McCallum, Anna W. Title

225 Pages·2011·3.11 MB·English

Decapod crustacean diversity along Australia’s 
western continental margin 

Anna W. McCallum

May 2011

Submitted in total fulfillment
of the requirements of the degree of
Doctor of Philosophy

DEPARTMENT OF ZOOLOGY
FACULTY OF SCIENCE
THE UNIVERSITY OF MELBOURNE

Abstract 
A challenge for biodiversity conservation on continental margins is the lack of
information on species distributions. Australia has an expansive continental margin that
is largely unexplored. To protect and manage biodiversity in Australia’s deep marine
environments, biological and abiotic surrogates have been used to classify biodiversity.
The aim of this thesis is to describe patterns of decapod diversity on an extensive
continental margin and investigate the ability of physical and biological surrogates to
represent underlying diversity patterns. The description of biological patterns at large
spatial scales requires reliable taxonomic identifications, and consequently a substantial
part of the thesis is taxonomic in nature.
Surveys of Australia’s western continental margin (~100 to 1000 m depths) were
undertaken in 2005 and 2007 by CSIRO Marine and Atmospheric Research in
conjunction with museum taxonomists. Species identified from the north-west margin
(survey SS05/2007) are reported here and the results of both surveys are summarised. In
total, 890 provisional species of decapod crustaceans were discovered during the two
surveys, of which 30% are new to science. Many of the species collected and identified
(327 or 37%) are known to occur elsewhere, from the tropical Indian Ocean to the West
Pacific, and 142 species were recorded in Australia for the first time.
A small component of the new fauna discovered during the surveys is described here.
These include two new species of the hippolytid shrimp genus Lebbeus and six new
species of squat lobster of the family Chirostylidae. Although 45 species of Lebbeus
exist worldwide, only one had previously been described from Australia. Squat lobsters
including those of the family Chirostylidae are rapidly advancing our understanding of
deep-sea environments across broad spatial scales and therefore the taxonomy and
distribution of these animals is a research priority. In addition to the six new species
described, seven new records of Indo-West Pacific species are reported for Australia.
This study increases the number of chirostylid species in Australia from 40 to 53. Keys
to Australian species of the genera Gastroptychus, Uroptychodes and Uroptychus are
provided.
The distributional records of decapods along the margin were used to determine the
relative importance of environmental and spatial predictor variables on both species
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richness (alpha diversity) and species turnover. The best predictors of species turnover
were temperature, oxygen and salinity, factors that reflect the oceanographic features
that dominate distinct depth bathomes along the slope. On both the shelf and the upper
slope, I differentiated an assemblage north of 22ºS from another south of 23ºS in the
vicinity of North-west Cape. This location correlates with changes in oxygen
concentration along the margin and marks the head of the Leeuwin Current system. The
number of species within samples was highly variable, but a small significant increase
in diversity towards the tropics was evident. On the shelf edge (~100 m) temperature
was correlated with latitude, oxygen and salinity, and thus the independent effects of
each variable could not be separated. On the shallow upper slope (~400 m) temperature
was disassociated from latitude, and latitude proved to be the best predictor of sample
species richness. The predictive power of latitude over other variables indicates that
proximity to the highly diverse Indo-West Pacific is important.
Management of both terrestrial and marine environments often uses vertebrates as a
surrogate for the diversity of the overall fauna, as their distributions are better
documented than those of most invertebrates. In the case of Australia’s deep-water
marine planning, the distributions of fishes were used to classify bioregions. To ensure
this classification represents underlying biodiversity, the spatial patterns of fishes with
three invertebrate taxa were compared along a latitudinal gradient. Changes in
community structure along the margin were broadly congruent for fishes and all
invertebrate taxa. In contrast, broad-scale species richness patterns differed between
major taxa, leading to the conclusion that one taxonomic group cannot be taken to
represent others in terms of species richness or taxonomic distinctness.
The results of this thesis lend support to Australia’s marine planning framework in
which bioregions are defined according to the distributions of fishes and major
oceanographic features. As in other large-scale studies which seek to examine the
drivers of diversity in the deep sea, attributing causal relationships is difficult as many
covariates are correlated. However, it was possible to distinguish some variables which
have greater explanatory power than others. Future research will invariably consider the
distributions of fauna over much larger scales as biological and environmental datasets
are assembled at global scales, and this may help to explain the physical and historical
constraints of deep-sea distributions.
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Declaration 

This is to certify that

(i) The thesis comprises only my original work towards the Ph.D.

