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Serotiny and WWI memorials

April 27th, 2021 No comments

On ANZAC Day (25 April; the national day of Australia, see wikipedia) I received the following query from an Australian colleague.

Apparently one of the few Australian soldiers that survived the Gallipoli battle (Turkey, 1915, WWI) picked up a pine cone (from a ‘Lone pine’), and took it back to Australia. The cone was kept on a shelf until 1933 when a horticulturalist extracted 5 seeds and germinated them. The seedlings were planted in botanic gardens; the 78-year-old trees now have special symbolic value to war veterans and the like (Fig. 1). The returned veterans are often referred to as ‘lone pine soldiers’ (and the battle, as the battle of the lone pine). My colleague asked me if the cone story had some credibility, for instance, would a pine seed germinate after 18 years?

Fig. 1. Plaque at the foot of pine tree in Kings Park, Perth, Western Australia. From [4]

The plaque in Kings Park (Fig. 1) suggest that the pine is a Pinus halepensis (Aleppo pine). However, the pines in Gallipoli peninsula (and in most Turkey) are of another species: Pinus brutia (Turkish Red Pine) [2]; the two species are very close related. So the cone that the soldier pick up should be a P. brutia, unless there was a plantation of P. halepensis there.

Pine seed, once there are out of the cone, do not last for long (mostly less than a year). However one of the characteristics of both P. halepensis and P. brutia is that they have some serotinous cones (the serotiny level is higher in P. halepensis than P. brutia, but both have a proportion of serotinous cones) [2,3]. Serotinous cones are those that remain closed after maturation, i.e., more than a year [1]. They accumulate for several years, forming a canopy seed bank; these cones open after the tree burns in a wildfire, and thus it is an adaptation to regenerate after fire [1]. At least in the case of P. halepensis, we have evidence that cones remaining close on the tree for many years; most cones open in less than 8 years, but some can last more than 15 years (Fig. 2). In addition we have evidence of cones remaining closed after harvest (at lest 12 years in my experience). This information is for P. halepensis, but could apply to P. brutia as well.

Fig. 2. Left: Frequency distribution of trees in relation to their maximum closed cone age for Pinus halepensis in eastern Spain. The gray pattern corresponds to the proportion of trees in population under high frequency of crown fires, the white to the proportion of trees where crown fires are rare. From [3]. Right: example of long-lived serotinous cones in P. halepensis in eastern Spain.

In conclusion, the Australian soldier may have picked up a serotinous cone, perhaps from a P. brutia. The seed were in the cone for 18 years and then extracted and planted. There are other accounts suggesting that several Australian soldiers took cones of both P. brutia, and P. halepensis (it’s difficult to understand why soldiers would collect pine cones after such a deadly battle, but this is another question …).

Currently most WWI memorials in Australia include a P. halepensis tree, a few a P. brutia. In the memorial cemetery near Gallipoli they planted (in the 1920s) a different pine, a Pinus pinea (stone pine, not native from Turkey, but from Italy and Spain). And in New Zealand (they shared with Australians the Gallipoli drama), the tree in ANZAC memorials includes Pinus radiata (from California) and Pinus canariensis (from Canary Islands, west Africa). That is, any of the ca. 120 pine species may do for a war memorial…

If Gallipoli has not been a fire-prone ecosystem, the pines would not be serotinous, the cones collected by the soldiers would not had kept the seeds, and we would not have pines in the Australian and New Zealand war memorials. So now, when you see a pine in a war memorial, just think about fire adaptations!

References

[1] Lamont BB, Pausas JG, He T, Witkowski, ETF, Hanley ME. 2020. Fire as a selective agent for both serotiny and nonserotiny over space and time. Crit. Rev. Plant Sci. 39:140-172. [doi | pdf | suppl.]  

[2] Pinus brutia jgpausas.blogs.uv.es/2017/04/19/

[3] Hernández-Serrano A., Verdú M., González-Martínez S.C., Pausas J.G. 2013. Fire structures pine serotiny at different scales. Amer. J. Bot. 100: 2349-2356. [doi | amjbot | pdf | supp.]  

[4] For more about the lone pine puzzle see: Underwood R. 2014  quadrant.org.au | wikipedia

More on serotiny|

 

Pinus yunnanesis

January 16th, 2021 2 comments

In the Yunnan Province of China, P. yunnanensis occurs in two growth forms: as a tree (var. yunnanensis) and as a shrub (var. pygmea) [1]. The shrubby form occurs mainly in upper slopes and ridges (Fig. 1), where soils are poor and dry, and fires are likely. This shrubby pine is very interesting and quite unique among pines: it has serotinous cones (Fig. 2), and resprouts after fire from basal buds (Fig. 3), generating multi-stemmed shrubby pine populations [1]. Serotiny is common among pines [2] while resprouting is not [3], so pines with both serotiny and resprouting are rare; and having a multi-stemmed growth form is even rarer.

