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Phylogenetic Levels (phylogenetic + level)
Selected AbstractsThe origin of higher taxa: macroevolutionary processes, and the case of the mammalsACTA ZOOLOGICA, Issue 1 2007T. S. Kemp Abstract The origin of a new higher taxon is characterized by a long-term phylogenetic trend, involving evolutionary changes in a large number of characters. At this phylogenetic level, the conflict between internal integration of the phenotype and its evolvability can be resolved by the correlated progression model, in which many disparate traits evolve by a sequence of small increments in loose correlation with one another, rather than by the modularity model. The trend leading to the new higher taxon implies the existence of a long ridge in an adaptive landscape. An evolutionary lineage tracking it requires adaptive changes in broad biological characteristics, involving many traits. Species selection is a possible additional driver of the trend. These conclusions are tested against the synapsid fossil record of the origin of mammals. The reconstructed sequence of acquisition of mammalian traits supports the correlated progression model. The adaptive ridge involved is postulated to have been a sequence of overlapping niches requiring increasing ability to remain active in daily and seasonally fluctuating environments by means of increasing internal regulation. An inferred speciation bias in favour of relatively small, relatively more progressive carnivores indicates that species selection was also involved in driving the trend. Palaeoenvironmental evidence indicates that ecological opportunity probably played a role at certain points along the lineage. [source] Richness patterns, species distributions and the principle of extreme deconstructionGLOBAL ECOLOGY, Issue 2 2009Levi Carina Terribile ABSTRACT Aim, To analyse the global patterns in species richness of Viperidae snakes through the deconstruction of richness into sets of species according to their distribution models, range size, body size and phylogenetic structure, and to test if environmental drivers explaining the geographical ranges of species are similar to those explaining richness patterns, something we called the extreme deconstruction principle. Location, Global. Methods, We generated a global dataset of 228 terrestrial viperid snakes, which included geographical ranges (mapped at 1° resolution, for a grid with 7331 cells world-wide), body sizes and phylogenetic relationships among species. We used logistic regression (generalized linear model; GLM) to model species geographical ranges with five environmental predictors. Sets of species richness were also generated for large and small-bodied species, for basal and derived species and for four classes of geographical range sizes. Richness patterns were also modelled against the five environmental variables through standard ordinary least squares (OLS) multiple regressions. These subsets are replications to test if environmental factors driving species geographical ranges can be directly associated with those explaining richness patterns. Results, Around 48% of the total variance in viperid richness was explained by the environmental model, but richness sets revealed different patterns across the world. The similarity between OLS coefficients and the primacy of variables across species geographical range GLMs was equal to 0.645 when analysing all viperid snakes. Thus, in general, when an environmental predictor it is important to model species geographical ranges, this predictor is also important when modelling richness, so that the extreme deconstruction principle holds. However, replicating this correlation using subsets of species within different categories in body size, range size and phylogenetic structure gave more variable results, with correlations between GLM and OLS coefficients varying from ,0.46 up to 0.83. Despite this, there is a relatively high correspondence (r = 0.73) between the similarity of GLM-OLS coefficients and R2 values of richness models, indicating that when richness is well explained by the environment, the relative importance of environmental drivers is similar in the richness OLS and its corresponding set of GLMs. Main conclusions, The deconstruction of species richness based on macroecological traits revealed that, at least for range size and phylogenetic level, the causes underlying patterns in viperid richness differ for the various sets of species. On the other hand, our analyses of extreme deconstruction using GLM for species geographical range support the idea that, if environmental drivers determine the geographical distribution of species by establishing niche boundaries, it is expected, at least in theory, that the overlap among ranges (i.e. richness) will reveal similar effects of these environmental drivers. Richness patterns may be indeed viewed as macroecological consequences of population-level processes acting on species geographical ranges. [source] The