jueves, 31 de enero de 2019

Inferring predator–prey interactions in food webs 
Justin P. F. Pomeranz Ross M. Thompson Timothée Poisot Jon S. Harding

  1. Food webs are a powerful way to represent the diversity, structure, and function of ecological systems. However, the accurate description of food webs requires significant effort in time and resources, limiting their widespread use in ecological studies. Newly published methods allow for the inference of feeding interactions using proxy variables. Here, we compare the accuracy of two recently described methods, as well as describe a composite model of the two, for the inference of feeding interactions using a large, well‐described dataset.
  2. Both niche and neutral processes are involved in determining whether or not two species will form a feeding link in communities. Three different models for determining niche constraints of feeding interactions are compared, and all three models are extended by incorporating neutral processes, based on relative abundances. The three models compared here infer niche processes through (a) phylogenetic relationships, (b) local species trait distributions (e.g., body size), and (c) a composite of phylogeny and local traits.
  3. We show that all three methods perform well at predicting individual species interactions, and that these individual predictions scale up to the network level, resulting in food web structure of inferred networks being similar to their empirical counterparts.
  4. Our results indicate that inferring food web structure using phylogenies can be an efficient way of getting summary webs with minimal data, and offers a conservative test of changes in food web structure, particularly when there is low species turnover between sites. Inferences made using traits require more data, but allows for greater understanding of the mechanisms underlying trophic interactions. A composite model of the two methods provides a framework for investigating the importance of how phylogeny, trait distributions, and relative abundances, affect species interactions, and network structure.
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domingo, 27 de enero de 2019

Plant seeds are primed by herbivore-induced plant volatiles 
Abhinav Kumar Maurya, Leila Pazouki,  Christopher Frost

Mature plants can detect and respond to herbivore-induced plant volatiles (HIPVs) by priming or directly activating defenses against future herbivores. Whether other plant life stages can respond to HIPVs in similar manners is poorly understood. For example, seeds are known to respond to a variety of environment cues that are essential for proper germination timing and survival. Seeds may also be exposed to HIPVs prior to germination, and such exposure may affect the growth, development, and defense profiles when the seeds grow into mature plants. Here, we investigated the effect of seed exposure to common HIPVs on growth, reproduction and defense characteristics in the model plants Arabidopsis thaliana and Medicago truncatula. Of all the HIPVs tested, indole specifically reduced both beet armyworm growth on A. thaliana and pea aphid fecundity on M. truncatula. Induction of defense genes was not affected by seed exposure to indole in either plant species, suggesting that seed priming operates independently of induced resistance. Moreover, neither species showed any negative effect of seed exposure to HIPVs on vegetative and reproductive growth. Rather, M. truncatula plants derived from seeds exposed to z-3-hexanol and z-3-hexenyl acetate grew faster and produced larger leaves compared to controls. Our results indicate that seeds are sensitive to specific HIPVs, which represents a novel ecological mechanism of plant-to-plant communication.

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martes, 22 de enero de 2019

Los no-humanos y los conflictos socioambientales: el caso del Arco Minero del Orinoco

Los no-humanos y los conflictos socioambientales: el caso del Arco Minero del Orinoco


Elsa Gabriela Rodríguez Pérez 



Los botánicos Wandersee y Shussleer (1999)  denominan plant blindness (ceguera vegetal) a la incapacidad de muchos seres humanos de percibir la vegetación o plantas que los rodean (ver Figura 1), interesantemente en lo concerniente a los  conflictos socioambientales existe un fenómeno similar, como veremos más adelante.




Figura 1. ¿Qué ves en la imagen? Un elefante, pues también hay un bello árbol (un Baobab), no observarlo es ceguera vegetal.

Los conflictos socioambientales, sobre todo en el ámbito académico latinoamericano, se analizan desde una corriente particular de la heterodoxa disciplina de la Ecología Política, en la que se da especial énfasis a tópicos como: el extractivismo, las relaciones de poder y los diferentes lenguajes de valoración que pueden existir entre quienes se enfrentan por el uso y apropiación de determinados territorios. Sin embargo, pese a los valiosos aportes de este enfoque particular, en el mismo las entidades no-humanas juegan un rol muy menor, siendo en realidad invisibles. Ahora bien, es justo mencionar que esta nos es más que una, de una multiplicidad de aproximaciones existentes a la Ecología Política. Por ejemplo, la Ecología Política Posconstructivista (Escobar, 2010 o de Tercer Tipo según Gudynas, 2014) incorpora explícitamente en el análisis de los conflictos socioambientales a entidades no-humanas como: objetos, animales, tecnologías (por solo mencionar algunas).

