Age matters: variations in parasitoid diversity along a successional gradient in a dry semi-deciduous tropical forest.

Parasitoids are an important group of insects because their species number is among the highest. Multiple studies have addressed the relationships between forest successional age and insect diversity by focusing on herbivorous organisms, but changes in diversity of parasitoids are still poorly known. This work analyses the diversity of parasitoids in tropical forests representing three successional stages. A total of 30 traps were placed, ten in each forest successional stages. We estimated true diversity of Ichneumonidae species and guilds and explored the relationship between their diversity and the abundance of plant species using an Indicator Species Analysis; the relationship between parasitoid species and plant richness and abundance was tested using a Redundancy Analysis. A total of 1522 individuals and 168 morpho-species were captured in four months. Species richness showed no differences; however, parasitoid abundance was higher in young forest, while intermediate forest had the highest true diversity values (1D) with 71.6 effective species. According to insect guilds, richness, abundance, and diversity were similar in the three vegetation successional stages. This finding may be explained based on the intermediate disturbance hypothesis, which postulates that moderate disturbance levels favor the highest diversity. In conclusion, successional age matters, i.e., diversity is the highest in intermediate stages, while the old forests harbors guilds unique to that successional stage, such as parasitoids of melitophagous larvae of bees. Other successional stages were characterized by a single species of parasitoid, belonging to the genera Eiphosoma and Anomalon, which may indicate altered and preserved forests, respectively.

Survival Rate of the Neotropical Stingless Bees Nannotrigona perilampoides and Frieseomelitta nigra after Exposure to Five Selected Insecticides, under Controlled Conditions.

Insecticides used in agricultural pest management pose survival risks to the stingless bees that forage on crops in tropical and subtropical regions. In the present study, we evaluated, under laboratory conditions, the acute oral toxicity of five selected insecticides (dinotefuran, imidacloprid, flupyradifurone, spirotetramat, and cyantraniliprole) to two species of neotropical stingless bees: Nannotrigona perilampoides and Frieseomelitta nigra. At field recommended doses, dinotefuran, imidacloprid, and flupyradifurone caused the highest mortality in both bee species. These insecticides also caused the largest decrease in the survival rate when exposed to a 10-fold dilution of the field recommended doses. Notably, dinotefuran exerted a high effect even at 100-fold dilution (100% mortality). In contrast, cyantraniliprole had a low effect and spirotetramat was virtually nontoxic. These results suggest that some insecticides used to control sap-sucking insects may have a significant negative impact on the communities of stingless bees.

Determining relevant traits for selecting landrace accessions of Phaseolus lunatus L. for insect resistance.

Plant-insect interactions are a determining factor for sustainable crop production. Although plants can resist or tolerate herbivorous insects to varying degrees, even with the use of pesticides, insects can reduce plant net productivity by as much as 20%, so sustainable strategies for pest control with less dependence on chemicals are needed. Selecting plants with optimal resistance and photosynthetic traits can help minimize damage and maintain productivity. Here, 27 landrace accessions of lima beans, Phaseolus lunatus L., from the Yucatan Peninsula were evaluated in the field for morphological resistance traits, photosynthetic characteristics, insect damage and seed yield. Variation was found in physical leaf traits (number, area, and dry mass of leaves; trichome density, specific leaf thickness and hardness) and in physiological traits (photosynthetic rate, stomatal conductance, intercellular carbon, water-use efficiency, and transpiration). Five accessions (JMC1325, JMC1288, JMC1339, JMC1208 and JMC1264) had the lowest index for cumulative damage with the highest seed yield, although RDA analysis uncovered two accessions (JMC1339, JMC1288) with strong positive association of seed yield and the cumulative damage index with leaf production, specific leaf area (SLA) and total leaf area. Leaf traits, including SLA and total leaf area are important drivers for optimizing seed yield. This study identified 12 important morphological and physiological leaf traits for selecting landrace accessions of P. lunatus for high yields (regardless of damage level) to achieve sustainable, environmentally safe crop production.

