{"refrec":{"BRefID":391924,"RR":"<b>McPeek, M.A.</b> (1998). The consequences of changing the top predator in a food web: a comparative experimental approach. <i>Ecol. Monogr. 68(1)</i>: 1-23. <a href=\"https://dx.doi.org/10.1890/0012-9615(1998)068[0001:tcoctt]2.0.co;2\" target=\"_blank\">https://dx.doi.org/10.1890/0012-9615(1998)068[0001:tcoctt]2.0.co;2</a>","BEntID":389676,"PublicFlag":1,"CheckedFlag":0,"wosflag":1,"vabbflag":0,"RefStringPartII":". <i>Ecol. Monogr. 68(1)</i>: 1-23. <a href=\"https://dx.doi.org/10.1890/0012-9615(1998)068[0001:tcoctt]2.0.co;2\" target=\"_blank\">https://dx.doi.org/10.1890/0012-9615(1998)068[0001:tcoctt]2.0.co;2</a>","DocTypID":8,"DocType":"Journal article","MarineFlag":1,"FreshFlag":0,"BrackishFlag":0,"TerrestrialFlag":0,"Authorstring":"McPeek, M.A.","OrigTitleTranslFlag":0,"Authorstringtrunc":"McPeek, M.A.","Englishabstract":"Changing the top predator in a food web often results in dramatic changes in species composition at lower trophic levels; many species are extirpated and replaced by new species in the presence of the new top predator. These shifts in species composition also often result in substantial alterations in the strengths of species interactions. However, some species appear to be little affected by these changes that cause species turnover at other positions in the food web. An example of such a difference in species responses is apparent in the distributions of coenagrionid damselflies (Odonata: Zygoptera) among permanent water bodies with and without fish as top predators. <i>Enallagma</i> species segregate between ponds and lakes that do and do not support fish populations, with each lake type having a characteristic <i>Enallagma</i> assemblage. In contrast, species of <i>Ischnura,</i> the sister genus to <i>Enallagma,</i> are common to both fish and fishless ponds and lakes. Previous research has shown that <i>Enallagma</i> species segregate because they are differentially vulnerable to the top predators in each lake type: dragonflies in fishless lakes and fish in fish lakes. This paper reports the results of a series of laboratory and field experiments quantifying the mortality and growth effects of interactions in the food webs surrounding <i>Enallagma</i> and <i>Ischnura</i> species in both lake types. These results are compared to determine how features of the food web change to force segregation of <i>Enallagma</i> species between the lake types but permit <i>Ischnura</i> species to inhabit both.The results of experiments conducted in a fishless lake show that damselflies are not food limited in this lake type, but that they do strongly compete via interference mechanisms. Interference effects between the genera are symmetrical. <i>Ischnura</i> species have substantially higher growth rates than <i>Enallagma</i> species under all conditions in fishless lakes. Although both <i>Enallagma</i> and <i>Ischnura</i> experience substantial mortality from predation by dragonflies (<i>Anax</i> and <i>Aeshna</i> species, the top predators in fishless lakes), these dragonflies display a significant bias towards feeding on <i>Ischnura.</i> Mortality rates due to dragonfly predation are not density dependent. The results of experiments done in a fish lake indicate that damselflies are food limited and thus compete for resources in fish lakes. <i>Ischnura</i> growth rates are also substantially higher than <i>Enallagma</i> species in the fish-lake system. Dragonfly species that coexist with fish (<i>Basiaeschna</i> and <i>Epitheca</i> species) do not impose significant mortality on coexisting damselflies, but they do compete for resources with the damselflies, and they may also generate feeding interference in the damselflies. Fish impose significantly higher mortality on <i>Ischnura</i> species than on coexisting <i>Enallagma</i> species, and this mortality is negatively density dependent.The coexistence of <i>Enallagma</i> and <i>Ischnura</i> species is fostered in both lake types by trade-offs in their abilities to avoid predators and to utilize resources. Native <i>Enallagma</i> species are better at avoiding coexisting predators in each lake type, but these abilities come at the expense of the ability to utilize resources effectively and to avoid the predator found in the other lake type. In contrast, <i>Ischnura</i> are better at utilizing resources in both lake types, but these abilities come at the expense of effectively avoiding both fish and dragonflies. Understanding the trade-offs faced by species at similar trophic positions within a food web is critical to predicting changes in food webs following major environmental perturbations such as changing the top predator.","AbstractOtherLang":null,"BibLvlCode":"AS","StandardTitle":"The consequences of changing the top predator in a food web: a comparative experimental approach","OrigTitleLangCode":"en","OrigTitleLangCodeExtended":"eng","OrigTitleLangID":15,"DateLastModified":{"date":"2026-04-23 01:33:29.369830","timezone_type":1,"timezone":"+02:00"},"UserAccessRight":null,"UserAccID":null,"AuthorKeywords":"coexistence; community structure; density dependence; Enallagma; food limitation; food web; Ischnura; resource competition; trade-offs; trophic structure.","OtherDescriptors":null,"Notes":null,"AnaPub":1998,"MonPub":null,"DateUpdate":"2024-04-15","DateCreate":"2024-04-15","SecASFANote":null,"ConfID":null,"PeerRev":1,"VlizCoreFlag":1,"WoScode":null,"VABBcode":null,"OpenAcc":0,"DOI":"10.1890/0012-9615(1998)068[0001:tcoctt]2.0.co;2"},"refs":null,"anarec":{"AnaID":391924,"PubliDate":1998,"Pagination":"1-23","XtraPublOfAnaID":null,"ISBN":null,"Volume":"68","Issue":"1","BRefMon":null,"BRefMonRR":null,"BRefXtra":null,"BRefXtraRR":null,"SerBRefID":42624,"SerRR":"Ecological Monographs. 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