Navegando por Assunto "Ecologia animal - Amazônia"

Agora exibindo 1 - 2 de 2

Acesso aberto (Open Access)
Ecologia populacional de Ocypode quadrata (Brachyura: Ocypodidae) em uma praia arenosa exposta de macromaré da costa amazônica do Brasil
(Universidade Federal do Pará, 2017-03) SOUZA, Diego Garcia Cordeiro; POMBO, Maíra; http://lattes.cnpq.br/0599201977466564; PETRACCO, Marcelo; http://lattes.cnpq.br/6834814201680920; https://orcid.org/0000-0001-6501-0099
The present study analyzes the population ecology of Ocypode quadrata (Brachyura: Ocypodidae) on an exposed, macrotidal, dissipative sandy beach located on the Amazon coast, during one year. Indirect (burrow counting and measurement) and direct (burrow excavation and assessment of individuals) methods were used on population assessments. Burrow abundance variation was analyzed over time and as a function of environmental variables (sediment properties, precipitation, air and seawater temperature, salinity). Zonation was described through burrow distribution by distance from the high tide mark. Burrow diameter was used to estimate individual growth parameters of the population. Burrow occupation rate, sex ratio and relation between burrow diameter and crab measures (carapace length, width and depth) were also estimated. Abundance was higher on the rainy season (0.78 ± 0.24 burrow.m-1, against 0.37 ± 0.13 burrow.m- 1 on the dry season) and related positively to precipitation and negatively to sediment grain size. The population was practically restricted to the supralittoral zone. The estimated individual growth parameters (L∞=53.36 mm, K=0.76 yr-1, t0=0.014 yr, Φ=3.34) describe a well-adjusted curve to cohort progression over time. Burrow occupation rate varied between 12.5% and 28.7%. There was sex equilibrium during the rainy season, however, changing to male predominance on the dry season. Burrow diameter was related mainly to carapace width. These are the first data of ghost crab population behavior on Amazon macrotidal environments. These, compared to available data on other regions, also gives insight on latitudinal tendencies of population parameters.
Acesso aberto (Open Access)
O papel de mamíferos de médio e grande porte como modificadores do habitat na Amazônia Ocidental
(Universidade Federal do Pará, 2019-12) BORGES, Luiz Henrique Medeiros; OLIVEIRA, Ana Cristina Mendes; http://lattes.cnpq.br/1199691414821581; https://orcid.org/0000-0002-7863-9678; SILVA, Carlos Augusto Peres da; http://lattes.cnpq.br/9267735737569372; https://orcid.org/0000-0002-1588-8765
Medium to large-bodied terrestrial mammals have a wide diversity of forms, life history, behaviour, physiology, and consequently a high diversity of ecological roles played in natural and human-modified ecosystems. Ecological functions such as seed dispersal, seed predation, pollination, population control, nutrient cycling and transport, and ecosystem engineering help maintain tropical ecosystems and regulate species diversity. Ecosystem engineers are species that by their presence and/or activity alter the biotic and abiotic environment, modulating the availability of resources and modifying habitat structure for other species. The way organisms can affect each other is diverse and occurs mainly through ecological interactions such as predation, competition and commensalism or facilitation, which in turn encompass several ecological processes such as pollination, dispersal, herbivory and prey control. The first chapter of this thesis assessed the role of Priodontes maximus (Giant Armadillo; tatu canastra) as an ecosystem engineer in southwestern Amazonian forests. Our results showed that a wide diversity of terrestrial vertebrates benefit from P. maximus burrows. Sites with high local diversity tend to increase the amount of interactions between vertebrate species and armadillo burrows. In addition, we identified the purpose for which most vertebrates use the burrows of this large excavator, showing that the interaction established in the burrows is broadly and strongly connected for a variety of purposes. In the second chapter of this thesis, I examine how medium and large-bodied mammals can interfere with the regeneration process of man-made treefall clearings formed by low-impact selective logging in southwestern Amazonia. Based on the relative abundance of species, damage to artificial seedlings was measured within both clearings and otherwise comparable shaded-understorey environments. Based on the results, I can infer that medium and large mammals affect seedling recruitment process in clearings. The impact of mammal-induced seedling mortality (via trampling and/or herbivory) is much greater within natural and logging clearings than in closed understorey environments.