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Environment, but not genetic divergence, influences geographic variation in colour morph frequencies in a lizard.

McLean CA, Stuart-Fox D, Moussalli A - BMC Evol. Biol. (2015)

Bottom Line: Despite genetic structure among populations, there was no relationship between genetic similarity or geographic proximity and similarity in morph frequencies.Spatial variation in selection appears to play an important role in shaping morph frequency patterns in C. decresii.Selection associated with differences in local environmental conditions, combined with relatively low levels of gene flow, is expected to favour population divergence in morph composition, but may be counteracted by negative frequency-dependent selection favouring rare morphs.

View Article: PubMed Central - PubMed

Affiliation: School of BioSciences, The University of Melbourne, Parkville, VIC, 2010, Australia. mcleanca@unimelb.edu.au.

ABSTRACT

Background: Identifying the causes of intraspecific phenotypic variation is essential for understanding evolutionary processes that maintain diversity and promote speciation. In polymorphic species, the relative frequencies of discrete morphs often vary geographically; yet the drivers of spatial variation in morph frequencies are seldom known. Here, we test the relative importance of gene flow and natural selection to identify the causes of geographic variation in colour morph frequencies in the Australian tawny dragon lizard, Ctenophorus decresii.

Results: Populations of C. decresii are polymorphic for male throat coloration and all populations surveyed shared the same four morphs but differed in the relative frequencies of morphs. Despite genetic structure among populations, there was no relationship between genetic similarity or geographic proximity and similarity in morph frequencies. However, we detected remarkably strong associations between morph frequencies and two environmental variables (mean annual aridity index and vegetation cover), which together explained approximately 45 % of the total variance in morph frequencies.

Conclusions: Spatial variation in selection appears to play an important role in shaping morph frequency patterns in C. decresii. Selection associated with differences in local environmental conditions, combined with relatively low levels of gene flow, is expected to favour population divergence in morph composition, but may be counteracted by negative frequency-dependent selection favouring rare morphs.

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Related in: MedlinePlus

STRUCTURE analysis figures showing hierarchical levels of population structure. Individual assignment probabilities are for aK = 2 bK = 3 cK = 3 and dK = 2. Populations are: Yourambulla Caves (YC), Aroona (A), Warren Gorge (WG), Devil’s Peak (DP), Mt Remarkable (MR), Telowie Gorge (TG), Wilpena (W), and Bimbowrie Station (BS)
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Fig2: STRUCTURE analysis figures showing hierarchical levels of population structure. Individual assignment probabilities are for aK = 2 bK = 3 cK = 3 and dK = 2. Populations are: Yourambulla Caves (YC), Aroona (A), Warren Gorge (WG), Devil’s Peak (DP), Mt Remarkable (MR), Telowie Gorge (TG), Wilpena (W), and Bimbowrie Station (BS)

Mentions: There was genetic subdivision between populations of C. decresii. Although pairwise FST values were low to moderate (ranging from 0.013–0.068), they were statistically significant for all population pairs (with the exception of Mt Remarkable and Telowie Gorge; Additional file 6: Table S5). Genetic similarity did not necessarily reflect geographic proximity as population structure did not conform to a model of isolation by distance (rpartial = 0.274, P = 0.171; Additional file 2: Figure S1). The highest ΔK value from the initial STRUCTURE analysis was for K = 2 (ΔK = 22.01, mean likelihood of K = −9901), with Yourambulla Caves forming a separate cluster from all other populations (Fig. 2a). The subsequent analysis excluding Yourambulla Caves inferred three clusters (K = 3: ΔK = 4.33, mean likelihood of K = −8484; Fig. 2b): Aroona/Warren Gorge/Devil’s Peak, Mt Remarkable/Telowie Gorge and Wilpena/Bimbowrie Station. With the exception of Mt Remarkable/Telowie Gorge, these clusters were further separated into individual populations in the final STRUCTURE analyses (Fig. 2c, d).Fig. 2


Environment, but not genetic divergence, influences geographic variation in colour morph frequencies in a lizard.

