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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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Regression analysis of Morethia boulengeri and candidate variables.The relationships show a positive association with snout-vent length (SVL) and: (a) temperature, (b) rainfall (c) percent bare ground cover, and (d) density of mature trees >50 cm diameter.
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pone-0109830-g004: Regression analysis of Morethia boulengeri and candidate variables.The relationships show a positive association with snout-vent length (SVL) and: (a) temperature, (b) rainfall (c) percent bare ground cover, and (d) density of mature trees >50 cm diameter.

Mentions: We found no significant relationship between male or female SVL and any of the geographical variables (e.g. bioregion, latitude or elevation). In contrast, all of the climate variables were important in explaining male and female SVL variation. However, these variables were highly correlated, so we selected mean maximum summer temperature (P<0.001; Figure 4a) and mean rainfall in 2008 (P<0.001; Figure 4b) based on their significance levels to use in the final model. Our habitat models included percent cover of bare ground (P = 0.003; Figure 4c) and the density of mature trees (P = 0.01; Figure 4d). Furthermore, we found a significant interaction between sex and the density of mature trees (P = 0.002), whereby female SVL increased relative to the density of mature trees. In relation to management models, we found no significant relationship with SVL and any of the candidate variables from this domain. In the final model, both climate variables remained significant, whereby SVL increased relative to decreasing temperature and increasing rainfall. However, in the presence of the climate variables, bare ground and large trees were no longer significant.


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)

Regression analysis of Morethia boulengeri and candidate variables.The relationships show a positive association with snout-vent length (SVL) and: (a) temperature, (b) rainfall (c) percent bare ground cover, and (d) density of mature trees >50 cm diameter.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0109830-g004: Regression analysis of Morethia boulengeri and candidate variables.The relationships show a positive association with snout-vent length (SVL) and: (a) temperature, (b) rainfall (c) percent bare ground cover, and (d) density of mature trees >50 cm diameter.
Mentions: We found no significant relationship between male or female SVL and any of the geographical variables (e.g. bioregion, latitude or elevation). In contrast, all of the climate variables were important in explaining male and female SVL variation. However, these variables were highly correlated, so we selected mean maximum summer temperature (P<0.001; Figure 4a) and mean rainfall in 2008 (P<0.001; Figure 4b) based on their significance levels to use in the final model. Our habitat models included percent cover of bare ground (P = 0.003; Figure 4c) and the density of mature trees (P = 0.01; Figure 4d). Furthermore, we found a significant interaction between sex and the density of mature trees (P = 0.002), whereby female SVL increased relative to the density of mature trees. In relation to management models, we found no significant relationship with SVL and any of the candidate variables from this domain. In the final model, both climate variables remained significant, whereby SVL increased relative to decreasing temperature and increasing rainfall. However, in the presence of the climate variables, bare ground and large trees were no longer significant.

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