Climatic stability in the Brazilian Cerrado: implications for biogeographical connections of South American savannas, species richness and conservation in a biodiversity hotspot

Abstract

Aim To investigate the historical distribution of the Cerrado across Quaternary climatic fluctuations and to generate historical stability maps to test: (1) whether the ‘historical climate’ stability hypothesis explains squamate reptile richness in the Cerrado; and (2) the hypothesis of Pleistocene connections between savannas located north and south of Amazonia. Location The Cerrado, a savanna biome and a global biodiversity hotspot distributed mainly in central Brazil. Methods We generated occurrence datasets from 1000 presence points randomly selected from the entire distribution of the Cerrado, as determined by two spatial definitions. We modelled the potential Cerrado distribution by implementing a maximum‐entropy machine‐learning algorithm across four time projections: current, mid‐Holocene (6 ka), Last Glacial Maximum (LGM, 21 ka) and Last Interglacial (LIG, 120 ka). We generated historical stability maps (refugial areas) by overlapping presence/absence projections of all scenarios, and checked consistencies with qualitative comparisons with available fossil pollen records. We built a spatially explicit simultaneous autoregressive model to explore the relationship between current climate, climatic stability, and squamate species richness. Results Models predicted the LGM and LIG as the periods of narrowest and widest Cerrado distributions, respectively, and were largely corroborated by palynological evidence. We found evidence for two savanna corridors (eastern coastal during the LIG, and Andean during the LGM) and predicted a large refugial area in the north‐eastern Cerrado (Serra Geral de Goiás refugium). Variables related to climatic stability predicted squamate richness better than present climatic variables did. Main conclusions Our results indicate that Bolivian savannas should be included within the Cerrado range and that the Cerrado’s biogeographical counterparts are not Chaco and Caatinga but rather the disjunct savannas of the Guyana shield plateaus. Climatic stability is a good predictor of Cerrado squamate richness, and our stability maps could be used in future studies to test diversity patterns and genetic signatures of different taxonomic groups and as a higher‐order landscape biodiversity surrogate for conservation planning.

Areas of climate stability of species ranges in the Brazilian Cerrado: disentangling uncertainties through time

“…of species ecological niches. In the main, applications of ENMs for conservation purposes have been focused on two diverging approaches: 1) a 'looking forward' approach that seeks for areas of climate suitability in face of future scenarios of climate changes (e.g., Hannah et al 2007), and 2) a 'looking backward' approach that searches for historical refugia making the assumption that they encompass high biodiversity and endemism and thus must be preserved (e.g., Graham et al 2006;Werneck et al 2012). These approaches make the common implicit assumption that the temporal extent they consider (i.e., from present to past or to future periods separately) is sufficient to picture the whole range of climate variation that species can support (Smith & Boyer 2012).…”

“…We obtained the climate layers and characterized the environmental space for ENMs using climatic simulations from pre-industrial (representing current climate conditions), Last Glacial Maximum (LGM, 21,000 years ago -21 ky BP) and future (2080-2100, 20-year mean; hereafter 'end-of-century' -EOC), derived from four coupled Atmosphere-Ocean General Circulation Models (AOGCM) -CCSM4, GISS-E2-R, MIROC-ESM and MRI-CGCM3. We downloaded climate variables from AOGCM outputs (monthly simulation for precipitation, and mean, maximum and minimum temperature), which were downscaled to the same grid and used to compute the full range of bioclimatic variables defined in the WorldClim models correlate current climate and known species occurrences to predict the potential distribution of the species into the future, being now widely used to predict past distributions (e.g., Nogués-Bravo et al 2008) and identify areas of long-term climate stability (historical refugia) (e.g., Werneck et al 2012), as well as many other applications (see Peterson et al 2011 for a recent review). However, there are many uncertainties associated with the use of ENMs for forecasting or hindcasting climatically suitable areas, arising from differences in methods used for ENMs (e.g., Pearson et al 2006;Diniz-Filho et al 2010), the variety of simulations from Atmosphere-Ocean General Circulation Models (AOGCM) and greenhouse emission scenarios (Beaumont et al 2005), and the cut-offs used to transform estimates of suitabilities from the models into presence and absence (Nenzén & Araújo 2011).…”

“…Climatically stable areas in the past are frequently associated with high levels of diversity and endemism (e.g., Haffer 1969;Fjeldså et al 1999;Araújo et al 2008). In the future, areas of high climatic stability may perform a similar role protecting current biodiversity and thus they are considered to be very important as buffers to the impacts of rising global temperatures and wide climate changes in the 21 st century (Williams et al 2008;Werneck et al 2012). Identifying these areas and reducing the uncertainties about their location is a very useful task for biodiversity conservation because of the drastic shifts in the current distribution of climatically suitable areas for species and ecological communities that are expected to occur due to future climate changes.…”

MODELO PREDITIVO DO POTENCIAL DE DISTRIBUIÇÃO GEOGRÁFICA DA ESPÉCIE Richeria grandis VAHL. NO ESTADO DE MINAS GERAIS E SUA RELAÇÃO COM AS FLUTUAÇÕES CLIMÁTICAS DO QUATERNÁRIO

“…Os efeitos das flutuações climáticas sobre a vegetação do Cerrado durante o período Quaternário (WERNECK et al, 2012;BUENO et al 2017) confirmam que as formações florestais e as áreas de cerrado tiveram sucessivas expansões e retrações, promovendo áreas de conexão entre os domínios fitogeográficos. OLIVEIRA- FILHO & RATTER (2002) sugeriram que a rede formada por matas de galeria do Brasil Central funciona como corredores ecológicos, atuais e pretéritos interligando a floresta amazônica à floresta atlântica, no sentido noroeste-sudeste, representando um vetor de grande relevância para a compreensão dos padrões de distribuição das espécies.…”

“…Um método que vem sendo amplamente usado para a definição de áreas prioritárias para a conservação é a modelagem de nicho ecológico (WERNECK et al 2012;BUNGER et al 2016;BUENO et al 2017). Este método permite predizer a distribuição potencial de espécies, com base em áreas de ocorrência conhecidas, variáveis ambientais e em requerimentos ecológicos das mesmas, ou seja, características que compõem o nicho (PHILIPS et al, 2006;LIMA-RIBEIRO & DINIZ FILHO, 2012).…”