Posts Tagged ‘diversity’

Fire and biodiversity in the Anthropocene

November 20th, 2020 No comments

Conservation of Earth’s biological diversity will be achieved only by recognition of the critical role of fire in shaping ecosystems.


Kelly LT, Giljohann KM, Duane A, Aquilué N, Archibald S, Batllori E, Bennett AF, Buckland ST, Canelles Q, Clarke MF, Fortin M-J, Hermoso V, Herrando S, Keane RE, Lake FK, McCarthy MA, Ordóñez AM, Parr CL, Pausas JG, Penman TD, Regos A, Rumpff L, Santos JL, Smith AL, Syphard AD, Tingley MW, Brotons L. 2020. Fire and biodiversity in the Anthropocene. Science 370 (6519): eabb0355. [doi | science | pdf | suppl.]

Fire as a key driver of Earth’s biodiversity

July 12th, 2019 2 comments

Regions subject to regular fire have exceptionally high levels of species richness and endemism, and fire is likely a major driver of their diversity. In a recent paper [1] we reviewed the mechanisms that enable fire to act as a major ecological and evolutionary force that promotes and maintains biodiversity over different spatiotemporal scales. Specifically, we reviewed the different components of fire regime, the diversity through time (postfire), the intermediate disturbance hypothesis, the pyrodiversity-begets-biodiversity hypothesis, the fire-driven evolution and diversification, and the mutagenic effect of fire.

From an ecological perspective, the vegetation, topography and local weather conditions during a fire generate a landscape with spatial and temporal variation in fire-related patches (pyrodiversity), and these produce the biotic and environmental heterogeneity that drives biodiversity across local, regional and global scales scales [2]. We show that biodiversity should peak at moderately high levels of pyrodiversity. Overall species richness is typically greatest immediately after fire and declines monotonically over time, with postfire successional pathways dictated by animal habitat preferences and varying lifespans among resident plants.

From an evolutionary perspective, fire drives population turnover and diversification by promoting a wide range of adaptive responses to particular fire regimes [3,4]. In addition, fire and its byproducts may have direct mutagenic effects, contributing to the formation of novel genotypes that can lead to trait innovation. As a consequence of all these processes, the number of species in fire-prone lineages is often much higher than that in their non-fire-prone sister lineages.

Figure 1: The six components that define an individual fire event (in red the two core components). The fire regime arises from repeated patterns (means plus variance) over time of the properties of the components for each fire. For more details, see [1].

Figure 2. Relationship between species richness (S) of a reference area (community, landscape, region) and mean fire interval (a fire regime component). For a given fire regime, there is a mosaic of patches defined by different times since the last fire (represented by black circles) about the mean time interval (central circle). For more details, see [1].



[1] He T., Lamont B.B., Pausas J.G. (2019). Fire as s key driver of Earth’s biodiversity. Biological Reviews [doi | pdf]

[2] Pausas J.G. & Ribeiro E. 2017. Fire and plant diversity at the global scale. Global Ecol. Biogeogr. 26: 889–897. [doi | pdf | data & maps (figshare)]

[3] 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 | pdf]  

[4] Pausas J.G. & Keeley J.E., 2014. Evolutionary ecology of resprouting and seeding in fire-prone ecosystems. New Phytologist 204: 55-65. [doi | pdf]  

Fire promotes pollinators

June 14th, 2019 1 comment

In ecosystems with a dens vegetation, wildfires open the canopy and create an environment with more light and less competition. In such postfire conditions there is an increase in flowers, and thus, flower visitors are also likely to increase. In a recent article [1] we performed a meta-analysis to specifically evaluate the effect of fire (prescribed and wildfires) on pollinators from 65 studies in 21 countries across de globe. The overall effect of fire on abundance and richness of pollinators across all studies was positive. The positive effect was especially clear after wildfires and for the abundance and diversity of Hymenoptera (bees, wasps, etc.; the main group of pollinators), while Lepidoptera (butterflies and moths) abundance showed a negative response. Short fire intervals also showed a negative effect on pollinators. In conclusion, pollinators are not only resilient to fire, but they tend to be promoted during the first postfire years. That is, fires by increasing the number of flowers, they also increase the number of flower visitors. It is also likely that this may have a positive cascading effects on other interacting species, like seed dispersers and predators. This is one of the mechanisms by which wildfires increase diversity. Pollinations is also one of the ecosystem services that fires can provide to humans [2].



