Bergmann meets Scholander: geographical variation in body size and insulation in the koala is related to climate

Briscoe, Natalie J.; Krockenberger, Andrew K.; Handasyde, Kathrine A.; Kearney, Michael R.

doi:10.1111/jbi.12445

Cited by 39 publications

(43 citation statements)

References 56 publications

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“…The four shallow genetic lineages identified here do not correspond to previously described sub-species, and it is now apparent that morphological variation within the koala represents a cline reflecting gradients in environmental conditions across the distribution [12,16]. In a previous phylogeographic study, Houlden et al [18] found a similar pattern of genetic divergence, noting the presence of ‘three clusters’ in their phylogenetic analyses, which correspond to three of the four identified in the present study.…”

Section: Discussionmentioning

confidence: 89%

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Phylogeography of the Koala, (Phascolarctos cinereus), and Harmonising Data to Inform Conservation

et al. 2016

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The Australian continent exhibits complex biogeographic patterns but studies of the impacts of Pleistocene climatic oscillation on the mesic environments of the Southern Hemisphere are limited. The koala (Phascolarctos cinereus), one of Australia’s most iconic species, was historically widely distributed throughout much of eastern Australia but currently represents a complex conservation challenge. To better understand the challenges to koala genetic health, we assessed the phylogeographic history of the koala. Variation in the maternally inherited mitochondrial DNA (mtDNA) Control Region (CR) was examined in 662 koalas sampled throughout their distribution. In addition, koala CR haplotypes accessioned to Genbank were evaluated and consolidated. A total of 53 unique CR haplotypes have been isolated from koalas to date (including 15 haplotypes novel to this study). The relationships among koala CR haplotypes were indicative of a single Evolutionary Significant Unit and do not support the recognition of subspecies, but were separated into four weakly differentiated lineages which correspond to three geographic clusters: a central lineage, a southern lineage and two northern lineages co-occurring north of Brisbane. The three geographic clusters were separated by known Pleistocene biogeographic barriers: the Brisbane River Valley and Clarence River Valley, although there was evidence of mixing amongst clusters. While there is evidence for historical connectivity, current koala populations exhibit greater structure, suggesting habitat fragmentation may have restricted female-mediated gene flow. Since mtDNA data informs conservation planning, we provide a summary of existing CR haplotypes, standardise nomenclature and make recommendations for future studies to harmonise existing datasets. This holistic approach is critical to ensuring management is effective and small scale local population studies can be integrated into a wider species context.

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Section: Discussionmentioning

confidence: 89%

“…size and colouration; [12,14–16]). Initially, three koala subspecies were recognised on the basis of variation in size and colouration: P .…”

Section: Introductionmentioning

confidence: 99%

Phylogeography of the Koala, (Phascolarctos cinereus), and Harmonising Data to Inform Conservation

et al. 2016

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“…In both birds and mammals, adaptive body size-independent changes to BMR and thermal conductance, in combination with additional behavioral and physiological traits, allow species to occur in a wide range of thermal environments. Although we focus on interspecific comparisons, similar physiological and morphological changes likely play a role in within-species adaptation to local environments (25).…”

Section: Discussionmentioning

confidence: 99%

Metabolic heat production and thermal conductance are mass-independent adaptations to thermal environment in birds and mammals

