Regional and Fine Scale Variation of Holoepiphyte Community Structure in Central Amazonian White‐Sand Forests
About: This article is published in Biotropica.The article was published on 2016-01-01. It has received 12 citations till now. The article focuses on the topics: Amazon rainforest & Amazonian.
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TL;DR: In this paper, the authors compared composition, richness and structure of epiphyte assemblages in white-water and black-water floodplains (varzea and igapo) in Central Amazonia.
Abstract: Research focusing on assemblages of vascular epiphytes in the Amazon are scarce. This is especially true for Amazonian floodplain forests, for which only two previous studies have been published. We compared composition, richness and structure of epiphyte assemblages in white-water and black-water floodplains (varzea and igapo) in Central Amazonia in order to close knowledge gaps concerning the distribution and richness of epiphytes. We established sixteen 25x25 m plots in each forest type, and counted and identified all species of vascular epiphytes occurring on trees with a diameter at breast height (DBH) ≥10 cm. We observed a clear distinction in epiphytic species composition (r2=0.83, p=0.001) and diversity (t=3.24, P=0.003) between the two environments, with 61.5 % of species being restricted to varzea, 22.9 % restricted to igapo and only 15.6 % common to both ecosystems. The floodplains were also structurally different for the most abundant species and those with the highest Epiphytic Importance Value (IVe). The diversity of trees did not influence the epiphyte diversity in either ecosystem. The forests were found to differ in the composition, diversity and structure of their epiphytic assemblages, which must be taken into account when designing conservation action plans for these ecosystems and for their vascular epiphytes.
13 citations
TL;DR: The results reinforce the importance of the lithophyte tree Pseudobombax for the maintenance of epiphytic diversity in the tropical inselbergs of southeast Brazil, mainly due to its size and architecture.
Abstract: This study aimed to quantify the importance of surface roots as phorophyte ecological zones for vascular epiphytes in the lithophyte tree Pseudobombax. The study was conducted on phorophytes, trees that support epiphytes, in three neotropical granitoid rocky outcrops (inselbergs). We investigated how community composition and abundance of vascular epiphytes differed among different ecological zones and examined habitat associations on Pseudobombax. Based on a census of 90 trees, we found 5896 individual vascular epiphytes attributed to 137 species. Bromeliads and orchids were dominant. Our results show that surface roots represented an important ecological zone as 53% of the diversity and 20% of the total vascular epiphyte abundance were found within this zone. Abundance patterns differed among the zones and the lithophyte species Sinningia speciosa, Selaginella convoluta and Alcantarea patriae were associated with the surface roots. Our results reinforce the importance of the lithophyte tree Pseudobombax for the maintenance of epiphytic diversity in the tropical inselbergs of southeast Brazil, mainly due to its size and architecture. The presence of large surface roots considerably increases the habitat for different epiphytic groups, including species typical of inselbergs. Roots are thus an important ecological zone for epiphytic communities on inselbergs.
12 citations
TL;DR: It is shown that neutral and niche-based processes act simultaneously on the dynamics of vascular epiphyte species, but distinctly on the inselberg and cloud forest, as they promote their abundance and maintain their diversity in tropical systems.
Abstract: The great heterogeneity of tropical systems challenges our understanding of how niche and neutral processes structure epiphyte communities. Dispersal, phorophyte identity and the environmental conditions created by phorophytes are the main determinants of vascular epiphyte structure and diversity. However, these forces comprise multiple causal factors that need to be decomposed to address the complex patterns of independent and confounded effects acting upon epiphyte communities. We tested the hypothesis that the environment created by phorophytes (size, bark characteristics, microenvironmental conditions, and substrate type) is more important than phorophyte species identity and space in determining the structure of epiphyte communities, with phorophyte size being a major determinant within the environmental component. We also expected larger phorophytes to exhibit greater epiphyte richness and diversity. The study was carried out on an inselberg within a semi-deciduous montane forest and a cloud forest in southeastern Brazil. Partial redundancy analysis was used to hierarchically decompose the relative abundances of vascular epiphytes into three components: association with particular phorophyte species, the environment created by phorophytes, and space (Moran’s eigenvector maps). Linear models were used to analyze the relationship between epiphytic diversity and richness with size descriptors. We show that neutral and niche-based processes act simultaneously on the dynamics of vascular epiphyte species, but distinctly on the inselberg and cloud forest. The potential for an epiphyte to occupy all favorable phorophytes was larger in the cloud forest due to the higher connectivity offered by trees. Abundance, richness and diversity of epiphytes increased with phorophyte size, probably due to an increase in the area, time of colonization or increase in microhabitat heterogeneity within phorophytes. Larger phorophytes are a major determinant of local environmental conditions and the spatial organization of epiphytes, as they promote their abundance and maintain their diversity in tropical systems.
