title: Colonisation of toxic environments drives predictable life-history evolution in livebearing fishes (Poeciliidae).
abstract: New World livebearing fishes (family Poeciliidae) have repeatedly colonised toxic, hydrogen sulphide-rich waters across their natural distribution. Physiological considerations and life-history theory predict that these adverse conditions should favour the evolution of larger offspring. Here, we examined nine poeciliid species that independently colonised toxic environments, and show that these fishes have indeed repeatedly evolved much larger offspring size at birth in sulphidic waters, thus uncovering a widespread pattern of predictable evolution. However, a second pattern, only indirectly predicted by theory, proved additionally common: a reduction in the number of offspring carried per clutch (i.e. lower fecundity). Our analyses reveal that this secondary pattern represents a mere consequence of a classic life-history trade-off combined with strong selection on offspring size alone. With such strong natural selection in extreme environments, extremophile organisms may commonly exhibit multivariate phenotypic shifts even though not all diverging traits necessarily represent adaptations to the extreme conditions.
authors.affiliation: Department of Biological Sciences & W. M. Keck Center for Behavioral Biology, North Carolina State University, 127 David Clark Labs, Raleigh, NC, 27695-7617, USA; Department of Animal and Plant Sciences, University of Sheffield, Sheffield, S10 2TN, UK.
authors.forename: Rüdiger
authors.initials: R
authors.lastname: Riesch
authors.forename: Martin
authors.initials: M
authors.lastname: Plath
authors.forename: Ingo
authors.initials: I
authors.lastname: Schlupp
authors.forename: Michael
authors.initials: M
authors.lastname: Tobler
authors.forename: R
authors.initials: R
authors.lastname: Brian Langerhans
mesh_terms: D000818:Animals; D005075:Biological Evolution; D049628:Body Size; D052284:Clutch Size; D005260:Female; D005298:Fertility; D006862:Hydrogen Sulfide / Q000633:toxicity*; D011036:Poecilia / Q000502:physiology*; D011247:Pregnancy
chemical_list: D006862:Hydrogen Sulfide
keywords: Divergent natural selection; Gambusia; Poecilia; ecological speciation; extreme environments; life-history evolution; phenotypic convergence; replicated evolution