Naming species with no morphological indicators: species status of Galeolaria caespitosa (Annelida:Serpulidae) inferred from nuclear and mitochondrial gene sequences and morphology

Abstract

Galeolaria caespitosa Lamarck, 1818 is an endemic, gregarious serpulid annelid, ubiquitous along the intertidal zone of southern Australia, occurring from Queensland to Western Australia. We sampled specimens across this range and utilised morphological features and sequences of mitochondrial (cytochrome-b) and nuclear (ITS2) markers to assess the taxonomic status of this morphospecies. No taxonomically significant morphological differences were observed across the range of G. caespitosa. However, the molecular data revealed the existence of the following two well supported clades that were also geographically concordant for the two markers: an eastern clade, consisting of New South Wales and southern Queensland samples, and a south-western group that encompassed samples from the rest of its range. The minimum pairwise distance between members of the two groups was more than 24% for cytochrome-b, with a maximum of 1% within-group variation. In addition, analysis of molecular variation showed a high proportion (97%) of the total variation distributed among the two groups, indicative of long-term isolation of the two clades. These results suggest that G. caespitosa comprises at least two cryptic species. Here, we discuss the merits of naming new Galeolaria species, given there were no consistent morphological differences detectable and the absence of details on the type locality for G. caespitosa. We conclude that a new species of Galeolaria is warranted and describe it here as G. gemineoa.

Reef formation versus solitariness in two New Zealand serpulids does not involve cryptic species

“…The Australian G. hystrix differs from our New Zealand clade by an average of 26% for the same gene. We note also that G. caespitosa and G. geminoea are both gregarious whereas the Australian G. hystrix is generally solitary (Halt et al 2009). …”

“…In Australia, sequencing has split morphologically indistinguishable 'G. caespitosa' into an eastern clade (renamed G. geminoea) and a southwestern clade (real G. caespitosa) (Halt et al 2009), whose cytochrome b sequences differ by >19%. The Australian G. hystrix differs from our New Zealand clade by an average of 26% for the same gene.…”

“…Each of these markers evolves at a different rate and thus provides a different level of resolution. Approximately 1800 bp of 18S was amplified using primers TimA (Norén & Jondelius 1999) and 18s2R (Kupri yanova et al 2006), ~300 bp of histone H3 using H3aF and H3aR (Colgan et al 1998) and ~350 bp of cytochrome b using Cytb424F and cobr825 (Halt et al 2009). All reactions were carried out in 20 µl volumes and contained 0.5 µM of each primer and 0.5 U MyTaq Red DNA polymerase (Bioline).…”

“…the aggregating population is a different cryptic species from the solitary population in each of 2 common species. We note that the related Australian nominal taxon, G. caespitosa, has recently been found to consist of 2 morphologically indistinguishable but genetically distant species (Halt et al 2009). …”

Australian Tropical Marine Micromolluscs: An Overwhelming Bias

“…When the microscopic lifestyle has led to real absence of characters (not just poorly studied), and cryptic radiations, using a DNA taxonomy has offered some promise. This method has been used for cryptic species in general [88,89] and for cryptic micromolluscs [90]. All robust works using DNA characters for species delimitation must also incorporate evidence that the species are truly cryptic and demonstrate a lack of morphological characters before going down that path.…”