Geographic variation in patterns of nestedness among local stream fish assemblages in Virginia

Abstract

Nestedness of faunal assemblages is a multi-scale phenomenon, potentially influenced by a variety of factors. Prior small-scale studies have found freshwater fish species assemblages to be nested along stream courses as a result of either selective colonization or extinction. However, within-stream gradients in temperature and other factors are correlated with the distributions of many fish species and may also contribute to nestedness. At a regional level, strongly nested patterns would require a consistent set of structuring mechanisms across streams, and correlation among species' tolerances of the environmental factors that influence distribution. Thus, nestedness should be negatively associated with the spatial extent of the region analyzed and positively associated with elevational gradients (a correlate of temperature and other environmental factors). We examined these relationships for the freshwater fishes of Virginia. Regions were defined within a spatial hierarchy and included whole river drainages, portions of drainages within physiographic provinces, and smaller subdrainages. In most cases, nestedness was significantly stronger in regions of smaller spatial extent and in regions characterized by greater topographic relief. Analysis of hydrologic variability and patterns of faunal turnover provided no evidence that inter-annual colonization/extinction dynamics contributed to elevational differences in nestedness. These results suggest that, at regional scales, nestedness is influenced by interactions between biotic and abiotic factors, and that the strongest nestedness is likely to occur where a small number of organizational processes predominate, i.show $132#e., over small spatial extents and regions exhibiting strong environmental gradients.

Differences in environmental heterogeneity promote the nestedness of Chironomidae metacommunity in Neotropical floodplain lakes

“…The nested pattern Chironomidae community observed here agrees with Cook et al (2004), which considers the nestedness as the result of the set of species throughout the region being filtered by specific environmental restrictions of each. Thus, the distribution of each taxon between the floodplain lakes is determined by their ability to overcome environmental limitations.…”

Nestedness of desert bat assemblages: species composition patterns in insular and terrestrial landscapes

“…Other potential mechanisms include gradients in species tolerance for habitat variables (Cook et al 2004;Patterson et al 1996) or nested structure of habitat diversity (Calmé and Desrochers 1999; Cutler Table 3 Maximally packed nested matrix of insular bat species on 20 islands in the Gulf of California, Baja California Sur, Mexico. For species codes see Table 2 MYVI NYFE LECU PIHE TABR MYCA NYMA MACA ANPA MOME LAXA EUSP San José 1 1 1 1 1 1 1 1 1 1 1 1 Carmen 1 1 1 1 0 1 1 1 1 1 0 0 San Francisco 1 1 1 1 1 1 1 1 0 0 0 1994).…”

“…Numerous studies have investigated nestedness patterns for a variety of taxa over the past 15 years (Bascompte et al 2003;Bolger et al 1991;Conroy et al 1999;Cook et al 2004;Cook and Quinn 1995;Davidar et al 2002;Fischer and Lindenmayer 2005;Greve et al 2005;Hausdor and Hennig 2003;Kadmon 1995;Martínez-Morales 2005;McAbendroth et al 2005;Meyer and Kalko 2008;Patterson and Atmar 1986;Sfenthourakis et al 2004;Wethered and Lawes 2005;Wright et al 1998;Wright and Reeves 1992). These studies and others suggest nestedness is quite common in faunal assemblages, causing some authors to suggest that absence of nestedness may be more interesting than its presence (Kadmon 1995;Simberloff and Martin 1991).…”

“…Factors influencing species composition may operate at different spatial scales, such that species that are widespread across one scale (e.g., local sites within habitats) could be rare across another scale (e.g., a suite of discrete habitat patches or islands) (Cook et al 2004;Sfenthourakis et al 2004;Wiens 1989). Other studies have shown that nestedness may depend on spatial scale of the analysis (Cook et al 2004;Sfenthourakis et al 2004).…”

“…Other studies have shown that nestedness may depend on spatial scale of the analysis (Cook et al 2004;Sfenthourakis et al 2004). If composition patterns are scale dependent, then the scale of investigation could strongly influence which species are identified as conservation priorities (Hartley and Kunin 2003).…”