continuity of microevolution and macroevolutionJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 5 2002Andrew M. Simons Abstract A persistent debate in evolutionary biology is one over the continuity of microevolution and macroevolution , whether macroevolutionary trends are governed by the principles of microevolution. The opposition of evolutionary trends over different time scales is taken as evidence that selection is uncoupled over these scales. I argue that the paradox inferred by trend opposition is eliminated by a hierarchical application of the ,geometric-mean fitness' principle, a principle that has been invoked only within the limited context of microevolution in response to environmental variance. This principle implies the elimination of well adapted genotypes , even those with the highest arithmetic mean fitness over a shorter time scale. Contingent on premises concerning the temporal structure of environmental variance, selectivity of extinction, and clade-level heritability, the evolutionary outcome of major environmental change may be viewed as identical in principle to the outcome of minor environmental fluctuations over the short-term. Trend reversals are thus recognized as a fundamental property of selection operating at any phylogenetic level that occur in response to event severities of any magnitude over all time scales. This ,bet-hedging' perspective differs from others in that a specified, single hierarchical selective process is proposed to explain observed hierarchical patterns of extinction. [source] Developmental genome processing and protein evolution in the ciliate Chilodonella uncinataTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 2 2005REBECCA A. ZUFALL Ciliates are microbial eukaryotes with dual genomes, one present in the transcriptionally inactive germline micronucleus (MIC) and the other in the somatic macronucleus (MAC). In the development of the MAC from the MIC, ciliates process their genomes by chromosomal fragmentation, excision of internal excised sequences (IESs), and amplification of chromosomes. Chilodonella uncinata is in a class of ciliates, Phyllopharyngea, that undergo extensive processing to generate MACs containing thousands of gene-sized chromosomes. Previous analyses suggest that sequences involved in this processing are highly variable among ciliate lineages. In this study, we examine cis-acting signals involved in the elimination of IESs in C. uncinata in order to understand the phylogenetic level at which processing signals are conserved. In addition, we are testing the hypothesis that the differential selection on dual genomes in ciliates allows unusually rapid divergence among paralogs of protein coding genes. [source] Diversity and abundance of freshwater Actinobacteria along environmental gradients in the brackish northern Baltic SeaENVIRONMENTAL MICROBIOLOGY, Issue 8 2009Karin Holmfeldt Summary Actinobacteria are highly abundant in pelagic freshwater habitats and also occur in estuarine environments such as the Baltic Sea. Because of gradients in salinity and other environmental variables estuaries offer natural systems for examining factors that determine Actinobacteria distribution. We studied abundance and community structure of Bacteria and Actinobacteria along two transects in the northern Baltic Sea. Quantitative (CARD-FISH) and qualitative (DGGE and clone libraries) analyses of community composition were compared with environmental parameters. Actinobacteria accounted for 22,27% of all bacteria and the abundance changed with temperature. Analysis of 549 actinobacterial 16S rRNA sequences from four clone libraries revealed a dominance of the freshwater clusters acI and acIV, and two new subclusters (acI-B scB-5 and acIV-E) were assigned. Whereas acI was present at all stations, occurrence of acII and acIV differed between stations and was related to dissolved organic carbon (DOC) and chlorophyll a (Chl a) respectively. The prevalence of the acI-A and acI-B subclusters changed in relation to total phosphorus (Tot-P) and Chl a respectively. Community structure of Bacteria and Actinobacteria differed between the river station and all other stations, responding to differences in DOC, Chl a and bacterial production. In contrast, the composition of active Actinobacteria (analysis based on reversely transcribed RNA) changed in relation to salinity and Tot-P. Our study suggests an important ecological role of Actinobacteria in the brackish northern Baltic Sea. It highlights the need to address dynamics at the cluster or subcluster phylogenetic levels to gain insights into the factors regulating distribution and composition of Actinobacteria in aquatic environments. [source] Comparative study on sensitivity of higher plants and fish to heavy fuel oilENVIRONMENTAL TOXICOLOGY, Issue 4 2004N. Kazlauskien Abstract Laboratory tests were conducted on higher plants [garden cress (Lepidium sativum), great duckweed (Spirodela polyrrhiza), and Tradescantia clone BNL 02] and fish [rainbow trout (Oncorhynchus mykiss) at all stages of development: eggs, larvae and adults] to estimate their sensitivity to heavy fuel oil (HFO). A number of biological indices (survival, growth, and physiological and morphological parameters) as well as the genotoxic impact (Tradescantia) of HFO was evaluated by acute and chronic toxicity tests. Fish were found to be more sensitive to the toxic effect of HFO than were higher plants. EC50 values obtained for higher plants ranged from 8.7 g/L (L. sativum) to 19.8 g/L (Tradescantia), and maximum-acceptable-toxicant concentration (MATC) values ranged from 0.1 to 1.0 g/L of total HFO for L. sativum and Tradescantia, respectively. The 96-h LC50 values ranged from 0.33 g/L, for larvae, to 2.97 g/L, for adult fish, and the MATC value for fish was found to be equal to 0.0042 g/L of total HFO. To evaluate and predict the ecological risk of the overall effects of oil spills, studies should be performed using a set of acute and chronic bioassays that include test species of different phylogenetic levels with the most sensitive morphological, physiological, and genotoxic indices. © 2004 Wiley Periodicals, Inc. Environ Toxicol 19: 449,451, 2004 [source] RIVER CAPTURE, RANGE EXPANSION, AND CLADOGENESIS: THE GENETIC SIGNATURE OF FRESHWATER VICARIANCEEVOLUTION, Issue 5 2006C. P. Burridge Abstract River capture is potentially a key geomorphological driver of range expansion and cladogenesis in freshwater-limited taxa. While previous studies of freshwater fish, in particular, have indicated strong relationships between historical river connections and phylogeographic pattern, their analyses have been restricted to single taxa and geological hypotheses were typically constructed a posteriori. Here we assess the broader significance of river capture among taxa by testing multiple species for the genetic signature of a recent river capture event in New Zealand. During the Quaternary an upper tributary of the Clarence River system was diverted into the headwaters of the Wairau River catchment. Mitochondrial DNA (control region and cytochrome b) sequencing of two native galaxiid fishes (Galaxias vulgaris and Galaxias divergens) supports headwater exchange: populations from the Clarence and Wairau Rivers are closely related sister-groups, whereas samples from the geographically intermediate Awatere River are genetically divergent. The upland bully Gobiomorphus breviceps (Eleotridae), in contrast, lacks a genetic signature of the capture event. We hypothesize that there is an increased likelihood of observing genetic signatures from river capture events when they facilitate range expansion, as is inferred for the two galaxiid taxa studied here. When river capture merely translocates genetic lineages among established populations, by contrast, we suggest that the genetic signature of capture is less likely to be retained, as might be inferred for G. breviceps. Rates of molecular evolution calibrated against this recent event were elevated relative to traditional estimates, consistent with the contribution of polymorphisms to branch lengths at shallow phylogenetic levels prior to fixation by purifying selection and drift. [source] Can taxonomic distinctness assess anthropogenic impacts in inland waters?FRESHWATER BIOLOGY, Issue 9 2006A case study from a Mediterranean river basin Summary 1. It is increasingly recognised that adequate measures of biodiversity should include information on the ,relatedness' of species within ecological assemblages, or the phylogenetic levels at which diversity is expressed. Taxonomic distinctness measures provide a series of indices to achieve this, which are independent of sample size. Taxonomic distinctness has been employed widely in marine systems, where it has been suggested that this index can provide a reliable measure of anthropogenic impact. 2. We tested the behaviour of three related taxonomic distinctiveness indices (Average Taxonomic Distinctness, ,+; Variation in Taxonomic Distinctness, ,+; and Total Taxonomic Distinctness, s,+) in relation to putative levels of anthropogenic impact in inland waters and their potential utility in environmental monitoring, using an extensive data set for aquatic beetles from the south-east of the Iberian Peninsula. 3. Taxonomic distinctness measures were not able to identify human disturbance effects and there were no clear relationships between these new biodiversity measures and the disturbance level recorded at individual localities. Furthermore, the taxonomic distinctness measures used were apparently less sensitive to the effects of anthropogenic impact than other diversity metrics, such as species richness and rarity. 