Fig. 1. Pine shrubland (Pinus yunnanensis var. pygmea) in Yunnan, China. Photo C. Luo [1]
Fig. 2. Pinus yunnanensis var. pygmea showing serotinous cones, Yunnan, China. Photo: W.-H. Su [1]
Fig. 3. Pinus yunnanensis var. pygmea resprouting from basal buds after a fire, Yunnan, China. Photo: JG Pausas [1]

References

[1] Pausas JG, Su W-H, Luo C, & Shen Z. 2021. A shrubby resprouting pine with serotinous cones endemic to Southwest China. Ecology [doi | pdf]

[2] He T, Pausas JG, Belcher CM, Schwilk DW, Lamont BB. 2012. Fire-adapted traits of Pinus arose in the fiery Cretaceous. New Phytol. 194: 751-759. [doi | wiley | pdf | suppl.]

[3] Pausas, J.G. 2015. Evolutionary fire ecology: lessons learned from pines. Trends Pl. Sci. 20: 318-324. [doi | sciencedirect | cell | pdf]

Pine serotiny

November 14th, 2020 No comments

Some days ago I asked this question on Twitter.

What is the difference between the top and bottom pine cones in this photo? This is a question I often ask to my new students in the first field trip; in this case, Beniardà fire, 2020 [link]

These cones are from Pinus halepensis and were collected after a wildfire in Beniardà (Alicante, E Spain; burned in Aug 2020).

Many of you reply correctly; here is the full answer:

Top cones: before the fire, they were open on on the tree, i.e., without seeds. Fire burn them, and so they are all black

Bottom cones (see also the picture below): before the fire they were closed (serotinous cones), and fire opened them facilitating seed dispersal. Note that they are unburned inside. These cones contribute to the postfire regeneration of the pine.

Serotinous cones in Pinus halepensis: before (left) and after a fire (right)

 

References

  • Lamont BB, Pausas JG, He T, Witkowski, ETF, Hanley ME. 2020. Fire as a selective agent for both serotiny and nonserotiny over space and time. Critical Reviews Plant Sci 39:140-172. [doi | pdf | suppl.]
  • Pausas JG. 2015. Evolutionary fire ecology: lessons learned from pines. Trends Plant Sci 20: 318-324. [doi | sciencedirect | cell | pdf]
  • Castellanos MC, González-Martínez S. & Pausas JG. 2015. Field heritability of a plant adaptation to fire in heterogeneous landscapes. Mol Ecol 24: 5633-5642. [doi | pdf | suppl.]
  • Hernández-Serrano A, Verdú M, González-Martínez SC, Pausas JG. 2013. Fire structures pine serotiny at different scales. Am J Bot 100: 2349-2356. [doi | amjbot | pdf | supp.]
  • Hernández-Serrano A, Verdú M, Santos-Del-Blanco L, Climent J, González-Martínez SC & Pausas JG. 2014. Heritability and quantitative genetic divergence of serotiny, a fire-persistence plant trait. Ann Bot 114: 571-577. [doi | pdf | suppl.]

 

More on serotiny: Serotiny: a review | Pinus brutia | Heritability of serotiny | Heritability of serotiny (2) | Evolutionary fire ecology in plants | Serotiny |

Serotiny: a review

June 9th, 2020 No comments

Here is a new review paper on serotiny in plants [1]. Serotiny refers to prolonged storage of seeds in woody structures (cones or fruits) on the mother plant for several growing seasons. This implies an accumulation of a canopy seed bank with seeds from different. Serotiny confer fitness benefits in environments with frequent crown-fires, as the heat of the fires opens the woody structures and thus seeds are dispersed in the post-fire bed (where resource are abundant and competition is low). There are other ways by which some cone/fruit can be opened (e.g., dry warm winds), but the number of seeds released and the chance of successful recruitment are much lower than in postfire conditions, and thus fire provides higher fitness benefits for serotinous plants than any other cue factor. This is why most serotinous plants occurs in ecosystems with frequent crown fires. Serotiny has been studied mainly in pines [2-4] and Proteaceae, but we know at least 12 families and more than 50 genera with serotinous species [1]. And there is a diversity of serotinous structures (cones and fruits) in different genera and families (Fig. 1).

