance of a potential invasion of southern Illinois by Orconectes rusticus. This species inhabits the Wabash and Ohio rivers and has the potential to be introduced into southern Illinois (Nonindigenous Aquatic Species Program, USGS, Gainesville, Fl. 1999). Several state-threatened crayfishes, O. illinoiensis, O. indianensis, O. kentuckiensis, O. stannardi and O. pladdus, currently occupy southern Illinois streams and are considered at risk of extinction (Page, 1985). If O. rusticus expands its range into this region, the potential for negative interactions between the species is possible. It is also possible that the spread of resident crayfishes in southern Illinois as bait could lead to local extinctions. We utilized methods previously used to elucidate the competitive hierarchies among these crayfish species, and, because the native species are ecologically similar to O. propinquus, we hypothesized O. rusticus would be competitively dominant to the crayfishes of southern Illinois: O. illinoiensis, O. indianensis and O. pladdus, in size-matched competition trials for food. METHODS
Grayfishes from southern Illinois used in the experiment were collected from four Ohio River tributaries in the Shawnee Hills. These streams are predominately first to third order with cobble and boulder substrata with alternating riffles and pools. In May 2001, crayfish were collected randomly in all habitats of several 300 m sections of each stream drainage tising dip nets and hand collection to avoid size bias (Greed, 1994). Orconectes indianensis v/as collected from the Haney Greek drainage and O. illinoiensis was collected from the Big Grand Pierre Greek drainage where they are allopatric. O. pladdus was collected from lower sections of the Big Greek drainage and Hogthief Greek where they overlap slighdy with O. kentuckiensis which is found only in the smaller headwater streams (Fig. 1). All individuals
2013
SzELA & PERRY: COMPETITIVE INTERACTIONS BETWEEN CR,\YFISH SPECIES
347
-|- O. indianensis O O. placid us O. kentuckiensis A O. illinoiensis FIG. 1.—Inset map of Illinois depicts the isolated collection location of crayfishes in southeastern Illinois. Orconectes indianensis in Haney Cr. and O. illinoiensis in Big Grand Pierre Cr. are allopatric; O. plaädus was collected in lower reaches of Big Cr. and Hogthief Cr., while O. kentuckiensis occupies the headwaters reaches
were measured to the nearest millimeter, and juveniles less than 20 mm were released. Male Form I and female crayfish larger than 20 mm were transported to the lab in chilled coolers and each species housed separately in recirculating 150 L aquaria in low densities (
