Phytoseiid mites (Acari: Mesostigmata) of Tunisian citrus orchards: catalogue, biogeography and key for identification.

This study presents the results of a survey aimed to determine the species composition of phytoseiid mites on citrus trees, inter-row grasses and conifers planted as break winds within and around citrus orchards. This survey was carried out in fourty six citrus orchards in the main citrus growing regions of Tunisia, from September 2009 to August 2011. Twenty six species belonging to ten genera were found, among which eleven are new for the Tunisian fauna. This paper provides a catalogue of all these species, with some information on their biogeography and biology when available. In addition, a key for the identification of all known Tunisian species (38 species belonging to 17 genera) is given.


INTRODUCTION
Mites of the family Phytoseiidae (Mesostigmata) have been extensively studied for their potential as biological control agents of phytophagous mites (McMurtry and Croft, 1997). Several species are currently used for bio-control of mite and insect pests in several crops all over the world (McMurtry and Croft, 1997). About 2,300 phytoseiid species belonging to 90 genera have been described in this family (Chant and McMurtry, 2007). However, the fauna of all countries has not been equally surveyed (Tixier et al., 2012). Until very recently, only few species were reported from Tunisia (Kreiter et al., 2010). For a long time, Phytoseiulus persimilis Athias-Henriot was the unique species reported from this country (Gafsa, South of Tunisia) (Rambier, 1972), and many works referring to phytoseiids from Tunisia have been recently initiated (Kreiter et al., 2002(Kreiter et al., , 2004(Kreiter et al., , 2006(Kreiter et al., , 2010. A synthesis of the surveys carried out during 15 years (between 1994 and 2008) in the main crops and surrounding vegetation was reported by Kreiter et al. (2010): 27 species of phytoseiid mites belonging to 14 genera are now recorded. Among them, twelve species were identified on citrus trees (table 1).
Despite these progresses, additional studies are still necessary in order to evaluate properly the diversity of Phytoseiidae species in Tunisian ecosystems, especially in crops in order to exploit their predatory potential for biological control applicahttp://www1.montpellier.inra.fr/CBGP/acarologia/ ISSN 0044-586-X (print). ISSN 2107-7207 (electronic) 433 Sahraoui H. et al. Kreiter et al. (2010) and those presently recorded.
The present paper aims to better accurately characterize the phytoseiid mite diversity in a wide range of citrus plots, located in different growing areas, sampled on several varieties at different seasons.

MATERIALS AND METHODS
A survey of phytoseiid mites was carried out from September 2009 to August 2011, in 46 citrus orchards in the most important productive regions of Tunisia: twenty three orchards are situated in Cap Bon which is the most important citrus productive region (with a surface of about 75 % of the total citrus surface), eight orchards in Tunis (Mornag, Sidi Thabet and Ariana), six orchards in Bizerte, seven in the North West (Béja and Jandouba), one orchard in Sousse and one orchard in Kairouan (Figure 1). One hundred and eight samplings have been carried out in the 46 selected orchards: for each sam-pling, collections were carried out on citrus trees, uncultivated weeds in inter-rows and break winds trees.
Samples of each plant were individually bagged in plastic bags and transported the same day in freezing boxes to the laboratory for mite extraction. Mites were extracted from leaves using a fine hair brush and were preserved in 70 % ethanol. They were then mounted on slides using Hoyer's medium (Gutierrez, 1985) and identified using a phase contrast microscope.
The generic classification of Chant and Mc-Murtry (2007) was used for identification. Other more specific literature was used for species determination (Ferragut et al., 2009;Papadoulis et al., 2009).