Figure:  Weighted-mean effect sizes and 95% bias-corrected confidence intervals on abundance (closed circles) and richness (open circles) of pollinator taxa. This is for wildfire only. Sample sizes for each category are shown on the right of each effect. From [1].


[1] Carbone L.M., Tavella J., Pausas J.G., Aguilar R. 2019. A global synthesis of fire effects on pollinators. Global Ecology & Biogeography. [doi | pdf]

[2] Pausas J.G. & Keeley J.E. 2019. Wildfires as an ecosystem service. Frontiers in Ecology and Environment 17: 289-295. [doi | pdf | post]


Fire and diversity

May 26th, 2017 1 comment

In a recent paper [1], we studied the relationship between plant diversity (Fig. 1a) and fire activity (Fig. 1b) for the different ecoregions of the world, and found a strong positive relationship (Fig. 2), even after taking into account productivity and other major environmental variables [1]. This is the first global assessment of the importance of fire as major determinant of species diversity. There are at least two (not mutually exclusive) mechanisms by which fire may drive plant diversity at the scale and grain considered. 1) A selective process; there is both micro and macro evolutionary evidence suggesting that fire regime can drive population divergence and diversification [2-5]. And 2) Fires generate landscape mosaics and thus more habitat types and more niches likely to be filled by different species. In fact, the two processes are linked as landscape mosaics are also appropriate frameworks for population divergences and selective processes in fire-prone ecosystems [6]. That is, our results suggest that fire generates the appropriate conditions for a large variety of plants in many regions worldwide. Or, in other words, a world without fires (if possible at all) would be less diverse.


Fig. 1. Maps of plant diversity (logarithm of the number of species divided by the ecoregion area) and fire activity (estimated by 15 years of remote sensing data for each ecoregions, standardized from 0 to 1) for each terrestrial ecoregion of the world. From [1].

Fig. 2. Plant diversity in each terrestrial ecoregion (number of species divided by area, log scale; Fig. 1a) plotted against an indicator of fire activity (Fig. 1b); the two lines refer to fitted lines for low and high radiative power (an indicator of fire intensity). Form [1].


[1] Pausas J.G. & Ribeiro E. 2017. Fire and plant diversity at the global scale. Global Ecol. & Biogeogr. [doi | pdf | data & maps (figshare)]

[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., Alessio G., Moreira B. & Corcobado G. 2012. Fires enhance flammability in Ulex parviflorus. New Phytol. 193: 18-23. [doi | wiley | pdf]

[4] Hernández-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 | amjbot | pdf | supp.]

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

[6] 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.]  



Diversidad política (2)

December 30th, 2015 No comments

En las recientes Elecciones Generales (20 de Diciembre) hemos conseguido incrementar la diversidad política del próximo gobierno. El Congreso de los Diputados que se está formando será (1) el que tiene más igualdad de género en la historia de la democracia, y (2) el que tiene más diversidad política en escaños (línea azul en la figura). Ambos datos son buenos, demuestran una tendencia positiva en la evolución política de nuestro país, aunque lenta.

DivPoliticaFigura: Valores de diversidad (expresada por el índice de diversidad de Shannon-Weaver) según el número de votos (rojo) o de escaños (azul) en los diferentes partidos políticos, en las diferentes Elecciones Generales al Congreso de los Diputados de España realizadas durante la democracia (elaborado a partir de la base histórica de resultados electorales del Ministerio del Interior).


La población española consta de aproximadamente un 49% de hombres y un 51% de mujeres, y por lo tanto no hay duda de que la paridad de género en el gobierno es importante para que represente bien a la población. En concreto, el 40% de los escaños del Congreso estarán ocupados por mujeres. Por lo tanto, la representación de mujeres no llega a la proporción de la población, pero nos vamos acercando a ella [1].

