Abstract
Hyperdiverse tropical rainforests, such as the aseasonal forests in Southeast Asia, are supported by high annual rainfall. Its canopy is dominated by the species-rich tree family of Dipterocarpaceae (Asian dipterocarps), which has both ecological (e.g., supports flora and fauna) and economical (e.g., timber production) importance. Recent ecological studies suggested that rare irregular drought events may be an environmental stress and signal for the tropical trees. We assembled the genome of a widespread but near threatened dipterocarp, Shorea leprosula, and analyzed the transcriptome sequences of ten dipterocarp species representing seven genera. Comparative genomic and molecular dating analyses suggested a whole-genome duplication close to the Cretaceous-Paleogene extinction event followed by the diversification of major dipterocarp lineages (i.e. Dipterocarpoideae). Interestingly, the retained duplicated genes were enriched for genes upregulated by no-irrigation treatment. These findings provide molecular support for the relevance of drought for tropical trees despite the lack of an annual dry season.
Highlights
Hyperdiverse tropical rainforests, such as the aseasonal forests in Southeast Asia, are supported by high annual rainfall
We showed that an ancient whole-genome duplication (WGD) event coincided with the Cretaceous–Paleogene (K-Pg) boundary using the genome-wide data of 19 distribution-wide S. leprosula individuals as well as of 10 species from seven genera of Dipterocarpaceae
We sequenced the genome of S. leprosula using Illumina pairedend and mate-pair sequencing strategy, yielding sequence dataset of ~388-fold genome coverage
Summary
Hyperdiverse tropical rainforests, such as the aseasonal forests in Southeast Asia, are supported by high annual rainfall. Recent research has pursued the importance of rainfall variation and drought for promoting species distribution[4] and for triggering reproduction[5,6,7,8] in tropical forests, ecologists have longviewed light and soil characteristics as the main drivers of environmental filtering and species distributions in ever-wet tropical forests[9] Drought events in this system are often associated with irregular supra-annual El Niño Southern Oscillations (ENSO), and climate models project more frequent and severe ENSO events[10,11,12]. In support of the importance of inter-annual drought events, dipterocarp species appear to have maintained a functional response to drought at the community level, which promotes species coexistence[24] and diversity[25] and synchronizes reproduction[5,6,7,8] Besides their ecological importance, Asian dipterocarps lead the international tropical timber market, playing an important role in the economy of many countries within the region[26]. The availability of the genome assembly of a dipterocarp is of great utility for genetic conservation and plant breeding in facing global changes
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