The position of the Haplotaxidae in the evolution of oligochaete annelids

The Haplotaxidae have all the characteristics to support the hypothesis that they are the living descendents of the stem forms from which all of the Oligochaeta Clitellata (Orders Lumbriculida, Haplotaxida, Lumbricida, Tubificida) can be derived. The Aphanoneura are distinct from the Clitellata and are raised to a separate Class. There is no evidence to support the view that the elaborate setae of many Tubificida are derived from a polychaete ancestry; both are held to be independent modifications to aquatic life derived from a simple burrowing protoannelid with lumbricine setae.     

A phenetic and cladistic study of spermatozoal ultrastructure in the Oligochaeta (Annelids)

Spermatozoal ultrastructure of nine oligochaete families has been examined for congruence with phylogenetic and taxonomic systems for the Oligochaeta based on general morphology, particularly the holomorphological hennigian analysis of Jamieson (1978a, 1980, 1983). Estimation of congruence has been made following phenetic and cladistic (phylogenetic) analysis. Correspondence, in phenograms and phylograms, of sperm types with taxonomic and phylogenetic groupings previously recognized is generally good. Departure from this rule in the similarity of the phreodrilid sperm to that of the Lumbricina suggests a corresponding alteration of fertilization biology in the phreodrilids. The results indicate that the Haplotaxidae lie at the base of the opisthopores though they do not unequivocally contraindicate acceptance of a Haplotaxis like form as a stem form of the Haplotaxida (opisthopores and Haplotaxidae) and Tubificida. An even more basal position for prosopores, now represented by the Lumbriculida, cannot yet be dismissed.     

Spermatozoal Ultrastructure: Evolution and Congruence with a Holomorphological Phylogeny of the Oligochaeta (Annelida)

Plesiomorph characters for the oligochaete spermatozoon are proposed. The chief trends from these plesiomorphies have been elongation of the acrosome and its tube; withdrawal of the primary acrosome vesicle and the axial rod into the acrosome tube and development of a capitulum; development of connectives from the secondary tube to the axial rod (though there is some possibility that the reverse, absence of connectives, is plesiomorph); detorting and shortening of the midpiece (or possibly, again, the reverse) with an increase in numbers of mitochrondria from the plesiomorph four to eight; modification of the base of the tube to form a hen of variable form; and, in one line (lumbricids) flattening of the tip of the nucleus and correspondingly of the limen. Sperm ultrastructure, examined for 9 oligochaete families, corresponds well with taxonomic and phylogenetic groupings recently recognized by the author. However, convergent similarity of the phreodrilid sperm to that of the Lumbricina suggests a corresponding alteration of fertilization biology in the phreodrilids. The results indicate that the Haplotaxidae lie at the base of the opisthopores, though they do not unequivocally contraindicate acceptance of a Haplotaxis-like form as a stem form of the Haplotaxida (opisthopores and Haplotaxidae) and Tubificida. An even more basal position for prosopores, now represented by the Lumbriculida, cannot yet be dismissed.     

