Biology Reference
In-Depth Information
NTP
True
a
a
b
b
c
c
d
d
Fig. 9.
(a) A true evolutionary tree with heterogeneous rates of evolution
between branches and (b) an attempt at reconstruction by a simple clustering NTP
method.
attempt to reconstruct it by a simple clustering NTP method.
b
is phylet-
ically more closely related to
a
than it is to
c
, even though the dissimilar-
ity between
b
and
a
is greater than the one between
b
and
c
. The
dissimilarity between
b
and
c
is small because both have evolved slowly
from their common ancestor at the root of the tree: they look uncannily
similar, despite being on lineages having diverged long ago, because they
are “living fossils”. NTP methods, with the notable exception of NJ, fail
to detect this pitfall and place
b
and
c
together as though they were very
closely related.
4.3. Cladistic Maximum Parsimony (CMP) Methods
The cladistic maximum parsimony (CMP) method and the related
character compatibility (CC) method explicitly reconstruct ancestral
states of characters.
In order to understand how CMP methods work, we need to expand
the terminology concerning ancestral and derived states presented
in Sec. 2.3.
4.3.1. Symplesiomorphy, synapomorphy, and autapomorphy
A symplesiomorphy is a plesiomorphy shared by a number of taxa relative to
the same ancestor (Greek
syn
(“(shared) with”)). A synapomorphy
is an apomorphy shared by a number of taxa relative to the same ancestor
