David J. Garbary

Phylogenetic Relationships of the "Green Algae" and "Bryophytes"

Considerable progress has been made recently, based on classical morphological characters and newly described ultrastructural features, in understanding the phylogenetic relationships of the tracheophytes to the green algae and bryophytes. Recent technological advances in molecular biology, particularly the advent of the polymerase chain reaction (PCR), have allowed nucleotide sequence data relevant to such large-scale phylogenetic questions to accumulate, especially ribosomal RNA gene sequences (both the large and small subunits) from the nucleus and the chloroplast. We present synthetic cladistic analyses of the green plants that combine and compare available morphological and molecular data sets

The phylogeny of land plants: A cladistic analysis based on male gametogenesis

A cladistic analysis was carried out to resolve phylogenetic pattern among bryophytes and other land plants. The analysis used 22 taxa of land plants and 90 characters relating to male gametogenesis.Coleochaete orChara/Nitella were the outgroups in various analyses using HENNIG86, PAUP, and MacClade, and the land plant phylogeny was unchanged regardless of outgroup utilized. The most parsimonious cladograms from HENNIG86 (7 trees) have treelengths of 243 (C.I. = 0.58, R.I. = 0.82). Bryophytes are monophyletic as are hornworts, liverworts, and mosses, with hornworts identified as the sister group of a liverwort/moss assemblage. In vascular plants, lycophytes are polyphyletic andSelaginella is close to the bryophytes.Lycopodium is the sister group of the remaining vascular plants (minusSelaginella). Longer treelengths (over 250) are required to produce tree topologies in which either lycophytes are monophyletic or to reconstruct the paraphyletic bryophyte phylogeny of recent authors. This analysis challenges existing concepts of bryophyte phylogeny based on more classical data and interpretations, and provides new insight into land plant evolution.

Motile Gametes of Land Plants: Diversity, Development, and Evolution

Referee: Professor Jeffrey Duckett, School of Biological Sciences, Queen Mary and Westfield College, University of London, Mile End Road, London, E1 4NS, UK Spermatogenesis is a morphogenetic system in plants that is unparalled in its potential to yield diverse and informative structural and developmental data. The unquestionable homology of terrestrial plant spermatozoids to each other and to gametes of related lineages allows an examination of cellular evolution and provides sound data for phylogenetic analyses. In this review we examine the architecture and ontogeny of motile male gametes among major groups of land plants. We begin with a historical perspective that emphasizes the utility of spermatogenesis in understanding cellular evolution and in determining phylogenetic relationships. A cladistic analysis of data based solely on spermatogenesis and a conceptual phylogeny based on combined morphological and molecular data serve as the basis for the comprehensive discussion of architectural and developmental features of plant spermatozoids. Spermatozoids of green plants have two fundamental architectural designs: biflagellated or multiflagellated. Biflagellated gametes vary among basal archegoniates and charophytes in degree of coiling, position, and substructure of the basal bodies and number of organelles. Hornwort spermatozoids are simple, bilaterally symmetrical, and uniquely exhibit a right-handed coil. An autapomorphy among setaphytes (a clade containing mosses and liverworts) is the production of coiled biflagellated sperm cells with dimorphic staggered basal bodies. Like bryophytes, gametes of most lycophytes are biflagellated; two exceptions are Isoëtes and Phylloglossum, taxa that independently evolved multiflagellated sperm cells with approximately 20 flagella. Developmental information, especially related to the origin and development of the locomotory apparatus, are essential to determine structural homology among these taxa. Evaluation of the more complicated multiflagellated gametes of other vascular plants reveals similarities that support a monophyletic fern, Equisetum and Psilotum assemblage. Autapomorphies of this clade include the arrangement of the microtubular cytoskeleton, origin of the locomotory apparatus, and structural details of the basal bodies and multilayered structure. Sperm cell development in archegoniates involves the complete transformation of virtually every cellular component. Crucial to this process are proteinaceous elements of the cytoskeleton. Complex microtubule arrays unique to these cells include the spline, basal bodies, and flagella. The discrete microtubule-organizing centers (MTOCs) that generate these cytoskeletal arrays are equally complex and enable the examination of molecular constituents and ontogenetic modifications. The protein centrin is found in a variety of structures, including the diverse MTOCs and the locomotory apparatus. Actin plays a role in organellar shaping and positioning as well as in cytoplasmic deletion and the maintenance of spatial integrity in the mature cell. We conclude with an overview of the current and potential utility of male gametogenesis as an informative system in approaching fundamental questions relating to cellular differentiation and motility. Characterization of motility mutants will elucidate genetic control of structure-function relationships among cellular components, while biochemical and molecular investigations provide crucial data on the mechanism of development. The examination of spermatogenesis in additional taxa is essential to characterize further developmental variations. Moreover, such studies provide a more comprehensive understanding of plant biodiversity at the cellular level and lead to even greater phylogenetic resolution from this elegant morphogenetic system.