En esta aproximación, la incorporación de los no-humanos no es meramente enunciativa, sino que efectivamente se les otorga estatus de actores a toda clase de entidades no-humanas. La incorporación de los no-humanos en el análisis, responde a un profundo debate de orden ontológico-epistemológico, que cuestiona cierta visión predominante según la cual la sociedad (humanos) siempre se encuentra en una posición jerarquía superior con respecto a la naturaleza (no-humanos).

En este contexto, es particularmente relevante una perspectiva teórica cuyo ámbito de aplicación abarca diferentes disciplinas (sociología, antropología, psicología social y por supuesto, Ecología Política Postconstructivista). Nos referimos al enfoque teórico y metodológico denominado Teoría del Actor-Red, que tiene como principal exponente al sociólogo francés Bruno Latour.

La Teoría del Actor-Red es útil para el estudio de conflictos ambientales, porque nos brinda un marco de referencia que permite incorporar y darle visibilidad a la diversidad de elementos que están involucrados en un conflicto o controversia. Desde las perspectivas convencionales, los actores siempre son humanos. En cambio, con la Teoría del Actor-Red podemos incorporar a entidades heterogéneas y otorgarle capacidad de agencia. En tal sentido, una ley, un animal, un mineral, un bosque o una tecnología también pueden ser actores. La idea es no circunscribir la capacidad agencia a los seres humanos, sino expandirla a todas las entidades que pueden intervenir en la formación de un conflicto o cualquier fenómeno susceptible de estudio (mostramos un ejemplo más adelante). Latour (2008) sostiene como premisa que continuamente establecemos asociaciones con otros entes y estos no tienen que ser necesariamente seres humanos.

Ahora bien, cómo se aplica este planteamiento en el análisis de conflictos socioambientales. En primer lugar, hay que destacar que la Teoría del Actor-Red no solo es una propuesta teórica, sino también metodológica y esta es de gran utilidad para analizar este tipo de contienda, como veremos a continuación utilizando como ejemplo  al Arco Minero del Orinoco.

El Arco Minero del Orinoco

El Arco Minero del Orinoco es un área que según decreto oficial comprende 111.843,70  km2  y que es considerada por el Estado venezolano como una “Zona de Desarrollo Estratégico Nacional” porque en ella se encuentran minerales tales como oro, coltán, cobre e incluso piedras preciosas como el diamante. Con la promulgación del decreto se dio inicio (de forma pública escala nacional) a una controversia compleja que todavía persiste.

Muchos sectores de la sociedad venezolana, e incluso de la comunidad internacional, se han pronunciado en contra del Arco Minero del Orinoco, porque este implica la realización de la minería a gran escala en áreas donde están ubicadas comunidades indígenas, importantes cuencas hidrológicas, parques naturales y reservas de biodiversidad.

En la contienda compleja que supone el Arco Minero del Orinoco, participan toda clases de actores y con ello no sólo nos referimos a las organizaciones sociales ambientalistas, periodistas, académicos, políticos, militares, comunidades indígenas y mineros que participan en este conflicto. También nos referimos a esos otros entes que no son humanos, pero cuyas mediaciones materiales (incluso simbólicas) los hace parte primordial de esta controversia. Una de estas entidades no-humanas, que se puede considerar actor clave dentro de la controversia por el Arco Minero del Orinoco es el oro  (ver Figura 2)


Figura 2. Red de actores (simplificada) involucrados en el conflicto por el Arco Minero. Se aprecia claramente que todos interactúan directamente con el oro y que este a su vez los vincula a todos

En este sentido, si entendemos la agencia como la capacidad de incidir en el otro, es indudable que este mineral ha movilizado a diversos actores. En el caso del Arco Minero del Orinoco, el oro pasa de ser un simple mineral a convertirse en una entidad no-humana que impulsa a otros actores actuar. En el caso del Gobierno venezolano, el oro motiva la generación de decretos, leyes y acuerdos internacionales (entre otros). El oro no sólo es catalogado como “estratégico” por el Gobierno, sino que las asociaciones que se producen con este mineral a su vez generan una red de poder, con componentes nacionales e internacionales (ver Figura 2).

