Abstract
AbstractA thorough understanding of how communities respond to extreme changes, such as biotic invasions, is essential to manage ecosystems today. Here we constructed fossil food webs to identify changes in Late Ordovician (Katian) shallow-marine paleocommunity structure and functioning before and after the Richmondian invasion, a well-documented ancient invasion. Food webs were compared using descriptive metrics and cascading extinction on graphs models. Richness at intermediate trophic levels was underrepresented when using only data from the Paleobiology Database relative to museum collections, resulting in a spurious decrease in modeled paleocommunity stability. Therefore, museum collections and field sampling may provide more reliable sources of data for the reconstruction of trophic organization in comparison to online data repositories. The invasion resulted in several changes in ecosystem dynamics. Despite topological similarities between pre- and postinvasion food webs, species loss occurred corresponding to a minor decrease in functional groups. Invaders occupied all of the preinvasion functional guilds, with the exception of four incumbent guilds that were lost and one new guild, corroborating the notion that invaders replace incumbents and fill preexisting niche space. Overall, models exhibited strong resistance to secondary extinction, although the postinvasion community had a lower threshold of collapse and more variable response to perturbation. We interpret these changes in dynamics as a decrease in stability, despite similarities in overall structure. Changes in food web structure and functioning resulting from the invasion suggest that conservation efforts may need to focus on preserving functional diversity if more diverse ecosystems are not inherently more stable.
Highlights
Biotic invasions are a leading cause of extinction in modern ecosystems (Eldredge 1992; Lodge 1993; Lockwood and Pimm 1994; Singh 2002; Lockwood et al 2007; Oliver et al 2015); their effects on ecosystem structure and functioning remain poorly understood
The fossil record documents persistent ecosystem dynamics (Aberhan 1994) and can be used to understand how and why ecosystems change in response to perturbations (Jackson et al 2001; Miller et al 2002; Jackson and Erwin 2006; Dzialowski et al 2007; Sperfeld et al 2010; Louys et al 2012; Gray et al 2015; Roopnarine 2018; Tyler and Schneider 2018; Stigall 2019)
All species from field collections were present in museum collections, and 45% of species in museum collections were present in field collections preinvasion, and 72% postinvasion
Summary
Biotic invasions are a leading cause of extinction in modern ecosystems (Eldredge 1992; Lodge 1993; Lockwood and Pimm 1994; Singh 2002; Lockwood et al 2007; Oliver et al 2015); their effects on ecosystem structure and functioning remain poorly understood. Geographic ranges change as species track shifting environments, and interspecific relationships are disrupted as a consequence. These changes have much in common with episodes of biotic interchanges and invasions in the geological past, commonly occurring during previous warming intervals, and are predicted to occur in the near future The fossil record documents persistent ecosystem dynamics (Aberhan 1994) and can be used to understand how and why ecosystems change in response to perturbations (Jackson et al 2001; Miller et al 2002; Jackson and Erwin 2006; Dzialowski et al 2007; Sperfeld et al 2010; Louys et al 2012; Gray et al 2015; Roopnarine 2018; Tyler and Schneider 2018; Stigall 2019). Here, we compare food webs across the Richmondian invasion, a well-documented invasion, to determine its effects on the structure and dynamics of Late Ordovician shallowmarine paleocommunities from the Cincinnati region (USA)
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