Biogeographical analysis within the family Phytoseiidae Berlese (Acari: Mesostigmata): an example from the large sub-genus Typhlodromus (Anthoseius) De Leon

A BSTRACT — Despite their great interest for pest management, the biogeography of the Phytoseiidae is still poorly known. This study focuses on the spatial distribution of one of the largest taxa within the family: the sub-genus Typhlodromus (Anthoseius) currently comprising 322 species. It also provides a description of ﬁve discrete morphological characters used to discriminate between species and easily observed. This survey is the ﬁrst analysis of the combined distribution of both species and associated morphological characters within the family Phytoseiidae. It reveals the great utility of taxonomic data compilation and associated databases for aspects beyong alpha-taxonomy. The highest number of species of Typhlodromus (Anthoseius) was reported from the East Palearctic region and the lowest from the Neotropical province. This was quite surprising as the highest species diversity of Phytoseiidae is reported from this latter region. Several hypotheses are discussed to explain this observation. In provinces showing the highest number of Typhlodromus (Anthoseius) species, we usually also observed the most diverse morphological forms for the ﬁve characters considered. High endemism levels were observed in all the provinces considered, even those where only few species were reported (especially the Neotropical province). Possible synonymies are thus discussed, as species could have been described more than once in different biogeographic provinces. Furthermore, some hypotheses are discussed to explain the high species and morphological diversity of the sub-genus Typhlodromus (Anthoseius) in the West and East Palaearctic regions. Further phylogenetic analyses are required to test these different hypotheses.


INTRODUCTION
The family Phytoseiidae Berlese (Acari: Mesostigmata) includes the most frequent predatory mites found on plants. Several species are used in the bio-control of mite and insect pests in several crops all over the world (McMurtry and Croft 1997;Gerson et al. 2003). It is also the family containing the highest number of known species within the or-der Mesostigmata, with more than 2,250 species described worldwide (Moraes et al. 2004;Chant and McMurtry 2007;Krantz and Walter 2009).
Despite its great interest for pest management, many aspects of Phytoseiidae distribution still remain poorly analyzed. Recently, the computerization and compilation of those data have been initiated (Tixier et al. unpub. database). Tixier et al. (2008a) analyzed the biogeographic distribution of the whole family, opening new perspectives for further studies on the distribution and occurrence of each genus. Indeed, understanding the distribution of taxa could help (i) in building a clearer picture of the evolutionary scenario of the considered group (Brown and Lomolino 1998;Humphries and Parenti 1999) and (ii) in more applied grounds, in searching for new predatory species to be employed in bio-control programs. This paper focuses on the biogeographic distribution of the known species of a specific sub-genus of the family Phytoseiidae, sub-family Typhlodrominae: Typhlodromus (Anthoseius) De Leon. Together, with its sister group [sub-genus Typhlodromus (Typhlodromus) Scheuten], it forms the genus Typhlodromus Scheuten, which is included in the tribe Typhlodromini with two other genera: Neoseiulella Muma and Typhloseiulus Chant and McMurtry (Chant and McMurtry 2007). The sub-genus Typhlodromus (Anthoseius), currently comprising 322 valid species and at least 20 suspected synonymies, is one of the largest within the family (Moraes et al. 2004;Chant and McMurtry 2007;Faraji et al. 2008Faraji et al. , 2011El-Banhawy et al. 2009;Rahmani et al. 2010;El-Banhawy and Knapp 2011;Jafari et al. 2011). Very few studies have provided revisions of this large group. Ueckermann and Loots (1988) and Ueckermann et al. (2008) revised the African species of Typhlodromus (Anthoseius). Denmark and Welbourn (2002) only listed 236 species in their world revision of the genus Amblydromella Muma, considered a junior synonym of Typhlodromus (Anthoseius) (Moraes et al. 2004, Chant andMcMurtry 2007). We herein considered species of the sub-genus Typhlodromus (Anthoseius) as defined by Chant and McMurtry (2007): presence of the setae z3, s6, S5 and absence of Z1, all dorsal setae thin, ventrianal shield not reduced (Chant andMcMurtry 1994, 2007). Species of this subgenus are delimitated with some discrete characters (peritreme length, number of solenostomes on the dorsal and ventrianal shields, number of setae on the sternal and on ventrianal shields) but also with continuous characters as the dorsal and leg setal lengths (Denmark and Welbourn 2002;Ueckermann et al. 2008;Papadoulis et al. 2009;Ferragut et al. 2010).
The first objective of the present study was to provide an exhaustive survey of the geographic distribution of the known species of Typhlodromus (Anthoseius). The second objective was to determine whether the species found since now in each of the seven biogeographical provinces bear specific morphologically discrete features. Considering the low number of morphological characters available and the difficulty to encode them (especially for continuous characters), as well as the difficulty of examining all type specimens, we believe it would certainly be premature to carry out a proper phylogenetic analysis at this point. Thus, our objective was only to provide a description of the relationships between geographical distribution and morphological attributes in the aforementioned group.