ON THE PHYLOGENY AND HIGHER CLASSIFICATION OF THE OLIGOCHAETA

Abstract— The 50 oligochaete taxa representing all families of “opisthoporous” oligochaetes (Aliuroididae, earthworms and aquatic “megadriles”) together with two representatives of the Haplotaxidac and three examples of “microdiles” were subjected to cladistic analysis using the PAUP program. Sixty-eight characters used in the analyses were derived from a comprehensive range of somatic and genital systems. The optimal result, in terms of maximal number of characters and taxa and of parsimony, produced two trees (consistency index 0.362) differing only in the placement of the monotypic clade for the family Lumbriculidae. From a line originating from the presumed octogonadial ancestor, the following branches were derived, in sequence from the basal to most derived (new taxa asterisked): subclass Randiellata* (order Randiellida*, Randiellidae); subclass Tubificata* (order Tubificida, Tubincidae, Naididae computed and others not computed); subclass Lumbriculata* (order Lumbriculida, Lumbriculidae); superorder Haplotaxidea* (order Haplotaxida, Haplotaxidae); order Moniligastrida (Moniligastridae); suborder Alluroidina (Aliuroididae and Syngenodrilidae); cohort Aquamegadrili* (with, in succession, superfamilice Sparganophiloidea, Sparganophilidae; Biwadriloidea, Biwadrilidac, and Almoidca—Lutodrilidac and Almidae, including Criodrilus); superfamily Eudriloidea*, superfamily Lumbricoidea and, as the adelphotaxon of the latter, the superfamily Megascolecoidea. Intermediate nodes were given the following names, with the adelpholaxon through to the Megascolecoidea, M, in parentheses: subclass Diplotesticulata (Haplotaxidea—M); superorder Metagynopohora* (Moniligastrida—M); order Opisthopora (Alluroidina M); suborder Crassiclitellata* (Aquamegadrili — M); cohort Terrimegadrili* (Ocnerodriloidea M); unnamed (Eudriloidea M); unnamed (Lumbricoidea and Megascolecoidea). Recognition of the Randiellata, which alone were added intuitively and not computed, and the position of the Lumbriculata, are tentative. Location of the Lumbricoidea as the adelphotaxon of a restricted Megascoecloidea is heuristic, but the alternative depiction of lumbricoids in some analyses, as the adelphotaxon of an ocnerodrilid-eudrilid-megascolecoid clade (the conventional Megascolecoidea s. lat.), is not conclusively dismissed.     

18S rDNA phylogeny of Clitellata (Annelida)

The phylogeny of Clitellata was analysed using 18S rDNA sequences of a selection of species representing Hirudinida, Acanthobdellida, Branchiobdellida and 10 oligochaetous families. Eleven new 18S sequences of Capilloventridae (one), Haplotaxidae (one), Propappidae (one), Enchytraeidae (two), Lumbricidae (one), Almidae (one), Megascolecidae (two), Lumbriculidae (one), and Phreodrilidae (one) are reported and aligned together with corresponding sequences of 28 previously studied clitellate taxa. Twelve polychaete species were used as an outgroup. The analysis supports an earlier hypothesis based on morphological features that Capilloventridae represents a basal clade of Clitellata; in the 18S tree it shows a sister-group relationship to all other clitellates. The remaining clitellate taxa form a basal dichotomy, one clade containing Tubificidae (including the former 'Naididae'), Phreodrilidae, Haplotaxidae, and Propappidae, the other clade with two subgroups: (1) Lumbriculidae together with all leech-like taxa (Acanthobdellida, Branchiobdellida and Hirudinida), and (2) Enchytraeidae together with a monophyletic group of all earthworms included in the study (Lumbricidae, Almidae and Megascolecidae). These earthworms are members of the taxon Crassiclitellata, the monophyly of which is thus supported by the data. The tree also shows support for the hypothesis that the first clitellates were aquatic. The position of the single species representing Haplotaxidae is not as basal as could have been expected from earlier morphology-based conclusions about the ancestral status of this family. However, if Haplotaxidae is indeed a paraphyletic assemblage of relict taxa, a higher number of representatives will be needed to resolve its exact relationships with the other clitellates.     

Phylogenetic analysis of the aquatic Oligochaeta under the principle of parsimony

Phylogenetic relationships between five subfamilies of Tubificidae and ten other families of microdrile oligochaetes were estimated by a Wanger parsimony analysis using PAUP (Phylogenetic Analysis Using Parsimony, by D. L. Swofford). As the apomorph character state is ambiguous for some characters, different assumptions of directionality as well as deletions of some characters are tested in a number of analyses. A general pattern is evident from the study; (1) the majority of the aquatic families are members of a large monophyletic group (the order Tubificida in a somewhat restricted sense) defined by the shared possession of atria (generally with well developed external prostate glands), but the family Tubificidae is paraphyletic within this group; (2) the Enchytraeidae appear to form a second group (the Enchytraeida) together with the exclusively marine Capilloventridae and Randiellidae, all three families characterized by the anterior location of the spermathecae; (3) the Haplotaxidae are a plesiomorph family, which stands out as a branch of its own and constitutes the ancestral part of a group comprising also all the megadriles (the Haplotaxida). However, monophyly of the Haplotaxida is likely only if the haplotaxid octogonadial condition is assumed to be derived from the tetragonadial condition characterizing most microdriles, a situation not envisaged by previous authors. The implications of the parsimony method are briefly discussed.     

