Genetic differentiation in leaf phenology among natural populations of Adansonia digitata L. follows climatic clines

Haby Sanou,Erik D Kjær,Anders Ræbild,Hawa Bamba,Adama Korbo,Jon K Hansen

doi:10.1016/j.gecco.2019.e00544

Haby Sanou, Erik D Kjær + Show 4 more

Open Access

https://doi.org/10.1016/j.gecco.2019.e00544

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Abstract

Leafing phenology is an important component of climatic adaptation in semi-arid regions. The questions are to what extent phenology is under genetic control and represent adaptation to local climates? In the present study, we compare leaf phenology among Adansonia digitata L. trees of 27 different origins from West and East Africa and test if the differences follow climatic clines. Timing of bud burst was largely synchronized with the start of rainy season, but some few individual trees showed bud burst before the first rain. Timing of leaf senescence was under genetic control with substantial differences among origins. The timing of senescence was for some origins at the end of rainy season and for some in the beginning of the dry season. Differences among origins in timing of leaf senescence were related to the variation in drought just before- and in the first months of the rainy season at the sites of origin. Populations from drier sites had the earliest leaf shed at the common test site indicating that trees have been adapted to the prevailing climatic conditions at the sites of origin. We discuss the results in the light of possible triggering factors.

Highlights

Tropical trees in many arid and semi-arid environments with a marked seasonality in rainfall have phenology synchronized to the periods of humidity and aridity
We examine the variability in leaf phenology of A. digitata originating from different geographic and climatic zones, and test if the differences among origins follow geographical or climatic clines
The growth of the plants from May 2009 to May 2011, and survival in the nursery are reported in Korbo et al (2012), while the present study reports the variation in phenology in 2012 and 2013 among the different origins

Summary

Introduction

Tropical trees in many arid and semi-arid environments with a marked seasonality in rainfall have phenology synchronized to the periods of humidity and aridity. Studies of genetic variation in phenology of tropical trees of temporal dry zones are rare (Ræbild et al., 2011). It is not clear whether reported differences in phenology are purely phenotypic reactions to varying environmental conditions, or whether there are genetic differences between origins, reflecting adaptation to the prevailing climate. This is a serious lack of knowledge, as climate change may challenge a current adaptation of trees to their local growth conditions (Ouedrago, 2014). The development in annual precipitation is more uncertain (Niang et al, 2014), but there is a risk for shorter rainy seasons with extreme precipitation in West Africa (Sylla et al, 2016)

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