Decapod crustacean phylogenetics
Edited by Joel W. Martin, Keith A. Crandall, and Darryl L. Felder
Series Crustacean Issues 18, Boca Raton, FL, CRC Press, Taylor & Francis Group, 616 pp., ISBN 13:978-1-4200-9258-5. US$140/£85 (hardback)
This book is a long-awaited publication which appeared in bookshops last year (2009). It comes as a result of a symposium hosted by the Society for Integrative and Comparative Biology and The Crustacean Society in San Antonio, Texas, USA on different aspects of decapod phylogeny.
The volume is divided into five sections comprising many different aspects of decapod crustacean phylogeny by many authors, all with an in-depth knowledge of the subjects. Also, the authors give long lists of up-to-date relevant literature on their particular subject.
1. ‘Overview of decapod phylogeny’
This part is a discussion of the different methods to use to elucidate the phylogeny of various groups of decapod crustaceans. The chapters describe various methods to obtain a phylogeny and how to interpret the results, drawbacks and highlights of the different methods. Molecular methods as well as ‘old school’ morphology are used; also spermatozoa morphology, eyes and visual perception (=optical design), larval morphology, mating systems and evolution of crustacean parasites are described. All are very interesting insights given by the experts as well as providing questions and ideas to take forward.
2. ‘Advances in our knowledge of shrimp-like decapods’
This part deals with swimming ‘shrimp-like’ crustaceans. However, even though the section is called ‘shrimp-like’, it does look mainly into shrimps (Caridea) and prawns (Dendrobranchiata) with the exception of the discussion of the historical term ‘Natantia’. The three articles provide different angles on the subject, but come up with the same result: we know some part of the phylogeny but most is not resolved. I hesitate to mention this, but some of the authors still use the strictly defined word ‘commensal’ in a general and undefined way for all types of shrimp associations that again emphasizes the fact that we need another term or to just use ‘associate’ for these unknown associations! The natural groupings that have been solved are the ones that normally have not given any problems, but more evidence is coming. Within the Dendrobranchiata is the family Penaeidae, a problematic non-monophyletic clade, as are the two superfamilies of the Caridea: Palamonoidea and Alphoidea. Although there will be discussions about the more ‘solved’ clades, the above-mentioned ‘clades’ are in deep need of more knowledge.
3. ‘Advances in our knowledge of the Thalassinidean and lobster-like groups’
In this part more insight is given to those lobster-like crustaceans with more information especially from molecular studies. The results are as always both supportive of the old groupings as well as giving contradictary results in others. This was found, for example, in the debatable Thalassinidea (mono- or paraphyletic) with two clades found (Axiidea and Gebiidea). Although most crustaceans are marine, there are also freshwater groups, and one very important one is discussed in this section, namely the crayfish. In this part the authors try to estimate the divergence time of the different genera of crayfish as well as the phylogeny. The polychelida are discussed for all extant species and the phylogeny using morphology is calculated. Even more, keys to all species and the diagnosis of the genera of the polychelida is given.
4. ‘Advances in our knowledge of the Anomura’
The enigmatic anomura has also been discussed in this book. This chapter describes the various phylogenies set up by different researchers working with this group. Also, new molecular data are used and of the three major recognized clades within anomuea, e.g. Galatheoidea, Paguroidea and Hippoidea, only the Hippoidea seems to be monophyletic. To resolve the major two clades, much more work is needed!
5. ‘Advances in our knowledge of the Brachyura’
The brachyurans are, as the previous anomura, very diverse and this group is also the most species-rich of the decapods, although more uniform in morphology compared with other decapods groups. Within this chapter are many contributions on the different group levels of Brachyura, as for example the section Podotremata and superfamilies as Majoidea down to genera such as Hexapanopeus. Much information of different levels of Brachyura comes from these contributions, but the phylogeny of the Brachyuran crabs is far from resolved. Most works are based on molecular markers. However, due to the lack of major molecular data for the true freshwater crabs, the contribution on those brachyurans combines morphology, biogeography and earlier data in an attempt to resolve this large and largely unknown group. Also a very interesting part is the attempt to bring order within the two superfamilies Portunoidea and Cancroidea with new proposed rearrangements using mitochondrial DNA.
One thing that remains in your mind after reading this book is that in spite of all the efforts of many brilliant scientists, the phylogeny of decapod crustaceans is still far from being resolved, although we are getting closer! One might wonder that the Decapod Crustacea, which contain about 15,000 species and among which are many important aquatic food sources for man of major economic importance, still has an unresolved phylogeny. However, one can hope that this volume will encourage more researchers, both present (researchers of today) and future (today's masters and PhD students), to take up the challenge and begin to work in the wonderful world of Decapod Crustacea. I hope this book will find its way to most people with an interest in crustacea and phylogeny, including both researchers and students.
Matz S. Berggren
Senior Scientist
Institute of Marine Ecology, Gothenburg University
The Sven Lovén Centre for Marine Sciences, Kristineberg, Sweden
Email: [email protected]