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  1. Article ; Online: Abiotic variables affect STX concentration in a meso-oligotrophic subtropical coastal lake dominated by Cylindrospermopsis raciborskii (Cyanophyceae).

    Brentano, Débora Monteiro / Giehl, Eduardo L Hettwer / Petrucio, Maurício Mello

    Harmful algae

    2016  Volume 56, Page(s) 22–28

    Abstract: The cyanobacterium Cylindrospermopsis raciborskii is capable of producing toxins including saxitoxin (STX). Few studies have verified the influence of environmental variables on the production of STX and most have only been studied in the laboratory. The ...

    Abstract The cyanobacterium Cylindrospermopsis raciborskii is capable of producing toxins including saxitoxin (STX). Few studies have verified the influence of environmental variables on the production of STX and most have only been studied in the laboratory. The goal of this work was to identify the abiotic variables related to STX concentration in situ. The relationship among STX concentration and the physical variables, nutrients and chlorophyll-a (chl-a) concentration was examined in a meso-oligotrophic subtropical coastal lake dominated by C. raciborskii. A generalized linear model was developed, incorporating all variables measured monthly over a 45-month monitoring period. Conductivity and dissolved inorganic nitrogen (DIN) concentration provided the greatest explanatory power for STX concentration in situ. Previous studies suggested that C. raciborskii cells exposed to stress associated with higher ionic concentrations appear to activate the biosynthesis of STX suggesting that STX can elicit changes cell permeability and may contribute to the homeostasis of this organism. An increase of DIN concentration results in a higher concentration of STX which may be related to a reduced metabolic demand, since the uptake of inorganic nitrogen requires less energy than N
    MeSH term(s) Cylindrospermopsis/metabolism ; Environmental Monitoring ; Lakes/chemistry ; Nitrogen/metabolism ; Saxitoxin/analysis ; Saxitoxin/metabolism
    Chemical Substances Saxitoxin (35523-89-8) ; Nitrogen (N762921K75)
    Language English
    Publishing date 2016-05-17
    Publishing country Netherlands
    Document type Journal Article
    ZDB-ID 2091119-1
    ISSN 1878-1470 ; 1568-9883
    ISSN (online) 1878-1470
    ISSN 1568-9883
    DOI 10.1016/j.hal.2016.03.017
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article: Niche conservatism and the differences in species richness at the transition of tropical and subtropical climates in South America

    Giehl, Eduardo L. Hettwer / Jarenkow, João André

    Ecography. 2012 Oct., v. 35, no. 10

    2012  

    Abstract: Although detected long ago, latitudinal disparity in species richness lacks a consensus regarding its underlying mechanisms. We evaluated whether the main predictions derived from the tropical niche conservatism hypothesis help to explain differences ... ...

    Abstract Although detected long ago, latitudinal disparity in species richness lacks a consensus regarding its underlying mechanisms. We evaluated whether the main predictions derived from the tropical niche conservatism hypothesis help to explain differences regarding species richness and turnover of species and lineages between forests located in tropical and subtropical climates. If tropical niches are retained, we predict that only a subset of tropical lineages disperses and establishes outside the tropics; tip‐level phylogenetic clustering increases outside the tropics; and the climatic variation drives species richness indirectly via constraints to the distribution of lineages. We compiled 58 checklists along tropical and subtropical sites of riparian forests in southeastern South America. We tested the frequency of niches shifts for species and lineages and the abundance of taxa in each climate. Next, we checked the likelihood of pathways linking climatic and spatial predictors directly with species richness and via phylogenetic clustering estimates. Several lineages only occurred in the tropics, and the number of species and lineages that occurred in both climates was lower than expected by chance. Conversely, few lineages were exclusively subtropical and diversified in the subtropics. Phylogenetic clustering increased in subtropical sites and was correlated with decreasing species richness. An interaction between mean temperature of coldest quarter and precipitation seasonality explained most variation in species richness via increases in phylogenetic clustering. These results support an important contribution of climatic niche conservatism to explain richness disparities between tropics and subtropics, mainly because of the inability of most lineages to colonize the subtropics, which is very likely related to cold intolerance. Since niche conservatism likely drives most of the variation in tree species richness in the region, it provides a mechanistic interpretation of the observed patterns, thus fostering the understanding of richness disparities between these tropical and subtropical tree communities.
    Keywords cold ; niches ; phylogeny ; prediction ; riparian areas ; riparian forests ; species differences ; species diversity ; subtropics ; temperature ; trees ; tropical forests ; tropics ; South America
    Language English
    Dates of publication 2012-10
    Size p. 933-943.
    Publishing place Blackwell Publishing Ltd
    Document type Article
    ZDB-ID 1112659-0
    ISSN 0906-7590
    ISSN 0906-7590
    DOI 10.1111/j.1600-0587.2011.07430.x
    Database NAL-Catalogue (AGRICOLA)

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