Why five fingers? Evolutionary constraints on digit numbers

Galis, Frietson; Alphen, Jacques J. M. van; Metz, J.A.J.

doi:10.1016/s0169-5347(01)02289-3

Cited by 130 publications

(138 citation statements)

References 44 publications

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“…An alternative interpretation of the staining of digit condensations is that the anterior-most condensation is not a digit, but rather a prepollex (Vargas and Fallon, 2005a;Wagner, 2005;Welten et al, 2005) similar to that found in several distantly related taxa including opossums and frogs (Fabrezi, 2001;Galis et al, 2001). In this case, consistent with the ASH (Fig.…”

Section: Embryological Evidencesupporting

confidence: 78%

“…In the bird wing, this digit, called the primary axis, develops in the posterior-most, fully formed digit position suggesting that it is digit IV, thus making the two anterior digits II and III (Mü ller and Alberch, 1990;Burke and Feduccia, 1997). Further supporting this diagnosis of digit identity, maintenance of digits II, III, and IV conforms to the more typical pattern of bilateral digit loss, with the loss of the last developing digits I and V preceding the loss of the earlier developing middle digits (Morse's Law; Morse, 1872;Sewertzoff, 1931;Greer, 1990Greer, , 1991Galis et al, 2001;Shapiro, 2002;Shapiro et al, 2003).…”

Section: Overview Of the Digit Identity Evidence: Conflicts And Propomentioning

confidence: 80%

“…There is no evidence in dinosaurs, or any archosaur, of a prepollex-a rudimentary extra digit that occurs anterior to position 1 (Larsson et al, 2010)-that characterizes many frog and mammal groups and that can be present as a polymorphic condition in salamanders and possibly some lizards (Wagner et al, 2000;Fabrezi, 2001;Galis et al, 2001). The anterior-most (preaxialmost) digit of theropods is characterized by a robust metacarpal whose distal articulation surface is formed by a pair of offset condyles that orient the two phalanges anteriorly.…”

Section: Developmental Dynamicsmentioning

confidence: 99%

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Identity of the avian wing digits: Problems resolved and unsolved

Young

Bever

Wang

et al. 2011

Developmental Dynamics

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Controversy over bird wing digit identity has been a touchstone for various ideas in the phylogeny of birds, homology, and developmental evolution. This review summarizes the past 10 years of progress toward understanding avian digit identity. We conclude that the sum of evidence supports the Frame Shift Hypothesis, indicating that the avian wing digits have changed anatomical location. Briefly, the derivation of birds from theropod dinosaurs and the positional identities of the avian wing digits as 2, 3, and 4 1 are no longer in question. Additionally, increasing evidence indicates that the developmental programs for identity of the wing digits are of digits I, II, and III. Therefore, the attention moves from whether the digit identity frame shift occurred, to what the mechanisms of the frame shift were, and when in evolution it happened. There is considerable uncertainty about these issues and we identify exciting new research directions to resolve them. Developmental Dynamics 240:1042-1053,

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Section: Embryological Evidencesupporting

confidence: 78%

Section: Overview Of the Digit Identity Evidence: Conflicts And Propomentioning

confidence: 80%

Section: Developmental Dynamicsmentioning

confidence: 99%

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Identity of the avian wing digits: Problems resolved and unsolved

Young

Bever

Wang

et al. 2011

Developmental Dynamics

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“…Wagner and Schwenk (2000) argue that such integration may overcome external selection pressure on individual characters comprising the ESC. Modularity of the developmental program is a manifestation of the internal co-ordination of embryogenesis that is related to character linkage (Wagner and Altenberg, '96;Galis et al, 2001). …”

Section: Generative and Selective Constraintsmentioning

confidence: 99%

“…However, Wagner and Müller (2002) reanalysed the dataset and concluded that abdominal lobes had failed to evolve in some lineages, despite appropriate selection pressures; this supports the hypothesis of constraint. See also Galis et al (2001) for a non-quantitative, character-based approach to the analysis of constraint in the mid-embryonic (phylotypic) period.…”

Section: Introductionmentioning

confidence: 99%

Developmental constraints in a comparative framework: A test case using variations in phalanx number during amniote evolution

Richardson

Chipman

2003

J Exp Zool Pt B

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Constraints are factors that limit evolutionary change. A subset of constraints is developmental, and acts during embryonic development. There is some uncertainty about how to define developmental constraints, and how to formulate them as testable hypotheses. Furthermore, concepts such as constraint-breaking, universal constraints, and forbidden morphologies present some conceptual difficulties. One of our aims is to clarify these issues. After briefly reviewing current classifications of constraint, we define developmental constraints as those affecting morphogenetic processes in ontogeny. They may be generative or selective, although a clear distinction cannot always be drawn. We support the idea that statements about constraints are in fact statements about the relative frequency of particular transformations (where 'transformation' indicates a change from the ancestral condition). An important consequence of this is that the same transformation may be constrained in one developmental or phylogenetic context, but evolutionarily plastic in another. In this paper, we analyse developmental constraints within a phylogenetic framework, building on similar work by previous authors. Our approach is based on the following assumptions from the literature: (1) constraints are identified when there is a discrepancy between the observed frequency of a transformation, and its expected frequency; (2) the 'expected' distribution is derived by examining the phylogenetic distribution of the transformation and its associated selection pressures. Thus, by looking for congruence between these various phylogenetic distribution patterns, we can test hypotheses about constraint. We critically examine this approach using a test case: variation in phalanx-number in the amniote limb.

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Development and Evolution

Schoch¹

2014

Amphibian Evolution

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Why five fingers? Evolutionary constraints on digit numbers

Cited by 130 publications

References 44 publications

Identity of the avian wing digits: Problems resolved and unsolved

Identity of the avian wing digits: Problems resolved and unsolved

Developmental constraints in a comparative framework: A test case using variations in phalanx number during amniote evolution

Development and Evolution

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