Birds foraging for fruits and insects in shrubby restinga vegetation, southeastern Brazil

Revisiting phylogeny, systematics, and biogeography of a Pleistocene radiation

PREMISE

Pilosocereus (Cactaceae) is an important dry forest element in all subregions and transitional zones of the neotropics, with the highest diversity in eastern Brazil. The genus is subdivided into informal taxonomic groups; however, most of these are not supported by recent molecular phylogenetic inferences. This lack of confidence is probably due to the use of an insufficient number of loci and the complexity of cactus diversification. Here, we explored the species relationships in Pilosocereus in more detail, integrating multilocus phylogenetic approaches with the assessment of the ancestral range and the effect of geography on diversification shifts.

METHODS

We used 28 nuclear, plastid, and mitochondrial loci from 54 plant samples of 31 Pilosocereus species for phylogenetic analyses. We used concatenated and coalescent phylogenetic trees and Bayesian models to estimate the most likely ancestral range and diversification shifts.

RESULTS

All Pilosocereus species were clustered in the same branch, except P. bohlei. The phylogenetic relationships were more associated with the geographic distribution than taxonomic affinities among taxa. The genus began diversifying during the Plio-Pleistocene transition in the Caatinga domain and experienced an increased diversification rate during the Calabrian age.

CONCLUSIONS

We recovered a well-supported multispecies coalescent phylogeny. Our results refine the pattern of rapid diversification of Pilosocereus species across neotropical drylands during the Pleistocene and highlight the need for taxonomic rearrangements in the genus. We recovered a pulse of diversification during the Pleistocene that was likely driven by multiple dispersal and vicariance events within and among the Caatinga, Cerrado, and Atlantic Forest domains.

Fruit Size and Structure of Zoochorous Trees: Identifying Drivers for the Foraging Preferences of Fruit-Eating Birds in a Mexican Successional Dry Forest

Simple Summary

Tropical dry forests are highly threatened by human activities such as agriculture, livestock, and selective logging. These activities have resulted in fragments of tropical dry forest under different successional stages that negatively affect the interaction between plants and fruit-eating birds. We analyzed the consumption of the fruits of zoochorous trees by birds during the dry season in a tropical dry forest and evaluated whether the horizontal and vertical structure of these trees explains fruit consumption. We also related the bird body mass and fruit size removed from zoochorous trees. We found that the tree structure can influence the visitation of fruit-eating birds, and therefore, the number of fruits consumed as the succession progresses. There was a relationship between fruit sizes and bird body mass in the successional gradient. Our results indicate that structural and fruit traits of zoochorous trees drive foraging preferences of fruit-eating birds, whose interactions in different successional stages can help to reverse the negative effects of fragmentation in tropical dry forests of the study area.

Abstract

Tropical dry forests (TDFs) are affected by land-use changes. These modifications impact their composition and arboreal structure, as well as the availability of food for several bird groups. In this study, we evaluated the foraging preferences in zoochorous trees of fruit-eating birds during the dry season of the year in three successional stages (early, intermediate, and mature) of TDFs in southern Mexico. The fruits of these trees are important in the diet of several birds during the dry season, a period during which food resources are significantly reduced in TDFs. We estimated foliar cover (FC) and foliage height diversity (FHD) of zoochorous trees in 123 circular plots. These variables were recognized as proxies of food availability and tree productivity. Foraging preferences were evaluated at the community level, by frugivore type, and by bird species. We evaluated the effect of the structural variables and the fruit size of zoochorous plants on fruit removal by birds and related the bird body mass and fruit size removed in the successional gradient. A total of 14 zoochorous tree species and 23 fruit-eating bird species were recorded along the successional gradient. Intermediate and mature stages showed greater fruit removal. The birds removed mainly B. longipes fruits across the three successional stages. The FHD and fruit size were important drivers in the selection of zoochorous trees and fruit removal by fruit-eating birds. Fruit size and bird body mass were positively related along the successional gradient. The results suggest that fruit removal by fruit-eating birds in the successional gradient can promote the demographic dynamics of several zoochorous tree species, especially of Bursera spp. along the TDFs.