Species distribution
Data on the geographic distribution of species were obtained from the two world catalogues of the family Phytoseiidae (Moraes et al. 1986(Moraes et al. , 2004 and from subsequent papers (e.g. Bayan and Merheb 2006;Ueckermann et al. 2008Ueckermann et al. , 2009Faraji et al. 2008Faraji et al. , 2011El-Banhawy et al. 2009;Rahmani et al. 2010;El-Banhawy and Knapp 2011;Jafari et al. 2011). Since no geographical data was available for neither Typhlodromus (Anthoseius) wichmanni Hirschmann nor T. (T.) chanti Hirschmann those two species were not considered in the present analysis.
The zoogeographic provinces used in the analysis are those defined by Sclater (1858) and Wallace (1876). These areas, initially called realms, were based on the taxonomic or phylogenetic relationships of animals (especially vertebrates) and not on the adaptations to specific environments (Ebach and Humphries 2002). Despite the fact that the data used to delineate provinces were compiled long before advances in Palaeontology and the theory of Continental Drift, the basic concept of distribution and the names of the zoogeographic provinces are still in use today (Humphries and Parenti 1999;Cox 2001). The biogeographic provinces considered are as follows: Nearctic (North America excluding Florida), Neotropical (South and Central  The database used for analyses includes the occurrence (presence/absence) of 320 species among the 322 presently described in the seven biogeographic regions (appendix 1). Species numbers and endemism levels were evaluated; endemism was considered when one species was reported only from a single biogeographic province.
Jaccard similarity indices were calculated between the areas as follows: I = C / (N 1 + N 2 -C), where C is the number of species present in both areas, N 1 is the total number of species in area 1, and N 2 is the total number of species in area 2 (Brown and Lomolino 1998).

