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Ecological Success (ecological + success)
Selected AbstractsThe structure of bacterial communities in the western Arctic Ocean as revealed by pyrosequencing of 16S rRNA genesENVIRONMENTAL MICROBIOLOGY, Issue 5 2010David L. Kirchman Summary Bacterial communities in the surface layer of the oceans consist of a few abundant phylotypes and many rare ones, most with unknown ecological functions and unclear roles in biogeochemical processes. To test hypotheses about relationships between abundant and rare phylotypes, we examined bacterial communities in the western Arctic Ocean using pyrosequence data of the V6 region of the 16S rRNA gene. Samples were collected from various locations in the Chukchi Sea, the Beaufort Sea and Franklin Bay in summer and winter. We found that bacterial communities differed between summer and winter at a few locations, but overall there was no significant difference between the two seasons in spite of large differences in biogeochemical properties. The sequence data suggested that abundant phylotypes remained abundant while rare phylotypes remained rare between the two seasons and among the Arctic regions examined here, arguing against the ,seed bank' hypothesis. Phylotype richness was calculated for various bacterial groups defined by sequence similarity or by phylogeny (phyla and proteobacterial classes). Abundant bacterial groups had higher within-group diversity than rare groups, suggesting that the ecological success of a bacterial lineage depends on diversity rather than on the dominance of a few phylotypes. In these Arctic waters, in spite of dramatic variation in several biogeochemical properties, bacterial community structure was remarkably stable over time and among regions, and any variation was due to the abundant phylotypes rather than rare ones. [source] Long-standing environmental conditions, geographic isolation and host,symbiont specificity influence the relative ecological dominance and genetic diversification of coral endosymbionts in the genus SymbiodiniumJOURNAL OF BIOGEOGRAPHY, Issue 5 2010Todd C. LaJeunesse Abstract Aim, This study examines the importance of geographic proximity, host life history and regional and local differences in environment (temperature and water clarity) in driving the ecological and evolutionary processes underpinning the global patterns of diversity and distribution of symbiotic dinoflagellates. By comparing and contrasting coral,algal symbioses from isolated regions with differing environmental conditions, we may assess the potential of coral communities to respond to significant changes in climate. Location, Indian Ocean. Methods, Community assemblages of obligate symbiotic invertebrates were sampled at numerous sites from two regions, the north-eastern Indian Ocean (Andaman Sea, western Thailand) and the western Indian Ocean (Zanzibar, Tanzania). Molecular genetic methods, including denaturing gradient gel electrophoresis analysis of the ribosomal internal transcribed spacers, DNA sequencing and microsatellite genotyping, were used to characterize the ,species' diversity and evolutionary relationships of symbiotic dinoflagellates (genus Symbiodinium). Host,symbiont specificity, geographic isolation and local and regional environmental factors were evaluated in terms of their importance in governing the distribution and prevalence of certain symbiont taxa. Results, Host-generalist symbionts (C3u and D1-4, formerly D1a now designated Symbiodinium trenchi) frequently occurred alone and sometimes together in hosts with horizontal modes of symbiont acquisition. However, the majority of Symbiodinium diversity consisted of apparently host-specific ,species'. Clade C Symbiodinium were diverse and dominated host assemblages from sites sampled in the western Indian Ocean, a pattern analogous to symbiont communities on the Great Barrier Reef with similar environmental conditions. Clade D Symbiodinium were diverse and occurred frequently in hosts from the north-eastern Indian Ocean, especially at inshore locations, where temperatures are warmer, water turbidity is high and large tidal exchanges commonly expose coral populations to aerial desiccation. Main conclusions, Regional and local differences in cnidarian,algal combinations indicate that these symbioses are ecologically and evolutionarily responsive and can thrive under various environmental conditions. The high temperatures and turbid conditions of the north-eastern Indian Ocean partly explain the ecological success of Clade D Symbiodinium relative to Clade C. Phylogenetic, ecological and population genetic data further indicate that Clade D has undergone an adaptive radiation, especially in regions around Southeast Asia, during the Pleistocene. [source] Greater capacity for division of labour in clones of Fragaria chiloensis from patchier habitatsJOURNAL OF ECOLOGY, Issue 3 2007SERGIO R. ROILOA Summary 1Unlike non-clonal plants, clonal plants can develop a division of labour in which connected ramets specialize to acquire different, locally abundant resources. This occurs as a plastic response to a patchy environment where two resources tend not to occur together and different ramets experience high availabilities of different resources. We hypothesized that if division of labour is an important advantage of clonal growth in such environments in nature, then clones from habitats where resource availabilities are negatively associated should show a greater capacity for division of labour than clones from habitats where resource availabilities are more uniform. 