Figure 1. A) Callitris (Actinostrobus) pyramidalis (Cupressaceae); B) Postfire Cupressus sempervirens (Cupressaceae); C) Cone of Pinus patula; D) Postfire cones of Pinus radiata; E) Folicles of Hakea cyclocarpa (Proteaceae); F) Hakea stenocarpa follicle; G) Follicles of H. platysperma; H) Xylomelum angustifolium (Proteaceae) follicle; I) Lambertia echinata (Proteaceae) follicle; J) Cone of Banksia lemanniana (Proteaceae); K) B. hookeriana burning; L) Postfire B. leptophylla cone; M) Cluster of capsules of Leptospermum spinescens (Myrtaceae), inset: seeds of Callistemon (Melaleuca) teretifolius; N) Elongated cluster of sessile capsules of Callistemon citrinus (Myrtaceae), + seeds of Callistemon (Melaleuca) teretifolius; O) Woody capsules of Eucalyptus todtiana (Myrtaceae), Inset: capsules of Angophora hispida (Myrtaceae); P) Spikes of Connomois parviflora (Restionaceae); Q) Protea burchellii (Proteaceae); R) fruits of Protea burchellii; S) Cone of Allocasuarina torulosus (Casuarinaceae); T) Cone of Isopogon trilobus (Proteaceae); U) Cones of Petrophile brevifolia; V) Seedlings from serotinous H. polyanthema, B. attenuata and B. hookeriana in litter microsite. For more details see [1].

References

[1] Lamont BB, Pausas JG, He T, Witkowski, ETF, Hanley ME. 2020. Fire as a selective agent for both serotiny and nonserotiny over space and time. Critical Rev. Plant Sci. [doi | pdf]

[2] Hernández-Serrano A, Verdú M, González-Martínez SC, Pausas JG. 2013. Fire structures pine serotiny at different scales. Am. J. Bot. 100: 2349-2356. [doi | amjbot | pdf | supp.]

[3] Hernández-Serrano A, Verdú M, Santos-Del-Blanco L, Climent J, González-Martínez SC, Pausas JG. 2014. Heritability and quantitative genetic divergence of serotiny, a fire-persistence plant trait. Ann. Bot. 114: 571-577. [doi | pdf | suppl.]

[4] Castellanos MC, González-Martínez S, Pausas JG. 2015. Field heritability of a plant adaptation to fire in heterogeneous landscapes. Mol. Ecol. 24, 5633-5642. [doi | pdf | suppl.]  

 

More on serotiny: Serotiny | Heritability of serotiny (1) | Heritability of serotiny (2): a molecular approach | Evolutionay fire ecology in pines 

A fire ecology lesson from the Florida scrub

June 11th, 2018 No comments

Fire is a key ecological factor in many Mediterranean shrublands [1]. But there is another shrubland, the Florida scrub, that share many characteristics with mediterranean ecosystems. Fire is frequent in the Florida scrub, and most plant strategies to deal with fire are the same to those found in mediterranean ecosystems, despite the species are different (a likely case of convergent evolution). The Florida scrub occurs on sandy soils of the Florida Peninsula (USA), under a subtropical climate.

Eric Menges, a fire ecologist at Archbold Biological Station in Florida, explains in this 16-minute video the main adaptive traits of plants to live in the Florida scrub. In his words “the lack of fire is a bigger disturbance than the fire”. All strategies explained in the video also occur in most mediterranean regions, including the Mediterranean Basin (i.e., from Portugal to Syria).

Video “Surviving fire in the Florida scrub”, also available in youtube.

[Versión en español]

El fuego es un factor ecológico clave en muchos matorrales mediterráneos [1,2]. Pero hay otro matorral, el matorral de la Florida, que comparte muchas características con los ecosistemas mediterráneos. El fuego también es frecuente en este matorral, y la mayoría de las estrategias de las plantas para persistir después de incendio son las mismas que las que se encuentran en los ecosistemas mediterráneos, a pesar de que las especies son diferentes (con ejemplos de evolución convergente). El matorral de Florida aparece en suelos arenosos en la península de la Florida (EEUU), en clima subtropical.

Eric Menges, ecólogo en la Estación Biológica Archbold en Florida, explica en este video de 16 minutos los principales estrategias adaptativas de las plantas para vivir en el matorral de Florida. En sus palabras, “la falta de fuego es una perturbación más importante que el fuego”. Todas las estrategias explicadas en el video también ocurren en la mayoría de las regiones mediterráneas, incluida la Cuenca Mediterránea (de Portugal a Siria, pasando por España, claro).

