60 research outputs found
The prehistoric human geography of Brazil
The first humans entered South America during the Late Pleistocene, when the lowland tropics were less densely forested than now and sea level was lower. During subsequent millennia, they learned to accommodate to changing conditions and developed an exhaustive knowledge of the biota and their interactions that permitted them to maintain sustainable levels of long-term exploitation of the varying local resources. This attitude of accommodation contrasts with the predatory behavior of recent immigrants of European origin, which threatens not only the future of Amazonia, but of the planet as a whole
A propósito da periodicidade climato-hidrológica que vem provocando grandes crises em Santa Catarina
Availability of food resources and habitat structure shape the individual‐resource network of a Neotropical marsupial
1. Spatial and temporal variation in networks has been reported in different studies.
However, the many effects of habitat structure and food resource availability variation
on network structures have remained poorly investigated, especially in individual‐
based networks. This approach can shed light on individual specialization
of resource use and how habitat variations shape trophic interactions.
2. To test hypotheses related to habitat variability on trophic interactions, we investigated
seasonal and spatial variation in network structure of four populations of
the marsupial Gracilinanus agilis in the highly seasonal tropical savannas of the
Brazilian Cerrado.
3. We evaluated such variation with network nestedness and modularity considering
both cool‐dry and warm‐wet seasons, and related such variations with food resource
availability and habitat structure (considered in the present study as environmental
variation) in four sites of savanna woodland forest.
4. Network analyses showed that modularity (but not nestedness) was consistently
lower during the cool‐dry season in all G. agilis populations. Our results indicated
that nestedness is related to habitat structure, showing that this metric increases
in sites with thick and spaced trees. On the other hand, modularity was positively
related to diversity of arthropods and abundance of fruits.
5. We propose that the relationship between nestedness and habitat structure is an
outcome of individual variation in the vertical space and food resource use by
G. agilis in sites with thick and spaced trees. Moreover, individual specialization in
resource‐rich and population‐dense periods possibly increased the network modularity
of G. agilis. Therefore, our study reveals that environment variability considering
spatial and temporal components is important for shaping network
structure of populations
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