El oro tiene capacidad de agencia y la misma se produce por las distintas asociaciones que se producen entre este con otros actores. La mediación material del oro se expresa porque esta entidad no-humana permite que otros elementos del conflicto se conecten. En la Figura 2 se puede observar como el oro se relaciona con el Gobierno, con países como China, Turquía y Rusia así como con los mineros, indígenas, militares e incluso grupos guerrilleros colombianos como el Ejercito Liberación Nacional (ELN). También se observa que el mismo constituye un nodo fundamental, que conecta actores locales como los mineros, con actores internacionales (países como Rusia y China). El oro se asocia, conecta, otorga poder, genera conflictos. En efecto la asociación con el oro modifica a los actores que con él se conectan: es diferente un ser humano entendido en abstracto, que uno vinculado al oro. Es diferente una comunidad indígena en un territorio no definido, que esta comunidad en un territorio en el cual se extrae oro. Es diferente el papel geopolítico de Venezuela, con o sin su vinculación con el oro.  De esta manera, una entidad no-humana, modifica la connotación y el significado de los actores que a él se conectan. Al reconocerlo como un actor con capacidad de agencia, podemos trazar sus huellas dentro de la controversia por el Arco Minero y percatarnos de las transformaciones que provoca en los otros actores. También es importante reconocer, que análisis similares son posibles y necesarios para otros no-humanos, como por ejemplo: el mercurio, el bosque o el agua.

Entonces, podemos decir que una de la ventajas que supone la Teoría del Actor-Red es que hacer visible toda clase de actores. Permitiéndonos evaluar las asociaciones entre ellos y determinar, analizando de la red en la cual están inmersos, los elementos claves en el surgimiento y desarrollo de una controversia. De esta manera permite enfocarnos más en el cómo, que en el qué.

Finalmente, esta teoría nos introduce a un debate complejo en el cual no sólo se intenta romper con las categorías binarias Sociedad/Naturaleza, sino que además suma otros elementos que desde una perspectiva convencional se dejarían a un lado, como por ejemplo, la capacidad de agencia de los objetos y el papel de sus mediaciones materiales en la interacción. Todo ello supone una oportunidad para darle otra mirada a los conflictos socioambientales, en los cuales siempre la naturaleza y sociedad van de la mano, donde (como se ha mostrado) los no-humanos también son protagonistas.

Aclaratoria
En sentido estricto, el término empleado por Latour para los no-humanos es actantes, aquí por razones de claridad y simplicidad hemos utilizado actores para referimos a ellos.


Imágenes


La imagen mostrada en la Figura 1, es de dominio público:
La red mostrada en la Figura 2, es de elaboración propia.

Referencias 

Escobar, A. (2010). Ecologías políticas postconstructivistas. Recuperado de http://www.unc.edu/~aescobar/text/esp/escobar.2010.EcologiasPoliticasPostconstructivistas.pdf
Gudynas, E. (2014). Ecología Políticas. Ideas preliminares sobre concepciones, tendencias, renovaciones y opciones Latinoamericanas. Uruguay: CLAES.
Latour, B. (2008). Reensamblar lo social: una introducción a la teoría del actor-red. Buenos Aires: Manantial.
Wandersee, J. H. Schussler, E. E. (1999).  Plant blindness. The American Biology Teacher  Vol. 61, No. 2 pp. 82:86.

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lunes, 21 de enero de 2019

International crop trade networks: The impact of shocks and cascades 
Rebekka Burkholz, Frank Schweitzer 

Analyzing available FAO data from 176 countries over 21 years, we observe an increase of complexity in the international trade of maize, rice, soy, and wheat. A larger number of countries play a role as producers or intermediaries, either for trade or food processing. In consequence, we find that the trade networks become more prone to failure cascades caused by exogenous shocks. In our model, countries compensate for demand deficits by imposing export restrictions. To capture these, we construct higher-order trade dependency networks for the different crops and years. These networks reveal hidden dependencies between countries and allow to discuss policy implications.


