Lignotuber resprouting in Juniperus signals the onset of the Mediterranean climate

The Juniperus group oxycedrus consists of needle-leaved junipers with red cones found across the Mediterranean Basin (South Europe and North Africa) and the Macaronesian islands. The group includes at least 5 recognised varieties or subspecies (oxycedrus, badia, macrocarpa, cedrus, maderensis [1]). Of these five, only one (ssp. oxycedrus) can resprout after a high-intensity fire thanks to its lignotuber (Fig. 1; an ontogenetic basal burl that stores buds [2,3]). J. oxycedrus ssp. oxycedrus is common in lowland shrublands of the western Mediterranean Basin, especially in the coastal mountains of eastern Iberia (Spain).

A recent phylogenomic analysis [4] suggested that the ability to resprout likely appeared about 6 million years ago. That is, during the late Miocene, junipers likely experienced a strong selective pressure from frequent fires. The acquisition of lignotuber resprouting in Juniperus oxycedrus is an indicator of a fire regime shift likely due to the onset of the Mediterranean climate. By tracing the evolutionary acquisition of resprouting in J. oxycedrus, this study provides a novel indicator of an intensification of fire regimes during the late Miocene [4]. That points to fire as an evolutionary pressure intrinsically linked to the Mediterranean biome.

This also highlights an interesting botanical point: it is not easy to differentiate Juniperus oxycedrus ssp. oxycedrus from ssp. badia either on a herbarium sheet or in the field, unless they've been burned! After a fire, ssp. oxycedrus resprouts vigorously from a lignotuber, whereas ssp. badia does not.

References

[1] Gutiérrez-Larruscain D, Vargas P, Fernández-Mazuecos M, Pausas JG. 2024. Phylogenomic analysis reveals the evolutionary history of Paleartic needle-leaved junipers. Mol Phylogen Evol 199: 108162. [doi | sciencedirect | pdf]

[2] Pausas JG, Lamont BB, Paula S, Appezzato-da-Glória B & Fidelis A. 2018. Unearthing belowground bud banks in fire-prone ecosystems. New Phytol 217: 1435–1448. [doi | pdf | suppl. | BBB database]

[3] Paula S, Naulin PI, Arce C, Galaz C & Pausas JG. 2016. Lignotubers in Mediterranean basin plants. Plant Ecol 217: 661-676. [doi | pdf | suppl.]

[4] Gutiérrez-Larruscain D, Vargas P, Pausas JG. 2025. Phylogenomic evidence of fire regime changes: the case of a resprouting juniper. Ecol Lett 28(7): e70169 [doi | wiley | pdf] <- New paper!