Discrete genetic boundaries of threeStreblospio(Spionidae, Annelida) species and the status ofS. shrubsolii

Abstract

Spionid polychaetes are a dominant component of benthic assemblages in marine and estuarine habitats and are important in assessing ecological function and integrity. Ecological and biogeographic studies rely upon the ability to distinguish between morphologically similar species, as well as knowledge of evolutionary relationships between species. Unfortunately, differentiating between congeneric species of spionids can be challenging thereby potentially creating mistakes in scientific investigations. For example Streblospio contains three recognized species (S. benedicti, S. shrubsolii, S. gynobranchiata) with few distinguishing morphological characters. Herein, we use Â500 bases of the mitochondrial cytochrome c oxidase subunit 1 gene (COI) to investigate the status of S. shrubsolii relative to other Streblospio. COI has previously been used to distinguish North American Streblospio benedicti and S. gynobranchiata. Results indicate all three Streblospio species are reciprocally monophyletic with S. shrubsolii basal to a well-supported S. benedicti/S. gynobranchiata clade.

Spionidae (Annelida: ‘Polychaeta’: Canalipalpata) from Lizard Island, Great Barrier Reef, Australia: the genera Malacoceros, Scolelepis, Spio, Microspio, and Spiophanes

“…Among the available species genetic distance was lowest to S. daphoinos Zhou, Ji & Li, 2009 but with 19.6% within the range (17.6%-30.6%) found between the other species of this genus. These values are comparable to interspecific distances previously reported within spionid genera (e.g., Blank & Bastrop 2009, Mahon et al 2009, Meißner & Blank 2009, Carr et al 2011. S. daphoinos has indeed been considered to be morphologically similar to S. kudenovi (Zhou et al 2009).…”

“…Sequencing of partial 16S failed as already before in another study on Spiophanes (Meißner & Blank 2009), most likely because the available universal 16S primers are not working in this genus. The analysis of the COI dataset including all available Spiophanes species revealed genetic distances that were within the previously reported range for this genus (15.0%-19.7%, Meißner & Blank 2009) and within other spionid genera (e.g., Blank & Bastrop 2009, Mahon et al 2009, Meißner & Blank 2009, Carr et al 2011). …”

Morphogenesis and phenotypic divergence in two developmental morphs of Streblospio benedicti (Annelida, Spionidae)

“…However, the low level of CO1 differentiation between members of the two morphs found in the present study is consistent with the hypothesis that members of the two morphs are conspecifics. Our results are consistent with previous CO1 data for members of the genus Streblospio (Schulze et al 2000;Mahon et al 2009). Mahon et al (2009) report CO1 p-distances from À0.44% to 2.6% within each of three described species of Streblospio, and distances of 15.5-22.5% between these species.…”

Dimorphic development in Streblospio benedicti: genetic analysis of morphological differences between larval types

“…benedicti evolved poecilogony from an ancestor with a single life-history strategy, most likely planktotrophy (Mahon et al, 2009). Lecithotrophy could have evolved through the accumulation of small-effect changes throughout the genome, but our results suggest that only one or a few genes (genomic regions) of large effect can account for major reduction in the length of larval chaetae.…”