An osteology‐based appraisal of the phylogeny and evolution of kangaroos and wallabies (Macropodidae: Marsupialia)

Macropodids are the most diverse group of marsupial herbivores ever to have evolved. They have been the subject of more phylogenetic studies than any other marsupial family, yet relationships of several key clades remain uncertain. Two important problem areas have been the position of the merrnine (Lagostrophus fasciatus) and the phylogenetic proximity of tree‐kangaroos and rock‐wallabies. Our osteological analysis revealed strong support for a plesiomorphic clade ( Lagostrophinae subfam. nov. ) containing Lagostrophus and Troposodon, which is likely to have originated in the early Miocene. The extinct short‐faced kangaroos (Sthenurinae) emerged in the middle Miocene as the sister lineage to a clade containing all other living kangaroos and wallabies (Macropodinae). New Guinea forest wallabies ( Dorcopsini trib. nov. ) are the most plesiomorphic macropodines; the other two main lineages include tree‐kangaroos and rock‐wallabies (Dendrolagini), and ‘true’ kangaroos and wallabies (Macropodini). These phylogenetic outcomes are broadly consistent with the results of recent molecular studies, although conflicts remain over the relative positions of some macropodins (e.g. Setonix, Onychogalea, and Wallabia). Given the presence of derived dendrolagins and macropodins in early Pliocene localities, it is probable that most macropodine genera originated in the late Miocene. Key functional–adaptive trajectories within the craniodental and locomotory systems of the dominant macropodid lineages represent varying responses to the spread of drier, open habitats following the Miocene Climatic Optimum. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 159 , 954–987.     

Taxic Revisions

Parsimony analysis provides a straightforward way of assessing homology on a tree: a state shared by two terminals comprises homologous similarity if optimization attributes that state to all the stem species lying between those terminals. Three-taxon statements (3ts), although seemingly "exact" in that each either fits a tree or does not, do not provide a satisfactory assessment of homology, because that assessment can be internally contradictory and because 3ts systematically exclude homologous resemblance in reversed states. Modified 3ts analysis (m3ta), a method in which both plesiomorphic and apomorphic states of "paired homologue" (PH) characters (those other than presence/absence data) are regarded as "informative" (able to distinguish groups), can (obviously) group by symplesiomorphy and so form paraphyletic groups unless data are clocklike enough. Patterson's pattern analysis (ppa) has the same shortcoming, to which it adds the drawback that only characters fitting the tree perfectly are used, a restriction that can easily lead to discarding most of the structure in the data. Revised m3ta (rm3ta), a method in which plesiomorphic states are not taken as informative, can also form paraphyletic groups, because it cannot apply reversals as apomorphies. The idea that knowledge of phylogeny has been derived from classifications does not imply that nonevolutionary methods should be employed for classification, but instead means that systematic methods must be logically capable of phylogenetic interpretation. Neither m3ta nor rm3ta satisfies that requirement because of their contradictory assessments of homology.     

Marine Oligochaeta from the Koster Area, West Coast of Sweden, with Descriptions of Two New Enchytraeid Species

A total of 28 species of marine Oligochaeta (belonging to the families Naididae, Tubificidae and Enchytraeidae) are reported from eulittoral and sublittoral sediment samples taken in the Koster area on the Swedish West Coast. Lumbricillus algensis sp.n. and Grania ovitheca sp.n. are described and their morphological and taxonomical relations to other enchytraeids are discussed. L. algensis is characterized mainly by its spermathecae, which project into segment VI, and by its very large penial bulbs. G. ovitheca possesses no dorsal setae, the ventral setae being present posterior to the clitellum only, and its spermathecae consist of a narrow duct and a large egg-shaped to oval ampulla, filling most of the coelom of segment V. Four sublittoral species, Limnodriloides barnardi (Tubificidae), Lumbricillus semifuscus, Marionina sublitoralis and Grania roscoffensis (all Enchytraeidae) are reported as new to the Swedish fauna.     

