Morphological and molecular concordance of Rhynchozoon clades (Bryozoa, Cheilostomata) from Alaska

• Published in: Invertebrate Biology
• Main Authors: Dick, Matthew H., Mawatari, Shunsuke F.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2005
• Subjects: Ketchikan; Alaska
• Online Access: http://dx.doi.org/10.1111/j.1744-7410.2005.00032.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1744-7410.2005.00032.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1744-7410.2005.00032.x

Abstract. Alpha‐level taxonomy in the bryozoan order Cheilostomata relies almost exclusively on hard‐part morphology. Geographical, ecophenotypic, and intracolony variation often make it difficult to distinguish intra‐ from interspecific variation and to recognize taxonomically informative characters. DNA sequences provide a source of data independent of morphology by which to gauge the relative reliability of various morphological characters for taxonomy. We present a case study involving a limited number of specimens of Rhynchozoon sp. from Ketchikan, Alaska to show the utility of DNA data in identifying genetic lineages for subsequent morphological analysis. The study illustrates that the use of genetic data need not involve massive, broad‐scale phylogenetic studies to address problems in invertebrate α‐level taxonomy. Phylogeny reconstruction with a 430‐bp fragment of the 16S mitochondrial ribosomal RNA gene showed two moderately diverged clades, here termed Rhynchozoon clades A and B, separated by an average genetic distance of 2.38% (K2P+Γ). Comparison of voucher specimens by scanning electron microscopy showed two congruent, morphologically distinct forms (forms A and B, respectively) distinguishable by a polythetic suite of characters including degree of frontal costation, range of spine number, number of beads on the primary orifice, number of areolar pores, and peri‐orificial sculpturing. Orifice shape and ovicell form proved not to be good diagnostic characters. The status of the two forms as biological species is unclear, although maintenance of distinct suites of morphological characters in the two mitochondrial lineages suggests they may be reproductively isolated from one another. For Rhynchozoon form B, which tends to have a highly costate frontal wall, we suggest a resurrection of the name Rhynchozoon tumulosum , which had been previously synonymized with R. rostratum . Rhynchozoon form A may be conspecific with “ Rhynchozoon sp. A” previously reported from Washington state.