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Background. Ecological communities are dynamic collections whose composition and structure change over time, making up complex interspecific interaction networks. Mutualistic plant–animal networks can be approached through complex network analysis; these networks are characterized by a nested structure consisting of a core of generalist species, which endows the network with stability and robustness against disturbance. Those mutualistic network structures can vary as a consequence of seasonal fluctuations and food availability, as well as the arrival of new species into the system that might disorder the mutualistic network structure (e.g., a decrease in nested pattern). However, there is no assessment on how the arrival of migratory species into seasonal tropical systems can modify such patterns. Emergent and fine structural temporal patterns are adressed here for the first time for plant-frugivorous bird networks in a highly seasonal tropical environment.Methods. In a plant-frugivorous bird community, we analyzed the temporal turnover of bird species comprising the network core and periphery of ten temporal interaction networks resulting from different bird migration periods. Additionally, we evaluated how fruit abundance and richness, as well as the arrival of migratory birds into the system, explained the temporal changes in network parameters such as network size, connectance, nestedness, specialization, interaction strength asymmetry and niche overlap. The analysis included data from 10 quantitative plant-frugivorous bird networks registered from November 2013 to November 2014.Results. We registered a total of 319 interactions between 42 plant species and 44 frugivorous bird species; only ten bird species were part of the network core. We witnessed a noteworthy turnover of the species comprising the network periphery during migration periods, as opposed to the network core, which did not show significant temporal changes in species composition. Our results revealed that migration and fruit richness explain the temporal variations in network size, connectance, nestedness and interaction strength asymmetry. On the other hand, fruit abundance only explained connectance and nestedness.Discussion. By means of a fine-resolution temporal analysis, we evidenced for the first time how temporal changes in the interaction network structure respond to the arrival of migratory species into the system and to fruit availability. Additionally, few migratory bird species are important links for structuring networks, while most of them were peripheral species. We showed the relevance of studying bird–plant interactions at fine temporal scales, considering changing scenarios of species composition with a quantitative network approach.

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The main objective of this study was to analyze the relationship between population densities of the white-tailed deer Odocoileus virginianus and certain habitat and human characteristics in the tropical dry forest of the Tehuacan-Cuicatlan Biosphere Reserve (TCBR), Mexico. To estimate population density and characterize the habitat, we established 32 strip transects (500 x 2 m) at four different locations in the TCBR from May to June during the dry season of 2010. Principal component analyses were used to order the 32 transects using habitat/human impact variables and tree species composition. Estimated average density was 1.7 deer/km 2 , ranging from 0.1 to 2.9 deer/km 2 . The variables associated with white-tailed deer density were: basal area, distance to roads, distance to the area with largest human population, slope, aspect and presence of cattle; the principal plant species were Zapotillo (Lantana camara), Chintoborrego (Vallesia glabra), Nanche (Bunchosia biocellata), Cuachalalate (Amphipterigyum adstringens) and Cuajiote Amarillo (Bursera aptera). Compared to other tropical dry forests, estimated white-tailed deer densities in the TCBR were lower. We discuss the possible effect of these variables on deer density and suggest management actions.Key Word: Odocoileus virginianus, pellet-groups count, human influence, management. ResumenEl objetivo principal de este estudio fue analizar la relación entre la densidad poblacional del venado cola blanca Odocoileus virginianus con algunas características del hábitat en el bosque tropical seco de la Reserva de la Biosfera de Tehuacán-Cuicatlán (TCBR), México. Para estimar la densidad y caracterizar el hábitat, se colocaron 32 transectos de franja (500 x 2 m) en cuatro diferentes localidades de la TCRB de mayo a junio de 2010. Se llevaron a cabo análisis de componentes principales para ordenar los 32 transectos conforme a las variables del hábitat, impacto humano y su composición vegetal. La densidad promedio fue de 1.7 venados/km 2 , con una variación entre de 0.1 a 2.9 venados/km 2 . Las variables relacionadas con la densidad del venado fueron el área basal, la distancia a caminos, la distancia a la localidad con mayor número de habitantes, la orientación y la presencia de ganado. En las localidades con mayor densidad de venados las plantas dominantes fueron Zapotillo (Lantana camara) Chintoborrego (Vallesia glabra), Nanche (Bunchosia biocellata, Cuachalalate (Amphipterigyum adstringens) y Cuajiote Amarillo (Bursera aptera). Comparado con otros bosques tropicales, las densidades estimadas en la TCBR fueron menores. Se discute el posible efecto de estas variables sobre la densidad del venado y se sugieren algunas acciones de manejo.Palabras clave: Odocoileus virginianus, conteo de grupos fecales, influencia humana, manejo.

Interactions between fleshy fruited plants and frugivores are crucial for the structuring and functioning of biotic communities, particularly in tropical forests where both groups are diverse and play different roles in network organization. However, it remains poorly understood how different groups of frugivore species and fruit traits contribute to network structure. We recorded interactions among 28 plant species and three groups of frugivores (birds, bats, and non-flying mammals) in a seasonal forest in Mexico to determine which species contribute more to network structure and evaluate the importance of each species. We also determined whether fruit abundance, water content, morphology traits, and fruiting phenology are related to network parameters: the number of interactions, species contribution to nestedness, and species strength. We found that plants did not depend on a single group of frugivores, but rather on one species of each group: the bird Pitangus sulphuratus, the bat Sturnira parvidens, and the non-flying mammal Procyon lotor. The abundance, size, and water content of the fruits were significantly related to the contribution to nestedness, number of interactions, and species strength index of plant species. Tree species and birds contributed mainly to the nested structure of the network. We show that the structure of plant-frugivore networks in this seasonal forest is non-random and that fruit traits (i.e., abundance, phenology, size, and water content) are important factors shaping plant-frugivore networks. Identification of the key species and their traits that maintain the complex structure of species interactions is therefore fundamental for the integral conservation of tropical forests.