2To test this, we collected clones of Fragaria chiloensis from sand dune and grassland sites in each of three regions of the central coast of California, grew pairs of connected or severed ramets under low light and high N or under high light and low N, and measured leaf area, chlorophyll content and final dry mass. Given that previous work has indicated that high availabilities of light and N show a stronger tendency not to occur together in the dune than in the grassland sites, we expected that clones from dunes would show greater capacity for division of labour than clones from grasslands. 3Clones from dunes showed a greater capacity than clones from grasslands to specialize for acquisition of abundant N via high proportional mass of roots. Clones from the two types of habitats showed similar capacity to specialize for acquisition of abundant light via high leaf area and chlorophyll content of leaves. Specialization via leaf area and chlorophyll content took place mainly within the first half of the 60-day experiment. 4These results provide evidence that division of labour in a clonal plant has been selected for in natural habitats where high levels of different resources tend to be spatially separated. Results also show that division of labour can occur, not just via allocation of mass, but also via physiological traits, and that both morphological and physiological specialization can take place within a few weeks. 5Clonal plants dominate many habitats and include many highly invasive species. Division of labour is one of the most striking potential advantages of clonal growth, and is a remarkable instance of phenotypic plasticity in plants. This study further suggests that division of labour in clonal plants is an instance of adaptive plasticity and could therefore play a part in their widespread ecological success. [source] Rapid evolution of social learningJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 9 2009M. FRANZ Abstract Culture is widely thought to be beneficial when social learning is less costly than individual learning and thus may explain the enormous ecological success of humans. Rogers (1988. Does biology constrain culture. Am. Anthropol. 90: 819,831) contradicted this common view by showing that the evolution of social learning does not necessarily increase the net benefits of learned behaviours in a variable environment. Using simulation experiments, we re-analysed extensions of Rogers' model after relaxing the assumption that genetic evolution is much slower than cultural evolution. Our results show that this assumption is crucial for Rogers' finding. For many parameter settings, genetic and cultural evolution occur on the same time scale, and feedback effects between genetic and cultural dynamics increase the net benefits. Thus, by avoiding the costs of individual learning, social learning can increase ecological success. Furthermore, we found that rapid evolution can limit the evolution of complex social learning strategies, which have been proposed to be widespread in animals. [source] Invasion genetics of the Eurasian round goby in North America: tracing sources and spread patternsMOLECULAR ECOLOGY, Issue 1 2009JOSHUA E. BROWN Abstract The Eurasian round goby Neogobius melanostomus (Apollonia melanostoma) invaded the North American Great Lakes in 1990 through ballast water, spread rapidly, and now is widely distributed and moving through adjacent tributaries. We analyse its genetic diversity and divergence patterns among 25 North American (N = 744) and 22 Eurasian (N = 414) locations using mitochondrial DNA cytochrome b gene sequences and seven nuclear microsatellite loci in order to: (i) identify the invasion's founding source(s), (ii) test for founder effects, (iii) evaluate whether the invasive range is genetically heterogeneous, and (iv) determine whether fringe and central areas differ in genetic diversity. Tests include FST analogues, neighbour-joining trees, haplotype networks, Bayesian assignment, Monmonier barrier analysis, and three-dimensional factorial correspondence analysis. We recovered 13 cytochrome b haplotypes and 232 microsatellite alleles in North America and compared these to variation we previously described across Eurasia. Results show: (i) the southern Dnieper River population was the primary Eurasian donor source for the round goby's invasion of North America, likely supplemented by some alleles from the Dniester and Southern Bug rivers, (ii) the overall invasion has high genetic diversity and experienced no founder effect, (iii) there is significant genetic structuring across North America, and (iv) some expansion areas show reduced numbers of alleles, whereas others appear to reflect secondary colonization. Sampling sites in Lake Huron's Saginaw Bay and Lake Ontario significantly differ from all others, having unique alleles that apparently originated from separate introductions. Substantial genetic variation, multiple founding sources, large number of propagules, and population structure thus likely aided the goby's ecological success. [source] Leaf photoacclimatory responses of the tropical seagrass Thalassia testudinum under mesocosm conditions: a mechanistic scaling-up studyNEW PHYTOLOGIST, Issue 1 2007Napo M. Cayabyab Summary ,,Here, the leaf photoacclimatory plasticity and efficiency of the tropical seagrass Thalassia testudinum were examined. ,,Mesocosms were used to compare the variability induced by three light conditions, two leaf sections and the variability observed at the collection site. ,,The study revealed an efficient photosynthetic light use at low irradiances, but limited photoacclimatory plasticity to increase maximum photosynthetic rates (Pmax) and saturation (Ek) and