Floristic influence of Amazonian Lowland Dense Rain Forest on the pioneer vegetation with marine influence, Restinga of Pará state, Brazil

Abstract The coastal region of the municipalities of Curuçá and Maracanã, on the northeastern coast of Pará, shelters a valuable biological heritage, the last two remnants of Dense Rain Forest on the shores of the Atlantic Ocean. On the Ipomonga Island (Curuçá) and at the Marieta Beach (Maracanã), the Lowland Dense Rain Forest is notable for its abrupt contact with the pioneer formation with marine influence, called as Restinga. This geomorphological interface favors floristic connectivity between different ecosystems. The research objective was to evaluate, through vegetation inventories, whether these forests remnants, about Lowland Dense Rain Forest, are sources of dispersal of woody species in Restinga. A total of 189 species were recorded in 50 botanical families with the greatest richness corresponds to the dense forest (67 species). Of this flora, 46 species (24%) were common to both vegetation typologies, with 18 species considered new occurrences in Restinga of the Amazonian coastal plains. The floristic affinities founded support the effect of Lowland Dense Rain Forest acting as the source for propagule dispersion over the pioneer formation with marine influence (Restinga), mostly dispersed by animals (zoocory).

Trophic niche similarities of sympatric Turdus thrushes determined by fecal contents, stable isotopes, and bipartite network approaches

An ecological niche has been defined as an n-dimensional hypervolume formed by conditions and resources that species need to survive, grow, and reproduce. In practice, such niche dimensions are measurable and describe how species share resources, which has been thought to be a crucial mechanism for coexistence and a major driver of broad biodiversity patterns. Here, we investigate resource partitioning and trophic interactions of three sympatric, phylogenetically related and morphologically similar species of thrushes (Turdus spp.). Based on one year of data collected in southern Brazil, we investigated niche partitioning using three approaches: diet and trophic niche assessed by fecal analysis, diet and niche estimated by stable isotopes in blood and mixing models, and bipartite network analysis derived from direct diet and mixing model outputs. Approaches revealed that the three sympatric thrushes are generalists that feed on similar diets, demonstrating high niche overlap. Fruits from C3 plants were one of the most important food items in their networks, with wide links connecting the three thrush species. Turdus amaurochalinus and T. albicollis had the greatest trophic and isotopic niche overlap, with 90% and 20% overlap, respectively. There was partitioning of key resources between these two species, with a shared preference for fig tree fruits-Ficus cestrifolia (T. amaurochalinus PSIRI% = 11.3 and T. albicollis = 11.5), which was not present in the diet of T. rufiventris. Results added a new approach to the network analysis based on values from the stable isotope mixing models, allowing comparisons between traditional dietary analysis and diet inferred by isotopic mixing models, which reflects food items effectively assimilated in consumer tissues. Both are visualized in bipartite networks and show food-consumers link strengths. This approach could be useful to other studies using stable isotopes coupled to network analysis, particularly useful in sympatric species with similar niches.

The Dispersion of Diaspores of Protium icicariba (Burseraceae) - a Networked or Multifactorial System?