McLean CA, Stuart-Fox D, Moussalli A - BMC Evol. Biol. (2015)

STRUCTURE analysis figures showing hierarchical levels of population structure. Individual assignment probabilities are for aK = 2 bK = 3 cK = 3 and dK = 2. Populations are: Yourambulla Caves (YC), Aroona (A), Warren Gorge (WG), Devil’s Peak (DP), Mt Remarkable (MR), Telowie Gorge (TG), Wilpena (W), and Bimbowrie Station (BS)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4528382&req=5

Fig2: STRUCTURE analysis figures showing hierarchical levels of population structure. Individual assignment probabilities are for aK = 2 bK = 3 cK = 3 and dK = 2. Populations are: Yourambulla Caves (YC), Aroona (A), Warren Gorge (WG), Devil’s Peak (DP), Mt Remarkable (MR), Telowie Gorge (TG), Wilpena (W), and Bimbowrie Station (BS)
Mentions: There was genetic subdivision between populations of C. decresii. Although pairwise FST values were low to moderate (ranging from 0.013–0.068), they were statistically significant for all population pairs (with the exception of Mt Remarkable and Telowie Gorge; Additional file 6: Table S5). Genetic similarity did not necessarily reflect geographic proximity as population structure did not conform to a model of isolation by distance (rpartial = 0.274, P = 0.171; Additional file 2: Figure S1). The highest ΔK value from the initial STRUCTURE analysis was for K = 2 (ΔK = 22.01, mean likelihood of K = −9901), with Yourambulla Caves forming a separate cluster from all other populations (Fig. 2a). The subsequent analysis excluding Yourambulla Caves inferred three clusters (K = 3: ΔK = 4.33, mean likelihood of K = −8484; Fig. 2b): Aroona/Warren Gorge/Devil’s Peak, Mt Remarkable/Telowie Gorge and Wilpena/Bimbowrie Station. With the exception of Mt Remarkable/Telowie Gorge, these clusters were further separated into individual populations in the final STRUCTURE analyses (Fig. 2c, d).Fig. 2

Bottom Line: Despite genetic structure among populations, there was no relationship between genetic similarity or geographic proximity and similarity in morph frequencies.Spatial variation in selection appears to play an important role in shaping morph frequency patterns in C. decresii.Selection associated with differences in local environmental conditions, combined with relatively low levels of gene flow, is expected to favour population divergence in morph composition, but may be counteracted by negative frequency-dependent selection favouring rare morphs.

View Article: PubMed Central - PubMed

Affiliation: School of BioSciences, The University of Melbourne, Parkville, VIC, 2010, Australia. mcleanca@unimelb.edu.au.

ABSTRACT

Background: Identifying the causes of intraspecific phenotypic variation is essential for understanding evolutionary processes that maintain diversity and promote speciation. In polymorphic species, the relative frequencies of discrete morphs often vary geographically; yet the drivers of spatial variation in morph frequencies are seldom known. Here, we test the relative importance of gene flow and natural selection to identify the causes of geographic variation in colour morph frequencies in the Australian tawny dragon lizard, Ctenophorus decresii.

Results: Populations of C. decresii are polymorphic for male throat coloration and all populations surveyed shared the same four morphs but differed in the relative frequencies of morphs. Despite genetic structure among populations, there was no relationship between genetic similarity or geographic proximity and similarity in morph frequencies. However, we detected remarkably strong associations between morph frequencies and two environmental variables (mean annual aridity index and vegetation cover), which together explained approximately 45 % of the total variance in morph frequencies.

Conclusions: Spatial variation in selection appears to play an important role in shaping morph frequency patterns in C. decresii. Selection associated with differences in local environmental conditions, combined with relatively low levels of gene flow, is expected to favour population divergence in morph composition, but may be counteracted by negative frequency-dependent selection favouring rare morphs.

Show MeSH
Related in: MedlinePlus