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Morph distribution and morph diversity in a colour polymorphic Lacertid lizard (P.muralis; Laurenti, 1768)

Plavos, Konstantinos (2017) BIOP01 20162
Degree Projects in Biology
Abstract
In colour polymorphic species the different morphs have discrete coloration and are typically correlated with particular phenotypic traits. In P.muralis the two evolutionary forces that maintain polymorphism has been suggested to be natural and sexual selection. Establishing the phylogenetic and geographic distribution of polymorphism is an important step to reveal if and how these selective procedures are applying to this species. Through the phylogeography and the genetic structure of the species, I here test if colour polymorphism is ancestral to this species, if it has been lost and where and how this loss occurred. I also tested if colour morph diversity in this species is affected by environmental factors. The results show that while... (More)
In colour polymorphic species the different morphs have discrete coloration and are typically correlated with particular phenotypic traits. In P.muralis the two evolutionary forces that maintain polymorphism has been suggested to be natural and sexual selection. Establishing the phylogenetic and geographic distribution of polymorphism is an important step to reveal if and how these selective procedures are applying to this species. Through the phylogeography and the genetic structure of the species, I here test if colour polymorphism is ancestral to this species, if it has been lost and where and how this loss occurred. I also tested if colour morph diversity in this species is affected by environmental factors. The results show that while polymorphism is ancestral to the species, it has been primary lost in the region of Tuscany and secondarily through selective introgression in the neighbouring lineages. The loss of polymorphism is associated with phenotypic divergence and in particular the evolution of highly exaggerated sexual characters in males. Climate did not seem to affect the distribution of the morphs on a large scale. Based on these results, I suggest that sexual selection is most likely to be responsible for the evolutionary maintenance of morphs, but it cannot be excluded that they are selectively neutral. (Less)
Popular Abstract
Lizards gone white? A case of morph loss and diversity in wall lizards

The different types in colour polymorphic species are usually correlated with other traits. In the common wall lizard, Podarcis muralis, the five colour morphs are thought to be maintained by two evolutionary forces: natural and sexual selection. I tested whether colour polymorphism is ancestral to the species, if it has been lost, and where and how this loss occurred. The results show that polymorphism is ancestral to this lizard, but it has been lost once in the region of Tuscany. Interestingly, it has later been lost through hybridization with lizards in the neighbouring areas. The loss of polymorphism is associated with the evolution of highly exaggerated sexual... (More)
Lizards gone white? A case of morph loss and diversity in wall lizards

The different types in colour polymorphic species are usually correlated with other traits. In the common wall lizard, Podarcis muralis, the five colour morphs are thought to be maintained by two evolutionary forces: natural and sexual selection. I tested whether colour polymorphism is ancestral to the species, if it has been lost, and where and how this loss occurred. The results show that polymorphism is ancestral to this lizard, but it has been lost once in the region of Tuscany. Interestingly, it has later been lost through hybridization with lizards in the neighbouring areas. The loss of polymorphism is associated with the evolution of highly exaggerated sexual characters in males. Based on these results, I suggest that sexual selection is most likely to be responsible for the evolutionary maintenance of polymorphism in this lizard.

Polymorphism is the phenomenon where individuals of a species may appear as distinct types, called morphs. In colour polymorphism, each morph has a particular colour and there usually are traits and behaviors connected to these morphs. In the polymorphic wall lizard Podarcis muralis there are three main colour morphs (white, yellow and red) as well as the intermediate morphs of white-red and yellow-red. Studies suggest that these morphs differ in particular traits, for example stress sensitivity, and the morph frequencies appear to be variable geographically, although white is in most cases the most common morph. The predominant hypothesis is that polymorphism is maintained in this species by a combination of natural and sexual selection. These selective processes are expected to shape morph composition and frequencies in populations.

In this study, I studied the distribution of colour polymorphism in P.muralis. I tested if morphs have been gained or lost by analysing the evolutionary history and geographic distribution of the species and I also tested for the existence of a relationship between morph diversity and trait and genetic divergence.
Results and implications
The results show that polymorphism is ancestral in this lizard and occurs across most of the contemporary distribution of the species. It is also prevalent in other species of the genus Podarcis and it may therefore reflect an even older evolutionary origin. However, there is evidence for a loss of the red and yellow morph, as monomorphic, white, populations are prevalent in central and northern Italy.

These populations are also distinct in terms of other characters, including coloration , morphology and behaviours that are likely to be under sexual selection via male-male competition. These characters evolved in the vicinity of Rome and have subsequently spread across a wider geographic area through directed hybridization (i.e., introgression). We can therefore hypothesize that the loss of polymorphism occurred in the Tuscan area and was associated with the evolution of exaggerated sexual characters. These characters later spread through selective introgression to nearby areas, resulting in a loss of colour polymorphism in a larger geographic region, now encompassing most of Tuscany.

Master’s Degree Project in Biology: Animal Ecology 60 credits 2017
Department of Biology, Lund University

Advisor: Tobias Uller
Department of Biology; Lund University (Less)
Please use this url to cite or link to this publication:
author
Plavos, Konstantinos
supervisor
organization
course
BIOP01 20162
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
8927839
date added to LUP
2017-10-26 10:42:57
date last changed
2017-10-26 10:42:57
@misc{8927839,
  abstract     = {In colour polymorphic species the different morphs have discrete coloration and are typically correlated with particular phenotypic traits. In P.muralis the two evolutionary forces that maintain polymorphism has been suggested to be natural and sexual selection. Establishing the phylogenetic and geographic distribution of polymorphism is an important step to reveal if and how these selective procedures are applying to this species. Through the phylogeography and the genetic structure of the species, I here test if colour polymorphism is ancestral to this species, if it has been lost and where and how this loss occurred. I also tested if colour morph diversity in this species is affected by environmental factors. The results show that while polymorphism is ancestral to the species, it has been primary lost in the region of Tuscany and secondarily through selective introgression in the neighbouring lineages. The loss of polymorphism is associated with phenotypic divergence and in particular the evolution of highly exaggerated sexual characters in males. Climate did not seem to affect the distribution of the morphs on a large scale. Based on these results, I suggest that sexual selection is most likely to be responsible for the evolutionary maintenance of morphs, but it cannot be excluded that they are selectively neutral.},
  author       = {Plavos, Konstantinos},
  language     = {eng},
  note         = {Student Paper},
  title        = {Morph distribution and morph diversity in a colour polymorphic Lacertid lizard (P.muralis; Laurenti, 1768)},
  year         = {2017},
}