España es un país muy diverso, con una gran variedad de climas, paisajes, comidas, bailes, lenguas, acentos, etc.; una diversidad generada por su peculiar situación geográfica, su heterogeneidad topográfica y la variedad de acontecimientos ocurridos a lo largo de su historia. Esto ha conferido a la población una elevada diversidad cultural, de ideas y puntos de vista. Sólo un gobierno plural y diverso, capaz de aceptar las diferencias, podrá gestionar correctamente y preservar la diversidad de nuestro país. El bipartidismo difícilmente podía representar la diversidad española. Sabemos que la diversidad es buena; cualquier sistema, sea ecológico, agrícola o social, funciona mejor con elevada diversidad, ya que esta implica más opciones, más posibilidades, más riqueza de ideas, más posibilidad de salir de atolladeros (perturbaciones, epidemias, crisis, etc.). La ciencia y el arte se benefician en gran manera de la diversidad de la población, pero también el pensamiento político, la innovación tecnológica y la economía. Los sistemas con poca diversidad son más simples, más fáciles de entender y de funcionar, pero también más vulnerables, más previsibles, y menos innovadores. Por ello, es importante que nuestras instituciones políticas representen al máximo la diversidad de la población [2]. Los sistemas políticos menos diversos son las dictaduras y las dictablandas; cuanto más nos alejemos de ellas, mejor. La pérdida de diversidad política que se estaba observando durante las últimas décadas (especialmente durante el periodo 1989-2008, ver Figura) era preocupante [2], probablemente fruto de la agresividad de la propaganda electoral, el llamado voto útil, y la injusta ley electoral [3]. El cambio radical en la tendencia (Figura) es un alivio y genera esperanzas.

A pesar del incremento en diversidad, cabe recordar que la diversidad de opciones políticas de los votos que realizan los españoles (línea roja en la Figura) es más elevada que la diversidad política que se refleja en el Congreso (escaños; línea azul en la Figura). El sistema electoral español, que favorece a los grandes partidos y a los partidos de ámbito regional, hace que se pierda más de un 20% de la diversidad política de los ciudadanos (promedio de todas las elecciones), una pérdida nada despreciable.

Los 350 diputados elegidos el pasado 20D ¿están preparados para gestionar la diversidad de este país? ¿son suficientemente maduros (democráticamente) para aceptar las diferencias y gestionar para el bien común? Los anteriores claramente no; estos, lo veremos; esperemos que estén a la altura del momento histórico.


[1] Las mujeres consiguen más representación que nunca, pero no la paridad., 21/12/2015

[2] Diversidad política: Pérdida de diversidad política en España, 11/3/2008

[3] Con un sistema proporcional puro, la izquierda superaría a la derecha. Público, 21/12/2015

Actualización (14/01/2016): Ya se ha constituido el Congreso de los Diputados, y a simple vista se puede observar que también ha incrementado la diversidad de maneras de vestir de los diputados, que probablemente refleja un incremento en la diversidad de maneras de pensar. Pero una viñeta vale más que mil palabras, aquí la de Miguel Gallardo.


Fire shapes savanna-forest mosaics in the Brazilian cerrado

May 14th, 2013 No comments

Cerrado is the name of a tropical fire-prone mosaic of savanna and forest in Brazil. In a recent paper [1], we showed that in cerrado landscapes, despite the existence of a great variety of community structure (from open savannas to closed forests; Figure below), there are two well-defined stable states of community function, each associated with contrasting levels of community closure (open and closed environments) and maintained by different fire regimes. Soil properties, phylogenetic and non-phylogenetic beta-diversities, and most of the plant functional traits presented a threshold pattern along the community closure gradient with coinciding breakpoints, providing strong evidence of a functional threshold along the forest-savanna gradient. Open environments consisted of communities growing on poor soil and dominated by short species with early investments in thick barks, low wood density and with thick and tough leaves (high toughness and low specific area). In contrast, closed communities grow in more fertile soils and include plants having the opposite functional attributes. Moreover, we found contrasting fire regimes on the two sides of the threshold, with open formations showing shorter fire intervals than closed formations and a switch from communities dominated by fire-resistant plants to communities dominated by shade tolerant species that compensate for their lack of fire resistance by efficiently closing the canopy (i.e., reducing flammability). Overall, these results are consistent with the theoretical model of fire-plant feedbacks as main drivers of the coexistence of two stable states, savanna and forest. In this context, we provide the first field-based evidence for a community-level threshold separating two vegetation states with distinct functional and phylogenetic characteristics and associated with different fire regimes.