 

References

[1] Keeley J.E., Bond W.J., Bradstock R.A., Pausas J.G. & Rundel P.W. 2012. Fire in Mediterranean Ecosystems: Ecology, Evolution and Management. Cambridge University Press. [the book]

[2] Pausas J.G. 2012. Incendios forestales. Una visión desde la ecología. Catarata-CSIC. [Libro]

 

Chile 2017 fires: fire-prone forest plantations

September 16th, 2017 No comments

During the 2016/17 fire season in central Chile, wildfires burned about 600,000 ha, a record for the region (most of the area burned between 18-Jan and 5-Feb, 2017). Two factors are considered the main responsible of such a large area burned: (1) an intense drought with strong head waves (January was the hottest month in record), and (2) the fact that the region is covered by large and dense tree plantations that create a continuous fuel bed. The tree planted are two alien species: Pinus radiata and Eucalyptus sp., from California and Australia, respectively. Most burned area (+60%) were plantations, and if we standardize the area burned in relation to the area with each landuse in the region (plantations, native forest, grasslands, agriculture) we see that the plantations were more affected by fire than expected by their area in each region; and this contrast with the other landuses (Figure 1, [1]). That is, tree plantations were an important driver for the large area burned (highly flammable).

Interesting is that the two species planted not only are highly flammable, they also have very good (although very different) postfire regeneration mechanisms, because both are originally from fire-prone ecosystems and have adapted to coupe with crown fires. Pinus radiata have serotinous cones (closed cones that open with fire) and showed an extraordinary “natural” seedling regeneration postfire (Figure 2 top), while those eucalytps planted show epicormic (stem) resprouting that allows a quick canopy recovery (even young trees, Figure 2 bottom). All suggest that these plantations were born to burn!

Figure 1: Analysis of the areas affected by fires according to types of use (forest plantations, native forest, Scrubland + pastures, and agricultural areas), in relation to what is available in each of the 4 regions that have burned the most (V, RM, VI, VII are: Valparaiso, Metropolitana, O’Higgins, and Maule). Positive data means that fire has positively selected this type of use (it has burned more than expected by the area it occupies); the negative data indicate that fire tends to avoid such landuse. There is a strong tendency for plantations to burn more than expected according to their abundance in the landscape (positive values), while native forests, scrub, or agricultural areas are burned similar or less than expected according to their abundance (negative values). The region VII (Maule) is the most extreme in positive selection of plantations and negative of other uses. Elaborated on the basis of official SIDCO-CONAF data (Chile) [1].

 


Figure. 2. Postfire regeneration of tree plantations. Top: Extraordinary postfire seedlings regeneration of Pinus radiata (adult trees are dead). Bottom: epicormic resprouting of eucalypts (mixed with dead pines). Photos from early September (ca. 7 months after fire), in the Nilahue Barahona fire (O’Higgins region, Chile).

References

[1] Incendios en Chile 2017, jgpausas.blogs.uv.es/2017/02/10

More information on:  Chile and fires | Serotiny | Epicormic resprouting

UPDATE (Jan 2019): this post and this other have inspired the following article:

Leverkus AB, Murillo PG, Doña VJ, Pausas JG. 2019. Wildfires: opportunity for restoration? Science 363 (6423): 134-135. [doi | science | pdf]

 

Pinus brutia

April 19th, 2017 No comments

Pinus halepensis is a strongly serotinous pine [1,2] occurring mainly in the western part of the Mediterranean Basin (especially in Spain; see map below). The most phylogenetically closely related species to P. halepensis is Pinus brutia that occurs in the eastern Mediterranean Basin (mainly in Turkey). P. brutia is called ‘red pine’ in Turkish (Kızıl çam) because sometimes the upper part of the trunk is reddish (as in P. sylvestris); the leaves are pale green as in P. halepensis. In relation to their fire response strategy [3], the main differences between the two species are that P. brutia is taller, the bark is thicker and the serotiny level is lower. Our observations suggest that P. brutia have relatively few serotinous cones, and most of then are less than 4 years old; P. halepensis have a higher proportion of serotinous cones, with many of them over 5 year old (and some more than 20 year old) [1].

Distribution maps of P. halepensis and P. brutia (from Wikipedia)

 
Pinus brutia forest, serotinous cones (2 serotinous and one non-serotinous (open)), and an example of a bark of more than 5 cm thick (the gaude was too short!). Photos from SW Turkey (by JG Pausas). For an example of serotinous cones in P. halepensis, see here.

