Galls of Cecidoses eremita Curtis and Eucecidoses minutanus Brèthes ( Lepidoptera : Cecidosidae ) in Magdalena , Buenos Aires Province : preliminary study and associated fauna

In Argentina, five galling species of the family Cecidosidae (Lepidoptera), including Cecidoses eremita Curtis and Eucecidoses minutanus Brèthes, have been cited. This note reports a preliminary study of their galls in “molles” (Schinus longifolius (Lindl.) Speg.) of Magdalena (Buenos Aires, Argentina). In April 2013, galls of C. eremita and E. minutanus were censused in randomly selected “molles”. In April and December 2013, randomly selected galls were then collected and transported to our laboratory in hermetic bags, and conserved at -18 oC until examination. Maximum diameter and wall thickness of collected galls were measured. About 84% of the observed “molles” (103/123) had galls of C. eremita and/or E. minutanus. The median of galls per tree was 12 (Q1=6; Q3=22). Eucecidoses minutanus had galls with smaller diameter (U11;53= 583; P<0.05) and thinner wall (U10;52=506.5; P<0..05) than C. eremita. In open galls, we found Pseudoescorpionida, Araneae (Segestriidae and Salticidae), and larvae of Lepidoptera and Hymenoptera. Within closed galls, we found adults of Torymidae and Chalcidoidea, and larvae of Ichneumonoidea.


Introduction
Gall formation in plant tissues is induced by galling organisms, mainly insects.The response to the stimulus from gall-making insects is the development of a specific morphological structure originated by hypertrophy (abnormal growth) and hyperplasia (increase in cell size).This structure or gall provides food and shelter for the gall-inducing organism (Nieves-Aldrey 1998, Stone & Schönrogge 2003, Albert et al. 2011, Dias et al. 2013).Galls also show associated fauna of parasitoids and inquiline species (Pujade-Villar & Ros-Farré 1998, Askew et al. 2013, Kuzmanich et al. 2015).
In South America, most studies have been carried out in Brazil.In Argentina, the first lists of gall-inducing organisms and their associated fauna were published in 1916 and 1917 by Brèthes and Jörgensen respectively.These first lists named five gall-inducing species of the family Cecidosidae (Incurvarioidea, Lepidoptera)  The galls of C. eremita and E. minutanus, named "matecitos" or "tabaneras" by inhabitants of Buenos Aires Province, are globose stem galls and smooth surface and glabrous.The colour is firstly green and brown later.They have a single spherical larval chamber, and an operculum that can be open or closed when it is covered by an opercular cap (see Figure 1).These galls are found in large numbers in the branches of Schinus longifolius (Lindl.)Speg.(Jörgensen 1917).
The aim of this communication is to report a preliminary survey of the abundance of galls produced by E. minutanus and C. eremita and the results of the examination of galls collected from different individuals of "molle" (Schinus longifolius (Lindl.)Speg.) located in an area of conserved native forest ("talar") at the Magdalena District, Buenos Aires Province, Argentina.

