Corresponding author: Caroline Oliveira Andrino (
Academic editor: Ricarda Riina
The world’s largest mineral iron province, Serra dos Carajás, is home to an open vegetation known as canga, found on top of isolated outcrops rising out of the Amazon rainforest. Over one thousand vascular plants species have been recorded in these canga sites, including 38 edaphic endemics. A new survey adds to our investigation of biogeographic relationships between sixteen canga outcrops and the effect of the distance between site pairs on the number of shared species, regional species turnover and species distribution patterns. Plant collecting expeditions to the westernmost site, the Serra de Campos of São Félix do Xingu (
Andrino CO, Barbosa-Silva RG, Lovo J, Viana PL, Moro MF, Zappi DC (2020) Iron islands in the Amazon: investigating plant beta diversity of canga outcrops. PhytoKeys 165: 1–25.
Mountaintops are often compared to sky-islands, as their vegetation is often distinct from the surrounding lowlands (
Canga is the lateritic duricrust that covers a supergene iron ore, with poorly developed soil and moderately hard rocks that are very resistant to erosion and permeable (
Species isolation caused by environmental conditions contrasting with the surrounding forests and associated with the mosaic of different geomorphological situations in the canga creates also an abundance of micro-habitats (
The first botanical studies on the iron islands of the Serra dos Carajás began in the late 1960s. However, the floristic knowledge was not synthetized and organized until the Flora of the canga of the Serra de Carajás (
Due to historic reasons, collection efforts of the
This study aims to investigate plant distribution and biogeographical patterns that connect the island-like habitats of canga outcrops isolated within an Amazonian rainforest matrix. We evaluated species distribution in the different sites in order to observe whether canga vegetation has elevated levels of beta diversity and whether the flora of each outcrop will be more dissimilar to other outcrops as the geographical distance increases. We provided the first checklist of vascular plants growing on canga at the Serra de Campos of São Félix do Xingu (
The
Most of the ferruginous island complex in the southeastern Amazon is within areas protected at different levels. The Serra Norte (
The Serra de Campos (
Botanical specimens from
Four plant collecting expeditions were carried out between 2016 and 2019 (May 2016, April 2017, March 2018, October 2019), aiming to collect fertile material of all vascular species. Collecting method followed
The samples collected were identified to species by comparing their macroscopic and microscopic morphological features with available bibliography, against herbarium collections (physically and on-line) and also consulting key family specialists. Voucher specimens were deposited at
Seed plant species distribution data were assembled from the
To perform the biogeographical analysis of the
To investigate the floristic richness of sites in relation to the size of each outcrop we used the species count for each canga outcrop and, employing GIS, we calculated the area of each outcrop in square kilometres. A linear model of the recorded richness versus area of each outcrop using the ‘glm’ function with Gaussian model was prepared in R. Because the outcrops were subjected to a large collecting effort during the ‘Flora of Carajás’ Project, we assumed that they were adequately sampled. We also evaluated whether the total number of species and of endemic species shared between sites were significantly related with the geographical distance between them. We computed the centroid of each outcrop using GIS and calculated the geographical distance between the centroids of all outcrop pairs. We tested the normality of the residuals of the models with the Shapiro-Wilk test to see whether the residuals significantly departed from normality. If these did not significantly differ from normality, we accepted the p value of the model. If the residuals differed from normality, we analysed the data using non parametric Spearman’s correlation to evaluate if the correlation was significant.
