title: Morphological and molecular diversification of Asian endemic Difflugia tuberspinifera (Amoebozoa, Arcellinida): a case of fast morphological evolution in protists?
abstract: Planktonic arcellinid testate amoebae exhibit a broad-range of morphological variability but it is currently unclear to what extent this variability represents phenotypic plasticity or if it is genetically determined. We investigated the morphology and phylogenetic relationships of three endemic east-asian Difflugia taxa 1) the vase-shaped D. mulanensis, 2) and a spinose and a spineless morphotypes of D. tuberspinifera using scanning electron microscopy and two ribosomal genetic markers (SSU rDNA and ITS sequences). Our phylogenetic analyses shows that all three taxa are genetically distinct and closely related to D. achlora and Netzelia oviformis. The genetic variations between the spineless and spinose morphotypes of D. tuberspinifera were low at the SSU rRNA level (0.4%), but ten times higher at the ITS level (4.5-6%). Our data suggest that the two forms of D. tuberspinifera are sufficiently differentiated in terms of morphology and genetic characteristics to constitute two separate entities and that the presence of spines does not result from phenotypic plasticity due to environmental selective pressure. However further observational and experimental data are needed to determine if these two forms constitute different biological species.
authors.affiliation: Laboratory of Soil Biology, University of Neuchâtel, Rue Emile-Argand 11, 2000 Neuchâtel, Switzerland; Zoology Department, Faculty of Science, Ain Shams University, Cairo, Egypt. Electronic address: fatma.gomaa@gmail.com.
authors.forename: Fatma
authors.initials: F
authors.lastname: Gomaa
authors.affiliation: Aquatic Ecohealth Group, Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China. Electronic address: jyang@iue.ac.cn.
authors.forename: Jun
authors.initials: J
authors.lastname: Yang
authors.affiliation: Laboratory of Soil Biology, University of Neuchâtel, Rue Emile-Argand 11, 2000 Neuchâtel, Switzerland; Jardin Botanique de Neuchâtel, Chemin du Perthuis-du-Sault 58, CH-2000 Neuchâtel, Switzerland.
authors.forename: Edward A D
authors.initials: EA
authors.lastname: Mitchell
authors.affiliation: Marine Biodiversity and Global Change Center, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China.
authors.forename: Wen-Jing
authors.initials: WJ
authors.lastname: Zhang
authors.affiliation: Aquatic Ecohealth Group, Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China; Graduate University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Yu
authors.affiliation: Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences, 2 Gagarin St., 1113 Sofia, Bulgaria.
authors.forename: Milcho
authors.initials: M
authors.lastname: Todorov
authors.affiliation: Laboratory of Soil Biology, University of Neuchâtel, Rue Emile-Argand 11, 2000 Neuchâtel, Switzerland.
authors.forename: Enrique
authors.initials: E
authors.lastname: Lara
mesh_terms: D001208:Asia; D016000:Cluster Analysis; D016054:DNA, Protozoan / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000737:chemistry / Q000235:genetics; D014644:Genetic Variation; D016840:Lobosea / Q000145:classification / Q000235:genetics* / Q000648:ultrastructure*; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D010802:Phylogeny; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D017422:Sequence Analysis, DNA
chemical_list: D016054:DNA, Protozoan; D004275:DNA, Ribosomal; D021903:DNA, Ribosomal Spacer; D012337:RNA, Ribosomal, 18S
keywords: China.; Difflugia tuberspinifera; ITS; Molecular phylogeny; SSU rRNA gene; fast evolution; morphological variation