Habitat amount hypothesis and passive sampling explain mammal species composition in Amazonian river islands

Rabelo, Rafael M.; Aragón, Susan; Bicca‐Marques, Júlio César; Nelson, Bruce

doi:10.1111/btp.12615

Cited by 13 publications

(14 citation statements)

References 41 publications

(87 reference statements)

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“…Larger islands support more species from the regional pool (Fahrig, ), and thus, species sharing tends to be higher in well‐connected landscapes as a single island tends to capture a greater portion of the total regional species pool. In low connectivity landscapes, distant islands tend to share fewer species, because smaller islands support fewer species (Rabelo, Aragón, Bicca‐Marques, & Nelson, ), and composition is the result of a small subset of the regional pool thus increasing beta diversity.…”

Section: Discussionmentioning

confidence: 99%

Islands in a green ocean: Spatially structured endemism in Amazonian white‐sand vegetation

et al. 2019

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Here, we examine the influence of the spatial distribution of open white-sand campina (WSC) in the Amazon on the species richness and beta diversity of their vascular plants. It is well known that beta diversity tends to increase with geographical distance, but the influence of habitat insularity on floristic composition and endemism is still unclear. We surveyed WSC in central and southwestern Amazon, generating lists of species occurrences by rapid-inventory techniques to evaluate the influence of island area and connectivity on alpha and beta diversity among five landscapes in the Amazon Basin. Effects of insularity were assessed by comparing alpha and beta diversity within and among landscapes. A high proportion of species (~74%) and genera (~50%) were restricted to only one of the five landscapes and only three species and 28 genera were shared among all landscapes. At the regional scale, beta diversity increased significantly with distance. Partitioning of beta diversity showed that landscapes of higher connectivity have greater turnover and lower nestedness.We conclude that the flora of WSC is highly structured at regional scales, while at the local scale structure is evident only in low connectivity landscapes. Landscape metrics apparently play an important role in shaping patterns of diversity regionally as a result of processes operating at larger geographical scales. This emphasizes that conservation policy should not be local in its geographical focus and should account for connectivity at larger scales. This study is the first to empirically and explicitly evaluate the pattern of endemism in lowland WSC in the Amazon.Abstract in Porteges is available with online only K E Y W O R D S beta diversity, campina, campinarana, island biogeography, savanna, tropical dry forests

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Section: Discussionmentioning

confidence: 99%

Islands in a green ocean: Spatially structured endemism in Amazonian white‐sand vegetation

et al. 2019

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“…The passive sampling effect, in which the probability that a species will colonize an island is proportional to its regional abundance, provides another possible explanation for the nested patterns (Ulrich et al., ). Indeed, occupancy of Amazonian fluvial islands by mammal species is predicted by regional abundance (Rabelo et al., ). The relative abundance of captured birds on studied islands and in the nearby blackwater flooded forest was positively correlated (Spearman rank correlation Rs = 0.51, p < .001) which also suggests that passive sampling could affect the observed nested composition patterns.…”

Section: Discussionmentioning

confidence: 99%

“…Recently, the biodiversity of Amazonian river islands has received increasing attention (Choueri et al, 2017;Cintra et al, 2007;Nunes, de Carvalho, Vaz-de-Mello, Dáttilo & Izzo, 2014;Rabelo, Aragón, Bicca-Marques & Nelson, 2019;Rabelo, Bicca-Marques, Aragón & Nelson, 2017;Rocha et al, 2014). This is a welcome development, since biodiversity studies of fluvial islands have important conservation implications.…”

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Bird assemblages on Amazonian river islands: Patterns of species diversity and composition

Borges

Baccaro

Moreira³

et al. 2019

Biotropica

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The principles of island biogeography are rarely applied to the animal assemblages of Amazonian river islands. Here, we compare bird assemblages of Amazonian river islands with a variety of mainland habitats. We also examine how bird species diversity and composition are related to island physical attributes. Birds were sampled with mist nets and qualitative censuses on 11 river islands and 24 mainland sites on the lower reaches of the Rio Negro in the Brazilian Amazon. Island bird assemblages were characterized by lower species richness and a higher abundance of a few dominant species. Additionally, the species composition of the islands was distinct from that of the mainland, including the nearby floodplain habitats. The number of bird species increased with island size and habitat diversity, and decreased with degree of isolation. In addition, small islands tended to harbor an impoverished subset of the species present on larger ones. Bird species diversity and composition on Amazonian river islands are likely influenced by the ecological succession and historical events affecting island formation. Considering their small total area across the Amazon basin, these insular fluvial communities could be disproportionately threatened by river channel disturbances related to climate change or hydroelectric dam development. Abstract in Portughese is available with online material.

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“…Red howler monkeys (Alouatta juara), brown-throated sloths (Bradypus variegatus) and jaguars are the most common mammal species in both the continuous forest and the fluvial islands (Rabelo et al, 2019). These islands originate from a complex river dynamics, in which the deposition of sediments as sandbars in the river channel that are followed by primary succession (Kalliola et al, 1991).…”

Section: Introductionmentioning

confidence: 99%

Prey abundance drives habitat occupancy by jaguars in Amazonian floodplain river islands

Rabelo

Aragón

Bicca‐Marques

2019

Preprint

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The jaguar (Panthera onca) is widely distributed across a broad range of habitat types, where its feeding habits and habitat use patterns vary significantly. The jaguar and its main arboreal preys -the brown-throated sloth (Bradypus variegatus) and the red howler monkey (Alouatta juara) -are widespread in the Amazonian floodplain forests Mamirauaó Reserve. These forest-dwelling species are the most common mammal species both in the continuous forest and the forest patches surrounded by a river matrix -the fluvial islands -at Solimoã es and Japuraó rivers. We used sign surveys along line-transects to assess the pattern of habitat occupancy by jaguars in Amazonian floodplain forests. Specifically, we (i) tested whether habitat occupancy by jaguars differs between river islands and continuous forest;and (ii) evaluated whether and how the local abundance of sloths and howler monkeys influence the probability of site occupancy by jaguars. We built an occupancy model and used Bayesian inference to reach these goals. The proportion of sites estimated to be used by jaguars was ψ = 0.75 (HPD95: 0.36-1.00), and it did not differ between islands and continuous forest. The abundance of both prey species had a direct influence on jaguar's habitat use, whereas the aquatic matrix seems to have a negligible effect on the use of islands by jaguars. We conclude that prey search modulates jaguars' habitat occupancy patterns with both prey species having a similar effect. This finding reinforces the importance of sloths to the diet of jaguars in the study region despite its lower abundance than howlers. Finally, we suggest that sign surveys are an alternative method to assess the pattern of jaguar habitat occupancy in floodplain forests.

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Habitat amount hypothesis and passive sampling explain mammal species composition in Amazonian river islands

Cited by 13 publications

References 41 publications

Islands in a green ocean: Spatially structured endemism in Amazonian white‐sand vegetation

Islands in a green ocean: Spatially structured endemism in Amazonian white‐sand vegetation

Bird assemblages on Amazonian river islands: Patterns of species diversity and composition

Prey abundance drives habitat occupancy by jaguars in Amazonian floodplain river islands

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