Integration, heterochrony, and adaptation in pedal digits of syndactylous marsupials

Weisbecker, Vera and Nilsson, Maria (2008) Integration, heterochrony, and adaptation in pedal digits of syndactylous marsupials. BMC Evolutionary Biology, 8 160.1-160.14. doi:10.1186/1471-2148-8-160


Author Weisbecker, Vera
Nilsson, Maria
Title Integration, heterochrony, and adaptation in pedal digits of syndactylous marsupials
Journal name BMC Evolutionary Biology   Check publisher's open access policy
ISSN 1471-2148
Publication date 2008-05
Sub-type Article (original research)
DOI 10.1186/1471-2148-8-160
Open Access Status DOI
Volume 8
Start page 160.1
End page 160.14
Total pages 14
Place of publication London, United Kingdom
Publisher BioMed Central
Language eng
Formatted abstract
Background: Marsupial syndactyly is a curious morphology of the foot found in all species of diprotodontian and peramelemorph marsupials. It is traditionally defined as a condition in which digits II and III of the foot are bound by skin and are reduced. Past treatments of marsupial syndactyly have not considered the implications of this unique morphology for broader issues of digit development and evolution, and the ongoing debate regarding its phylogenetic meaning lacks a broad empirical basis. This study undertakes the first interdisciplinary characterisation of syndactyly, using variance/covariance matrix comparisons of morphometric measurements, locomotor indices, ossification sequences, and re-assessment of the largely anecdotal data on the phylogenetic distribution of tarsal/metatarsal articulations and "incipient syndactyly".

Results: Syndactylous digits have virtually identical variance/covariance matrices and display heterochronic ossification timing with respect to digits IV/V. However, this does not impact on overall locomotor adaptation patterns in the syndactylous foot as determined by analysis of locomotor predictor ratios. Reports of incipient syndactyly in some marsupial clades could not be confirmed; contrary to previous claims, syndactyly does not appear to impact on tarsal bone arrangement.

Conclusion: The results suggest that marsupial syndactyly originates from a constraint that is rooted in early digit ontogeny and results in evolution of the syndactylous digits as a highly integrated unit. Although convergent evolution appears likely, syndactyly in Diprotodontia and Peramelemorpha may occur through homologous developmental processes. We argue that the term "syndactyly" is a misnomer because the marsupial condition only superficially resembles its name-giving human soft-tissue syndactyly.
Keyword Marsupial syndactyly
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ
Additional Notes Article number 160

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Biological Sciences Publications
 
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Created: Mon, 08 Apr 2013, 22:43:09 EST by Gail Walter on behalf of School of Biological Sciences