Material and Methods
The study was carried out in the El Destino Reserve, Magdalena District, Buenos Aires Province (35º 8'S, 57º 23'W).This Reserve is located in the Pampa Deprimida, a plaine with dominant grassland and few forest.The annual mean temperature is 15ºC and the annual mean rainfall 970 mm.
In April 2013, the galls of C. eremita and E. minutanus were censused until two meters high in 123 randomly selected trees in a patch with conserved native forest ("talar").
The censused trees were selected through a systematic sampling with k=2, and were marked with a code number.
For the census, the galls were classified as open (without opercular cap) or closed (with opercular cap).Additionally, in April and December 2013, E. minutanus and C. eremita galls were randomly collected and examined.The collection method consisted of three stages: first, 32 trees (16 trees in April and 16 in December) were selected using a table of random numbers; second, two branches of each tree were selected.For the selection of branches, we used a random number between 1 and 5 and selected the branches with equal number by counting the branches from the soil to the crown.Finally, we collected the first gall observed by visually inspecting the branch from the trunk to its distal end.
Collected galls were transported to the laboratory in hermetic bags, and conserved at -18ºC until examined.The diameter and the wall thickness were measured in each gall by means of a calliper.The wall thickness was measured after a cut at sagittal plane of the gall by a mini saw.
The inside of galls was examined with a stereoscopic microscope.The observed organisms were kept in alcohol 70% until their identification.
The data of the diameter and wall thickness in the galls of both species were tested using Shapiro Wilk test for normality (Shapiro & Wilk 1965).Differences between the galls of both species in the diameter and wall thickness were tested using the Wilcoxon rank sum test (non-parametric data, Siegel & Castellan 1995).
The gall numbers of each species with presence of the original pupa or other organisms are shown in Table 2.In the open galls of E. minutanus with presence of other organisms, we observed an exuvia of Pseudoescorpionida and a larva of suborder Symphyta (Hymenoptera).In the open galls of C. eremita, we found three spiders: one specimen of Ariadna boesenbergi Keyserling 1877 (Segestriidae), one specimen of the family Salticidae (Hernán Iuri, personal communication), and a group of spiders recently hatched that could not be identified.Another open gall held a Lepidoptera larva and four galls held arthropod remains that could not be identified by their degree of decomposition.
One of the three closed galls of E. minutanus held an adult of the family Torymidae (Hymenoptera) (Juan José Martínez, personal communication) and showed six little holes in its wall.Seven of the 24 closed galls of C. eremita held other organisms: three held two or three Ichneumonoidea larvae (Hymenoptera) (Juan José Martínez, personal communication), one held an adult of the family Chalcidoidea (Hymenoptera) and an unidentified larva, and the remaining galls held other insect larvae that could not be identified.All observed galls had only one chamber.

Discussion
Gall inducers show a high level of specificity to their host plants, although some plant species have different galler species (Cuevas-Reyes et al. 2003, Veldtman & McGeoch 2003).Schinus longifolius (Lindl.)Speg.and other species of the family Anacardiaceae show several specific galler species.In a survey to identify the gall-inducing insects in the region of the Río de la Plata, 15% of all the gall morphotypes found were observed in Schinus longifolius (Lindl.)Speg., a species that would have "super host" characteristics (Veldtman & McGeoch 2003, Kuzmanich et al. 2015).In our study area, galls of four species, including C. eremita, E. minutanus, D. congregatella (Lepidoptera: Cecidosidae), and other leaf gallers (possibly family Calophyidae (Psylloidea) (Burckhardt & Basset 2000, Kuzmanich et al. 2015), have been observed in Schinus longifolius (Lindl.)Speg.The presence of four galler species and the high percentage of trees with galls could be due to the great abundance of this host tree in the study area (Cuevas Reyes et al. 2004).Some authors have found an inverse relationship between the gall number and the age of host plant for several leaf gallers, and proposed that young leaves have higher nutrient value than old leaves (Washburn & Cornell 1981, Price et al. 1987, Cuevas Reyes et al. 2004).Although our sampling included few saplings (nine), none of them showed galls of C. eremita or E. minutanus.Future studies should evaluate the potential relationship between the presence of this species and the age of the host Schinus longifolius (Lindl.)Speg.
In this preliminary study, we found that 12.9% of the closed galls of C. eremita contained some parasitoid Hymenoptera.The proportion of galls with parasitoids is very variable in space and time.Several galler-host systems have been studied by different authors.Washburn & Cornell (1981) found that the percentages of leaf galls of the cynipid Xanthoteras politum (Bassett) with parasitoids varied between 3 and 18%.Wool & Burstein (1991) detected between 13-33% of Smynthurodes betae (Aphididae) galls housing parasitoids in different sites.Almeida et al. (2006) detected 2.5% of parasitism by insect parasitoids in galls induced by Anisodiplosis waltheriae Maia (Diptera: Cecidomyiidae) while in other Cecidomyiidae Maia & Tavares (2000) observed along 12 months parasitoidism rates between 32-79% in Cordiamyia globosa Maia (Diptera: Cecidomyiidae).
The gall abundance in host trees, the morphometric variables of galls and the proportion of galls with parasitoids are original contributions of this study because they may allow comparisons in space and time in the area and because there are no previous reports for the two species studied in the present study.In addition, the "talar" is the only native forest of Buenos Aires Province and an environment with conservation value.Thus, the study of gall-inducing species and their parasitoids or associated organisms becomes important for the design of policies on conservation of biodiversity.