INFLUENCIA DE LA HERBIVORÍA Y LA APERTURA DE CLAROS SOBRE EL CRECIMIENTO TOTAL DE Brosimum alicastrum (Moraceae) / Influence of herbivory and gap-openness on whole-plant growth of Brosimum alicastrum (Moraceae)

RESUMEN El crecimiento compensatorio y las defensas vegetales son respuestas para lidiar con la herbivoría y la luz. El estudio de la influencia de los componentes morfo-fisiológicos, de la asignación de biomasa y de la defensa vegetal podría arrojar información que ayude a entender estas respuestas. Se evaluaron los efectos de la herbivoría y la apertura de claros sobre el crecimiento, los componentes morfo-fisiológicos, la asignación de biomasa y las defensas químicas y físicas en plántulas de Brosimum alicastrum en una selva mediana subcaducifolia. Se utilizó un diseño anidado con sitios de sotobosque y claros (n = 3 en cada uno) y dentro de ellos plántulas sometidas a tres tratamientos de herbivoría: control (n = 10), simulada (n = 10) y natural (n = 10). Se registró a lo largo de seis meses la influencia de la herbivoría sobre el crecimiento (biomasa, área foliar, altura, diámetro y producción de hojas), la producción de fenoles y la dureza foliar. Se halló un crecimiento compensatorio (todas las variables de crecimiento) con la herbivoría natural, subcompensatorio (biomasa, altura y diámetro) con la simulada, y sobrecompensatorio (producción de hojas) con la herbivoría natural sólo en claros. Los componentes morfológicos como el cociente del área foliar (LAR) y el área foliar específica (SLA) fueron mayores bajo claros y el fisiológico, como la tasa de asimilación neta (NAR), en sotobosque. La proporción de biomasa en sotobosque fue mayor hacia hojas y tallos y en claros más alta hacia raíces. La herbivoría fue mayor en claros y los fenoles foliares en sotobosque. No se encontró una relación (compromiso) entre las defensas y el crecimiento, sólo una tendencia negativa con los fenoles bajo condiciones limitantes de recursos, como ocurre en el sotobosque.

ABSTRACT Compensatory plant growth and plant defense are responses to deal with herbivory and light availability. The research focused on compensatory growth responses explained through the influence of morphological and physiological components of plant growth, allocation mass, and plant defense could clarify such process. We studied the effects of herbivory and gap-openness on compensatory growth responses, morphological and physiological components, allocation mass, and chemical defenses in seedlings of Brosimum alicastrum in a subhumid tropical forest. We used a nested design with understory and gap-openness site (n = 3 each) within each replicated site seedling belong to three herbivory treatments (n = 10 each): control, simulated, and natural; and along six months we studied the influence of leaf herbivory on plant growth (mass, leaf area, height, diameter, and leaf production) and production of phenols and leaf toughness. We recorded compensatory growth responses (all plant growth variables) with natural herbivory, subcompensatory (mass, height, and diameter) with simulated and, overcompensatory (leaf production) with natural herbivory although only under gap-openness. We found a higher leaf area ratio (LAR) and specific leaf area (SLA) (both morphological components) under gap-openness and high values of net assimilation rate (NAR) on understory. The mass proportion was highest in leaves and stems on the understory and higher in roots under gap-openness. Leafherbivory was highest under gap-openness while the phenols of the leaves on understory. We did not find a relationship (trade-off) between defense with plant growth, but it was possible to underline a negative pattern of the leaf phenols under limiting resources environment such as understory.

Frequency of the L1014F Mutation in the Sodium Channel Gene, in Culex quinquefasciatus (Diptera: Culicidae) Populations From Rural and Urban Areas of Yucatan State, Mexico.

