^03 Marine Biology (2000) 137: 183-194 ® Spnnger-Verlag 2000 M. G. Harasevvych A. G. McArthur A molecular phylogeny of the Patellogastropoda (Mollusca: Gastropoda) Received: 5 February 1999 /Accepted: 16 May 2000 Abstract Phylogenetic analyses of partiaJ J8S rDNA formia" than between the Patellogastropoda and sequences from species representing all living families of Orthogastropoda. Partial 18S sequences support the the order Patellogastropoda, most other major gastro- inclusion of the family Neolepetopsidae within the su- pod groups (Cocculiniformia, Neritopsma, Vetigastro- perfamily Acmaeoidea, and refute its previously hy- poda, Caenogastropoda, Heterobranchia, but not pothesized position as sister group to the remaining Neomphalina), and two additional classes of the phylum living Patellogastropoda. This region of the Í8S rDNA Mollusca (Cephalopoda, Polyplacophora) confirm that gene diverges at widely differing rates, spanning an order Patellogastropoda comprises a robust clade with high of magnitude among patellogastropod lineages, and statistical support. The sequences are characterized by therefore does not provide meaningful resolution of the the presence of several insertions and deletions that are relationships among higher taxa of patellogastropods. unique to, and ubiquitous among, patellogastropods. Data from one or more genes that evolve more uni- However, this portion of the 18S gene is insufficiently formly and more rapidly than the ISSrDNA gene informative to provide robust support for the mono- (possibly one or more of the mitochondrial genes) seem phyly of Gastropoda, or to address the division of the more likely to be informative about relationships within Gastropoda into the subclasses Eogastropoda (= Patel- Patellogastropoda. logastropoda + hypothetical coiled ancestors) and Or- thogastropoda. These sequence data invariably group Patellogastropoda in a weakly supported clade with Introduction cocculiniform limpets, despite greater sequence divergences between Patellogasti'opoda and "Cocculini- The patellogastropod limpets are conspicuous in inter- tidal, rocky shore faunas, achieving greatest abundance and diversity in temperate climates. Most limpets live in Communicated by J. P. Grassle, New Brunswick shallow water and feed on algae and seagrasses, but some Supplementary material: Aligned partial sequences of the gastropod inhabit sunken wood at bathyal and abyssal depths 18S rDNA gene corresponding to positions 60-515 of the (Lindberg and Hedegaard 1996), and others have been IBS rRNA of Oiicliidellci ccllicci as reported by Winnepenninckx discovered at hydrothermal vents and sulfide seeps et al. (1994: Nautilus Suppl 2:p 101). Ambiguous base assignments (McLean 1990; Beck 1996). Because of their abundance are noted using lUPAC symbols. Dashes (-) represent gaps in- serted during alignment, question marks represent missing data, and diversity, limpets have been used in studies in nu- periods represent identity to the sequence of the chiton Acanllio- merous biological disciplines, including ecology, embry- pleiira japónica. Available in electronic form on Springer-Verlag's ology, sperm morphology, population genetics, and server imder http: link.springer.de/link/service/journals/00227. biogeography (e.g. Smith 1935; Abbott et al. 1968;Branch and Branch 1980; Hodgson 1996; Koufopanou et al. M. G. Harasewych (ÍBi) • A. G. JVJcArthur Department of Invertebrate Zoology, 1999). Due to their distinctive morphology and anatomi- National Museimi of Natural History, cal organization, patellogastropod limpets play a pivotal Smithsonian Institution, Washington, D.C. 20560-0118, USA role in the ongoing reassessment of the evolutionary his- e-mail: Harasewych a nmnh.si.edu tory of the molluscan class Gastropoda and the subphy- Fax: +1-202-3572343 lum Conchífera (e.g. Haszprunar 1988; Bändel and Geldmacher 1996; Ponder and Lindberg 1996, 1997; Sal- Present address: A. G. McArthui- vim-Plawen and Steiner 1996; Bändel 1997; Sasaki 1998). Marine Biological Laboratory, 7 MBL Street, Woods Hole, Limpets had been segregated from the coiled gas- Massachusetts 02543-1015, USA tropods by the earliest molluscan taxonomists on the 184 basis of their low, conical shells (e.g. Lister 1678; Bu- morphological characters, begun by GoUkov and Sta- onnani 1684; Linné 1758). During the gradual refine- robogatov (1975) and continued using cladistic princi- ment of gastropod classification in the nineteenth ples (e.g. Haszprunar 1988; Ponder and Lindberg 1996, century, systematists erected taxa such as Cyclobranchia 1997; Sasaki 1998), invariably place the Patellogastro- (Cuvier 1817) and Docoglossa (Troschel 1861) to en- poda as the basal clade within Gastropoda. So profound compass the patellogastropod limpets, while