International trade networks in 2013 for maize (M), rice (R), soy (S), and wheat (W). Each node is colored according to the world map. The color of a link ( i;j ) corresponds to the exporting country i , with a link weight proportional to a logarithmic transformation of the export quantity: log (1 + wij ) . Links with larger weights are plotted on top of smaller ones. Square node shapes indicate that the respective country is a net importer, while circles refer to net exporters. The node size is proportional to a log transformation of their net imports or net exports. The twenty biggest nodes have their ISO-3 country code assigned . Isolated nodes (i.e. without connections) are omitted in a network plot.

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domingo, 20 de enero de 2019


Flowers can hear buzzing bees—and it makes their nectar sweeter 
Michelle Z. Donahue 

"Even on the quietest days, the world is full of sounds: birds chirping, wind rustling through trees, and insects humming about their business. The ears of both predator and prey are attuned to one another’s presence.
... What if it wasn’t just animals that could sense sound—what if plants could, too? The first experiments to test this hypothesis... suggest that in at least one case, plants can hear, and it confers a real evolutionary advantage..."


Flowers respond to pollinator sound within minutes by increasing nectar sugar concentration
Marine Veits et al.

Can plants hear? That is, can they sense airborne sounds and respond to them? Here we show that Oenothera drummondii flowers, exposed to the playback sound of a flying bee or to synthetic sound-signals at similar frequencies, produced sweeter nectar within 3 minutes, potentially increasing the chances of cross pollination. We found that the flowers vibrated mechanically in response to these sounds, suggesting a plausible mechanism where the flower serves as the plant's auditory sensory organ. Both the vibration and the nectar response were frequency-specific: the flowers responded to pollinator sounds, but not to higher frequency sound. Our results document for the first time that plants can rapidly respond to pollinator sounds in an ecologically relevant way. Sensitivity of plants to pollinator sound can affect plant-pollinator interactions in a wide range of ways: Plants could allocate their resources more adequately, focusing on the time of pollinator activity; pollinators would then be better rewarded per time unit; flower shape may be selected for its effect on hearing ability, and not only on signaling; and pollinators may evolve to make sounds that the flowers can hear. Finally, our results suggest that plants may be affected by other sounds as well, including antropogenic ones.

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viernes, 18 de enero de 2019

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Pero si me domesticas, entonces tendremos necesidad el uno del otro. Tú serás para mí único en el mundo, yo seré para ti único en el mundo…

Antoine de Saint-Exupéry / El Principito
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jueves, 17 de enero de 2019

Plant interactions shape pollination networks via nonadditive effects 
Gianalberto Losapio et al.

Plants grow in communities where they interact with other plants and with other living organisms such as pollinators. On the one hand, studies of plant–plant interactions rarely consider how plants interact with other trophic levels such as pollinators. On the other, studies of plant–animal interactions rarely deal with interactions within trophic levels such as plant–plant competition and facilitation. Thus, to what degree plant interactions affect biodiversity and ecological networks across trophic levels is poorly understood. We manipulated plant communities driven by foundation species facilitation and sampled plant–pollinator networks at fine spatial scale in a field experiment in Sierra Nevada, Spain. We found that plant–plant facilitation shaped pollinator diversity and structured pollination networks. Nonadditive effects of plant interactions on pollinator diversity and interaction diversity were synergistic in one foundation species networks while they were additive in another foundation species. Nonadditive effects of plant interactions were due to rewiring of pollination interactions. In addition, plant facilitation had negative effects on the structure of pollination networks likely due to increase in plant competition for pollination. Our results empirically demonstrate how different network types are coupled, revealing pervasive consequences of interaction chains in diverse communities.



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miércoles, 16 de enero de 2019

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To those who do not know mathematics it is difficult to get across a real feeling as to the beauty, the deepest beauty, of nature

 Richard Feynman ‏   
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lunes, 14 de enero de 2019

Phylogenetic inference in section Archerythroxylum informs taxonomy, biogeography, and the domestication of coca (Erythroxylum species)
Dawson M. White Melissa B. Islam Roberta J. Mason‐Gamer

Premise of the Study

This investigation establishes the first DNA‐sequence‐based phylogenetic hypothesis of species relationships in the coca family (Erythroxylaceae) and presents its implications for the intrageneric taxonomy and neotropical biogeography of Erythroxylum. We also identify the closest wild relatives and evolutionary relationships of the cultivated coca taxa.

