Adapting to the unpredictable: reproductive biology of vertebrates in the Australian wet–dry tropics

Shine, Richard; Brown, Gregory P.

doi:10.1098/rstb.2007.2144

Cited by 145 publications

(130 citation statements)

References 74 publications

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“…For example, Lank et al (2003) suggest that the timing of autumn migration in sandpipers is influenced by the need to travel south before the southerly migration of peregrine falcons. Even in the tropics, where day length is constant (and temperature may be reasonably constant), there may be strong seasonal changes (Komdeur & Daan 2005, Shine & Brown 2008.…”

Section: Introductionmentioning

confidence: 99%

Optimal annual routines: behaviour in the context of physiology and ecology

McNamara

Houston

2007

Phil. Trans. R. Soc. B

177

149

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Organisms in a seasonal environment often schedule activities in a regular way over the year. If we assume that such annual routines have been shaped by natural selection then life-history theory should provide a basis for explaining them. We argue that many life-history trade-offs are mediated by underlying physiological variables that act on various time scales. The dynamics of these variables often preclude considering one period of the year in isolation. In order to capture the essence of annual routines, and many life-history traits, a detailed model of changes in physiological state over the annual cycle is required. We outline a modelling approach based on suitable physiological and ecological state variables that can capture this underlying biology, and describe how models based on this approach can be used to generate a range of insights and predictions.

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Section: Introductionmentioning

confidence: 99%

Optimal annual routines: behaviour in the context of physiology and ecology

McNamara

Houston

2007

Phil. Trans. R. Soc. B

177

149

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“…Breeding activity is often related to temporal variation in precipitation, especially in tropical organisms (van Schaik et al 1993;Shine and Brown 2008). Because precipitation is strongly related to food availability (Ahumada 2001;Wright and Calderó n 2006), tropical animals are expected to adjust their reproductive timing to match local precipitation patterns (Hau et al 2008;Shine and Brown 2008;Martin et al 2009;Jahn et al 2010), which may be variable even over small spatial scales (Legates and Willmott 1990).…”

Section: Introductionmentioning

confidence: 99%

Asynchrony of Seasons: Genetic Differentiation Associated with Geographic Variation in Climatic Seasonality and Reproductive Phenology

Quintero

González‐Caro

Zalamea

et al. 2014

The American Naturalist

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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. abstract: Many organisms exhibit distinct breeding seasons tracking food availability. If conspecific populations inhabit areas that experience different temporal cycles in food availability spurred by variation in precipitation regimes, then they should display asynchronous breeding seasons. Thus, such populations might exhibit a temporal barrier to gene flow, which may potentially promote genetic differentiation. We test a central prediction of this hypothesis, namely, that individuals living in areas with more asynchronous precipitation regimes should be more genetically differentiated than individuals living in areas with more similar precipitation regimes. Using mitochondrial DNA sequences, climatic data, and geographical/ecological distances between individuals of 57 New World bird species mostly from the tropics, we examined the effect of asynchronous precipitation (a proxy for asynchronous resource availability) on genetic differentiation. We found evidence for a positive and significant cross-species effect of precipitation asynchrony on genetic distance after accounting for geographical/ecological distances, suggesting that current climatic conditions may play a role in population differentiation. Spatial asynchrony in climate may thus drive evolutionary divergence in the absence of overt geographic barriers to gene flow; this mechanism contrasts with those invoked by most models of biotic diversification emphasizing physical or ecological changes to the landscape as drivers of divergence.

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“…a severe rainfall is indicative of the coming rainy season or just a random rainfall during a prolonged dry season (cf. Shine & Brown 2008). These benefits also apply to animals that need to anticipate environmental conditions they cannot directly assess, e.g.…”

mentioning

confidence: 99%

Avian circannual clocks: adaptive significance and possible involvement of energy turnover in their proximate control

Wikelski

Martin

Scheuerlein

et al. 2007

Phil. Trans. R. Soc. B

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Endogenous circannual clocks are found in many long-lived organisms, but are best studied in mammal and bird species. Circannual clocks are synchronized with the environment by changes in photoperiod, light intensity and possibly temperature and seasonal rainfall patterns. Annual timing mechanisms are presumed to have important ultimate functions in seasonally regulating reproduction, moult, hibernation, migration, body weight and fat deposition/stores. Birds that live in habitats where environmental cues such as photoperiod are poor predictors of seasons (e.g. equatorial residents, migrants to equatorial/tropical latitudes) rely more on their endogenous clocks than birds living in environments that show a tight correlation between photoperiod and seasonal events. Such population-specific/interspecific variation in reliance on endogenous clocks may indicate that annual timing mechanisms are adaptive. However, despite the apparent adaptive importance of circannual clocks, (i) what specific adaptive value they have in the wild and (ii) how they function are still largely untested. Whereas circadian clocks are hypothesized to be generated by molecular feedback loops, it has been suggested that circannual clocks are either based upon (i) a de-multiplication ('counting') of circadian days, (ii) a sequence of interdependent physiological states, or (iii) one or more endogenous oscillators, similar to circadian rhythms. We tested the de-multiplication of days (i) versus endogenous regulation hypotheses (ii) and (iii) in captive male and female house sparrows (Passer domesticus). We assessed the period of reproductive (testicular and follicular) cycles in four groups of birds kept either under photoperiods of LD 12 L : 12 D (period length: 24 h), 13.5 L : 13.5 D (27 h), 10.5 L : 10.5 D (23 h) or 12 D : 8 L : 3 D : 1 L (24-h skeleton photoperiod), respectively, for 15 months. Contrary to predictions from the de-multiplication hypothesis, individuals experiencing 27-h days did not differ (i.e. did not have longer) annual reproductive rhythms than individuals from the 21-or 24-h day groups. However, in line with predictions from endogenous regulation, birds in the skeleton group had significantly longer circannual period lengths than all other groups. Birds exposed to skeleton photoperiods experienced fewer light hours per year than all other groups (3285 versus 4380) and had a lower daily energy expenditure, as tested during one point of the annual cycle using respirometry. Although our results are tantalizing, they are still preliminary as birds were only studied over a period of 15 months. Nevertheless, the present data fail to support a 'counting of circadian days' and instead support hypotheses proposing whole-organism processes as the mechanistic basis for circannual rhythms. We propose a novel energy turnover hypothesis which predicts a dependence of the speed of the circannual clock on the overall energy expenditure of an organism.

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Adapting to the unpredictable: reproductive biology of vertebrates in the Australian wet–dry tropics

Cited by 145 publications

References 74 publications

Optimal annual routines: behaviour in the context of physiology and ecology

Optimal annual routines: behaviour in the context of physiology and ecology

Asynchrony of Seasons: Genetic Differentiation Associated with Geographic Variation in Climatic Seasonality and Reproductive Phenology

Avian circannual clocks: adaptive significance and possible involvement of energy turnover in their proximate control

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