RESUMEN
BACKGROUND AND AIMS: Whole-plant performance in water-stressed and disturbance-prone environments depends on a suitable supply of water from the roots to the leaves, storage of reserves during periods of shortage, and a morphological arrangement that guarantees the maintenance of the plants anchored to the soil. All these functions are performed by the secondary xylem of roots. Here, we investigate whether different growth forms of Fabaceae species from the seasonally dry Neotropical environment have distinct strategies for water transport, mechanical support and non-structural carbon and water storage in the root secondary xylem. METHODS: We evaluated cross-sections of root secondary xylem from species of trees, shrubs and subshrubs. We applied linear models to verify the variability in secondary xylem anatomical traits among growth forms. KEY RESULTS: Secondary xylem with larger vessels and lower vessel density was observed in tree species. Vessel wall thickness, vessel grouping index, potential hydraulic conductivity and cell fractions (vessels, fibres, rays and axial parenchyma) were not statistically different between growth forms, owing to the high interspecific variation within the groups studied. CONCLUSION: Our results showed that the variability in anatomical traits of the secondary xylem of the root is species specific. In summary, the cellular complexity of the secondary xylem ensures multiple functional strategies in species with distinct growth forms, a key trait for resource use in an environment with strong water seasonality.
Asunto(s)
Fabaceae , Xilema/anatomía & histología , Árboles/anatomía & histología , Hojas de la Planta/anatomía & histología , AguaRESUMEN
There is an increasing interest in unveiling the dynamics of parasite infection. Understanding the interaction patterns, and determinants of host-parasite association contributes to filling knowledge gaps in both community and disease ecology. Despite being targeted as a relevant group for conservation efforts, determinants of the association of amphibians and their parasites in broad scales are poorly understood. Here we describe parasite biodiversity in South American amphibians, testing the influence of host body size and geographic range in helminth parasites species richness (PSR). We also test whether parasite diversity is related to hosts' phylogenetic diversity. Results showed that nematodes are the most common anuran parasites. Host-parasite network has a nested pattern, with specialist helminth taxa generally associated with hosts that harbour the richest parasite faunas. Host size is positively correlated with helminth fauna richness, but we found no support for the association of host geographic range and PSR. These results remained consistent after correcting for uneven study effort and hosts' phylogenic correlation. However, we found no association between host and parasite diversity, indicating that more diversified anuran clades not necessarily support higher parasite diversity. Overall, considering both the structure and the determinants of PRS in anurans, we conclude that specialist parasites are more likely to be associated with large anurans, which are the ones harbouring higher PSR, and that the lack of association of PSR with hosts' clade diversification suggests it is strongly influenced by ecological and contemporary constrains.
Asunto(s)
Anuros/parasitología , Helmintos/clasificación , Helmintos/aislamiento & purificación , Animales , Tamaño Corporal , Helmintos/fisiología , Especificidad del Huésped , Interacciones Huésped-Parásitos , Filogenia , Filogeografía , América del SurRESUMEN
Home-range is the area used by an animal in its daily activities. Home-range studies provide data on species mating systems and territorial behavior. Our main goal was to estimate the Didelphis albiventris (Lund 1840) home-range in Mutum Island, Paraná River, Brazil. The study was carried out in 2008 from March to October on a 19.20 ha grid. The island is part of the Parana River Islands and Floodlands Federal Environmental Protection Area, with vegetation composed by Alluvial Semideciduous Seasonal Forest in a region of Subtropical Wet climate. The sampling effort was 3,360 traps-night resulting in 152 Didelphis albiventris (Lund 1840) captures. Forty-one Didelphis albiventris (Lund 1840) individuals were captured in 42 capture stations, composed by a trap placed on the floor and another in understory (2 m high). The animals were mostly terrestrial, independently of age or sex. Four females and five males, which were recaptured at least five times, were used to calculate home-range using the minimum convex polygon method. The mean home-range estimate was 2.33 ± 2.32 ha, similar to previous estimates provided by other methods, suggesting that our capture grid area, that was larger than usually applied for mark-capture studies for this species, have not underestimated the home-ranges. Evidences of the relation between individual home-range area and body mass were observed. Home-range overlaps occurred between males, females and males with females; the average overlap was 33.74%, which may be related to a promiscuous mating system, and suggests female territoriality.
Área de vida é a área usada por um animal em suas atividades diárias. Estudos de área de vida oferecem dados sobre os sistemas reprodutivos e comportamento territorial das espécies. Nosso objetivo foi estimar a área de vida de Didelphis albiventris (Lund 1840) na ilha Mutum, no rio Paraná, Brasil. O estudo foi realizado em 2008 de março a outubro em uma grade de 19,20 ha. Esta ilha é parte da área de proteção de ilhas e várzeas do rio Paraná e sua vegetação é composta por floresta estacional semidecidual aluvial sazonal com clima subtropical úmido. O esforço amostral foi de 3.360 armadilhas-noite resultando em 152 capturas de Didelphis albiventris (Lund 1840). Foram capturados 41 indivíduos nas 42 estações compostas por uma armadilha no solo e a dois metros de altura. A maioria dos animais foi capturada no solo, independente de idade ou sexo. Quatro fêmeas e cinco machos foram recapturados pelo menos cinco vezes e foram usados para calcular a área de vida mediante método de polígono mínimo convexo. A área de vida média estimada foi de 2,33 ha ± 2,32, similar às estimativas previamente descritas por outros métodos, sugerindo que o tamanho da grade de captura, maior que a usualmente empregada em estudos de marcação-recaptura com esta espécie, não subestimou as áreas de vida. Evidências da relação entre a área de vida e massa corporal dos indivíduos foram observadas. Sobreposição das áreas de vida (média = 33,74%) ocorreu entre machos, entre fêmeas e de machos com fêmeas, o que pode ser relacionado a um sistema de acasalamento promíscuo e territorialidade de fêmeas.
RESUMEN
The presence of buds, flowers, and fruits increases structural complexity in plants, but can also attract potentialprey for predators, thus determining faunistic composition. To understand how a spider assemblage living in the shrub Byrsonima intermedia (Malpighiaceae) varies with habitat structure in terms of reproductive elements and height of plant,we collected spider specimens and measured bud, flower, fruit, and leaf masses of 44 plants, as well as their height. Spider family composition was found to depend on habitat structure, following a pattern of family turnover occurring along gradients of reproductive plant elements and height, regardless of plant biomass. Theridiidae occurred in samples with themajor proportions of buds and flowers, while Oxyopidae occurred only in samples with major proportions of fruits.Multiple linear regression revealed the strong relation between the composition in reproductive plant elements and thecomposition in families of spiders and a relation between shrub height and spider family composition. These results help us to understand the temporal dynamics between structural complexity of vegetation and spider assemblages, because during plant phenology the proportions of reproductive elements are also varying.