Ovary organization and oogenesis in two species of Lumbriculida (Annelida,Clitellata)

The aim of the present study is to describe the organization of the ovary and mode of oogenesis at the ultrastructural level in two representatives of Lumbriculida – Lumbriculus variegatus and Stylodrilus heringianus. In both species studied, the ovaries are small and conically shaped structures that are attached to the intersegmental septum via a thin ligament. The ovaries are composed of germline cysts formed by germ cells interconnected by stable cytoplasmic bridges. As a rule, the cyst center is occupied by a poorly developed anuclear cytoplasmic mass, termed a cytophore, whereas the germ cells are located at the periphery of the cyst. Germline cysts are enveloped by somatic cells. The ovaries of the species studied are polarized, i.e., along the long axis of the ovary there is an evident gradient of germ cell development. The data obtained suggest ovary meroism, i.e., two categories of germ cells were found: oocytes, which continue meiosis, gather nutrients, grow and protrude into the body cavity, and nurse cells, which do not grow and are supposed to supply oocytes with cell organelles and macromolecules via the cytophore. The ovary structure and mode of oogenesis in the species studied were compared with those of other clitellate annelids. As a rule, in all clitellates studied to date, the ovaries are composed of germline cysts equipped with a cytophore and associated with somatic cells; however, the ovary morphology differs between taxa regarding several quantitative and qualitative features. The ovary organization and mode of oogenesis in L. variegatus and S. heringianus strongly resemble those found in Tubificinae and Branchiobdellida studied to date. Our results also support a sister-group relationship between Lumbriculida and a clade comprising ectoparasitic clitellates (i.e., Branchiobdellida, Acanthobdellida and Hirudinida) with Branchiobdellida as a plesiomorphic sister group to Acanthobdellida and Hirudinida.     

The ultrastructure of the spermatozoon of Haplotaxis ornamentus (Annelida,Oligochaeta, Haplotaxidae) and its phylogenetic significance

Summary The spermatozoon of Haplotaxis ornamentus has characteristics common to all oligochaete sperm: filiform; primary acrosome vesicle carried on an acrosome tube and containing an axial rod (perforatorium) in an invagination (subvesicular space or secondary acrosomal invagination); an elongate, highly condensed cylindrical nucleus followed by a cylindrical midpiece of radially adpressed mitochondria not penetrated by the axoneme; a single (distal) centriole persistent, though modified, at maturity; axoneme with 9 doublets, each with two outer glycogen granules, and centrally two singlets accompanied by two solid fibres. A peculiar haplotaxid combination of characters (none unique) is slight withdrawal of the primary vesicle into the acrosome tube with a strongly emergent capitulate axial rod and moderately short midpiece. This ultrastructure is consistent with location of the Haplotaxidae at the base of the Haplotaxida (Haplotaxina — Alluroidina — Moniligastrina — Lumbricina). Tubificida sperm, although also plesiomorph for the Oligochaeta, have the autapomorphy elongate periaxial sheath (secondary tube), excepting the Phreodrilidae whose sperm show convergent resemblances to the Lumbricina. The term annuloid has been introduced for annulus-like structures of varied origins.     

PHYLOGENY OF THE CONJUGATING GREEN ALGAE (ZYGNEMOPHYCEAE) BASED ON rbc L SEQUENCES

Sequences of the gene encoding the large subunit of RUBISCO (rbcL) for 30 genera in the six currently recognized families of conjugating green algae (Desmidiaceae, Gonatozygaceae, Mesotaeniaceae, Peniaceae, and Zygnemataceae) were analyzed using maximum parsimony and maximum likelihood; bootstrap replications were performed as a measure of support for clades. Other Charophyceae sensu Mattox and Stewart and representative land plants were used as outgroups. All analyses supported the monophyly of the conjugating green algae. The Desmidiales, or placoderm desmids, constitute a monophyletic group, with moderate to strong support for the four component families of this assemblage (Closteriaceae, Desmidiaceae, Gonatozygaceae, and Peniaceae). The analyses showed that the two families of Zygnematales (Mesotaeniaceae, Zygnemataceae), which have plesiomorphic, unornamented and unsegmented cell walls, are not monophyletic. However, combined taxa of these two traditional families may constitute a monophyletic group. Partitioning the data by codon position revealed no significant differences across all positions or between partitions of positions one and two versus position three. The trees resulting from parsimony analyses using first plus second positions versus third position differed only in topology of branches with poor bootstrap support. The tree derived from third positions only was more resolved than the tree derived from first and second positions. The rbcL‐based phylogeny is largely congruent with published analyses of small subunit rDNA sequences for the Zygnematales. The molecular data do not support hypotheses of monophyly for groups of extant unicellular and filamentous or colonial desmid genera exhibiting a common cell shape. A trend is evident from simple omniradiate cell shapes to taxa with lobed cell and plastid shapes, which supports the hypothesis that chloroplast shape evolved generally from simple to complex. The data imply that multicellular placoderm desmids are monophyletic. Several anomalous placements of genera were found, including the saccoderm desmid Roya in the Gonatozygaceae and the zygnematacean Entransia in the Coleochaetales. The former is strongly supported, although the latter is not, and Entransia's phylogenetic position warrants further study.     

