Evolution, 4th Edition

■■Biogeography, the study of organisms’ geo-

graphic distributions, has both historical and

ecological components. Certain distributions

are the consequence of long-term evolutionary

history; others are the result of current ecological

factors.

■■The geographic distributions of organisms

provided Darwin and Wallace with some of their

strongest evidence for the reality of evolution.

■■The historical processes that affect the dis-

tribution of a taxon are extinction, dispersal,

and vicariance (fragmentation of a continuous

distribution by the emergence of a barrier).

These processes may be affected or accompa-

nied by environmental change, adaptation, and

speciation.

■■Histories of dispersal or vicariance can often be

inferred from phylogenetic data.

■■Disjunct distributions are attributable in some

instances to vicariance, but dispersal seems to be

the more common cause.

■■Genetic patterns of geographic variation within

species can provide information on historical

changes in a species’ distribution.

■■The local distribution of species is affected by

ecological factors, including both abiotic aspects

of the environment and biotic features such as

competitors and predators. Why species do not

enlarge their ranges indefinitely, by incremen-

tally adapting to conditions farther and farther

away, is a major question in evolutionary biology.

■■Geographic patterns in the number and diver-

sity of species may stem partly from current

ecological factors, but long-term evolutionary

history also may explain them.

TERMS AnD ConCEPTS

biogeographic

realm

biogeography

competitive

exclusion

principle

disjunct distribution

dispersal

ecological

biogeography

endemic

fundamental

ecological niche

historical

biogeography

phylogenetic niche

conservatism

phylogeography

vicariance

Wallace’s line

SuGGESTionS foR fuRTHER READinG

M. v. lomolino, B. R. Riddle, R. J. Whittaker, and

J. H. Brown, Biogeography, 5th edition (Sinau-

er Associates, Sunderland, MA, 2017), is the

leading textbook of biogeography.

A. de Queiros has written about the role of

dispersal in the evolution of distributions in a

book for a general audience, The Monkey’s

Voyage: How Improbable Journeys Shaped

the History of Life (Basic Books, new york,

2014).

Phylogeography is treated in depth by J. C.

Avise in Phylogeography (Harvard university

Press, Cambridge, MA, 2000), and human

phylogeography is included in E. E. Harris’s

Ancestors in Our Genome: The New Science

of Human Evolution (oxford university Press,

oxford, uK, 2015).

PRoBlEMS AnD DiSCuSSion ToPiCS

1. until recently, the plant family Dipterocarpaceae
   was thought to be restricted to tropical Asia,
   where many species are ecologically domi-
   nant trees. However, a new species of tree in
   this family was discovered in the rainforest of
   Colombia, in northern South America. What
   hypotheses could account for this tree’s pres-
   ence in South America, and how could you test
   those hypotheses?
   2. Except for birds and bats, there are almost no
   native land vertebrates in new Zealand. There is
   one native frog species, a few lizard species, and
   several species of flightless birds. There are no
   snakes, freshwater fishes, or terrestrial mammals.
   What might explain this situation? is this biota
   more likely derived by dispersal from another
   region or by vicariance? What is the significance
   of the missing elements, such as the freshwater
   fishes?

SuMMARy

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