Data congruence, paedomorphosis and salamanders.

Torsten H Struck

doi:10.1186/1742-9994-4-22

Abstract

BackgroundThe retention of ancestral juvenile characters by adult stages of descendants is called paedomorphosis. However, this process can mislead phylogenetic analyses based on morphological data, even in combination with molecular data, because the assessment if a character is primary absent or secondary lost is difficult. Thus, the detection of incongruence between morphological and molecular data is necessary to investigate the reliability of simultaneous analyses. Different methods have been proposed to detect data congruence or incongruence. Five of them (PABA, PBS, NDI, LILD, DRI) are used herein to assess incongruence between morphological and molecular data in a case study addressing salamander phylogeny, which comprises several supposedly paedomorphic taxa. Therefore, previously published data sets were compiled herein. Furthermore, two strategies ameliorating effects of paedomorphosis on phylogenetic studies were tested herein using a statistical rigor. Additionally, efficiency of the different methods to assess incongruence was analyzed using this empirical data set. Finally, a test statistic is presented for all these methods except DRI.ResultsThe addition of morphological data to molecular data results in both different positions of three of the four paedomorphic taxa and strong incongruence, but treating the morphological data using different strategies ameliorating the negative impact of paedomorphosis revokes these changes and minimizes the conflict. Of these strategies the strategy to just exclude paedomorphic character traits seem to be most beneficial. Of the three molecular partitions analyzed herein the RAG1 partition seems to be the most suitable to resolve deep salamander phylogeny. The rRNA and mtDNA partition are either too conserved or too variable, respectively. Of the different methods to detect incongruence, the NDI and PABA approaches are more conservative in the indication of incongruence than LILD and PBS.ConclusionPaedomorphosis induces strong conflicts and can mislead the phylogenetic analyses even in combined analyses. However, different strategies are efficiently minimizing these problems. Though the exploration of different methods to detect incongruence is preferable NDI and PABA are more conservative than the others and NDI is computational less extensive than PABA.

Highlights

The retention of ancestral juvenile characters by adult stages of descendants is called paedomorphosis
Paedomorphosis, morphology and conflict The addition of morphological data to molecular data changed the phylogenetic positions of three of the four paedomorphic taxa included in this study
Paedomorphosis can influence the phylogenetic reconstruction of salamander phylogeny even in combination with a large molecular data set

Summary

Introduction

The retention of ancestral juvenile characters by adult stages of descendants is called paedomorphosis This process can mislead phylogenetic analyses based on morphological data, even in combination with molecular data, because the assessment if a character is primary absent or secondary lost is difficult. Wiens et al [2] coded the adult morphology of paedomorphic taxa as unknown, because adult, sexually mature stages of paedomorphic and non-paedomorphic species are not comparable ontogenetic stages Though this strategy might be overly conservative by deleting characters not affected by paedomorphosis Wiens et al [2] favoured this strategy over another strategy, which was adopted by them as well as other authors [e.g., [33]]. Priority of the first strategy over the second one was not tested using a statistical rigor

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Results

Discussion

Conclusion