TY - JOUR
T1 - Ascidian mitogenomics
T2 - Comparison of evolutionary rates in closely related taxa provides evidence of ongoing speciation events
AU - Griggio, Francesca
AU - Voskoboynik, Ayelet
AU - Iannelli, Fabio
AU - Justy, Fabienne
AU - Tilak, Marie Ka
AU - Xavier, Turon
AU - Pesole, Graziano
AU - Douzery, Emmanuel J P
AU - Mastrototaro, Francesco
AU - Gissi, Carmela
PY - 2014
Y1 - 2014
N2 - Ascidians are a fascinating group of filter-feeding marine chordates characterized by rapid evolution of both sequences and structure of their nuclear and mitochondrial genomes. Moreover, they include several model organisms used to investigate complex biological processes in chordates. To study the evolutionary dynamics of ascidians at short phylogenetic distances, we sequenced 13 new mitogenomes and analyzed them, together with 15 other available mitogenomes, using a novel approach involving detailed whole mitogenome comparisons of conspecific and congeneric pairs. The evolutionary rate was quite homogeneous at both intraspecific and congeneric level, and the lowest congeneric rates were found in cryptic (morphologically undistinguishable) and inmorphologically very similar species pairs. Moreover, congeneric nonsynonymous rates (dN) were up to two orders of magnitude higher than in intraspecies pairs. Overall, a clear-cut gap sets apart conspecific from congeneric pairs. These evolutionary peculiarities allowed easily identifying an extraordinary intraspecific variability in the model ascidian Botryllus schlosseri, where most pairs show a dN value between that observed at intraspecies and congeneric level, yet consistently lower than that of the Ciona intestinalis cryptic species pair. These data suggest ongoing speciation events producing genetically distinct B. schlosseri entities. Remarkably, these ongoing speciation events were undetectable by the cox1 barcode fragment, demonstrating that, at low phylogenetic distances, the whole mitogenomehas a higher resolving power than cox1. Our study shows that whole-mito genome comparative analyses, performedon a suitable sample of congeneric and intraspecies pairs, may allow detecting not only cryptic species but also ongoing speciation events.
AB - Ascidians are a fascinating group of filter-feeding marine chordates characterized by rapid evolution of both sequences and structure of their nuclear and mitochondrial genomes. Moreover, they include several model organisms used to investigate complex biological processes in chordates. To study the evolutionary dynamics of ascidians at short phylogenetic distances, we sequenced 13 new mitogenomes and analyzed them, together with 15 other available mitogenomes, using a novel approach involving detailed whole mitogenome comparisons of conspecific and congeneric pairs. The evolutionary rate was quite homogeneous at both intraspecific and congeneric level, and the lowest congeneric rates were found in cryptic (morphologically undistinguishable) and inmorphologically very similar species pairs. Moreover, congeneric nonsynonymous rates (dN) were up to two orders of magnitude higher than in intraspecies pairs. Overall, a clear-cut gap sets apart conspecific from congeneric pairs. These evolutionary peculiarities allowed easily identifying an extraordinary intraspecific variability in the model ascidian Botryllus schlosseri, where most pairs show a dN value between that observed at intraspecies and congeneric level, yet consistently lower than that of the Ciona intestinalis cryptic species pair. These data suggest ongoing speciation events producing genetically distinct B. schlosseri entities. Remarkably, these ongoing speciation events were undetectable by the cox1 barcode fragment, demonstrating that, at low phylogenetic distances, the whole mitogenomehas a higher resolving power than cox1. Our study shows that whole-mito genome comparative analyses, performedon a suitable sample of congeneric and intraspecies pairs, may allow detecting not only cryptic species but also ongoing speciation events.
KW - Ascidian
KW - Evolutionary rate
KW - Mitochondrial genome
KW - Species identification
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UR - http://www.scopus.com/inward/citedby.url?scp=84902993601&partnerID=8YFLogxK
U2 - 10.1093/gbe/evu041
DO - 10.1093/gbe/evu041
M3 - Article
C2 - 24572017
AN - SCOPUS:84902993601
VL - 6
SP - 591
EP - 605
JO - Genome Biology and Evolution
JF - Genome Biology and Evolution
SN - 1759-6653
IS - 3
ER -