RESULTS
A total of 2,759 individuals (adults) of phytoseiid mites were identified from citrus trees and associated uncultivated plants in the 46 Tunisian orchards considered.
Twenty-six phytoseiid species belonging to 10 genera were found, fifteen of them being already known and eleven are new species for Tunisia (Table 2). Among them six were found on citrus trees (Table 1), the others on weeds and conifers. First, we will present the twenty six species presently found in citrus agrosystems. Some biological data are given when available and helpful for biological control applications, the current geographic distribution of species are from Moraes et al. (2004) and Papadoulis et al. (2009). Data on the species previously recorded in Tunisia are from Kreiter et al. (2010). Then, a key of all the species of Phytoseiidae known from Tunisia is provided.  Biology -Euseius scutalis was described from Algeria by Athias-Henriot (1958). This species can be reared on pollen (Alshammeri, 2011) and was recorded as a predator of Panonychus citri (Mc Gregor) in citrus orchards (McMurtry, 1969(McMurtry, , 1977Kasap and Ekerog, 2004). Euseius scutalis has also been reported as a biological control agent of Bemisia tabaci (Gennadius) (Nomikou et al., 2003;Dale and Donald, 1986 Biology -Euseius stipulatus was classified by McMurtry and Croft (1997) as a specialized pollen feeder. This species feeds also on pest mites such as P. citri (Ferragut et al. 1988(Ferragut et al. , 1992, Tetranychus urticae Koch (Moyano et al., 2009) and eriophyid mites (Ferragut et al., 1987). ( (Berlese, 1887), this species has a wide distribution in Africa and around the Mediterranean Sea (Moraes et al., 2004). Iphiseius degenerans is described by McMurtry and Croft (1997) as a generalist (type III predator), able to feed on a wide range of foods such as thrips larvae (Messelink et al., 2005), spider mites (Nwilene and Nachman, 1996;Vantornhout et al., 2004) and pollen (van Rijn et al., 1999). This species is commercialised for the biological control of the western flower thrips Frankliniella occidentalis (Pergande) in greenhouses (Vantornhout et al., 2005). Biology -Various studies have shown its ability to control F. occidentalis (Rodriguez-Reina et al., 1992), Thrips tabaci (Lindeman) (Hansen, 1988;Bonde, 1989;Dsgaard et al., 1992) and T. urticae in cucumber (Yuqing and Petitt, 1994). Fan and Petitt (1994)   Biology -This is a very widespread species (Moraes et al., 2004). Neoseiulus californicus has characteristics of both specialist and generalist predatory mites (Castagnoli and Simoni, 2003). It prefers to feed on Tetranychidae mites (Escudero et al., 2004(Escudero et al., , 2005Greco et al., 2005;Katayama et al., 2006;Fraulo et al., 2008;Gomez et al., 2009), but can also consume other mite species like tarsonemid mites [Phytonemus pallidus (Banks)] (Easterbrook et al., 2001), small insects, such as thrips (Rodriguez et al., 1992) and even pollen when the primary prey is unavailable (Rhodes and Liburd, 2005). Biology -Neoseiulus paspalivorus was found only on coconut and on fruits, in association with A. guerreronis (Moraes et al., 2004). This species is a promising candidate for the biological control of the coconut eriophyid (Lawson-Balagbo et al., 2008).  Biology -Phytoseiulus persimilis was first collected in Algeria (Athias-Henriot, 1957). It is known mainly from Mediterranean climates around the world (Takahashi and Chant, 1993). Many studies deal with this specialist predator because of its economic importance, especially in the bio-control of T. urticae Koch in greenhouses all over the world (Mc-Murtry and Croft, 1997). Typhlodromus exhilaratus has been considered as a synonym of T. tiliae Oudemans by Denmark (1992). Additional records from Tunisia -Takelsa (Cap Bon): July -5♀ on Malva sp.

Key to the species of Phytoseiid mites of Tunisia
Thirty eight species belonging to 17 genera are known from Tunisia. Among them, 18 species were identified on citrus trees. In order to facilitate the identification of the Phytoseiidae species reported from Tunisia until now, a dichotomous key comprising these 38 species of Phytoseiidae is provided below.

DISCUSSION AND CONCLUSION
Twenty-seven species were known from Tunisia until now (Kreiter et al., 2010), including one new genus and one new species to science found in the South of Tunisia. In this study, twenty six species belonging to 10 genera were found, eleven of them being new for the Tunisian fauna. Among these species, six were found on citrus trees: Typhlodromus  (Typhlodromus) setubali, Typhlodromus (Typhlodromus) ernesti, Typhlodromus (Anthoseius) pegazzani, Typhlodromus (Anthoseius) yasminae, Proprioseiopsis bordjelaini and Paraseiulus talbii. Only one of these six species (Paraseiulus talbii) was found in two samples and two different regions (Bizerte and Cap Bon), the other species were found only once (one or two individuals per species) ( Table 2). These latter species seem thus to be rare on citrus trees. Two of the 10 newly reported species were also found on Cupressus sp. (conifer planted usually around orchards to break winds) and Tamarix sp.: Neoseiulus bicaudus and Typhlodromus (Anthoseius) yasminae. Three others were also found on weeds: Neoseiulus longilaterus, Neoseiulus alpinus, Amblyseius obtusus and Amblyseius meridionalis; all of them being rare.
Only one of the new reported species was present in many samples and several regions (Bizerte, Tunis and Cap Bon), Typhlodromus (Anthoseius) yasminae, but almost on the same plants: Cupressus sp. and Tamarix sp. (on Citrus sp. in only one sample). These new recorded species were found in Cap Bon region, North region (Bizerte), North West (Beja) and in Tunis (Ariana, Sidi Thabet, Morneg and Boumhal) ( Table 2). Even the number of citrus plots sampled in the Cap Bon region (23 plots) was higher than of Tunis (8 plots) and Bizerte (6 plots), the global diversity of Phytoseiidae in these three regions is similar (Figure 2).
Euseius stipulatus was the most abondant species on citrus trees (82 %) followed by P. persimilis, N. californicus, A. rhenanoides and T. phialatus which only represented respectively 4 %, 5 %, 3 % and 1 % of the phytoseiids collected from citrus trees. These most abundant phytoseiid species could be helplful in biological pest management programs. Since these most important species are also present in weeds, it is important to know which weed plants are favorable to these phytoseiid species. Additional studies are required to determine the factors that affect the diversity but also the abundance of preys and predators.