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Recent ecological divergence despite migration in sockeye salmon (Oncorhynchus nerka).

Pavey SA, Nielsen JL, Hamon TR - Evolution (2009)

Bottom Line: Ecological divergence may result when populations experience different selection regimes, but there is considerable discussion about the role of migration at the beginning stages of divergence before reproductive isolating mechanisms have evolved.Although studies of fish divergence following the retreat of glaciers (10,000-15,000 years ago) have contributed extensively to our understanding of speciation, the Aniakchak system of sockeye salmon provides a rare example of the initial stages of ecological divergence following natural colonization.Our results show that even in the face of continued migration, populations may diverge in the absence of a physical barrier.

View Article: PubMed Central - PubMed

Affiliation: Biological Sciences Department, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada. spavey@sfu.ca

ABSTRACT
Ecological divergence may result when populations experience different selection regimes, but there is considerable discussion about the role of migration at the beginning stages of divergence before reproductive isolating mechanisms have evolved. However, detection of past migration is difficult in current populations and tools to differentiate genetic similarities due to migration versus recent common ancestry are only recently available. Using past volcanic eruption times as a framework, we combine morphological analyses of traits important to reproduction with a coalescent-based genetic analysis of two proximate sockeye salmon (Oncorhynchus nerka) populations. We find that this is the most recent (approximately 500 years, 100 generations) natural ecological divergence recorded in a fish species, and report that this divergence is occurring despite migration. Although studies of fish divergence following the retreat of glaciers (10,000-15,000 years ago) have contributed extensively to our understanding of speciation, the Aniakchak system of sockeye salmon provides a rare example of the initial stages of ecological divergence following natural colonization. Our results show that even in the face of continued migration, populations may diverge in the absence of a physical barrier.

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Posterior probability distributions for time since divergence in years. All three runs of the IM program are illustrated; run 1 is black dashed, run 2 is black, run 3 is gray. The inset is an enlargement of years 1–1000.
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fig05: Posterior probability distributions for time since divergence in years. All three runs of the IM program are illustrated; run 1 is black dashed, run 2 is black, run 3 is gray. The inset is an enlargement of years 1–1000.

Mentions: High point estimates of the posterior probability of the time since onset of divergence ranged from 47 to 123 years prior to sample collection (Table 4, Fig. 5), however, runs 2 and 3 exhibited two and three peaks, respectively, and all peaks occurred between 47 and 400 years prior to sample collection. Mean distribution values of the entire posterior probability distributions for divergence times ranged between 389 and 503 years ago (Table 4). It is important to note that with all of the posterior probabilities, the y-axis scale is completely dependent on the number of bins in the x-axis (1000). The area under the curve is equal to one.


Recent ecological divergence despite migration in sockeye salmon (Oncorhynchus nerka).

Pavey SA, Nielsen JL, Hamon TR - Evolution (2009)

Posterior probability distributions for time since divergence in years. All three runs of the IM program are illustrated; run 1 is black dashed, run 2 is black, run 3 is gray. The inset is an enlargement of years 1–1000.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2901516&req=5

fig05: Posterior probability distributions for time since divergence in years. All three runs of the IM program are illustrated; run 1 is black dashed, run 2 is black, run 3 is gray. The inset is an enlargement of years 1–1000.
Mentions: High point estimates of the posterior probability of the time since onset of divergence ranged from 47 to 123 years prior to sample collection (Table 4, Fig. 5), however, runs 2 and 3 exhibited two and three peaks, respectively, and all peaks occurred between 47 and 400 years prior to sample collection. Mean distribution values of the entire posterior probability distributions for divergence times ranged between 389 and 503 years ago (Table 4). It is important to note that with all of the posterior probabilities, the y-axis scale is completely dependent on the number of bins in the x-axis (1000). The area under the curve is equal to one.

Bottom Line: Ecological divergence may result when populations experience different selection regimes, but there is considerable discussion about the role of migration at the beginning stages of divergence before reproductive isolating mechanisms have evolved.Although studies of fish divergence following the retreat of glaciers (10,000-15,000 years ago) have contributed extensively to our understanding of speciation, the Aniakchak system of sockeye salmon provides a rare example of the initial stages of ecological divergence following natural colonization.Our results show that even in the face of continued migration, populations may diverge in the absence of a physical barrier.

View Article: PubMed Central - PubMed

Affiliation: Biological Sciences Department, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada. spavey@sfu.ca

ABSTRACT
Ecological divergence may result when populations experience different selection regimes, but there is considerable discussion about the role of migration at the beginning stages of divergence before reproductive isolating mechanisms have evolved. However, detection of past migration is difficult in current populations and tools to differentiate genetic similarities due to migration versus recent common ancestry are only recently available. Using past volcanic eruption times as a framework, we combine morphological analyses of traits important to reproduction with a coalescent-based genetic analysis of two proximate sockeye salmon (Oncorhynchus nerka) populations. We find that this is the most recent (approximately 500 years, 100 generations) natural ecological divergence recorded in a fish species, and report that this divergence is occurring despite migration. Although studies of fish divergence following the retreat of glaciers (10,000-15,000 years ago) have contributed extensively to our understanding of speciation, the Aniakchak system of sockeye salmon provides a rare example of the initial stages of ecological divergence following natural colonization. Our results show that even in the face of continued migration, populations may diverge in the absence of a physical barrier.

Show MeSH
Related in: MedlinePlus