Thrips species ( Insecta : Thysanoptera ) associated with flowers in a restinga fragment in northeastern Brazil

With the growing volume of research involving Thysanoptera in Brazil, studies were carried out to improve our understanding of the diversity of thrips in areas where the fauna has historically been neglected. Accordingly, we recorded the diversity of thrips (Insecta: Thysanoptera) associated with a restinga fragment located on the campus of the State University of Ceará (UECE), Fortaleza, Ceará state, and computed the estimated richness and diversity indices. Samples were collected from 2011 through 2013 from flowers of 86 plant species. The material was taken to the Laboratory of Insect-Plant Interaction, where thrips were screened under stereomicroscope. We collected 456 adults and 58 immatures, representing 14 species, in addition to one unidentified species of Treherniella. Microcephalothrips abdominalis was found on a large number of host plants, and Frankliniella insularis was the most common species. About two-thirds of the total richness of thrips species was associated with three plant families (Amaranthaceae, Caesalpiniaceae and Poaceae); six thrips species were each associated with only one plant species. The richness of the species collected was close to that estimated by Bootstrap and Jackknife 1 analysis. The Shannon-Wiener (H’) and Simpson (D) diversity indexes were 1,7607 and 0.7769, respectively. Although the species are common, 46 new associations between plant species and thrips were established, 13 of which are true host associations, which demonstrates the importance of coastal vegetation in maintaining populations of thrips.


Introduction
The world fauna of Thysanopotera includes approximately 6,000 species distributed in 800 genera (ThripsWiki, 2017).In the Neotropical Region, thrips have been relatively little studied, although this region has an enormous diversity of topography and flora, including mountains, large deserts and extensive tropical forests.According to Mound (2013), most thrips species recorded in South America are from Brazil.
According to Monteiro and Mound (2012), six of the eight families of thrips are found in Brazil (Uzelothripidae, Heterothripidae Merothripidae, Aeolothripidae, Thripidae and Phlaeothripidae) with a total of 576 species (Monteiro and Lima, 2011;Lima, 2017).However, thrips have been recorded from only a small part of the Brazilian territory, especially the states of São Paulo, Rio de Janeiro, Santa Catarina and Rio Grande do Sul (Monteiro and Mound, 2012;Lima, 2017).Santa Catarina and São Paulo alone account for more than half of the thrips fauna recorded in Brazil, mainly from studies carried out by Fritz Plaumann and J. Douglas Hood in the 1940s and 1950s (Monteiro, 2002;Lima, 2017).
It is essential to carry out studies involving the interaction of thrips and their hosts in their native areas, especially in neglected regions, in order to extend our knowledge of the Brazilian thrips fauna and the position that these insects occupy in different ecosystems.One of these native areas is the coastal forest habitat known as restinga, which exists in fragments that are severely threatened by human occupation along the entire Brazilian coast.So far, no thrips surveys in this type of environment have been conducted in the country, in contrast with the situation of other insect orders, such as Lepidoptera, Coleoptera and Diptera (Flinte et al., 2006;Monteiro et al., 2007;Silveira et al., 2008;Gostinski et al., 2016).The lack of such information impedes the development of conservation and management strategies for these and other organisms.
This study assessed the diversity of thrips in restinga remnants in the state of Ceará, Brazil, as an attempt to foster research on thrips in the Brazilian Northeast.Diversity was evaluated by means of diversity indices and a species-accumulation curve.

Fieldwork
The collections were performed at points with flowering plants in a coastal forest (restinga) fragment in areas belonging to the Universidade Estadual do Ceará (UECE), Campus of Itaperi, Fortaleza, Ceará, Brazil (Figure 1).The UECE Itaperi Campus is located in the municipality of Fortaleza (03°47'45"S, 038°33'10"W, 38.4 m a.s.l.) and covers an area of 104 ha on the coastal plain, about 8 Km from the Ocean, with typical coastal vegetation (Esteves and Lacerda, 2000;IBGE, 2012), although heavily human-impacted (Brandão, 2003).This remnant is composed mainly (70%) of plants with a mean height of 6 meters that lose more than 30% of their leaves during the dry season.Aside from this, the vegetation near the campus buildings is herbaceous and shrubby, and remains green almost year-round.
A total of 86 plant species belonging to 34 families (Table 1) were sampled for thrips.Surveys were performed once a month in April, May, June and July 2011; February through August 2012; and February through August 2013.
The plants were collected randomly, depending on the availability of flowers and inflorescences, typical habitats of common thrips (Lewis, 1973(Lewis, , 1997)).Sampling was carried out between 7:00 and 9:00, and approximately 5 flowers from each species were placed in individual plastic bags and taken to the Laboratory of Insect-Plant Interaction, where the insects were screened under a stereomicroscope and the plant species were identified.The insects were stored in microtubes with AGA (10 parts of ethanol 60%, one part glycerin and one part glacial acetic acid) for preservation.

Identification
Adult thrips were mounted on permanent microscope slides and identified based on Mound and Marullo (1996).Plants were identified by comparison with herbarium specimens and using specialized literature (Bridson and Forman, 1998;Esteves and Lacerda, 2000;Brito et al., 2006;Moro et al., 2011).Vouchers of the thrips are deposited in the collection of the Laboratory of Insect-Plant Interaction (UECE).