(ii) Due acknowledgement has been made in the text to all other material used.

(iii) The thesis is less than 100,000 words in length.

Anna McCallum
May 2011
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Preface 
This thesis was prepared as a collection of publications. Each data chapter (Chapters 2
to 6) constitutes an independent paper. Therefore, there may be some repetition between
chapters; however this has been avoided where possible.
These publications have been prepared in co-authorship. However, the contents of these
chapters are my own work, except where outlined below. Co-authorship reflects a
supervisory role in some cases (Gary Poore), and the result of collaboration in other
instances. The decapods collected from south-west Australia in 2005, which form a
significant component of the data used in Chapter 5 and 6, were identified by Gary
Poore and myself. Chapter 6 uses data provided by a number of collaborators: Alan
Williams provided data on fishes, Magdalena Blazewicz-Paszkowycz identified the
tanaidaceans, and Tim O’Hara provided data on echinoderms. The identifications of
caridean shrimps and hermit crabs listed in Chapter 2 were completed with assistance
from Caroline Farrelly and Skipton Woolley. Other identifications by expert
taxonomists are acknowledged in the text of the chapter. Some abiotic data used in
Chapter 5 were provided by CSIRO and Geoscience Australia. Franzis Althaus of
CSIRO facilitated the use of abiotic data and provided advice on its interpretation. Tim
O’Hara assisted with interpolation of the abiotic data in Chapter 5 and provided advice
on the analyses in this chapter.
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Acknowledgements 
I wish to thank my supervisors, Gary Poore and Michael Keough, for their support and
advice, and for reading and commenting on drafts of this thesis. I would especially like
to thank Gary Poore who introduced me to crustacean taxonomy, and who has
supported me when my PhD continued into his retirement.
I would like to thank Tim O’Hara who provided advice throughout my thesis,
commented on drafts of chapters, and provided a database to manage the large quantity
of data. I am grateful to Alan Williams and Franzis Althaus of CSIRO for their
collaboration on the sixth chapter of this thesis. Thanks also to Adnan Mousalli for
statistical advice in the fifth chapter.
Thanks to my fellow students and colleagues at Museum Victoria for their friendship
and support. Thanks especially to Robin Wilson for a steady supply of biscuits and
encouragement, and to Joanne Taylor and Liz Greaves for proof reading and comments.
Thanks to the Keough Lab (University of Melbourne) for discussions and advice.
This research was supported by a Melbourne Research Scholarship funded by the
University of Melbourne. Support was also provided by the Commonwealth
Environment Research Facilities (CERF) Marine Biodiversity Hub, which is a
collaborative partnership between the University of Tasmania, CSIRO Wealth from
Oceans Flagship, Geoscience Australia, Australian Institute of Marine Science and
Museum Victoria. Attendance at conferences, including the 2008 World Conference on
Marine Biodiversity (Valencia, Spain), was funded by the University of Melbourne
(Melbourne Abroad Travelling Scholarship and Drummond Award), the CERF Marine
Biodiversity Hub, and the Museum Victoria 1854 Student Scholarship. Funding for
research surveys was provided by CSIRO Wealth from Oceans Flagship, and the
Department of Water, Environment, Heritage and the Arts, and completed with the
assistance of staff from Australia’s Marine National Facility.
Finally, I would like to thank my family and friends for their encouragement, and their
interest in my work. To Lach especially, who always kept me happy and on an even
keel.
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