Methods 

We focused our phylogenomic inference on the largest taxonomic section in the genus Erythroxylum (Archerythroxylum O.E.Schulz) using concatenation and gene tree reconciliation methods from hybridization‐based target capture of 427 genes.

Key Results 

We show that neotropical Erythroxylum are monophyletic within the paleotropical lineages, yet Archerythroxylum and all of the other taxonomic sections from which we sampled multiple species lack monophyly. We mapped phytogeographic states onto the tree and found some concordance between these regions and clades. The wild species E. gracilipes and E. cataractarum are most closely related to the cultivated E. coca and E. novogranatense, but relationships within this “coca” clade remain equivocal.

Conclusions 

Our results point to the difficulty of morphology‐based intrageneric classification in this clade and highlight the importance of integrative taxonomy in future systematic revisions. We can confidently identify E. gracilipes and E. cataractarum as the closest wild relatives of the coca taxa, but understanding the domestication history of this crop will require more thorough phylogeographic analysis.

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domingo, 13 de enero de 2019


HOW BEAUTY IS MAKING SCIENTISTS RETHINK EVOLUTION 
The extravagant splendor of the animal kingdom can’t be explained by natural selection alone — so how did it come to be?

By Ferris Jabr

"male flame bowerbird is a creature of incandescent beauty. The hue of his plumage transitions seamlessly from molten red to sunshine yellow. But that radiance is not enough to attract a mate. When males of most bowerbird species are ready to begin courting, they set about building the structure for which they are named: an assemblage of twigs shaped into a spire, corridor or hut. They decorate their bowers with scores of colorful objects, like flowers, berries, snail shells or, if they are near an urban area, bottle caps and plastic cutlery. Some bowerbirds even arrange the items in their collection from smallest to largest, forming a walkway that makes themselves and their trinkets all the more striking to a female — an optical illusion known as forced perspective that humans did not perfect until the 15th century.
Yet even this remarkable exhibition is not sufficient to satisfy a female flame bowerbird. Should a female show initial interest, the male must react immediately. Staring at the female, his pupils swelling and shrinking like a heartbeat, he begins a dance best described as psychotically sultry. He bobs, flutters, puffs his chest. He crouches low and rises slowly, brandishing one wing in front of his head like a magician’s cape. Suddenly his whole body convulses like a windup alarm clock. If the female approves, she will copulate with him for two or three seconds. They will never meet again.
The bowerbird defies traditional assumptions about animal behavior. Here is a creature that spends hours meticulously curating a cabinet of wonder, grouping his treasures by color and likeness. Here is a creature that single-beakedly builds something far more sophisticated than many celebrated examples of animal toolmaking; the stripped twigs that chimpanzees use to fish termites from their mounds pale in comparison. The bowerbird’s bower, as at least one scientist has argued, is nothing less than art. When you consider every element of his courtship — the costumes, dance and sculpture — it evokes a concept beloved by the German composer Richard Wagner: Gesamtkunstwerk, a total work of art, one that blends many different forms and stimulates all the senses.
This extravagance is also an affront to the rules of natural selection. Adaptations are meant to be useful — that’s the whole point — and the most successful creatures should be the ones best adapted to their particular environments. So what is the evolutionary justification for the bowerbird’s ostentatious display? Not only do the bowerbird’s colorful feathers and elaborate constructions lack obvious value outside courtship, but they also hinder his survival and general well-being, draining precious calories and making him much more noticeable to predators...."

viernes, 11 de enero de 2019

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Trends in ecology: shifts in ecological research themes over the past four decades 
Emily McCallen, Jonathan Knott, Gabriela Nunez‐Mir. Benjamin Taylor, Insu Jo and Songlin Fei

