SpiritQuest

1. What hypothesis are Losos and colleagues testing?
In their examination of the evolutionary radiation of Anolis lizards on four separate islands of the Greater Antilles, Loasos and his colleagues are testing the theory that “repeated instances of evolutionary diversification will lead to disparate outcomes even if starting conditions are similar” . That is to say that the evolutionary paths of organisms all with similar starting conditions will diverge based solely on historical contingencies.

2. What is the alternative hypothesis inherent in the paper?
Though the intent of the researchers is to prove or disprove the relevance of historical contingency, there is a secondary theorem tested in the paper; the consideration of single or recurring evolutionary paths of the islands’ ecomorphs. It is hypothesized that either the species evolved, once, then entered the habitat or that they arrived at the islands prior to evolutionary transitions and that none of the ecomorph classes form a monophyletic group.

3. How do these hypotheses relate to the material we have covered in class?
[Place Answer Here]

4. What is an ecomorph and how is it defined in the paper?
The report defines ecomorphs to be a “species specialized to use particular structural microhabitats” . An ecomorph is therefore an organism that has evolutionarily conformed to its environment, with characteristics and traits that facilitate existence and survival in its niche.

5. How do the phylogenies in Figures 1A, 1B, and 1C support Losos and colleagues’ hypothesis?
The phylogenies all indicate a statistical irrelevance of geographical location relating to the divergence of ecomorphic evolutionary tracks. As shown in Figure 1A, there exist evolutionary clusters in the morphological structure of the ecomorphs across all four islands. The frequent transitions of the second figure relate to a recurring evolutionary system and solidify the argument that the evolution took place on the respective islands, and not preceding the lizards’ arrival and colonization.

6. What are the 3 different phylogenies measuring?
The three different phylogenies measure the sequences of events that lead through the evolutionary development of the species. Analysis was performed on the mitochondrial DNA sequences of fifty-five species, with” alignments of sequences encoding five transfer RNAs […] constructed on the basis of secondary models” .

7. Imagine that the phylogeny in Figure 1A looked like the phylogeny in Figure 1B, and the phylogeny in Figure 1B looked like that in Figure 1A. Would the Losos and colleagues conclusion remain the same or would it change? Explain.
[add answer here…damned if I know! I think it would mean that there were many, and frequent diversions in the evolutionary paths of the lizards in the different geographical areas and, thus, the conclusion would be an agreement that evolutionary paths vary regardly of common starting conditions]

8. In Figure 1C, why is it important that the sequence of evolution of the different ecomorph classes is different?
It is important because it shows that the niches are all similarly satisfied; that is to say that the relatively stable status quo is common to all topologies. All four general niches are satisfied on all four islands regardless of the order in which the ecomorphs emerged.

9. What is constraint? Why are Losos and colleagues worried about the diversity of Anoles being “constrained” to these different ecotypes? How does this challenge their hypothesis?
It can be suggested that the Anoles are only capable of evolving into certain classes of ecomorphs; a specific range of ecotypes. Were this is case, one could argue that it is not adaptation to environment that brings about similar ecotypes amongst the species but rather a fulfillment of the natural evolutionary progression of the Anole leading to its culmination of four specific ecotypes. Losos and colleagues argue that this is not the case, citing examples of species that are not among the noted ecomorhpic classes.

10. The paper ends on Page 2117 by stating that “the importance of historical contingency depends on the frame of reference:” what do Losos and colleagues mean by this statement?
Losos and colleagues suggest that the lack of importance of historical contingency on this experiment may be related to the setting of the test. Inter-island we find that the evolutionary ecomorphic changes came to similar result, but were we to look intra-island we would find that the prior evolutionary events hold great significance with regards to future evolutionary trends.
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