Top: A woodland cerrado (cerrado sensu stricto) six months after a fire, with several top-killed trees and a developed layer of resprouting vegetation; and one of the sampled closed forests.
Middle: A dense woodland cerrado (cerrado denso); one example of a typical thick-barked species found in open communities (Anadenanthera peregrina (Benth.) Reis, Fabaceae); a transitional zone between dense savannas and forests.
Bottom: A typical open savanna at the early rainy season, with tall flammable grasses and small trees and shrubs.
Photo credits: V. Dantas, G. Sartori, V. Cadry, J.G. Pausas, F. Noronha, A. Favari. See [1].


[1] Dantas V., Batalha, MA & Pausas JG. 2013. Fire drives functional thresholds on the savanna-forest transition Ecology 94: 2454-2463. [doi | pdf]


Mediterranean diversification and plant syndromes

January 21st, 2013 No comments

Woody plants of the Mediterranean Basin can be classified in two contrasted morpho-functional syndromes [1]: a) plants with sclerophyllous, evergreen leaves and small, unisexual greenish or brownish flowers with a reduced perianth, and large seeds dispersed by vertebrates; and b) plants with alternative character states (non-sclerophyllous deciduous, semi-deciduous or summer deciduous species with large and conspicuous flowers pollinated by insects, and small seeds). The sclerophyllous syndrorme (a) occurs in clades whose characteristics pre-date the appearance of the mediterranean climate while the non-sclerophyllous syndrome (b) arose in clades that have evolved after the emergence of this distinctive climate (Tertiary – Quaternary transition).

A recent phylogenetic study [2] show that during the time with prevalent mediterranean climate, lineages with the non-sclefophyllous syndrome showed a higher speciation rate than the sclerophyllous lineages, suggesting that a syndrome-driven local diversification has occurred in shrublands under mediterranean conditions. The processes behind this result might be divers, but fire might had an important role. The rise of mediterranean climate increased fire activity [3] and traits defining these two syndromes are related to post-fire regeneration traits and to the age to maturity [4,5]. The non-sclerophyllous syndrome is associated with species considered post-fire seeders (i.e., killed by fire in which populations regenerate from a persistent seed bank; fire-stimulated germination [6,7]) and to species with early maturation. In fire-prone ecosystems, these characteristics reduce the generation time and the overlap between generations and thus they provide more opportunities for diversification.

Overall, the results provide an example of how the integration of the environmental filter in a dated phylogeny may recreate the local history of lineages and help to explain assembly processes in mediterranean ecosystems.

Figure: Frequency distribution of differences in local speciation rate (λ) between non-sclerophyllous (n) and sclerophyllous (s) syndromes in the Valencia woody flora for 3 different post cut temporal slices (cutoff of 10, 6, and 3.6 My) related to the increasing aridity associated with the rise of mediterranean climate. For all alternative phylogenies (i.e., accounting for the undertainity in node age), speciation rate of the non-sclerophyllous syndrome is greater than for the sclerophyllous one. See Verdú & Pausas (2013) for details [2].

[1] Herrera, CM. 1992. Historical effects and sorting processes as explanations for contemporary ecological patterns: character syndromes in Mediterranean woody plants. Am. Nat. 140:421-446.