As ecology enters a critical era, more comprehensive studies are needed to improve our understanding of the key themes, major trends, and potential gaps within the discipline. However, as the number of published scientific papers continues to grow, tracking the ever‐expanding body of work becomes increasingly challenging. To identify trends in ecological research, we used recently developed machine learning techniques to perform an automated content analysis on over 84,841 articles published in 33 top‐ranked scientific journals over the past four decades. We detected a clear decline in the relative frequency of classical theoretical research, and increases in data‐intensive research at both micro‐ and macroscales and on anthropogenic themes. Scattered around the periphery of the expanding thematic space, themes such as microbial ecology, genetics, biogeochemistry, and management and policy have all increased in relative frequency. New educational and research frameworks, as well as funding priorities, should incorporate these contemporary themes so that the field of ecology can better address societal challenges.



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jueves, 10 de enero de 2019

Detail of a marginal drawing of a moth from the border of a page from a verse history of Sicily in the time of Frederick II. 
Italy, N. W. (Genoa) in c. 1330 - c. 1340. 
London, The British Library, Ms. Add. 28841, fol. 4v.

miércoles, 9 de enero de 2019

martes, 8 de enero de 2019

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Every Species has come into existence coincident both in space and time with a pre-existing closely allied species

Alfred Russel Wallace
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domingo, 6 de enero de 2019




"When birds of paradise first arrived to Europe, as dried  specimens with legs and wings removed, they were seen in almost mythical  terms — as angelic beings forever airborne, nourished by dew and the  “nectar” of sunlight."

Fallen Angels: Birds of Paradise in Early Modern Europe

https://publicdomainreview.org/2018/04/04/fallen-angels-birds-of-paradise-in-early-modern-europe/


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sábado, 5 de enero de 2019

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Once considered outlandish, the idea that plants help their relatives is taking root  
By Elizabeth Pennisi

For people, and many other animals, family matters. Consider how many jobs go to relatives. Or how an ant will ruthlessly attack intruder ants but rescue injured, closely related nestmates. There are good evolutionary reasons to aid relatives, after all. Now, it seems, family feelings may stir in plants as well.

A Canadian biologist planted the seed of the idea more than a decade ago, but many plant biologists regarded it as heretical—plants lack the nervous systems that enable animals to recognize kin, so how can they know their relatives? But with a series of recent findings, the notion that plants really do care for their most genetically close peers—in a quiet, plant-y way—is taking root. Some species constrain how far their roots spread, others change how many flowers they produce, and a few tilt or shift their leaves to minimize shading of neighboring plants, favoring related individuals.

"We need to recognize that plants not only sense whether it's light or dark or if they've been touched, but also whom they are interacting with," says Susan Dudley, a plant evolutionary ecologist at McMaster University in Hamilton, Canada, whose early plant kin recognition studies sparked the interest of many scientists.

Beyond broadening views of plant behavior, the new work may have a practical side. In September 2018, a team in China reported that rice planted with kin grows better, a finding that suggested family ties can be exploited to improve crop yields. "It seems anytime anyone looks for it, they find a kin effect," says André Kessler, a chemical ecologist at Cornell University.

From termites to people, kin-specific behaviors have evolved over and over in animals, showing there is a strong advantage to helping relatives pass on shared genes. Dudley reasoned that the same evolutionary forces should apply to plants. Not long after researchers proved that plants can distinguish "self" from "nonself" roots, she tested whether they could also pick out and favor kin. She grew American searocket (Cakile edentula), a succulent found on North American beaches, in pots with relatives or with unrelated plants from the same population. With strangers, the searocket greatly expanded its underground root system, but with relatives, it held these competitive urges in check, presumably leaving more room for kin roots get nutrients and water. The claim, published in 2007, shocked colleagues. A few sharply criticized the work, citing flawed statistics and bad study design.

Since then, however, other researchers have confirmed her findings. Recently, working with Moricandia moricandioides, a Spanish herb, Rubén Torices and his colleagues at the University of Lausanne in Switzerland and the Spanish National Research Council demonstrated cooperation in flowering. After growing 770 seedlings in pots either alone or with three or six neighbors of varying relatedness, the team found the plants grown with kin put out more flowers, making them more alluring to pollinators. The floral displays were especially big in plants in the most crowded pots of relatives, Torices and his colleagues reported on 22 May 2018 in Nature Communications.

