Book Review

Gloyd, H. K., Conant, R. (1990): Snakesof the Agkistrodon complex - a monographicreview. 1-614, 32 colouredfigs., 20 half-tone plates. Price $75. Societyfor the Study of Amphibiansand Reptiles, Con- tributions to Herpetologyno. 6, Oxford, Ohio.

This is a monographicstudy written on very good paper, and including32 colour plates with eight photos on each, and 20 additionalblack and white plateswith betweentwo and six photos each. Besidesthese there are 60 drawingsand 28 maps. The book givesa very nice and proper impression. It contains an enormous amount of informationand data, and it is not possible,or necessary,to comment on it all here. For any student of these snakes this is a rich source of knowledge. A total number of 34taxa of Agkistrodonand related genera are thoroughlydiscussed, and of these11 have been describedby the authors during the years of work with this group of snakes. Actuallythe two authors have each got one subspeciesnamed after him in credit by the co-author, Agkistrodonbilineatus howardgloydi and A. piscivorusconanti respectively. The book is divided into a number of sectionswhere the major part is devoted to the descriptionsof the differentgenera, species,and subspecies.A major part is devotedto the American speciesof Agkistrodonfor natural reasons. These are the taxa that are most familiar to the authors, and on which the authors have spent most of their time. The number of specimensavailable for examination to the authors vary con- siderably.It is a little bit difficultto see the exact numbers of examined specimensas differentnumbers of individuals are listed in the different character Tables, but A. contortrix(about 2700 specimens)and A. piscivorus( 1200 specimens) are clearlythe best examinedtaxa. A. blomhoffi alsois well represented (well above 300 specimensexamined). A fewspecies (A. bilineatus,A. intermedius,Calloselasma rhodostoma, and Hypnalehyp- nale)are representedby around 100 to 200 specimensin this study while A. caliginosus,A. himalayanus,A. halysand Deinagkistrodonacutus are representedby around 50 or slightlymore specimenseach. The remaining specieshave only been availablein smaller series. About 20 specimensof H. nepa, 18 of A. strauchi,seven of A. monticolaand six of H. wallihave been examined. Also some subspecieshave been availableonly in small numbers. All the differentsubspecies of A. halys(halys, cognatus and caraganus)as well as A. intermedius stejnegeriand A. bilineatushowardgloydi have been examined only in about ten or slightlymore specimens. Agkistrodonaffinis is consideredas Incerta Sedisin this work and it seemsthat the authors do not really con- sider this taxon as valid. When only speciesor subspecieswith such a large range in Asia as A. halysas well as its differentsubspecies only have been availablein comparativelyfew specimenslocal geographicvaria- tion certainly remain hidden and additional taxa will most probably remain undiscovered.This is also the opinion of the authors as is stated in several places in the text. A large sectionof the book is devoted to the Asian taxa, but for politicalreasons it has not been possible for the authors to examine a comparativeamount of museum specimensfrom this part of the world. The material depositedin museums in the USSR and Chine was not availableuntil the last decade or so. The senior author, Gloyd,died 1978and Conant has recentlycelebrated his 80th birthday so there has only been a short of time to use material from these countries. The authors put a deadline for gathering data to December31, 1980for old worldtaxa. However,fortunately Conant continuedto includeinformation pub- lished after that date and this informationhas mainly been includedin a 'Postscript'. This sectionincludes a description of two additional taxa described after the first deadline. The final cut off date was set to December 31, 1986. For me as a Europeanand involvedin studiesof oldworld herpetology one of the very great contributions 424

