The Missing Part of Seed Dispersal Networks: Structure and Robustness of Bat-Fruit Interactions

Mutualistic networks are crucial to the maintenance of ecosystem services. Unfortunately, what we know about seed dispersal networks is based only on bird-fruit interactions. Therefore, we aimed at filling part of this gap by investigating bat-fruit networks. It is known from population studies that: (i) some bat species depend more on fruits than others, and (ii) that some specialized frugivorous bats prefer particular plant genera. We tested whether those preferences affected the structure and robustness of the whole network and the functional roles of species. Nine bat-fruit datasets from the literature were analyzed and all networks showed lower complementary specialization (H2' = 0.37±0.10, mean ± SD) and similar nestedness (NODF = 0.56±0.12) than pollination networks. All networks were modular (M = 0.32±0.07), and had on average four cohesive subgroups (modules) of tightly connected bats and plants. The composition of those modules followed the genus-genus associations observed at population level (Artibeus-Ficus, Carollia-Piper, and Sturnira-Solanum), although a few of those plant genera were dispersed also by other bats. Bat-fruit networks showed high robustness to simulated cumulative removals of both bats (R = 0.55±0.10) and plants (R = 0.68±0.09). Primary frugivores interacted with a larger proportion of the plants available and also occupied more central positions; furthermore, their extinction caused larger changes in network structure. We conclude that bat-fruit networks are highly cohesive and robust mutualistic systems, in which redundancy is high within modules, although modules are complementary to each other. Dietary specialization seems to be an important structuring factor that affects the topology, the guild structure and functional roles in bat-fruit networks

Barriers to gene flow and ring species formation

FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQRing species are groups of organisms that dispersed along a ring-shaped region in such a way that the two ends of the population that meet after many generations are reproductively isolated. They provide a rare opportunity to understand the role of spatial structuring in speciation. Here, we simulate the evolution of ring species assuming that individuals become sexually isolated if the genetic distance between them is above a certain threshold. The model incorporates two forms of dispersal limitation: exogenous geographic barriers that limit the population range and endogenous barriers that result in genetic structuring within the population range. As expected, species' properties that reduce gene flow within the population range facilitate the evolution of reproductive isolation and ring species formation. However, if populations are confined to narrow ranges by geographic barriers, ring species formation increases when local mating is less spatially restricted. Ring species are most likely to form if a population expands while confined to a quasi-unidimensional range but preserving high mobility in the direction of the range expansion. These conditions are unlikely to be met or persist in real populations and may explain why ring species are rare.Ring species are groups of organisms that dispersed along a ring-shaped region in such a way that the two ends of the population that meet after many generations are reproductively isolated. They provide a rare opportunity to understand the role of spatial structuring in speciation. Here, we simulate the evolution of ring species assuming that individuals become sexually isolated if the genetic distance between them is above a certain threshold. The model incorporates two forms of dispersal limitation: exogenous geographic barriers that limit the population range and endogenous barriers that result in genetic structuring within the population range. As expected, species' properties that reduce gene flow within the population range facilitate the evolution of reproductive isolation and ring species formation. However, if populations are confined to narrow ranges by geographic barriers, ring species formation increases when local mating is less spatially restricted. Ring species are most likely to form if a population expands while confined to a quasi-unidimensional range but preserving high mobility in the direction of the range expansion. These conditions are unlikely to be met or persist in real populations and may explain why ring species are rare.712442448FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ2010/10155-32016/06054-3302859/2011-

Occurrence of food items found in Didelphis aurita and Metachirus nudicaudatus fecal samples

The study was conducted in an Atlantic Rainforest area, in the Serra do Mar State Park (23°20’S and 44°50’W), southeast of Brazil (São Paulo State coast), at altitudes between 43 and 89m asl (Eisenlohr et al. 2013). A trapping session of four consecutive nights was conducted monthly from October 2013 to November 2014. In order to capture the animals, we used one hundred Tomahawk traps (45 x 16 x 16 cm) on the ground, baited with banana, peanut butter, and bacon. The traps were 20 m apart from each other, forming a 3.4 ha grid (280m x 120m). Individuals captured were marked in each ear with one 1g monel ear tag (National Band and Tag Co.®), weighted, and identified by sex and age (Tyndale-Biscoe and MacKenzie 1976). Samples of scats were collected from adults only. Scats were collected from the bottom of the trap where the animal spent the night. The traps were placed on a platform of hardboard in order to isolate the scats from litter. Feces samples were dissolved in water and then filtered through a 1mm mesh screen sieve under running tap water. Then the material retained on the sieve was dried at ambient temperature. This undigested material was analyzed with a stereoscope and the taxonomic classification of the prey items found was done by specialists. After one year of trapping sessions (48 nights of trapping, 4800 trap-nights) we recorded 35 individuals (i.e., adults and juveniles) of *Didelphis aurita* and 19 individuals of *Metachirus nudicaudatus*. In order to avoid differences in the diet samplings of individuals, only adult feces were taken. Thirty-eight fecal samples were collected from 18 adults of *D. aurita*, and 32 fecal samples were collected from 15 adults of *M. nudicaudatus*. Their diet items are described in Table 01

Impacts of enemy-mediated effects and the additivity of interactions in an insect trophic system

In this study, we used data from both experiments and mathematical simulations to analyze the consequences of the interacting effects of intraguild predation (IGP), cannibalism and parasitism occurring in isolation and simultaneously in trophic interactions involving two blowfly species under shared parasitism. We conducted experiments to determine the short-term response of two blowfly species to these interactions with respect to their persistence. A mathematical model was employed to extend the results obtained from these experiments to the long-term consequences of these interactions for the persistence of the blowfly species. Our experimental results revealed that IGP attenuated the strength of the effects of cannibalism and parasitism between blowfly host species, increasing the probability of persistence of both populations. The simulations obtained from the mathematical model indicated that IGP is a key interaction for the long-term dynamics of this system. The presence of different species interacting in a tri-trophic system relaxed the severity of the effects of a particular interaction between two species, changing species abundances and promoting persistence through time. This pattern was related to indirect interactions with a third species, the parasitoid species included in this study. © 2012 The Society of Population Ecology and Springer Japan