This study recorded a total of 254 species, of which 248 are seed plants, five ferns and one lycophyte in the
Vascular plant species from Serra de Campos of São Félix do Xingu (
Taxa | New for Carajás Flora | Endemic canga | Endemic |
Life form | Voucher |
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X | Herb | ||||
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Treelet | |||||
X | Treelet | ||||
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X | Shrub | ||||
Tree | |||||
X | Tree | ||||
Treelet | |||||
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Tree | |||||
Liana | |||||
Herb | |||||
X | Herb | ||||
Treelet | |||||
Treelet | |||||
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Herb | |||||
X | Herb | ||||
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Palm | |||||
Palm | |||||
Palm | |||||
Palm | |||||
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Herb | |||||
Shrub | |||||
X | Herb | ||||
Herb | |||||
Herb | |||||
Herb | |||||
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Herb | |||||
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Liana | |||||
Liana | |||||
X | Shrub | ||||
Liana | |||||
Shrub | |||||
Liana | |||||
Liana | |||||
Liana | |||||
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Treelet | |||||
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Tree | |||||
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Herb | |||||
Herb | |||||
Herb | |||||
Herb | |||||
Herb | |||||
X | Herb | ||||
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Herb | |||||
Herb | |||||
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Herb | |||||
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Herb | |||||
Liana | |||||
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Shrub | |||||
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X | Liana | ||||
Liana | |||||
Liana | |||||
X | Liana | ||||
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Herb | |||||
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Herb | |||||
Herb | |||||
Herb | |||||
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Herb | |||||
X | Herb | ||||
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Herb | |||||
Herb | |||||
Herb | |||||
Herb | |||||
Herb | |||||
Herb | |||||
Herb | |||||
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Liana | |||||
X | Liana | ||||
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X | Herb | ||||
Herb | |||||
Herb | |||||
X | Herb | ||||
Herb | |||||
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X | Shrub | ||||
Shrub | |||||
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Shrub | |||||
Tree | |||||
Shrub | |||||
Shrub | |||||
Shrub | |||||
Shrub | |||||
X | Shrub | ||||
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Liana | |||||
Subshrub | |||||
Shrub | |||||
Shrub | |||||
Herb/Liana | |||||
Subshrub | |||||
Liana | |||||
Shrub | |||||
Liana | |||||
X | Tree | ||||
X | Tree | ||||
X | Tree | ||||
X | X | X | Subshrub | ||
Shrub | |||||
X | Herb | ||||
Subshrub | |||||
Tree | |||||
Shrub | |||||
Shrub | |||||
Treelet | |||||
Subshrub | |||||
Tree | |||||
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Herb | |||||
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X | Herb | ||||
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Treelet | |||||
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Herb | |||||
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Subshrub | |||||
Herb | |||||
Herb | |||||
Herb | |||||
X | Tree | ||||
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Parasite | |||||
X | X | Shrub | |||
Shrub | |||||
X | Tree | ||||
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Herb | |||||
Herb | |||||
Herb | |||||
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Parasite | |||||
Parasite | |||||
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Subshrub | |||||
X | Shrub | ||||
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Shrub | |||||
Liana | |||||
Shrub | |||||
Liana | |||||
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Herb | |||||
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Shrub | |||||
Herb | |||||
X | Shrub | ||||
Herb | |||||
Shrub | |||||
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Shrub | |||||
Liana | |||||
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Shrub | |||||
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Shrub | |||||
Shrub | |||||
Shrub | |||||
Shrub | |||||
X | Shrub | ||||
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Treelet | |||||
X | Shrub | ||||
Shrub | |||||
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Shrub | |||||
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Herb | |||||
Herb | |||||
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Herb | |||||
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Liana | |||||
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Liana | |||||
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Herb | |||||
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Herb | |||||
Herb | |||||
Herb | |||||
Herb | BFF 634 | ||||
Herb | |||||
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Shrub | |||||
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X | Liana | ||||
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Shrub | |||||
Herb | |||||
X | Subshrub | ||||
Herb | |||||
Shrub | |||||
X | Shrub | ||||
Shrub | |||||
Treelet | |||||
X | Herb | ||||
Herb | |||||
Subshrub | |||||
Liana | |||||
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Treelet | |||||
Subshrub | |||||
Shrub | |||||
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Tree | |||||
Shrub | |||||
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X | Shrub | ||||
X | Liana | ||||
X | Shrub | ||||
Liana | |||||
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Treelet | |||||
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Shrub | |||||
Shrub | |||||
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Treelet | |||||
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Liana | |||||
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Herb | |||||
Treelet | |||||
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Liana | |||||
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Shrub | |||||
Herb | |||||
Shrub | |||||
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Tree | |||||
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Herb | |||||
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X | Shrub | ||||
Shrub | |||||
Subshrub | |||||
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Liana | |||||
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Tree | |||||
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X | Herb | ||||
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Representative species of canga in new dataset,
Among the 38 edaphic endemic species of canga, defined according to
Areas compared by this study, respective area codes used in the multivariate analysis and number of angiosperms species recorded for each area. Serra de Campos of São Félix do Xingu (
Area code | Area | Species | Cumulative species |
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ARQ | Serra Arqueada | 149 | 149 |
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Serra dos Carajás – Serra Sul 11A | 230 | 535 |
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Serra dos Carajás – Serra Sul 11B | 201 | |
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Serra dos Carajás – Serra Sul 11C | 180 | |
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Serra dos Carajás – Serra Sul 11D | 428 | |
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Serra dos Carajás – Serra Norte 1 | 383 | 643 |
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Serra dos Carajás – Serra Norte 2 | 125 | |
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Serra dos Carajás – Serra Norte 3 | 218 | |
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Serra dos Carajás – Serra Norte 4 | 308 | |
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Serra dos Carajás – Serra Norte 5 | 293 | |
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Serra dos Carajás – Serra Norte 6 | 99 | |
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Serra dos Carajás – Serra Norte 7 | 112 | |
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Serra dos Carajás – Serra Norte 8 | 101 | |
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Serra dos Carajás – Serra da Bocaina | 223 | 336 |
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Serra dos Carajás – Serra do Tarzan | 211 | |
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Serra de Campos – São Félix do Xingu | 248 | 248 |
Around 25% (60) of the 248 angiosperms registered for
Regarding the phytophysiognomies listed by
The biogeographical database from the
The mean angiosperm species richness for each outcrop of the Serra dos Carajás was 218 species. The
Species richness was significantly correlated with site area (
Regarding the total of species of the canga, the Carajás iron islands share an average of 40% of their flora with each other.
