title: Are microbes fundamentally different than macroorganisms? Convergence and a possible case for neutral phenotypic evolution in testate amoeba (Amoebozoa: Arcellinida).
abstract: This study reveals extensive phenotypic convergence based on the non-monophyly of genera and morphospecies of testate (shelled) amoebae. Using two independent markers, small subunit ribosomal DNA (ssu-rDNA) and mitochondrial cytochrome oxidase I (COI), we demonstrate discordance between morphology and molecules for 'core Nebela' species (Arcellinida; Amoebozoa). Prior work using just a single locus, ssu-rDNA, also supported the non-monophyly of the genera Hyalosphenia and Nebela as well as for several morphospecies within these genera. Here, we obtained COI gene sequences of 59 specimens from seven morphospecies and ssu-rDNA gene sequences of 50 specimens from six morphospecies of hyalosphenids. Our analyses corroborate the prior ssu-rDNA findings of morphological convergence in test (shell) morphologies, as COI and ssu-rDNA phylogenies are concordant. Further, the monophyly of morphospecies is rejected using approximately unbiased tests. Given that testate amoebae are used as bioindicators in both palaeoecological and contemporary studies of threatened ecosystems such as bogs and fens, understanding the discordance between morphology and genetics in the hyalosphenids is essential for interpretation of indicator species. Further, while convergence is normally considered the result of natural selection, it is possible that neutrality underlies phenotypic evolution in these microorganisms.
authors.affiliation: Department of Biological Sciences Smith College Northampton, MA 01063, USA.
authors.forename: Angela M
authors.initials: AM
authors.lastname: Oliverio
authors.affiliation: Department of Zoology, Institute of Biosciences University of São Paulo São Paulo 05508-090, Brazil.
authors.forename: Daniel J G
authors.identifier: 0000-0002-1049-0635
authors.initials: DJ
authors.lastname: Lahr
authors.affiliation: Department of Biological Sciences Smith College Northampton, MA 01063, USA.
authors.forename: Jessica
authors.initials: J
authors.lastname: Grant
authors.affiliation: Department of Biological SciencesSmith CollegeNorthampton, MA 01063, USA; Graduate Program in Organismic and Evolutionary BiologyUniversity of MassachusettsAmherst, MA 01003, USA.
authors.forename: Laura A
authors.initials: LA
authors.lastname: Katz
keywords: arcellinida; convergence; cryptic species; sex; testate amoebae; tubulinea