Spatial distribution of characters
Terminologies for chaetotaxy, poroidotaxy and adenotaxy used in this paper follow those proposed by Lindquist and Evans (1965) as adapted by Rowell et al. (1978) for the Phytoseiidae, and Athias-Henriot (1975), respectively.
The study of the spatial distribution of five qualitative discrete characters was carried out. We have chosen to analyze qualitative discrete characters in order to avoid interpretation errors (as it could be the case for continuous characters such as setae lengths). Furthermore, they were quite easy to observe, and at the same time universally reported in description and re-descriptions. Finally, the five characters selected are currently used in species diagnostic (Ueckermann and Loots 1988;Denmark and Welbourn 2002;Ueckermann et al. 2008). Some rare intraspecific variations were observed but further experiments for testing if these variations really correspond to intraspecific morpholines would be clearly required (Rahmani et al. 2010, Jafari et al. 2011. The characters considered were as follows: 1. number of setae on the sternal shield, some species bear two pairs (ST1 and ST2) whereas others bear three (ST1, ST2, ST3); 2. number of preanal setae on the ventrianal shield (VAS), some species bear two pairs, while others bear three or four; 3. presence of the pores gv3 on the ventrianal shield; 4. number of solenostomes on the dorsal shield (ranging between one and seven: gd1, gd2, gd4, gd5, gd6, gd8, gd9); 5. peritreme length: 4 character states were considered, peritreme reaching at the levels of j1, between j1-j3, between j3-z2 or between z4-s4 (Figures 1 A-C).
To determine the state of these five characters, we used the original descriptions but also subsequent publications to check for the stability of the character state within a same species. However, although the overall literature on the sub-genus Typhlodromus (Anthoseius) was considered, information was not equally available for all the species and characters because of the poor quality and/or succinct descriptions. For some species, inconclusive characters were thus not considered. The most problematic feature was the number of solenostomes on the dorsal shield, because sometimes this was not mentioned in the description text, and drawings were often unclear. Furthermore, some authors (e.g. Gupta 1970) referred to solenostomes as "pairs of visible pores". In those cases, again, it is not conclusive to assume that those correspond to solenostomes, or rather to other types of dorsal pores (e.g. poroids).

Species distribution
Species of the sub-genus Typhlodromus (Anthoseius) occur in the seven biogeographic provinces (Table 1). Distribution of species in these provinces are significantly different (Chi2 (1, 6) = 210.16; P < 0.05). Only seven species have been found in more than one biogeographic province [T.  (Table 2). The East Palaearctic province shows the highest diversity (99 species), followed by the Ethiopian (87 species), the West Palaearctic (63 species) and the Oriental (59 species) provinces. Conversely, relatively few species are reported from the Neotropical (10 species), Nearctic (12 species) and Australasian (11 species) provinces ( Table 1).
The great majority of species (313 species; 97.8 %) are endemic to a single geographic province. Five provinces have endemism rates of at least 90 % (Table 1). The highest endemism levels are observed in the four most species-rich areas (West Palaearctic, East Palaearctic, Ethiopian and Oriental) but also in the Neotropical province despite the low number of species reported in this latter area (10 species). The lowest endemism rate (50 %) is observed in the Nearctic province.
Jaccard indices were globally low, ranging from 0.93 % to 15 % (Table 3), which agrees with the high endemism rates previously discussed. The highest similarity rate is observed between the Nearctic and Australasian provinces (15 %) but this high rate is due to the occurrence of three species [T. (A.) bakeri, T. (A.) caudiglans, and T. (A.) transvaalensis] that are present in at least five provinces among the seven considered. The second highest similarity rate is observed between the Nearctic and West Palaearctic provinces (7.14 %). Again, among the five species common to these two provinces, four are worldwide distributed whereas a single one -T. (A.) rhenanoides -is only present in these two regions. Similarities around 5 % are noted between (i) Nearctic and Neotropical provinces (4.76 %), the single species in common, T.     transvaalensis]. Finally, four species are simultaneously found in the Nearctic and Oriental provinces (similarity of 5.97 %). However, again these species are the most worldwide distributed.

Spatial character distribution
Number of setae inserted on the sternal shield.
The number of species with two pairs (157 species) of setae on the sternal shield is slightly higher than the number of species bearing three pairs (  they constitute the prevailing species. Species with two pairs of setae are also numerous in the East Palaearctic and Oriental provinces; however, in those areas they do not constitute the prevailing ones. No species with three setae on the sternal shield is reported from the Neotropical province and very few in the Nearctic and Australasian areas ( Figure 2).

