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Signatures of selection in the three-spined stickleback along a small-scale brackish water - freshwater transition zone.

Konijnendijk N, Shikano T, Daneels D, Volckaert FA, Raeymaekers JA - Ecol Evol (2015)

Bottom Line: However, the detected loci appear repeatedly as targets of selection in similar studies of genomic adaptation in the three-spined stickleback.We conclude that the signature of genomic selection in the face of strong gene flow is weak, yet detectable.We argue that the range of studies of genomic divergence should be extended to include more systems characterized by limited geographical and ecological isolation, which is often a realistic setting in nature.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Biodiversity and Evolutionary Genomics University of Leuven Ch. Deberiotstraat 32, B-3000 Leuven Belgium.

ABSTRACT
Local adaptation is often obvious when gene flow is impeded, such as observed at large spatial scales and across strong ecological contrasts. However, it becomes less certain at small scales such as between adjacent populations or across weak ecological contrasts, when gene flow is strong. While studies on genomic adaptation tend to focus on the former, less is known about the genomic targets of natural selection in the latter situation. In this study, we investigate genomic adaptation in populations of the three-spined stickleback Gasterosteus aculeatus L. across a small-scale ecological transition with salinities ranging from brackish to fresh. Adaptation to salinity has been repeatedly demonstrated in this species. A genome scan based on 87 microsatellite markers revealed only few signatures of selection, likely owing to the constraints that homogenizing gene flow puts on adaptive divergence. However, the detected loci appear repeatedly as targets of selection in similar studies of genomic adaptation in the three-spined stickleback. We conclude that the signature of genomic selection in the face of strong gene flow is weak, yet detectable. We argue that the range of studies of genomic divergence should be extended to include more systems characterized by limited geographical and ecological isolation, which is often a realistic setting in nature.

No MeSH data available.


Map with the four sampling locations of three‐spined sticklebacks in northwestern Belgium and the southwestern Netherlands. River network and major towns are mapped.
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ece31671-fig-0001: Map with the four sampling locations of three‐spined sticklebacks in northwestern Belgium and the southwestern Netherlands. River network and major towns are mapped.

Mentions: Three‐spined sticklebacks (Gasterosteus aculeatus L.; Gasterosteidae) from the coastal lowlands (polder) of Belgium and the Netherlands (Fig. 1) reside in ponds, ditches, streams, estuaries, or polder creeks. They have an anadromous or landlocked life style (Heuts 1947; Wootton 1976; Raeymaekers et al. 2005, 2007). The polder and surrounding areas contain diked brackish and freshwater habitats of Holocene origin with varying levels of connectivity to adjacent estuaries and the open sea. Populations that live in close proximity to the sea (<10 km) reside in brackish water, of which the salinity is influenced by rainfall and water management. On a scale of less than 50 km further inland, salinity drops to freshwater levels (Raeymaekers et al. 2014). Lateral plate number, an important ecological trait, also decreases with distance to the coast, with population averages ranging between 5 and 20 (Heuts 1947; Raeymaekers et al. 2014). Populations bordering the North Sea and the Baltic are typically polymorphic for lateral plate number (Heuts 1947; Raeymaekers et al. 2014), so higher or lower population averages are rare. This range is therefore representative for the phenotypic extremes we can find in this part of the stickleback's distribution range.


Signatures of selection in the three-spined stickleback along a small-scale brackish water - freshwater transition zone.

Konijnendijk N, Shikano T, Daneels D, Volckaert FA, Raeymaekers JA - Ecol Evol (2015)

Map with the four sampling locations of three‐spined sticklebacks in northwestern Belgium and the southwestern Netherlands. River network and major towns are mapped.
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4588664&req=5

ece31671-fig-0001: Map with the four sampling locations of three‐spined sticklebacks in northwestern Belgium and the southwestern Netherlands. River network and major towns are mapped.
Mentions: Three‐spined sticklebacks (Gasterosteus aculeatus L.; Gasterosteidae) from the coastal lowlands (polder) of Belgium and the Netherlands (Fig. 1) reside in ponds, ditches, streams, estuaries, or polder creeks. They have an anadromous or landlocked life style (Heuts 1947; Wootton 1976; Raeymaekers et al. 2005, 2007). The polder and surrounding areas contain diked brackish and freshwater habitats of Holocene origin with varying levels of connectivity to adjacent estuaries and the open sea. Populations that live in close proximity to the sea (<10 km) reside in brackish water, of which the salinity is influenced by rainfall and water management. On a scale of less than 50 km further inland, salinity drops to freshwater levels (Raeymaekers et al. 2014). Lateral plate number, an important ecological trait, also decreases with distance to the coast, with population averages ranging between 5 and 20 (Heuts 1947; Raeymaekers et al. 2014). Populations bordering the North Sea and the Baltic are typically polymorphic for lateral plate number (Heuts 1947; Raeymaekers et al. 2014), so higher or lower population averages are rare. This range is therefore representative for the phenotypic extremes we can find in this part of the stickleback's distribution range.

Bottom Line: However, the detected loci appear repeatedly as targets of selection in similar studies of genomic adaptation in the three-spined stickleback.We conclude that the signature of genomic selection in the face of strong gene flow is weak, yet detectable.We argue that the range of studies of genomic divergence should be extended to include more systems characterized by limited geographical and ecological isolation, which is often a realistic setting in nature.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Biodiversity and Evolutionary Genomics University of Leuven Ch. Deberiotstraat 32, B-3000 Leuven Belgium.

ABSTRACT
Local adaptation is often obvious when gene flow is impeded, such as observed at large spatial scales and across strong ecological contrasts. However, it becomes less certain at small scales such as between adjacent populations or across weak ecological contrasts, when gene flow is strong. While studies on genomic adaptation tend to focus on the former, less is known about the genomic targets of natural selection in the latter situation. In this study, we investigate genomic adaptation in populations of the three-spined stickleback Gasterosteus aculeatus L. across a small-scale ecological transition with salinities ranging from brackish to fresh. Adaptation to salinity has been repeatedly demonstrated in this species. A genome scan based on 87 microsatellite markers revealed only few signatures of selection, likely owing to the constraints that homogenizing gene flow puts on adaptive divergence. However, the detected loci appear repeatedly as targets of selection in similar studies of genomic adaptation in the three-spined stickleback. We conclude that the signature of genomic selection in the face of strong gene flow is weak, yet detectable. We argue that the range of studies of genomic divergence should be extended to include more systems characterized by limited geographical and ecological isolation, which is often a realistic setting in nature.

No MeSH data available.