Fractal Dimension as a Quantitative Measure of Complexity in Plant Development

The shapes of 51 fronds from three species of brown algae (Fucus vesiculosus, Fucus serratus and Ascophyllum nodosum) were evaluated by computing the fractal dimensions (D) of their outlines. There was no difference in fractal dimension among mature fronds of the three species, and D was highly correlated with both developmental stage and structural complexity. With increasing age the plants grew not only larger but also more complex in form. Fractal dimension increased systematically with increasing complexity of shape from about 1 to 1.6. Fractal dimension thus provides a useful quantitative measure for the elaboration of shape complexity during plant development.

Systematics of red algae (Rhodophyta)

Red algal systematics is in a state of flux unparalleled since the early decades of this century. Ultrastructural and biochemical studies are providing features for a revised classification at ordinal and supraordinal ranks, whereas characters of vegetative and reproductive morphology continue to establish discontinuities among taxa at lower ranks. Cytological, biosystematic, and chemotaxonomic contributions are viewed as useful in defining relationships at specific and infraspecific ranks. Chemotaxonomic studies, depending on the properties of the taxa that are being studied, are applicable at all taxonomic levels. The taxonomic importance of life histories and themes of vegetative morphology, including spore germination, heterotrichy, initiation and differentiation of thalli are discussed at length. Homologies of auxiliary cells, carpogonial branches, and connecting filaments are examined in the context of relationships among Corallinales, Cryptonemiales, Gigartinales, and Rhodymeniales, and their inclu...

From Sea to Sea: Canada's Three Oceans of Biodiversity

Evaluating and understanding biodiversity in marine ecosystems are both necessary and challenging for conservation. This paper compiles and summarizes current knowledge of the diversity of marine taxa in Canadas three oceans while recognizing that this compilation is incomplete and will change in the future. That Canada has the longest coastline in the world and incorporates distinctly different biogeographic provinces and ecoregions (e.g., temperate through ice-covered areas) constrains this analysis. The taxonomic groups presented here include microbes, phytoplankton, macroalgae, zooplankton, benthic infauna, fishes, and marine mammals. The minimum number of species or taxa compiled here is 15,988 for the three Canadian oceans. However, this number clearly underestimates in several ways the total number of taxa present. First, there are significant gaps in the published literature. Second, the diversity of many habitats has not been compiled for all taxonomic groups (e.g., intertidal rocky shores, deep sea), and data compilations are based on short-term, directed research programs or longer-term monitoring activities with limited spatial resolution. Third, the biodiversity of large organisms is well known, but this is not true of smaller organisms. Finally, the greatest constraint on this summary is the willingness and capacity of those who collected the data to make it available to those interested in biodiversity meta-analyses. Confirmation of identities and intercomparison of studies are also constrained by the disturbing rate of decline in the number of taxonomists and systematists specializing on marine taxa in Canada. This decline is mostly the result of retirements of current specialists and to a lack of training and employment opportunities for new ones. Considering the difficulties encountered in compiling an overview of biogeographic data and the diversity of species or taxa in Canadas three oceans, this synthesis is intended to serve as a biodiversity baseline for a new program on marine biodiversity, the Canadian Healthy Ocean Network. A major effort needs to be undertaken to establish a complete baseline of Canadian marine biodiversity of all taxonomic groups, especially if we are to understand and conserve this part of Canadas natural heritage.

The nature of the ancestral red alga: Inferences from a cladistic analysis

A cladistic analysis of the orders of Rhodophyta is presented. Sixteen taxa and 34 characters comprise the data matrix. Included in the analysis are biochemical and ultrastructural features of pigments, cell walls, cell organelles, mitosis and pit connections as well as vegetative and reproductive characters. The traditional recognition of two classes or subclasses, Bangiophycidae and Florideophycidae, is not supported regardless of whether Porphyridiales, Rhodochaetales or Bangiales is designated the outgroup. Florideophycidae, however, appears to be monophyletic with Bangiales as its sister group. Relationships among taxa with one or two plug cap layers, i.e. Acrochaetiales, Palmariales, Corallinales, Nemaliales, Batrachospermales, Gelidiales and Hildenbrandiales are unresolved. Rhodochaetales, Bangiales and possibly Erythropeltidales are monophyletic, but Porphyridiales is polyphyletic. The class Cyanidiophyceae is not recognized and the included genera are considered to be unicellular red algae belonging to Porphyridiales. Taxa that have been proposed as sister groups for red algae, including Cyanobacteria, Cryptophyta, Glaucophyta and Chlorophyta, and Ascomycetes and Basidiomycetes are discussed in relation to the proposed phylogeny of Rhodophyta.