10 citations
TL;DR: Analysis of Amazonian bryophytes reveals spatial genetic structures comparable to those documented for angiosperms, whose diaspores are orders of magnitude larger, and suggests that the plight of this component of cryptic biodiversity is more dire than previously considered in light of accelerated forest fragmentation in the Amazon.
Abstract: Lowland tropical bryophytes have been perceived as excellent dispersers. In such groups, the inverse isolation hypothesis proposes that spatial genetic structure is erased beyond the limits of short-distance dispersal. Here, we determine the influence of environmental variation and geographic barriers on the spatial genetic structure of a widely dispersed and phylogenetically independent sample of Amazonian bryophytes. Single nucleotide polymorphism data were produced from a restriction site-associated DNA sequencing protocol for 10 species and analyzed through F-statistics and Mantel tests. Neither isolation-by-environment nor the impact of geographic barriers were recovered from the analyses. However, significant isolation-by-distance patterns were observed for 8 out of the 10 investigated species beyond the scale of short-distance dispersal (> 1 km), offering evidence contrary to the inverse isolation hypothesis. Despite a cadre of life-history traits and distributional patterns suggesting that tropical bryophytes are highly vagile, our analyses reveal spatial genetic structures comparable to those documented for angiosperms, whose diaspores are orders of magnitude larger. Dispersal limitation for tropical bryophytes flies in the face of traditional assumptions regarding their dispersal potential, and suggests that the plight of this component of cryptic biodiversity is more dire than previously considered in light of accelerated forest fragmentation in the Amazon. © 2020 The Authors. New Phytologist © 2020 New Phytologist Trust
10 citations
TL;DR: The taxonomic and geographic focus of these articles is impressive, with articles on terrestrial plants, epiphytes, insects, birds, and fungi based on fieldwork conducted in the Amazon Basin, the Guianas, and Brazil's Atlantic Forests as mentioned in this paper.
Abstract: NEOTROPICAL WHITE-SAND FORESTS ARE UNUSUAL ENVIRONMENTS FOUND THROUGHOUT TROPICAL SOUTH AMERICA that often occur as habitat islands surrounded by more familiar rain forests growing on clayey soils. Their namesake sandy soils can greatly reduce nutrient and water availability, leading to stunted forests with unique physiognomies and endemic species assemblages. Although whitesand forests have fascinated biologists since the 19th century (Spruce 1908, Janzen 1974), it was not until the 1980s that efforts to describe their unique nutrient cycling, forest structure, plant adaptations, and biological diversity began in earnest (e.g., Anderson 1981, Medina & Cuevas 1989, Duivenvoorden & Lips 1995, Coomes & Grubb 1996, ter Steege et al. 2000, Alvarez Alonso & Whitney 2003). In this Special Section, we present original research, reviews and synthesis to detail the current state of knowledge of Neotropical white-sand forests, as well as identify research and conservation priorities for the future. The eleven articles in this Special Section are a multinational effort with lead authors from Brazil, Peru, Ecuador, France, and the United States. The taxonomic and geographic focus of these articles is impressive, with articles on terrestrial plants, epiphytes, insects, birds, and fungi based on fieldwork conducted in the Amazon Basin, the Guianas, and Brazil’s Atlantic Forests. Beyond the individual advances these articles put forth, considering them as a whole also reveals three persistent themes. The first is the realization that while some of the white-sand soils are ancient— over 100 million years in some areas of tropical South America —the recent history of the habitat islands we see today is quite dynamic. Their current biota is shaped in part by the expansion and contraction of white-sand areas, the large-scale movement of sediments by rivers, and geologic subsidence during the Pleistocene (Adeney et al. 2016). This combination of ancient origin with recent dynamism has had important consequences for the biota of white-sand habitats. On the one hand, many plant lineages have had long associations with white-sand forests, and have evolved traits that preclude them from expanding their distributions into other forest types (Vicentini 2016). As detailed by Fine and Baraloto (2016), these traits are likely related to adaptations to low nutrient availability, drought, and defense against natural enemies. The discontinuous nature of white-sand habitats across the landscape, which could also have