The most species-rich families and genera found in the
There is a large turnover of species between outcrops (
As an example, only three species were recorded in all surveyed areas: the widely distributed
Some widely distributed species from the canga of Carajás, found at more than 10 of the 16 sites surveyed, were not recorded at
The canga is typically a mosaic of different vegetation types (
Despite having the lowest number of species registered in the
As a relatively large canga site isolated from the active iron mines further to the east, the
The mosaic of landscapes typical of
The greater similarity between
The low number of species restricted to the Amazon (25%) and the high number of species widely distributed in South America (75%) recorded at
Another factor that may have an impact on the contrasting effects of floristic similarity vs. distance from canga islands is the different environmental requirements of herbs, shrubs and trees, that shape their biogeographical patterns and affect species-area and richness-environment relationships (
Recent analyses of open vegetation in the Amazon reinforce the insular character of Amazonian canga and their low similarity to other vegetation types in the Amazonian biome (
Species richness of the iron islands outcrops of Carajás complex (bold diagonal) along with the number of shared species (above diagonal) and distance in kilometres (below diagonal) between the centroid sites; an estimated area for each site is provided.
Sites | Area (km2) |
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ARQ |
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19.98 |
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100 | 47 | 79 | 80 | 75 | 135 | 85 | 124 | 46 | 84 | 108 | 101 | 56 | 57 | 56 |
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8.3 | 24 |
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48 | 88 | 90 | 80 | 138 | 84 | 119 | 59 | 87 | 102 | 105 | 55 | 59 | 53 |
ARQ | 1.27 | 140 | 116 |
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52 | 44 | 45 | 80 | 70 | 75 | 30 | 52 | 77 | 62 | 30 | 29 | 32 |
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15.27 | 59 | 24 | 92 |
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139 | 119 | 170 | 96 | 143 | 59 | 89 | 116 | 101 | 56 | 54 | 53 |
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8.44 | 54.6 | 30.8 | 82 | 4.5 |
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107 | 147 | 77 | 120 | 53 | 81 | 96 | 99 | 49 | 52 | 48 |
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6.26 | 52.5 | 28.8 | 85 | 10 | 4.5 |
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140 | 83 | 110 | 46 | 72 | 101 | 91 | 49 | 41 | 50 |
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16.41 | 47 | 24.4 | 92.3 | 15.7 | 9.8 | 5.7 |
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141 | 222 | 80 | 134 | 189 | 168 | 75 | 80 | 72 |
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9.04 | 217 | 193 | 79.5 | 158 | 162 | 165 | 170 |
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131 | 48 | 82 | 111 | 95 | 52 | 44 | 51 |
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11.81 | 52 | 37.7 | 111 | 37 | 38 | 40 | 42 | 180 |
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98 | 154 | 183 | 174 | 77 | 71 | 78 |
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0.86 | 46.8 | 32.8 | 113 | 36.8 | 37.1 | 39.3 | 40 | 184 | 5.18 |
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69 | 73 | 71 | 40 | 34 | 44 |
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2.1 | 44.7 | 32 | 117.5 | 40.2 | 40.1 | 42 | 42.2 | 188 | 8.1 | 3.8 |
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129 | 103 | 71 | 60 | 59 |
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14.83 | 38 | 25 | 117.4 | 37.5 | 36.4 | 37.7 | 37 | 189 | 13.7 | 8.6 | 7.4 |
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181 | 74 | 65 | 81 |
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8.26 | 32.36 | 22.75 | 122 | 41 | 39 | 40 | 38.53 | 195 | 19.78 | 14.6 | 12.4 | 6.2 |
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63 | 54 | 69 |
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0.97 | 35.29 | 22.46 | 118 | 37.3 | 35.8 | 36.7 | 35.7 | 190 | 16 | 11 | 10 | 3 | 4 |
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40 | 42 |
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0.34 | 33 | 19 | 117 | 35.7 | 33.8 | 34 | 33.1 | 190.5 | 18 | 14 | 13 | 6 | 5 | 3 |
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46 |
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2.69 | 30 | 17 | 119 | 37 | 34.7 | 35 | 33 | 192 | 22 | 17 | 16 | 8.8 | 6 | 5.7 | 3.3 |
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Different evolutionary processes of the species occurring in
Endemic edaphic species of the iron islands outcrops of Carajás complex (bold diagonal) along with the number of shared endemic species (above diagonal) and distance in kilometres (below diagonal) between the centroid sites.
