The relationships of Heberdenia bahamensis and H. penduliflora (Myrsinaceae)

A morphological and anatomical investigation is presented of the two species of Heberdenia, H. bahamensis (Macaronesia) and H. penduliflora (Mexico). A cladistic analysis including 27 taxa of the Myrsinaceae and using Jacquinia (Theophrastaceae) and Manilkara (Sapotaceae) as outgroup was performed to provide a hypothesis of the relationships of the two species of Heberdenia. It was concluded that H. bahamensis and H. penduliflora are not more closely related to each other than either is to many other species of the Myrsinaceae, and that they should not be referred to the same genus. Heberdenia bahamensis appears to be most closely related to the Old World genera Pleiomeris, Embelia , and Grenacheria , whereas H. penduliflora is nested within Ardisia s. L , possibly being most closely related to the segregate genus Gentlea. It is suggested that H. penduliflora is probably best referred to a genus of its own.     

The Concept of Monophyly: A Speculative Essay

The concept of monophyly is central to much of modern biology. Despite many efforts over many years, important questions remain unanswered that relate both to the concept itself and to its various applications. This essay focuses primarily on four of these: i) Is it possible to define monophyly operationally, specifically with respect to both the structures of genomes and at the levels of the highest phylogenetic categories (kingdoms, phyla, classes)? ii) May the mosaic and chimeric structures of genomes be sufficiently important factors in phylogeny that situations exist in which the concept may not be applicable? iii) In the history of life on earth were there important groups of organisms that probably had polyphyletic, rather than monophyletic, origins? iv) Does the near universal search for monophyletic origins of clades lead, on occasion, to both undesirable narrowing of acceptable options for development of evolutionary scenarios and sometimes actual omission from consideration of less conventional types of both data and modes of thought, possibly at the expense of biological understanding? Three sections in the essay consider possible answers to these questions: i) A reassessment is made of major features of both the concept and some of its applications. Recent research results make it seem improbable that there could have been single basal forms for many of the highest categories of evolutionary differentiation (kingdoms, phyla, classes). The universal tree of life probably had many roots. Facts contributing to this perception include the phylogenetically widespread occurrences of: horizontal transfers of plasmids, viral genomes, and transposons; multiple genomic duplications; the existence and properties of large numbers of gene families and protein families; multiple symbioses; broad-scale hybridizations; and multiple homoplasys. Next, justifications are reassessed for the application of monophyletic frameworks to two major evolutionary developments usually interpreted as having been monophyletic: ii) the origins of life; and iii) the origins of the vertebrate tetrapods. For both cases polyphyletic hypotheses are suggested as more probable than monophyletic hypotheses. Major conclusions are, as answers to the four questions posed above: probably not, yes, yes, and yes.     

Phylogeny of oligochaetous Clitellata

Clitellata, with more than one third of all annelid species described, is briefly introduced, and an overview of the hypotheses of phylogenetic relationships among the groups traditionally referred to as oligochaetes is given. The presentation is placed in a historical context and describes the trend to move from intuitive, narrative approaches to more formal analyses of character patterns. Monophyly of the earthworms (the megadriles, or Metagynophora sensu Jamieson), or at least a major part of them (Crassiclitellata sensu Jamieson), and paraphyly of the ‘microdrile’ largely aquatic, groups are supported by both morphological and molecular data. Further, DNA sequences as well as spermatozoal ultrastructure corroborate that all leech-like taxa (Hirudinida, Acanthobdellida and Branchiobdellida) constitute a clade derived within ‘Oligochaeta’, closely related to the family Lumbriculidae. Molecular systematic studies also support relationships already identified on the basis of morphological data, e.g., the position of Naididae within Tubificidae, the position of Phreodrilidae close to, but outside, the same family, and the putative sistergroup relationship between the newly discovered Capilloventridae and the rest of Clitellata. A recent study using 18S rDNA suggests that Enchytraeidae is closely related to Metagynophora, and that these two taxa, which contain all terrestrial oligochaetous clitellates, form a clade derived from aquatic ‘microdriles’ This refutes a recent hypothesis proposing that the ancestor of Clitellata was terrestrial. To a great extent, however, the basal resolution of the oligochaetous clitellates remains unclear.     

