Selection on body size in a raptor with pronounced reversed sexual size dimorphism: are bigger females better?

McDonald, Paul G.; Olsen, Penny; Cockburn, Andrew

doi:10.1093/beheco/arh118

Cited by 34 publications

(52 citation statements)

References 49 publications

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“…Such complexity underlines the diYculty of capturing individual quality by means of a single univariate measure. This diYculty was further emphasised by the fact that morphometric measures of individual quality, such as size and mass residuals, had opposite eVects on the productivity of males and females, which may be common in raptorial species (Massemin et al 2000;McDonald et al 2005;Sergio et al 2007b and references therein). This highlights the importance of an in-depth understanding of the general ecology of the study species before devising biologically meaningful estimates of individual quality.…”

Section: Discussionmentioning

confidence: 99%

“…For example, smaller males may be more productive but survive less well (e.g. McDonald et al 2005). Such antagonistic selective pressures may outweigh the eVect of individual quality over the long term.…”

Section: Discussionmentioning

confidence: 99%

“…Firstly, raptorial species show reversed sexual dimorphism, with frequently demonstrated advantages for reproduction associated with large size and large mass residuals for females and small size and small mass residuals for males (e.g. Massemin et al 2000;McDonald et al 2005;Sergio et al 2007b and references therein). Because of such opposing trends between the sexes, we always added the interaction term between sex and body size and between sex and mass residuals to the set of explanatory variables, so as to estimate individual quality in a more biologically meaningful manner.…”

Section: Statistical Analysesmentioning

confidence: 99%

“…We did not employ capture-recapture models to examine the eVects on recruitment for three reasons (see also Breininger and Carter 2003;McDonald et al 2005;Maguire 2006): (1) re-sighting probability in this population is nearly one (Forero et al 1999), and the detectability of breeding individuals is extremely high because all territories are repeatedly visited throughout the breeding season-the open landscape allows rings to be read from very far away, and only a handful of birds known to be marked eventually escape detection; (2) natal and breeding dispersal is extremely low in this population and emigration is virtually absent (Forero et al 1999(Forero et al , 2002, reducing the likelihood of some individuals being recruited elsewhere;…”

Section: Statistical Analysesmentioning

confidence: 99%

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Short- and long-term consequences of individual and territory quality in a long-lived bird

et al. 2009

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Site-quality is a major determinant of fitness but its effect can be confounded by individual quality, a relationship that has been little studied in large, long-lived vertebrates. The fitness effects of quality estimates depend on the assumption of co-variation between individual and territory quality and can be framed as five working hypotheses: no effect on fitness, exclusive effect of individual quality, exclusive effect of site quality, and independent or interactive effects of the two. We explored such a framework using a medium-sized raptor, the black kite Milvus migrans, as a model species. Individual and territory quality co-varied, but the strength of the relationship varied across different estimates of individual quality (age, body size, or mass residuals). Short-term production of fledglings was related to the independent effects of both individual and territory quality. However, longer-term production of recruits was related solely to territory quality. The disappearance of individual quality effects over the long-term may be caused by antagonistic selective pressures acting during different stages of the life cycle. Our results contribute to a growing appreciation of the long-term fitness-benefits of advantages experienced in early life and highlight the importance of a long-term perspective in studies assessing the effects of individual and territory quality. In our case study, prioritizing sites for conservation on the basis of territory quality may be a feasible pathway to maintain the viability of the population. However, scenarios where such a method could be inefficient have been previously reported, suggesting caution in its application. More studies are needed to understand the generality of the efficiency of priority-setting approaches based on site quality.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Statistical Analysesmentioning

confidence: 99%

Section: Statistical Analysesmentioning

confidence: 99%

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Short- and long-term consequences of individual and territory quality in a long-lived bird

et al. 2009

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“…A number of authors studying a range of animal types and performance traits have proposed that large body sizes per se increase fitness in animals, and summarized their results under the general premise of ''bigger is better'' (e.g., Lighton et al, 1994;Gabor, 1995;Ferguson, 2000;Schlupp et al, 2001;Steer et al, 2003;McDonald et al, 2005;Meekan et al, 2006;Kingsolver & Huey, 2008;MacNulty et al, 2009). However, this evidence is just a growing body of evidence that questions it using the even more trendy term ''bigger isn't always better'' (Knapp & Warner, 1991;Litvak & Leggett, 1992;Meyer, 1992;Sadowski et al, 1999;Topping & Millar, 1999;Gaillard et al, 2000;Pureswaran & Borden, 2003;Dibattista et al, 2007).…”

Section: Discussionmentioning

confidence: 99%

Viability selection on body size in a non-marine ostracod

et al. 2011

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One of the most important research topics in evolutionary ecology is body size evolution. Actually, several hypotheses have been proposed to explain the many observed patterns-also known as ''rules''-of body size variation in across latitude, temperature, and time. The temperature-size rule (TSR), describes an inverse relationship between body size and temperature. We took advantage of the ''natural laboratory'' that the crustacean populations at the Chilean altiplano offers, to study the TSR in ostracods. We studied three populations of Limnocythere atacamae that are physically separated by several kilometers, and differ mainly by their permanent thermal regime. We found larger individuals in the hotspring compared to the cold ponds. Also, in the hotspring we found a significant quadratic selection coefficient, suggesting stabilizing selection in this population. The fitness profiles showed stabilizing selection in the hotspring, and positive directional selection in the ponds. Our results suggest the existence of an optimal body size above the population means. This optimal size is apparently attained in the hotspring population. Then, natural selection appears to be promoting a shift in the mean phenotype that, for some reason, is not attained in the cold environments. Genetic slippage and population bottleneck would explain this absence of response to selection.

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Correlates of immune defenses in golden eagle nestlings

et al. 2017

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An individual's investment in constitutive immune defenses depends on both intrinsic and extrinsic factors. We examined how Leucocytozoon parasite presence, body condition (scaled mass), heterophil-to-lymphocyte (H:L) ratio, sex, and age affected immune defenses in golden eagle (Aquila chrysaetos) nestlings from three regions: California, Oregon, and Idaho. We quantified hemolytic-complement activity and bacterial killing ability, two measures of constitutive immunity. Body condition and age did not affect immune defenses. However, eagles with lower H:L ratios had lower complement activity, corroborating other findings that animals in better condition sometimes invest less in constitutive immunity. In addition, eagles with Leucocytozoon infections had higher concentrations of circulating complement proteins but not elevated opsonizing proteins for all microbes, and eagles from Oregon had significantly higher constitutive immunity than those from California or Idaho. We posit that Oregon eagles might have elevated immune defenses because they are exposed to more endoparasites than eagles from California or Idaho, and our results confirmed that the OR region has the highest rate of Leucocytozoon infections. Our study examined immune function in a free-living, long-lived raptor species, whereas most avian ecoimmunological research focuses on passerines. Thus, our research informs a broad perspective regarding the evolutionary and environmental pressures on immune function in birds.

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Selection on body size in a raptor with pronounced reversed sexual size dimorphism: are bigger females better?

Cited by 34 publications

References 49 publications

Short- and long-term consequences of individual and territory quality in a long-lived bird

Short- and long-term consequences of individual and territory quality in a long-lived bird

Viability selection on body size in a non-marine ostracod

Correlates of immune defenses in golden eagle nestlings

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