ABSTRACT
The diversity of eukaryotic and prokaryotic communities has been assessed by morphological and genetic approaches, which are used to characterize the microbiota in different environments. Here, planktonic prokaryotic and eukaryotic communities of the Araguaia River, located in the Central region of Brazil, were analyzed based on metabarcoding analysis of rRNA genes to evaluate the diversity of these groups in tropical floodplain lakes. Also, we tested their spatial concordance throughout the Araguaia river. Water samples were collected from 8 floodplain lakes in Araguaia River. The 16S and 18S rRNA genes were amplified and sequenced using Illumina MiSeq. For eukaryotes, 34,242 merged reads were obtained and 225 distinct OTUs were delineated, of which 106 OTUs were taxonomically classified. For prokaryotes, 26,426 sequences were obtained and 351 OTUs were detected. Of them, 231 were classified in at least one taxonomic category. The most representative eukaryotes belonged to Ciliophora, Chlorophyta and Charophyta. The prokaryotic phylum with the most OTUs classified were Proteobacteria, Actinobacteria and Bacteroidetes. The lakes did not show spatial concordance when comparing the similarity between their microbiota. The knowledge of freshwater biodiversity using DNA sequencing for important rivers, such as Araguaia River, can improve microbiota inventories of tropical biodiversity hotspots.
Subject(s)
Lakes , Microbiota , Lakes/microbiology , Eukaryota/genetics , Bacteria/genetics , Biodiversity , Microbiota/genetics , PhylogenyABSTRACT
We investigated here the demographical history of Tabebuia impetiginosa (Bignoniaceae) to understand the dynamics of the disjunct geographical distribution of South American seasonally dry forests (SDFs), based on coupling an ensemble approach encompassing hindcasting species distribution modelling and statistical phylogeographical analysis. We sampled 17 populations (280 individuals) in central Brazil and analysed the polymorphisms at chloroplast (trnS-trnG, psbA-trnH, and ycf6-trnC intergenic spacers) and nuclear (ITS nrDNA) genomes. Phylogenetic analyses based on median-joining network showed no haplotype sharing among population but strong evidence of incomplete lineage sorting. Coalescent analyses showed historical constant populations size, negligible gene flow among populations, and an ancient time to most recent common ancestor dated from ~4.7 ± 1.1 Myr BP. Most divergences dated from the Lower Pleistocene, and no signal of important population size reduction was found in coalescent tree and tests of demographical expansion. Demographical scenarios were built based on past geographical range dynamic models, using two a priori biogeographical hypotheses ('Pleistocene Arc' and 'Amazonian SDF expansion') and on two additional hypotheses suggested by the palaeodistribution modelling built with several algorithms for distribution modelling and palaeoclimatic data. The simulation of these demographical scenarios showed that the pattern of diversity found so far for T. impetiginosa is in consonance with a palaeodistribution expansion during the last glacial maximum (LGM, 21 kyr BP), strongly suggesting that the current disjunct distribution of T. impetiginosa in SDFs may represent a climatic relict of a once more wide distribution.
Subject(s)
Bignoniaceae/genetics , Genetic Variation , Trees/genetics , Brazil , DNA, Chloroplast , DNA, Intergenic , Gene Flow , Genetics, Population , Models, Theoretical , Molecular Sequence Data , Phylogeny , Phylogeography , SeasonsABSTRACT
Three main causes to population synchrony are proposed: exogenous factors, dispersal and inter-specific interactions. This paper had as main goal to test the influence of the exogenous factors in the synchrony in spatially isolated (i.e., no dispersal) populations of Sitophilus zeamais (Mots.) (Coleoptera: Curculionidae), in microcosms with different environmental conditions (humidity, temperature and light intensity). Twelve populations of 20 individuals each, were randomly assigned between two treatment conditions: with or without light. Population size and environmental factors (temperature and relative humidity) were weekly assessed for seven months. Temporal trend in populations increase was eliminated adjusting autoregressive models. Population synchrony, detected by means of Pearson's and Spearman's correlation coefficients, was higher within than between treatments, although the populations kept without lamp were more synchronized than populations with lamp. Besides demonstrating the influence of environment on population fluctuations, these results suggest that metabolism and intra-specific interactions are important factors in population dynamic. Organisms exposed to unsuitable environmental conditions may have abnormal metabolic rates, which negatively influences the population grow. Thus, small populations are more likely to suffer from demographic stochasticity, decreasing the probability of the synchrony among populations. On the other hand, in more suitable environments, individuals are expected to have normal metabolic functions, and so, to achieve higher rates of population grow. In this case, the demographic stochasticity has smaller influence, leading populations without lamp to fluctuate synchronously.
