 |
|
| Science Forum Index » Bio Evolution Forum » Paper: Adaptation by introgression... |
|
Page 1 of 1 |
|
| Author |
Message |
| Robert Karl Stonjek... |
 Posted: Sun Oct 18, 2009 5:30 pm |
|
|
|
Guest
|
Adaptation by introgression
Michael L Arnold 1 and Noland H Martin 2
1 Department of Genetics, University of Georgia, Athens, Georgia 30602, USA
2 Department of Biology, Texas State University, San Marcos, Texas 78666,
USA
Journal of Biology 2009, 8:82doi:10.1186/jbiol176
The electronic version of this article is the complete one and can be found
online at: http://jbiol.com/content/8/9/82
Published: 13 October 2009
© 2009 BioMed Central Ltd
Abstract
Both selective and random processes can affect the outcome of natural
hybridization. A recent analysis in BMC Evolutionary Biology of natural
hybridization between an introduced and a native salamander reveals the
mosaic nature of introgression, which is probably caused by a combination of
selection and demography.
Minireview
Natural interspecific hybridization has been observed in a diverse array of
taxa, and the production of such hybrids can have a wide range of
evolutionary consequences. For instance, natural hybridization can act as a
'destructive' force, resulting in the fusion of taxa that do not reveal
strong reproductive isolation. Alternatively, it can result in evolutionary
novelty via the production of new reproductively isolated hybrid species, or
by the transfer of potentially adaptive traits through a process known as
introgressive hybridization. In a recent article in BMC Evolutionary
Biology, Fitzpatrick et al. tested for introgressive hybridization by
performing a genome-wide scan of native salamander (Ambystoma californiense)
populations, and identified genomic regions that have rapidly fixed
alternative alleles derived from a recently introduced, invasive species
(Ambystoma mavortium). This rapid assimilation of non-native alleles
suggests that selective processes were involved in their fixation.
Introgressive hybridization is a multi-step process by which genetic
material from one population infiltrates into another, genetically
differentiated population. In order for introgressive hybridization to take
place, F1 hybrids must initially be produced between the two species. In
nature, such hybrid formation is often a rare event owing to the presence of
multiple prezygotic and postzygotic reproductive barriers, and indeed in
most species-pairs studied to date, the frequencies of F1 hybrid formation
are low. However, even if the F1 hybrids possess only partial fitness, they
may mate with one or both progenitor species to produce first-generation
backcross (BC1) hybrids. These BC1 hybrids may further backcross with
pure-species individuals, ultimately resulting in the transfer of novel
alleles between the hybridizing lineages/species.
A key question with respect to introgressive hybridization is 'To what
degree is interspecific gene flow the result of adaptive processes?' Whereas
hybridization can certainly result in the transfer of alleles and traits
across species boundaries, such genetic exchange does not necessarily
involve the transfer of adaptations. Stochastic processes (that is, random
genetic drift) could potentially explain introgression events, and
deciphering the roles of stochastic and deterministic (that is, natural
selection) processes has often proved difficult. Only a handful of examples
are currently available that provide rigorous tests for adaptive
introgression. Given the scarcity of such analyses, the recent study of
Fitzpatrick et al. reporting on signatures of adaptive introgression in
salamanders is a significant contribution. Here, we review four examples
(including) that have used four different methodologies to test for adaptive
introgression.
Source: Journal of Biology [Open Access]
http://jbiol.com/content/8/9/82
Posted by
Robert Karl Stonjek |
|
|
| Back to top |
|
|
|
|
|
All times are GMT - 5 Hours
The time now is Fri Mar 12, 2010 12:04 am
|
|