What does morphology tell us about orchid relationships?—a cladistic analysis

A cladistic analysis of Orchidaceae was undertaken for 98 genera using 71 morphological apomorphies based on a reconsideration of previous character analyses and newly discovered variation. The equally weighted analysis found 60 000 most parsimonious trees with low consistency (CI = 0.29) but high retention (RI = 0.83). The strict consensus reveals a significant amount of structure, and most traditionally recognized subfamilies are supported as monophyletic, including the Apostasioideae, Cypripedioideae, Spiranthoideae, and Epidendroideae. Orchidoideae in the broad sense are paraphyletic, giving rise to spiranthoids. Vanilloids are sister to epidendroids, although exhibiting several states otherwise found only in clearly basal groups, such as Apostasioideae. The nonvandoid epidendroids are poorly resolved, due to a high degree of homoplasy. The vandoids appear to be monophyletic, contrary to recent molecular evidence, possibly due to repeated parallel development of the vandoid character suite. The importance of vegetative characters as evidence putatively independent from floral features is demonstrated in the placement of Tropidia. Implied weighting analysis of these data resulted in similar patterns at high levels, although the Orchidoideae and Spiranthoideae may each be monophyletic and the nonvandoid epidendroids are more resolved. The high degree of structure implied in previous orchid classifications must be reconsidered, given the poor resolution at lower levels in the present trees.     

Implications of Molecular and Morphological Data for Understanding Ateline Phylogeny

The ateline monkeys constitute as certain a monophyletic group as there is among primates. The group is intriguing because while their adaptations are well-documented and their monophyly as a group is unquestioned, their phylogenetic interrelationships are controversial. Molecular data indicate a phylogeny at odds with their morphology. Traditional morphological comparisons isolate Alouatta from the atelins, and link Ateles and Brachyteles as a sister group to the exclusion of Lagothrix. In contrast, several recent molecular studies point to a closer relationship between Brachyteles and Lagothrix than between Brachyteles and Ateles. At the heart of the problem lie the assumptions we make about the validity of data and the homology of observed traits. The fossil record further confounds the issue. We must account for the fossil record because it is positive evidence. But we cannot control how much of it there is or how much of it ever will be known. At this point in time, the ateline molecular and fossil record provoke us to examine critically our morphological approach to phylogenetic modeling.     

The Ultrastructure of Chaenea teres and an Analysis of the Phylogeny of the Haptorid Ciliates

Chaenea teres has typical haptorid ultrastructure. The somatic monokinetid has two transverse microtubular ribbons, an overlapping postciliary microtubular ribbon, and a laterally directed kinetodesmal fiber. The evered cytopharynx forms a dome at the apical end of the cell. The base of the dome is surrounded by oral dikinetids. The left, anterior kinetosome of the oral pair is not ciliated and has a transverse microtubular ribbon, a nematodesmata and a single postciliary microtubule. The right, posterior kinetosome is ciliated and has only postciliary microtubules. The kinetosomes at the anterior ends of the somatic kinetics are close together and their transverse microtubules and nematodesmata contribute to the support of the cytopharynx. The transverse microtubules of these oralized somatic kinetosomes, together with those from the oral dikinetids, line the cytopharynx. Accessory or bulge microtubules arise perpendicular to the transverse microtubules. A dorsal brush of three kineties of clavate cilia is found on the cell surface just posterior to the oral region. Mucocysts and a single type of toxicyst are present. The toxicysts are confined to the oral region. There are multiple ovoid macronuclei that stain weakly. Micronuclei were not observed. Cladistic analysis indicates the Chaenea may be most closely related to Fuscheria and Acropisthium. The cladistic analysis also suggests that existing taxonomies of the subclass Haptoria need to be revised. We propose some modifications to Foissner & Foissner's classification that include transferring Helicoprorodon, Actinobolina, the buetschiliids, and the balantidiids to the order Haptorida and recognizing the close relationship between pleurostomes and spathidiids.