Non–random fitness variation in two populations of Darwin's finches

Grant, Peter R.; Grant, B. Rosemary

doi:10.1098/rspb.2000.0977

Cited by 75 publications

(51 citation statements)

References 31 publications

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“…On the other hand, our results do agree with previous studies conducted on laboratory and wild rodents which find no evidence of V A in metabolic traits (Lacy and Lynch 1979;Lynch et al 1988;Dohm et al 1996Dohm et al , 2001Nespolo et al 2003a). Concerning morphological traits, many studies have reported high values of h 2 (Boonstra and Boag 1987;Roff 1997;Endler 2000;Grant and Grant 2000;Hoffman 2000;Kruuk et al 2000;Brooks and Endler 2001), which is in agreement with a previous study on P. darwini that also found high h 2 for tarsus length (Nespolo et al 2003a). Conversely we found h 2 not different from zero for the dry masses of central organs, with the exception of the liver (h 2 ϭ 0.73).…”

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confidence: 79%

The Quantitative Genetics of Sustained Energy Budget in a Wild Mouse

et al. 2004

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Abstract. We explored how morphological and physiological traits associated with energy expenditure over long periods of cold exposure would be integrated in a potential response to natural selection in a wild mammal, Phyllotis darwini. In particular, we studied sustained energy expenditure (SusMR), the rate of expenditure fueled by concurrent energy intake, basal metabolic rate (BMR), and sustained metabolic scope (SusMS ϭ SusMR/BMR), a measure of the reserve for sustained work. We included the masses of different central processing organs as an underlying factor that could have a mechanistic link with whole animal traits. Only the liver had heritability statistically different from zero (0.73). Physiological and morphological traits had high levels of specific environmental variance (average 70%) and postnatal common environmental variance (average 30%) which could explain the low heritabilities estimates. Our results, (1) are in accordance with previous studies in mammals that report low heritabilities for metabolic traits (SusMR, BMR, SusMS), (2) but not completely with previous ones that report high heritabilities for morphological traits (masses of central organs), and (3) provide important evidence of the relevance of postnatal common environmental variance to sustained energy expenditure.Key words. Energy budget, heritability, mammal, sustained metabolic rate.Received June 25, 2003. Accepted September 22, 2003 In recent years the evolutionary role of physiological variation within natural populations has been a subject of intensive research (Garland and Carter 1994;Bradley and Zamer 1999;Feder et al. 2000). A key parameter focused in many of the studies is the narrow-sense heritability (h 2 ) or the proportion of population phenotypic variance of a trait that is additive genetic (Roff 1997). This is because the extent of the evolutionary response to natural or sexual selection is dependent on the magnitude of h 2 . However, organisms comprise far more than just one trait, and thus the evolutionary response to selection could involve simultaneous modifications of several traits at the same time, and at different levels of biological organization . The estimation of genetic covariances among several different traits are indispensable in predicting the evolutionary response to selection (Arnold 1994). These covariances could show if multivariate evolution could be facilitated or constrained among a particular set of traits (Arnold 1994).In seasonal environments, daily and seasonal variations in ambient temperature represent an important challenge to small nonhibernating eutherian mammals (McNab 2002), and therefore mechanisms that control thermoregulatory homeostasis are paramount (Lynch 1994; Nespolo et al. 2003a,b). In addition, it is well known that acclimatization to cold in small mammals involves aspects of physiology, behavior, and morphology (Geiser et al. 1996). However, it is less clear whether an evolutionary response could take place in traits related to thermogenic capacity and whether such a re...

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confidence: 79%

The Quantitative Genetics of Sustained Energy Budget in a Wild Mouse

et al. 2004

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“…lifetime reproductive success) would require multigeneration pedigrees, which could not be obtained. Regardless, previous work on G. fortis has confirmed that 'the most important determinant of fitness is the ability of an individual to survive to breed in many years' (Grant & Grant 2000). One of the reasons is that periodic droughts (and other factors) can eliminate reproduction and cause very high adult mortality in a given year.…”

Section: Methodsmentioning

confidence: 99%

“…At the outset, an ancestral species colonized multiple islands characterized by ecological differences, such as different seed size distributions. Resulting divergent selection among allopatric populations then caused their adaptive divergence, most notably in beak and body dimensions (Bowman 1961;Abbott et al 1977;Schluter & Grant 1984;Grant & Grant 2000, 2008. Next, further dispersal among the islands brought some allopatric forms back into secondary contact (Grant 1986;Petren et al 2005;), where several outcomes were possible.…”

Section: Introductionmentioning

confidence: 99%

Disruptive selection in a bimodal population of Darwin's finches

et al. 2008

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A key part of the ecological theory of adaptive radiation is disruptive selection during periods of sympatry. Some insight into this process might be gained by studying populations that are bimodal for dual-context traits, i.e. those showing adaptive divergence and also contributing to reproductive isolation. A population meeting these criteria is the medium ground finch (Geospiza fortis) of El Garrapatero, Santa Cruz Island, Galápagos. We examined patterns of selection in this population by relating individual beak sizes to interannual recaptures during a prolonged drought. Supporting the theory, disruptive selection was strong between the two beak size modes. We also found some evidence of selection against individuals with the largest and smallest beak sizes, perhaps owing to competition with other species or to gaps in the underlying resource distribution. Selection may thus simultaneously maintain the current bimodality while also constraining further divergence. Spatial and temporal variation in G. fortis bimodality suggests a dynamic tug of war among factors such as selection and assortative mating, which may alternatively promote or constrain divergence during adaptive radiation.

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“…He became almost completely silent and then paired not with a G. magnirostris female but with a G. fortis female. In this case, pair formation was based on morphology and not on song (Grant & Grant 2008 (Grant & Grant 2000). With beaks of generally intermediate size hybrids can feed on small soft seeds but are unable to crack the large and hard seeds of T. cistoides, even though they occasionally try.…”

Section: Hybridizationmentioning

confidence: 99%

Fission and fusion of Darwin's finches populations

Grant

2008

Phil. Trans. R. Soc. B

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147

165

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This study addresses the causes and evolutionary consequences of introgressive hybridization in the sympatric species of Darwin's ground finches (Geospiza) on the small island of Daphne Major in the Galápagos archipelago. Hybridization occurs rarely (less than 2% of breeding pairs) but persistently across years, usually as a result of imprinting on the song of another species. Hybrids survive well under some ecological conditions, but not others. Hybrids mate according to song type. The resulting introgression increases phenotypic and genetic variation in the backcrossed populations. Effects of introgression on beak shape are determined by the underlying developmental genetic pathways. Introgressive hybridization has been widespread throughout the archipelago in the recent past, and may have been a persistent feature throughout the early history of the radiation, episodically affecting both the speed and direction of evolution. We discuss how fission through selection and fusion through introgression in contemporary Darwin's finch populations may be a reflection of processes occurring in other young radiations. We propose that introgression has the largest effect on the evolution of interbreeding species after they have diverged in morphology, but before the point is reached when genetic incompatibilities incur a severe fitness cost.

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Non–random fitness variation in two populations of Darwin's finches

Cited by 75 publications

References 31 publications

The Quantitative Genetics of Sustained Energy Budget in a Wild Mouse

The Quantitative Genetics of Sustained Energy Budget in a Wild Mouse

Disruptive selection in a bimodal population of Darwin's finches

Fission and fusion of Darwin's finches populations

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