Tags

Type your tag names separated by a space and hit enter

Seasonal and geographical variation in heat tolerance and evaporative cooling capacity in a passerine bird.
J Exp Biol. 2016 Mar; 219(Pt 6):859-69.JE

Abstract

Intraspecific variation in avian thermoregulatory responses to heat stress has received little attention, despite increasing evidence that endothermic animals show considerable physiological variation among populations. We investigated seasonal (summer versus winter) variation in heat tolerance and evaporative cooling in an Afrotropical ploceid passerine, the white-browed sparrow-weaver (Plocepasser mahali; ∼ 47 g) at three sites along a climatic gradient with more than 10 °C variation in mid-summer maximum air temperature (Ta). We measured resting metabolic rate (RMR) and total evaporative water loss (TEWL) using open flow-through respirometry, and core body temperature (Tb) using passive integrated transponder tags. Sparrow-weavers were exposed to a ramped profile of progressively higher Ta between 30 and 52 °C to elicit maximum evaporative cooling capacity (N=10 per site per season); the maximum Ta birds tolerated before the onset of severe hyperthermia (Tb ≈ 44 °C) was considered to be their hyperthermia threshold Ta (Ta,HT). Our data reveal significant seasonal acclimatisation of heat tolerance, with a desert population of sparrow-weavers reaching significantly higher Ta in summer (49.5 ± 1.4 °C, i.e. higher Ta,HT) than in winter (46.8 ± 0.9 °C), reflecting enhanced evaporative cooling during summer. Moreover, desert sparrow-weavers had significantly higher heat tolerance and evaporative cooling capacity during summer compared with populations from more mesic sites (Ta,HT=47.3 ± 1.5 and 47.6 ± 1.3 °C). A better understanding of the contributions of local adaptation versus phenotypic plasticity to intraspecific variation in avian heat tolerance and evaporative cooling capacity is needed for modelling species' responses to changing climates.

Authors+Show Affiliations

DST-NRF Centre of Excellence at the Percy FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa.UNM Biology Department, University of New Mexico, MSC03-2020, Albuquerque, NM 87131-0001, USA.DST-NRF Centre of Excellence at the Percy FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa aemckechnie@zoology.up.ac.za.

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

Language

eng

PubMed ID

26787477

Citation

Noakes, Matthew J., et al. "Seasonal and Geographical Variation in Heat Tolerance and Evaporative Cooling Capacity in a Passerine Bird." The Journal of Experimental Biology, vol. 219, no. Pt 6, 2016, pp. 859-69.
Noakes MJ, Wolf BO, McKechnie AE. Seasonal and geographical variation in heat tolerance and evaporative cooling capacity in a passerine bird. J Exp Biol. 2016;219(Pt 6):859-69.
Noakes, M. J., Wolf, B. O., & McKechnie, A. E. (2016). Seasonal and geographical variation in heat tolerance and evaporative cooling capacity in a passerine bird. The Journal of Experimental Biology, 219(Pt 6), 859-69. https://doi.org/10.1242/jeb.132001
Noakes MJ, Wolf BO, McKechnie AE. Seasonal and Geographical Variation in Heat Tolerance and Evaporative Cooling Capacity in a Passerine Bird. J Exp Biol. 2016;219(Pt 6):859-69. PubMed PMID: 26787477.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Seasonal and geographical variation in heat tolerance and evaporative cooling capacity in a passerine bird. AU - Noakes,Matthew J, AU - Wolf,Blair O, AU - McKechnie,Andrew E, Y1 - 2016/01/19/ PY - 2015/09/09/received PY - 2016/01/08/accepted PY - 2016/1/21/entrez PY - 2016/1/21/pubmed PY - 2017/4/5/medline KW - Acclimatisation KW - Arid-zone birds KW - Evaporative water loss KW - Heat stress KW - Hyperthermia SP - 859 EP - 69 JF - The Journal of experimental biology JO - J. Exp. Biol. VL - 219 IS - Pt 6 N2 - Intraspecific variation in avian thermoregulatory responses to heat stress has received little attention, despite increasing evidence that endothermic animals show considerable physiological variation among populations. We investigated seasonal (summer versus winter) variation in heat tolerance and evaporative cooling in an Afrotropical ploceid passerine, the white-browed sparrow-weaver (Plocepasser mahali; ∼ 47 g) at three sites along a climatic gradient with more than 10 °C variation in mid-summer maximum air temperature (Ta). We measured resting metabolic rate (RMR) and total evaporative water loss (TEWL) using open flow-through respirometry, and core body temperature (Tb) using passive integrated transponder tags. Sparrow-weavers were exposed to a ramped profile of progressively higher Ta between 30 and 52 °C to elicit maximum evaporative cooling capacity (N=10 per site per season); the maximum Ta birds tolerated before the onset of severe hyperthermia (Tb ≈ 44 °C) was considered to be their hyperthermia threshold Ta (Ta,HT). Our data reveal significant seasonal acclimatisation of heat tolerance, with a desert population of sparrow-weavers reaching significantly higher Ta in summer (49.5 ± 1.4 °C, i.e. higher Ta,HT) than in winter (46.8 ± 0.9 °C), reflecting enhanced evaporative cooling during summer. Moreover, desert sparrow-weavers had significantly higher heat tolerance and evaporative cooling capacity during summer compared with populations from more mesic sites (Ta,HT=47.3 ± 1.5 and 47.6 ± 1.3 °C). A better understanding of the contributions of local adaptation versus phenotypic plasticity to intraspecific variation in avian heat tolerance and evaporative cooling capacity is needed for modelling species' responses to changing climates. SN - 1477-9145 UR - https://www.unboundmedicine.com/medline/citation/26787477/Seasonal_and_geographical_variation_in_heat_tolerance_and_evaporative_cooling_capacity_in_a_passerine_bird_ L2 - http://jeb.biologists.org/cgi/pmidlookup?view=long&pmid=26787477 DB - PRIME DP - Unbound Medicine ER -