BIOGEOGRAPHY, ETC. Fall 2018
QUESTION SET 3

DUE: 15 November

1. Most higher taxa of animals (all major phyla, most major classes) are apparently of relatively ancient origin, their earliest common ancestors dating to the early Paleozoic (or even latest pre-Cambrian), not long (in the grand context) after multicellular life first appeared.
          A. Give a hypothetical explanation (or two if you can) for why no lineages of more recent origin have gained such status (consider what characteristics a lineage must have to be given phylum or class rank).  Is there a parallel here with adaptive radiations 'within' groups (like the diversification of mammalian orders in late Mesozoic/earliest Cenozoic)?
          B. Is there a way in which you might recognize an existing organism as the likely parent of a future adaptive radiation, or progenitor of a future higher taxon, if you were encounter such a creature now?

2. Here are two tree diagrams showing the relationships within a family of frogs and a family of midges; the members of each family are identified by the land mass on which they live; i.e., the frogs of Europe are most closely related to those of North America (instead of "australia" in each graph read 'the frog (or midge) that lives in australia'). One 'trichotomy' indicates that the sequence of divergence can't be fully resolved. You might find it useful to refer to the sequence of tectonic events in the splitting up of Pangaea.
    A. What's the significance of the similarity between these two trees?  What does it suggest to you about what caused (or allowed) the lineages that now live on these land masses to diverge (with regard to the alternative possibilities of initial allopatry/speciation being result of 'vicariance' or long-distance dispersal)?
    B. Identify where similarity of pattern breaks down, and offer a hypothesis as to what that means, how it might be interpreted.

HYLID FROGS                           MIDGES

3. You now have a historical picture of the world alternating between a condition where most of the land is in a single large land-mass (with lower sea-levels and, therefore, narrower strips of shallow ocean around the continents), and a condition where there are multiple smaller land masses separated by ocean (with higher sea-levels, so with wide areas of flooded continental shelf). Combine this with what you understand about biological processes and patterns like evolution and species-area relationships (review species-area relationship in textbook if called for) to offer hypotheses addressing following questions. You can (re)view paleo-geography of continents and oceans at http://www.scotese.com/ if you want...
             A. How would you expect these changes to have affected diversity patterns and overall diversity in terrestrial biota?
             B. and how might they affect diversity patterns in marine biota (recognizing that much of the diversity in the oceans is in the shallow oceans – that is, on the continental shelves)?

4. Historian Alfred Crosby, in his book "Ecological Imperialism", refers to the effects of the age of exploration and subsequent economic globalization as 'reuniting the seams of Pangaea' -- he draws a parallel between the effects of human activity and plate tectonic cycles, specifically with respect to biological distributions.  What do you suppose he means by this metaphor?  How might it inform our thinking about approaches to conserving global biodiversity?

5.  Caro-Beth Steward, as described in Dawkins and discussed in class, has used the distribution of hominoid fossils as well as distributions of living apes to postulate that an ape that was  common ancestor of chimps, gorillas, and humans, but a sister group to the Asian great apes, dispersed out of Asia and into Africa (the 'out-and-in-and-out-of-Africa hypothesis').  This theory is based primarily on a parsimony argument regarding the number of independent movements between continents required (see the figure in  'The Orang Utan's Tale' -- or the original article (with color figure) here, if you wish).  
A) How might this hypothesis be further tested?  What kinds of evidence would be needed?
B) How would the argument be affected if, say, a fossil apparently related to the orangutan-Sivapithecus clade were found in Africa?