Jerry John, D.Y Patil University
According to the fossil records, the life of our earth is about 3.5 billion years and these planets hold wonders in it. If we see deep into these beauties, we can find different organisms from different habitats. In 1862 Bates, observed several simple and conspicuous color patterns distantly related to Lepidoptera species in the same habitat. After many arguments and studies, they introduced a successful theory of natural selection for the phenomenon of mimicry.
About Mullerian Mimicry :
Mimicry is an adaptation process where organisms share several common phenotypes. One of such mimicry systems is Mullerian mimicry. Found by the German biologist Frtiz Muller is a phenomenon between two or more harmful species that evolve to enact one another. This species serves on an individual of either ‘co-mimic’ species. The organism with this kind of mimic will be rare as they feed on their ‘ co-mimic’ species. Aposematic species have a Mullerian mimicry phenomenon. It has a vivid color pattern which indicates it is a toxic organism. The color phenotypes are selected by sexual selection, or natural selection, or both. An Aposematic species shows adaptive radiation, an example of phenotypes by strong selection. This mechanism of color and pattern phenotype will help us to understand evolution.
Identification of Mullerian Mimicry in Aposematics species:
Geographically, that there is rapid diversification of color and pattern in a group of species. It creates a variety of polytypic phenotypes, which keeps each predator unique. Heliconius butterflies, velvet ants, millipedes, and poison frogs are some species enlisted in papers. The majority of mimicry is found in the Heliconius butterfly. It holds a genetic locus that controls the phenotypic variation seen in entire species and also explains the mimicry convergence between the species. To examine the natural selection on color pattern phenotypes and to identify the mechanism of convergence by which it occurs at the molecular level, understanding the genomics of adaptive phenotypic diversification is in need. So, this plays substantial importance in the field of evolution.
The study of Stuckert et.al about Mullerian mimicry in Amphibians:
Here to understand more about the Mullerian mimicry in other species. Stuckert et.al has studied the convergent color phenotypes in Ranitomeya from the Northern Peru region. Ranitomeya is an excellent example of Mullerian mimicry. It contains mimic poisonous frog ( Ranitomeya imitator, Dendrobatidae ). This species has gone through several adaptive radiations so that co-mimic species have been created ( R.fantastica, R.summersi, and R.variabilis).
Results :
According to the literature, the similarities between R.imitator and R. Fantastica, R.variabilis are done. The assembled R.imitator genome is a high-quality genome sequence with high genic content. Its length is about 6.8Gbp, 50% of genome assembly is a repeated sequence. The studied colors and patterns of Ranitomeya species are variable. They have a vivid color patched in a black colored background. Specific colors are included in xanthophores like pteridines, carotenoids, which interact with structural elements to give yellow to red-orange colorations. Most frogs have a black-colored body; some have a brown-colored one which depends on the melanophores and melanin pigmentations. The colors and patterns are produced by the pteridine pathway.
Pteridine synthesis pathway for colors and patterns in animals :
The pteridine pathway is a source of coloration. According to the genetics studies and biochemical assays of pigments, pteridine is responsible for animal coloration. It was said as the pteridine pathways produce different color patterns. But as the studies, the pteridine synthesis gene expresses differently in-between color morphs. The dominant among xanthine dehydrogenase(xdh), quinoid dihydropteridine reductase (qdpr), and 6-pyruvoyltetrahydropterin synthase (pts) decide the color and patterns. Xanthine dehydrogenase(xdh) is highly conserved and plays an important role in the production of protein-based coloration in various organisms like spiders, fish, and the dendrobatid frogs.
Discussion :
In this study, the divergence between the color morphs may be due to the difference in expression or the time of expression. The convergence for the same color patterns cannot be produced through the same changes in gene expression. So, we found that pteridine synthesis pathways play a role in the production of different color morphs in species. So, the specific color production was observed due to the strong differences in gene expression among the species in the pathway, or maybe the species-specific color patterns in this pathway help to produce similar colors and patterns among the same species.
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References:
- Stuckert, A. M. M., Chouteau, M., McClure, M., LaPolice, T. M., Linderoth, T., Nielsen, R., Summers, K., & MacManes, M. D. (2021). The genomics of mimicry: Gene expression throughout development provides insights into convergent and divergent phenotypes in a Müllerian mimicry system. Molecular Ecology, mec.16024. https://doi.org/10.1111/mec.16024
- Mallet J. “New genomes clarify mimicry evolution”. Nat Genet. 2015 Apr;47(4):306-7. doi: 10.1038/ng.3260. PMID: 25814305.
- Deborah Charlesworth, Brian Charlesworth, “Mimicry: The Hunting of the Supergene”, Current Biology, Volume 21, Issue 20,2011, Pages R846-R848, ISSN 0960-9822, https://doi.org/10.1016/j.cub.2011.09.004
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