亚洲蝮亚科蛇属间系统发生支序分析 (蛇亚目：蝰科)

在大量比较形态研究的基础上,选择了５个特征方面２８个性状,以支序分析方法探讨了分布于亚洲蝮亚科蛇５属１４种的系统发生关系,结果表明：该亚科蛇类可以划分为３个不同的类群,第一个类群包括尖吻蝮属、瘤鼻蝮属、红口腹属,它们具有较多的祖征,代表了该科中原始一类,基中红口蝮可能是最原始的一属;亚洲蝮属单独形成一个类群;第三个类群为原广义的烙铁头蛇属,包括竹叶青蛇属、原矛蝮属、烙铁头蛇属、黑绿烙铁头蛇属、莽山     

Phylogeny of the Acanthocephala based on morphological characters

Only four previous studies of relationships among acanthocephalans have included cladistic analyses, and knowledge of the phylogeny of the group has not kept pace with that of other taxa. The purpose of this study is to provide a more comprehensive analysis of the phylogenetic relationships among members of the phylum Acanthocephala using morphological characters. The most appropriate outgroups are those that share a common early cell-cleavage pattern (polar placement of centrioles), such as the Rotifera, rather than the Priapulida (meridional placement of centrioles) to provide character polarity based on common ancestry rather than a general similarity likely due to convergence of body shapes. The phylogeny of 22 species of the Acanthocephala was evaluated based on 138 binary and multistate characters derived from comparative morphological and ontogenetic studies. Three assumptions of cement gland structure were tested: (i) the plesiomorphic type of cement glands in the Rotifera, as the sister group, is undetermined; (ii) non-syncytial cement glands are plesiomorphic; and (iii) syncytial cement glands are plesiomorphic. The results were used to test an early move of Tegorhynchus pectinarius to Koronacantha and to evaluate the relationship between Tegorhynchus and Illiosentis. Analysis of the data-set for each of these assumptions of cement gland structure produced the same single most parsimonious tree topology. Using Assumptions i and ii for the cement glands, the trees were the same length (length = 404 steps, CI = 0.545, CIX = 0.517, HI = 0.455, HIX = 0.483, RI = 0.670, RC = 0.365). Using Assumption iii, the tree was three steps longer (length = 408 steps, CI = 0.539, CIX = 0.512, HI = 0.461, HIX = 0.488, RI = 0.665, RC = 0.359). The tree indicates that the Palaeacanthocephala and Eoacanthocephala both are monophyletic and are sister taxa. The members of the Archiacanthocephala are basal to the other two clades, but do not themselves form a clade. The results provide strong support for the Palaeacanthocephala and the Eoacanthocephala and the hypothesis that the Eoacanthocephala is the most primitive group is not supported. Little support for the Archiacanthocephala as a monophyletic group was provided by the analysis. Support is provided for the recognition of Tegorhynchus and Illiosentis as distinct taxa, as well as the transfer of T. pectinarius to Koronacantha.     

