The evolutionary history of Symbiodinium and scleractinian hosts - Symbiosis, diversity, and the effect of climate change

Marine invertebrates representing at least five phyla are symbiotic with dinoflagellates from the genus Symbiodinium. This group of single-celled protists was once considered to be a single pandemic species, Symbiodinium microadriaticum. Molecular investigations over the past 25 years have revealed, however, that Symbiodinium is a diverse group of organisms with at least eight (A-H) divergent clades that in turn contain multiple molecular subclade types. The diversity within this genus may subsequently determine the response of corals to normal and stressful conditions, leading to the proposal that the symbiosis may impart unusually rapid adaptation to environmental change by the metazoan host. These questions have added importance due to the critical challenges that corals and the reefs they build face as a consequence of current rapid climate change. This review outlines our current understanding of the diverse genus Symbiodinium and explores the ability of this genus and its symbioses to adapt to rapid environmental change. (c) 2006 Rubel Foundation, ETH Zurich. Published by Elsevier GmbH. All rights reserved.

Phylogeny and evolution of anomalous roots in Daviesia (Fabaceae : Mirbelieae)

The phylogeny of the Australian legume genus Daviesia was estimated using sequences of the internal transcribed spacers of nuclear ribosomal DNA. Partial congruence was found with previous analyses using morphology, including strong support for monophyly of the genus and for a sister group relationship between the clade D. pachyloma and the rest of the genus. A previously unplaced bird-pollinated species, anceps + D. D. epiphyllum, was well supported as sister to the only other bird-pollinated species in the genus, D. speciosa, indicating a single origin of bird pollination in their common ancestor. Other morphological groups within Daviesia were not supported and require reassessment. A strong and previously unreported sister clade of Daviesia consists of the two monotypic genera Erichsenia and Viminaria. These share phyllode-like leaves and indehiscent fruits. The evolutionary history of cord roots, which have anomalous secondary thickening, was explored using parsimony. Cord roots are limited to three separate clades but have a complex history involving a small number of gains (most likely 0-3) and losses (0-5). The anomalous structure of cord roots ( adventitious vascular strands embedded in a parenchymatous matrix) may facilitate nutrient storage, and the roots may be contractile. Both functions may be related to a postfire resprouting adaptation. Alternatively, cord roots may be an adaptation to the low-nutrient lateritic soils of Western Australia. However, tests for association between root type, soil type, and growth habit were equivocal, depending on whether the variables were treated as phylogenetically dependent (insignificant) or independent ( significant).

Generic delimitation and phylogenetic uncertainty: An example from a group that has undergone an explosive radiation

Phylogenetic trees can provide a stable basis for a higher-level classification of organisms that reflects evolutionary relationships. However, some lineages have a complex evolutionary history that involves explosive radiation or hybridisation. Such histories have become increasingly apparent with the use of DNA sequence data for phylogeny estimation and explain, in part, past difficulties in producing stable morphology-based classifications for some groups. We illustrate this situation by using the example of tribe Mirbelieae (Fabaceae), whose generic classification has been fraught for decades. In particular, we discuss a recent proposal to combine 19 of the 25 Mirbelieae genera into a single genus, Pultenaea sens. lat., and how we might find stable and consistent ways to squeeze something as complex as life into little boxes for our own convenience. © CSIRO.

A multiple-outgroup approach to resolving division-level phylogenetic relationships using 16S rDNA data

The 16S rRNA gene (16S rDNA) is currently the most widely used gene for estimating the evolutionary history of prokaryotes, To date, there are more than 30 000 16S rDNA sequences available from the core databases, GenBank, EMBL and DDBJ, This great number may cause a dilemma when composing datasets for phylogenetic analysis, since the choice and number of reference organisms are known to affect the resulting tree topology. A group of sequences appearing monophyletic in one dataset may not be so in another. This can be especially problematic when establishing the relationships of distantly related sequences at the division (phylum) level. In this study, a multiple-outgroup approach to resolving division-level phylogenetic relationships is suggested using 16S rDNA data. The approach is illustrated by two case studies concerning the monophyly of two recently proposed bacterial divisions, OP9 and OP10.