The adaptive radiation of the angiosperms was strongly affected by fruit and seed dispersal since the establishment of the seedlings is a fundamental process for the recruitment of juveniles to the populations. Among the species of Burseraceae, seeds with fleshy attachments and high caloric value suggest mammaliochory as an ancestral dispersal way. In Protium icicariba, at the same time as there is a visual pattern typical of ornithochory, with a report of effective demonstration, the diaspores present the highest levels of essential oils of the whole plant, suggesting other dispersion processes by olfactory guided vectors. This work aims to monitor the diasporic dispersal process in P. icicariba in situ, aiming to identify dispersers and to investigate the role of the essential oil in the dispersion of diaspores of this plant species. The natural dispersion was monitored in situ, in weekly campaigns throughout eight months, using visual and photographic records, in daily shifts of six hours, distributed along the dawn, morning, afternoon, dusk, and night. We used both direct observation and continuous picture capturing along 43 days with photographic traps. Mature diaspores removed from pseudocapsules were pooled to determine potential dispersers. Artificial models of the diaspores, in white and green colors, were also used to test hypotheses on the role of scent in the dispersion, added 1%, weight/weight, of the essential oil extracted from the mature diaspores, which chemical composition determined by gas chromatography coupled to mass spectrometry. Besides, the analysis of stomach contents of lizards collected in adjacent area was also performed. In daytime and nighttime monitoring in nature, no vertebrates were recorded dispersing diaspores. The most common was the primary wind-facilitated autochory of diaspores to the substrate, near the plant matrices. Secondarily, workers of the ant species Atta robusta can remove the pseudoarils or move the pyrenes to the anthills. The lizard species Tropidurus torquatus ingests pyrenes with the pseudoarils, and the sclerified pericarp of the pyrene is potentially resistant to chemical action of the digestive juices. Ants and lizards have also accessed the caves with natural diaspores. Concerning the artificial diaspore models, ants accessed, indistinctly, white and the green models that contained essential oils. The lizards accessed the white models, with or without essential oils, and showed insignificant access to green ones, with or without essential oil. The ingestion of pyrenes by lizards was also confirmed through analysis of stomach contents. The aggregate spatial pattern of P. icicariba at the study site, associated with clumps, may be derived from germination in the substrate near the matrices, or in the anthills or after diaspora defecation and / or regurgitation of the lizard, which is a species strongly associated with clumps of this vegetation. As the access to the diaspores by ants and lizards depends on the primary autochory, and no impediments to the germination near to the matrix plant were found, the dispersion is compatible with a multifactorial characteristic of the diplochory.

Pervasive migration across rainforest and sandy coastal plain Aechmea nudicaulis (Bromeliaceae) populations despite contrasting environmental conditions

Understanding the colonization of extreme marginal habitats and the relative roles of space and environment in maintaining peripheral populations remains challenging. Here, we leverage a system of pairs of rainforest and sandy coastal plain communities that allow us to decouple spatial and environmental effects in the population structure and migration rates of the bromeliad Aechmea nudicaulis. Structure and gene flow between populations were estimated from Bayesian clustering and coalescent-based migration models applied to chloroplast sequence and nuclear microsatellite data. Contrary to our initial expectation, the sharp environmental gradient between rainforest and sandy plains does not seem to have affected the colonization and migration dynamics in A. nudicaulis. Our analyses uncover pervasive gene flow between neighbouring habitats in both chloroplast and nuclear data despite the striking differences in environmental conditions. This result is consistent with a scenario of repeated colonization of the sandy coastal plains from forest populations through seed dispersal, as well as the maintenance of gene flow between habitats through pollination. We also recovered a broad north/south population structure that has been found in other Atlantic rainforest groups and possibly reflects older phylogeographic dynamics.

O estado do Rio de Janeiro como limite sul e norte de distribuição de algumas espécies de aves

A região onde se localiza o estado do Rio de Janeiro pode ser considerada biogeograficamente importante por abrigar os limites geográficos extremos da Serra do Mar e das florestas dos tabuleiros (ou de baixada), formações bastante significativas para a distribuição de diversas espécies de aves. Nesse estudo, através de extensa consulta bibliográfica, foram encontradas 59 espécies de aves com seu limite sul (40 espécies) ou norte (19 espécies) de distribuição geográfica localizado no estado do Rio de Janeiro. As espécies com limite sul de distribuição no estado têm registros em quase todo o território fluminense, exceto na região do alto vale do rio Paraíba do Sul e na porção mais ocidental da costa fluminense. São espécies predominantemente associadas às florestas de baixada e submontanas e mais da metade está incluída na lista de espécies ameaçadas de extinção do estado. As espécies com limite norte de distribuição no Rio de Janeiro podem ser classificadas em dois grupos básicos quanto ao seu padrão de distribuição em território fluminense. O primeiro grupo é composto por espécies de ambientes florestais montanos e endêmicas da Mata Atlântica, enquanto o segundo grupo é constituído por visitantes ocasionais associados a ambientes aquáticos. A baixa representatividade de espécies ameaçadas entre aquelas com limite norte de distribuição no Rio de Janeiro pode ser explicada pela elevada proporção, entre suas espécies florestais, de representantes de matas serranas, melhor preservadas que as matas de baixada.