Number of setae inserted on the ventrianal shield (VAS).
Most species of Typhlodromus (Anthoseius) (280 species) have four pairs of pre-anal setae on the VAS; 31 species have three pairs whereas only four species have two ( Figure 3). Species with four or three pairs are reported from all the seven provinces. However, they tend to be more numerous in the Palaearctic (both East and West), Oriental and Ethiopian provinces, which might be simply due to the higher number of species found in those provinces. Considering thus the percent of species bearing these features in each province (  Presence of pores gv3 on the ventrianal shield. gv3 Most species (262 species) of the sub-genus Typhlodromus (Anthoseius) have a pair of pores gv3 on the ventrianal shield. These species are found mostly in the East Palaearctic (82 species), Ethiopian (80 species), Oriental (50 species), and West Palaearctic (40 species) provinces ( Figure 4). Species reported from the Australasian and Nearctic provinces all bear a pore, as well as the majority of the Neotropical species.
Number of solenostomes on the dorsal shield.
The majority of the species of Typhlodromus (Anthoseius) for which this feature could be observed, has five solenostomes on the dorsal shield (126 species). They are found in all the seven geographic provinces, the highest number being reported from the Ethiopian (58 species) and the Palaearctic provinces (EP: 33 species, WP: 30 species) ( Figure   5). Species with four solenostomes (24 species) are particularly numerous in the Palaearctic provinces (11 species in EP and 8 in WP). Species with three solenostomes are absent from the Neotropical zone, again these species are more commonly found in the Palaearctic provinces. Four species have only one solenostome (gd2), one is reported from the WP province [Typhlodromus (Anthoseius) serratus ( Knapp are reported to have 6 solenostomes, the former being endemic to the East Palaearctic province and the latter endemic to the Ethiopian region. Only one species, endemic to the Oriental province, has 7 solenostomes [T. (A.) pruni Gupta] ( Figure 5).
Regions showing the highest diversity in the number of solenostomes are the Oriental, Ethiopian and the two Palaearctic provinces.

Peritreme length.
In most of the species (216 species), the peritreme reaches the level of the dorsal setae j1; only relatively few species show other positions. Species with this feature are numerous in all the provinces ( Figure 6). Most of the species endemic to the Australasian and Neotropical provinces have the peritreme at j1 position. Species with the shortest peritreme (15 species in total), i.e. reaching the level of dorsal setae z4 to s4, are only present in the Palaearctic (8 species in WP, 3 species in EP), Oriental (3 species) and the Nearctic (1 species) provinces. Two types of peritreme are observed in species endemic to the Australasian province, and three in the endemic species of the Nearctics and Neotropics ( Figure 6).