Sites |
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ARQ |
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15 | 3 | 17 | 15 | 16 | 19 | 11 | 18 | 11 | 15 | 15 | 13 | 11 | 11 | 12 |
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24 |
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2 | 14 | 13 | 14 | 15 | 9 | 15 | 9 | 12 | 11 | 11 | 9 | 10 | 10 |
ARQ | 140 | 116 |
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5 | 4 | 5 | 7 | 5 | 6 | 3 | 4 | 5 | 3 | 2 | 2 | 4 |
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59 | 24 | 92 |
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17 | 21 | 22 | 14 | 21 | 10 | 16 | 17 | 13 | 11 | 9 | 12 |
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54.6 | 30.8 | 82 | 4.5 |
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18 | 19 | 10 | 15 | 14 | 14 | 13 | 12 | 10 | 8 | 10 |
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52.5 | 28.8 | 85 | 10 | 4.5 |
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21 | 13 | 11 | 10 | 15 | 15 | 13 | 10 | 9 | 12 |
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47 | 24.4 | 92.3 | 15.7 | 9.8 | 5.7 |
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14 | 21 | 11 | 18 | 19 | 14 | 12 | 12 | 14 |
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217 | 193 | 79.5 | 158 | 162 | 165 | 170 |
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13 | 9 | 13 | 12 | 8 | 9 | 7 | 9 |
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52 | 37.7 | 111 | 37 | 38 | 40 | 42 | 180 |
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15 | 20 | 22 | 19 | 13 | 12 | 16 |
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46.8 | 32.8 | 113 | 36.8 | 37.1 | 39.3 | 40 | 184 | 5.18 |
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15 | 14 | 14 | 11 | 8 | 12 |
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44.7 | 32 | 117.5 | 40.2 | 40.1 | 42 | 42.2 | 188 | 8.1 | 3.8 |
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20 | 15 | 15 | 12 | 15 |
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38 | 25 | 117.4 | 37.5 | 36.4 | 37.7 | 37 | 189 | 13.7 | 8.6 | 7.4 |
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18 | 14 | 12 | 17 |
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32.36 | 22.75 | 122 | 41 | 39 | 40 | 38.53 | 195 | 19.78 | 14.6 | 12.4 | 6.2 |
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11 | 9 | 15 |
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35.29 | 22.46 | 118 | 37.3 | 35.8 | 36.7 | 35.7 | 190 | 16 | 11 | 10 | 3 | 4 |
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8 | 10 |
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33 | 19 | 117 | 35.7 | 33.8 | 34 | 33.1 | 190.5 | 18 | 14 | 13 | 6 | 5 | 3 |
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10 |
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30 | 17 | 119 | 37 | 34.7 | 35 | 33 | 192 | 22 | 17 | 16 | 8.8 | 6 | 5.7 | 3.3 |
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This is the most complete study analysing a database of canga outcrop islands in the Amazon thus far. Our data suggest higher shared similarity between largest sites and higher species richness. We show that species richness in these vegetation islands reveals complex biogeographic patterns and relatively high beta diversity. Outcrop size seemed to be more important than geographical proximity between outcrops, and this should be taken into account when drafting conservation and compensation measures for the canga. There are still inaccessible canga outcrops towards the north of the state of Pará that remain unexplored, and their study would certainly yield interesting information to be added to the present findings.
We are grateful to the Museu Paraense Emílio Goeldi (MPEG) and Instituto Tecnológico Vale (ITV) for essential infrastructure and support for this project, and to Priscila O. Rosa, from the Herbarium
Data availability statement: All supplementary data can be accessed at figshare repository:
Investigating plant beta diversity of canga outcrops
species data