AN OVERVIEW OF THE DISTRIBUTION OF THE PARABATHYNELLIDAE ( CRUSTACEA , SYNCARIDA BATHYNELLACEA ) ON THE IBERIAN PENINSULA AND BALEARIC

This paper reviews all the knowledge on the presence and distribution of 26 species of the family Parabathynellidae Noodt, 1964 (Crustacea, Syncarida, Bathynellacea) on the Iberian Peninsula and Balearic Islands. The different genera, subgenera and species distributions are subjected to a basic analysis. The presence of these taxa in different subterranean aquatic habitats (caves, springs, wells and interstitial environment) is also discussed. The most sampled habitat was the interstitial environment (45%); the least sampled habitat was springs (5%). The most commonly found genus was Iberobathynella Schminke, 1973 (54%) and the rarest was Guadalopebathynella Camacho & Serban, 1998 (0.7%) All the knowledge on these taxa in the study area, in Europe and in the world is compared and evaluated. More species of the Parabathynellidae live on the Iberian Peninsula and Balearic Islands than in any other part of the world (26 species). Iberobathynella is a highly diversified genus endemic to the Iberian peninsula. Its diversity is comparable to another genus in the order, Hexabathynella Schminke, 1972, which also has 18 described species. However, Hexabathynella has a cosmopolitan distribution.


Introduction
The Order Bathynellacea Chappuis, 1915, is widely distributed on the Iberian Peninsula and the Balearic Islands.This is the area of the World where most species of this crustacean group are known.The two families described in the order, Parabathynellidae Noodt, 1964 andBathynellidae Grobben, 1905, are highly diversified in Portugal and Spain.In the rest of Europe only the Bathynellidae has a similar number of known species.
Twenty-six species of Parabathynellidae are known and a similar number of Bathynellidae to date on the Iberian Peninsula and Balearic Islands, but most of the latter have not yet been described.The Parabathynellidae comprises 18 species of Iberobathynella; one species of Guadalopebathynella; two species of Hexaiberobathynella; two species of Paraiberobathynella Camacho & Serban, 1998; and three species of Hexabathynella Schminke, 1972 (the only cosmopolitan genus in the order Bathynellacea).
The distribution of the Parabathynellidae family in this area is very extensive and covers the whole of the Peninsula and the islands of Mallorca and menorca (Pretus, 1991).Some of the species are found in many different sites, often placed considerably apart, while other species inhabit very limited areas, some even being known from a single location only.Subterranean water sensu lato (i.e.caves: gours, pools, lakes, subterranean rivers and springs; and in unconsolidated sediments: wells and the hyporheic and intersticial realms) is the only habitat where bathynells live.This environment is poorly known on the Iberian Peninsula as well as in Europe and the world.But, despite this, we consider that the current knowledge on the distribution of 26 species in 139 different places, in four habitats, is such that it constitutes a body of data that is of considerable importance and now is the time that it should be revised, updated and compared critically from a faunistic point of view.
It is important to bear in mind that in Europe, apart from the Iberian Peninsula, only two genera of the Parabathynellidae family have been found.One of these, Parabathynella Chappuis, 1926, has only two species, which are widely distributed in France and Central Europe.The other genus, Hexabathynella, which is the only cosmopolitan genus in the order, has five species in Bulgaria and one in Corsica.Given that Parabathynella never crossed the Pyrenees, Hexabathynella has three different species on the Iberian Peninsula, and that as much as four endemic genera are known from this  (Camacho, 1989).Spain.
Table 1 shows the recognized names of taxa and the taxonomic authorities for the Parabathynellidae in the study area.There are 18 species of Iberobathynella (belonging to three subgenera), one species of Guadalopebathynella, two species of Paraiberobathynella Camacho & Serban, 1998, two species of the Hexaiberobathynella genus, and three species of Hexabathynella.
Table 2 shows the world distribution, by continent, of the species of the Parabathynellidae.
Appendix lists the sites where the 26 species of the Parabathynellidae and eleven Iberobathynella sp., one Paraiberobathynella sp. and one Hexabathynella sp. have been found.For each site (139 places in Spain and Portugal) the following data are provided: an identification number, used also in Figures 1 to 4; the province; the country and the UTM coordinates.We also specify the habitat type (cave, spring, well and rivers -interstitial water associated with epigean rivers or streams).

Distribution
The distribution of the 26 species of Parabathynellidae on the Iberian Peninsula & Balearic Islands is shown in detail in Figures 1 to 4.
Each map shows the distribution of a particular genus.The numbers indicate the different places, and the different symbols indicate the different subgenera or species.
Figure 1 shows the 74 localities where the 18 species of Iberobathynella have been found (plus 10 I. sp.localities).Taxa have been divided into 5 groups (Fig 1A ): the Iberobathynella (Iberobathynella) subgenus in the western part of the Iberian Peninsula; the Iberobathynella (Espanobathynella) subgenus in a small area in the North of Spain (Picos de Europa); the Iberobathynella (Asturibathynella) subgenus in the North of the Iberian Peninsula above the Duero basin, plus one species found in Sevilla; Iberobathynella pedroi Camacho (in press c), species  Figure 2 details the 43 localities where the 2 species of the genus Paraiberobathynella have been found.All places are situated on the edge of the Peninsula, from Cantabria to Cádiz, and on the Island of Mallorca.This genus also lives in North Africa (Paraiberobathynella maghrebensis Boutin & Coineau, 1987).
Figure 3 shows the 19 localities of Hexaiberobathynella.Another genus, the monotypic Guadalopebathynella is found in a single locality (70).
Figure 4 shows the distribution of the genus Hexabathynella, with two localities in the North of Portugal (124 and 65), one in the south of Spain (123) and three more in Central Spain.
There are 109 species of Parabathynellidae known in the world (Table 2).Europe is the continent which has been most sampled.This sampling effort has been very unequal over the years and very different in each country.However it can still be said that the some sampling effort has been devoted in France, Spain, Portugal, Slovenia, Italy, Bulgaria, Rumania, Belgium and Germany during the last 70 years.America, both North and South, has been hardly sampled.Few species have been found there, and most new species described are only known from the type locality.The same holds for Asia, Africa, Australia and New Zealand.Most of the genera described worldwide (35) have only been found, to date, in a single country.

