1. Example of Herpetological Research in Colorado
BL/ENVS 476: Colorado Flora and Fauna
September 19, 2011

2. A Fundamental Problem
Sexual reproduction is predominant in vertebrates
The common perception is that long-term evolutionary success is based on phenotypic variability generated by genetic recombination.
But there are many parthenogenetic lizards that exhibit ecological success; e.g., Aspidoscelis tesselata.
Alternatives to sexual reproduction in vertebrates:
Hybridogenesis and gynogenesis: in a few fish species Parthenogenesis: in a few lizard species
The purpose of this research was to test the idea that genetic recombination is critical for phenotypic variation, using parthenogenetic and sexual species of the lizard genus Aspidoscelis.

4. A. Aspidoscelis marmorata
B. And C. A. gularis septemvittata
D. A. tesselata E (2n)
F. A. tesselata C
E. A. tesselata D
G. A. sexlineata
H. A. neotesselata (3n)

5. How do you reproduce without males?
1. Premeiotic doubling of chromosome number
DNA synthesis
A. tesselata: 46 single-stranded chromosomes (46 DNA molecules)
Endoreplication  46 double stranded chromosomes
Centromeres separate: 92 single-stranded chromosomes
2. Provide each chromosome with a genetically identical synaptic partner.
92 single-stranded chromosomes  92 double-stranded chromosomes.
3. Undergo the two meiotic divisions as found in sexual species.
Synapsis and crossing over with “sister” (identical) chromosomes
1st division: 92 double-stranded chromosomes /cell  46 double-stranded chromosomes/cell
2nd division: 46 double stranded chromosomes/cell  46 single stranded chromosomes/cell
One becomes an ovum. genetically identical with mother

8. Patterns of Morphological Variability
1. Among “uniclonal” and “multiclonal” groups of two color pattern classes of A. tesselata
Multiclonal = more than one allele for a particular gene locus
Glucose-6-phosphate isomerase (GPI)
Multiclonal: GPI ab and GPI ac
Uniclonal: GPI ac
2. Between each of four geographically disjunct groups of A. tesselata and a sympatric sexual species
Controlling for environmental effects on phenotypic variation
3. Among the four species
Can the variability of the parthenogenetic species exceed the variability of a sexually reproducing species?
The phenotypic characters used are quantitative: GAB, FP, COS, LSG, SDL
Meristic characters: counts

9. The pattern of variability has to be simplified
Done with multivariate statistics
Principal components analysis
Uses variance/covariance relationships among characters
Establishes coefficients to multiple times the values of the original characters
New variables are produced called principal components
Linear compounds of the original meristic character scores and coefficients
Concentrate as much of the variation of the original variables in a reduced number
of new variables: principal components.
Each specimen has score for principal component 1 and principal component 2.
Scores are plotted to show patterns of variation.
Variances of the principal component scores can be compared for relative
variability.

10. Do “multiclonal” groups A
Do “multiclonal” groups A. tesselata express greater variability than “uniclonal” groups?
Multiclonal: more than
one GPI allele
Uniclonal: one GPI allele

11. Example of verification

13. Are differences in phenotypic
variability related to reproductive mode?

15. Are differences in phenotypic
variability related to reproductive mode?

16. How does A. tesselata rank on a scale of relative variability
with sexual A. sexlineata, A. marmorata, and A. gularis septemvittata?

17. Conclusions
Aspidoscelis tesselata is organized as a collection of independent mother-daughter arrays.
Cohesiveness achieved by ecological constraints.
This would mean that the relative phenotypic variability of a particular parthenogenetic groups should not be predictable by reproductive mode, color pattern class, or geographic location.
This was confirmed by the present study.
Presumably, phenotypic variation increases as development is variously modified in clones produced by random mutation.