BIOGEOGRAPHY ETC. 2018
FIRST Questions Set

DUE: October 1

NOTE that these are all open-ended sorts of questions.  Don't go overboard.  A medium-length paragraph should allow for sufficient answer on each.  Try to assess what's most important in each case, then construct an argument focusing on what's asked!  (They're mostly not 'look-upable' either; do your best working with the ideas and concepts we have discussed/developed.  Part of the point is to apply approaches and ideas in novel contexts...)

TWO QUESTIONS FOR WORKING WITH BACKGROUND IDEAS about ecology and natural selection

 1. Ecologists typically describe species as either 'specialists' or 'generalists'.  Specialists tend to have relatively specific resource or environment requirements (narrow fundamental niches), but adaptations that make them very effective in competing for these resources or very effective at dealing with environmental constraints.  Generalists have broad fundamental niches -- can use diverse resources, tolerate a wide range of habitat conditions -- but are not particularly effectively adapted to specific conditions (so likely to be competitively excluded by specialists from situations within the specialist's specialty).  Many biologists have suggested that Darwinian selection ought to produce progressively more sophisticated specialization (Dawkins says more specialized 'survival machines' (phenotypes) that serve as vehicles for replicators (genes) that build them).   Of course, more specialized organisms are more vulnerable, over the long term, to extinction as environment changes, but that's not a problem that's generally 'visible' to selection (i.e., risk of eventual extinction doesn't affect individual fitness differences now).  Propose a scenario where selection might favor a more generalist phenotype/genotype over a more specialized one -- i.e., where a more generalist individual might have higher fitness.  What sorts of traits ought to 'go with' a generalist phenotype?  Developmental plasticity -- where the same genotype can produce different phenotypes, but phenotype is 'locked in' over development -- can be regarded as a form of generalization (same genotype can do different things...); does your model suggest insight into adaptive costs and benefits of plasticity? Explain.

2. We have discussed how competitive interactions among organisms may shape their adaptations to reduce overlap in resource use. One result of this is that the niches (range of resources used) of organisms within the same ‘ecological guild’ tend to be separated, or ‘spaced out’ along a gradient of resource quality or type (e.g., size of seeds eaten by granivorous mice and ants). You can ‘place’ more organisms along such a gradient or axis if niches are narrower; conversely, broader fundamental niches will intensify competition and tend to eliminate some species. Imagine a guild of ant species using a range of seed sizes; each species can exploit a certain range of seed sizes, depending on mandible size -- a heritable trait -- and mandible size varies within species. The total range of seed sizes available does not change over time, but other properties of the environment might change. Suggest at least one way you might change environmental circumstances to ‘permit’ more species to persist in coexistence – i.e., ways to allow tighter ‘packing’ of niches without extinction of populations; you can invoke likely selective responses of species (i.e., evolutionary change in mandible size distributions within species).

ISLAND BIOGEOGRAPHY AND SPECIATION:

3. If two sibling lineages are separated geographically, they are likely to diverge evolutionarily.  However, there is no inherent reason why the two populations would develop, while allopatric, a reproductive isolating mechanism (RIM) except by accident (e.g., if they become so different they don't recognize each other as potential mates, or if they've changed morphologically so that mating is impossible).  Suppose that  two such sibling populations have diverged in allopatry due to different types of environmental selection so that they now have significant adaptive phenotypic differences.  Eventually, contact is re-established but there is no RIM - they are still capable of interbreeding (maybe think polar bear and grizzly bear).  Is there reason to anticipate that an RIM might develop secondarily? (AFTER contact is re-established), as a consequence of selection? What would be required for this to occur? Explain (use fitness terminology correctly).

4. Like any basic model, the MacArthur-Wilson equilibrium model of island biogeography can be tricky to apply in real-world situations.  This study looked diversity of anole lizards on Caribbean islands with a focus on how isolation ("distance" in M-W basic model) affects diversity by influencing the rate at which new species are added to the biota of an island: " Helmus, M. R., D. L. Mahler, and J. B. Losos. 2014. "Island biogeography of the Anthropocene". Nature 513:543–546."  Authors encountered three challenges in fitting the model by traditional methods (that is, by assessing the rate of colonization as a function of distance from a mainland/continental source pool in South America).
    * First, other islands can serve as a source of colonists; they may not all come from the single original source
    * Second, human-assisted dispersal: anoles have a habit of hitching rides on ships that pass between the mainland and islands and among islands
    * Third, new species can 'arrive' on an island by speciation - one original population splitting into two or more species within a single island
WITHOUT first reading the article (which you're welcome to do, subsequently, if you want), come up with ways YOU might deal with at least TWO of these problems by either 'controlling' for them or somehow incorporating them into the 'colonization function' of the model (perhaps by re-coding how you assess isolation).

AND ONE MORE:

5. Choose one of the two papers we read and discussed in class (Naka and Brumfield, concerning speciation patterns in Amazonia, and Lomolino, concerning island evolution).  Frame a further research idea based on that study -- a question unanswered, a further implication of findings (explicitly realized by authors or not), or anything else that is somehow rooted in your reading of the article.  State the question and explain how it arises from the reading. See if you can articulate a hypothesis or two to answer the question.  Offer a BRIEF (3-4 sentences maybe) suggestion of a basic research approach to address your question/test your hypothesis.  What kinds of data would you need to collect and what kinds of patterns would your thinking suggest should be seen in those data?