Ecological equivalency as a tool for endangered species management

Christopher Searcy, Hilary B. Rollins, H. Bradley Shaffer

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


The use of taxon substitutes for extinct or endangered species is a controversial conservation measure. We use the example of the endangered California tiger salamander (Ambystoma californiense; CTS), which is being replaced by hybrids with the invasive barred tiger salamander (Ambystoma mavortium), to illustrate a strategy for evaluating taxon substitutes based on their position in a multivariate community space. Approximately one-quarter of CTS ' s range is currently occupied by "full hybrids" with 70% nonnative genes, while another one-quarter is occupied by "superinvasives" where a specifi c set of 3/68 genes comprising 4% of the surveyed genome is nonnative. Based on previous surveys of natural CTS breeding ponds, we stocked experimental mesocosms with fi eld-verifi ed, realistic densities of tiger salamander larvae and their prey, and used these mesocosms to evaluate ecological equivalency between pure CTS, full hybrids, and superinvasives in experimental pond communities. We also included a fourth treatment with no salamanders present to evaluate the community effects of eliminating Ambystoma larvae altogether. We found that pure CTS and superinvasive larvae were ecologically equivalent, because their positions in the multivariate community space were statistically indistinguishable and they did not differ signifi cantly along any univariate community axes. Full hybrids were ecologically similar, but not equivalent, to the other two genotypes, and the no-Ambystoma treatment was by far the most divergent. We conclude that, at least for the larval stage, superinvasives are adequate taxon substitutes for pure CTS and should probably be afforded protection under the Endangered Species Act. The proper conservation status for full hybrids remains debatable.

Original languageEnglish (US)
Pages (from-to)94-103
Number of pages10
JournalEcological Applications
Issue number1
StatePublished - Jan 1 2016
Externally publishedYes


  • Ambystoma californiense
  • California tiger salamander
  • Community composition
  • Ecological similarity
  • Endangered species management
  • Mesocosm
  • Superinvasives
  • Taxon substitution

ASJC Scopus subject areas

  • Ecology


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