Culex quinquefasciatus Say (Diptera: Culicidae) is a mosquito species that has attracted a lot of attention from a medical and veterinary point of view; however, little is known about the frequency of L1014F mutations that have been found in the sodium channel gene, with this being a target for DDT and pyrethroid insecticides. The distribution and frequency of the L1014F mutation in Cx. quinquefasciatus populations was determined in rural and urban areas of Yucatan, Mexico from January 2015 to March 2016. Nine hundred fifty adult females out of 17,727 immature states were collected and analyzed in all sites sampled (n = 10). Susceptible homozygotes were identified (L1014/L1014) in 12% (114/950), heterozygous individuals (F1014/L1014) in 34% (323/950), and mutated homozygotes (F1014/F1014) in 54% (513/950) during the dry and rainy seasons. In this work, study areas with a high frequency of L1014F mutation were identified. These findings may help guarantee a more effective and efficient use of the resources available for the control of this vector.

Population fluctuation of Schistocerca piceifrons piceifrons (Orthoptera: Acrididae) in the Yucatán Península and its relation with the environmental conditions / Fluctuación poblacional de Schistocerca piceifrons piceifrons (Orthoptera: Acrididae) en la Península de Yucatán y su relación con las condiciones climáticas

Abstract The Central American Locust Schistocerca piceifrons piceifrons is one of the most damaging plant pest in Mexico and Central America. The present work was carried out to evaluate the seasonal population fluctuation of S. p. piceifrons and vegetation diversity and their association with weather factors and edaphic conditions in the gregarious zone of the Yucatán Península. The study was performed in seven sites during three seasons: North-wind (December 2013), rainy (June 2014) and dry (April 2014). The locust density was sampled in transect of 100 m2, as well as the vegetation in 16 m2: plant species richness (PSR) and relative species density (RSD), and analyzed by generalized linear models. Additionally, soil samples were obtained at 10 cm depth into a 4 × 6 m quadrat, land use in the sites was classified and temperature, precipitation and evaporation of each site were obtained from the database and they were analyzed with multiple factor analysis. The population density of S. p. piceifrons was higher in the sites Panaba, Tizimin, Tunkas and Cenotillo (F= 74.3, P < 0.0001). Characterization of vegetation showed that PSR and RSD were higher during the rainy season relative to those in the dry season (F= 50.4, P < 0.0001). RSD was identified as the most important group associated with locust density (0.86), followed by isotherm/isohyets (0.63), maximum precipitation and temperature (0.60), as well as the land use (0.65); no correlation between locust density and soil characteristics was found. Locust density was positively correlated with the abundance of the grass Panicum maximum (Sr2= 0.85, PC5= 0.87). This work shows that the population of S. p. piceifrons is high in the rainy season and influenced primarily by the abundance of the grass P. maximum and the precipitation. The results indicate that surveys for early detection and control of the locust on the Yucatán Península can focus on areas with the grass P. maximum to predict risk areas and target survey efforts. Rev. Biol. Trop. 66(1): 403-414. Epub 2018 March 01.

