Floristic composition and community structure of epiphytic angiosperms in a terra firme forest in central Amazonia

This survey aimed to describe the floristic composition and structure of the epiphytic community occurring in a terra firme forest in the city of Coari, Brazil, in the Amazon region. Data collection was performed with a 1.5 ha plot method, with which upland, slope and lowland habitats were sampled. All angiosperm epiphytes and their host plants (diameter at breast height > 10 cm) were sampled. We recorded 3.528 individuals in 13 families, 48 genera and 164 species. Araceae was the most prevalent family with regard to the importance value and stood out in all related parameters, followed by Bromeliaceae, Cyclanthaceae and Orchidaceae. The species with the highest epiphytic importance values were Guzmania lingulata (L.) Mez. and Philodendron linnaei Kunth. The predominant life form was hemiepiphytic. Estimated floristic diversity was 3.2 (H'). The studied epiphytic community was distributed among 727 host plants belonging to 40 families, 123 genera and 324 species. One individual of Guarea convergens T.D. Penn. was the host with the highest richness and abundance of epiphytes. Stems/trunks of host plants were the most colonized segments, and the most favorable habitat for epiphytism was the lowlands, where 84.1% of species and 48.2% of epiphytic specimens were observed

Rolling the Dice or Struggling for Survival : Cheating in life's casino

At every scale of life, from microscopic bacteria to the towering giants of Amazonian trees we see a similar pattern of diversity where not every individual gets to be equally abundant. Rather, there is a pattern in which common species are rare and rare species are common. But how does this seemingly universal pattern of diversity arise and how is it is maintained? What mechanisms account for the rarity of some and the commonness of others? Hypotheses can be categorized in two different perspectives: classical niche ecology, arguing that natural selection has shaped and altered species to outcompete others or neutral ecology, stating that a never ending game of chance alters community structure according to fixed laws of probability. One might say that each organism is either struggling for life or rolling the dice in life’s casino. The main theme of the thesis by Edwin Pos is to quantify the relative importance of these different mechanisms shaping community composition. In this thesis, theoretical models were developed to test the relative importance of selection, migration and stochastic events on structuring community composition. But as any theoretical model needs empirical input, the first chapters of his thesis are devoted to validating and testing important assumptions and caveats of using and analyzing ecological data. First it is shown that having a large number of unidentified species in a dataset, which often is the case for ecological field data, may not affect our results as much as is often thought. Second, that estimators of species diversity based on a logseries distribution are much more effective in estimating species richness for highly diverse ecosystems than other, far more commonly, used nonparametric estimators. Third, a comparison between many different mathematical methods for the estimation of migration shows that in many cases this is more an approximation of the homogenization among local communities over time than a direct measurement of migration. Combining the above and developing a new simulation model, a level of biological reality was added to predictions from neutral theory, simultaneously focusing at both local and regional scales of life. The results showed that no matter how well parameterized or how well the output of simulations fitted the regional patterns, an accurate simultaneous prediction on both regional and local diversity patterns was impossible to attain. It was concluded that other non-neutral processes must be at work, at least at the local level. Finally the use of mathematical principles from information theory, the Maximum Entropy Formalism showed an overall low, but strong, environmentally dependent effect of specific functional traits on genus level composition. Very strong effects of dispersal accompanied this pattern of selection, with a strong spatial gradient in dispersal that depends on geographical distance. The combined results of this thesis show that both niche and neutral driven processes play important roles in structuring community composition and provides clues as to where we should focus our attention towards understanding the game of life

