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Temperature and aridity determine body size conformity to Bergmann’s rule independent of latitudinal differences in a tropical environment

Research output: Contribution to journalArticle

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Temperature and aridity determine body size conformity to Bergmann’s rule independent of latitudinal differences in a tropical environment. / Nwaogu, Chima Josiah; Tieleman, B. Irene; Bitrus, Kwanye; Cresswell, William Richard Lawrence.

In: Journal of Ornithology, Vol. 159, No. 4, 10.2018, p. 1053–1062 .

Research output: Contribution to journalArticle

Harvard

Nwaogu, CJ, Tieleman, BI, Bitrus, K & Cresswell, WRL 2018, 'Temperature and aridity determine body size conformity to Bergmann’s rule independent of latitudinal differences in a tropical environment' Journal of Ornithology, vol. 159, no. 4, pp. 1053–1062 . https://doi.org/10.1007/s10336-018-1574-8

APA

Nwaogu, C. J., Tieleman, B. I., Bitrus, K., & Cresswell, W. R. L. (2018). Temperature and aridity determine body size conformity to Bergmann’s rule independent of latitudinal differences in a tropical environment. Journal of Ornithology, 159(4), 1053–1062 . https://doi.org/10.1007/s10336-018-1574-8

Vancouver

Nwaogu CJ, Tieleman BI, Bitrus K, Cresswell WRL. Temperature and aridity determine body size conformity to Bergmann’s rule independent of latitudinal differences in a tropical environment. Journal of Ornithology. 2018 Oct;159(4):1053–1062 . https://doi.org/10.1007/s10336-018-1574-8

Author

Nwaogu, Chima Josiah ; Tieleman, B. Irene ; Bitrus, Kwanye ; Cresswell, William Richard Lawrence. / Temperature and aridity determine body size conformity to Bergmann’s rule independent of latitudinal differences in a tropical environment. In: Journal of Ornithology. 2018 ; Vol. 159, No. 4. pp. 1053–1062 .

Bibtex - Download

@article{3fbbf4b6673a4326b3728b75189c5ab3,
title = "Temperature and aridity determine body size conformity to Bergmann’s rule independent of latitudinal differences in a tropical environment",
abstract = "Bergmann’s rule, defined as the tendency for endotherms to be larger in colder environments, is a biophysical generalization of body size variation that is frequently tested along latitudinal gradients, even though latitude is only a proxy for temperature variation. We test whether variation in temperature and aridity determine avian body size conformity to Bergmann’s rule independent of latitude differences, using the ubiquitous Common Bulbul Pycnonotus barbatus, along a West African environmental gradient. We trapped 538 birds in 22 locations between latitudes 6 and 13°N in Nigeria, and estimated average body surface area to mass ratio per location. We then modelled body surface to mass ratio using general linear models, with latitude, altitude and one of 19 bioclimatic variables extracted from http://www.worldclim.org/bioclim as predictors. We sequentially dropped latitude and altitude from each model to obtain the R2 of the resultant models. Finally, we compared the R2 of univariate models, where bioclimatic variables predicted body surface area to mass ratio significantly (14 out of 19), to multivariate models including latitude, altitude and a bioclimatic variable, using the Wilcoxon matched pairs test. We found that multivariate models did not perform better than univariate models with only bioclimatic variables. Six temperature and eight precipitation variables significantly predicted variation in body surface area to mass ratio between locations; in fact, 50{\%} (seven out of 14) of these better explained variation in body surface area to mass ratio than the multivariate models. Birds showed a larger body surface area relative to body mass ratio in hotter environments independent of latitude or altitude, which conforms to Bergmann’s rule. Yet, a combination of morphometric analyses and controlled temperature-exposure experiments is required to prove the proposed relationship between relative body surface area and thermoregulation in endotherms.",
keywords = "Latitude, Thermoregulation, Global warming, Birds, Temperature variation, Bioclimatic variable",
author = "Nwaogu, {Chima Josiah} and Tieleman, {B. Irene} and Kwanye Bitrus and Cresswell, {William Richard Lawrence}",
note = "C.J.N. was supported by a studentship funded by the Leventis Conservation Foundation through the University of St. Andrews, UK.",
year = "2018",
month = "10",
doi = "10.1007/s10336-018-1574-8",
language = "English",
volume = "159",
pages = "1053–1062",
journal = "Journal of Ornithology",
issn = "2193-7192",
publisher = "Springer Nature",
number = "4",

}

RIS (suitable for import to EndNote) - Download

TY - JOUR

T1 - Temperature and aridity determine body size conformity to Bergmann’s rule independent of latitudinal differences in a tropical environment

AU - Nwaogu, Chima Josiah

AU - Tieleman, B. Irene

AU - Bitrus, Kwanye

AU - Cresswell, William Richard Lawrence

N1 - C.J.N. was supported by a studentship funded by the Leventis Conservation Foundation through the University of St. Andrews, UK.

