36 research outputs found
Availability of food resources and habitat structure shape the individualâresource 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 individualâ
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 coolâdry and warmâwet 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 coolâdry 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
resourceârich and populationâdense 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
O estado do Rio de Janeiro como limite sul e norte de distribuição de algumas espécies de aves
Diurnal and seasonal variability in bird counts in a forest fragment in southeastern Brazil
High Levels of Diversity Uncovered in a Widespread Nominal Taxon: Continental Phylogeography of the Neotropical Tree Frog
Species distributed across vast continental areas and across major biomes provide unique model systems for studies of biotic diversification, yet also constitute daunting financial, logistic and political challenges for data collection across such regions. The tree frog Dendropsophus minutus (Anura: Hylidae) is a nominal species, continentally distributed in South America, that may represent a complex of multiple species, each with a more limited distribution. To understand the spatial pattern of molecular diversity throughout the range of this species complex, we obtained DNA sequence data from two mitochondrial genes, cytochrome oxidase I (COI) and the 16S rhibosomal gene (16S) for 407 samples of D. minutus and closely related species distributed across eleven countries, effectively comprising the entire range of the group. We performed phylogenetic and spatially explicit phylogeographic analyses to assess the genetic structure of lineages and infer ancestral areas. We found 43 statistically supported, deep mitochondrial lineages, several of which may represent currently unrecognized distinct species. One major clade, containing 25 divergent lineages, includes samples from the type locality of D. minutus. We defined that clade as the D. minutus complex. The remaining lineages together with the D. minutus complex constitute the D. minutus species group. Historical analyses support an Amazonian origin for the D. minutus species group with a subsequent dispersal to eastern Brazil where the D. minutus complex originated. According to our dataset, a total of eight mtDNA lineages have ranges >100,000 km2. One of them occupies an area of almost one million km2 encompassing multiple biomes. Our results, at a spatial scale and resolution unprecedented for a Neotropical vertebrate, confirm that widespread amphibian species occur in lowland South America, yet at the same time a large proportion of cryptic diversity still remains to be discovered