[2] Verdú M. & Pausas J.G. 2013. Syndrome-driven diversification in a Mediterranean ecosystem. Evolution. [doi | pdf]

[3] Keeley JE., Bond WJ., Bradstock RA., Pausas JG. & Rundel PW. 2012. Fire in Mediterranean Ecosystems: Ecology, Evolution and Management. Cambridge University Press [the book]

[4] Pausas, J.G., Bradstock, R.A., Keith, D.A., Keeley, J.E. & GCTE Fire Network. 2004. Plant functional traits in relation to fire in crown-fire ecosystems. Ecology 85: 1085-1100. [pdf | jstor]

[5] Pausas J.G. & Verdú M. 2005. Plant persistence traits in fire-prone ecosystems of the Mediterranean Basin: A phylogenetic approach. Oikos 109: 196-202. [doi| pdf]

[6] Moreira B., Tormo J., Estrelles E., Pausas J.G. 2010. Disentangling the role of heat and smoke as germination cues in Mediterranean Basin flora. Annals of Botany 105: 627-635. [doi| pdf]

[7] Moreira B. & Pausas J.G. 2012. Tanned or burned: The role of fire in shaping physical seed dormancy. PLoS ONE 7(12): e51523.  [doi | plos | pdf]


Linguistic diversity hotspots

August 2nd, 2012 No comments

Languages can be study using similar tools as we use for biological organism, because languages, like species, have their geographic distribution, they have variability, they evolve with time, they show divergence and extinction processes. In fact there are phylogenetic trees and networks of languages [1] similar to those we build for understanding species evolution. In addition, a recent paper show that the hotspots of species diversity also co-occur with hotspots of language diversity [2], in such a way that highly biodiverse areas accounting for 24% of Earth’s land surface contain ca. 70% of the world’s languages. However, the reasons of this link is not yet well understood. Are the factors that generate linguistic diversity the same to those that generate biodiversity? Is the linguistic diversity a consequence of the biodiveristy? Nearly 60 percent of the languages in high biodiversity regions, like Amazonia and the lowland forests of West Africa, are spoken by fewer than 10,000 people; more than 1,200 of those languages are spoken by fewer than 1,000 people. So cultural diversity, as biological diversity, is threatened. It is worth mentioning the recent online collaborative effort trying to preserve samples of endangared languages [3].

Geographic distribution of indigenous languages (from [2])

[1] Diversity of languages,, November 7th, 2010.

[2] Gorenflo L.J., Romaine S., Mittermeier R.A. & Walker-Painemilla K. (2012). Co-occurrence of linguistic and biological diversity in biodiversity hotspots and high biodiversity wilderness areas. PNAS [doi]

[3] Endangered Languages, A project by the Alliance for Linguistic Diversity,


Diversity of languages

November 7th, 2010 No comments

Linguistic diversity has many commonalities with species diversity, and the two disciplines are sharing methodologies. Few years ago, Gray and Atkinson (2003) showed a phylogenetic tree of Ind-European languages [1, see tree], a tree similar to those used in evolutionary biology. This is because languages contain a lot of historic information, like species. In this line, an interesting and recently compilation of papers show the state-of-the-art of evolutionary approaches to study cultural and linguistic diversity [2]. For instance, we can see a phylogeneitc network of the Indo-European languages (see below, by Gray et al.) or the extinction trends of a language (e.g., the case of Gaelic in Scotland, by Kandle et al. [see figure]).

Jarret Diamond recently highlighted the benefits of learning several languages [3]. Apart for the obvious social benefits, there are also health benefits of multilingualism like protection against Alzheimer’s dementia in old people [4]. What it is unclear is whether the health benefits increase with the phylogenetic distance of the languages learned, or not. … So there is still a lot of room for including evolutionary approaches in social and medical sciences.


[1] Gray RD and Atkinson QD 2003. Language-tree divergence times support the Anatolian theory of Indo-European origin. Nature 426: 435-439 (27 Nov. 2003).

[2] Steele J, Jordan P and Cochrane E (eds). 2010. Cultural and linguistic diversity: evolutionary approaches. Phil. Trans. R. Soc. B vol. 365 (no. 1559) [table of contents]

[3] Diamond J. 2010. The Benefits of Multilingualism. Science 330: 332-333 (15 Oct. 2010).

[4] Bialystok E, Craik FI, Freedman M. 2007. Bilingualism as a protection against the onset of symptoms of dementia. Neuropsychologia 45: 459-64

NeighborNet analyses of the Indo-European lexical data. Scale bar, 0.1. (Grey et al. 2010, Phil. Trans. R. Soc. B 365: 3923-3933).

