Genital Morphology

Adams, D. C. (2012). Comparing evolutionary rates for different phenotypic traits on a     phylogeny using likelihood.Systematic Biology, sys083.

According to the article, likelihood-based approaches have been used at an increasing rate to evaluate macro-evolutionary hypotheses of phenotypic development under different evolutionary processes in a phylogenetic setting and to compare one or more evolutionary rate for the same phenotypic trait along a phylogeny.  The article to determine whether one trait evolves at a faster rate compared to another trait. There isfew research that compare phylogenetic evolutionary rates between traits using likelihood because formal approach have not been proposed.  The author seeks to describe new likelihood procedure for comparing evolutionary rate for two or more phenotypic traits on a phylogeny. The method contrast the likelihood of a model where each characteristic evolves at a different evolutionary frequency to the likelihood of a model where all characters are controlled to advance at a mutual evolutionary frequency.  The approach is to account for within-species measurement error and within-species trait co-variation when available. Simulations revealed that the method has appropriate type I error rates and statistical power. According to the author, when comparing the existing approaches based on phylogenetically independent contracts and methods that compare confidence intervals for a model parameter, the likelihood method displays preferable statistical properties for a wide range of simulated conditions.   The article asserts that the likelihood-based method extends the phylogenetic comparative biology kits and offers biologists with a more powerful approach to determine when evolutionary rate differ in phenotypic traits.  The approach proposed can be additionally extended to evaluate other distinct evolutionary model, by adjusting the phylogenetic covariance matrix.  Incorporating the approach described with existing approaches provide the researcher with greater flexibility in evaluating evolutionary hypotheses of character change and accumulation of phenotypic diversity within and across lineages.


Harrison, A., & Poe, S. (2012). Evolution of an ornament, the dewlap, in females of the lizard      genus Anolis.Biological Journal of the Linnean Society, 106(1), 191-201.

According to the article, male ornaments have been subject to numerous studies on sexual selection and communication. However, female ornaments have garnered substantially less study, despite being well developed in some species.  The factors that have propelled the evolution of elaborate ornaments in female are not well understood because it includes genetic correlations between social selection, sexes, species recognition and sensory drive.  The article used simulation-based comparative methods and a newly estimated phylogeny to analyze four hypotheses to explain female ornamentation within the diverse neo-tropical lizard genus Anolis. The authors found that the support for the sensual drive hypothesis and the community selection hypothesis, the female dewlap was greater in species that use additional arboreal habitats, as well as in species where the sexes were less dimorphic. There was not support for the genetic correlation hypothesis or the species recognition hypothesis.  Authors propose that the size of female dewlap ma evolve in response to sensory drive differentially affecting species in different habitats and selection such as male mate choice or intra-sexual competition for territory among females.  The article provides information about evolution of the female dewlap could be improved by using continuous data on dewlap size, direct information on ecological variables  including  female competition  for  mates and territories, and phylogeny with realistic branch length estimates.

Johnson, M. A., Lopez, M. V., Whittle, T. K., Kircher, B. K., Dill, A. K., Varghese, D., &Wade, J. (2014). The evolution of copulation frequency and the mechanisms of reproduction in   male Anolis lizards.Current Zoology, 60(6), 768.

According to this article, the evolution of much morphological structures associated with the behavioral context of their use, anespecially structure involved in copulation.  There are few studies that have considered evolutionary relationship among the integrated suite of structure associated with male reproduction.  In the experiment, investigators examined nine species of lizards in the Genus Anolis in the effort of determining whether larger copulatory morphologies and higher potential for copulatory muscle performance evolve in connection with higher copulation rates. In 10-12 adult males from each species, we measured the size of the hemipenes and related muscles, examine the fiber type composition of muscles associated with copulation and the renal sex segments in the kidney. During the study, the investigator used field behavioral data to determine whether observed rates of copulationwere associated with such morphologies.  Results reveal that species with larger hemipenes had larger fibers in the retractor penis Magnus and that the evolution of larger hemipenes and retractor penis Magnusis linked to the evolution of higher rates of copiatory behavior. The size of the seminiferous tubules and renal sex segments and the muscles fiber composition of the retractor penis magnusare not associated with copulation rates.  The article assert that body size is not associated with the size of the reproductive structure investigated. The results of the study suggest that peripheral morphologies involved in the transfer of ejaculate may be more evolutionarily labile than internal structure involved in ejaculate production.



Klaczko, J., Ingram, T., &Losos, J. (2015). Genitals evolve faster than other traits in Anolis           lizards.Journal of Zoology, 295(1), 44-48.