PY - 2018/10

Y1 - 2018/10

N2 - Bergmann’s rule, defined as the tendency for endotherms to be larger in colder environments, is a biophysical generalization of body size variation that is frequently tested along latitudinal gradients, even though latitude is only a proxy for temperature variation. We test whether variation in temperature and aridity determine avian body size conformity to Bergmann’s rule independent of latitude differences, using the ubiquitous Common Bulbul Pycnonotus barbatus, along a West African environmental gradient. We trapped 538 birds in 22 locations between latitudes 6 and 13°N in Nigeria, and estimated average body surface area to mass ratio per location. We then modelled body surface to mass ratio using general linear models, with latitude, altitude and one of 19 bioclimatic variables extracted from http://www.worldclim.org/bioclim as predictors. We sequentially dropped latitude and altitude from each model to obtain the R2 of the resultant models. Finally, we compared the R2 of univariate models, where bioclimatic variables predicted body surface area to mass ratio significantly (14 out of 19), to multivariate models including latitude, altitude and a bioclimatic variable, using the Wilcoxon matched pairs test. We found that multivariate models did not perform better than univariate models with only bioclimatic variables. Six temperature and eight precipitation variables significantly predicted variation in body surface area to mass ratio between locations; in fact, 50% (seven out of 14) of these better explained variation in body surface area to mass ratio than the multivariate models. Birds showed a larger body surface area relative to body mass ratio in hotter environments independent of latitude or altitude, which conforms to Bergmann’s rule. Yet, a combination of morphometric analyses and controlled temperature-exposure experiments is required to prove the proposed relationship between relative body surface area and thermoregulation in endotherms.

AB - Bergmann’s rule, defined as the tendency for endotherms to be larger in colder environments, is a biophysical generalization of body size variation that is frequently tested along latitudinal gradients, even though latitude is only a proxy for temperature variation. We test whether variation in temperature and aridity determine avian body size conformity to Bergmann’s rule independent of latitude differences, using the ubiquitous Common Bulbul Pycnonotus barbatus, along a West African environmental gradient. We trapped 538 birds in 22 locations between latitudes 6 and 13°N in Nigeria, and estimated average body surface area to mass ratio per location. We then modelled body surface to mass ratio using general linear models, with latitude, altitude and one of 19 bioclimatic variables extracted from http://www.worldclim.org/bioclim as predictors. We sequentially dropped latitude and altitude from each model to obtain the R2 of the resultant models. Finally, we compared the R2 of univariate models, where bioclimatic variables predicted body surface area to mass ratio significantly (14 out of 19), to multivariate models including latitude, altitude and a bioclimatic variable, using the Wilcoxon matched pairs test. We found that multivariate models did not perform better than univariate models with only bioclimatic variables. Six temperature and eight precipitation variables significantly predicted variation in body surface area to mass ratio between locations; in fact, 50% (seven out of 14) of these better explained variation in body surface area to mass ratio than the multivariate models. Birds showed a larger body surface area relative to body mass ratio in hotter environments independent of latitude or altitude, which conforms to Bergmann’s rule. Yet, a combination of morphometric analyses and controlled temperature-exposure experiments is required to prove the proposed relationship between relative body surface area and thermoregulation in endotherms.

KW - Latitude

KW - Thermoregulation

KW - Global warming

KW - Birds

KW - Temperature variation

KW - Bioclimatic variable

U2 - 10.1007/s10336-018-1574-8

DO - 10.1007/s10336-018-1574-8

M3 - Article

VL - 159

SP - 1053

EP - 1062

JO - Journal of Ornithology

T2 - Journal of Ornithology

JF - Journal of Ornithology

SN - 2193-7192

IS - 4

ER -

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ID: 253199123