The Cactaceae is one of the most conspicuous and ecologically important plant families in the world. Its species may have specialist or generalist pollination systems that show geographic patterns, which are synthesised in the Geographic Dichotomy Hypothesis. Here, we assess this hypothesis in five countries in both tropical and extratropical regions, evaluating the pollinator visitation rate and pollinator identity and abundance. We calculate the Shannon diversity index (H') and evenness (J) and evaluate differences between latitude parameters with a Student t-test. Overall, we found more specialised pollination systems in all tropical sites; the richness, diversity and evenness of pollinators was reduced in comparison to extratropical regions, where the pollination system was generalised. Our results support the geographic dichotomy hypothesis in the cacti of South America, suggesting that environmental factors underlying the latitudinal patterns can help to explain differences in the pollination syndrome between tropical and extratropical regions.

Aims: Facilitation among plant species occurs when the presence of one species, the so-called nurse, alters the environment in a way that enhances the growth, survival or reproduction of a second species. This positive association could be specie-specific and can have direct top-down (canopy) or bottom-up (soil) effects as well as indirect effects like higher tolerance against herbivory. The main objective of our study was to determine the positive interaction between the endemic Chilean orchid Bipinnula fimbriata and the nurse shrub Baccharis macraei in the Mediterranean ecosystem of Chile. Methods: To assess the direct and indirect effects of the nurse, we conducted field and greenhouse experiments, respectively. In the field, we performed manipulative experiments assessing the nurse canopy and soil direct effects on the orchid. We measured microclimatic and edaphic variables within and outside nurses, and assessed survival, growth and photochemical efficiency (Fv/Fm) of the orchids. In the greenhouse, we performed experiments assessing the indirect effect of tolerance to simulated herbivory in orchids under nurse and open spaces conditions. We measured survival, flowering percentage, Fv/Fm, total biomass and jasmonic acid of the orchids. Important Findings: We found more soil moisture and nutrients under the nurses, and higher photosynthetically active radiation, soil and air temperature in open spaces. Survival, growth and Fv/Fm were significantly higher in plants under the nurses, showing the top-down effect more importance than the bottom-up effect. In the greenhouse experiment, we found higher survival, Fv/Fm, flowering and biomass in orchids under the nurse treatment, independently of the imposed herbivory. Jasmonic acid was significantly higher in those individuals with herbivory and open spaces condition. We conclude that B. macraei acts as a nurse improving microclimatic and edaphic conditions that result in an increased survival, growth, physiological status and tolerance against herbivory for B. fimbriata present in the Mediterranean Chilean region.

Los compuestos orgánicos volátiles (COVs) producidos por plantas son productos secundarios de su metabolismo y están involucrados en una gran variedad de funciones ecológicas. Cuando presentes en las flores, los perfiles de los COVs no sólo están asociados con mutualismos, como la polinización, sino también con procesos antagónicos, como la herbivoría o las señales deshonestas. Su presencia, perfiles y concentraciones en las flores están bajo selección mediada por el compromiso entre supervivencia y reproducción de las plantas, es decir por las interacciones antagonistas y mutualistas mediadas por los COVs. En las interacciones mutualistas, los COVs pueden actuar sinérgicamente con señales visuales asegurando la atención de los polinizadores durante períodos más largos y/o a mayores distancias. A pesar del papel fundamental de las fragancias florales en la biología reproductiva, se han realizado pocos estudios que aborden la evolución de este rasgo floral. Esta revisión destaca la importancia de los volátiles florales en las interacciones ecológicas, principalmente en las interacciones planta-insecto. Palabras-clave: COVs florales; herbívoros; polinizadores; señal deshonesta; señal honesta. THE ROLE OF FLORAL VOLATILE ORGANIC COMPOUNDS IN PLANT-INSECT INTERACTIONS. Volatile Organic Compounds (VOCs) produced by plants are secondary products of their metabolism and are related to a wide range of ecological functions. When present in flowers, VOCs profiles are not only associated with mutualisms such as pollination, but also to antagonistic processes such as herbivory or dishonest signaling. Their presence, profiles and concentrations in flowers are under selection mediated by the trade-off between survivorship and reproduction of plants, i.e. antagonist and mutualist interactions mediated by VOCs. In the mutualistic interactions, VOCs can act synergistically with visual signals ensuring the attention of pollinators for longer periods and/or distances. Despite the fundamental role of floral scents on the reproductive biology, few studies addressing the evolution of this floral trait have been reported. This review highlights the importance of floral volatiles on ecological interactions, mainly on plant-insect interactions.