Fire increases species relatedness in plant communities

March 2nd, 2010 No comments

Mediterranean communities living under high fire recurrence are composed by plant species that are more closely related than what would be expected from the regional species pool (i.e., phylogenetic clustering; Verdú & Pausas 2007). This is because high fire recurrence favors seeder species, and the traits that confer the seeder character (e.g., heat and smoke stimulated germination, Moreira et al. 2010) are evolutionary conserved, that is, closely related species tend to be similar (Pausas & Verdú 2008). In fact, the abundance of seeders species is negatively related to phylogenetic diversity (Coca & Pausas 2009; see Figure 2 below).

The Figure 1 below shows the Net Relatedness Index (NRI, i.e, standardized form of the community mean phylogenetic distance) of woody species coexisting in for communities in contrasted crown-fire regimes (LowFire vs HighFire) at different spatial scales (regional and local). Note that high net relatedness = low mean phylogenetic distance. At regional scale, “LowFire” corresponds to mountain communities living in zones that rarely burnt, and “HighFire” are warm and dry coastal communities subject to a high frequency of crown fires. At local scale (under the same climate), “LowFire” corresponds to communities growing in fertile soils while “HighFire” are communities growing on poor soils where flammability is higher. When comparing from community null models, HighFire communities show higher NRI than expected by chance (phylogenetic clustering), which indicates the importance of habitat filtering in shaping fire-prone communities (Verdú & Pausas 2007, Ojeda et al. 2010).


Fig. 1. Elaborated from Verdú & Pausas (2007) and Ojeda et al. (2010).

PD-seeders_Coca-Pausas Fig. 2. From Coca & Pausas (2009).


  • Coca M. & Pausas J.G. 2009. Regeneration traits are structuring phylogenetic diversity in cork oak (Quercus suber) woodlands. J. Veget. Sci. 20: 1009-1015. [doi | pdf | post]
  • Moreira B., Tormo J., Estrelles E., Pausas J.G. 2010. Disentangling the role of heat and smoke as germination cues in Mediterranean Basin flora. Ann. Bot. 105:627-635 [doi | pdf | post]
  • Ojeda, F., Pausas, J.G., Verdú, M. 2010. Soil shapes community structure through fire. Oecologia 163:729-735. [doi | pdf | post]
  • Pausas J.G. & Verdú M. 2008. Fire reduces morphospace occupation in plant communities. Ecology 89: 2181-2186. [doi | pdf]
  • Verdú M. & Pausas J.G. 2007. Fire drives phylogenetic clustering in Mediterranean Basin woody plant communities J. Ecol. 95: 1316-323. [doi | pdf]

Wine supporting biodiversity

January 5th, 2010 No comments

Good news: Sainsbury’s to pop new corks for wildlife. All of Sainsbury’s own-brand wines will be sealed with corks certified by the Forest Stewardship Council by the end of 2010 [see The Guardian, 31/Dec/2009].  Sainsbury is the third largest chain of supermarkets in the United Kingdom. We hope other supermarkets and wine makers will follow this initiative.

Remeber that IUCN proposed ten things we all can do to save biodiversity [see], and one was to only drink wines with natural cork stoppers!

Cork oak (Quercus suber) is a WWF priority species, because it is one of the most ecologically, economically and/or culturally important species.

For more information on cork oak woodlands see the book Cork Oak Woodlands on the Edge, and the WWF Cork Oak Programme.


corcho_WWF treebark1sm

New paper: Regeneration traits and phylodiversity

October 29th, 2009 No comments

Coca M. & Pausas J.G. 2009. Regeneration traits are structuring phylogenetic diversity in cork oak (Quercus suber) woodlands. J. Veget. Sci. 20: 1009-1015  [Wiley] [doi] [pdf]