Rolling the Dice or Struggling for Survival : Cheating in life's casino

At every scale of life, from microscopic bacteria to the towering giants of Amazonian trees we see a similar pattern of diversity where not every individual gets to be equally abundant. Rather, there is a pattern in which common species are rare and rare species are common. But how does this seemingly universal pattern of diversity arise and how is it is maintained? What mechanisms account for the rarity of some and the commonness of others? Hypotheses can be categorized in two different perspectives: classical niche ecology, arguing that natural selection has shaped and altered species to outcompete others or neutral ecology, stating that a never ending game of chance alters community structure according to fixed laws of probability. One might say that each organism is either struggling for life or rolling the dice in life’s casino. The main theme of the thesis by Edwin Pos is to quantify the relative importance of these different mechanisms shaping community composition. In this thesis, theoretical models were developed to test the relative importance of selection, migration and stochastic events on structuring community composition. But as any theoretical model needs empirical input, the first chapters of his thesis are devoted to validating and testing important assumptions and caveats of using and analyzing ecological data. First it is shown that having a large number of unidentified species in a dataset, which often is the case for ecological field data, may not affect our results as much as is often thought. Second, that estimators of species diversity based on a logseries distribution are much more effective in estimating species richness for highly diverse ecosystems than other, far more commonly, used nonparametric estimators. Third, a comparison between many different mathematical methods for the estimation of migration shows that in many cases this is more an approximation of the homogenization among local communities over time than a direct measurement of migration. Combining the above and developing a new simulation model, a level of biological reality was added to predictions from neutral theory, simultaneously focusing at both local and regional scales of life. The results showed that no matter how well parameterized or how well the output of simulations fitted the regional patterns, an accurate simultaneous prediction on both regional and local diversity patterns was impossible to attain. It was concluded that other non-neutral processes must be at work, at least at the local level. Finally the use of mathematical principles from information theory, the Maximum Entropy Formalism showed an overall low, but strong, environmentally dependent effect of specific functional traits on genus level composition. Very strong effects of dispersal accompanied this pattern of selection, with a strong spatial gradient in dispersal that depends on geographical distance. The combined results of this thesis show that both niche and neutral driven processes play important roles in structuring community composition and provides clues as to where we should focus our attention towards understanding the game of life

The Amazon Epiphyte Network: A First Glimpse Into Continental-Scale Patterns of Amazonian Vascular Epiphyte Assemblages

Epiphytes are still an understudied plant group in Amazonia. The aim of this study was to identify distributional patterns and conservation priorities for vascular epiphyte assemblages (VEA) across Amazonia. We compiled the largest Amazonian epiphyte plot database to date, through a multinational collaborative effort of 22 researchers and 32 field sites located across four Amazonian countries – the Amazonian Epiphyte Network (AEN). We addressed the following continental-scale questions by utilizing the AEN database comprising 96,448 epiphyte individuals, belonging to 518 vascular taxa, and growing on 10,907 tree individuals (phorophytes). Our objectives here are, first, to present a qualitative evaluation of the geographic distribution of the study sites and highlight regional lacunae as priorities for future quantitative inventories. Second, to present the floristic patterns for Amazonia-wide VEA and third, to combine multivariate analyses and rank abundance curves, controlled by major Amazonian habitat types, to determine how VEA vary geographically and ecologically based on major Amazonian habitat types. Three of the most striking patterns found are that: (1) VEA are spatially structured as floristic similarity decays with geographic distance; (2) a core group of 22 oligarchic taxa account for more than a half of all individuals; and (3) extensive floristic sampling gaps still exist, mainly across the highly threatened southern Amazonian deforestation belt. This work represents a first step toward unveiling distributional pattern of Amazonian VEA, which is important to guide future questions on ecology and species distribution ranges of VEA once the collaborative database grows allowing a clearer view of patterns

Diversidade de bromeliáceas epífitas na Área de Proteção Ambiental Ilha do Combu, Belém, Pará, Brasil Diversity of epiphytic bromeliads in the environmental protection area of Combu Island, Belém, Pará, Brazil

Informações sobre a diversidade no nível de espécie oferecem subsídios importantes para o desenvolvimento sustentável e a conservação biológica. Neste contexto, estudos com Bromeliaceae merecem destaque, especialmente porque o grupo é importante ecologicamente, mas ainda pouco conhecido na Região Norte. Neste trabalho, foram demarcadas duas parcelas de 100 m x 100 m em uma floresta de várzea localizada na Área de Proteção Ambiental Ilha do Combu, em Belém, Estado do Pará. Cada parcela foi subdividida em oito parcelas de 50 m x 50 m, tendo todas as espécies e espécimes de bromeliáceas epífitas registradas e quantificadas. A diversidade do grupo foi calculada utilizando o índice de Shannon-Wiener. Foram registrados 1.339 indivíduos pertencentes a oito espécies e quatro gêneros. Tillandsia e Aechmea apresentaram maior riqueza. A diversidade de espécies na área foi de H= 1,10, apresentando dominância acentuada de muitos indivíduos em poucas espécies.<br>Information about diversity at the species level offers data for sustainable development and biological conservation. In this context, studies about Bromeliaceae are noteworthy, especially because this group is ecologically important and poorly known in the North Region of Brazil. In this study, two grids (100 m x 100 m) were delineated in a floodplain forest in the environmental protection area of Combu Island, Belém, Pará, Brazil. The grids were subdivided into eight grids of 50 m x 50 m, and all species and individuals of epiphytic Bromeliaceae were recorded and quantified. The diversity was calculated using the Shannon-Wiener index. A total of 1,339 individuals, belonging to eight species and four genera were recorded. Tillandsia and Aechmea presented the greatest richness. The diversity of species was H= 1.10, presenting sharp dominance of many individuals of few species