 

References
[1] Hernandez-Serrano A., Verdú M., González-Martínez S.C., Pausas J.G. 2013. Fire structures pine serotiny at different scales. Am. J. Bot. 100: 2349-2356. [doi | pdf | supp.]

[2] Castellanos, M.C., González-Martínez, S. & Pausas, J.G. 2015. Field heritability of a plant adaptation to fire in heterogeneous landscapes. Mol. Ecol. 24, 5633-5642. [doi | pdf | suppl. | blog]

[3] Pausas, J.G. 2015. Evolutionary fire ecology: lessons learned from pines. Trends Pl. Sci. 20: 318-324. [doi | pdf | blog]

Heritability of serotiny (2): a molecular approach

December 2nd, 2015 No comments

Not long ago we demonstrated that serotiny (i.e., the capacity to accumulate a seed bank in the canopy until the seeds are released by fire) is an heritable trait in pines [1]. This analysis was based on a classical provenance – progeny common garden experiment. However, trait variability under controlled environmental conditions may not fully reflect the variability observed in the field, and thus this estimate of heritability may not reflect how traits respond to natural selection. This is because there is higher environmental variability in the field and also because garden experiments typically include individuals that would not survive in the field (i.e., artificially increases progeny survival) [2]. With the aim of obtaining a more realistic estimate of heritability of serotiny, we have recently estimate it directly in the field for two pine species (P. halepensis, P. pinaster) [3]. Because in the field it is not possible to construct a pedigree, we used the relatedness among individuals estimated from molecular markers (SNPs) for the same individuals from which we had estimated serotiny previously [4]. The variance in serotiny was modelled incorporating the environmental variability (climate and fire regime) using a Bayesian ‘animal model’. As expected, field heritability was smaller (around 0.10 for both species) than previous estimates under common garden conditions (0.20). The difference is not surprising because wild P. halepensis and P. pinaster populations extend over heterogeneous landscapes with large environmental variations. Our results highlight the importance of measuring quantitative genetic parameters in natural populations, where environmental heterogeneity is a critical aspect. The heritability of serotiny, although not high, combined with high phenotypic variance within populations, confirms the potential of this fire-related trait for evolutionary change in the wild [2].

Pinus patula
Fig: Serotinous cones of P, halepensis and P. pinaster can be observed in previous posts (P, halepensis, P. pinaster). The photo here shows serotinous cones of Pinus patula from central Mexico (in a foggy rainy day).

References

[1] Hernández-Serrano, A., Verdú, M., Santos-Del-Blanco, L., Climent, J., González-Martínez, S.C. & Pausas, J.G. 2014. Heritability and quantitative genetic divergence of serotiny, a fire-persistence plant trait. Annals of Botany 114: 571-577.  [doi | pdf | suppl. | blog]

[2] Pausas, J.G. 2015. Evolutionary fire ecology: lessons learned from pines. Trends in Plant Science 20: 318-324. [doi | sciencedirect | cell | pdf]

[3] Castellanos, M.C., González-Martínez, S. & Pausas, J.G. 2015. Field heritability of a plant adaptation to fire in heterogeneous landscapes. Molecular Ecology 24: 5633–5642 [doi | pdf | suppl.]

[4] Hernández-Serrano A., Verdú M., González-Martínez S.C., Pausas J.G. 2013. Fire structures pine serotiny at different scales. American Journal of Botany 100: 2349-2356. [doi | amjbot | pdf | supp. | blog]

 

Fire adaptations in Mediterranean Basin plants

September 7th, 2015 No comments

Few days ago a botanist colleague ask me whether there were some fire adaptations in the plants of the Mediterranean Basin, similar to those reported in other mediterraenan-climate regions. So I realised that researchers working on other topics may not be aware of the recent advances in this area. Here is my brief answer, i.e., some examples of species growing in Spain that show fire adaptations; this is by no means an exhaustive list, but a few examples of common species for illustrative purpose. You can find a description of these adaptations and further examples elsewhere [1, 2, 3, 4]. It is also important to note that plants are not adapted to fire per se, but to specific fire regimes, and thus some adaptations my provide persistence to some fire regimes but not to all [1]. That is, species that exhibit traits that are adaptive under a particular fire regime can be threatened when that regime changes.

