Diversidade, taxonomia e ecologia de leveduras associadas a bromélias da caatinga no Estado de Alagoas/Brasil

Abstract

The Caatinga is a Seasonally Dry Tropical Forest that occupies 10% of the Brazilian territory and great part of the Northeast region. Its main characteristics are its low and irregular rains that cause long periods of drought. The Caatinga is currently experiencing the most severe drought of the last century and processes such as climate change can intensify this situation. Yeasts are recurrent colonizers of the phylloplane and, in this environment, are subject to nutrient fluctuations, temperature and water availability. Knowledge about the diversity and dynamics of the epiphytic yeast community is still insipient, especially in semi-arid environments such as the Caatinga. Therefore, our aim was to verify the temporal and spatial dynamics of the community of epiphytic yeasts associated with bromeliads in the Caatinga, to identify the possible influence of the rains and to describe possible new species of yeasts. For this, leaves, flowers and fruits of adult and healthy bromeliads were collected, washed and the final product sown on modified YM agar and incubated for 5-7 days. For the molecular identification of the isolates, the D1/D2 LSU rDNA region were amplified and sequenced. Species suspected of being undescribed are in the process of being described, for this the Internal Transcribed Spacer (ITS) rDNA region was further sequenced and the isolates were subjected to the polyphasic taxonomy method. A total of 209 isolates and 85 yeast species were obtained (82 in leaves, 9 in fruits and 6 in flowers), of which more than one third (n = 29) are possible undescribed species. If all possible new yeast species found only in this study were described this would increase the yeast richness described by about 2%. Among the undescribed species, it is worth mentioning Vishniacozyma sp., Which occurred in about 20% of collected leaf samples and is in an advanced process of description. In addition, we verified that the composition of the yeast community tends to vary in the temporal and spatial dimension and that the rains had a positive relation with the diversity and negative with the abundance of the yeasts. These results indicate that the bromeliad phylloplane in the Caatinga is rich in yeast species, including many species not described, and that this community is extremely dynamic and may be related to the rainfall regime.