Con el objetivo de asociar genes/QTLs de resistencia a los virus PVY, PVX, a los nematodos (Globodera pallida y G. rostochiensis), al tizón (Phytophthora infestans) y a la verruga (Synchytrium endobóticum) en 20 variedades de papa, incluida la variedad Waych'a como control susceptible, se evaluaron siete marcadores moleculares para SCAR, CAPS y PCR. Los resultados mostraron que el alelo del marcador RySC3 co-localizado con el gen Ryadg de resistencia a PVY, fue observado en todas las variedades evaluadas. El alelo para el marcador CP60 co-localizado con el gen Rx1 para resistencia a PVX, fue observado en todas las variedades excepto en Chota Ñawi. El alelo para el marcador HC co-localizado con el gen/QTL RGp5-vrnHC para resistencia a G. pallida, fue observado en las variedades Aurora, Chota Ñawi, Isabel, Keila, Morita, P'alta Chola, Pujyuni imilla, Robusta, Rosada, Victoria, Violeta, Yungueñita, Jaspe e India. El alelo para el marcador Gro1-4 co-localizado con el gen Gro1-4 para resistencia a G. rostochiensis, fue observado en las variedades Chota Ñawi, Isabel, Keila, Victoria, Violeta, Jaspe e India. El alelo para el marcador GP94 co-localizado con el gen/QTL Rpi-phu 1 para resistencia a P. infestans, fue observado en todas las variedades. Finalmente el alelo para el marcador NL25 co-localizado con el gen Sen1 para resistencia a S. endobioticum, fue también observado en todas las variedades.Aceptado para publicación: Noviembre 30, 2011

We assessed the effect that electromagnetic field (EMF) exerts on honeybees’ pollination efficiency using field and laboratory experiments. First, we measured levels of gene and protein expression in metabolic pathways involved in stress and behavioral responses elicited by EMF. Second, we assessed the effect of EMF on honeybee behavior and seed production by the honeybee-pollinated California poppy and, lastly, by measuring the consequences of pollination failure on plants’ community richness and abundance. EMF exposure exerted strong physiological stress on honeybees as shown by the enhanced expression of heat-shock proteins and genes involved in antioxidant activity and affected the expression levels of behavior-related genes. Moreover, California poppy individuals growing near EMF received fewer honeybee visits and produced fewer seeds than plants growing far from EMF. Last, we found a hump-shaped relationship between EMF and plant species richness and plant abundance. Our study provides conclusive evidence of detrimental impacts of EMF on honeybee’s pollination behavior, leading to negative effects on plant community.

In the Mediterranean portion of Central Chile, where anthropic disturbances are common and severe, precipitations could drastically decrease and temperatures increase due to climate change. In this ecological context, positive interactions between plants could increase in relevance since they can increase growth and survival in stressful conditions. In this area, natural populations also suffer herbivore damage, mainly by cattle and other introduced species. The orchid family is represented in Chile by terrestrial species only that grow in natural and disturbed sites where native shrubs are common. These species have been poorly studied in terms of their ecology, and some species are currently severely threatened. In this study, we tested if native shrubs can facilitate Chilean orchids, reducing abiotic stress and herbivory. We evaluated this positive interaction in three sites with different orchid and shrub species. We found that in all sites, there are more orchid individuals growing inside the canopy of shrubs compared to open areas. Additionally, abiotic conditions were milder and herbivory was reduced inside shrubs in all sites. Our results suggest that there is a positive interaction between native shrubs and native orchids that could result in increased survival in orchid individuals growing inside the canopy of such shrubs. This result could be essential for future conservation and restoration initiatives that should take into account the need for shrubs before re-introduction of individuals in the field, especially for endangered orchid species present in Central Chile.

In stressful environments, a nurse plant can ameliorate harsh biotic and abiotic conditions for another plant species that grows within its canopy. This canopy can act as a barrier for herbivores, reducing damage to the protected plants inside, but it can also reduce access to pollinators possibly resulting in a tradeoff between survival and reproductive output. In a semi‐arid ecosystem, the shrub Porlieria chilensis acts as a nurse, increasing soil moisture, nutrients and reducing temperature inside its canopy compared to open areas. Flourensia thurifera is one of the beneficiary shrubs that can grow inside P. chilensis, where it shows increased survival and performance compared to open areas. However, growing inside P. chilensis’ canopy may reduce pollinator visit. We aim to evaluate the possible tradeoff between survival and reproduction in F. thurifera individuals growing inside and outside the canopy of P. chilensis. This was achieved through a field experiment were we measured survival, pollinator visits and seed output of F. thurifera plants growing inside and outside the canopy of P. chilensis. Flourensia thurifera individuals had a higher survival when growing within the canopy of P. chilensis and had lower pollinator visits and seed output compared to plants growing in open areas. Thus, we found a significant negative correlation between plant survival and seed output considering both conditions (inside or outside nurses), evidencing a tradeoff between these traits. The tradeoff evidenced here could have large impact at the population and community level. On one hand, this tradeoff could mask possible nurse effects in other species, since they could show a similar net fitness in both microhabitat (inside or outside nurses). Finally, we propose a theoretical model to assess the change in the shape of this tradeoff under future climatic conditions where temperature and precipitation are predicted to vary due to climate change.

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