Trophic guilds of suction-feeding fishes are distinguished by their characteristic hydrodynamics of swimming and feeding

Suction-feeding in fishes is a ubiquitous form of prey capture whose outcome depends both on the movements of the predator and the prey, and on the dynamics of the surrounding fluid, which exerts forces on the two organisms. The inherent complexity of suction-feeding has challenged previous efforts to understand how the feeding strikes are modified when species evolve to feed on different prey types. Here, we use the concept of dynamic similarity, commonly applied to understanding the mechanisms of swimming, flying, walking and aquatic feeding. We characterize the hydrodynamic regimes pertaining to (i) the forward movement of the fish (ram), and (ii) the suction flows for feeding strikes of 71 species of acanthomorph fishes. A discriminant function analysis revealed that feeding strikes of zooplanktivores, generalists and piscivores could be distinguished based on their hydrodynamic regimes. Furthermore, a phylogenetic comparative analysis revealed that there are distinctive hydrodynamic adaptive peaks associated with zooplanktivores, generalists and piscivores. The scaling of dynamic similarity across species, body sizes and feeding guilds in fishes indicates that elementary hydrodynamic principles govern the trophic evolution of suction-feeding in fishes.

Birds of Parque Estadual Ilha do Cardoso: ecology, conservation and natural history

The Parque Estadual Ilha do Cardoso (PEIC), located on extreme South of São Paulo’s cost, in Brazil, holds an important Atlantic Forest remnant which still in a good state of conservation, but lack a deepen study about the avian community that habits the island. This study aimed to elaborate a census of avian species that occur in the park approaching richness, occurrence frequency, occurrence status and the structure of trophic guilds. A total of 25 field expedictions occurred between September 2015 and September 2017 during five days each, the field work included different ecosystems as mangrove, restinga, forest, sandbank, beach and marine. The census was made combine three different techniques used in ornithological studies: visual identification, auditory identification and catch by mist-nets (with five fixed sites in mangrove, restinga and forest). Were recorded 335 avian species, with 28 of them endemic from Brazil and 33 being threatened with extinction. Seventy-three species were recorded in all sampled months (FO 100%), while 46 were recorded in just one month (FO = 4%). About occurrence status, 55% of species are residents, 20% occasional visitors, 13% unusual residents, 6% migratory and 6% visitors. According the recorded species were recognized 25 trophic guilds based on food items, corporal size and strata that commonly forage, which of most representative in the community, the guild of “of insectivorous of medium-strata” (N = 55), “canopy omnivorous” (N = 33), “aquatic invertebrates consummers” and “piscivorous” (N = 31). Finally, with the current study, we aimed through a significative field effort bring a better knowledge about avifauna of PEIC, which could be a good base when is necessary take actions that aim to park management and the Conservation Unities around it.

Diet composition of abundant fish species in the shallow waters of the Todos os Santos Bay, Bahia, Brazil

Coastal habitats have great ecological importance with estuarine environments providing feeding sites for many fish species, especially during juvenile life stages. This study investigates the diet composition and trophic guild organization of the common and abundant ichthyofauna in shallow areas of the Todos os Santos Bay (TSB), Bahia, Brazil, and their relationships with environmental parameters. Six fish sampling campaigns were carried out in the shallow zones (infralittoral) of the Paraguaçu River estuary which encompasses the inner and outer (marine exposure) reaches of the TSB. The stomach contents of 1231 individuals belonging to common and abundant species were examined. A total of 32 food items were identified and fish were into four trophic guilds: detritivores, zoobenthivores I, zoobenthivores II, and zooplanktivores. The relationship between the guilds and environmental parameters showed that zoobenthivores II and zooplanktivores guilds had a positive relationship with salinity and pH, explaining 86% of data variability, though only the salinity variable was significant. This study provides basic information about the diet composition of common and abundant species in the TSB and their organization into trophic guilds. In addition, demonstrates that shallow waters fish across all guilds have broadly similar diets, comprising food items that are usually associated with bottom waters.

The non-random structure of multi-trophic ecological interactions maximizes species coexistence within ecologically realistic constraints

Theory posits that the persistence of species in ecological communities is shaped by their interactions within and across trophic levels. However, we lack empirical evaluations of how the structure, strength and sign of these interactions drive the potential to coexist in diverse multi-trophic communities. Here we model community feasibility domains, a theoretically-informed measure of coexistence probability, from empirical data on communities comprising more than 50 species for three trophic guilds (plants, pollinators, and herbivores). Although feasibility domains vary depending on the number of trophic guilds considered, we show that higher network connectance leads to lower coexistence opportunities. Moreover, empirical estimations of the feasibility domains were higher with respect to random network structures but lower than a mean-field approach, suggesting that observed interaction structures tend to maximize coexistence within its imposed limits. Our results stress the importance of incorporating empirically-informed interaction structures within and across guilds to better understand how species coexist in diverse multi-trophic communities.

