Sunday, 27 March 2016

Placentation in bovids: can we learn more?

Princeton University Press 2016 ISBN-13: 9780691167176
Field guide or doorstopper? Just published as a Princeton Field Guide, this tome runs to 664 pages and weighs 1.3 kg. It aims to be, "The first comprehensive field guide to all 279 bovid species." Where did that total come from when Mammal Species of the World recognizes half the number?

Johns Hopkins University Press 2011 ISBN-13: 978-1421400938
The answer is the above book on ungulates (hoofed mammals) with a revised taxonomy based on the authors' Phylogenetic Species Concept (PSC). A useful comparison between old and new species can be found at the ultimateungulate site. 

Ungulate Taxonomy was criticised by Frank E. Zachos and colleagues both in a letter to Nature (here) and in a detailed critique (here). They argued that splitting of species was a worrying trend with unfortunate implications for conservation efforts.

Bovid placentation

I bought both these books because bovid placentation deserves further study. Two major clades are recognized. Bovinae include domestic cattle (Bos taurus) and the zebu (B. indicus) - the latter was raised to species status by Groves and Grubb, which should please my Brazilian colleagues.

Antilopinae is less well studied although it does include domestic sheep (Ovis aries). A large amount of antelope material is available in The Harland W. Mossman Collection together with detailed field notes by the principal collector Archie S. Mossman.
Placenta of a klipspringer (Oreotragus oreotragus) with a binucleate cell
From Comparative Placentation courtesy of Dr. Kurt Benirschke

There is much to be done. And which of the rival terminologies should we use? I chose this rather fuzzy image of a klipspringer because Groves and Grubb chose to split it into no less than 11 species. Zachos et al. call this, "a prime example of rash taxonomic conclusions derived from inappropriate data." Even if their judgement is too harsh, the fact remains that this San Diego Zoo specimen cannot be assigned with confidence to any one of those  11 species. We might be on better ground with the Mossman material as it was collected in the wild at known localities and many of the "new" species have clearly defined (often restricted) ranges.
Placentome of a sable antelope (Hippotragus niger)
From Comparative Placentation courtesy of Dr. Kurt Benirschke
Hradecky wrote several papers on placentation in antelopes based mainly on the Mossman material and partly on specimens supplied by Benirschke (e.g. here). A set of his slides is in the Mossman Collection and some reproduced on the Benirschke web site.

Handbook of the Mammals of the World

PSC may be a valid taxonomic approach inasmuch as the premisses are defined and understood by experts. But there was renewed controversy when the Groves and Grubb taxonomy was incorporated in Volume 2 of Handbook of the Mammals of the World. Heller et al. (here) criticised PSC and concluded, "Conveying the message to the public that global diversity is on the decrease ... is unnecessarily confounded when the number of bovid species has just doubled without sufficient justification."

Perhaps the same criticism could be levelled at the new field guide. It does, however, have the virtue of supplying an illustrated version of Groves and Grubb - a book that was strangely lacking in pictures (as noted here). Trophy Hunters will find it a useful aid to bagging yet more species.



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