Molecular phylogeny of large miliolid foraminifera - University of ...

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68M. Holzmann et al. / Marine Micropaleontology 43 2001) 57±74in the NJtree Fig. 2). Branching positions within theArchaiasinae change in the MP tree Fig. 3): Laevipeneroplissp. keeps its basal position and Archaiasangulatus and Androsina lucasi form a group bootstrapvalue of 73%), but the phylogenetic relationshipsbetween the remaining archaiasine species arenot resolved. Furthermore, Parasorites does notappear at the base of the Soritinae, but builds a sistergroup to the Amphisorus/Marginopora kudakajimaensisand Sorites/Marginopora vertebralis clade bootstrapvalue of 60%).To improve the resolution of the relationshipswithin the Soritinae, 15 additional partial SSUrDNA sequences of Soritinae have been obtained.The examined fragment prooves to be well suited toinvestigate intrageneric relationships in ForaminiferaDe Vargas et al., 1999; Pawlowski, 2000).Additional informative sites were gained by excludingmore distantly related groups of Soritacea fromthe analysis. A total of 27 sequences, includingParasorites as an outgroup has been analysed byusing NJmethod Fig. 4). The result con®rms thedivision of Soritinae in two distinctive clades as itwas already suggested by the analysis of completeSSU rDNA sequences. One clade is composed ofAmphisorus hemprichii and Marginopora cf. kudakajimaensis,as well as two specimens of SoritesSorites sp_k and Sorites sp._l). The second cladecomprises the remaining Sorites specimens specimensa±j) and Marginopora vertebralis, the latterone forming a monophyletic group, supported by99±100% bootstrap value Fig. 4). One sequenceof Sorites Sorites orbiculus_h) branches at thebase of the Sorites/Marginopora clade. Analyseswith ML and MP method trees not shown) yieldcongruent results. Changes in the branching positionin the latter two trees concern S. orbiculus h) whichbranches at the base of the Sorites clade containingthe specimens a±j.4. Discussion4.1. Peneroplidae are the ancestors of SoritidaeThe general structure of the molecular trees Figs.1±3) is congruent with the classical, morphologybasedphylogeny of Soritacea where Peneroplidaeappear as the basal group Hofker, 1953; Haynes,1981). Our molecular data are con®rmed by the fossilrecord, as the emergence of the ®rst Peneroplidaepredates by far the divergence of Soritidae, amongwhich the earliest fossil archaiasines are reportedfrom the Middle Eocene Smout and Eames, 1958)and the earliest soritines from the Miocene Haynes,1981).The monophyly of Peneroplidae in our moleculartree is unquestionable 100% bootstrap value),whereas the relationships between other Soritaceaare less clear. High bootstrap support 96±100%)exists for the clade that groups archaisines andsoritines together, but the associations within thisclade are less resolved. In view of our moleculardata, it seems accurate to divide the Soritacea intwo families, Peneroplidae and Soritidae, and tofurther subdivide the Soritidae in two subfamilies,Archaiasinae and Soritinae, as already proposed byGudmundsson 1994).4.2. Laevipeneroplis is an archaiasine genusArchaiasinae form a monophyletic cluster that alsocomprises Laevipeneroplis Fig. 1). Although mostauthors recognize archaiasines as a separate taxon offamily or subfamily rank Seiglie et al., 1976;Loeblich and Tappan, 1988; Hallock and Peebles,1993), the systematic position of Laevipeneroplishas remained controversial. Based on different externaland internal morphological characters, Laevipeneroplisis placed by some authors among thePeneroplidae Levy, 1977, Crapon de Caprona d'Ersu,1983; Leutenegger, 1984; Hallock, 1999), whereasothers Seiglie et al., 1976) include it in the Archaiasinae.Gudmundsson 1994) splits the genus Laevipeneroplisbecause of some morphological differencespresence or absence of arciform growth mode andinterior skeleton) and puts L. proteus at the base ofthe Archaiasinae, whereas L. bradyi is placed at thebase of soritids.Our molecular analyses indicate that all extantspecies of Laevipeneroplis are members of thesubfamily Archaiasinae. The genus itself, however,is not well de®ned. The three species, that havebeen examined in this study branch separately fromeach other. One of them, Laevipeneroplis sp. thatoriginates from the Western Paci®c, appears as a sister