  • Serotiny (canopy seed storage): Pinus halepensis, Pinus pinaster, with variability in serotiny driven by different fire regimes [5, 6]
  • Fire-stimulated germination: There are examples of heat-stimulated germination, like many Cistaceae (e.g., Cistus, Fumana [7, 8]) and many Fabaceae (e.g., Ulex parviflorus, Anthyllis cytisoides [7, 8]), as well as examples of smoke-stimulated germination like many Lamiaceae (e.g., Rosmarinus officinalis, Lavandula latifolia [7]) or Coris monspeliensis (Primulaceae [7]). There are also examples of species with smoke-stimulated seedling growth (Lavandula latifolia [7])
  • Resprouting from lignotubers: Arbutus unedo, Phillyrea angustifolia, Juniperus oxycedrus, many Erica species (e.g., E. multiflora, E. arborea, E. scoparia, E. australis) [4, 17]
  • Epicormic resprouting: Quercus suber [9, 10], Pinus canariensis [4]
  • Fire-stimulated flowering: Some monocots like species of Asphodelus, Iris, Narcissus [11, 12]
  • Enhanced flammability: Ulex parviflorus shows variability of flammability driven by different fire regimes [13] and under genetic control [14]. Many Lamiaceae species have volatile organic compounds that enhance flammability (e.g., Rosmarinus officinalis [16]).
  • Thick bark and self-pruning (in understory fires): Pinus nigra [3,15]

 

fireadaptations2

References

[1] Keeley et al. 2011. Fire as an evolutionary pressure shaping plant traits. Trends Plant Sci 16:406-411. [doi | pdf]

[2] Keeley et al. 2012. Fire in Mediterranean Ecosystems. Cambridge University Press. [book]

[3] Pausas JG. 2012. Incendios forestales. Catarata-CSIC. [book]

[4] Paula et al. 2009. Fire-related traits for plant species of the Mediterranean Basin. Ecology 90:1420-1420. [doi | pdf | BROT database]

[5] Hernández-Serrano et al. 2013. Fire structures pine serotiny at different scales. Am J Bot 100:2349-2356. [doi | pdf]

[6] Hernández-Serrano et al. 2014. Heritability and quantitative genetic divergence of serotiny, a fire persistence plant trait. Ann Bot 114:571-577. [doi | pdf]

[7] Moreira et al. 2010. Disentangling the role of heat and smoke as germination cues in Mediterranean Basin flora. Ann Bot 105:627-635. [doi | pdf]

[8] Moreira B and Pausas JG. 2012. Tanned or Burned: the role of fire in shaping physical seed dormancy. PLoS ONE 7:e51523. [doi | plos | pdf]

[9] Pausas JG. 1997. Resprouting of Quercus suber in NE Spain after fire. J Veget Sci 8:703-706. [doi | pdf]

[10] Catry et al. 2012. Cork oak vulnerability to fire: the role of bark harvesting, tree characteristics and abiotic factors. PLoS ONE 7:e39810. [doi | pdf ]

[11] Postfire flowering: Narcissusjgpausas.blogs.uv.es 2 May 2015

[12] Postfire blooming of Asphodelous, jgpausas.blogs.uv.es 5 Apr 2014

[13] Pausas et al. 2012. Fires enhance flammability in Ulex parviflorus. New Phytol 193:18-23. [doi | pdf]

[14] Moreira et al. 2014. Genetic component of flammability variation in a Mediterranean shrub. Mol Ecol 23:1213-1223. [doi | pdf]

[15] He et al. 2012. Fire-adapted traits of Pinus arose in the fiery Cretaceous. New Phytol 194:751-759. [doi | pdf | picture]

[16] Flammable organic compounds: Rosmarinus officinalis, jgpausas.blogs.uv.es 2-Oct-2015

[17] Paula et al. 2016. Lignotubers in Mediterranean basin plants. Plant Ecology [doi | pdf | suppl. | blog]

 

Evolutionary fire ecology in pines

April 1st, 2015 No comments

Fire is an ancient and recurrent disturbance factor in our planet and has been present since the origin of terrestrial plants [1]. However, demonstrating whether fire has acted as an evolutionary force is not an easy task [2]. In this context, the emerging discipline of evolutionary fire ecology aims to understand the role of wildfires in shaping biodiversity. In a recent review paper I summarize what we have learned on evolutionary fire ecology by studying the iconic genus Pinus [3]. I suggest that the study of pines has greatly increased our understanding of the role of fire as an evolutionary pressure on plants.