Resumen La langosta Centroamericana Schistocerca piceifrons piceifrons es una de las plagas más dañinas en México y Centroamérica. El presente trabajo se realizó para evaluar la fluctuación estacional de poblaciones de S. p. piceifrons y su asociación con la diversidad de vegetación, factores climáticos y edáficos en la zona gregarígena de la Península de Yucatán. Se seleccionaron siete sitios y se muestrearon a lo largo de tres estaciones: nortes (diciembre 2013), lluvias (junio 2014) y sequías (abril 2014). La densidad poblacional de la langosta fue muestreada en transectos de 100 m2, así como la vegetación en 16 m2 obteniendo la riqueza de especies vegetales (REV) y la densidad relativa de especies (DRE), y fueron analizadas por modelos lineales generalizados. Adicionalmente se obtuvieron muestras de suelo de 10 cm de profundidad en un área de 4 × 6 m, se clasificó el uso del suelo de cada sitio y se obtuvieron en una base de datos las condiciones de temperatura, precipitación y evaporación para cada sitio, estos datos se analizaron con análisis de factores múltiples. La densidad poblacional de S. p. piceifrons fue mayor en los sitios de Panaba, Tizimin, Tunkas y Cenotillo (F= 74.3, P < 0.0001). La caracterización de la vegetación mostró que la REV y la DRE fueron mayores en la estación de lluvias que en la de sequías (F= 50.4, P < 0.0001). La DRE fue el grupo más importante asociado a la densidad de la langosta (0.86), seguido por las isotermas/isoyetas (0.63) y la precipitación-temperatura máxima (0.60), así como el uso del suelo (0.65); no hubo correlación con las características del suelo. La densidad de la langosta fue correlacionada positivamente con la abundancia del pasto Panicum maximum (Sr2= 0.85, PC5= 0.87). El estudio mostró que las poblaciones de S. p. piceifrons fueron mayores en la estación lluviosa e influenciadas principalmente por la abundancia del pasto P. maximum y la precipitación. Los resultados indican que las exploraciones, la detección temprana y el control de la langosta en la Península de Yucatán puede enfocarse sobre áreas cultivadas con P. maximum para predecir áreas con riesgo y eficientar los recursos.

Elección diferencial de frutos en dos especies simpátricas de monos y murciélagos frugívoros en el sureste de México / Differential fruit choice in two simpatric monkey species and frugivorous bats in southern mexico

ABSTRACT In order to identify the role played by plant species as a food source in the fruit election of dispersing agents (Alouatta pigra Lawrence 1933, Atelesgeoffroyi Kuhl 1820 and frugivorous bats), we developed a study in dry tropical forests in Yucatan, Mexico. We recorded the fruits consumed by frugivorous bats using collectors and, for monkeys, we implemented the focal animal method. The number of fruits consumed by primates (A. pigra and A. geoffroyi) and bats were recorded, 342 and 386, respectively. It was determined that bats deposited fruits with some percentage of pulp, while monkeys contributed more with a fruits without pulp (pairwise LSD contrast p < 0.05). Among the variety of fruit species in the diet of primates, we detected that A. pigra chose mostly not an abundant species such as Enterolobium cyclocarpum Jacq. Griseb. (1860) instead of those more abundant (Manilkara zapota (L.) P. Royen (1953) and Brosimum alicastrum Sw. subsp. alicastrum C.C. Berg (1972)). The type of fruit and seed handling caused by primates would be more beneficial to seed germination than those applied by bats. Moreover, this election and fruit handling could depend on the characteristics of fruits and space-temporal availability of plant species as a food source.

RESUMEN Con el objetivo de examinar el papel que juegan las especies vegetales como fuentes alimenticias en la selección de frutos de agentes dispersores (Alouatta pigra, Ateles geoffroyi y murciélagos frugívoros), se realizó un estudio en selvas secas en el sureste de Yucatán, México. Se registraron los frutos consumidos por murciélagos usando colectores y, en el caso de los monos, se implementó el método de animal focal. El número de frutos consumidos registrados para ambas especies de primates y murciélagos fueron 342 y 386, respectivamente. Se determinó que los murciélagos depositaron frutos con pequeñas cantidades de pulpa, mientras que los monos contribuyeron mayormente con frutos totalmente despulpados (contrastes por pares LSD p < 0.05). Entre la variedad de especies de frutos en la dieta de los primates se detectó que A. pigra eligió frutos de las especies menos abundantes como Enterolobium cyclocarpum Jacq. Griseb. (1860) en vez de aquellas más abundantes (Manilkara zapota (L.) P. Royen (1953) y Brosimum alicastrum Sw. subsp. alicastrum C.C. Berg (1972)). El tipo de manejo de frutos y semillas causado por los primates sería más beneficioso para la germinación de las semillas que los aplicados por los murciélagos. Además, esta elección y manejo del fruto podría depender de sus características y la disponibilidad espacio-temporal de las especies de plantas como fuente de alimento.