excluding are the morphological difli"erences between limpets and the various unrelated taxa with convergently derived, the remaming gastropods (summarized by Lindberg limpet-like shells (e.g. Fissurellidae, Calyptraeidae, Si- 1998a; Sasaki 1998) that the subclass Eogastropoda was phonariidae), usually on the criterion of the morphology proposed to segregate the Patellogastropoda, together of the radula. In the prevailing classifications of the time with their hypothesized, coiled ancestors, from the re- (e.g. Gray 1857; Fischer 1887; Pelseneer 1906), patello- maming gastropods, which were assigned to the subclass gastropod limpets were generally placed at the base of Orthogastropoda (Ponder and Lindberg 1996). Some taxa today included in the Gastropoda. In a significant authors (Termier and Termier 1968; Shileyko 1977) have departure from previous classifications, Thiele (1929) speculated that patellogastropods might not be gastro- proposed a new arrangement of the Gastropoda based pods, but rather were independently derived from on the paradigm that paired mantle cavity organs con- monoplacophorans. stitute the primitive condition. He regarded the patel- Evolutionary relationships within Patellogastropoda logastropod limpets to be closely related to the fissurellid have long been studied (e.g. Dall 1871, 1876; Fleure limpets and included both groups in his order Archae- 1904; Lindberg 1988, 1998a; Lindberg and Hedegaard ogastropoda. This arrangement has been accepted al- 1996; Sasaki 1998). While patellogastropods are readily most universally for over 50 years (e.g. Abbott 1974; sorted into groups (families superfamilies) on the basis Brusca and Brusca 1990; Ruppert and Barnes 1994). of highly concordant suites of shell ultrastructural, ra- Modern analyses of gastropod phylogeny based on dular, and anatomical characters, recent hypotheses of Fig. lA-D Morphology-based r- 1 nt cVt-i =PETOPSINA hypotheses of pateUogastropod PalGlIidae PATELLOIDEA m I'elationships. Nomenclature C-^^ifíi/flffr^ and taxon rank have, in some z 1 NACELLA 1 cases, been modified to facili- NEOLEPETOPSIDAE Nacellidae NACELLOIDEA tate cornparisons, la.\a listed in CEUANA upper case are represented in 1 EULEPETOPSIS this study. A McLean (1990: Neoíepelopsidae z Fi2. 1). B Lmdbera (1998a; O > m Fig. 15.31). C Dall (1876: 1 Propilidium o I• "D s i- Fig. 2): follows Lindberg Lepetidae > 1 / FPFTA m (1998b) for modern equivalents m O > o of Dall's (1871, 1876) taxa. D Z 1 1 LOTTIA m Sasaki (1998: Fig. 104) > Loltüdae > PATELLOIDA ACMAFOinPA u 1 ACMAEA Acmaeidae • Peclinodonla A McLEAN, 1990 B LINDBERG, 1998 LE PETA - Limalepeta | Lepetidae Lepetidae t Propiüdium _ 'PATELLA I Patellidae ACMAEA Acmaeidae LOTTIA - CELLANA I Nacellidae 41 PATELLOIDA Lottüdae - Peclinodonla I Acmaeidae Scurria PATELLA Scutellastra Patellidae - Nipponacmaea Lotliidae Hflrinn CELLANA ~~ Nacellidae - Erg i nus NACELLA C DALL, 1876 D SASAKI, 1998 185 phylogenetic relationships among these groups differ significantly (Fig. IB, D), despite their being based on Materials and methods broad suites of anatomical characters and cladistic methodology. Most notably, a distinctive, monophyletic Table 1 lists the laxa used in the present study, their collection locality, preservation history, tissue extracted, and voucher speci- lineage of limpets discovered at hydrothermal vents and men information. N4ost taxa were collected specifically for this hydrocarbon seeps was initially thought to be interme- study, frozen while living, and maintained a( -80 °C until DNA diate between patellogastropods and the remaining was extracted. Freshly collected specimens of Nocel/a iiwgellonica gastropods (Haszprunar 1988: Fig. 5, "Hot-Vent-C"), were fixed in 95% etlianol prior to shipping. Data for Lepetci caeca and Para/epeiopsis floriclensis were obtained from museum speci- but subsequently was included within the patellogas- mens that liad been fixed in formalin and stored in 70% ethanol. tropod clade as additional data became available DNA was extracted from buccal muscles or entire individuals fol- (McLean 1990; Ponder and Lind berg 1996, 1997). lowing the protocol of Harasewych et al. (1997). If this did not McLean (1990) proposed the family Neolepetopsidae for provide workable template for the polymerase chain reaction (PCR), as was the case for most formalin-preserved specimens, these limpets based on their articulating radular teeth, DNA was then extracted using the protocol of Chase et al. (f998). and grouped them with extinct. Paleozoic limpets in the Newly designed oligonucleotide primers used for PCR amplifica- suborder Lepetopsina. McLean regarded the Lepetop- tion of approximately 450 bp of the 5' end of the 18S rDNA sina as the sister taxon of the remaining patellogastro- molecule