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Geographical variation in body size and sexual size dimorphism in an Australian lizard, Boulenger's Skink (Morethia boulengeri).

Michael DR, Banks SC, Piggott MP, Cunningham RB, Crane M, MacGregor C, McBurney L, Lindenmayer DB - PLoS ONE (2014)

Bottom Line: Lizards were sexually dimorphic, whereby females had longer snout-vent length than males, providing support for the fecundity selection hypothesis.Body size variation in M. boulengeri was correlated with temperature and rainfall, a pattern consistent with larger individuals occupying cooler and more productive parts of the landscape.Climate change forecasts, which predict warmer temperature and increased aridity, may result in reduced lizard biomass and decoupling of trophic interactions with potential implications for community organization and ecosystem function.

View Article: PubMed Central - PubMed

Affiliation: Fenner School of Environment and Society, ARC Centre of Excellence for Environmental Decisions, and National Environment Research Program, The Australian National University, Canberra, Australia.

ABSTRACT
Ecogeographical rules help explain spatial and temporal patterns in intraspecific body size. However, many of these rules, when applied to ectothermic organisms such as reptiles, are controversial and require further investigation. To explore factors that influence body size in reptiles, we performed a heuristic study to examine body size variation in an Australian lizard, Boulenger's Skink Morethia boulengeri from agricultural landscapes in southern New South Wales, south-eastern Australia. We collected tissue and morphological data on 337 adult lizards across a broad elevation and climate gradient. We used a model-selection procedure to determine if environmental or ecological variables best explained body size variation. We explored the relationship between morphology and phylogenetic structure before modeling candidate variables from four broad domains: (1) geography (latitude, longitude and elevation), (2) climate (temperature and rainfall), (3) habitat (vegetation type, number of logs and ground cover attributes), and (4) management (land use and grazing history). Broad phylogenetic structure was evident, but on a scale larger than our study area. Lizards were sexually dimorphic, whereby females had longer snout-vent length than males, providing support for the fecundity selection hypothesis. Body size variation in M. boulengeri was correlated with temperature and rainfall, a pattern consistent with larger individuals occupying cooler and more productive parts of the landscape. Climate change forecasts, which predict warmer temperature and increased aridity, may result in reduced lizard biomass and decoupling of trophic interactions with potential implications for community organization and ecosystem function.

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Maximum-likelihood phylogenetic tree.The tree represents 30 unique Morethia boulengeri haplotypes from 471 bp of mitochondrial DNA ND2 gene sequence, using M. adelaidensis (a closely-related species) as the outgroup. Sequences are coded according to major branches of the tree and their sampling locations are shown on the associated map. Sample names refer to the Australian Biological Tissue Collection numbers and unlabelled samples are those collected in this study (indicated by rectangle on map). Bootstrap values are shown on the figure and branches with less than 50% bootstrap support were collapsed.
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pone-0109830-g002: Maximum-likelihood phylogenetic tree.The tree represents 30 unique Morethia boulengeri haplotypes from 471 bp of mitochondrial DNA ND2 gene sequence, using M. adelaidensis (a closely-related species) as the outgroup. Sequences are coded according to major branches of the tree and their sampling locations are shown on the associated map. Sample names refer to the Australian Biological Tissue Collection numbers and unlabelled samples are those collected in this study (indicated by rectangle on map). Bootstrap values are shown on the figure and branches with less than 50% bootstrap support were collapsed.

Mentions: We sequenced a 546 base pair fragment of the mitochondrial ND2 gene from 75 M. boulengeri sampled in this study (with at least one sample from each farm our sample size was adequate), nine M. boulengeri from other locations throughout the species' distribution in eastern Australia (from the Australian Biological Tissue Collection - see Figure 2 for collection numbers) and one Samphire Skink (M. adelaidensis), a closely-related species. We selected this gene because it is a common marker used to detect shallow phylogenetic structure [44]. We chose not to use faster evolving markers such as microsatellites as we were interested in testing for unrecognized species and not patterns of genetic differentiation caused by movement across the landscape. We extracted DNA according to the protocol of [44] and sequenced the samples as described in [45]. We edited and aligned the sequences using the program Geneious [46] and calculated haplotype diversity measures and a matrix of nucleotide differences between individuals in DnaSP [47]. We constructed a maximum likelihood phylogenetic tree with the PhyML program implemented in the Phylogeny.fr platform [48] using the HKY+G (gamma  = 0.327) substitution model, as selected according to AICc in (imodeltest) [49]. We performed a Mantel test in the R package Ecodist [50] to examine the correlation between the nucleotide difference matrix and Euclidean geographic distances.


