Archive for February, 2009

Atlantic Rain Forest domain

Deforestation

 

100 years ago and nowadays.

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Brazilian hotspots and refugia

Brazilianforests are widely known for their high biodiversity. Two hotspots were identified in Brazil by Myers et al.(2000): the Biome of Cerrado and the Biome of Atlantic Forest. Hotspots are regions or areas with high endemism and exceptional loss of habitat, that make them priority in conservation politics.

                The Atlantic Forest has been deforested along the last 500 years. Nowadays, less than 8% of the original cover is rested. Despite its diminished state, the Atlantic Foreststill ranks as a global conservation priority. Although it is just a small fraction of the size of the huge Amazon rainforest, the Atlantic Forest still harbors of a range of biological diversity similar to that of the Amazon. Not only similar in richness, but following Costa (2003), both forests were connected during the Pleistocene, and the Atlantic and Amazon’s fauna are relative.

We have seen that the Late Quaternary climate fluctuations helped to shape present-day diversity, providing a general context for understanding current patterns of endemism. Carnaval et al. (2009) related refuge areas and biodiversity in Brazilian Atlantic forest hotspot. In the study, the authors used frogs as indicators; ecological niche models under paleoclimates; and simultaneous Bayesian analyses of multispecies molecular data to compare alternative hypotheses of assemblage-scale response to late Quaternary climate change.

In a regional scale, biodiversity species should consistently show higher genetic diversity within and among populations in refugia relative to recent colonized areas. This is explained by the long-term persistence and population structure. The genetic signature of population expansion in unstable (recent colonized) areas, should reflect multispecies colonization from adjacent refugial regions after the Last Glacial Maximum (Carnaval et al. 2009).

Besides, the absence of genetic patterns of isolation-by-distance in recent colonized areas is due to colonization has been too recent to permit restoration of equilibrium between migration and genetic drift.

Following all predicts, the authors supposed a large central refugium throughout the Late Quarternary – Bahia refugium; a second much smaller in the northeastern most of forest – Pernambuco refugium; and a southeastern refugium of intermediate size – São Paulorefugium. The authors also supposed that these areas received a significant influx of migrants from adjacent, large refugial populations after Late Quaternary Maximum. The southern Atlantic forest was climatically unstable relative to the central part (Bahia).

I am from Espírito Santo, a state between São Paulo and Bahia and, following the article, it is included in Bahiarefugium. During my on field works, I could realize the difference among the forests. The Bahia Atlantic Forest (northern of my state) is drier and the fauna, generally, is less related to animals from the southernmost (more humid and high altitude). Otherwise, São Paulo has humid and high altitude forests, as the southern of my state.

Finally, this paper was quite interesting for my, because actually, the highest diversity that we have been found for a wasp family (Bethylidae) in Brazil occurs in the central part of the Atlantic Forest, which the authors called Bahia refugium. 

 

 

 

Carnaval AC et al. 2009. Stability Predicts Genetic Diversity in the Brazilian Atlantic ForestHotspot.

Costa LP. 2003. The historical brigde between the Amazon Forest of Brazil: a study of molecular phylogeography with small mammals. Journal of Biogeography 30: 71-86.

Myers N, Mittermeier RA, Mittermeier CG, da Fonseca GAB, Kent J. 2000. Biodiversity hotspots for conservation priorities. Nature 403: 853-858.

Science 323: 785-789.

Chaos Theory

It’s not really biogeography, but the Ethan’s class and Ken’s blog, remembered me my brother trying to explain me the Chaos Theory. 

“Chaos theory describes the behaviour of certain dynamical systems – that is, systems whose states evolve with time – that may exhibit dynamics that are highly sensitive to initial conditions (popularly referred to as the butterfly effect). As a result of this sensitivity, which manifests itself as an exponential growth of perturbations in the initial conditions, the behavior of chaotic systems appears to be random. This happens even though these systems are deterministic, meaning that their future dynamics are fully defined by their initial conditions, with no random elements involved. This behavior is known as deterministic chaos, or simply chaos.”

 

Considering the fractal definition  (a rough or fragmented geometric shape that can be split into parts, each of which is a reduced-size copy of the whole), you can ask: where is the relation? Chaos system is about dynamic systems and deterministic factors, such as the film that many of you have watched, The Butterfly effect. Otherwise, fractal is about static geometric traces.  Biological and physical models, e.g. weather, are explained or based on Chaos Theory, and fractal models can be kind of measurements in works on Chaos Theory. Well, the whole theory is complicated but, if I wasn’t persuasive in the relationship between them, I’ll let the pictures tell for me.

Fractal fern created using chaos game. Natural forms (ferns, clouds, mountains, etc.) may be recreated through an Iterated function system.

Fractal fern created using chaos game. Natural forms (ferns, clouds, mountains, etc.) may be recreated through an Iterated function system.

New Page

I’ve just added a new page related to my research proposal for Biogeography. Any ideas are welcome!

Last week on Nature…

I came out with this highlight today and I though it was interesting to post it here:

Two conflicting theories explain the heritage of New Zealand’s current flora and fauna.

Sea levels rose 25 million–22 million years ago, and some believe that the landmass was completely submerged during this time and then repopulated later by transoceanic voyagers. Others hold that the land was only ever partly submerged, and that the ancestors of some of today’s resident species have been there since New Zealand separated from other continents, 82 million–60 million years ago.

Marc Jones of University College London and his colleagues identified fossil jaw bones and teeth (pictured) of a rhynchocephalian reptile, a relative of the extant New Zealand tuatara. Given the fossil’s age — 19 million–16 million years — these lizard-like creatures would have had less time to repopulate the landmass than had previously been thought, suggesting that New Zealand was never fully underwater and has been home to the tuatara’s ancestors since the time of the dinosaurs.

 

The paper can be found in:

Proc. R. Soc. B. doi:10.1098/rspb.2008.1785 (2009)

 

😉