Biology Reference
In-Depth Information
of evolution or because no close relatives were sampled for particular species on
the tree. As noted by
Telford and Copley (2011)
, when the long-branch attraction
issue was resolved using a better model, nematodes and arthropods were found
to be closely related, supporting the Ecdysozoa hypothesis.
Huerta-Cepas et al. (2011)
provide a repository for alignments based on
whole-genome sequences, which allows additional analyses to be conducted
using the alignments used by others.
Rokas and Abbott (2009)
discuss the
experimental design and concepts associated with analysis of whole-genome
sequences.
Rokas and Abbott (2009)
concluded that Next-Generation sequenc-
ing will soon “transform ecology and evolution by fundamentally changing the
ranges and types of questions that can be addressed.”
12.10 Molecular Evolution and Speciation
The concept of species is inherent to the study of evolution and to understand-
ing the evolution of life. Species concepts, definitions, and origins, however,
remain controversial (
Hey 2001, Margulis and Sagan 2002, de Meeus et al. 2003,
Hey 2006, Winker et al. 2007, Coleman 2009, Nosil et al. 2009, Faria and Navarro
2010, Marie Curie SPECIATION Network 2012
).
Winker et al. (2007)
, “maintain
that the inherent subjectivity within all species concepts is likely to ensure con-
tinued disagreement on where to place species limits.”
de Meeus et al. (2003)
note, “Species are entities that can be discriminated from one another, follow-
ing criteria that seem the most appropriate at one place in time and space, and
for one class of organisms.”
12.10.1 Species Concepts
One of the central questions of biology is how a continuous process of evolution
can produce species (
Coyne 1992, Rice and Hostert 1993, O'Hara 1994, Hollocher
1998, Hey 2001, Noor 2002, de Meeus et al. 2003
). There are multiple views of
“species” (
Table 12.5
). The
biological species concept
indicates that, “Species are
groups of actually or potentially interbreeding natural populations, which are
reproductively isolated from other such groups” (
Mayr 1970
). Reproductive isola-
tion is achieved by
prezygotic isolating factors
(mating discrimination, different
habitat preferences) and
postzygotic isolating factors
(hybrid inviability, sterility).
Reproductive isolation, in concert with selection and genetic drift, creates and
expands the morphological differences between species living in the same area.
Physical isolation (
allopatry
) leads inevitably to evolutionary change through
natural selection or drift, and pre- or postmating reproductive isolation mech-
anisms evolve as a by-product of the genetic changes. Any resultant hybrid
