Phylogeography of Ophryotrocha labronica (Polychaeta, Dorvilleidae) along the Italian coasts

Abstract

Species of the genus Ophryotrocha are a well‐studied group of organisms but, despite the relatively large body of biological studies, little is known about their intra‐specific patterns of genetic diversity. In the present study, we analysed the patterns of genetic variation in samples of Ophryotrocha labronica (Polychaeta, Dorvilleidae) collected along the Italian coasts within three regions with different thermal regimes: the Northern Adriatic Sea (NAS), the Ligurian Sea (LS), and the South/Southeast Sicilian Sea (SS). A partial sequence of the cytochrome c oxidase subunit I (COI) gene was used as a genetic marker. An analysis of molecular variance (AMOVA) showed significant genetic differentiation between the NAS and the other regions. Conversely, little or no genetic structuring was found between the LS and the SS or amongst locations within a given region. A Bayesian phylogenetic tree and a median‐joining network provided evidence for the occurrence of two highly divergent genetic lineages characterized by a high average sequence divergence (17.2%, Kimura two‐parameter distance). The spatial patterns of genetic variation found in O. labronica may reflect the signature of past expansion events of the two genetic lineages. Although the high sequence divergence suggested that cryptic speciation within O. labronica may have occurred, other traits such as the absence of reproductive isolation, pattern of phenotypic variation and habitat specificity prompted us to regard the two groups as distinct COI lineages of O. labronica.

Cryptic species and colonization processes in Ophryotrocha (Annelida, Dorvilleidae) inhabiting vertebrate remains in the shallow‐water Mediterranean

“…ABGD additionally recovered other Ophryotrocha species included in the analyses as separate species, and separated as two different species the two lineages of O. labronica corresponding to the two haplogroups defined by Cossu et al . () including also the three individuals we collected in Blanes harbour ( O. labronica Wh‐Ha‐14_13‐15). Interestingly, these two O. labronica species inferred here do not cluster together with the original COI sequence available in NCBI for O. labronica () (Table ).…”

“…In this case, the two species inferred here corresponded to the two haplogroups identified in the study by Cossu et al . () and also include the three individuals of specimens collected in Blanes harbour ( O. labronica Wh‐Ha‐14_13‐15). As for ABGD analyses, these two O. labronica species inferred here do not cluster together with the original COI sequence available in NCBI for O. labronica () (Fig.…”

“…), thus indicating that these haplogroups are in fact two separate lineages of the species O. labronica (Cossu et al . ). However, given that no nuclear markers were sequenced for these haplogroups (neither for the haplogroups nor for the resulting ‘hybrids’ after cross‐breeding), we cannot dismiss the possibility that these two lineages in fact correspond to two different species whose reproductive prezygotic isolation is incomplete at least in in vitro conditions, as it has been reported for different species of echinoderms ( e.g .…”

“…In their recent study, Cossu et al . () demonstrated that O. labronica populations along the Italian coast can be in fact subdivided into two highly divergent haplogroups (average 17.2% K2P distance for COI ), which was suggested to be the result of allopatric divergence followed by secondary contact. Remarkably, cross‐breeding experiments showed that individuals from the two haplogroups were interfertile (Massamba‐N'Siala et al .…”

Can multi-generational exposure to ocean warming and acidification lead to the adaptation of life-history and physiology in a marine metazoan?

“…This study was conducted on the benthic marine polychaete Ophryotrocha labronica Bacci and La Greca 1961 (Polychaeta, Dorvilleidae), a patchily distributed global occupant of the biofouling community (Cossu et al, 2015). Sexual maturity is reached at 11-12 chaetigers in females and at 7-8 chaetigers in males (Lorenzi and Sella, 2013).…”