Caracterização dos frutos, sementes e plântulas de espécies de Clusiaceae das restingas do Rio de Janeiro

No presente trabalho foi estudada a morfologia dos frutos, sementes e plântulas de cinco espécies de Clusiaceae presentes em vegetação de restinga do estado do Rio de Janeiro. Os frutos das espécies estudadas apresentam características ligadas à zoocoria (Clusia fluminensis, C. lanceolata, C. criuva e Garcinia brasiliensis) e à anemocoria (Kielmeyera membranacea). As sementes recém-coletadas apresentam altas taxas de germinação: C. fluminensis (100%), C. lanceolata (100%), C. criuva (99,2%), G. brasiliensis (90,45%) e K. membranacea (91%). A germinação fanerocotiledonar foi registrada em C. fluminensis, C. lanceolata, C. criuva e K. membranacea e criptocotiledonar em G. brasiliensis. Plântulas de espécies de Clusia são frequentemente encontradas no habitat natural, especialmente associadas a espécies de Bromeliaceae, que funcionam como plantas-berçário

Feeding ecology of Tropidurus torquatus (Wied) (Squamata, Tropiduridae) in two areas with different degrees of conservation in Marambaia Island, Rio de Janeiro, Southeastern Brazil

We compared the effects of habitat disturbance on the feeding ecology of two local populations of Tropidurus torquatus (Wied, 1820) in restinga habitats on Ilha da Marambaia, Southeastern Brazil. Both populations presented a relatively diverse diet and differ in the number (D Max = 0.22, DF = 2, p = 0.00) and volume of prey consumed (D Max = 0.82, DF = 2, p = 0.00). Ants were the most frequent and numerous preys in both areas, and plant matter and coleopterans were the most important alimentary items in volume. The population from the disturbed area presented a larger niche breadth for number of prey items consumed (Bi num = 3.06) and volume (Bi vol = 2.98), when compared to the other population (Bj num = 2.44, Bj vol = 1.52). Niche overlap was higher for number of items consumed between the populations (Oij num = 0.82) but lower for volume (Oij vol = 0.05). Our data suggest dietary differences between the two lizard populations, and these differences may be associated with environmental modifications. Our main hypothesis to explain the dietary differences is based in the Optimal Foraging Theory. However, the alimentary behavior, and consequently the diet of these lizards, seems to be constrained phylogenetically, with a pattern that may have evolved in the ancestor of all iguanids.<br>Comparamos os efeitos da degradação ambiental sobre a ecologia alimentar de duas populações de Tropidurus torquatus (Wied, 1820) em áreas de restinga da Ilha da Marambaia, sudeste do Brasil. Ambas as populações apresentaram dieta relativamente diversa e deferiram em número (D Max = 0,22; DF = 2; p = 0,00) e volume de presas consumidas (D Max = 0,82; DF = 2; p = 0,00). Formigas foram os itens mais freqüentes e numerosos em ambas as áreas, e material vegetal e coleópteros os mais importantes em volume. A população da área perturbada apresentou maior largura de nicho alimentar para número de presas consumidas (Bi num = 3,06) e volume (Bi vol = 2,98), quando comparada à outra população (Bj num = 2,44; Bj vol = 1,52). A sobreposição de nicho foi mais marcante para o número de itens consumidos entre as populações (Oij num = 0,82) e menos marcante para volume (Oij vol = 0,05). Nossos dados sugerem diferenças nas dietas entre as duas populações de lagartos, e estas diferenças parecem estar associadas à degradação ambiental. Nossa principal hipótese para explicar as diferenças nas dietas embasa-se na Teoria do Forrageamento Ótimo. Entretanto, o comportamento alimentar, e conseqüentemente a dieta dos lagartos, mostrarem-se limitadas filogeneticamente, com um padrão que pode ter evoluído no ancestral de todos os iguanídeos

Influence of life history traits on trophic niche overlap between two similar sympatric Tupinambis lizards