  • Question: What factors determine the deviations from the relationship between species richness (which considers species as independent entities) and phylogenetic diversity (PD) (which considers species relatedness)? What are the implications for community composition and phylogenetic structure?
  • Location: Los Alcornocales Natural Park, in southern Iberian Peninsula (Spain).
  • Methods: We recorded all woody species and geographical features on 94 (20 m × 20 m) plots of cork oak woodlands. Disturbance information was obtained from the Park records; precipitation was estimated from local maps. PD was computed as the minimum total length of all the phylogenetic branches spanning the set of species on each site. Then, PD was regressed against species richness to test to what extent the unexplained variance in this relationship could be accounted for by environmental variables and disturbances, and against the representation of species with different regeneration strategies.
  • Results: Species richness and PD are strongly related; however, the remaining variability can be explained by: (1) precipitation and disturbance, and (2) the proportion of seeder species. Thus, the PD both of areas with low precipitation and high disturbance, and of areas with a high representation of seeder species, is lower than what would be expected from the species richness.
  • Conclusions: Regeneration traits are important in structuring plant community composition; specifically, they contribute to shaping biodiversity in Mediterranean ecosystems. Species richness tends to overestimate biodiversity in highly disturbed systems.
Fig3_resid-propP The relationship between the residuals from the phylodiversity-species richness regression, and the proportion of post-disturbance seeding species (P+; r= -0.560, p< 0.0001). Negative residuals indicate lower phylogenetic diversity than expected from species richness values, that is, a tendency for phylogenetic clustering.

Amazonia: The empty forest

October 27th, 2009 No comments

We all now about the over-exploitation and over-hunting in many ecosystems, including the Amazonian forests. Recently, travelling in Brazil I found some figures on the magnitude of the hunting in the Amazon, they are unbelievable:

Number of animals legally exported from one single port (Iquitos, a river port in the Peruvian Amazon) during 5 years (1962-1967):

183,664 – Monkeys
149,256 – Caiman species (Melanosuchus and Caiman)
67,575 – Capybaras (Hydrochaeris)
47,851 – Otter (Lutra)
2,529 – Giant otter (Pteronura)
61,499 – Ocelots (Leopardus pardalis = Felis pardalis)
9,565 – Margay (Leopardus wiedii = Felis wiedii)
5,345 – Jaguar (Panthera onca)
690,210 – Collared Peccary (Pecari tajacu = Tayassu tajacu)
239,472 – White-lipped Peccary, Tayassu pecari,
239,470 – Deer (Mazama)

Total > 1.6 millions of animals!

But, you need to add those that were hunted for local consumption (estimated to be as many as to those hunted for legally exporting, above), and those hunted illegally (estimated to be much more that those hunted legally). And this is only for one single port, for a only 5 years, and only for large mammals and caimans … (birds, turtles, lizards, etc… are also hunted). This strong defaunation of vertebrates has implication not only on animal biodiversity but it has also cascading effects on ecosystems (e.g., reducing predation, herbivory, dispersal of plants, etc.). [more info: R. Dirzo]

The Amazon is now a great place for any biologist, how would it be if it was not an empty forest!

MISR image of the Central Amazon showing the city of Manaus, the meeting-of-the-waters where the Rio Negro and Rio Solimoes merge.

Fenandéz, F. 2009. O poema imperfeito, 2on ed., UFPR editora.
Redford, K.H. 1992. The empty forest. BioScience, 42(6), 412–422.

Pérdida de diversidad política en España

March 11th, 2008 No comments

No es necesario analizar los datos genéticos para saber que no hay dos personas iguales, y que la población es extremadamente diversa. De hecho, la población de países como España presenta una diversidad elevada, no sólo por el legado histórico (reflejada, por ejemplo, en la diversidad de lenguas y acentos de éstas), sino también por los procesos actuales, de manera que cada vez se aceptan más opciones ideológicas, sociales, sexuales, religiosas, etc. y cada vez hay más gente que ha nacido o a tenido fuertes influencias de otros países y culturas. Se puede decir que somos un país diverso, somos ricos.

