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The evolutionary origins of the southern ocean Philobryid bivalves: hidden biodiversity, ancient persistence.

Jackson JA, Linse K, Whittle R, Griffiths HJ - PLoS ONE (2015)

Bottom Line: The A. nitens species complex is identified as at least seven morpho-species through morphological and genetic analysis of taxon clustering.Phylogenetic analyses resolve Philobryidae as a strongly supported monophyletic clade and sister taxon to the Limopsidae, as anticipated by their classification into the superfamily Limopsoidea.Bayesian relaxed clock analyses of divergence times suggest that genus Adacnarca radiated in the Southern Ocean from the Early Paleogene, while P. sublaevis and P. wandelensis clades radiated in the late Miocene, following the formation of the Antarctic Circumpolar Current.

View Article: PubMed Central - PubMed

Affiliation: British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 0ET, United Kingdom.

ABSTRACT
Philobryids (Bivalvia: Arcoida) are one of the most speciose marine bivalve families in the Southern Ocean and are common throughout the Southern Hemisphere. Considering this diversity and their brooding reproductive mode (limiting long-distance dispersal), this family may have been present in the Southern Ocean since its inception. However Philobrya and Adacnarca appear only in the Quaternary fossil record of the Antarctic, suggesting a much more recent incursion. Molecular dating provides an independent means of measuring the time of origin and radiation of this poorly known group. Here we present the first combined molecular and morphological investigation of the Philobryidae in the Southern Ocean. Two nuclear loci (18S and 28S) were amplified from 35 Southern Ocean Adacnarca and Philobrya specimens, with a combined sequence length of 2,282 base pairs (bp). Adacnarca specimens (A. nitens and A. limopsoides) were resolved as a strongly supported monophyletic group. Genus Philobrya fell into two strongly supported groups ('sublaevis' and 'magellanica/wandelensis'), paraphyletic with Adacnarca. The A. nitens species complex is identified as at least seven morpho-species through morphological and genetic analysis of taxon clustering. Phylogenetic analyses resolve Philobryidae as a strongly supported monophyletic clade and sister taxon to the Limopsidae, as anticipated by their classification into the superfamily Limopsoidea. Bayesian relaxed clock analyses of divergence times suggest that genus Adacnarca radiated in the Southern Ocean from the Early Paleogene, while P. sublaevis and P. wandelensis clades radiated in the late Miocene, following the formation of the Antarctic Circumpolar Current.

No MeSH data available.


Molecular phylogeny of 28S.Node values show Bayesian posterior probabilities (as %) and maximum likelihood bootstrap support respectively. Coloured bars show species units identified using ABGD and GMYC.
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pone.0121198.g006: Molecular phylogeny of 28S.Node values show Bayesian posterior probabilities (as %) and maximum likelihood bootstrap support respectively. Coloured bars show species units identified using ABGD and GMYC.

Mentions: The monophyly of this genus is strongly supported by the 18S+28S dataset only (0.98 BPP) and by SH testing of both gene datasets (Table 2). Within the 18S+28S phylogeny, A. limopsoides is placed basal to A. nitens with >0.95 BPP. Within the 18S phylogeny, Adacnarca and A. nitens form an unresolved polytomy with other Philobrya taxa (Fig. 5). Within the 28S phylogeny, A. nitens is a strongly supported monophyletic group (0.99 BPP, Fig. 6), but the placement of A. limopsoides is more basal within the Philobryidae, suggesting a polyphyletic Adacnarca. Divergence time analysis reveals rate variation across Adacnarca, particularly on the A. limopsoides branch, which has an elevated mutation rate relative to other philobryids. The long branch subtending this taxon likely explains the instability of this taxon across the 28S phylogenetic and divergence time analyses.


The evolutionary origins of the southern ocean Philobryid bivalves: hidden biodiversity, ancient persistence.

Jackson JA, Linse K, Whittle R, Griffiths HJ - PLoS ONE (2015)

Molecular phylogeny of 28S.Node values show Bayesian posterior probabilities (as %) and maximum likelihood bootstrap support respectively. Coloured bars show species units identified using ABGD and GMYC.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4390230&req=5

pone.0121198.g006: Molecular phylogeny of 28S.Node values show Bayesian posterior probabilities (as %) and maximum likelihood bootstrap support respectively. Coloured bars show species units identified using ABGD and GMYC.
Mentions: The monophyly of this genus is strongly supported by the 18S+28S dataset only (0.98 BPP) and by SH testing of both gene datasets (Table 2). Within the 18S+28S phylogeny, A. limopsoides is placed basal to A. nitens with >0.95 BPP. Within the 18S phylogeny, Adacnarca and A. nitens form an unresolved polytomy with other Philobrya taxa (Fig. 5). Within the 28S phylogeny, A. nitens is a strongly supported monophyletic group (0.99 BPP, Fig. 6), but the placement of A. limopsoides is more basal within the Philobryidae, suggesting a polyphyletic Adacnarca. Divergence time analysis reveals rate variation across Adacnarca, particularly on the A. limopsoides branch, which has an elevated mutation rate relative to other philobryids. The long branch subtending this taxon likely explains the instability of this taxon across the 28S phylogenetic and divergence time analyses.

Bottom Line: The A. nitens species complex is identified as at least seven morpho-species through morphological and genetic analysis of taxon clustering.Phylogenetic analyses resolve Philobryidae as a strongly supported monophyletic clade and sister taxon to the Limopsidae, as anticipated by their classification into the superfamily Limopsoidea.Bayesian relaxed clock analyses of divergence times suggest that genus Adacnarca radiated in the Southern Ocean from the Early Paleogene, while P. sublaevis and P. wandelensis clades radiated in the late Miocene, following the formation of the Antarctic Circumpolar Current.

View Article: PubMed Central - PubMed

Affiliation: British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 0ET, United Kingdom.

ABSTRACT
Philobryids (Bivalvia: Arcoida) are one of the most speciose marine bivalve families in the Southern Ocean and are common throughout the Southern Hemisphere. Considering this diversity and their brooding reproductive mode (limiting long-distance dispersal), this family may have been present in the Southern Ocean since its inception. However Philobrya and Adacnarca appear only in the Quaternary fossil record of the Antarctic, suggesting a much more recent incursion. Molecular dating provides an independent means of measuring the time of origin and radiation of this poorly known group. Here we present the first combined molecular and morphological investigation of the Philobryidae in the Southern Ocean. Two nuclear loci (18S and 28S) were amplified from 35 Southern Ocean Adacnarca and Philobrya specimens, with a combined sequence length of 2,282 base pairs (bp). Adacnarca specimens (A. nitens and A. limopsoides) were resolved as a strongly supported monophyletic group. Genus Philobrya fell into two strongly supported groups ('sublaevis' and 'magellanica/wandelensis'), paraphyletic with Adacnarca. The A. nitens species complex is identified as at least seven morpho-species through morphological and genetic analysis of taxon clustering. Phylogenetic analyses resolve Philobryidae as a strongly supported monophyletic clade and sister taxon to the Limopsidae, as anticipated by their classification into the superfamily Limopsoidea. Bayesian relaxed clock analyses of divergence times suggest that genus Adacnarca radiated in the Southern Ocean from the Early Paleogene, while P. sublaevis and P. wandelensis clades radiated in the late Miocene, following the formation of the Antarctic Circumpolar Current.

No MeSH data available.