Cumacea (Crustacea; Peracarida) of the Antarctic shelf [Elektronische Ressource] : diversity, biogeography, and phylogeny / Peter Rehm

Haake-Xp

Informations

• Publié par: universitat_bremen
• Publié le: 01 janvier 2007
• Nombre de lectures: 18
• Langue: English
• Poids de l'ouvrage: 8 Mo

Extrait

Cumacea (Crustacea; Peracarida)
of the Antarctic shelf – diversity,
biogeography, and phylogeny






















Peter Rehm



Ph. D Thesis
submitted to the faculty 2 (Biology Chemistry)
of the University of Bremen, Germany

Bremen, October 2007



































1. Examiner Prof. Dr. Wolf E. Arntz
Alfred Wegener Institute
University of Bremen


2. Examiner Dr. Sven Thatje
National Oceanography Centre
University of Southampton
CONTENTS

Summary
Zusammenfassung

1 INTRODUCTION 1
1.1 Antarctic peracarid crustaceans...................................................................................... 1
Systematics and morphology ............................................................................................ 1
Ecological importance and evolution.............................................................................. 2
1.2 Antarctic Cumacea............................................................................................................ 3
1.3 Hypotheses and aims of the study .................................................................................... 5
Cumacean phylogeny.......................................................................................................5
Diversity of the Ross Sea...................................................................................................... 5
and speciation of Antarctic Cumacea ............................................................ 5
Aims of the study ................................................................................................................. 6

2 MATERIALS AND METHODS 7
2.1 Study areas........................................................................................................................... 7
2.2 Sampling methods.............................................................................................................. 9
2.3 Morphological studies......................................................................................................... 9
2.4 Molecular genetic methods ............................................................................................ 10
Tissue dissection and DNA extraction ............................................................................. 10
Polymerase chain reaction (PCR) ................................................................................... 10
Primer design...................................................................................................................... 11 Gel electrophoresis.12
DNA purification ................................................................................................................ 12 DNA sequencing 13
2.5 Statistical analysis .............................................................................................................. 14
Faunal communities14 Morphological data..........................................................................................................14
2.6 Phylogenetic analysis........................................................................................................ 14
Correction of DNA sequence .......................................................................................... 14
The Basic Local Alignment Search Tool (BLAST)............................................................. 14
Aligning sequences........................................................................................................... 15 Tree construction ............................................................................................................... 15

3 SYNOPSIS 18
3.1 Cumacean phylogeny18
3.2 Peracarid crustaceans of the Ross Sea .......................................................................... 20
3.3 Origin of Antarctic Peracarida ........................................................................................ 22
History and present state of the Antarctic benthic community.................................. 22
Shallow water – deep-see relationship of Antarctic Peracarida ................................ 24
Faunal linkage to the Subantarctic Magellan Region ................................................. 25
3.4 Peracarid diversity............................................................................................................. 26
3.5 Speciation in the context of Antarctic evolution .......................................................... 27
3.6 patterns in Antarctic Cumacea .................................................................. 29
3.7 Future perspectives.... 32

PUBLICATIONS 33
Publication I............................................................................................................................... 35 n II............................................................................................................................... 44
Publication III............................................................................................................... 55
Pun IV............................................................................................................................. 60 blication V 70
Pun VI............. 79

ACKNOWLEDGEMENTS 88

REFERENCES 90 SUMMARY
SUMMARY

The crustacean order Cumacea belongs to the Peracarida and comprises an
evolutionary old group with conservative morphology. Predominantly bound to soft
bottom habitats in benthic marine environments they show a cosmopolitan distribution.
As other Peracarida they display brood protection; juvenile stages are carried in the
marsupium. It is supposed that the marsupium plays a major role in the success of this
abundant and specious group of Crustacea.
The Peracarida are a dominant group in Southern Ocean benthic communities.
Quantitative investigations of the Ross Sea shelf fauna demonstrated that the
Peracarida contribute 63% to abundance and 50% to biomass. Amphipods dominated
clearly, while different sample sites yielded high dominances by Cumacea, Isopoda,
and Tanaidacea. The recorded number of peracarid species from the Ross Sea is lower
than in other high-Antarctic regions. The present study could show, that cumacean
diversity with respect to species richness resembles that of the Weddell Sea or the East
Antarctic. Species number has now increased from 13 to 34 for the Ross Sea, which
highlights the requirement for choosing the appropriate sampling gear, and continued
‘classical’ taxonomical as well as biogeographical work. With the present study equal
distribution of cumacean species with an affinity to the Magellan region in all high-
Antarctic regions could be demonstrated.
A new species Leucon rossi (see front page) and the subspecies Diastylis
enigmatica rossensis was described from the Ross Sea. Further species from the Ross Sea
showed slight morphological differences to literature. In the context of the discussion
about cryptic speciation these differences might indicate that diversity of Antarctic
cumaceans is likely much higher as currently known. In the present study genetic
differences in the 16S rRNA gene of populations of Leucon antarcticus from the Ross
Sea and the Weddell Sea make clear that these have genetically separated for an
extended period of time. According to the analysis of 16S rRNA data, populations of the
species Leucon intermedius from the Ross Sea and the Weddell Sea belong to the
same species. Genetic diversity of the cytochrome oxidase I (COI) gene of two
caridean decapods supports the concept of circumantarctic species distribution in
marine broadcasters. A broadcasting mode in reproduction seems to favour high gene
flow and homogeneous populations around Antarctica. Contrarily, brooders with
limited capability to disperse over long distances are more likely exposed to
geographic isolation on the Antarctic continental shelf, i.e. in glacial periods, which
favours cryptic speciation patterns and high diversity in these taxa.
The phylogenetic history of cumaceans is obscure as there is almost no fossil
record and derived and primitive characters, which vary within and between families,
distinguish families. Though assumptions about the succession of cumacean families
exist, details are still ambiguous. The present molecular study of mitochondrial 16S rDNA SUMMARY
confirmed the Cumacea as a monophylum with respect to Tanaidacea and Isopoda
with the monophyletic Diastylidae as a basal family. The hypothesis of a derived group
of Cumacea bearing a fused pleotelson was confirmed as well. Furthermore this study
demonstrated that within the family Leuconidae the genus Leucon is paraphyletic,
whereas the subgenus Crymoleucon resolved monophyletic. ZUSAMMENFASSUNG
ZUSAMMENFASSUNG

Die Cumacea gehören zu den Peracariden und sind eine Ordnung der Crustacea.
Diese evolutiv alte Gruppe zeichnet sich durch eine