The phylogeography and connectivity of the latitudinally widespread scleractinian coral Plesiastrea versipora in the Western Pacific

Whereas terrestrial animal populations might show genetic connectivity within a continent, marine species, such as hermatypic corals, may have connectivity stretching to all corners of the planet. We quantified the genetic variability within and among populations of the widespread scleractinian coral, Plesiastrea versipora along the eastern Australian seaboard (4145 km) and the Ryukyu Archipelago (Japan, 681 km) using sequences of internal transcribed spacers (ITS1-2) from ribosomal DNA. Geographic patterns in genetic variability were deduced from a nested clade analysis (NCA) performed on a parsimony network haplotype. This analysis allowed the establishment of geographical associations in the distribution of haplotypes within the network cladogram, therefore allowing us to deduce phylogeographical patterns based under models of restricted gene flow, fragmentation and range expansion. No significant structure was found among Ryukyu Archipelago populations. The lack of an association between the positions of haplotypes in the cladogram with geographical location of these populations may be accounted for by a high level of gene flow of P. versipora within this region, probably due to the strong Kuroshio Current. In contrast, strong geographical associations were apparent among populations of P. versipora along the south-east coast of Australia. This pattern of restricted genetic connectivity among populations of P. versipora on the eastern seaboard of Australia seems to be associated with the present surface ocean current (the East Australian Current) on this side of the south-western Pacific Ocean.

Overlapping species boundaries and hybridization within the Monastraea "annularis" reef coral complex in the Pleistocene of the Bahama Islands

Recent molecular analyses indicate that many reef coral species belong to hybridizing species complexes or "syngameons." Such complexes consist of numerous genetically distinct-species or lineages, which periodically split and/or fuse as they extend through time. During splitting and fusion, morphologic intermediates form and species overlap. Here we focus on processes associated with lineage fusion, specifically introgressive hybridization, and the recognition of such hybridization in the fossil record. Our approach involves comparing patterns of ecologic and morphologic overlap in genetically characterized modern species with fossil representatives of the same or closely related species. We similarly consider the long-term consequences of past hybridization on the structure of modern-day species boundaries. Our study involves the species complex Montastraea annularis s.l. and is based in the Bahamas, where, unlike other Caribbean locations, two of the three members of the complex today are not genetically distinct. We measured and collected colonies along linear transects across Pleistocene reef terraces of last interglacial age (approximately 125 Ka) on the islands of San Salvador, Andros, and Great Inagua. We performed quantitative ecologic and morphologic analyses of the fossil data, and compared patterns of overlap among species with data from modern localities where species are and are not genetically distinct. Ecologic and morphologic analyses reveal "moderate" overlap (>10%, but statistically significant differences) and sometimes "high" overlap (no statistically significant differences) among Pleistocene growth forms (= "species"). Ecologic analyses show that three species (massive, column, organ-pipe) co-occurred. Although organ-pipes had higher abundances in patch reef environments, columnar and massive species exhibited broad, completely overlapping distributions and had abundances that were not related to reef environment. For morphometric analyses, we used multivariate discriminant analysis on landmark data and linear measurements. The results show that columnar species overlap "moderately" with organ-pipe and massive species. Comparisons with genetically characterized colonies from Panama show that the Pleistocene Bahamas species have intermediate morphologies, and that the observed "moderate" overlap differs from the morphologic separation among the three modern species. In contrast, massive and columnar species from the Pleistocene of the Dominican Republic comprise distinct morphologic clusters, similar to the modern species; organ-pipe species exhibit "low" overlap (

The Caenorhabditis briggsae genome contains active CbmaT1 and Tcb1 transposons

The maT clade of transposons is a group of transposable elements intermediate in sequence and predicted protein structure to mariner and Tc transposons, with a distribution thus far limited to a few invertebrate species. We present evidence, based on searches of publicly available databases, that the nematode Caenorhabditis briggsae has several maT-like transposons, which we have designated as CbmaT elements, dispersed throughout its genome. We also describe two additional transposon sequences that probably share their evolutionary history with the CbmaT transposons. One resembles a fold back variant of a CbmaT element, with long (380-bp) inverted terminal repeats (ITRs) that show a high degree (71%) of identity to CbmaT1. The other, which shares only the 26-bp ITR sequences with one of the CbmaT variants, is present in eight nearly identical copies, but does not have a transposase gene and may therefore be cross mobilised by a CbmaT transposase. Using PCR-based mobility assays, we show that CbmaT1 transposons are capable of excising from the C. briggsae genome. CbmaT1 excised approximately 500 times less frequently than Tcb1 in the reference strain AF16, but both CbmaT1 and Tcb1 excised at extremely high frequencies in the HK105 strain. The HK105 strain also exhibited a high frequency of spontaneous induction of unc-22 mutants, suggesting that it may be a mutator strain of C. briggsae.

