Phylogeny and biogeography of the Cavernicola (Platyhelminthes: Tricladida): Relicts of an epigean group sheltering in caves?

[Display omitted] •First molecular phylogeny of a rare (11 species) planarian suborder, Cavernicola.•Confirms monophyly, Maricola sistership and their status as a distinct suborder.•Freshwater and epigean in origin, colonized both epigean and hypogean habitats.•Disjunct distribution may be due to Go...

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Published in:Molecular phylogenetics and evolution 2020-04, Vol.145, p.106709-106709, Article 106709
Main Authors: Benítez-Álvarez, Lisandra, Maria Leal-Zanchet, Ana, Oceguera-Figueroa, Alejandro, Lopes Ferreira, Rodrigo, de Medeiros Bento, Diego, Braccini, João, Sluys, Ronald, Riutort, Marta
Format: Article
Language:English
Subjects:
Gondwana
Molecular phylogeny
Pangea
Taxonomy
Troglobitic flatworms
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Summary:[Display omitted] •First molecular phylogeny of a rare (11 species) planarian suborder, Cavernicola.•Confirms monophyly, Maricola sistership and their status as a distinct suborder.•Freshwater and epigean in origin, colonized both epigean and hypogean habitats.•Disjunct distribution may be due to Gondwana origin, and loss of most epigean diversity.•Genetic diversity and new findings foreshadow more species to be discovered. The planarian suborder Cavernicola Sluys, 1990 was originally created to house five species of triclad flatworms with special morphological features and a surprisingly discontinuous and broad geographic distribution. These five species could not be accommodated with any degree of certainty in any of the three taxonomic groups existing at that moment, viz., Paludicola Hallez, 1892, Terricola Hallez, 1892, and Maricola Hallez, 1892. The scarce representation of the group and the peculiarities of the morphological features of the species, including several described more recently, have complicated new tests of the monophyly of the Cavernicola, the assessment of its taxonomic status, as well as the resolution of its internal relationships. Here we present the first molecular study including all genera currently known for the group, excepting one. We analysed newly generated 18S and 28S rDNA data for these species, together with a broad representation of other triclad flatworms. The resulting phylogenetic trees supported the monophyly of the Cavernicola, as well as its sister-group relationship to the Maricola. The sister-group relationship to the Maricola and affinities within the Cavernicola falsify the morphology-based phylogeny of the latter that was proposed previously. The relatively high diversity of some cavernicolan genera suggests that the presumed rarity of the group actually may in part be due to a collecting artefact. Ancestral state reconstruction analyses suggest that the ancestral habitat of the group concerned epigean freshwater conditions. Our results point to an evolutionary scenario in which the Cavernicola (a) originated in a freshwater habitat, (b) as the sister clade of the marine triclads, and (c) subsequently radiated and colonized both epigean and hypogean environments. Competition with other planarians, notably members of the Continenticola, or changes in epigean habitat conditions are two possible explanations -still to be tested- for the loss of most epigean diversity of the Cavernicola, which is currently reflec
ISSN:1055-7903
1095-9513
DOI:10.1016/j.ympev.2019.106709