Torices, now at King Juan Carlos University in Madrid, calls the kin effects "altruistic" because each individual plant gives up some of its ultimate seedmaking potential to expend more energy making flowers. In the end, he suspects, more seeds are fertilized overall in the closely related pots.

Doubts linger. Is a plant identifying genetic kin, or simply recognizing that its neighbor is more or less similar to itself? "I do not think that there has been convincing evidence for kin recognition in plants yet," says Hélène Fréville, a population biologist studying crops at the Montepellier outpost of the French National Institute for Agricultural Research.

Sagebrush bushes (Artemisia tridentata) have provided some strong clues, however. When injured by herbivores, these plants release volatile chemicals that stimulate neighboring sagebrush to make chemicals toxic to their shared enemies. Ecologist Richard Karban at the University of California, Davis, wondered whether kin were preferentially warned. His group had already found that sagebrush plants roughly fall into two "chemotypes," which mainly emit either camphor or another organic compound called thujone when their leaves are damaged. The team showed that the chemotypes are heritable, making them a potential kin recognition signal. In 2014, the researchers reported that when volatiles from a plant of one chemotype were applied to the same type of plant, those plants mounted stronger antiherbivore defenses and had much less insect damage than when the volatiles were applied to a plant of the other chemotype—a hint of a kin effect.

The mustard Arabidopsis thaliana has provided another clue. About 8 years ago, Jorge Casal, a plant biologist at the University of Buenos Aires, noticed that Arabidopsis plants growing next to relatives shift the arrangement of their leaves to reduce shading of their neighbors, but don't do that when the neighbors are unrelated. How they sense the presence of relatives was a mystery, however.

The plants do have light sensors, and in 2015, Casal's team discovered that the strength of reflected light striking nearby leaves signaled relatedness and triggered the rearrangements. Relatives tend to sprout leaves at the same height, bouncing more light onto each other's leaves. By shifting leaves to reduce how much they shade each other, the relatives cumulatively grow more vigorously and produce more seeds, his team found. "There is no other case of kin recognition in plants where the cue, the receptors, and the fitness consequences have been established," Casal says.

Since then, he has shown that when sunflower kin are planted close together, they, too, arrange themselves to stay out of one another's way. The sunflowers incline their shoots alternately toward one side of the row or the other, Casal and his colleagues reported in 2017 in the Proceedings of the National Academy of Sciences. Taking advantage of the effect, they planted 10 to 14 related plants per square meter—an unheard of density for commercial growers—and got up to 47% more oil from plants that were allowed to lean away from each other than plants forced to grow straight up.

Chui-Hua Kong, a chemical ecologist at the China Agricultural University in Beijing, is exploiting a similar effect to boost rice yields. His lab studies rice varieties that give off weed-killing chemicals in their roots. Right now, they don't have high enough yields to replace commonly grown varieties that require herbicides. But in 3-year-long field tests, kin-recognizing versions of these self-protective rice varieties produced a 5% increase in yield when grown with kin, rather than unrelated plants, Kong and colleagues reported in late September 2018 in New Phytologist. To test the approach on a larger scale, he and his colleagues are planting "kin" seedlings of the weed-killing strain together in paddy fields in South China.

Brian Pickles, an ecologist at the University of Reading in the United Kingdom, proposes that kin recognition could even help forests regenerate. By tracing flows of nutrients and chemical signals between trees connected by underground fungi, he showed that the firs preferentially feed their kin and warn them about insect attacks. The finding suggested a family of firs would grow faster than unrelated trees.

To some biologists, the emerging picture of communicating, cooperating plants is still based on thin evidence. Laurent Keller, an evolutionary biologist at the University of Lausanne who has shown that some apparent signs of kin recognition in Arabidopsis can instead stem from innate differences among the plants, calls for more rigor in studies. "People have started to realize that it is important to think carefully about the design of the experiment to rule out other potential explanations," he says.

Keller is keeping an open mind and predicts stronger evidence of plant kin recognition will emerge. Karban is already convinced. "We are learning that plants are capable of so much more sophisticated behavior than we had thought," he says. "It's really cool stuff."

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jueves, 3 de enero de 2019

martes, 1 de enero de 2019