4. We conclude that taxonomic distinctness indices may not always perform as well as other metrics in the assessment of environmental quality. In addition, taxonomic distinctness measure should be interpreted with caution, as their performance and ability to detect anthropogenic disturbance may depend on the phylogenetic structure of sampled taxa within a region, and their evolutionary and ecological history. [source] Pollen and sperm heteromorphism: convergence across kingdoms?JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 1 2005I. Till-Bottraud Abstract Sperm competition theory predicts that males should produce many, similar sperm. However, in some species of animals and plants, males exhibit a heteromorphism that results in the production of at least two different types of sperm or pollen grains. In animals, sperm heteromorphism typically corresponds to the production of one fertile morph and one (or more) sterile morph(s), whereas in plants two or more pollen morphs (one of which can be either sterile or fertile) are produced in all flowers but sometimes in different anthers. Heteromorphism has arisen independently several times across phyla and at different phylogenetic levels. Here, we compare and contrast sperm and pollen heteromorphism and discuss the evolutionary hypotheses suggested to explain heteromorphism in these taxa. These hypotheses include facilitation, nutritive contribution, blocking, cheap filler, sperm flushing or killing for animals; outcrossing and precise cross-pollen transfer or bet-hedging strategy for plants; cryptic female choice for both. We conclude that heteromorphism in the two phyla is most likely linked to a general evolutionary response to sexual selection, either to increase one male's sperm or pollen success in competition with other males, or mediate male/female interactions. Therefore, although sperm and pollen are not homologous, we suggest that heteromorphism represents an example of convergence across kingdoms. [source] Disentangling causes of disjunction on the South Island of New Zealand: the Alpine fault hypothesis of vicariance revisitedBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2007MARTIN HAASE Many elements of the flora and fauna of New Zealand's South Island show disjunct distributions with conspecific populations or closely-related species that occur in the north-west and south separated by a central gap. Three events have been implicated to account for this pattern: Pleistocene glaciations, Pliocene mountain building, or displacement along the Alpine fault, the border of the Pacific and Australian plates stretching diagonally across the South Island from south-west to north-east that formed during the Miocene. Disjunct distributions of species level taxa are probably too young to be due to Alpine fault vicariance. It has therefore been suggested that the biogeographical impact of the Alpine fault, if any, should be apparent on deeper phylogenetic levels. We tested this hypothesis by reconstructing the phylogenetic relationships of the hydrobiid gastropods of New Zealand based on mitochondrial DNA fragments of cytochrome oxidase subunit I (CO I) and 16S rDNA. The creno- and stygobiont species of this family are typically poor dispersers. Therefore, ancient patterns of distribution may be conserved. The phylogenetic reconstructions were in accordance with the Alpine fault hypothesis uniting genera occurring on either side of the fault. Divergence estimates based on a molecular clock of CO I indicated splits predating the Pliocene uplift of the Alps. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 91, 361,374. [source] Phylogenetic Composition of Angiosperm Diversity in the Cloud Forests of MexicoBIOTROPICA, Issue 4 2010Isolda Luna-Vega ABSTRACT Several members of the most ancient living lineages of flowering plants (angiosperms) inhabit humid, woody, mostly tropical habitats. Here we assess whether one of these forest types, the cloud forests of Mexico (CFM), contain a relatively higher proportion of phylogenetically early-diverging angiosperm lineages. The CFM houses an extraordinary plant species diversity, including members of earliest-diverging angiosperm lineages. The phylogenetic composition of CFM angiosperm diversity was evaluated through the relative representation of orders and families with respect to the global flora, and the predominance of phylogenetically early- or late-diverging lineages. Goodness-of-fit tests indicated significant differences in the proportional local and global representation of angiosperm clades. The net difference between the percentage represented by each order and family in the CFM and the global flora allowed identification of clades that are overrepresented and underrepresented in the CFM. Early-diverging angiosperm orders and families were found to be neither over- nor underrepresented in the CFM. A slight predominance of late-diverging phylogenetic levels among overrepresented clades, however, was encountered in the CFM. The resulting pattern suggests that cloud forests provide habitats where the most ancient angiosperm lineages have survived in the face of accumulating species diversity belonging to phylogenetically late-diverging lineages. Abstract in Spanish is available at http://www.blackwell-synergy.com/loi/btp [source] | ||||||||||||||||||||||