Holocene history of a lake filling and vegetation dynamics of the Serra Sul dos Carajás, southeast Amazonia

Down-core changes in sedimentary facies, elemental geochemistry, pollen, spore, δ13C, δ15N and radiocarbon records from a filled lake, named R4, of the Serra Sul dos Carajás were used to study the relationship between the paleomorphological and paleoecological processes and their significance for Holocene paleoclimatology of the southeast Amazonia. The sediment deposition of the R4 lake started around 9500 cal yr BP. Increase of detrital components from 9500 to 7000 cal yr BP suggests high weathering of surrounding catchment rocks and soils, and deposition into the lake basin under mudflows. At that time, montane savanna and forest formation were already established suggesting predominance of wet climate. However, from 7000 to 3000 cal yr BP, a decline of detrital input occurred. Also, forest formation and pteridophytes were declined, while palms and macrophytes were remained relatively stable, indicating that water levels of the lake is likely dropped allowing the development of plants adapted to subaerial condition under drier climate conditions. After 3000 cal yr BP, eutrophication and low accommodation space lead to high lake productivity and the final stage of the lake filling respectively, and forest formation may has acquired its current structure, which suggests return of wetter climate conditions.SOUZA FILHO, P. W. M. Universidade Federal do Par

Quillworts from the Amazon: A multidisciplinary populational study on <i>Isoetes serracarajensis</i> and <i>Isoetes cangae</i> - Fig 11

<p>Synteny analysis <i>I</i>. <i>flaccida</i> (A), <i>I</i>. <i>serracarajensis</i> (B, ITV411) and <i>I</i>. <i>cangae</i> (C, ITV2008) chloroplast genomes. Genes are shown in light green with arrows pointing in the direction of transcription. Gray areas represent syntenic regions ranging from white to dark gray the greater the similarity between syntenic regions. Red represents repeated inverted regions.</p

Individual dissimilarity trees based on SNP data separates the two <i>Isoetes</i> species.

<p>VCF SNP files were used by SNP Relate R package to measure coancestry coefficient.</p

Sequence coverage of chloroplast SNPs separates the two <i>Isoetes</i> species.

<p>Illumina reads of the 10 sequenced chloroplasts were mapped to the reference genomes of <i>I</i>. <i>serracarajensis</i> (A) or <i>I</i>. <i>cangae</i> (B). Low coverage ranges from white to blue and high coverages range from green to yellow.</p

Quillworts from the Amazon: A multidisciplinary populational study on <i>Isoetes serracarajensis</i> and <i>Isoetes cangae</i> - Fig 7

<p>A) PCA of morphometric data of <i>Isoetes</i> megaspore showing tubercles group differentiated from other parameters (total variance: 91.5%). B) Distinct clustering of <i>I</i>. <i>cangae</i> from <i>I</i>. <i>serracarajasensis</i> with (w/) and without (w/o) silica coating.</p

Microspore number and size of two <i>Isoetes</i> species from Carajás.

<p>A) Number of microspores per microsporangia. Light gray and dark gray represent two groups of <i>I</i>. <i>serracarajensis</i> independently collected, B) Microspore equatorial and polar diameters and, C) Polar/equatorial diameter ratio of <i>I</i>. <i>cangae</i> (six microsporangia from three plants) and <i>I</i>. <i>serracarajensis</i> (four microsporangia from three plants). The gray shades indicate different shapes. ‘***’ represents a significant difference in a t-test at P<0.01 and ‘ns’ non-significant.</p

The ITS2 DNA barcode can be used to identify the two Carajás <i>Isoetes</i> species.

<p>Summary of the multiple alignment of all genotypes observed for both species. The site position is indicated on top. The site of origin of each genotype of <i>I</i>. <i>serracarajensis</i> is indicated. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0201417#pone.0201417.s009" target="_blank">S2 Fig</a> for the complete multiple alignment.</p

Morphometric values (minimum–maximum) of <i>Isoetes</i> megaspores; w/ (with silica) and w/o (without silica).

<p>Morphometric values (minimum–maximum) of <i>Isoetes</i> megaspores; w/ (with silica) and w/o (without silica).</p