Tuesday, January 9, 2018

[Invertebrate • 2018] Phylogenomics Illuminates the Backbone of the Myriapoda Tree of Life and Reconciles Morphological and Molecular Phylogenies


Figure 1. The four main groups of myriapods. AOtostigmus (Parotostigmuspococki (Northern Range, Trinidad, Trinidad and Tobago) (Chilopoda, Scolopendromorpha); BHanseniella sp. (South Island, New Zealand) (Symphyla, Scutigerellidae); CPauropus huxleyi (Massachusetts, USA) (Pauropoda, Tetramerocerata); and DPlatydesmus sp. (La Selva, Costa Rica) (Diplopoda, Platydesmida).
Fernández, Edgecombe & Giribet, 2018.

Abstract
The interrelationships of the four classes of Myriapoda have been an unresolved question in arthropod phylogenetics and an example of conflict between morphology and molecules. Morphology and development provide compelling support for Diplopoda (millipedes) and Pauropoda being closest relatives, and moderate support for Symphyla being more closely related to the diplopod-pauropod group than any of them are to Chilopoda (centipedes). In contrast, several molecular datasets have contradicted the Diplopoda–Pauropoda grouping (named Dignatha), often recovering a Symphyla–Pauropoda group (named Edafopoda). Here we present the first transcriptomic data including a pauropod and both families of symphylans, allowing myriapod interrelationships to be inferred from phylogenomic data from representatives of all main lineages. Phylogenomic analyses consistently recovered Dignatha with strong support. Taxon removal experiments identified outgroup choice as a critical factor affecting myriapod interrelationships. Diversification of millipedes in the Ordovician and centipedes in the Silurian closely approximates fossil evidence whereas the deeper nodes of the myriapod tree date to various depths in the Cambrian-Early Ordovician, roughly coinciding with recent estimates of terrestrialisation in other arthropod lineages, including hexapods and arachnids.

Figure 2A. Preferred phylogenetic hypothesis of myriapod interrelationships (PhyloBayes, matrix 1). 2B. DensiTree visualization of the four most congruent analyseis (PhyloBayes, matrices 2 and 3; PhyML, matrix 3). 2C, 2D. Main conflicting alternative hypothesis (2C, PhyML, matrix 2; 2D, PhyML, matrix 1). 2E. Phylogenetic hypothesis of Myriapoda based on 232 morphological characters coded for both extant and extinct species (see Methods for further details); strict consensus of 488 trees of 257 steps; Fossil taxa are identified with a dagger symbol. Black circles in nodes represent high support (> 95% posterior probability, > 90% bootstrap support). CHE: Chelicerata. PAN: Pancrustacea. CHI: Chilopoda. SYM: Symphyla. PAU: Pauropoda. DIP: Diplopoda. Colour codes for each clade are maintained in all figures.

Figure 1. The four main groups of myriapods.
AOtostigmus (Parotostigmuspococki (Northern Range, Trinidad, Trinidad and Tobago) (Chilopoda, Scolopendromorpha); BHanseniella sp. (South Island, New Zealand) (Symphyla, Scutigerellidae); CPauropus huxleyi (Massachusetts, USA) (Pauropoda, Tetramerocerata); and DPlatydesmus sp. (La Selva, Costa Rica) (Diplopoda, Platydesmida).

Rosa Fernández, Gregory D. Edgecombe and Gonzalo Giribet. 2018. Phylogenomics Illuminates the Backbone of the Myriapoda Tree of Life and Reconciles Morphological and Molecular Phylogenies. Scientific Reports. 8, 83.  DOI:  10.1038/s41598-017-18562-w

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