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A large-scale survey of heterochrony in anuran cranial ossification patterns


Weisbecker, V; Mitgutsch, C (2010). A large-scale survey of heterochrony in anuran cranial ossification patterns. Journal of Zoological Systematics and Evolutionary Research, 48(4):332-347.

Abstract

Most anurans have a biphasic life cycle, which includes metamorphosis from a tadpole stage to an adult frog. This process involves extensive transformations of the cranial skeleton, which have been of long-standing interest with respect to anuran skeletal evolution and taxonomy. In this study, large-scale patterns of anuran skeletal ossification are assessed by collecting the most comprehensive data set on anuran cranial ossification to date from the literature, including data for 45 anuran and one caudate outgroup species. Ossification sequences were translated into event-pair matrices for explorative phylogenetic analysis and phylogenetically informed parsimony search for heterochrony using the Parsimov algorithm. Rank variability of single bones across species was also analysed. Little phylogenetic signal was retrieved from a parsimony-based phylogenetic analysis of event-pairs, and only a few species that are generally agreed to be closely related are placed close to each other (e.g. some Pipidae and Costata). Parsimov analysis revealed some clade-specific heterochrony in anuran clades of varying inclusiveness. Our results show that relating heterochronic changes in anuran cranial ontogeny to parameters such as direct development or miniaturization is problematic because of the high evolvability of cranial ossification sequences. Rank variation analysis suggests that anuran cranial bones are highly variable in their sequence positioning, possibly because tadpole and adult cranial morphology do not co-evolve. Elements which are lost in some species ossify at the end of the sequence, providing evidence for the notion that failure of anuran cranial elements to ossify is due to processes of paedomorphosis.

Abstract

Most anurans have a biphasic life cycle, which includes metamorphosis from a tadpole stage to an adult frog. This process involves extensive transformations of the cranial skeleton, which have been of long-standing interest with respect to anuran skeletal evolution and taxonomy. In this study, large-scale patterns of anuran skeletal ossification are assessed by collecting the most comprehensive data set on anuran cranial ossification to date from the literature, including data for 45 anuran and one caudate outgroup species. Ossification sequences were translated into event-pair matrices for explorative phylogenetic analysis and phylogenetically informed parsimony search for heterochrony using the Parsimov algorithm. Rank variability of single bones across species was also analysed. Little phylogenetic signal was retrieved from a parsimony-based phylogenetic analysis of event-pairs, and only a few species that are generally agreed to be closely related are placed close to each other (e.g. some Pipidae and Costata). Parsimov analysis revealed some clade-specific heterochrony in anuran clades of varying inclusiveness. Our results show that relating heterochronic changes in anuran cranial ontogeny to parameters such as direct development or miniaturization is problematic because of the high evolvability of cranial ossification sequences. Rank variation analysis suggests that anuran cranial bones are highly variable in their sequence positioning, possibly because tadpole and adult cranial morphology do not co-evolve. Elements which are lost in some species ossify at the end of the sequence, providing evidence for the notion that failure of anuran cranial elements to ossify is due to processes of paedomorphosis.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Paleontological Institute and Museum
Dewey Decimal Classification:560 Fossils & prehistoric life
Uncontrolled Keywords: * Event-pairs; * heterochrony; * Anura; * ossification; * cranium
Language:English
Date:November 2010
Deposited On:04 Nov 2010 13:30
Last Modified:05 Apr 2016 14:14
Publisher:Wiley-Blackwell
ISSN:0947-5745
Publisher DOI:https://doi.org/10.1111/j.1439-0469.2010.00570.x

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