Pinus pinea - EUFORGEN European forest genetic resources programme

Genetic summary

Genetic diversity and variation

Stone pine is genetically depauperate, with less genetic diversity than other pine species because of demographic collapse and a severe genetic bottleneck (Fady, Fineschi, and Vendramin, 2004; Jaramillo‐Correa et al., 2020). The genetic bottleneck in stone pine is likely the result of natural climatic fluctuations during the Quaternary (Vendramin et al., 2008). Severe population bottlenecking was likely not a single event but a trend of population collapse that continued through the Holocene and reduced ancestral stone pine populations to 1%–10% of their original size (Vendramin et al., 2008; Jaramillo‐Correa et al., 2020). The presence of one haplotype right across the range suggests that it may have survived in only a single population at some point in its history (Vendramin et al., 2008).

Gene flow may be restricted by stone pine’s reliance on seed dispersal by birds and the fact that cones take three years to mature (Jaramillo‐Correa et al., 2020). Restricted gene flow means mutations appearing after the species’ genetic decline are only locally dispersed and are more likely to be lost by genetic drift (Jaramillo‐Correa et al., 2020). Stone pine has maintained a low level of diversity while spreading across diverse and fragmented regions, which implies either mutations in the species are rare or that expansion was recent (Vendramin et al., 2008). Despite bottlenecking and low diversity, stone pine has managed to survive; this could be because the species shows a significant amount of genetic variation in adaptive traits considering its low genetic diversity, allowing it to expand into diverse habitats (Vendramin et al., 2008). For example, research has shown significant variation among provenances of stone pine for growth traits such as total height and growth rate (Carrasquinho and Gonçalves, 2013).

Genetic distribution and clustering

Despite its wide distribution, stone pine is known since the late 1970s to be genetically very uniform, when studies revealed that certain proteins were unexpectedly identical across many individuals and populations. There is no description in the literature of geographical races, ecotypes, or cultivars; however, one variety, P. pinea var. fragilis, which produces soft-shelled seeds, may be the result of a single mutation (Fady, Fineschi, and Vendramin, 2004). There is also no evidence of any strong geographic structure in adaptive traits such as vigour (Fady, Fineschi, and Vendramin, 2004). Studies have identified only four haplotypes around the Mediterranean; most populations contain a single haplotype, while Spanish populations contain another, and Lebanese populations contain two more (Fady, Fineschi, and Vendramin, 2004; Vendramin et al., 2008). The haplotypes observed in Spain and Lebanon are likely later mutations that occurred after the species’ genetic bottleneck.

The bibliographic review was conducted by James Chaplin of the EUFORGEN Secretariat in August 2024.

Further relevant genetic traits

Cultivation and human intervention

There is evidence that people were eating stone pine nuts 300 000 years ago, and that it has been cultivated for more than 6 000 years (Jaramillo‐Correa et al., 2020). The split between the eastern Mediterranean and Iberian populations probably took place about 9 500 years ago, around the same time as the earliest archaeological evidence for stone pine cultivation. Rapid and widespread range expansion and dispersion in the Holocene was probably human mediated as natural dispersion is low and colonization occurred very quickly and coincides with the beginning of widespread cultivation around 3 000 years ago (Mutke et al., 2019; Jaramillo‐Correa et al., 2020).

The bibliographic review was conducted by James Chaplin of the EUFORGEN Secretariat in August 2024.

Genetic conservation

Threats

Despite low genetic diversity stone pine is not considered a threatened species. It is rarely attacked by pests and diseases, although some insects are known to cause damage (Fady, Fineschi, and Vendramin, 2004). Forest fires are the main threat to stone pine genetic diversity, but stone pine is considerably less fire-sensitive than other species, given its thick bark and high crown devoid of low branches (Fady, Fineschi, and Vendramin, 2004). Fire is also necessary for natural stone pine regeneration.

Stone pine is highly sensitive to air pollution, especially when combined with other environmental stresses such as drought (Fady, Fineschi, and Vendramin, 2004). Widespread cultivation using the same genetic material has also likely contributed to the species’ reduced genetic diversity (Fady, Fineschi, and Vendramin, 2004).

Management

Analysis of stone pine genetic variability is inconsistent, hence research to help inform management would be beneficial (Carrasquinho and Gonçalves, 2013). Because of its uniform and low genetic diversity, much of the genetic variability within stone pine can be captured within a small number of individuals (Jaramillo‐Correa et al., 2020). However, research is still needed to determine whether current Mediterranean forests are really well adapted and truly natural, and to understand the history and ecology of this species (Fady, Fineschi, and Vendramin, 2004).

Establishment of in situ conservation networks, where selected populations are allowed to naturally regenerate without introduction of exotic material, is recommended (Fady, Fineschi, and Vendramin, 2004). Prioritization should be given to areas where extensive populations currently exist or with ecological extremes (Fady, Fineschi, and Vendramin, 2004). As many seed trees as possible should be left to maximize outcrossing and pollen flow in natural regeneration, including severely damaged/burned trees, to overcome the species low genetic diversity (Fady, Fineschi, and Vendramin, 2004). Stands should also implement fire- and overgrazing-protection measures.

The bibliographic review was conducted by James Chaplin of the EUFORGEN Secretariat in August 2024.

Pinus pinea
Stone pine

Environmental zones

Status of Pinus pinea conservation in Europe

Genetic summary

Genetic diversity and variation

Genetic distribution and clustering

Further relevant genetic traits

Cultivation and human intervention

Genetic conservation

Threats

Management

Genetic Characterisation of Pinus pinea and its GCUs

Availability of FRM

EUFORGEN’s publications

Technical guidelines for genetic conservation and use

Pinus pinea - Technical guidelines for genetic conservation and use for Italian stone pine

Related publications

Conifers Network: Report of the fifth meeting

Conifers Network: Report of the sixth meeting

Conifers Network: Report of the fourth meeting

Contacts of experts

Further reading

References

Pinus pineaStone pine

Environmental zones

Status of Pinus pinea conservation in Europe

Genetic summary

Genetic diversity and variation

Genetic distribution and clustering

Further relevant genetic traits

Cultivation and human intervention

Genetic conservation

Threats

Management

Genetic Characterisation of Pinus pinea and its GCUs

Availability of FRM

EUFORGEN’s publications

Technical guidelines for genetic conservation and use

Pinus pinea - Technical guidelines for genetic conservation and use for Italian stone pine

Related publications

Conifers Network: Report of the fifth meeting

Conifers Network: Report of the sixth meeting

Conifers Network: Report of the fourth meeting

Contacts of experts

Further reading

References

Pinus pinea
Stone pine