Systematics and Evolution, Part A The Mycota

3 Systematics of the Straminipila: Labyrinthulomycota,

Hyphochytriomycota, and Oomycota

GORDONW. BEAKES^1 ,DAISKEHONDA^2 ,MARCOTHINES^3

CONTENTS

I. Introduction.................................. 39

II. Molecular Phylogeny and Systematics...... 41

A. Higher-Level Relationships ............... 41

B. Systematics of Labyrinthulomycota. ...... 41

C. Systematics of Hyphochytriomycota ..... 46

D. Systematics of Oomycota ................. 49

E. Early Diverging Clades: ClassesIncertae

Sedis........................................ 54

1. Eurychasmales .......................... 55


2. Haptoglossales .......................... 55


3. Olpidiopsidales s. lat. ................... 57


4. Haliphthorales .......................... 57
   F. Saprolegniomycetes........................ 58


5. Atkinsiellales............................ 58


6. Leptomitales s. lat. and Related
   Clades.................................... 59


7. Saprolegniales ........................... 59
   G. Peronosporomycetes ...................... 65


8. Rhipidiales .............................. 69


9. Albuginales.............................. 70


10. Peronosporales s. lat. ................... 71
    III. Selected Developmental and Morphological
    Trends......................................... 76
    A. Zoospore Characteristics.................. 76


11. Zoospore Morphology and Flagellar
    Rootlet Organization.................... 76


12. Encystment/Adhesive Vesicles ......... 79

B. Life Histories and Sexual Cycle

Characteristics ............................. 80

IV. Evolutionary Timeline and the

Fossil Record................................. 82

V. Conclusions................................... 84

References..................................... 85

I. Introduction

Osmotrophic fungal-like stramenopiles (as

recognized by Adl et al. 2012 ) are characterized

by their heterokont, predominantly biflagellate,

zoospores (Fig. 3.16). Although well known

from marine and freshwater habitats, these

organisms also are widespread inhabitants of

soils, and many are significant pathogens of

plants and animals. It has long been recognized

that these organisms have many structural and

biochemical characteristics that separate them

from the osmotrophic members of Kingdom

Fungi (see Powell and Letcher 2014 ; James et al.

2014 ). Features such as havingcelluloseas the

main structural polysaccharide in the cell wall,

different pathways forlysine biosynthesis,mito-

chondria withtubular vesiculate cristae,largely

diploidvegetative thalli, and oftenb1-3 glucans

(laminarins) as their main storage carbohydrate

(Dick2001a) set these organisms apart from the

members of Kingdom Fungi/Mycota.

There has been a recent trend to refer to the

osmotrophic stramenopiles traditionally studied by

mycologists as “fungal-analogues” or even as “untrue

fungi” (Moore et al. 2011 ). However, Bartnicki-Garcia

( 1996 ), Dick (2001a), and Money ( 1998 ) have all

eloquently argued that “fungi” should be considered a

biological lifestyle, characterized by osmotrophic

nutrition and yeast-like or hyphoid growth form, rather

than a phylogenetic entity (Kingdom Mycota or Myco-

(^1) School of Biology, Newcastle University, Newcastle upon Tyne
NE1 7RU, United Kingdom; e-mail:[email protected]
(^2) Department of Biology, Faculty of Science and
Engineering, Konan University, 8-9-1, Okamoto, Higashinada,
Kobe, Hyogo 658-8501, Japan; e-mail:[email protected]
(^3) Centre for Integrative Fungal Research (IPF), Biodiversity and
Climate Research Centre (BiK-F), Goethe University Frankfurt
am Main (Department of Biological Sciences, Institute of Ecol-
ogy, Evolution and Diversity), and Senckenberg Gesellschaft
fu ̈r Naturforschung, Senckenberganlage 25, 60325 Frankfurt
am Main, Germany; e-mail:[email protected]
Systematics and Evolution, 2ndEdition
The Mycota VII Part A
D.J. McLaughlin and J.W. Spatafora (Eds.)
©Springer-Verlag Berlin Heidelberg 2014