M. Holzmann et al. / Marine Micropaleontology 43 2001) 57±74 69taxa to all Caribbean Archaiasinae Figs. 1±3). Twoother species, Laevipeneroplis bradyi and Laevipeneroplisproteus, are the respective sister taxa of theclades Cyclorbiculina compressa 1 Broeckina andArchaias angulatus 1 Archaias lukasi Fig. 1), buttheir branching position within the Archaiasinaedoes not remain stable Figs. 2 and 3). The basal positionof Laevipeneroplis sp. is in agreement withmorphological studies carried out by Seiglie et al.1976) who proposed L. proteus or a close relativeas an ancestor of the Archaiasinae.The close connection between Archaias angulatusand A. lucasi, as suggested by our molecular dataFigs. 1±3) was already pointed out by Gudmundsson1994), although the author groups both speciestogether with Cyclorbiculina compressa because ofsome homologies concerning their internal and externaltest morphology. On the basis of the present moleculardata, the relationships within the archaiasinesubfamily cannot be fully resolved and further molecularstudies are required to elucidate this problem.The monophyly of Caribbean Archaiasinae ismoderately well supported by our molecular dataFigs. 1±3). The presence of Paci®c Laevipeneroplissp. at the base of this clade Figs. 1±3) would indicatethat the origin of recent Archaiasinae lies in the Paci-®c or in the former Tethys region. Extant Archaiasinaeare predominantely found in the Caribbean withthe exception of Laevipeneroplis in the Paci®c Chengand Zheng, 1978; Hallock and Peebles, 1993;Hallock, 1999) and Mediterranean Leutenegger,1984; Cimerman and Langer, 1991; Langer andHottinger, 2000). Fossil archaiasines are knownfrom the Tethys and the Paci®c, as well as from theCaribbean region Smout and Eames, 1958; Adams,1976; Seiglie et al., 1976; Pringgoprawiro et al.,1998). It is possible that Archaiasinae originated inthe Indo-Paci®c and migrated later to the westernAtlantic. The carbonate shelves and platforms ofthe Caribbean are generally distinguished by intermediatenutrient ¯uxes as a result of their proximityto continental runoff and coastal ortopographic upwelling Hallock, 1988a; Hallocket al., 1993). The proliferation of Archaiasinaein the Caribbean Sea might be explained by thepresence of suitable environments, whereas therelative scarcity of appropriate ecological conditionsin the Paci®c might be a reason that recentarchaiasine taxa failed to diversify in this regionHallock, 1988a,b, 1999).4.3. Parasorites appears as a sister taxa to theSoritinaeAccording to our molecular data Figs. 1±3), thesubfamily Soritinae forms a monophyletic groupbootstrap value of 60±70%), including Parasoritesas a sister clade. Whereas the soritine genera Sorites,Amphisorus and Marginopora are distinguished bydino¯agellate symbionts, Parasorites possesses chlorophyteendosymbionts. The taxonomic position of thelatter genus is highly controversial. Similar forms thatare distinguished by cyclic growth and chambersdivided by rudimentary partitions, exist in the CaribbeanSea as well as in the Paci®c and were united bysome authors under a single species Hofker, 1952;Gudmundsson, 1994), whereas others stated thatCarribean and Paci®c forms belong to two differentspecies Levy, 1977; Crapon de Caprona d'Ersu,1985).Parasorites was ®rst described by Seiglie et al.1976), based on Caribbean material. Its type speciesis Praesorites orbitolitoides, which was originallydescribed by Hofker 1930) from Paci®c and Caribbeanmaterial. Caribbean forms that are akin toHofker, 1930 P. orbitolitoides were included intothe genus Broeckina by Levy 1977) and Crapon deCaprona d'Ersu 1985). According to Levy 1977)Broeckina only occurs in the Carribean Sea and isoften confused with P. orbitolitoides Hofker, 1930).Similar forms from the Paci®c were identi®ed asParasorites orbitolitoides by Hohenegger 1994) andHohenegger et al. 1999), and described as Soritesorbitolitoides type species: P. orbitolitoides, Hofker,1930) by Lehmann 1961). Gudmundsson 1994)described similar forms from the Caribbean and thePaci®c as S. orbitolitoides and regarded Broeckinaand Praesorites as synonyms of the former species.Specimens of Parasorites examined in the presentwork correspond in their external features to P. orbitolitoidesHohenegger 1994, Hohenegger et al.,1999) and S. orbitolitoides Lehmann, 1961). Theexamined specimen of Broeckina corresponds in itsexternal features to Broeckina orbitolitoides Levy,1977, Hallock and Peebles, 1993).Our molecular data are in agreement with Levy
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