Ant diversity and abundance in pasture system and two agricultural land uses in the Rashad district, Southern Sudan

The most common ecological consequence of biodiversity loss is a reduction in ecosystem functions. These responses, however, vary depending on the type of land-use change and the ecological setting. This study investigated the impact of land-use type and ecosystem functions on the ant assemblage of Rashad district, Sudan. Therefore, the purposes of this study are to evaluate the composition and structure of the ant assembly in the station, as well as to determine the trophic guilds and functional groups and their spatial variation in three different land uses. Furthermore, based on the type of land use to determine how the conversion of native vegetation affects the richness and composition of ant species. In each location, we sampled three 20-meter-long transects (Sample plot). Each sample plot consisted of a grid of 12 pitfall traps arranged in three rows of four traps each, with a 2 m spacing between them, replicated six times in a single year. We collected 38 ant species from four subfamilies and 17 genera. Parasyscia lamborni was the most abundant species followed by Bothroponera crassa. Ant diversity was higher in Soy monoculture and Organic farming than in the Pasture. The frequency distributions of ant Functional groups in Soy monoculture and Organic farming were significantly different from the frequency distributions in the pasture. The omnivorous and predator’s trophic guilds were the best represented and regarding functional groups. We found a high proportion of tropical climate specialists and Myrmicinae generalists. These findings suggest that Pasture Activation reduces ant diversity. It can also help to increase the population of species with a diverse diet that predominate in areas where stress and disturbance prevent other ants from reproducing.

Characterization of assemblages in neotropical cave dwelling bats based on their diet, wing morphology, and flight performance

Bats have a great variety of wing morphologies that determines the bat’s flight performance, and this in turn conditions the forage aerosphere and the food it can obtain. Several studies have shown differences in wing morphology, flight performance, and forage aerospheres among species from different trophic guilds. However, for species that share a guild this is not entirely clear. It is possible that these species have differences in their diet and show changes in wing morphology that modify their flight performance and forage areas. Determining this will allow a better understanding of spatial segregation among species that share a trophic guild. These studies allow the identification of species assemblages based on wing morphological differences and flight performance that would not be distinguished only by guild membership. Our goal was to define the species assemblages that make up a community of Neotropical cave dwelling bats based on their trophic guild, flight performance, and forage zone. A community of Neotropical cave dwelling bats from a cave in Veracruz, Mexico was analyzed. The diet of each species was determined by means of their stomach contents and bibliographic review. In addition, aspect ratio, wing loading and tip index were calculated. Based on the wing characteristics and diet, multivariate groupings and orders were performed, as well as to define the assemblages present. According to the wing characteristics and the dietary composition, four groups of species were found that represent four different flight characteristics in terms of agility and maneuverability. There was agreement between diet and wing characteristics, and the four trophic groups were identified through canonical correspondence analysis. Correlating wing morphology, diet and forage area allows us to adequately define the assemblages of a community of bats. Regarding the hypothesis, it was found that species that share a food guild show differences in the composition of their food and wing morphology, which generate differences in flight performance and forage areas. Four assemblages differing in forage aerospheres among three trophic guilds are described: understory and facultative artrhopodivorous, semi-clearing hematophages, and facultative nectarivores. Finally, spatial segregation between the species of the families Mormoopidae and Natalidae was recognized.

Effect of the matrix-edge-forest interior gradient on the phyllostomid bats assemblage in sub-Andean forest fragments

The edge effect is one of the consequences of forest fragmentation and is one of the main drivers of alteration of ecological and ecosystem processes. Trophic guilds and species of bats have shown differential responses to this phenomenon. Our goal was to describe the change in bat species richness, abundance, evenness, and species composition of trophic guilds associated with a matrix edge-forest interior gradient. Therefore, we conducted a bat sampling with 16 mist nets covering such gradient in four sub-andean forest fragments (10-50 ha). In total, we captured 566 individuals of 21 species of phyllostomid bats. Bat species richness and abundance were higher in the matrix and edge and were similar between fragments. Evenness showed the lowest values in the matrix and forest edge and was different between forest patches. Some shrub frugivorous bats were more abundant in the edge, and others were more abundant in two fragments. Species composition of canopy frugivorous bats was similar along the gradient but was significantly different between fragments. In contrast, the species composition of nectarivores was similar throughout the matrix-interior forest gradient and between patches. Our data suggest that bat responses at assemblage-level are affected by the disturbance gradient from the matrix to forest interior, even at short distances form fragment borders, and are dependent on the trophic guild.

Macrobenthic community of an estuarine tidal flat on the Amazon coast: spatial variations and presence of polychaetes tubes

The present study characterized the macrobenthic fauna found on a muddy-sandy tidal flat of the Amazon coast in areas with and without the presence of Diopatra cuprea (Bosc, 1802) (Onuphidae: Annelida) tubes. In addition, a brief review of records of D. cuprea on the Brazilian Amazon coast is presented. Samples were collected in February 2014 in two different areas: (1) an area in which D. cuprea tubes were present, and (2) a control area, in which worm tubes were absent. A total of 21 taxa were found, of which 10 were associated exclusively with D. cuprea tubes. Although richness did not vary significantly among areas, there were changes in the abundance and composition of species and trophic guilds. In the area with tubes, there was a higher abundance of filter-feeders and the presence of species adapted to consolidated and muddy substrates. Our results and those of other studies indicate that D. cuprea commonly presents low density in the Amazon coastal, and its tubes are typically scattered widely in the intertidal zone. The present findings add knowledge about the presence of the bioconstructor in coastal areas and reinforce the role of tube-building polychaetes as ecosystem engineers.