Spatial niche modelling of five endemic cacti from the Brazilian Caatinga: Past, present and future SILVANA DOS SANTOS SIM ~ OES, 1,2 DANIELA ZAPPI, 3 GR ^ ENIVEL MOTA DA COSTA, 2 GUILHERME DE OLIVEIRA 2 AND LIDYANNE YURIKO SALEME AONA 2 * 1 Programa de mestrado em Recursos Gen  eticos Vegetais, Universidade Federal do Rec^ oncavo da Bahia – UFRB; 2 Centro de Ci ^ encias Agr arias, Ambientais e Biol  ogicas, Universidade Federal do Rec^ oncavo da Bahia – UFRB, Rua Rui Barbosa, 710, Centro, Cruz das Almas, 44380-000 (Email: lidyanne.aona@gmail.com); and 3 Instituto Tecnol  ogico Vale/Museu Paraense Emilio Goeldi – Coord. Bot^ anica, Bel  em, Brazil Abstract Climate change, together with human activities, impacts on natural and human systems on all conti- nents 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 aurei- flora, Stephanocereus leucostele and Tacinga inamoena) endemic to the Caatinga and with different traits, to evalu- ate 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 stud- ied 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, mar- ginal 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. Key words: Cactaceae, climate change, conservation, forecast modelling, North-eastern Brazil, plant distribution. INTRODUCTION Climatic changes caused by physical–chemical alter- ations in the atmosphere result in cycles of heating and cooling and are natural global phenomena (Oli- veira et al. 2017). However, since the Industrial Revolution and with the resulting increase in gas emissions and the greenhouse effect, these cycles are accelerating and affecting the global climate (Mar- engo 2006). These changes lead to impacts on natu- ral and human systems globally, with more intense and comprehensive impacts on natural systems due to their vulnerability (IPCC - Intergovernmental Panel on Climate Change 2014). During the Pleistocene, gradual climatic changes affected the geographical distribution of the species as a result of changes in the heating and cooling cycles, leading to humid and dry periods occurring in the tropics (Brasil 2007). These changes, principally those arising during the last glacial maximum (LGM), influenced the evolution of flora and fauna (Meyer et al. 2014). Between 18 and 36 thousand years ago, the climate was moister, allowing the development of densely wooded savanna and sparse forests in Central Brazil; between 22 and 18 thou- sand years ago, the humidity started to decrease and the area reached maximum aridity between 10 and 10.5 thousand years ago. During this period, there was a decrease in the tree component and an expan- sion of the open savanna and dry forest (Meyer et al. 2014). *Corresponding author. Accepted for publication August 2019. © 2019 Ecological Society of Australia doi:10.1111/aec.12825 Austral Ecology (2019) , –