Chapter 11 Synthesis: Biogeographic and Macroevolutionary Implicaitons

Brown begins this chapter with giving us a brief overview of the ecological limits on geographic ranges. Boundaries of species are determined by ecological limits. These ecological limits are defined by the interactions between niche requirements of the individual and the abiotic and biotic characteristics of their environment. Three points about the ecology of range boundaries are pointed out: First, these ranges are dynamic; they fluctuate in space and time. Second, environmental conditions that set these ranges are defined by biogeographers as barriers. These barriers can follow two hypothesis: the disperalist or vicariance hypothesis. The third point states that all range boundaries are ultimately set by abiotic conditions. Brown then goes into some detail about the importance of "history". Specifically, the history of a place that has lead to it's characteristic components it is today. And the history of lineage; which is the sequence of speciation and extinction that has occurred since the descent from a common ancestor.

The next part of the chapter Brown discusses macroevolutionary and macroecological implications. The term macroevolution was coined in the 1970's by some paleontologists to be the large-scale, long-term patterns and processes in the evolution of lineages revealed to us through the fossil record. The macroevolutionary research program centered itself around two concepts: punctuated equilibrium, and species selection. The concept of species selection is what Brown likes to call species dynamics. Species dynamics is natural selection operating on the individual level. Darwin's four conditions of evolutionary change persist at the level of an individual, and if these conditions are met then descent with modification (aka natural selection, or speciation) will occur. Three major evolutionary forces act on individuals: drift, migration, and selection. Among these three selection can be considered the most complex force playing on a species. This is where we see "emergent" traits acting on species selection. Brown states that emergent traits can be mean body mass, sex ratio, age structure, variance in male reproductive success, average population density, area of geographic range, and time from divergence of most closely related species. Thinking about emergent traits, could we say that everything about that species physiology and morphology is made up of emergent traits? Or basically, what makes a species it's unique self is made up of emergent traits? I think so, however this emergent trait must allow positive benefits for future generations in order for it to be considered emergent, do you agree?

This brings us to macroecology and the environmental filter. Looking into the fossil record there is evidence for species selection. There is also evidence as to what traits are associated with success or failure of a given lineage. My personal favorite is the explosive speciation of Cichlid fishes in the Great Lakes of Central Africa. Whenever species selection does occur, it is the environment that determines whether this species will persist, will have to move its range, or it will become extinct. The mechanisms that act on a species to determine whether they survive, have a background extinction, or they undergo mass extinction depends largely on the dynamics of the individuals. Such mechanisms include body size, generalist or specialist characteristics, but overall the species ability to evolve accordingly. I will end this summary with my favorite quote from the chapter: "To a large extent, the game of life played by all organisms is a competitive contest to obtain a share of this productivity, and relative success is measured by the size of the share". I apologize this summary is scattered and not good, #1 I wanted to summarize every detail given to us and didn't know where to start, and #2 a lot of this chapter I wanted to discuss with everyone instead of blogging it!

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Biogeography and Evolution of Abies (Pinaceae) in the Mediterranean Basin: the Roles of Long-term Climatic Change and Glacial Refugi

Juan Carlos Linares

Journal of Biogeography 2011, Vol. 38 pg's 619-630

Coolest thing about this article: It took microecological studies and made a macroecological compilation on the evolution of Abies species. I thought it was appropriate considering we discussed in class last week the call to compile small scale studies into a macro assessment! Linares summarized current data on the origin and evolution of genus Abies in the Mediterranean basin and made a comprehensive analysis regarding the isolation and speciation patterns of the firs found in this basin. He reviewed all the studies on Abies genus in the Mediterranean, primarily focusing on morphology, molecular ecology, phytosociology, and biogeography present today and in the fossil record. He found that Abies have undergone evolutionary changes that don't necessarily point to reproductive isolation being the mechanism behind this. He did find that long-term dryness caused an initial Miocene-Pliocene speciation event. And in the Pleistocene, the glacial cycles forced species migrations to occur and caused contact to be repeated and constant between fir species. I thought this paper was a bit on the wordy side and slightly confusing to a non-plant lover. However, its maybe appropriate to include the plants and not talk about animals all the time!

Sorry about the late and scattered post! See you guys tomorrow!