Macro-evolutionary studies of the genus Pinus provide the oldest current evidence of fire as an evolutionary pressure on plants and date back to ca. 125 Million years ago (Ma). Micro-evolutionary studies show that fire traits are variable within and among populations, and especially among populations subject to different fire regimes. In addition, there is increasing evidence of an inherited genetic basis to variability in fire traits. Added together, pines provide compelling evidence that fire can exert an evolutionary pressure on plants and thus shape our biodiversity. In addition, evolutionary fire ecology is providing insights to improve the management of our pine forests under changing conditions. The lessons learned from pines may guide research on the evolutionary ecology in other taxa.

pinus-serotiny
Figure: Example of trait divergence among populations living under different fire regime. Serotiny (as % of closed cones) in populations living under frequent crown fires (red boxes) and in populations where crown-fires are rare (green boxes) for two pine species, Pinus halepensis (Allepo pine, left) and P. pinaster (maritime pine, right).

References
[1] Pausas, J.G. and Keeley, J.E. 2009. A burning story: The role of fire in the history of life. Bioscience 59: 593-601. [doi | jstor | BioOne | pdf]

[2] Keeley, J.E., Pausas, J.G., Rundel, P.W., Bond, W.J. & Bradstock, R.A. 2011. Fire as an evolutionary pressure shaping plant traits. Trends in Plant Science 16: 406-411. [doi | sciencedirect | trends | pdf]

[3] Pausas, J.G. (2015) Evolutionary fire ecology: lessons learned from pines. Trends in Plant Science 20(5): 318-324. [doi | sciencedirect | pdf]

 

Ecology and evolution in fire-prone ecosystems

February 28th, 2015 2 comments

During the last years I’ve been working in many topics related to fire ecology and plant evolution in ecosystems subject to recurrent fires (mainly mediterranean and savanna ecosystems). Because I believe knowledge should be spread around easily, I make my results available to the public in my web page (see publications list) and in this blog. However, having the cumulative list of paper published each year is not very convenient for people searching for a specific topic. For this reason, I’m rearranging most of my articles by topics as follows:

1. Fire history
2. Fire regime: climate & fuel
3. Fire traits (resprouting, postfire germination, serotiny, bark thickness, flammability, data & methods)
4. Fire & plant strategies (in Mediterranean ecosystems, in pines, in savannas, community assembly)
5. Fire & evolution
6. Some fire-adapted species (Pinus halepensis, Quercus suber, Ulex parviflorus)
7. Fire & vegetation modelling
8. Plant-animal interactions
9. Restoration & conservation

See: fire-ecology-evolution.html

Some papers may be repeated if they clearly fit in more than one topic; some papers, mainly old ones, do not fit well in any of these topics and have not been included (at least at the moment), they still can be found in the section of publications sorted by year. I’m still working on this rearrangement, so some modifications are possible; and any comment is welcome.
I hope this is useful for somebody!

Publications: by year | by topic | books

 

Heritability of serotiny

September 29th, 2014 No comments

Evolution by mean of natural selection requires three conditions: there is variation in the trait, this variation is linked to differences in fitness, and the variation is heritable (Darwin!). In many traits we do not have reliable information for the three processes. For a serotinous species, there is evidence that the level of serotiny is variable, and specially it varies in relation to the fire regime of the population. This is because serotiny increases fitness in crown-fire ecosystems and it is not advantageous in ecosystems that do not suffer frequent fires or in ecosystems with understory fires. We recently studied how serotiny of two pine species (Pinus halepensis and Pinus pinaster) varies within population and between populations with different fire regimes and also provided a meta-analysis of the relation between serotiny and fire from other published studies [1]. We also performed a genetic association study for serotiny using SNPs and showed that 17 loci explained ca. 29% of the serotiny variation found in the field in Pinus pinaster [2], suggesting that serotiny variation have a genetic basis. In our most recent paper we provide the first estimate of heritability for a fire trait; specifically we computed the norrow-sense heritability (h2) of serotiny in Pinus halepensis using the common garden approach [3]. We also evaluated whether fire has left a selection signature on the level of serotiny among populations by comparing the genetic divergence of serotiny with the expected divergence of neutral molecular markers (QST – FST comparison). Serotiny showed a significant heritability (h2 = 0.20). The quantitative genetic differentiation among provenances for serotiny (QST= 0.44) was significantly higher than expected under a neutral process (FST = 0.12), suggesting adaptive differentiation. Overall we showed that serotiny is a heritable trait and that it has been shaped by natural selection driven by fire.

ph-serotiny
Figure: Serotinous cones of Pinus halepensis (Foto: J.G. Pausas)

References:

