Monogenean anchor morphometry: systematic value, phylogenetic signal, and evolution
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Abstract
Anchors are important attachment appendages that prevent the physical dislodging of a monogenean parasite from fish host gills. Common descent and evolutionary processes have left their mark on anchor morphometry, in the form of patterns of shape and size variation useful for systematic and evolutionary studies. We used a geometric morphometric approach to explore anchor shape variation in 13 Ligophorus (Monogenea:Ancyrocephalidae) species infecting two marine mugilid (Teleostei: Mugilidae) fish hosts (Moolgarda buchanani and Liza subviridis) in the waters off West Peninsular Malaysia. Molecular sequence data from three nuclear markers: 28S rRNA, 18S rRNA and ITS1, were used to infer a maximum likelihood phylogeny to enable visualization of shape evolution in phylomorphospace. For inferring patterns of size evolution in the phylogeny, we used a size measure based on the first principal component of all pairwise Euclidean distances between landmarks. Cluster heat map and principal component analysis showed that anchor shape variation had sufficient systematic information for delimiting 12 of the 13 species. Adams' multivariate K test indicated significant correlation between anchor shape and phylogeny (p-value = 0.0001). We also discovered that characters based on anchor shaft shape, the length between inner and outer root tips and the length between inner root tip and the dent point were more phylogenetically informative than inner and outer lengths, as indicated by a maximum parsimony tree that was better resolved and had major clades congruent with those of the molecular phylogenetic tree. Continuous character mapping of size onto the inferred molecular phylogeny and Rayleigh’s test for departure from directional uniformity in each species’s landmark relative to the ancestor indicated that species infecting M. buchanani generally evolved larger and more robust anchors, while those infecting L. subviridis generally evolved smaller and more delicate anchors. Nevertheless, phylogenetic regression of anchor shape against body size and anchor size showed significant correlation (p-value = 0.02) between anchor shape and size, suggesting morphometric constraints in anchor evolution. Finally, morphological integration analysis revealed tight integration between the root and point compartments within anchors, confirming that the anchor functions as a single, fully integrated module. The present work is supported by the development of integrative analytical tools in the form of a new R package – monogeneaGM. By lowering barriers to data integration and analysis , we aim to encourage the scientific community to collect and contribute morphometric and genetic data from other Ligophorus species, which are essential for developing Ligophorus as a model system for understanding association between patterns of anchor shape size evolution and biodiversity in the Monogenea.
Cite this as
2015. Monogenean anchor morphometry: systematic value, phylogenetic signal, and evolution. PeerJ PrePrints 3:e1283v1 https://doi.org/10.7287/peerj.preprints.1283v1note This preprint is not peer-reviewed. You may wish to reference the subsequent peer-reviewed version of this article.
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This manuscript draft is version 1.0 and will be submitted soon for peer-review elsewhere.
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Competing Interests
The authors declare that they have no competing interests.
Author Contributions
Tsung Fei Khang conceived and designed the experiments, performed the experiments, analyzed the data, contributed reagents/materials/analysis tools, wrote the paper, prepared figures and/or tables, reviewed drafts of the paper.
Oi Yoon Michelle Soo performed the experiments, analyzed the data, contributed reagents/materials/analysis tools, wrote the paper, prepared figures and/or tables, reviewed drafts of the paper.
Wooi Boon Tan performed the experiments, analyzed the data, contributed reagents/materials/analysis tools, wrote the paper, prepared figures and/or tables, reviewed drafts of the paper.
Lee Hong Susan Lim conceived and designed the experiments.
DNA Deposition
The following information was supplied regarding the deposition of DNA sequences:
GenBank
KM221934
KM221935
KM221936
KM221937
KM262663
KM221944
KM221945
KM221938
KM221941
KM221942
KM221939
KM221940
KM221943
Funding
This work was supported by University of Malaya Research Grant RG 197/12SUS to TFK and LHSL, and RP004D-13SUS to LHSL, WBT and TFK. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
