Isolation and speciation

Roberta Batista Viana – u5492640

During the first semester of 2014 I worked at the Plant Anatomy Laboratory of the Botanic Department of University of Brasília preparing slides for later analysis of Peperomia glabella individuals from the continent and an oceanic island close to the Brazilian coast.

labanatoveg1

Question

The archipelago of Trindade and Martim Vaz is geographically isolated from Brazil, but the same species of Piperaceae occur in both habitats. So, Dr Micheline Carvalho Silva started questioning if this was a case of speciation.

The purpose of this research was to compare individuals from South America and Trindade and Martim Vaz archipelago using anatomic, phylogenetic and morphologic characteristics to determine if they were actually the same species.

peperomia-glabella

Peperomia glabella (extracted from: http://terrarienpflanzen-lexikon.de/wp-content/uploads/2011/07/peperomia-glabella.jpg)

What did I do?

My job was to prepare fresh slides by sectioning translucent slices (really, really thin) of the stem, leaves and petioles of three individuals of each habitat, photograph these slides and analyse the differences and similarities of continental and oceanic Peperomia.

Right now you might be thinking:

so boring

But wait! Here’s a nice photograph of the stem of one of these plants:

stem

The bigger picture

What is speciation? It occurs when a population of animals or plants is isolated geographically creating two distinct populations that can no longer exchange genetic material, so these two populations will start to evolve separately creating a new species.

How does it apply to this case? Trindade and Martim Vaz is an archipelago located ~1200km from the Brazilian coast with a high number of endemic species that haven’t been described since the discovery of the island.

Trindade-and-Martim-Vaz_image

Trindade and Martim Vaz (source: https://geos309.community.uaf.edu/files/2014/09/Trindade-and-Martim-Vaz_image.jpg)

Arquipelago-Trindade-Martim-Vaz

Trindade and Martim Vaz archipelago (source: https://www.mar.mil.br/secirm/img-trindade/antecedentes.jpg)

We don’t know how P. glabella individuals from the continent reached the beaches of this archipelago and how did they colonize the island.

This case might raise some questions about the process new species are created and what is the role of exotic plants in speciation.

Conclusion

Our findings were that all individuals had the same anatomic characteristics, except for different oil glandules for the island individuals (yellow and red glandules) and continental individuals (only red glandules). The phylogenetic analysis proved that they were the same species.

References

Carvalho-Silva, M. & Viana, R. B., 2014. Sociedade Botanica do Brasil – SBB. [Online]
Available at: http://www.botanica.org.br/trabalhos-cientificos/65CNBot/8402-BTE.pdf
[Acesso em 3 may 2015].

Da Silva, N., Alves, R., Da Silva Sylvestre, L. & Dos Santos, R., 2013. Two rediscoveries and one extinction for the flora of Trindade Island, Brazil. Journal of the Torrey Botanical Society, 140(2), pp. 230-235.

Ferris, K., 2014. Speciation on a local geographic scale: the evolution of a rare rock outcrop specialist in Mimulus. Philosophical transactions of the Royal Society of London. Series B, Biological sciences, 369(1648).

Santos, A., Rodrigues, S., Geraldes, M. & Vargas, T., 2015. Geology of Martin Vaz Island, South Atlantic, Brazil. Journal of Maps, 11(2), pp. 314-322.

 

 

 

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About Biodiversity Conservation Blog

I am an Associate Professor at The Australian National University and convene a (very awesome) course called Biodiversity Conservation. Myself and students in the course contribute to this blog.
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One Response to Isolation and speciation

  1. Chloe says:

    Some really interesting work experience! I’d be interested to know more about the questions that this case study raises about speciation, the role of exotic plants in speciation, and (given that the two populations were the same species), what does this mean about how P. glabella may have reached the island?

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