been promoted by Pleistocene changes, may have also resulted in allopatric isolation and subsequent speciation in many of these plant lineages (Guevara et al. 2016); a similar signal of recent divergence may also be seen in the phylogeographic structure of white-sand bird species (Matos et al. 2016). However, other plant and animal lineages appear to exhibit much less niche conservatism, with clades of white-sand forest specialists that are closely related to specialists from other habitat types (Fine & Baraloto 2016, Lamarre et al. 2016). A second, related theme is that many species associated with white-sand forests also occur in other forest types—especially forests with similar structure or resource limitations. Thus, many organisms that are abundant in white-sand forests may not be entirely restricted to these habitats, including species of trees (Garcia-Villacorta et al. 2016), epiphytes (Mar ı et al. 2016), birds (Borges et al. 2016), and ectomycorrhyzal fungi (Roy et al. 2016). These other marginal habitats, including seasonally flooded blackwater forests (igap o) and disturbed open habitats (caatinga), may serve as corridors between isolated white-sand forest islands, resulting in greater gene flow and metacommunity dynamics that buffer against local extinction. Finally, white-sand forests are unique and fragile habitats that are especially vulnerable to anthropogenic change. Many of the contributions highlight specific regions of white-sand forest that should be priorities for conservation initiatives (e.g., Daly et al. 2016); particularly notable among these is Adeney et al. (2016), which also includes the first comprehensive map of Amazonian white-sand ecosystems. We hope the articles in this Special Section make a compelling case for why tropical biologists should continue to study and strive to conserve the fascinating biota of Neotropical white-sand forests.
9 citations
References
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30 Sep 1988
TL;DR: In this paper, the authors define definitions of diversity and apply them to the problem of measuring species diversity, choosing an index and interpreting diversity measures, and applying them to structural and structural diversity.
Abstract: Definitions of diversity. Measuring species diversity. Choosing an index and interpreting diversity measures. Sampling problems. Structural diversity. Applications of diversity measures. Summary.
10,957 citations
"Regional and Fine Scale Variation o..." refers methods in this paper
...Because holoepiphyte abundance differed substantially among sites and height zones, species richness and diversity comparisons were made using Chao’s richness and Fisher’s log series a indices, respectively (Magurran 1988)....
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Utrecht University1, Naturalis2, Duke University3, Institut de recherche pour le développement4, Institut national de la recherche agronomique5, Museu Paraense Emílio Goeldi6, University of California, Berkeley7, University of Leeds8, Empresa Brasileira de Pesquisa Agropecuária9, National Institute of Amazonian Research10, National University of Saint Anthony the Abbot in Cuzco11, University of Exeter12, World Wide Fund for Nature13, Universidad Autónoma Gabriel René Moreno14, Norwegian University of Life Sciences15, Max Planck Society16, James Cook University17, Universidade do Estado de Mato Grosso18, University of Amsterdam19, Silver Spring Networks20, State University of Campinas21, University of Edinburgh22, University of Los Andes23, Smithsonian Conservation Biology Institute24, National University of Colombia25, University of East Anglia26, Central University of Ecuador27, Centre national de la recherche scientifique28, Humboldt State University29, New York Botanical Garden30, Universidade Federal do Acre31, Paul Sabatier University32, Missouri Botanical Garden33, Amazon.com34, University of Texas at Austin35, University of Florida36, Venezuelan Institute for Scientific Research37, Environmental Change Institute38, Federal Rural University of Amazonia39, University of São Paulo40, State University of Norte Fluminense41, Smithsonian Tropical Research Institute42, University of Wisconsin–Milwaukee43, Northern Arizona University44, Aarhus University45, Tropenbos International46, University of Kent47, Royal Botanic Gardens48, University of Missouri–St. Louis49, Universidad Nacional de la Amazonía Peruana50, Fairchild Tropical Botanic Garden51, Florida International University52, Wake Forest University53
TL;DR: The finding that Amazonia is dominated by just 227 tree species implies that most biogeochemical cycling in the world’s largest tropical forest is performed by a tiny sliver of its diversity.
