Intraguild interactions and large-scale population patterns Author(s): Julie Sircom and Sandra J. Walde Source: Journal of the North American Benthological Society, Vol. 28, No. 3 (Sep., 2009), pp. 649 -658 Published by: University of Chicago Press on behalf of the Society for Freshwater Science Stable URL: http://www.jstor.org/stable/10.1899/08-188.1 Accessed: 29-02-2016 17:38 UTC Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at http://www.jstor.org/page/ info/about/policies/terms.jsp JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. Society for Freshwater Science and University of Chicago Press are collaborating with JSTOR to digitize, preserve and extend access to Journal of the North American Benthological Society. http://www.jstor.org This content downloaded from 129.173.74.41 on Mon, 29 Feb 2016 17:38:59 UTC All use subject to JSTOR Terms and Conditions J. N. Am. Benthol. Soc., 2009, 28(3):649–658 ’ 2009 by The North American Benthological Society DOI: 10.1899/08-188.1 Published online: 30 June 2009 Intraguild interactions and large-scale population patterns 1 2 Julie Sircom AND Sandra J. Walde Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada B3H 1C8 Abstract. Competitive interactions, including interference and intraguild predation, occur in many aquatic food webs and influence large-scale patterns of abundance, especially in lentic habitats. In a study of small coastal streams in eastern Canada, we found patterns suggesting that abundances of a predatory invertebrate, Sweltsa onkos (Plecoptera:Chloroperlidae), are influenced by another predator, Rhyacophila vibox (Trichoptera:Rhyacophilidae). Larval densities of the 2 species were inversely correlated, and mortality of larval S. onkos tended to be higher in streams with many R. vibox. Abundance and mortality of a3rd predatory species, Isoperla montana (Plecoptera:Perlodidae), were unrelated to abundances of the other species. Laboratory behavioral observations confirmed that interactions between R. vibox and S. onkos were asymmetrical; high densities of R. vibox led to higher injury and mortality rates and lower growth rates of S. onkos, whereas S. onkos had no effect on R. vibox growth or mortality. Previous work has shown that R. vibox reaches high densities only in streams with few or no fish, and we conclude that the relative abundances of S. onkos and R. vibox in the study streams might be influenced by differences in vulnerability to intraguild and fish predation. Key words: intraguild interactions, competition, behavior, aquatic invertebrates, Rhyacophilidae, Chloroperlidae, Perlodidae, streams. The importance of biotic interactions, such as 2004). Behavioral interference often is observed competition or predation, in structuring stream among predatory invertebrates, and effects include communities has been a point of contention for changes in behavior (avoidance, reduced activity, decades (e.g., Grossman et al. 1982, Creed 2006, reduced foraging) (Elliott 2003b), physical displace- Lepori and Malmqvist 2007). Competition is some- ment from preferred locations (Haden et al. 1999), and times thought to play a relatively minor role in predation (Woodward and Hildrew 2002). streams because of high levels of disturbance (Wagner Relating small-scale species interactions to larger- 2005, Schmera et al. 2007). However, many studies scale patterns of distribution can be challenging have demonstrated density-dependent population (Wiley et al. 1997, Cooper et al. 1998). In general, dynamics linked to resource limitation (Wallace et scaling up is expected to occur when small-scale al. 1999, Rowe and Richardson 2001, Taylor et al. processes are not swamped by phenomena important 2002), competition for nonfood resources (e.g., net- at larger scales, e.g., disturbance, dispersal, or effects building sites for filtering Trichoptera; Lancaster et al. on different life stages (Peckarsky et al. 1997). 