Sugarloaf Land in south-eastern Brazil: a tropical hotspot of lowland inselberg plant diversity

Abstract

Background: Isolated monoliths of granitic and/or gneissic rock rising abruptly from the surrounding landscape are known as inselbergs. Dome-shaped inselbergs are common throughout the Atlantic Forest in south-eastern Brazil, a region known as Sugarloaf Land (SLL). This study aimed to create the first checklist of vascular plant species occurring on lowland inselbergs in SLL, with a focus on vegetation islands. We used information from online databases, our own field sampling and data from previously-published studies. We found 548 vascular plant species (505 angiosperms; 43 ferns and lycophytes) belonging to 69 families and 212 genera. Of all identified species, 536 are native and 12 are naturalised.

New information: We updated the information currently available in Flora do Brasil 2020, as 59% of the angiosperms and 63% of the ferns and lycophytes on our checklist were not previously characterised as occurring on rock outcrops. As a first step towards generating a Virtual Herbarium of lowland inselberg vascular plants, we added barcode vouchers with images available online for 75% of the total number of vascular species. In the official lists of endangered species, 115 angiosperms and five ferns and lycophytes are mentioned. However, the conservation status of many species have not yet been evaluated (77% angiosperms; 88% ferns and lycophytes), thus this list is an important step towards their conservation. The information provided herein is essential for management programmes related to rock outcrops in Brazil as they are facing serious threats to conservation.

Keywords: Atlantic Forest; granite outcrops; rock outcrops; rupicolous plants.

Figure 1.

Examples of highland and lowland inselbergs occurring in SE Brazil. The first row represents highland inselbergs; A. Serra do Caparaó, Minas Gerais State; B. Serra do Itatiaia, Rio de Janeiro State. The second row represents lowland inselbergs, also known as sugarloaves; C. Sugarloaf Mountain, Rio de Janeiro; D. Pedra da Boca, Minas Gerais. Photos by L.F.A. de Paula, except for A. by N.F.O. Mota.

Figure 2.

Procedure 1: stages of data filtering to obtain the angiosperm species list for lowland inselbergs, SE Brazil, based on the list available from BFG (2015). The left column shows species that remained during the construction and validation of the list and the right column represents species removed from the list; S1-S4: indicates steps 1- 4 (see text for more details). Procedure 2: stages of data addition to obtain the final angiosperm species list for lowland inselbergs, SE Brazil.

Figure 3.

Procedure 1: stages of data filtering to obtain the fern and lycophyte species list from lowland inselbergs, SE Brazil, based on the list available from Prado et al. (2015). The left column represents species that remained during the construction and validation of the list and the right column represents species removed from the list; S1-S4: indicates steps 1- 4 (see text for more details). Procedure 2: stages of data addition to obtain the final fern and lycophyte species list for lowland inselbergs, SE Brazil.

Figure 4.

Schematic representation of inselberg vegetation. Vegetation islands are represented by patches 1-5 of varying shapes and sizes, which are bounded by bare rock or directly seated on bare rock (Porembski et al. 2000). Scrub vegetation (Rizzini 1997) appears in the transition zone between the outcrop and the forest that borders the inselberg. The matrix is characterised by the surrounding vegetation, in this case represented by the forest physiognomies belonging to the Atlantic Forest domain. The schematic representation was adapted from de Paula et al. (2015).

Figure 5.

Species belonging to the most representative angiosperm families from vegetation islands occurring on lowland inselbergs in the Atlantic Forest, SE Brazil. A. Encholirium gracile L.B.Sm . (Bromeliaceae); B. Encyclia spiritusanctensis L.C.Menezes (Orchidaceae); C. Barbacenia tomentosa Mart. (Velloziaceae); D. Begonia aguiabrancensis L.Kollmann (Begoniaceae); E. Vellozia pulchra L.B.Sm. (Velloziaceae); F. Coleocephalocereus fluminensis (Miq.) Backeb. (Cactaceae); G. Pleroma marinanum P.J.F. Guim. & Fraga (Melastomataceae); H. Cnidoscolus lombardii Fern.Casas (Euphorbiaceae); I. Mandevilla grazielae M.F.Sales et al. (Apocynaceae). Photos A, B, D, E, I by L.F.A. de Paula; C, F, G, H by L.O. Azevedo.

Figure 6.

Richest angiosperm families from lowland inselbergs in the Atlantic Forest, SE Brazil.

Figure 7.

Richest angiosperm genera from lowland inselbergs in the Atlantic Forest, SE Brazil.

Figure 8.

Species belonging to the most representative fern and lycophyte families from vegetation islands occurring on lowland inselbergs in the Atlantic Forest, SE Brazil. A. Selaginella convoluta (Arn.) Spring (Selaginellaceae); B. S. sellowii Hieron. (Selaginellaceae); C. Cheilanthes geraniifolia (Weath.) R.M.Tryon & A.F.Tryon (Pteridaceae); D. Doryopteris collina (Raddi) J.Sm. (Pteridaceae).

Figure 9.

Richest fern and lycophyte families from lowland inselbergs in the Atlantic Forest, SE Brazil.

Figure 10.

Richest fern and lycophyte genera from lowland inselbergs in the Atlantic Forest, SE Brazil.

Figure 11.

Life forms of the vascular plant species occurring on lowland inselbergs in the Atlantic Forest, SE Brazil.

Figure 12.

Percentage of vascular plant species occurring in different habitat types on lowland inselbergs in the Atlantic Forest, SE Brazil. VI = vegetation islands; VI_S = vegetation islands and scrub.

Figure 13.

Percentages of the vascular plant species included in the checklist that were collected by the authors (C) or vouchered indirectly from other sources (OS).

Figure 14.

General overview of Sugarloaf Land (SLL) region. The concave polygon that indicates SLL was built, based on the available coordinates of the vouchers assigned in the vascular plant list for lowland inselbergs occurring in the Atlantic Forest, SE Brazil.

Figure 15.

Main threats to inselberg biodiversity in SE Brazil. A, B. Mining in Espírito Santo State; C, D. Burned populations of Alcantarea extensa (Bromeliaceae) and Vellozia plicata (Velloziaceae), respectively, due to anthropogenically-caused fire in Minas Gerais State; E, F. Invasive grass (Melinis repens) on inselbergs in Minas Gerais State; G, H. Grazing on inselberg surroundings and on the top of an inselberg, respectively, in Minas Gerais State; I, J. Urban expansion on to inselbergs in the municipalities of Rio de Janeiro (Rio de Janeiro State) and Vitória (Espírito Santo State), respectively. Photos by L.F.A. de Paula, except for photo I by J.M.A. Braga.