Statistical analysis
A species-accumulation curve and species-richness estimators were calculated using the software EstimateS 9.1 (Colwell, 2013) in order to evaluate the sampling methods and to calculate the estimated richness of thrips in the particular restinga fragment.Only nonparametric incidence-based estimators (ICE, Chao 2, Jackknife 1, Jackknife 2 and Bootstrap) (Gotelli and Colwell, 2001) were computed, using the classic model with 95% confidence intervals and 1000 randomizations.Also, the diversity indices of Shannon-Wiener (H') and Simpson (D) were calculated using the software DiVes 3.0.7 (Rodrigues, 2015).The Shannon-Wiener index was also calculated using data from plant families with higher richness of associated thrips to compare possible differences in diversity.

Results
A total of 456 thrips specimens belonging to 14 species were found in association with the coastal vegetation.Fifty-eight immatures (13 Tubulifera and 45 Terebrantia) were also found.The insects were associated with 36 of the 86 plant species sampled (Table 2).One probable new species of Treherniella was collected, and 46 new associations between thrips species and plants were established (Table 2), of which 13 are true host associations based on larvae collection (Table 2).
The accumulation curve did not reach an asymptote.The results obtained with the Chao 2, ICE and Jackknife 2 estimators indicate that at least ten more species may exist in the area.On the other hand, the resulting estimates of Bootstrap (17.88) and Jackknife 1 (22.58) are closer to the number of species effectively surveyed (Figure 2).
The Shannon-Wiener (H') and Simpson (D) indices for the sampled area were 1,7607 and 0.7769 respectively (Table 3).Thrips richness and abundance were concentrated in three plant families, Amaranthaceae, Caesalpiniaceae and Poaceae.Plant species of the three families harbored two-thirds of the thrips species collected, and about half of the thrips abundance sampled (Tables 1 and 2).

Discussion
This study established the first records of association between several thrips species and restinga plants in Brazil (Table 2).Fourteen species (seven of which, Androthrips ramachandrai, Frankliniella brevicaulis, F. gemina, F. insularis, F. tritici, Haplothrips gowdeyi, Heliothrips haemorrhoidalis, are new records) are added to the total known from state of Ceará, and the genus Treherniella is a new record in Brazil.This genus has been found on members of Poaceae in native vegetation in northern Italy (Marullo and Grazia, 2013), as well as in southern United States (Diffie et al., 2008) and in Paraguay and Argentina (ThripsWiki, 2017).Apart from Treherniella sp., all thrips species sampled in our study have been found in surveys conducted in different states of Brazil, i.e.Piauí and Maranhão (Lima and Zucchi, 2016), Rio Grande do Norte (Cavalleri et al., 2011) and Rio Grande do Sul (Pinent et al., 2005(Pinent et al., , 2006)).
Most of these species are phytophagous, except for A. ramachandrai, a predator of Gynaikothrips spp.(Melo et al., 2013).The fiding 46 new associations of plant species with thrips in Brazil, along with the 13 true host associations demonstrates the importance of coastal vegetation in maintaining populations of thrips.Although the species identified are common on cultivated plants in other areas of Brazil, the failure to find other different species in the vegetation of this area is probably related to the degree of environmental alteration.
In southern Brazil, other studies in a natural area found a thrips richness in Itapuã State Park (Cavalleri, 2005;Pinent et al., 2005Pinent et al., , 2006) ) that is double the level observed in our study.However, the incomplete stabilization of the species-accumulation curve indicates that a higher richness of thrips species may be found in the fragments of coastal vegetation sampled.Moreover, the collection effort (number of surveys) and specimens collected was also higher in Rio Grande do Sul.Therefore, an increase in collection efforts may well demonstrate a higher richness of thrips species in the restinga fragment sampled here.
The diversity indices calculated in our study indicate that some species are more abundant in the area, thus leaving the diversity relatively low.The Simpson Index of the complete sample was close to 1 (Table 3), a result of the high abundances of a few species (mainly F. insularis and Microcephalothrips abdominalis).The diversity levels within the plant families with the highest richness of thrips species were slightly higher.This can be explained by the exclusion of species with low abundance collected from other plant families (Table 2).Cavalleri (2005), in Rio Grande do Sul, found a higher diversity (D = 0.211), as the species showed more uniform abundances.
The Shannon-Weiner index also indicated a low diversity.In Itapuã State Park, the index value was 2.19 and there were differences between the plant family with the highest thrips richness (Asteraceae) and the other families (Cavalleri, 2005).Although the collection methods used by the author are different, these comparisons give an idea of the relative diversity of these different areas.
In Brazil, very few systematic surveys of thrips in natural ecosystems have been performed, and there are no assessments of the importance of preserving natural areas for conservation of these insects.Especially in the northeast region of this country, where the biodiversity of these insects is little known, efforts must be made to better understand the patterns and size of thrips populations.Restinga fragments in Brazil are fragile ecosystems threatened by human settlement.The area studied here is located near to built-up areas of one of the largest cities in northeastern Brazil, and is under environmental stress.The existence of a diverse fauna of insects harbored by many plant species is an important reason to carry out efforts for their conservation.

Figure 2 .
Figure 2. Species accumulation curve and richness estimators for thrips species recorded in restinga fragment in the municipality of Fortaleza, Ceará, Brazil from 2011 through 2013.

Table 2 .
Thrips species of thrips and their respective hosts in fragment of restinga vegetation in the municipality of Fortaleza, Ceará, Brazil.
*New records of association with plant species in Brazil; +Host-associations based on larvae collection.

Table 3 .
Diversity indices of the thrips species in restinga fragment in the municipality of Fortaleza, Ceará, Brazil.