Modelling life history strategies with capture-recapture data: Evolutionary demography of the water skink Eulamprus tympanum

Matrix population models, elasticity analysis and loop analysis can potentially provide powerful techniques for the analysis of life histories. Data from a capture-recapture study on a population of southern highland water skinks (Eulamprus tympanum) were used to construct a matrix population model. Errors in elasticities were calculated by using the parametric bootstrap technique. Elasticity and loop analyses were then conducted to identify the life history stages most important to fitness. The same techniques were used to investigate the relative importance of fast versus slow growth, and rapid versus delayed reproduction. Mature water skinks were long-lived, but there was high immature mortality. The most sensitive life history stage was the subadult stage. It is suggested that life history evolution in E. tympanum may be strongly affected by predation, particularly by birds. Because our population declined over the study, slow growth and delayed reproduction were the optimal life history strategies over this period. Although the techniques of evolutionary demography provide a powerful approach for the analysis of life histories, there are formidable logistical obstacles in gathering enough high-quality data for robust estimates of the critical parameters.

Evolutionary theory of history

Several attempts have been made recently to apply Darwinian evolutionary theory to the study of culture change and social history. The essential elements in such a theory are that variations occur in population, and that a process of selective retention operates during their replication and transmission. Location of such variable units in the semantic structure of cognition provides the individual psychological basis for an evolutionary theory of history. Selection operates on both the level of cognition and on its phenotypic expression in action in relation to individual preferred sources of psychological satisfaction. Social power comprises the principal selective forces within the unintended consequences of action and through the struggle of individuals and groups in pursuit of opposing interests. The implication for historiography are methodological in that evolutionary theory of history sharpens the focus of explanatory situational analysis, and interpretive in that it provides a paradigmatic metanarrative for the understanding of historical change.

The interaction between technologies and society: Lessons learnt from 160 evolutionary years of online news services

In mapping the evolutionary process of online news and the socio-cultural factors determining this development, this paper has a dual purpose. First, in reworking the definition of “online communication”, it argues that despite its seemingly sudden emergence in the 1990s, the history of online news started right in the early days of the telegraphs and spread throughout the development of the telephone and the fax machine before becoming computer-based in the 1980s and Web-based in the 1990s. Second, merging macro-perspectives on the dynamic of media evolution by DeFleur and Ball-Rokeach (1989) and Winston (1998), the paper consolidates a critical point for thinking about new media development: that something technically feasible does not always mean that it will be socially accepted and/or demanded. From a producer-centric perspective, the birth and development of pre-Web online news forms have been more or less generated by the traditional media’s sometimes excessive hype about the power of new technologies. However, placing such an emphasis on technological potentials at the expense of their social conditions not only can be misleading but also can be detrimental to the development of new media, including the potential of today’s online news.

The evolutionary structure of scientific theories

David Hull's (1988c) model of science as a selection process suffers from a two-fold inability: (a) to ascertain when a lineage of theories has been established; i.e., when theories are descendants of older theories or are novelties, and what counts as a distinct lineage; and (b) to specify what the scientific analogue is of genotype and phenotype. This paper seeks to clarify these issues and to propose an abstract model of theories analogous to particulate genetic structure, in order to reconstruct relationships of descent and identity.

The Western Alps from the Jurassic to Oligocene: spatio-temporal constraints and evolutionary reconstructions

Despite extensive research in the last 150 years, the regional tectonic reconstruction of the Western Alps has remained controversial. The curved orogenic belt consists of several ribbon-like continental terranes (Sesia/Austroalpine, Internal Crystalline Massifs, Brianconnais), which are separated by two or more ophiolitic sutures (Piemonte, Valais, Antrona?, Lanzo/ Canavese?). High-pressure (HP) metamorphism of each terrane occurred during distinct orogenic episodes: at similar to65 Ma in the Sesia/Austroalpine, at similar to45 Ma in the Piemonte zone and at similar to35 Ma in the Internal Crystalline Massifs. It is suggested that these events reflect individual accretionary episodes, which together with kinematic indicators and the speed and direction of plate motions, provide constraints for the discussed reconstruction model. The model involves a prolonged orogenic history that took place during relative convergence of Europe and Adria (here considered as a promontory of the African plate). The first accretionary event involved the Sesia/Austroalpine terrane. Final closure of the Piemonte Ocean occurred during the Eocene (similar to45 Ma) and involved ultra-high-pressure (UHP) metamorphism of the Piemonte oceanic crust. Incorporation of the Brianconnais terrane in the accretionary wedge occurred thereafter, possibly during or after subduction of the Valais Ocean in the late Eocene (45-35 Ma). This subduction was terminated at ca. 35 Ma, when the Internal Crystalline Massifs (i.e. the assumed internal parts of the Brianconnais terrane) were buried into great depths and underwent HP and UHP metamorphism. (C) 2004 Elsevier B.V. All rights reserved.