DISTRIBUTION OF ALGAL EPIPHYTES ACROSS ENVIRONMENTAL GRADIENTS AT DIFFERENT SCALES: INTERTIDAL ELEVATION, HOST CANOPIES, AND HOST FRONDS 1

Understanding epiphyte distribution in coastal communities is important because these organisms affect many others directly or indirectly. Yet, their distribution has been considerably less studied than that of their hosts and other primary‐space holders. Identifying major sources of variation in epiphyte abundance is thus still a need. Environmental gradients help predict species distribution and are pervasive on marine shores. In this study, we test the notion that environmental gradients across intertidal elevation, throughout host canopies, and along host fronds explain a large variation in the abundance of sympatric epiphytes. Our model system was the assemblage of Ascophyllum nodosum (L.) Le Jol. and its epiphytes Vertebrata lanosa (L.) T. A. Chr. [= Polysiphonia lanosa (L.) Tandy], Elachista fucicola (Velley) Aresch., and Pylaiella littoralis (L.) Kjellm. On the coast of Nova Scotia (Canada), we found evidence of a spatial segregation among these species at almost all scales. While the red epiphyte V. lanosa was more common at high‐ and midintertidal elevations (peaking at midelevations) and on middle segments of host fronds, the brown epiphytes E. fucicola and P. littoralis were more common at low elevations and restricted to distal segments of host fronds. Canopy habitat affected abundance only for V. lanosa, which was more common within the host canopy than on its periphery at midelevations. Since the studied gradients are related to predictable changes in abiotic factors, the identification of likely causes behind the observed patterns was facilitated. Our study ends by proposing abiotic and biotic factors that deserve priority in the experimental testing of the forces structuring this assemblage.

Decline of Canada geese (Branta canadensis) and common goldeneye (Bucephala clangula) associated with a collapse of eelgrass (Zostera marina) in a Nova Scotia estuary

Abstract. Mean numbers of migrant Canada geese (Branta canadensis) in Antigonish Harbour in the southern Gulf of St. Lawrence (Canada) during October to December were similar (approx. 450–500 birds) for the period 1998–2000. Similarly, during this period, geese used two foraging sites. However, in 2001, the average number of birds decreased by half and the primary foraging sites were used only rarely. This coincided with a decline of about 95% in the biomass of roots and rhizomes of eelgrass (Zostera marina) that occurred between October 2000 and 2001. Eelgrass is the principal food of geese in this estuary. In addition, there was a reduction of around 50% in the numbers of common goldeneye (Bucephala clangula), which feed on invertebrates associated with eelgrass. Lower than usual weekly abundances of geese and goldeneye are probably the result of an unusually short residence time in the estuary, rather than a decline in the total number of visiting migrants. We attribute these changes in the distribution and abundance of geese and goldeneyes to the dramatic decline in eelgrass.

FLUORESCENT LABELLING OF THE CYTOSKELETON IN CERAMIUM STRICTUM (RHODOPHYTA)

Using rhodamine‐phalloidin to detect F‐actin/microfilaments and indirect immunofluorescence to detect tubulin/microtubules, we studied the cytoskeleton in axial cells of Ceramium strictum Harv., especially microfilaments and microtubules associated with cytoplasmic strands (trabeculae) that extend longitudinally through the central vacuole. As axial cells attained mature size, trabeculae became progressively thinner, branched, and then broke down. An extensive microfilament array was present in peripheral parts of axial cells as well as in trabeculae. Microfilament arrays were highly disrupted by cytochalasin‐B; this resulted in small irregular actin structures in axial cell peripheries and occasional dense aggregations at the base of cells. No actin‐fluorescence was detected in intact trabeculae after cytochalasin‐B treatment. Microtubules formed a primary structural component in trabeculae, which were disrupted by griseofulvin (5 to 0.005 μM) but reformed after two days in griseofulvin‐free medium.