A little over a year, we were fortunate to receive an unforgettable visit Peter and Rosemary Grant University of the Andes, where they gave an impressive conference based on his book How and Why Species Multiply occasion of our celebration early Darwin Day as part of events celebrating 60 years at the University . In the conference and in his book, Grant gathered his experience of more than 30 years studying the finches Darwin in the Galapagos Islands to illustrate the processes involved in the origin of species.
Despite having already gathered enough information to reach a comprehensive summary of how species are formed, the Grants do not stop. A few days ago released a new article , perhaps biased by the research that I'm more interested now, I think the most interesting thing I've read all year. The article tells the fascinating story of what happened to a person apparently belonging to the species Geospiza fortis who came to the island Daphne Major in 1981. The story, which Grant managed to figure out which detectives using multiple sources of information is as follows. This immigrant was in fact a hybrid between G. and G. fortis scandens probably came from the island of Santa Cruz. His bill was exceptionally large in comparison with those of G. fortis of Daphne Major, and his song, presumably acquired through apprenticeship after his arrival in Daphne Major, was a variation of a type of imperfect singing G. fortis that exists on this island but not in Santa Cruz or the rest of the archipelago. This guy is paired with a female resident (who also had genome hybrid), resulting offspring were mated with members of the local population. The descendants of this second generation established a lineage (defined by their edges, which are culturally inherited) that largely remained reproductively isolated from the rest of the population for several years, particularly after an event natural selection in the fourth generation which reduced this lineage to a pair of siblings (male and female) that mated with each other. From that point forward, members of this lineage (which have peaks, ridges and genes other than those of other birds on the island) have been paired only among themselves, essentially forming what one might consider a new species! 
This article is impressive because it meets relevant evidence for key questions in the study of the formation of new species. In terms of geographical context, suggesting that speciation occurred in two phases: initially there was divergence between populations with geographical isolation (allopatry) and then the divergence is completed in one place (sympatric) with the origin of differences in the song, which happens to be a fundamental mechanism of reproductive isolation for his role in the formation of pairs. In terms of evolutionary forces involved in speciation, the study suggests that natural selection acted process (the initial cause of divergence in phenotype between birds of Santa Cruz where it came from the immigrant and those of Daphne Major, and final stabilization of the line after the selective event of the fourth generation), a random component could be called cultural drift (responsible for the male immigrants were learned a local song and imperfect copy had developed a different signal) and further hybridization. All this is enough to change a classic study more of the several that have produced the Grant. The authors finish off the article talking about the possible fate that could follow the lineage that led to the male immigrant, which they carefully cataloged only as an incipient species. Is likely to end up disappearing in the short or medium term, but my interpretation of the data (based on the idea of \u200b\u200bErnst Mayr the biological species concept is dimensionless, that the standard bone isolation reproduction is only applicable in a moment in time and place in space) is that race may be considered a new species. The implications of this are profound, thanks to a multifaceted and extended in time, the Grants have been the origin of new species in real time. Darwin never imagined that something like this happen.
Grant, P., & Grant, B. (2009). Inaugural Article: The secondary contact phase of allopatric speciation in Darwin's finches Proceedings of the National Academy of Sciences, 106 (48), 20141-20148 DOI: 10.1073/pnas.0911761106
0 comments:
Post a Comment