Phylogenetic relationships among genera of the Tetrabothriidae (Eucestoda)

Cladistic analysis of the generic-level relationships within the family Tetrabothriidae was conducted. A single cladogram resulted from evaluation of 28 homologous transformation series representing 41 character states. The genus Tetrabothrius was recognized as plesiomorphic followed by Chaetophallus and Trigonocotyle. The latter was considered as the sister group for the remaining tetrabothriid genera of marine mammals. Anophryocephalus, Strobilocephalus, and Priapocephalus are among the most highly derived genera and are postulated as having close evolutionary affinities. Comparisons to previous explicit hypotheses for relationships among the genera indicated the present analysis was the most efficient phylogenetic statement (consistency index = 85.4%) for the 28 attributes evaluated. The recognition of Tetrabothrius as primitive and a natural grouping of Anophryocephalus, Strobilocephalus, and Priapocephalus in part confirmed results of previous studies of the Tetrabothriidae.     

Cladistic Analysis of Sphagnum in Northeast China

This paper deals with the phylogenetic relationships in Sphagnum using the Wagner Groundplan-Divergence method. The main principle of the Wagner GPD method is grouping based on synapomorphy derived from outgroup comparison and ontogenetic analysis whenever possible. We make use of 21 available characters from gametophytes, estimate plesiomorphic conditions on the principle that characters found in the group under study and in most or all members of related groups are plesiomorphic, while those found only within the group are apomorphic, and finally arrange taxa according to shared derived features. In the Wagner tree diagrams, all characters can be placed on a Wagner tree so that the various relationships in the genus Sphagnum can be visualized. The results were as follows: 1. The genus Sphagnum can be divided into six sections, i.e. Sphagnum, Squarrosa, Acutifolia, Cuspidata, Subsecunda and Polyclada. They are almost consistent withe those derived from classical and numerical taxonomy of Sphagnum. 2. In Wagner tree diagrams, Section Sphagnum and Sect. Squarros were branched earlier, so they are primitive and the other four sections were last branched, so they are derived. Sphagnum magellanicum is a rather primitive species, whereus S. girgensohnii andS. fimbriatum are rather advanced ones in the 14 species of Sphagnum investigated.     

BASAL TISSUE STRUCTURE IN THE EARLIEST EUCONODONTS: TESTING HYPOTHESES OF DEVELOPMENTAL PLASTICITY IN EUCONODONT PHYLOGENY

Abstract:  The hypothesis that conodonts are vertebrates rests solely on evidence of soft tissue anatomy. This has been corroborated by microstructural, topological and developmental evidence of homology between conodont and vertebrate hard tissues. However, these conclusions have been reached on the basis of evidence from highly derived euconodont taxa and the degree to which they are representative of plesiomorphic euconodonts remains an open question. Furthermore, the range of variation in tissue types comprising the euconodont basal body has been used to establish a hypothesis of developmental plasticity early in the phylogeny of the clade, and a model of diminishing potentiality in the evolution of development systems. The microstructural fabrics of the basal tissues of the earliest euconodonts (presumed to be the most plesiomorphic) are examined to test these two hypotheses. It is found that the range of microstructural variation observed hitherto was already apparent among plesiomorphic euconodonts. Thus, established histological data are representative of the most plesiomorphic euconodonts. However, although there is evidence of a range in microstructural fabrics, these are compatible with the dentine tissue system alone, and the degree of variation is compatible with that seen in clades of comparable diversity.     

"ALL TREE HISTOGRAMS" AND THE EVALUATION OF CLADISTIC EVIDENCE: SOME AMBIGUITIES

Abstract— Inspection of trees of varying lengths (by the option ALL TREES, which produces a histogram for tree lengths in PAUP 3.0) has been used to evaluate cladistic data and results. For example, a result may be judged more effective if the groups supported in the most parsimonious tree are preserved in trees that require increasingly greater amounts of homoplasy. Evaluation of grouping purely on the basis of this stability criterion ignores other highly relevant aspects of cladistic results. In particular, some data sets may incorporate additional taxa that introduce homoplasy to the shortest tree in a manner that concurrently allows for a revised understanding of character optimization patterns. These taxa may render groups preserved in the shortest tree less stable, but this result is not necessarily deficient if the homoplasy underlying such instability reveals possible character state changes for the given taxa irretrievable from the original matrix. The hypothetical example described here is relevant to so called "stem", "basal" or "plesiomorphic sister" taxa that are commonly considered in studies of both fossil and extant taxa.