Effects of Quaternary Climatic Fluctuations on the Distribution of Neotropical Savanna Tree Species

摘要

In order to develop niche models for tree species characteristic of thecerrado vegetation (woody savannas) of central South America, and tohindcast their distributions during the Last Glacial Maximum and Last Inter-Glacial, we compiled a dataset of tree species checklists for typical cerradovegetation (n=282) and other geographically co-occurring vegetationtypes, e.g. seasonally dry tropical forest (n=355). We then performed anIndicator Species Analysis to select ten species that best characterizetypical cerrado vegetation and developed niche models for them using theMaxent algorithm. We used these models to assess the probability ofoccurrence of each species across South America at the following timeslices: Current (0 ka pre-industrial), Holocene (6 ka BP), Last GlacialMaximum (LGM - 21 ka BP), and Last Interglacial (LIG - 130 ka BP). Theniche models were robust for all species and showed the highest probabilityof occurrence in the core area of the Cerrado Domain. The palaeomodelssuggested changes in the distributions of cerrado tree species throughoutthe Quaternary, with expansion during the LIG into the adjacentAmazonian and Atlantic moist forests, as well as connections with otherSouth American savannas. The LGM models suggested a retraction ofcerrado vegetation to inter-tableland depressions and slopes of the CentralBrazilian Highlands. Contrary to previous hypotheses, such as thePleistocene Refuge Theory, we found that the widest expansion of cerradotree species seems to have occurred during the LIG, most probably due toits warmer climate. On the other hand, the postulated retractions duringthe LGM were likely related to both decreased precipitation andtemperature. These results are congruent with palynological andphylogeographic studies in the Cerrado Domain.