Abstract: The vast extent of the Amazon Basin has historically restricted the study of its tree communities to the local and regional scales. Here, we provide empirical data on the commonness, rarity, and richness of lowland tree species across the entire Amazon Basin and Guiana Shield (Amazonia), collected in 1170 tree plots in all major forest types. Extrapolations suggest that Amazonia harbors roughly 16,000 tree species, of which just 227 (1.4%) account for half of all trees. Most of these are habitat specialists and only dominant in one or two regions of the basin. We discuss some implications of the finding that a small group of species—less diverse than the North American tree flora—accounts for half of the world’s most diverse tree community.
963 citations
TL;DR: A classification of fragmentation sensitivity based on specific trait combinations is developed and the implications of the results for ecological theory are discussed.
Abstract: We reviewed empirical data and hypotheses derived from demographic, optimal foraging, life-history, community, and biogeographic theory for predicting the sensitivity of species to habitat fragmentation. We found 12 traits or trait groups that have been suggested as predictors of species sensitivity: population size; population fluctuation and storage effect; dispersal power; reproductive potential; annual survival; sociality; body size; trophic position; ecological specialisation, microhabitat and matrix use; disturbance and competition sensitive traits; rarity; and biogeographic position. For each trait we discuss the theoretical justification for its sensitivity to fragmentation and empirical evidence for and against the suitability of the trait as a predictor of fragmentation sensitivity. Where relevant, we also discuss experimental design problems for testing the underlying hypotheses. There is good empirical support for 6 of the 12 traits as sensitivity predictors: population size; population fluctuation and storage effects; traits associated with competitive ability and disturbance sensitivity in plants; microhabitat specialisation and matrix use; rarity in the form of low abundance within a habitat; and relative biogeographic position. Few clear patterns emerge for the remaining traits from empirical studies if examined in isolation. Consequently, interactions of species traits and environmental conditions must be considered if we want to be able to predict species sensitivity to fragmentation. We develop a classification of fragmentation sensitivity based on specific trait combinations and discuss the implications of the results for ecological theory.
951 citations
"Regional and Fine Scale Variation o..." refers background in this paper
...Considering the central role that spatial isolation plays in influencing patterns of biological diversity (Henle et al. 2004), studies of plant community structure in systems defined by spatially explicit substrates such as Received 8 May 2015; revision accepted 2 November 2015....
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537 citations
"Regional and Fine Scale Variation o..." refers background in this paper
...In such cases, regional floristic guides, such as Berry et al. (1995) and Ribeiro et al. (1999), were also consulted....
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TL;DR: Habitat specialization in this system results from an interaction of herbivore pressure with soil type when protected from herbivores.
Abstract: In an edaphically heterogeneous area in the Peruvian Amazon, clay soils and nutrient-poor white sands each harbor distinctive plant communities. To determine whether a trade-off between growth and antiherbivore defense enforces habitat specialization on these two soil types, we conducted a reciprocal transplant study of seedlings of 20 species from six genera of phylogenetically independent pairs of edaphic specialist trees and manipulated the presence of herbivores. Clay specialist species grew significantly faster than white-sand specialists in both soil types when protected from herbivores. However, when unprotected, white-sand specialists dominated in white-sand forests and clay specialists dominated in clay forests. Therefore, habitat specialization in this system results from an interaction of herbivore pressure with soil type.
519 citations
"Regional and Fine Scale Variation o..." refers background in this paper
...In theory, plant distributions are influenced by interactions between environmental filters, biotic interactions, and dispersal limitation (Fine et al. 2004, Jabot et al. 2008); however, quantifying such factors in the field is difficult....
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