Insect galls from Córdoba, Argentina: a case where stem galls predomínate / Agallas de insectos en Córdoba, Argentina: un caso en el que predominan las agallas caulinares

Abstract Galls are structures produced by plants in response to the activity of several types of organisms. Gall-inducing species have a close relationship with their host plant, as their habitat is largely restricted to the gall and the plant organ in which it develops. All plant organs are susceptible to gall induction by insects, the leaves being the most vulnerable. Knowledge about interactions between gall-inducing insects and plants is fragmented and incomplete in Argentina. In this study, we completed an inventory of galls induced by insects on plants in Córdoba (central Argentina) using information from field surveys and a review of the literature. We also focused on the frequency of plant-insect taxonomic associations and plant organs most commonly attacked by gall-inducing insects. Field surveys were performed systematically in 26 sites of Chaco Serrano, which were visited five times in two consecutive years, and in 17 sites of the province, which were sampled one or two times each. A comprehensive literature search of electronic and conventional databases was also conducted to complete the inventory. A total of 99 gall morphospecies on 58 plant species (21 families and 44 genera) were recorded through both field surveys and a literature review, enlarging the list of species available for the region by almost 50 %. Asteraceae and Fabaceae were the plant families most attacked by galling insects, in partial concordance with the most species-rich plant families in the region. Diptera, particularly the family Cecidomyiidae, was the most species-rich group in the community of galling insects, which is in agreement with different studies across the globe. Baccharis was the genus displaying the highest number of gall morphotypes, followed by Acacia, Condalia, Geoffroea, Prosopis and Schinus. Almost 60 % of the morphotypes were stem galls, a pattern uncommon in the literature. Fusiform and globoid-shaped galls were predominant. Our study highlights the scarce knowledge there is about the interactions between plants and gall-inducing insects in Argentina, particularly those involving species of Cecidomyiidae, with more than 30 undescribed species. Possible mechanisms involved in the predominance of stem galls in central Argentina are discussed. Rev. Biol. Trop. 66(3): 1135-1148. Epub 2018 September 01.

Resumen Las agallas son estructuras producidas por las plantas en respuesta a la actividad de diversos tipos de organismos, los cuales establecen una estrecha relación con sus especies hospedantes, ya que su hábitat está restringido en gran medida a la agalla y al órgano vegetal donde la agalla se desarrolla. Todos los órganos vegetales son susceptibles a la inducción de agallas por insectos, siendo las hojas los más frecuentemente atacados. En Argentina, el conocimiento de estas interacciones es fragmentando e incompleto. En el presente estudio, se realizó un inventario de agallas inducidas por insectos utilizando información obtenida de muestreos a campo y revisión bibliográfica. También nos enfocamos en las asociaciones taxonómicas insecto-planta más frecuentes y en los órganos vegetales más atacados por los insectos cecidógenos. Se realizaron muestreos a campo en 26 sitios localizados en el Chaco Serrano, que fueron visitados cinco veces en dos años consecutivos y en otros 17 sitios, distribuidos en la provincia de Córdoba, que fueron visitados una o dos veces. Además se realizó una exhaustiva revisión bibliográfica en bases de datos electrónicas (disponibles en internet) y convencionales. Un total de 99 agallas en 58 especies vegetales (21 familias y 44 géneros) fueron registradas a través de los muestreos en el campo y la revisión bibliográfica, ampliando el número de interacciones previamente conocidas en al menos un 50 %. Las familias vegetales más atacadas fueron Asteraceae y Fabaceae, coincidiendo con las familias vegetales más diversas de la región. La familia Cecidomyiidae (Diptera) presentó el mayor número de especies, en concordancia con diversos estudios alrededor del mundo. Baccharis fue el género vegetal que mayor número de morfotipos de agallas albergó, seguido por Acacia, Condalia, Geoffroea, Prosopis y Schinus. Al menos el 60 % de morfotipos registrados se presentaron en tallos, un patrón poco común en la bibliografía. Las formas predominantes fueron fusiforme y globoide. Nuestra investigación revela el escaso conocimiento sobre la comunidad de insectos cecidógenos y sus agallas en Argentina, particularmente de las inducidas por especies de la familia Cecidomyiidae, con más de 30 especies aún no descritas. Se discuten posibles mecanismos involucrados en la predominancia de agallas caulinares en el centro de Argentina.

Insect Galls of the Parque Nacional do Itatiaia (Southeast Region, Brazil)

ABSTRACT The Parque Nacional do Itatiaia (PNI) (Brazilian Southeast Region) was surveyed monthly for insect galls from February/2014 to December/ 2015. A total of 432 gall morphotypes were found. This number places the PNI as the richest Atlantic forest area in number of gall morphotypes. The galls were found on 47 plant families. Among them, Asteraceae were pointed out as the superhost. The gall richness in the lower part of the PNI is higher than that of the plateau. The insect galls were found in 154 native, 56 endemic and only one exotic plant species. Concerning the conservational status, the host plants include two vulnerable species with three morphotypes together. Several new botanical records were reported. Leaves were the most galled plant organ, followed by stems. Globoid, green, glabrous and one-chambered galls were the most frequent. Cecidomyiidae were the most common gallers. Parasitoids, successors and inquilines composed the associated fauna.