Esta diversidad es buena, y debemos estar orgullosos de ello. Cualquier sistema, sea ecológico, agrícola o social, funciona mejor con elevada diversidad, ya que esta implica más opciones, más posibilidades, más riqueza de ideas, más posibilidad de salir de atolladeros (perturbaciones, epidemias, crisis, etc.). La ciencia y el arte se benefician en gran manera de la diversidad de la población, pero también el pensamiento político, la innovación tecnológica y la economía. Los sistemas con poca diversidad son más simples, más fáciles de entender, pero también más vulnerables, más previsibles, y menos innovadores. La importancia de la diversidad ha llevado a un resurgimiento de la conservación de la diversidad a muchos niveles, tales como el nivel ecológico (conservación de las especies), el agrícola y ganadero (conservación de variedades), el social (protección de las lenguas, las culturas), etc.

En un país democrático y con una democracia representativa, se supone que la población elige a un gobierno que le represente. Para ello, se generan diversos partidos políticos que intentan recoger al máximo las ideologías políticas de la población. En las elecciones al gobierno, cada persona vota a un partido según su propia ideología, de manera que el gobierno debería ser un reflejo de la diversidad de ideologías de la población votante. Sin embargo, si observamos los valores de diversidad política que se desprenden de las elecciones generales que ha habido durante la democracia española, vemos que hay signos claros de pérdida de diversidad:

diversidad-politica Valores de diversidad (expresado por el índice de diversidad de Shannon-Weaver) según los votos (rojo) o los escaños obtenidos al congreso (azul) en las diferentes elecciones generales de España. Elaborado a partir de la base histórica de resultados electorales del Ministerio del Interior.

En primer lugar, se observa que la diversidad de opciones políticas de los votos que realizan los españoles es mucho más elevada que la diversidad política que se refleja en el Congreso (escaños). El sistema electoral español hace que se pierda aproximadamente un 25% de la diversidad política de los ciudadanos, una pérdida nada despreciable. Esto se debe a que la legislación electoral favorece a los grandes partidos en detrimento de los partidos pequeños. En segundo lugar, se observa una clara disminución de diversidad en el tiempo, hecho que ha quedado muy patente en las últimas elecciones del 9 de marzo de 2008. La razón de esta pérdida parece estar ligada a un concepto perverso, el concepto de “voto útil”. La idea del “voto útil” hace que la población no vote exactamente según sus ideales, sino a los grandes partidos, y por lo tanto, la configuración del parlamento resultante de las elecciones no representa la diversidad de la población. Además, la llamada “disciplina de partido” reduce la posible diversidad que pueda haber dentro de los partidos. La actual ley electoral también distorsiona la diversidad espacial, otorgando diferente peso a los votos de cada persona dependiento de la densidad de población del lugar donde vive (hecho que cuestiona esa idea democrática de que todas las personas tienen las mismas posibilidades de ser representadas en el parlamento). Todo esto conlleva a que la población, con el tiempo, se sienta frustrada con el gobierno, ya que los comportamientos de este no son los que ellos desearían. Ello incita a la abstención, y pone de manifiesto la inutilidad del “voto útil”. Gran parte de la frustración de la izquierda de nuestro país viene dada por el concepto del “voto útil” y la pérdida de diversidad que todo ello comporta. De hecho, la tendencia a la pérdida de diversidad en la representación política pone en tela de juicio a las democracias representativas. El caso extremo de gobiernos con baja diversidad son las dictaduras.

Claramente podemos afirmar que el parlamento salido de las últimas elecciones españolas es un parlamento poco diverso, pobre, el más pobre de la democracia, al contrario que la población española, que es rica, quizá la más rica de la democracia. Esta pérdida de diversidad de nuestro sistema político requiere una profunda y urgente reflexión. Los representantes políticos deberían entender que un país moderno, dinámico e innovador requiere estar liderado por un gobierno que refleje la diversidad de la población, y por lo tanto deberían introducir los mecanismos necesarios para conseguirlo. Todos nos beneficiaríamos. Desgraciadamente, los partidos políticos actualmente están inmersos en un sistema competitivo y sólo piensan en sacar el máximo de votos posibles (incluso a veces incitan al “voto útil”), en lugar de pensar en configurar un parlamento que refleje más claramente la diversidad de ideas de la población.

Juli G. Pausas, Godella, 11 de marzo de 2008