[1] Hernández-Serrano A., Verdú M., González-Martínez S.C., Pausas J.G. 2013. Fire structures pine serotiny at different scales. American Journal of Botany 100 (12): 2349-2356. [doi | amjbot | pdf | supp. | blog]

[2] Budde, K. B., Heuertz, M., Hernández-Serrano, A., Pausas, J.G., Vendramin, G.G., Verdú, M. & González-Martínez, S.C. 2014. In situ genetic association for serotiny, a fire-related trait, in Mediterranean maritime pine (Pinus pinaster Aiton). New Phytologist 201: 230-241.  [doi | pdf | supp1 | supp2]

[3] Hernández-Serrano, A., Verdú, M., Santos-Del-Blanco, L., Climent, J., González-Martínez, S.C. & Pausas, J.G. 2014. Heritability and quantitative genetic divergence of serotiny, a fire-persistence plant trait. Annals of Botany 114: 571-577. [doi | pdf | suppl.]

 

Serotiny

November 16th, 2013 No comments

Serotiny is the delayed seed release for more than a year by retaining the seeds in a woody structure [1]. This implies an accumulation of a canopy seed bank. Serotiny confer fitness benefits in environments with frequent crown-fires, as the heat opens the cones and seeds are dispersed in the post-fire bed which is rich in resource and the competition and predation are low. It is typical of many Proteaceae and some conifers, like some pine species [1, 2; figure below].

Two recent papers analyse the serotiny of two mediterranean pines Pinus halepensis and Pinus pinaster [3, 4]. P. halepensis show higher proportion of serotinous cones than P. pinaster, but the latter retain the cones for longer [3]. The two species show high variability of serotiny within and between populations, but they show a clear pattern of higher serotiny in populations subject to high frequency of crown-fires than those living in areas where crown-fires are rare or absent. This is true either considering serotiny as the proportion of serotinous cones or as the age of the cones stored. Compared with other pines worldwide, the strength of the fire-serotiny relationship in P. pinaster is intermediate, and in P. halepensis is among the highest known [3]. For P. halepensis (the species with higher % serotiny), populations in high fire recurrence regimes have higher fine-scale spatial aggregation of serotiny than those inhabiting low fire recurrence systems. This phenotypic spatial structure generated by fire could be a consequence of the spatial genetic structure of the population. The second study used genomic tools to search for a genetic association for serotiny [4]. The analysis of 384 SNPs of 199 individuals of P. pinaster (in 3 populations included in the previous study [3])  shows that 17 loci were associated with serotiny and explain all together ca. 29% of the serotiny variation found in the field. All these results adds further evidence to the emerging view that fire shapes intraspecific variability of traits and generates phenotypic divergence between populations [5, 6, 7].

Figure: Serotinous cones of Pinus pinaster (Foto: K.B. Budde)

References:

[1] Keeley J.E., Bond W.J., Bradstock R.A., Pausas J.G. & Rundel P.W. 2012. Fire in Mediterranean Ecosystems: Ecology, Evolution and Management. Cambridge University Press.  [The book]

[2] He T, Pausas JG, Belcher CM, Schwilk DW, Lamont BB. 2012. Fire-adapted traits of Pinus arose in the fiery Cretaceous. New Phytologist 194: 751-759. [doi | wiley | pdf (suppl.)]

[3] Hernández-Serrano A., Verdú M., González-Martínez S.C., Pausas J.G. 2013. Fire structures pine serotiny at different scales. American Journal of Botany 100: 2349-2356 [doi | amjbot | pdf | supp.]

[4] Budde, K. B., Heuertz, M., Hernández-Serrano, A., Pausas, J.G., Vendramin, G.G., Verdú, M. & González-Martínez, S.C. 2014. In situ genetic association for serotiny, a fire-related trait, in Mediterranean maritime pine (Pinus pinaster Aiton). New Phytologist  201: 230-241 [doi | pdf]

[5] Keeley J.E., Pausas J.G., Rundel P.W., Bond W.J., Bradstock R.A. 2011. Fire as an evolutionary pressure shaping plant traits. Trends in Plant Science 16(8): 406-411. [doi] [trends] [pdf]

[6] Pausas, J. G., Schwilk, D. W. 2012. Fire and plant evolution. New Phytologist, 193:301-303. [doi | wiley | pdf]

[7] Pausas J.G., Alessio G., Moreira B. & Corcobado G. 2012. Fires enhance flammability in Ulex parviflorusNew Phytologist 193: 18-23. [doi | wiley | pdf]