- Increases in leaf mass per area (LMA) are commonly observed in response to environmental stresses and are achieved through increases in leaf thickness and/or leaf density. Here, we investigated how the two underlying components of LMA differ in relation to species native climates and phylogeny, across deciduous and evergreen species.
- Using a phylogenetic approach, we quantified anatomical, compositional and climatic variables from 40 deciduous and 45 evergreen Quercus species from across the Northern Hemisphere growing in a common garden.
- Deciduous species from shorter growing seasons tended to have leaves with lower LMA and leaf thickness than those from longer growing seasons, while the opposite pattern was found for evergreens. For both habits, LMA and thickness increased in arid environments. However, this shift was associated with increased leaf density in evergreens but reduced density in deciduous species.
- Deciduous and evergreen oaks showed fundamental leaf morphological differences that revealed a diverse adaptive response. While LMA in deciduous species may have diversified in tight coordination with thickness mainly modulated by aridity, diversification of LMA within evergreens appears to be dependent on the infrageneric group, with diversification in leaf thickness modulated by both aridity and cold, while diversification in leaf density is only modulated by aridity.
Acknowledgements. Financial support from Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA) grant no. RTA2015-00054-C02-01, from Ministerio de Ciencia e Innovación grant number PID2019-106701RR-I00 and from Gobierno de Aragón H09_20R research group. The work of DAF was supported by a FPI-INIA contract BES-2017-081208. The work of CS was supported by a National Science Foundation (NSF)-CAREER grant no. 231715. We thank Elena Martí Beltrán for her valuable help searching the species distribution and obtaining the climatic data. We thank Ruth Cuevas Calvo for helping in the anatomy cross-section process. We thank Francisco Garin García for his meaningful support in the recollection of oak leaves and identification of the species leaf habit. We also thank Jardín Botánico de Iturrarán for allowing us to collect oak leaf samples from their garden. Finally, we would like to thank the anonymous reviewers for their careful reading of our manuscript and their insightful and valuable suggestions.