This article assert that male genitalia are rapidly evolving morphological structure, despite few quantitative interspecific comparison between the evolutionary rate of genital and non-genital trait.  The most prominent argument is that genitalia evolve as a result of sexual selection. Sexual selection drives male genital evolution either through cryptic female choice or sexually antagonistic coevolution, which are predictors of therapid evolution of male genitalia as a result of coevolution with the female. Authors argue  that cryptic female choice favor male genitalia  that better fit or stimulate  the female, while sexually antagonistic coevolution occur if male genitalia evolves to reduce female control of reproduction resulting  in a co-evolutionary arms race between sexes. During quantify hemipenis morphology of 25 ecologically diverse species of Caribbean, Anolis.  The study uses phylogenetic comparative methods to estimate the evolutionary rate of hemipenis trait and to assess whether they surpass the evolutionary rate of morphological characterslinked to microhabitat and gesticulating.  The experiment seeks to examine the male genitalia demonstrating the variety of microhabitat specialists present in Caribbean anoles.  During the experiment, the investigator took three hemipenis measurement including total length, width at the hemipenis body and width at the lobes.  The width at the hemipenis lobes was obtained by measuring the widest region of the lobes and width at thehemipenis body was obtained by measuring the width approximately halfway along the body of the hemipenis. To determine whether the hemipenial trait evolves faster than the non-genital trait, likelihood method for comparing evolutionary rates of thedifferent phenotypic trait. The method estimates the rate of evolution as the Brownian rate parameter and compares the fit of themodel on which traits differ in rate versus constrained to share rates. Evolutionary rate analysis reveals that strong support for rate variation among trait with genital charactersvalued to have a frequency six times more than non-genital traits.  According to authors, the higher rates of hemipenial trait evolution could be explained by sexual selection.

Köhler, J., Hahn, M., & Köhler, G. (2012). Divergent evolution of hemipenial morphology in        two cryptic species of mainland anoles related to Anolis polylepis. Salamandra, 48(1), 1-          11.

According to this article assert that male genital morphology is a crucial diagnostic character to discriminate closely related species in many different groups of organisms. . It seeks to examine thedivergent evolution of hemipenial morphology between closely related forms appears to be a common phenomenon in mainland anoles. In addition, the article discusses the possible evolutionary scenarios for this finding based on different lines of evidence from work on Anolispolylepis and A. osa from Costa Rica. Results from the experiment revealthat the recent split of Anolisosa clade from asoutheastern population of polylepis and he generally indicate a limited and non-existing gene-flow along thematernal line between thegeographic different populations. Available evidence suggests that sexual selection by female choice is the effective plausible for thepeculiar rapid divergent evolution of genital morphology. There is an assumption that afemalecan discriminate males with different hemipenis morphologies  and that insemination success varies depending on female preference and any male performing a superior stimulus wouldbenefit from theadvantage in reproductive success.  The article assert that females prefer mates performing the stimulus in turn would be favored by producing favorable male offspring.  Depending on how strong the sexual selection works, it could even maintain the geographical integrity of genital morphology against homogenizing effects from a male-biased gene flow.


Soto, I. M., Carreira, V. P., Soto, E. M., Márquez, F., Lipko, P., &Hasson, E. (2013). Rapid          divergent evolution of male genitalia among populations of Drosophila buzz tip.         Evolutionary Biology, 40(3), 395-407.

According to this article, there is an increasing evidence from a multiple animal system that genital evolution and diversification are affected by strong and rapid evolutionary forces.  Precisely, the morphology of male genital structure is considered to be the fastest evolving traits in animal groups with internal fertilization. In the experiment, the authors seek to investigate patterns of male genital variation within and between natural of male genital variation within and between natural populations of the cactophilic fly referred to as Drosophila buzzatii which is the original geographic distribution range in the neo-tropics. During the experiment, the investigator detected significant morphological variation among populations and distinguished five differentiated groups. Among population differentiation in genital morphology was linked with the degree of geographic loneliness among populaces and clearly compared with the general homogeneousness detected for the putatively neutral mitochondrial gene. The article provides compatible information with proposed evolutionary process coupled drift. Female may discriminate potential mates during copulation by their genital morphology. With female preference as the leading trait evolving by drift, the evolution of the follower trait. Coupled evolution is characterized by patterns similar to random drift at the among inhabitants level but in a petite evolutionary time span due to the acceleration imposed during sexual selection.  Patterns of population structure for the chromosomal polymorphisms and a quantitative trait which are concordant with the operation of strong selective forces as proposed by the association with ecological and relevant environment variables.