Local adaptative strategies for coping with drought stress in Neltuma alba (Leguminosae, Caesalpinioideae) are associated with the timing of leaf senescence

Abstract

Drought stress is a significant abiotic factor that limits plant growth and has led to widespread tree mortality worldwide. As climate change predicts longer, more severe, and unpredictable drought periods in subtropical regions, understanding how forest ecosystems cope with such stress becomes critical. This study focuses on Neltuma alba, a drought-tolerant tree species commonly found in the Gran Chaco Americano region of South America. We investigated the coexistence of different behaviors to cope with drought stress in N. alba and searched for signals of local adaptation in its populations. Using a combination of macroscopic leaf morphological traits and genetic (molecular) information in common garden experiments, we identified four behaviors in N. alba plants for coping with drought stress. These behaviors were associated with the timing of leaf senescence and survival under drought stress. Genetic markers revealed high levels of diversity within populations, providing potential for adaptive responses to changing environmental conditions. Furthermore, we observed local adaptation, with populations exhibiting distinct leaf morphological traits related to water use efficiency and transpiration rates. These traits reflect the natural selection imposed by different water regimes in each population. In conclusion, this study enriches our understanding of N. alba’s adaptive responses to drought stress and highlights the importance of considering intraspecific functional diversity and local adaptation in forest management and conservation efforts. The findings can guide the selection of drought-tolerant provenances for reforestation projects and contribute to maintaining the evolutionary resilience of forest populations in the face of climate change.