COMPARATIVE POPULATION CYTOGENETICS, SPECIATION, AND EVOLUTION OF THE CREVICE USING SPECIES OF SCELOPORUS (SAURIA, IGUANIDAE)

by

William P. Hall, III

Museum of Comparative Zoology, Harvard University, Cambridge, Mass. 02138

CONTENTS

Introduction

Scope

Sceloporus as a resource for the study of evolution

Karyotype variation in Sceloporus

Chromosomal Speciation Theory

Basics

genetic revolutions

chromosomal differentiation

hybridization

The geographic component

Cascading revolutionary speciation

cascade initiation

chain termination

evidence

Karyotypes as a phyletic tool

Methods and Materials

Cytological procedure

Material examined

Results

The "standard" or S karyotype

The "enlarged micro" or Em karyotype

Karyotypic diversity of Sceloporus grammicus

Introductory comments

S or standard grammicus

P1 or polymorphic-1 grammicus

F6 or fission-6 grammicus

F5 or fission-5 grammicus

F5+6 or fissions 5+6 grammicus

FM or multiple fissions grammicus

Contact zones, hybridization, and reproductive isolation in grammicus

general

triploidy and possible incipient parthenogenesis

Karyotype Evolution

Karyotype evolution in the grammicus complex

caveat

possible phyletic sequences

the probable phyletic sequence

Clarkii group chromosomes and origin of Em karyotypes

Sex chromosome evolution

Evolution of the Species Groups

Karyotypic phylogeny

Alternative phylogenies

the Smith phylogeny

problems with the Smith phylogeny

the Larsen phylogeny

problems with the Larsen phylogeny

Reconciliation and phyletic synthesis

the biology of crevice using

reproductive biology

biogeography

synthesis

Patterns of Speciation

Introductory comments

Conservative geographic speciation

Revolutionary speciation

Cascading revolutionary speciation

Geography of revolutionary speciation

Summary and Conclusion

Acknowledgements

Notes

Bibliography

Appendix: Specimens Examined

FIGURES

1. Distribution of karyotypic variation in the family Iguanidae

2. The standard karyotype

3. Standard karyotypes of the torquatus species group

4. The standard and Em karyotypes of three species groups

5. Major karyotypes of the grammicus complex

6. Comparison of standard grammicus and Agama caucasica

7a. Distribution of grammicus karyotypes in Mexico

7b. Distribution of grammicus karyotypes in the Valley of Mexico

8. Karyotypic relationships of the clarkii species group

9. Male diakinesis arrays,

10. Microchromosomal arrays from male diakinesis.

11. Reconstruction of the karyotypic evolution of the crevice-using Sceloporus and the clarkii group

12. Relationships of the species groups of Sceloporus as proposed by Smith (1939)

13. Relationships and groupings of Sceloporus proposed by Larsen

14. Geographic distributions of the 2n=34 orcutti group species

15. Geographic distributions of the 2n=40 clarkii group species

16. Geographic distributions of the Em karyotype species

17. Geographic distributions of the standard species of the grammicus group

18. Geographic distributions of the torquatus group species

19. Early radiation of the large-sized, large-scaled Sceloporus

TABLES

1. Summary of Karyotyped Lizard Genera and Species, by Family

2. Geographical and Ecological Distribution of Standard grammicus

3. Geographical and Ecological Distribution of F6 grammicus

4. Geographical and Ecological Distribution of P1 grammicus

5. Geographical and Ecological Distribution of F5 grammicus

6. Geographical and Ecological Distribution of F5+6 grammicus

7. Geographical and Ecological Distribution of FMl grammicus

 8. Geographical and Ecological Distribution of FM2 grammicus