Biogeography
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CONTINENTAL DRIFT ANIMATION – A HISTORY OF ISOLATION AND CONTACT
Biogeographers have long commented on the similarities (affinities) vs. differences among terrestrial fauna and
flora of the various continents. Strong affinities among continents would suggest they have been in close enough
contact for long enough – either currently or times in the past – for sufficient dispersal to occur and/or gene flow
across the range of a species. The presence of strong differences in flora and fauna, on the other hand, suggest
that continents are or have been sufficiently isolated – limiting the flow of organisms and genetic information
(reproductive isolation) – so that evolution has taken different paths.
In this exercise, you will be able to explore how physiographic relationships have developed and perhaps reversed
over geologic time, and consider their consequences for the geography of the Earth’s biodiversity.
1) Open the file: ContDrift-animationW&P.pdf [Opens in Full Screen view – to return view to within a Window,
hit Esc, or right click & select “Exit ...”]. You may also wish to refer to the sequence in your text on pp. 252255 (Fig. 8.15) in conjunction with the text (pp. 270-274) and Tables 8.2 & 8.3 (e.g., re concurrent Biotic
events in Table 8.3, rightmost column).
Use the arrow keys to roll through the animation. Roll forward, and then step backward to gain insights as to
when current continents were more or less connected to each other.
2) Also, look at online versions of the last 750 Myr of continental arrangements; e.g., at:
http://www.scotese.com/pangeanim.htm - select era (VR tabs), and drag mouse across map displayed below the
tabs)
3) Use the following guide and questions to help you explore the animations and discern relationships:
1) Record when (i) Africa & South America separate, (ii) the Isthmus of Panama forms, and (iii) different parts
of present-day Eurasia coalesce – focus on both Asian & European terranes.
2) Record when these physiographic relationships form relative to the origin of (i) seed plants (beginnings of
conifers) and from these origins, (ii) flowering plants, and (iii) most modern mammals.
3) In the periods that follow the changes in (1), which continents (or continents to be) maintain the closest
connections? Which are more isolated?
a) Based on your assessment, which sets of continents are most likely to have the strongest modern-day
affinities in terrestrial flora & fauna? And which the greatest degree of endemism (at the continental
scale)?
b) Do these patterns suggest the current distribution of most placental vs. marsupial mammals?
4) Would you expect these relationships to vary by groups of organisms – how & why? That is, might two
continents have strong affinities for some types of organisms and show strong divergence in others?
5) What other broad-scale factors, might play a role in affinities and divergence in the biota of continents?
Recall what is it about continental drift that plays a role in biodiversity.
Biogeography
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6) Consider the following biogeographic patterns:
a) Why do South America, Africa, and Australasia have relatively high floral affinities?
b) Wallace’s Line, running through the middle of Indonesia, distinguishes faunal affinities of Indo-Malaysia
vs. of Australasia – even though Indonesia is a string of closely spaced islands. Why might this have
come about? You may wish to refer to your text’s discussion of Wallace’s Line (pp. 284-285, Fig. 9.9).
c) Consider migratory patterns. Can you imagine how both birds and marine turtles many have been
affected by the changes in geography over the past 100 million years? Might these changes in geography
result in speciation of migratory species?
d) Did the union of continents (e.g., India with Asia, and connection of North and South America) serve to
generate new species? Or did species go extinct? Explain why. For example, what do you think
happened to South American terrestrial flora and fauna when the Isthmus of Panama formed?
e) The species richness for trees in the deciduous temperate forests of Europe and eastern North America are
depauperate relative to those in east Asia (see table; note forests are roughly the same in area). This is
suggested to be because European & North American temperate areas were separated from tropical
regions 30Mya (see figure) – can you think of why in contrast such connection might have made a
difference in Asia?
f) What effect, if any, might the formation of the Isthmus of Panama and the closing of the Tethys Sea have
had upon global climate? You may wish to refer to your text, Tables 8.2 and 8.3.
g) Over the next 250 million years, a future prediction (http://www.scotese.com/futanima.htm) is for, first,
Australia to run into East Asia, and eventually all continents to coalesce once again into one
supercontinent. Will there be greater or lesser richness when Australia & Asia connect and the
earth has one landmass – the return of Pangea. (think about the Habitat Fragmentation & Island
Biogeography)? Do you think current, anthropogenic global transportation is virtually creating
one continental landmass by permitting easy or increased transmission of species? List some
examples.
A Chmura 8/05, rev T Kittel 3/10