Geographical variation in body size and sexual size dimorphism in an Australian lizard, Boulenger's Skink (Morethia boulengeri).

Michael DR, Banks SC, Piggott MP, Cunningham RB, Crane M, MacGregor C, McBurney L, Lindenmayer DB - PLoS ONE (2014)

Maximum-likelihood phylogenetic tree.The tree represents 30 unique Morethia boulengeri haplotypes from 471 bp of mitochondrial DNA ND2 gene sequence, using M. adelaidensis (a closely-related species) as the outgroup. Sequences are coded according to major branches of the tree and their sampling locations are shown on the associated map. Sample names refer to the Australian Biological Tissue Collection numbers and unlabelled samples are those collected in this study (indicated by rectangle on map). Bootstrap values are shown on the figure and branches with less than 50% bootstrap support were collapsed.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4206273&req=5

pone-0109830-g002: Maximum-likelihood phylogenetic tree.The tree represents 30 unique Morethia boulengeri haplotypes from 471 bp of mitochondrial DNA ND2 gene sequence, using M. adelaidensis (a closely-related species) as the outgroup. Sequences are coded according to major branches of the tree and their sampling locations are shown on the associated map. Sample names refer to the Australian Biological Tissue Collection numbers and unlabelled samples are those collected in this study (indicated by rectangle on map). Bootstrap values are shown on the figure and branches with less than 50% bootstrap support were collapsed.
Mentions: We sequenced a 546 base pair fragment of the mitochondrial ND2 gene from 75 M. boulengeri sampled in this study (with at least one sample from each farm our sample size was adequate), nine M. boulengeri from other locations throughout the species' distribution in eastern Australia (from the Australian Biological Tissue Collection - see Figure 2 for collection numbers) and one Samphire Skink (M. adelaidensis), a closely-related species. We selected this gene because it is a common marker used to detect shallow phylogenetic structure [44]. We chose not to use faster evolving markers such as microsatellites as we were interested in testing for unrecognized species and not patterns of genetic differentiation caused by movement across the landscape. We extracted DNA according to the protocol of [44] and sequenced the samples as described in [45]. We edited and aligned the sequences using the program Geneious [46] and calculated haplotype diversity measures and a matrix of nucleotide differences between individuals in DnaSP [47]. We constructed a maximum likelihood phylogenetic tree with the PhyML program implemented in the Phylogeny.fr platform [48] using the HKY+G (gamma  = 0.327) substitution model, as selected according to AICc in (imodeltest) [49]. We performed a Mantel test in the R package Ecodist [50] to examine the correlation between the nucleotide difference matrix and Euclidean geographic distances.

Bottom Line: Lizards were sexually dimorphic, whereby females had longer snout-vent length than males, providing support for the fecundity selection hypothesis.Body size variation in M. boulengeri was correlated with temperature and rainfall, a pattern consistent with larger individuals occupying cooler and more productive parts of the landscape.Climate change forecasts, which predict warmer temperature and increased aridity, may result in reduced lizard biomass and decoupling of trophic interactions with potential implications for community organization and ecosystem function.

View Article: PubMed Central - PubMed

Affiliation: Fenner School of Environment and Society, ARC Centre of Excellence for Environmental Decisions, and National Environment Research Program, The Australian National University, Canberra, Australia.

ABSTRACT
Ecogeographical rules help explain spatial and temporal patterns in intraspecific body size. However, many of these rules, when applied to ectothermic organisms such as reptiles, are controversial and require further investigation. To explore factors that influence body size in reptiles, we performed a heuristic study to examine body size variation in an Australian lizard, Boulenger's Skink Morethia boulengeri from agricultural landscapes in southern New South Wales, south-eastern Australia. We collected tissue and morphological data on 337 adult lizards across a broad elevation and climate gradient. We used a model-selection procedure to determine if environmental or ecological variables best explained body size variation. We explored the relationship between morphology and phylogenetic structure before modeling candidate variables from four broad domains: (1) geography (latitude, longitude and elevation), (2) climate (temperature and rainfall), (3) habitat (vegetation type, number of logs and ground cover attributes), and (4) management (land use and grazing history). Broad phylogenetic structure was evident, but on a scale larger than our study area. Lizards were sexually dimorphic, whereby females had longer snout-vent length than males, providing support for the fecundity selection hypothesis. Body size variation in M. boulengeri was correlated with temperature and rainfall, a pattern consistent with larger individuals occupying cooler and more productive parts of the landscape. Climate change forecasts, which predict warmer temperature and increased aridity, may result in reduced lizard biomass and decoupling of trophic interactions with potential implications for community organization and ecosystem function.

Show MeSH
Related in: MedlinePlus