DISCUSSION
This study focusing on the sub-genus Typhlodromus (Anthoseius) is the first one proposing combined analyses of the distribution of both species and morphological associated characters within the family Phytoseiidae. It clearly shows the utility of taxonomic data compilation and associated databases in broader aspects than only alpha-taxonomy (Meier and Dikow 2004).
This survey first emphasizes the worldwide distribution of T. (A.) transvaalensis. This species is found in many habitats including stored products (Amitai and Swirski 1978;Corpuz-Raros et al. 1988), and its wide distribution could be explained by the shipment of food from country to country.
The highest number of species of the sub-genus Typhlodromus (Anthoseius) was found in the whole Palaearctic region, whereas the lowest was reported in the Neotropical province. This is quite surprising as this latter province contains the highest number of Phytoseiidae species reported to date (Tixier et al. 2008a). So one can wonder why a high diversity of Typhlodromus (Anthoseius) was not also observed in this area. Is it because species of this sub-genus have not been found yet in this province? In our opinion this hypothesis is weakly sustained, as the number of surveys carried out in the Neotropics is much higher than in other areas (Moraes et al. 2004;Tixier et al. 2008a;Tixier and Kreiter 2009). We could thus suggest other hypotheses as (i) species of this sub-genus did not colonize this province or (ii) have been extinct. Similarly, the number of species of Typhlodromus (Anthoseius) is also low in the Nearctics. The same hypotheses as those previously developed for the Neotropics could also be raised to explain the low number of species reported in the Nearctics.
The most diverse morphological forms of Typhlodromus (Anthoseius) have been observed in the two Palaearctic areas. This could appear quite logical.
Indeed, in provinces where the number of species of Typhlodromus (Anthoseius) was low, the number of morphological forms was also low (e.g.Neotropical and Australasian provinces) and vice versa. However, despite a great number of species reported in the Ethiopian province and in a less extent in the Oriental one, the number of morphological forms is much lower than in the Palaearctic provinces. This could suggest that only some morphological forms succeeded in colonizing these two former provinces, nevertheless with a great success in regards to the occurrence of many species. Other hypotheses could be that these forms have not been found yet or that they would have been extinct.
In the West and East Palaearctic provinces, we also observed rare character states (two setae on the ventrianal shield, short peritreme). The highest number of species and morphological diversity, as well as some rare characters in these latter provinces could suggest that these parts of the world are the centre of origin of the sub-genus. The distribution of the three other genera of the tribe (Typhlodromini) [in which is included Typhlodromus (Anthoseius)] seems to concur to this hypothesis (Moraes et al. 2004;Tixier et al. 2008a). Indeed, all species of the genus Typhloseiulus Chant and McMurtry [same dorsal chaetotaxy as Typhlodromus (Anthoseius)] are reported from the West Palaearctic area; species of the sister sub-genus, Typhlodromus (Typhlodromus) Scheuten, are mainly reported from the Palaearctic province (60 % and 14 % of species from the West and East Palaearctic areas, respectively); and 38% of the species the genus Neoseiulella Muma are endemic to the West Palaearctic region. Furthermore, Kanouh (2010) questioned the polyphyly of this latter genus to explain that 50 % of species are endemic of the Australasian province. However, as high diversity and endemism in the Palaearctic provinces can be due to other factors, i.e. extinctions in the other provinces (Cain 1944;Brown and Lomolino 1998;Humphries and Parenti 1999), additional phylogenetic studies would be thus required to test the hypothesis presently discussed.
Finally, the present study emphasizes high endemism levels in all the provinces considered, even those where only few species were reported (i.e. Neotropics). Organisms can be endemic to a location because they originated in that place and never dispersed but also because they can be extinct in the original area and only survive in the secondary colonized zones (Brown and Lomolino 1998). Biology and history of species of Typhlodromus (Anthoseius) is poorly known, thus it would be highly speculative to try to explain the endemism rates. Our own experience suggests however that species of Typhlodromus (Anthoseius) are rare and when found the number of specimens is low. For instance, 269 species have been reported less than four times, whereas six species (the worldwide ones) have been reported more than 30 times. Finally, the high endemism rates at species level could also be due to an artefact. Indeed, the morphological features that really allow to discriminate between species within the family Phytoseiidae, and as a consequence in the sub-genus Typhlodromus (Anthoseius), are sometimes questionable (Tixier et al. 2003(Tixier et al. , 2006a(Tixier et al. , b, 2008b(Tixier et al. , 2010Okassa et al. 2009Okassa et al. , 2010. We can thus wonder if the number of synonymies which is presently very low (6 %) would not be in reality much higher. Many species described or only reported from one province may have actually been described more than once from another province (under another name). Furthermore, many species have been described based on few specimens thus it is quite difficult to determine a posteriori if this is really a new species or a variant of a known one. Moreover, for some authors it could have been difficult to assess the huge taxonomic information (322 original descriptions in 58 countries and in nearly a dozen languages). To better assess the level of synonymy, different studies on this sub-genus are planned. At first, molecular experiments will be conducted to assess the reliability of some morphological characters presently used for diagnosis; a DNA sequence database will be built to assist diagnosis (La Salle et al. 2009). However, the main difficulty presently encountered is the collection of live material, given the rarity of the species. The second work consists in a compilation of the morphological characters of all the species of this sub-genus in order to construct an electronic polytomous key intended to be freely accessible on the web in order to facilitate the identification of the species of Typhlodromus (Anthoseius) and to avoid the description of species already known. found in a grapevine orchard from Lebanon -Syst. Appl. Acarol., 11: 51-56.