to our knowledgeof the biologyof the genus Agkistrodonis the work done on the halyslintermediuscomplex and relatedtaxa. These snakeshave at all timescreated much confusionin taxonomy,and speciesdefinitions and borders have been subjectivelydefined in most old literature. Gloyd and Conant have tried to create a proper taxonomyfor this group using new and reevaluatedinterpretations of characters,and come up with a fairly good picture of what the taxonomyand systematicslook like for these snakes. It will definitelyhelp many other students of these snakesin their work when systematizingAsian Agkistrodonin the future. With such a large group and with so many difficultiesin obtaining material, a study like this can never be total or final; as the authors state in their 'Postscript' there are undoubtedly populations and taxa yet to be discoveredand described in remote places. But this work definitelygives a very prospectiveplatform for future studiesof the group. As the authors foresightedlyexpressed it in their own writing - a platform for investigatorsin Asia "to finish the job". The snakesof the genusAgkistrodon illustrates very good examplesof siblingspecies. Snakes mostly recog- nize their own specieson chemicalcommunication such as pheromones,behaviour etc rather than on exter- nal morphology.This does not select for unique colour-patternbut rather for selectiontowards a similar pattern whichwe know as Muellerianmimicry. The morphologicallyvariable subspeciesAgkistrodon h. halys and A. i. intermedius,which have a similardistribution in large areas of central Asia, showan extreme mor- phologicsimilarity at sympatric localities.The authors also raise the question in the 'Postscript' section about the true taxonomicsub specificdivision of these two polymorphicspecies and point to the necessity for future studies to solve these taxonomicdifficulties. In fact there are areas of true sympatry between several taxa which may suggest that taxa here treated as subspeciesactually are good species. However, more documentationabout this phenomenonmust be presented before further conclusionscan be drawn. The authors point severaltimes to the possibilityof the occurrenceof additionalsibling species, and stress that caution must be taken in future taxonomicstudies in this difficultgroup. One such possiblecase of sibl- ings may be the two taxa Agkistrodoncaliginosus and A. intermediusussuriensis which have recently been put together in one species,A. ussuriensis,by Toriba (1986). Gloyd and Conant discussthis interpretationand stress the possibilitythat this may be another case of siblingspecies, but leave the question open for future studies. The book is an impressivesource of knowledgeand this is also the case with the referencelist which con- tains almost 1900 references on the subject and with an additional list of references on venoms and envenomationat the end of thebook, written by D. L. Hardy and publishedas one of nineancillary papers. The other eight ancillarypapers include one on behaviour by C. C. Carpenter and J. C. Gillingham,one on chromosomesby C. J. Cole, one on the fossilhistory on North Americantaxa by Roger Conant, one by Howard K. Gloyd with a discussionon palearcticAgkistrodon, one on skull, muscle and bone variation by K. V. Kardong, one on hemipenialstructure by E. V. Malnate, one on immunologicalrelationships by S. A. Minton, and a final paper on Pleistocenecopperheads by T. R. van Devender and Roger Conant. Althougheach of these ancillary papers is good and contributes in an important way to the main text, they constitutejust a minor part of this monograph. But in the last of these ancillarypapers an interesting and convincingdiscussion of thephylogeny the Americanspecies of Agkistrodoncan be read. This is preceded by a chapter in the main text about the phylogenyand zoogeographyof the old world taxa of the group. All phylogeneticdiscussions are by their nature more or lesshypothetical, as they more or lessmust be based on assumptionsdepending on how much fossilmaterial is availableor to what degree various more or less sophisticatedmethods have been applied. Almostno fossilmaterial is availableof the old world forms of Agkistrodonand related genera. Thus the phylogenyhas been based on availableinformation from recent taxa. The authors have analysedthe material in the traditional "old-fashionedway" and cladisticmethods have not been used. Much of this sectionwas written by Gloydlong before his death and Conant has chosen to include many of these thoughts unchanged in this section. Although no cladisticshave been used the authors base their discussionon polarized character states, and a phylogenybased on cladisticsand par- simony methods could have added phylogeneticinformation to this work. Now as it seems, this "old- fashioned" phylogenystill most certainlyresults in a proper phylogenetictheory also of the old world taxa, albeit two of the species,intermedius and blomhoffi,are paraphyleticas figured in the drawing of the phylo- genetictree on page 448. By using a phylogeneticspecies concept several of the various subspecies,defined by apomorphiccharacter states, could be treated as full species. Type specimensand type localitiesare unsolvedproblems for many taxa in the Agkistrodoncomplex. Partly this is becauseno type-seriesor holotypeshave been selected,or that the type seriesinclude specimens from differentsources and localities.This may sometimesbe a sourceof confusion.When Strauch describedhis intermedius(Trigonocefihalus intermedius) he used material which includesseveral taxa, includingA. i. saxatilis.