Segregation of habitat resources is an important mechanism that allows the coexistence of species. The diet is an important and dynamic component that can generate interactions among co-existing species. Differences in food resource use between related sympatric species have been associated frequently with divergence in multiple phenotypic traits; hence, it is interesting to explore how phenotypic differences allow sympatric species to minimize niche overlap. We aimed to evaluate trophic niche segregation between Tupinambis merianae and T. rufescensin relation to life history traits in a sympatric zone. We compared the volume of the stomach food items between species considering sexual dimorphism, body size classes, sexual maturity and reproductive activity. The obtained Morisita?s index indicated trophic niche overlap between T. merianaeand T. rufescens; however, considering particular food items, we observed differences in diet composition. Moreover, our results indicate that body size, sexual maturity and reproductive activity are relevant factors influencing the diet of these species. Life history traits of these two species of Tupinambisare important because they shape diet composition, contributing to interspecific segregation of the trophic niche and, therefore, allowing species coexistence.La segregación de los recursos del hábitat es un importante mecanismo que permite la coexistencia de especies. La dieta es un componente importante y dinámico, que puede generar interacciones entre especies co-existentes. Las diferencias en la dieta entre especies relacionadas en simpatría han sido frecuentemente asociadas a la divergencia en múltiples caracteres fenotípicos, por lo tanto es interesante explorar cómo las diferencias fenotípicas permiten que las especies simpátricas minimicen la superposición del nicho. Nuestro objetivo fue evaluar la segregación del nicho trófico entre Tupinambis merianae y T. rufescens en una zona de simpatría y entender de qué manera los caracteres de historia de vida podrían influenciar la ecología trófica de estos lagartos. Analizamos el contenido estomacal comparando el volumen de presas consumidas entre especies, considerando además el dimorfismo sexual, las clases de tamaño corporal, la madurez sexual y la actividad reproductiva. El índice de Morisita obtenido indica superposición del nicho trófico entre T. merianae y T. rufescens, pero considerando algunas presas en particular, observamos que las especies muestran diferencias en la composición de la dieta. Por otro lado, nuestros resultados indican que el tamaño corporal, la madurez sexual y la actividad reproductiva son factores relevantes que influyen en la dieta de las especies. Los caracteres de historia de vida de estas dos especies de Tupinambis son importantes porque determinan la composición de la dieta, contribuyendo a la segregación interespecifica del nicho trófico y en consecuencia a la coexistencia de las especies.Fil: López Juri, Guadalupe. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; ArgentinaFil: Naretto, Sergio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; ArgentinaFil: Mateos, Ana Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Chiaraviglio, Margarita. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; ArgentinaFil: Cardozo, Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; Argentin

Directional growth of a clonal bromeliad species in response to spatial habitat heterogeneity

Item does not contain fulltextHabitat selection by directional growth of plants has previously been investigated but field evidence for this phenomenon is extremely scarce. In this study we demonstrate directional clonal growth in Aechmea nudicaulis, a monocarpic, perennial bromeliad native to spatially heterogeneous sandy coastal plains (restinga) in Brazil. This habitat is characterized by a matrix of bare sand with interspersed vegetation islands. Due to very high soil surface temperatures and other stress factors such as drought, A. nudicauliscan only germinate inside vegetation islands. Nevertheless, this species is very common on bare sand. In this study we tested the hypothesis that clonal fragments occurring at the border and inside vegetation islands show habitat selection by growing preferentially towards the bare sand habitat (i.e. away from the center of vegetation islands). We randomly chose 116 clonal fragments in two distinct micro-environments (inside vegetation islands, and in the border area between bare sand and vegetation islands) in the natural habitat of A.nudicaulisand measured their growth direction in relation to the island center. We measured the growth directions of entire clonal fragments (defined as the line that connects the oldest and the youngest ramets of a clonal fragment) as well as the growth direction of the youngest internode on each fragment (the growth direction of the youngest ramet in relation to its parent ramet). We used Monte Carlo simulations to test for deviations from randomness in the growth direction of clonal fragments and individual internodes. The clonal fragments of A.nudicaulis showed a significant tendency to grow away from the center of vegetation islands. In other words, the main growth direction of clonal fragments growing inside vegetation islands or at the border between bare sand and vegetation islands was preferentially directed towards bare sand environments. Individual internodes at the border of vegetation islands also exhibited this tendency to grow towards the outside of vegetation islands, but internodes growing inside vegetation islands did not show directional growth. These results provide the first field evidence for habitat selection through directional growth of a clonal plant species