Climate change, together with human activities, impacts on natural and human systems on all continents and poses a major threat to biodiversity, especially in environments with a high rate of endemism and where species are profoundly adapted to specific environmental conditions, as is the case of the seasonally dry tropical forests, noticeably the Caatinga, an exclusively Brazilian biome. The objective of this study was to build spatial niche models of five species of Cactaceae (Arrojadoa penicillata, Brasilicereus phaeacanthus, Pereskia aureiflora, Stephanocereus leucostele and Tacinga inamoena) endemic to the Caatinga and with different traits, to evaluate the impact of climate change on their geographical distribution. The species records and environmental variable values were overlaid on a grid of 6818 cells with 0.5° spatial resolution. Niche models were obtained for five types of general circulation models between ocean and atmosphere and 12 different ecological models. The ensemble ecological niche model was calculated at present and projected to past (last glacial maximum – LGM, 21 000; and mid‐Holocene – Hol, 6000 years ago) and future climate conditions (average of 2080), under the effect of climate change, in the greenhouse gas emission scenario RCP4.5. The distribution pattern of the studied species indicates an area with less environmental suitability in the LGM, followed by an expansion that began in the Hol and continued until the present period. In the future (2080), the models predicted a retraction of areas of environmental suitability, in which P. aureiflora and B. phaeacanthus, given their more restricted, marginal habitat and woody habit, present a great risk of extinction, whilst S. leucostele, A. penicillata and T. inamoena present a smaller reduction in suitable area, partly reflecting their spreading, less woody habit. Regional conservation actions for Cactaceae species and their habitat need to take these findings into account if we are to ensure the survival of these species.
RESUMO A família Cactaceae inclui 1.850 espécies distribuídas primariamente no continente americano, sendo o Brasil o terceiro maior centro de diversidade da família, com 277 espécies. Neste último centro de diversidade, o Parque Nacional de Boa Nova (PNBN), localizado no leste do Estado da Bahia, Brasil, possui uma área com cerca de 12.065 ha, incluindo um ecótono sentido leste-oeste, com áreas de Mata Atlântica sendo substituídas por mata-de-cipó e, mais a oeste, pela Caatinga. Como parte da proposta do Plano de Ação Nacional para conservação das Cactáceas de 2011, este trabalho apresenta o estudo taxonômico de Cactaceae ocorrentes no PNBN, e tem como objetivo ampliar o conhecimento da flora local e das Unidades de Conservação do Estado da Bahia. O material foi coletado em quatro expedições de coleta durante um ano, em trilhas aleatórias percorrendo os diversos ambientes do parque. Foram registrados 10 gêneros e 15 espécies: Arrojadoa penicillata, Brasilicereus phaeacanthus, Brasiliopuntia brasiliensis, Cereus jamacaru, Cereus sp., Melocactus ernestii, Pereskia aculeata, P. bahiensis, Pilosocereus catingicola, P. pentaedrophorussubsp.robustus, Rhipsalis hileiabaiana, R. russellii, Stephanocereus leucostele, Tacinga funalis eT. werneri. No âmbito do PNBN, as vegetações de mata-de-cipó e Caatinga foram as que apresentaram o maior número de espécies, com oito e cinco espécies, respectivamente, enquanto a Mata Atlântica apresentou uma única espécie.
Species lists available from floristic and phytosociological studies contain important information about species distributions that are useful for making biogeographical inferences and even to evaluate conservation status of species and ecosystems. In the case of the Caatinga, this information may contribute to challenging the pre-established idea that it is a homogeneous vegetation unit. The strong relation between the substrate and the plant assemblages of the Caatinga may characterise different types of vegetation. In this way, the objective of the present study is to evaluate whether differences in the distribution of Cactaceae relate to distinctive types of substrate (sedimentary and crystalline) as much in terms of floristic richness as species density. Concomitantly, we evaluated the conservation status of the Caatinga areas studied. To obtain the data, we undertook a bibliographic revision of floristic and phytosociological studies in the Caatinga and constructed a similarity matrix using the selected floristic studies in order to evaluate the relation among different areas of Caatinga. We found that 48 areas included Cactaceae species; 33 species distributed in 14 genera were recorded. Among these taxa, Cereus jamacaru was the species that presented the largest number of occurrences, appearing in 17 areas, followed by Pilosocereus gounellei (=Xiquexique gounellei), found in 11 studies, and Tacinga inamoena in 10. The grouping analysis resulted in the formation of 10 groups, with a remarkable relationship between species and soil type. There were differences in both the diversity and density of species related with the degree of conservation of the Caatinga, noticeable from the direct relationship between conservation and richness and, indirectly, between density and number of species.
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