1988, Funakoshi 2005), and interference in predatory Intraguild predation (often coupled with fish preda- invertebrates (Hildrew et al. 2004). tion) is an interaction that influences large-scale The many examples of microhabitat and diet distributional patterns in lentic environments. Species partitioning in invertebrates, often enhanced by composition tends to vary in a predictable manner temporal segregation of life cycles, strongly suggest from temporary ponds without large predators, a significant past or current role for interspecific through semipermanent habitats with large predatory competitive interactions in streams. Manipulations of invertebrates, to permanent habitats with fish consumers or their resources have demonstrated (McPeek 1990, Wellborn et al. 1996, Wissinger et al. negative effects of one species on the growth, 1996, 2003, Stoks and McPeek 2003). Species are survivorship, or abundance of another (e.g., Richard- prevented from extending their distributions to more son 1991, Feminella and Hawkins 1995, Slavik et al. permanent habitats by predation (intraguild or fish), or are excluded from less permanent habitats by 1 E-mail addresses: [email protected] intraguild predators or intolerance of abiotic condi- 2 [email protected] tions. Species composition in streams follows a similar 649 This content downloaded from 129.173.74.41 on Mon, 29 Feb 2016 17:38:59 UTC All use subject to JSTOR Terms and Conditions 650 J. SIRCOM AND S. J. WALDE [Volume 28 environmental gradient, from temporary, fishless, cobble on bedrock with scattered boulders and often headwater streams, through permanent reaches stretches of exposed bedrock in some streams. The with fish, with further gradients in fish species streams are prone to spates during heavy rain and at composition depending on stream size or order snowmelt and have greatly reduced water flow in late (Creed 2006). Similar mechanisms might drive tran- summer/early autumn. Five of the 8 streams have sitions in stream invertebrate community composi- resident populations of small brook trout (Salvelinus tion. Stream invertebrates clearly differ in their fontinalis), and one stream also has American eels vulnerability to fish, and good examples of strong (Anguilla rostrata). No other fish species are present. fish effects on invertebrate communities can be found Fish surveys were done in late July and early August (e.g., Gilliam et al. 1989, Meissner and Muotka 2006). 2004 when streams were reduced to small pools Asymmetric intraguild interactions influence distri- connected by limited surface flow. An electroshocker butional patterns, e.g., segregated distributions of 2 was passed through ,20 pools in each sampling predatory caddisflies (Martin 1985) and effects on reach. The pools were small enough that it was foodweb structure by an invasive dragonfly (Wood- unlikely that fish were missed. Fish density was ward and Hildrew 2001). However, we know of no calculated from estimates of pool area, on the basis of example in which a pattern of inverse abundances is length and width. produced by a combination of vulnerability to a top Benthic larval censuses were done in autumn 2004 predator and intraguild interactions. (6–7 November, 18–19 December) and spring 2005 (2– Up to 13 (average 9) species of relatively large 3 April, 28–29 April). Streams were ice-covered from predatory invertebrates, most of which are rare, January through March, and emergence of Sweltsa coexist in small coastal streams in eastern Canada. onkos and I. montana and pupation of R. vibox began in One species, Rhyacophila vibox (Trichoptera:Rhyaco- May. Rhyacophila vibox and I. montana have a philidae), emerges in high numbers only from streams predominantly 1-y life cycle, whereas S. onkos has a without or with very few fish (Sircom and Walde 2-y life cycle. Otherwise, phenologies are similar: 2009). We asked if 2 of the other common and emergence occurs from mid-May through July, eggs widespread members of the predator guild, Sweltsa are laid shortly after emergence, and early instar onkos (Plecoptera:Chloroperlidae) and Isoperla montana larvae can be collected in September. (Plecoptera:Perlodidae), showed patterns of abun- Estimates of larval abundance of the 3 focal species dance and larval mortality that were suggestive of (R. vibox, S. onkos, and I. montana) were obtained by intraguild interactions with R. vibox. We then deter- allowing colonization of mesh bags (,1-cm mesh) mined if growth, mortality, and behavioral responses that each covered ,300 cm2 on the stream bottom. measured in laboratory streams provided mecha- Each bag contained 7 pieces of substrate of standard- nisms that explained field patterns. Our goal was to ized sizes (maximum dimensions: one 14–16 cm, one determine if differences in vulnerability to intraguild 10–12 cm, three 7–10 cm, two 4–6 cm); the smallest predation could explain variation in the distribution and largest stones corresponded to the 25th and 50th and mortality of predatory invertebrates. percentiles of substrate sizes found in the streams. Artificial samplers have well-known sets of advan- Methods tages and disadvantages (Rosenberg and Resh 1993). The important advantages for our study were the Study area and organisms ability to take equivalent samples