compensation (Ec) irradiances under high light irradiance. A strong, positive and linear association between the percentage of daylight hours above saturation and the relative maximum photochemical efficiency (FV/FM) reduction observed between basal and apical leaf sections was also found. ,,The results indicate that T. testudinum leaves have a shade-adapted physiology. However, the large amount of heterotrophic biomass that this seagrass maintains may considerably increase plant respiratory demands and their minimum quantum requirements for growth (MQR). Although the MQR still needs to be quantified, it is hypothesized that the ecological success of this climax species in the oligotrophic and highly illuminated waters of the Caribbean may rely on the ability of the canopy to regulate the optimal leaf light environment and the morphological plasticity of the whole plant to enhance total leaf area and to reduce carbon respiratory losses. [source] Translocation of 15N indicates nitrogen recycling in the mat-forming lichen Cladonia portentosaNEW PHYTOLOGIST, Issue 2 2005C. J. Ellis Summary ,,Nitrogen translocation was measured in Cladonia portentosa during 2 yr growth in Scottish heathland. Translocation was predicted to occur if N is resorbed from senescent basal tissue and recycled within the thallus. ,,15N was introduced into either the lower (TU thalli) or upper (TD thalli) 25 mm of 50-mm-long thalli as 15N-NH4+, 15N-NO3, or 15N-glycine. Labelled thalli were placed within intact lichen cushions, either upright (TU) or inverted (TD). Vertical distribution of label was quantified immediately following labelling and after 1 and 2 yr. ,,Independently of the form of introduced label, 15N migrated upwards in TU thalli, with new growth being a strong sink. Sink regions for 15N during year 1 (including new growth) became sources of 15N translocated to new growth in year 2. Upward migration into inverted bases was minimal in TD thalli, but was again marked in new growth that developed from inverted apices. ,,Relocation of N to regions of growth could facilitate internal N recycling, a process postulated to explain the ecological success of mat-forming lichens. [source] Seasonal differences in photosynthesis between the C3 and C4 subspecies of Alloteropsis semialata are offset by frost and droughtPLANT CELL & ENVIRONMENT, Issue 7 2008DOUGLAS G. IBRAHIM ABSTRACT The regional abundance of C4 grasses is strongly controlled by temperature, however, the role of precipitation is less clear. Progress in elucidating the direct effects of photosynthetic pathway on these climate relationships is hindered by the significant genetic divergence between major C3 and C4 grass lineages. We addressed this problem by examining seasonal climate responses of photosynthesis in Alloteropsis semialata, a unique grass species with both C3 and C4 subspecies. Experimental manipulation of rainfall in a common garden in South Africa tested the hypotheses that: (1) photosynthesis is greater in the C4 than C3 subspecies under high summer temperatures, but this pattern is reversed at low winter temperatures; and (2) the photosynthetic advantage of C4 plants is enhanced during drought events. Measurements of leaf gas exchange over 2 years showed a significant photosynthetic advantage for the C4 subspecies under irrigated conditions from spring through autumn. However, the C4 leaves were killed by winter frost, while photosynthesis continued in the C3 plants. Unexpectedly, the C4 subspecies also lost its photosynthetic advantage during natural drought events, despite greater water-use efficiency under irrigated conditions. This study highlights previously unrecognized roles for climatic extremes in determining the ecological success of C3 and C4 grasses. [source] Assessing ecological changes in and around marine reserves using community perceptions and biological surveysAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 4 2010M. Yasué Abstract 1. Well-enforced partial or total no-fishing zones (collectively known as marine protected areas, or MPAs) can help restore degraded coral reefs and enhance fish populations. 2. A comparison was made of community perceptions of ecological changes in an MPA with concurrent scientific data on these changes in the same MPA. Such analyses are particularly important in community-based MPAs where local support is a key determinant of ecological success. 3. The no-take MPA in question was initially launched in partnership with the community in 1995 and formalized in 1998. The perceptions data come from interviews with community members in 1999 and 2004, the biological data come from underwater visual censuses of the MPA from 1998 to 2004. 4. Community members perceived more fish within the MPA and slight increases in catch outside the MPA. In contrast, fish censuses showed a high degree of stochastic variation and only minor increases in fish abundance, size and diversity in and around the MPA between 1998 and 2004. 5. Possible explanations for these discrepancies include different temporal, spatial or species frames of reference and/or limitations to the biological survey technique. Other options include wishful thinking, external influences, a desire to please, or confounding with other benefits. 6. This study demonstrates some of the strengths and weaknesses of community perceptions and biological data. In order to improve our understanding about the changes that occur over time in an MPA and engender community support for the long-term viability of MPAs, it is important to develop diverse and efficient monitoring schemes. Copyright © 2010 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||