Subject(s)
Coleoptera , Animals , Brazil , Environment , Population Dynamics , Stochastic ProcessesABSTRACT
São propostas três causas principais para sincronia de populações: fatores exógenos, dispersão e interações interespecíficas. O presente trabalho teve por objetivo testar a influência dos fatores exógenos na sincronia de populações de Sitophilus zeamais (Mots.) (Coleoptera: Curculionidae), isoladas espacialmente (sem dispersão), em microcosmos com diferentes condições ambientais (umidade e temperatura). Doze populações com 20 indivíduos cada, foram divididas, aleatoriamente, em dois tratamentos: com lâmpada e sem lâmpada. O censo dos indivíduos adultos foi realizado semanalmente, durante sete meses. A tendência de crescimento da abundância ao longo do tempo foi eliminada através do ajuste de modelos autoregressivos. A sincronia entre as populações, detectada por meio dos coeficientes de correlação de Pearson e Spearman, foi maior dentro do que entre tratamentos, embora as populações mantidas sem lâmpada tenham sido mais sincrônicas do que as populações com lâmpada. Além de evidenciarem a influência do ambiente nas flutuações populacionais, esses resultados sugerem que o metabolismo e as interações intraespecíficas são fatores importantes na dinâmica populacional. Organismos em ambientes desfavoráveis podem apresentar taxas metabólicas anormais, contribuindo pouco para o crescimento populacional. Logo, populações pequenas sofrem maior influência da estocasticidade demográfica, reduzindo a probabilidade de sincronia entre elas. Nos ambientes mais favoráveis, espera-se que os indivíduos desenvolvam funções metabólicas normais, levando as populações a apresentar taxas de crescimento mais elevadas. Nesse caso, a estocasticidade demográfica tem menor influência, levando as populações sem lâmpada a flutuar de forma mais sincrônica.
Three main causes to population synchrony are proposed: exogenous factors, dispersal and inter-specific interactions. This paper had as main goal to test the influence of the exogenous factors in the synchrony in spatially isolated (i.e., no dispersal) populations of Sitophilus zeamais (Mots.) (Coleoptera: Curculionidae), in microcosms with different environmental conditions (humidity, temperature and light intensity). Twelve populations of 20 individuals each, were randomly assigned between two treatment conditions: with or without light. Population size and environmental factors (temperature and relative humidity) were weekly assessed for seven months. Temporal trend in populations increase was eliminated adjusting autoregressive models. Population synchrony, detected by means of Pearsons and Spearmans correlation coefficients, was higher within than between treatments, although the populations kept without lamp were more synchronized than populations with lamp. Besides demonstrating the influence of environment on population fluctuations, these results suggest that metabolism and intra-specific interactions are important factors in population dynamic. Organisms exposed to unsuitable environmental conditions may have abnormal metabolic rates, which negatively influences the population grow. Thus, small populations are more likely to suffer from demographic stochasticity, decreasing the probability of the synchrony among populations. On the other hand, in more suitable environments, individuals are expected to have normal metabolic functions, and so, to achieve higher rates of population grow. In this case, the demographic stochasticity has smaller influence, leading populations without lamp to fluctuate synchronously.
Subject(s)
Animals , Coleoptera , Brazil , Environment , Population Dynamics , Stochastic ProcessesABSTRACT
Os cupins normalmente constroem ninhos que apresentam formas e características diferenciadas de acordo com a espécie, oferecendo-lhes proteção, além de manter a coesão da sociedade. Algumas espécies constroem seus ninhos sobre a superfície do solo, enquanto outras preferem a subsuperfície, troncos e galhos de árvores como suporte ou madeira para construção das galerias. O objetivo deste trabalho foi analisar a relação entre a ocorrência de colônias do cupim arborícola Constrictotermes cyphergaster Silvestri e as espécies vegetais suporte em um Cerrado sentido restrito na Serra de Caldas Novas, GO. Os dados sugerem forte associação entre C. cyphergaster e algumas espécies vegetais de porte arbóreo, como Qualea grandiflora Mart., Annona crassiflora Mart., Caryocar brasiliense Camb. e Plathymenia reticulata Benth., evidenciado pelo alto valor do Qui-quadrado (chi2 = 214,986, gl. = 20, P < 0,001). Essa relação é verificada entre outras espécies de cupins e plantas, inclusive na região dos cerrados, e pode estar associada a vários fatores. Por um lado pode ser influenciada pela presença de inimigos naturais (competidores e predadores), e pela produção de substâncias tóxicas por essas plantas, ou por outro lado, pode haver benefício entre as espécies associadas, neste caso indicando relações ecológicas de mutualismo facultativo ou facilitação.
Subject(s)
Animals , Isoptera , Trees/parasitology , Brazil , Isoptera/classificationABSTRACT
Termites usually build nests differently shaped and characterized according to each species, to protect and keep society cohesion. Some species build nests in the ground, some prefer tree thunks or branches as support, whereas other dig galleries in the wood. The purpose of this study is to analyze the relationship between the occurrence of arboreal termites Constrictotermes cyphergaster Silvestri and tree species that support the nest of this species, in a Cerrado sensu strictu of the Serra de Caldas Novas, GO. Data suggest a association relationship between C. Cyphergaster and the tree species Qualea grandiflora Mart., Annona crassiflora Mart., Caryocar brasiliense Camb. and Plathymenia reticulata Benth., shown by high Qui-squared values (chi2 = 214.986, gl. = 20, P < 0.001). This relationship may be found among other termites and tree species, including Cerrado biome, and may be due to several factors, such as natural competitors and predators, toxin production by other tree species or benefits between associated species (facultative mutualism or facilitation).
