Tracing the Origins of Signal Diversity in Anole Lizards

Various factors have been shown to influence the evolution of communication structures in animals. For instance, signals used by species to attract mates will tend to be favored by selection (Jord and Martins, 2006, p. 2). The properties of the animal’s environment, especially the makeup of the habitat, are another factor that influences the evolution of the communication methods. Apart from adaptation, there are other factors such as mutation, random genetic drift and the genetic correlations between different elements of a given phenotype. It is rather difficult to positively identify the exact evolutionary process responsible for the differences in animal signals. This is because animals normally display more than one signal that could have arisen as a result of varying evolutionary forces (Jord and Martins, 2006, p. 3).

In order to have animals communicating effectively with each other, it may be important that they produce signals that are capable of conveying messages that are reliable and are understandable to their fellows (Jord and Martins, 2006, p. 7). The efficiency of the signal is normally determined by a number of factors such as the extent of the vegetation that are blown by the wind that determines the clarity of the motion displays in the lizards. Another is the availability of visual interferences between the sender and the receiver, the amount of light available in the habitat that determine the clarity of the motion display i.e. the clarity of the headbobbing lizard is never clear under dim light. Various ecomorphs are associated with peculiar selection forces and this could therefore be the cause of differences in display features.

Anolis is one of the largest genera in the world and it consists of about 400 species. This could be as a result of adaptive radiation in the islands of Antilles and the inhabitation of the mainland Central America and Northern South America. The genus has been extensively used in research work because it provides an important ecological, evolutionary biology and island biographic system. In addition, the group has a lot of information concerning its morphological, phylogenetic and ecological setup data (Jord, and Martins, 2006, p. 3). The study capitalized on the group‘s large species diversity and the focus was specifically on the diversified movement features in anole headbob and the dewlap displays.

Methodology of Research

Modern phylogenetic comparative methods were used to study the effect of the ecological and phylogenetic factors on the interspecific diversification of a multifaceted signal and the dynamic visual displays of animals (Jord and Martins, 2006 p. 3). The study also aimed at showing how data from various sources can be compared to help determine the evolutionary forces that cause the diversity in signals.

The information for the study was collected from the published display action pattern graphs that had information on the motion of headbobs and dewlaps over a period of time. The data collection was restricted to the signature displays only; the other information collected was on sexual size dimorphism, habitat use, and sympatry and ecomorph class. In the analysis of the study; for the start, the phylogenetic generalized least squares method was used to assess the ancestral states and relationships between the evolutionary changes and the surroundings. The phylogenetic mixed model was then used to assess the relationship between the interspecific phenotypes and evolution.

The research involved the use of four phylogenetic comparative methods, alternative phylogenetic hypotheses and asset of data that had been collected from 50 different sources representing 53 different strata (Jord and Martins, 2006, p. 1).

The investigation started by looking at the relation between the different signal characteristics that constitute displays. Then the role of the evolutionary processes in determining the display structure using the phylogenetic generalized least squares and the phylogenetic mixed models; to determine the display components that are controlled by phylogeny. Finally the effect of the ecological set up of the species on the evolution of signals was studied. Apart from the effect of sexual selection, the recognition of species and the role of the organism’s habitat in the evolution of the display structures in anoles were also examined.

Result of Research

The study showed that there was no special choice of females in the iguana lizards but it was shown that sexual selection was shown by the males when they fought over control over the regions that would allow easy access to the females (Jord and Martins, 2006 p. 4). Research also shows that the conflicts over territories by males are mainly influenced by the differences in the sexual sizes of the organism. The competition between males in the lizards have been found to cause the evolution of various methods of communication and as a result a number of signals are developed, some of which could be in the form of color variations (Jord and Martins, 2006, p. 5). Then the sexual size dimorphism effect on the evolution of the shorter and more complex signals was assessed. In the anoles the sexual selection has been shown to influence the development of the sexual size dimorphism and it normally occurs by pushing the organisms into ecological setups so as to minimize the conflicts between same sexes (Jord and Martins, 2006, p. 6). If the divisions of the ecological niche results into sexual size differences, then it means that the sexual size dimorphism could be having a very minimal effect on the development of the signals.

The sexual size dimorphism and the headbob duration were shown to have a strong negative correlation. The study also found that there was very little relationship with the other display traits with sexual size dimorphism. The species’ body size was found to be positively related to sexual size dimorphism in the anoles. It was also shown that there was a negative relationship between headbob homogeneity and the sympatric congeners and that the lizards communicating in a sunny environment used more pulses that stayed in the environment for quite some time (Jord and Martins, 2006 p. 10). The headbob duration and the dewlap latency were found to be related to the ecomorph categories. The study also showed that the display evolution is as a result of multiple forces. The habitat structures were found to affect the varying properties of lizard’s visual displays (Jord and Martins 2006 p. 14).

The intensity of the competition between the males normally gives rise to the development of even more complex and efficient display features to assist in the assessment of the other males for a speedy conflict decree. The diversity in the displays of the sympatric species is found to be higher than in the allopatric species and is normally proportional to the number of congeners each of the species encounter (Jord and Martins, 2006, p. 8). Species in the less sunny surroundings always produce longer and more homogenous signals so as to enhance the identification of that given signal. The arboreal ecomorphs are shown to have developed slow few display movements.


The research was meant to test the relative importance of different ecological variables on the evolution of anal visual displays. The results of the study showed that the change in the different display components could have been as a result of selection, but evolution normally shows that the changes that occur during the time of display could be as a result of sexual dimorphism and the number and uniformity of the display. The research also showed that ecomorph differences also have an effect on the display structure’s evolution.

The communication between organisms is always a very important activity since it enables the organisms to acquire food, avoid danger and mate among other things. This will enhance the survival of the species. The modes of communication are normally diversified and at times the animals, especially the males exhibit aggression when communicating with other males. The animals can use signals such as color variation and production of sounds in order to communicate. These signals normally show a lot of diversification even among members of the same species. This has been shown to be as result of the nature of the habitat, the amount of illumination in the environment and sexual selection.


Jord, T. and Martins, E. P. (2006). Tracing the origins of signal diversity in anole Lizards: phylogenetic approaches to inferring the evolution of complex Behavior. ANIMAL BEHAVIOUR, 71, 1411–1429. Web.

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