Fristoe

Burger

Balk

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

123

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The extent to which different kinds of organisms have adapted to environmental temperature regimes is central to understanding how they respond to climate change. The Scholander-Irving (S-I) model of heat transfer lays the foundation for explaining how endothermic birds and mammals maintain their high, relatively constant body temperatures in the face of wide variation in environmental temperature. The S-I model shows how body temperature is regulated by balancing the rates of heat production and heat loss. Both rates scale with body size, suggesting that larger animals should be better adapted to cold environments than smaller animals, and vice versa. However, the global distributions of ∼9,000 species of terrestrial birds and mammals show that the entire range of body sizes occurs in nearly all climatic regimes. Using physiological and environmental temperature data for 211 bird and 178 mammal species, we test for mass-independent adaptive changes in two key parameters of the S-I model: basal metabolic rate (BMR) and thermal conductance. We derive an axis of thermal adaptation that is independent of body size, extends the S-I model, and highlights interactions among physiological and morphological traits that allow endotherms to persist in a wide range of temperatures. Our macrophysiological and macroecological analyses support our predictions that shifts in BMR and thermal conductance confer important adaptations to environmental temperature in both birds and mammals.macrophysiology | Bergmann's rule | body size | metabolic rate | thermal conductance A fundamental problem in ecology and biogeography is to elucidate the physiological processes that determine the environmental tolerances and influence the distributions of species. Across their nearly worldwide distributions, endothermic birds and mammals maintain near-constant body temperatures in the face of extreme and fluctuating environmental temperatures. Elucidating the morphological and physiological adaptations that allow species to inhabit such a wide spectrum of thermal environments is important for understanding the distribution of biodiversity and for predicting responses of species to climate change (1, 2).In a seminal paper, Scholander et al. (3) showed how endotherms balance rates of heat production and heat loss so as to maintain a constant body temperature in the face of varying environmental temperatures. The essence of the Scholander-Irving (S-I) model is the equation:where T b is body temperature, T a is ambient temperature, B is the rate of metabolic heat production, and C is the rate of heat loss or thermal conductance (4). For a resting animal, which has minimized heat loss by maximizing insulation and optimizing body posture, C = minimum thermal conductance (C MIN ); B = basal metabolic rate (BMR); and T a = T lc , where T lc is the lower critical temperature or the lower limit of the thermal neutral zone (TNZ).The TNZ is ecologically important because it is the range of environmental temperatures where energy expenditure is minimal; out...

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“…Birds use a suite of behaviours and physiological mechanisms to control heat exchange and thus reduce the energy required for thermoregulation. This can include use of micro refugia, postural changes including ptiloerection of feathers, and modification of peripheral blood flow [29,30,48,52,55,56,63,64]. Such strategies are used in both winter and summer and can be effective at maintaining body mass in the face of challenging conditions [65].…”

Section: Differences Between the Speciesmentioning

confidence: 99%

“…In cool climates, winter rainfall can reduce the insulation capacity of fur and feathers, thereby increasing heat loss and leading to reductions in body condition [27][28][29]. Winter rain may also indirectly increase the costs of thermoregulation by negatively affecting the availability of food [27].…”

Section: Introductionmentioning

confidence: 99%

Associations between changing climate and body condition over decades in two southern hemisphere passerine birds

Gardner

Rowley

Rebeira³

et al. 2018

Clim Chang Responses

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Background: Climate change presents considerable challenges for endotherms because they must maintain high, relatively constant body temperatures across a range of environmental conditions to ensure survival and optimise performance. Individuals exposed to changing weather must manage energy and water allocation to maintain thermal homeostasis, with consequences for body condition, and hence there is potential for selection because body condition is strongly linked to fitness. Understanding how weather drives changes in body condition is therefore fundamental to understanding how fitness is affected by climate change. Here we test for associations between weather and body condition and how this changes over time, in two co-existing species of small insectivorous passerines, the red-winged fairy-wren, Malurus elegans and white-browed scrubwren, Sericornis frontalis, that have been the subject of a ringing study for 39 years in temperate south-western Australia. The study populations have experienced increases in minimum temperatures in winter and summer as well as decreases in the frequencies of days with thermal minima < 5°C, but the summer climate remains relatively mild with few days experiencing thermal maxima > 35°C. Although, warming temperatures may reduce thermoregulatory costs, repeated exposure to hot conditions has been shown to have negative effects on body condition. Thus, we predict that the reduction over time in daily minima < 5°C, along with the influence of increased maximum and minimum temperatures in summer and winter, will have positive effects on body condition. Results: In accordance with thermoregulatory predictions, colder daily minima in the range 1-19°C prior to capture were associated with reduced body condition in winter in both species. Furthermore, in summer, in fairy-wrens but not scrubwrens, warmer daily maxima were associated with increasing body condition, and repeated exposure to temperatures > 30°C over consecutive days was negatively associated with body condition. Body condition increased over the 39 years of the study for fairy-wrens but there was no change in scrubwrens, which is consistent with observed within-season associations between body condition and weather, and the change in climate over time.

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Bergmann meets Scholander: geographical variation in body size and insulation in the koala is related to climate

Cited by 39 publications

References 56 publications

Phylogeography of the Koala, (Phascolarctos cinereus), and Harmonising Data to Inform Conservation

Phylogeography of the Koala, (Phascolarctos cinereus), and Harmonising Data to Inform Conservation

Metabolic heat production and thermal conductance are mass-independent adaptations to thermal environment in birds and mammals

Associations between changing climate and body condition over decades in two southern hemisphere passerine birds

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