Body and Limb Size Dissociation at the Origin of Birds: Uncoupling Allometric Constraints Across a Macroevolutionary Transition

Dececchi, T. Alexander; Larsson, Hans C. E.

doi:10.1111/evo.12150

Cited by 84 publications

(122 citation statements)

References 72 publications

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“…Tradeoffs between wings and legs would have become more important during the later phases of flight evolution: once fully powered flight was acquired, selection for enhanced forelimb investment and performance may have favored reduced hindlimb investment and performance (and vice versa), culminating in the explosion of locomotor strategies observed among birds today (Fig. ; see Dececchi and Larsson for patterns consistent with tradeoffs and Benson and Choiniere for patterns of diversity).…”

Section: Discussionmentioning

confidence: 99%

Wings versus legs in the avianbauplan: Development and evolution of alternative locomotor strategies

2015

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Wings have long been regarded as a hallmark of evolutionary innovation, allowing insects, birds, and bats to radiate into aerial environments. For many groups, our intuitive and colloquial perspective is that wings function for aerial activities, and legs for terrestrial, in a relatively independent manner. However, insects and birds often engage their wings and legs cooperatively. In addition, the degree of autonomy between wings and legs may be constrained by tradeoffs, between allocating resources to wings versus legs during development, or between wing versus leg investment and performance (because legs must be carried as baggage by wings during flight and vice versa). Such tradeoffs would profoundly affect the development and evolution of locomotor strategies, and many related aspects of animal ecology. Here, we provide the first evaluation of wing versus leg investment, performance and relative use, in birds-both across species, and during ontogeny in three precocial species with different ecologies. Our results suggest that tradeoffs between wing and leg modules help shape ontogenetic and evolutionary trajectories, but can be offset by recruiting modules cooperatively. These findings offer a new paradigm for exploring locomotor strategies of flying organisms and their extinct precursors, and thereby elucidating some of the most spectacular diversity in animal history.

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Section: Discussionmentioning

confidence: 99%

Wings versus legs in the avianbauplan: Development and evolution of alternative locomotor strategies

2015

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“…Other classic avian features, such as the keeled breastbone to support flight muscles and highly reduced tail, evolved after the origin of birds, meaning that the earliest birds looked more like dinosaurs in lacking these features. Long-term trends in skeletal proportions and musculature across dinosaurs and early birds led to two of the most characteristic features of living birds: the elongated arms, which became wings in birds ( [45], but see [46]); and the bizarre 'crouched' hindlimb posture, in which the femur is held nearly horizontal and most of the locomotory activity of the hindlimb occurs at the knee joint rather than the pelvic joint [47].…”

Section: The Assembly Of the Bird Body Plan And Classic Avian Behaviorsmentioning

confidence: 99%

The Origin and Diversification of Birds

2015

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Birds are one of the most recognizable and diverse groups of modern vertebrates. Over the past two decades, a wealth of new fossil discoveries and phylogenetic and macroevolutionary studies has transformed our understanding of how birds originated and became so successful. Birds evolved from theropod dinosaurs during the Jurassic (around 165-150 million years ago) and their classic small, lightweight, feathered, and winged body plan was pieced together gradually over tens of millions of years of evolution rather than in one burst of innovation. Early birds diversified throughout the Jurassic and Cretaceous, becoming capable fliers with supercharged growth rates, but were decimated at the end-Cretaceous extinction alongside their close dinosaurian relatives. After the mass extinction, modern birds (members of the avian crown group) explosively diversified, culminating in more than 10,000 species distributed worldwide today.

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“…The origin of modern birds from their dinosaurian ancestors is one of the most celebrated and scrutinized evolutionary transitions (Zhou, 2004;Turner et al, 2007;Chiappe, 2009;Benson & Choiniere, 2013;Dececchi & Larsson, 2013;Benson et al, 2014;Brusatte Stephen et al, 2014;Puttick et al, 2014). Particularly in recent years, the rate of morphological change leading to the explosion of avian diversity we see today has been a hot-bed of activity and controversy (Benson & Choiniere, 2013;Benson et al, 2014;Brusatte Stephen et al, 2014;Lee et al, 2014b;Puttick et al, 2014).…”

Section: Relative Limb Proportions In Dinosauriamentioning

confidence: 99%

Positive phenotypic selection inferred from phylogenies

Baker

Meade

Pagel

et al. 2015

Biol. J. Linn. Soc.

188

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Rates of phenotypic evolution vary widely in nature and these rates may often reflect the intensity of natural selection. Here we outline an approach for detecting exceptional shifts in the rate of phenotypic evolution across phylogenies. We introduce a simple new branch-specific metric Δ V /Δ B that divides observed phenotypic change along a branch into two components: (1) that attributable to the background rate (Δ B ), and (2) that attributable to departures from the background rate (Δ V ). Where the amount of expected change derived from variation in the rate of morphological evolution doubles that explained by to the background rate (Δ V /Δ B > 2), we identify this as positive phenotypic selection. We apply our approach to six datasets, finding multiple instances of positive selection in each. Our results support the growing appreciation that the traditional gradual view of phenotypic evolution is rarely upheld, with a more episodic view taking its place. This moves focus away from viewing phenotypic evolution as a simple homogeneous process and facilitates reconciliation with macroevolutionary interpretations from a genetic perspective, paving the way to novel insights into the link between genotype and phenotype. The ability to detect positive selection when genetic data are unavailable or unobtainable represents an attractive prospect for extant species, but when applied to fossil data it can reveal patterns of natural selection in deep time that would otherwise be impossible.

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Body and Limb Size Dissociation at the Origin of Birds: Uncoupling Allometric Constraints Across a Macroevolutionary Transition

Cited by 84 publications

References 72 publications

Wings versus legs in the avianbauplan: Development and evolution of alternative locomotor strategies

Wings versus legs in the avianbauplan: Development and evolution of alternative locomotor strategies

The Origin and Diversification of Birds

Positive phenotypic selection inferred from phylogenies

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