Browsing by Author "Moura, Mariana Neves"

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    Caracterização do nicho térmico em comunidades de formigas de restinga.
    (2021) Guimarães, Pedro Henrique; Cardoso, Danon Clemes; Sobrinho, Tathiana Guerra; Cristiano, Maykon Passos; Cardoso, Danon Clemes; Moura, Mariana Neves; Carneiro, Marco Antonio Alves
    A corrente teoria de nicho ecológico o define como o resumo das tolerâncias de necessidades de um organismo, onde essas são as dimensões por onde a ocorrência de um ser vivo é restringida. Dentre as dimensões que podem ser particionadas, a temperatura se constitui como uma das mais importantes, pois está na base dos processos de distribuição dos seres vivos. Tendo como base o aumento das médias globais de temperatura previsto para os próximos anos, os ambientes tropicais podem possuir maior vulnerabilidade, pois, considerando que são ambientes quentes e poucos sazonais, as comunidades biológicas vivendo nesses lugares tendem a apresentar nichos térmicos estreitos, segundo a hipótese de adaptação térmica. Pelo fato das restingas estarem inseridas em ambientes costeiros, sob forte tensores ambientais como a temperatura, elas se apresentam como excelentes ambientes para estudos desse tipo. Além disso, apresentam diversas comunidades de formigas, as quais são organismos que demonstram grande influência térmica na estruturação de suas comunidades. O presente estudo buscou elucidar os padrões térmicos da comunidade de formigas estudada através da construção de modelos de nicho térmico, com base em padrões de ocorrências. Construímos dois transectos de armadilhas de ‘pitfalls’ epigéicos ao longo de um gradiente de vegetação, um localizado nas dunas frontais e o segundo na fisionomia floresta de restinga, com temperatura e umidade sendo medidas durante um período de 24h. A cada três horas os ‘pitfalls’ eram trocados, totalizando, ao final de um dia, oito trocas. O processo foi repetido em três áreas diferentes, separadas por 500m umas das outras. A comunidade de formigas apresentou uma segregação temporal, que se projetou homogeneamente entre as fitofisionomias estudadas, formando um grupo de espécies majoritariamente diurno, e um outro majoritariamente noturno. Além disso, abundância e frequência foram significativamente maiores nos períodos quentes, evidenciando que a temperatura está intimamente ligada ao nível de atividade das formigas.
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    Chromosomal variation among populations of a fungus-farming ant: implications for karyotype evolution and potential restriction to gene flow.
    (2018) Cardoso, Danon Clemes; Heinze, Jürgen; Moura, Mariana Neves; Cristiano, Maykon Passos
    Background: Intraspecific variation in chromosome structure may cause genetic incompatibilities and thus provides the first step in the formation of species. In ants, chromosome number varies tremendously from 2n = 2 to 2n = 120, and several studies have revealed considerable variation in karyotype within species. However, most previous studies were limited to the description of chromosome number and morphology, and more detailed karyomorphometric analyses may reveal additional, substantial variation. Here, we studied karyotype length, genome size, and phylogeography of five populations of the fungus-farming ant Trachymyrmex holmgreni in order to detect potential barriers to gene flow. Results: Chromosome number and morphology did not vary among the five populations, but karyotype length and genome size were significantly higher in the southernmost populations than in the northern populations of this ant. Individuals or colonies with different karyotype lengths were not observed. Karyotype length variation appears to result from variation in centromere length. Conclusion: T. holmgreni shows considerable variation in karyotype length and might provide a second example of centromere drive in ants, similar to what has previously been observed in Solenopsis fire ants. Whether this variation leads to genetic incompatibilities between the different populations remains to be studied.
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    Intraspecific variation in the karyotype length and genome size of fungus-farming ants (genus Mycetophylax), with remarks on procedures for the estimation of genome size in the Formicidae by flow cytometry.
    (2020) Moura, Mariana Neves; Cardoso, Danon Clemes; Baldez, Brenda Carla Lima; Cristiano, Maykon Passos
    Ants (Formicidae) present considerable diversity in chromosome numbers, which vary from n = 1 to n = 60, although this variation is not proportional to that in genome size, for which estimates range from 0.18 pg to 0.77 pg. Intraspecific variation in the chromosome number and karyotype structure has been reported among species, although the variation among populations of the same species has received much less attention, and there are few data on genome size. Here, we studied the karyotype length and genome size of different populations of the fungus-farming ants Mycetophylax conformis (Mayr, 1884) and Mycetophylax morschi (Emery, 1888). We also provide remarks on procedure for the estimation of ant genome size by Flow Cytometry (FCM) analysis. Chromosome number and morphology did not vary among the populations of M. conformis or the cytotypes of M. morschi, but karyotype length and genome size were significantly distinct among the populations of these ants. Our results on the variation in karyotype length and genome size among M. morschi and M. conformis populations reveal considerable diversity that would be largely overlooked by more traditional descriptions of karyotypes, which were also supported by the estimates of genome size obtained using flow cytometry. Changes in the amount of DNA reflect variation in the fine structure of the chromosomes, which may represent the first steps of karyotype evolution and may occur previously to any changes in the chromosome number.
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    Reconstruction of ancestral genome size in Pitcairnioideae (Bromeliaceae) : what can genome size tell us about the evolutionary history of its five genera?
    (2018) Moura, Mariana Neves; Forzza, Rafaela Campostrini; Cristiano, Maykon Passos
    We expand the genome size (GS) database for Bromeliaceae, specifically for subfamily Pitcairnioideae, and verify whether GS can provide information on the diversification of the five genera in this subfamily. We also provide a phylogenetic perspective on GS evolution in the subfamily and reconstruct the ancestral state for this character. We show that the evolutionary path of GS from the origin of angiosperms to the origin of Pitcairnioideae agrees with the proportional model of GS evolution. Furthermore, we propose that the high phenotypic diversity that is found across Bromeliaceae and that is well represented in Pitcairnioideae is both correlated with high rates of GS evolution of the species and associated with a short period of diversification. The paper also highlights the value of flow cytometry as a rapid and reliable technique for generating GS data which can be analysed in conjunction with other molecular and morphological data to help elucidate patterns of evolution and phylogenetic relationships within this family.
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    The tight genome size of ants : diversity and evolution under ancestral state reconstruction and base composition.
    (2020) Moura, Mariana Neves; Cardoso, Danon Clemes; Cristiano, Maykon Passos
    The mechanisms and processes driving change and variation in the genome size (GS) are not well known, and only a small set of ant species has been studied. Ants are an ecologically successful insect group present in most distinct ecosystems worldwide. Considering their wide distribution and ecological plasticity in different environmental contexts, we aimed to expand GS estimation within Formicidae to examine distribution patterns and variation in GS and base composition and to reconstruct the ancestral state of this character in an attempt to elucidate the generalized pattern of genomic expansions. Genome size estimates were generated for 99 ant species, including new GS estimates for 91 species of ants, and the mean GS of Formicidae was found to be 0.38 pg. The AT/GC ratio was 62.40/37.60. The phylogenetic reconstruction suggested an ancestral GS of 0.38 pg according to the Bayesian inference/Markov chain Monte Carlo method and 0.37 pg according to maximum likelihood and parsimony methods; significant differences in GS were observed between the subfamilies sampled. Our results suggest that the evolution of GS in Formicidae occurred through loss and accumulation of non-coding regions, mainly transposable elements, and occasionally by whole genome duplication. However, further studies are needed to verify whether these changes in DNA content are related to colonization processes, as suggested at the intraspecific level.