Elevational and seasonal patterns of plant pollinator networks in two highland tropical ecosystems in Costa Rica.

Many plant species in high montane ecosystems rely on animal pollination for sexual reproduction, however, our understanding of plant-pollinator interactions in tropical montane habitats is still limited. We compared species diversity and composition of blooming plants and floral visitors, and the structure of plant-floral visitor networks between the Montane Forest and Paramo ecosystems in Costa Rica. We also studied the influence of seasonality on species composition and interaction structure. Given the severe climatic conditions experienced by organisms in habitats above treeline, we expected lower plant and insect richness, as well as less specialized and smaller pollination networks in the Paramo than in Montane Forest where climatic conditions are milder and understory plants are better protected. Accordingly, we found that blooming plants and floral visitor species richness was higher in the Montane Forest than in the Paramo, and in both ecosystems species richness of blooming plants and floral visitors was higher in the rainy season than in the dry season. Interaction networks in the Paramo were smaller and more nested, with lower levels of specialization and modularity than those in the Montane Forest, but there were no seasonal differences within either ecosystem. Beta diversity analyses indicate that differences between ecosystems are likely explained by species turnover, whereas within the Montane Forest differences between seasons are more likely explained by the rewiring of interactions. Results indicate that the decrease in species diversity with elevation affects network structure, increasing nestedness and reducing specialization and modularity.

Aerial plankton from the Eastern Tropical Pacific

Introduction: Small terrestrial invertebrates disperse in a passive manner through wind currents, forming what is known as aerial plankton, which has not been surveyed yet for the Eastern Tropical Pacific. Documenting the aerial plankton of Isla del Coco will allow to better understand the colonization process of this highly diverse island. Objective: Characterize the aerial plankton present on the transect Puntarenas - Isla del Coco. Methods: Specimens were collected using entomological nets on 2 roundtrip voyages during the months of July and August of 2017 and 2018, respectively. Results: A total of 10 morpho-species were collected corresponding to the orders: Diptera (Ceratopogonidae, Milichiidae, and Nematocera of a non-identified family), Hymenoptera (Chalcidoidea: Agaonidae), Hemiptera (Scutelleridae and Coreidae) and Lepidoptera (Sphingidae). Diptera and Hymenoptera were collected on the nets; while, Hemiptera and Lepidoptera were found on the deck of the boat. No spiders were collected. The Diptera and Hymenoptera families, as well as the family Coreidae (Hemiptera), have been previously recorded on this type of surveys across the tropical Pacific. Conclusions: Two of the taxa collected by nets, Ceratopogonidae (Diptera) and Chalcidoidea (Hymenoptera), have representatives on Isla del Coco, which could provide direct support for wind dispersal as a colonization mechanism for these groups. We also detected other insects (i.e. Lepidoptera and Scutelleridae-Hemiptera) which most likely reached the boat by their own means providing evidence of their dispersal abilities. This research provides data to further expand on questions about the mechanisms of island colonization.

Introducción: Los invertebrados terrestres pequeños se dispersan de manera pasiva en corrientes de viento, constituyendo lo que se conoce como plancton aéreo, el cual previamente no había sido evaluado en Pacífico Tropical Oriental (PTO). Documentar el plancton aéreo de la Isla del Coco permitiría entender mejor el proceso de colonización de esta diversa isla. Objetivos: Caracterizar el plancton aéreo del transecto Puntarenas - Isla del Coco. Métodos: Los especímenes fueron recolectados utilizando redes entomológicas en 2 viajes de ida y vuelta durante los meses de Julio y Agosto de 2017 y 2018, respectivamente. Resultados: Un total de 10 morfo-especies fueron recolectadas, correspondientes a los órdenes Diptera (Ceratopogonidae, Milichiidae, y Nematocera de familia no identificada), Hymenoptera (Chalcidoidea: Agaonidae), Hemiptera (Scutelleridae y Coreidae) y Lepidoptera (Sphingidae). Diptera e Hymenoptera fueron recolectados en las redes; mientras que Hemiptera y Lepidoptera fueron encontrados en la cubierta del barco. No se recolectaron arañas. Las familias de Diptera e Hymenoptera, al igual que la familia Coreidae (Hemiptera) han sido previamente registradas en este tipo de muestreos en el PTO. Conclusiones: Dos de los taxones recolectados en las redes, Ceratopogonidae (Diptera) y Chalcidoidea (Hymenoptera), están representados en la Isla del Coco, lo cual provee apoyo directo a la dispersión por viento como un mecanismo de colonización para estos grupos. Igualmente, encontramos otros insectos (Lepidoptera y Hemiptera: Scutelleridae), los cuales probablemente llegaron al barco por sus propios medios, evidenciando sus habilidades de dispersión. Esta investigación entrega datos para responder nuevas preguntas sobre los mecanismos de colonización de islas.

Sampling scarab beetles in tropical forests: the effect of light source and night sampling periods.

Light traps have been used widely to sample insect abundance and diversity, but their performance for sampling scarab beetles in tropical forests based on light source type and sampling hours throughout the night has not been evaluated. The efficiency of mercury-vapour lamps, cool white light and ultraviolet light sources in attracting Dynastinae, Melolonthinae and Rutelinae scarab beetles, and the most adequate period of the night to carry out the sampling was tested in different forest areas of Costa Rica. Our results showed that light source wavelengths and hours of sampling influenced scarab beetle catches. No significant differences were observed in trap performance between the ultraviolet light and mercury-vapour traps, whereas these two methods caught significantly more species richness and abundance than cool white light traps. Species composition also varied between methods. Large differences appear between catches in the sampling period, with the first five hours of the night being more effective than the last five hours. Because of their high efficiency and logistic advantages, we recommend ultraviolet light traps deployed during the first hours of the night as the best sampling method for biodiversity studies of those scarab beetles in tropical forests.