Anolis lizards follow a common ontogenetic growth trajectory despite early embryonic species differences in relative limb length
(2021) BION03 20201Degree Projects in Biology
- Abstract
- The generation of phenotypes in nature is not boundless. They are governed by natural selection as well as genetic and developmental processes that precede selection. When the developmental process itself is biased, it promotes or prevents certain phenotypes from being formed which in turn could impact the course of evolution. Despite the solid theory behind developmental bias, its exact influence on evolution has remained ambiguous. This study aims to fill in this knowledge gap by investigating the covariation of 13 limb bones during embryonic development of 15 Anolis species. Embryos were processed through a clearing and staining procedure in order to measure the limb bones. The results of a bivariate allometry analysis indicates that... (More)
- The generation of phenotypes in nature is not boundless. They are governed by natural selection as well as genetic and developmental processes that precede selection. When the developmental process itself is biased, it promotes or prevents certain phenotypes from being formed which in turn could impact the course of evolution. Despite the solid theory behind developmental bias, its exact influence on evolution has remained ambiguous. This study aims to fill in this knowledge gap by investigating the covariation of 13 limb bones during embryonic development of 15 Anolis species. Embryos were processed through a clearing and staining procedure in order to measure the limb bones. The results of a bivariate allometry analysis indicates that species-specific differences in relative limb length are established in early ontogeny, prior to the emergence of cartilaginous condensations. The results of the multivariate allometry analyses indicate that Anolis species follow a common ontogenetic growth trajectory and that ecomorph species are therefore not “unique” in any regard. In conclusion, differential limb morphologies in Anolis species are already apparent in early ontogeny. Despite the early differentiation, this set of species (which includes a large variety of ecomorph and non-ecomorph species) follows a single similar allometric trajectory, yet is still capable of evolutionary diversification. (Less)
- Popular Abstract
- Anolis lizards share a common ontogenetic growth trajectory despite early embryonic species differences in relative limb length
Evolution has provided us with an incredible variety of different organisms. However, we know that the generation of phenotypes (the combination of observable traits) is not unlimited. In order for a certain phenotype to be formed, it must first go through a highly regulated developmental process involving cell division, tissue differentiation, growth, etc. The developmental process itself can be biased causing certain trait combinations to be common, whereas others might be rare or not produced at all. When these phenotypes are later subject to evolution, developmental bias will ultimately impact evolutionary... (More) - Anolis lizards share a common ontogenetic growth trajectory despite early embryonic species differences in relative limb length
Evolution has provided us with an incredible variety of different organisms. However, we know that the generation of phenotypes (the combination of observable traits) is not unlimited. In order for a certain phenotype to be formed, it must first go through a highly regulated developmental process involving cell division, tissue differentiation, growth, etc. The developmental process itself can be biased causing certain trait combinations to be common, whereas others might be rare or not produced at all. When these phenotypes are later subject to evolution, developmental bias will ultimately impact evolutionary outcomes. Mapping this developmental baseline is therefore essential in understanding evolutionary patterns such as adaptive diversification and convergence.
This thesis has examined the role of developmental bias in Anolis lizards who are a textbook example of adaptive radiation and show a remarkable pattern of convergent evolution. Anolis lizards are adapted to their microclimates specifically through the size and shape of their limbs (e.g., species with short limbs are specialized for perching on twigs and branches, while species with long limbs are agile runners on tree trunks). We observe convergence not merely in individual species but of entire species assemblages. Similar habitat specialist groups have evolved independently, essentially showing “evolution on repeat”.
I tested if developmental bias impacts phenotypic diversification by studying the covariation of limb bones during embryonic development of 15 Anolis species. I measured limb bones during successive embryonic stages up until hatching and compared the developmental trajectories between species. In order to do this, I used a clearing and staining procedure which rendered the soft tissue transparent while pigments stained cartilage and bone.
My results have shown that species-specific differences in relative limb length are already established in early development and become more pronounced near the hatching stage. They also show that all the studied Anolis species follow a common developmental growth trajectory in which the relative proportions of individual limb elements scale up in a similar way throughout development. This came as a big surprise since I observed such large differences in relative limb length between species. It seems that despite this early differentiation of relative limb length, species follow a similar “developmental blueprint” and are still capable of evolutionary diversification.
Master’s Degree Project in Biology, 60 credits, 2021
Department of Biology, Lund University
Advisor: Nathalie Feiner
Evolutionary Biology, Lund University (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9043306
- author
- Van der Cruyssen, Eliane
- supervisor
- organization
- course
- BION03 20201
- year
- 2021
- type
- H2 - Master's Degree (Two Years)
- subject
- language
- English
- id
- 9043306
- date added to LUP
- 2021-04-26 12:03:47
- date last changed
- 2021-04-26 12:03:47
@misc{9043306,
abstract = {{The generation of phenotypes in nature is not boundless. They are governed by natural selection as well as genetic and developmental processes that precede selection. When the developmental process itself is biased, it promotes or prevents certain phenotypes from being formed which in turn could impact the course of evolution. Despite the solid theory behind developmental bias, its exact influence on evolution has remained ambiguous. This study aims to fill in this knowledge gap by investigating the covariation of 13 limb bones during embryonic development of 15 Anolis species. Embryos were processed through a clearing and staining procedure in order to measure the limb bones. The results of a bivariate allometry analysis indicates that species-specific differences in relative limb length are established in early ontogeny, prior to the emergence of cartilaginous condensations. The results of the multivariate allometry analyses indicate that Anolis species follow a common ontogenetic growth trajectory and that ecomorph species are therefore not “unique” in any regard. In conclusion, differential limb morphologies in Anolis species are already apparent in early ontogeny. Despite the early differentiation, this set of species (which includes a large variety of ecomorph and non-ecomorph species) follows a single similar allometric trajectory, yet is still capable of evolutionary diversification.}},
author = {{Van der Cruyssen, Eliane}},
language = {{eng}},
note = {{Student Paper}},
title = {{Anolis lizards follow a common ontogenetic growth trajectory despite early embryonic species differences in relative limb length}},
year = {{2021}},
}