Results
Table 2 shows the world distribution of the genera and species of the Parabathynellidae by continent.It can be seem that almost one quarter of all the species known in the world live on the Iberian Peninsula and that of all the genera described, 14% come from Iberian Peninsula.Half of the world genera are African, but the number of African makes up only 25% of the total.In France, only 3 species of this family are known: Paraiberobathynella (Pi.) fagei, which lives in 3 localities close to Perpignan; Parabathynella motasi or stygia, known only from a single locality; in 10 French localities there are specimens as yet unidentified (under study by the author) but which could correspond to Parabathynella; and Hexabathynella knoepfflery, found in Corsica.
If we take into account that the sampling effort in neighbouring France has been similar or even greater in the past than that carried out in Spain in the last 18 years, we can conclude that the diversity, in the number of species, is far superior in the Iberian Peninsula.
In the rest of Europe, which has also been well sampled, only 2 species of Parabathynella, and 5 more, all Bulgarian, of Hexabathynella have been found.None of the other 4 continents can equal the Iberian Peninsula in the number of known species.Africa, which is far bigger that the Iberian Peninsula harbours only 23 known species and the same holds for America (23 species).But the sampling effort in these continents cannot be compared with that carried out in the Iberian Peninsula in the last few years and it is to be expected that when more intensive sampling takes place the figures will go up significantly.
Table 3 and Appendix it show that the genus Iberobathynella is themost common in the study area, being present in 74 sites (Fig. 1).The 18 species belong to three subgenera: Iberobathynella (Iberobathynella) (9 localities, four in Portugal and five in Spain), containing five especies, three being unique to Portugal, one which only lives in Spain, and another found in both countries; the Iberobathynella (Espanobathynella) subgenus inhabits 15 localities, with one species in a single locality, the other two species coexisting in 7 localities and each inhabiting 4 additional localities separately; the Iberobathynella (Asturibathynella) subgenus is found in 45 localities, has the greatest number of species of all the subgenera (nine); four of its species are only found in a single site, one in Portugal, and the other three in Spain; another five species only appear in Spain in 5, 4, 3, 3 and 26 localities respectively; Iberobathynella pedroi (subgenus unknown) has only been found in a single locality in Portugal.The genus Paraiberobathynella occurs in 43 localities (Fig. 2; Table 3): Pi. (Paraiberobathynella) fagei (42 localities), and Pi.(Orihuelabathynella) notenboomi (single locality, number 77), and Pi.sp.found in a single locality (67).
Hexaiberobathynella has been found in 21 localities (Fig. 3; Table 3); one species, Hi. mateusi was found in 20 sites, while the other species, Hi. hortezuelensis is known from a single site only (108).
Hexabathynella has been found in 6 localities (Fig. 4; Table 3); one species, H. minuta, lives in three sites, two in the North of Portugal, and one in the south of Spain.The other two species, H. nicoleiana and H. valdecasasi, are only found in Central Spain, each in a single place.An additional species, H. sp., lives also in Central Spain.
Table 3 shows also the habitat types occupied by the 5 genera and 26 species: rivers (interstitial environment), caves, wells and springs.
Figure 6A shows of the percentage of sampling points per habitat type: 45%-the biggest-for rivers and 5% for springs-the smallest.In these habitats the representation of genera is very unequal, as can be seen in Fig. 6B.In rivers all 5 genera are present, with Paraiberobathynella being the most common, found in 40% of the sampling points) although Iberobathynella is also very common (32%); Guadalopebathynella has only been found once and does not appear in any other habitat.
In caves only 3 genera have been found (neither Guadalopebathynella nor Hexabathynella occur) and here it is the genus Iberobathynella which occurs most frequently (84%); Paraiberobathynella only appears in 13% of the sampling points, and Hexaiberobathynella in 3%.
In wells the same subgenera as in caves are found, but again and as for rivers Paraiberobathy-nella is most common (57%), whereas the least common is Hexaiberobathynella (10%).
Figure 6C shows the percentage of sampling points where each of the 5 genera have been found.Iberobathynella is most common (54% of the total), followed by Paraiberobathynella (31%), whereas the rarest is Guadalopebathynella (0.9%). Figure 6D shows the habitat preference for each genus.Iberobathynella occurs in all habitats, although it is more common in caves (55%).Paraiberobathynella is most common in rivers (53%) and is never found in springs.Hexaiberobathynella appears in all habitats, but most commonly in rivers (80%).Guadalopebathynella and Hexabathynella only live in rivers.
The different species of the genus Iberobathynella frequently coexist (I.(E.) magna and I. (E.) cantabriensis in 7 caves; e.g.see Table 4) while they rarely coexist with species from other genera.Species from the other genera show also little propensity to coexist with other species of their owngenus or of other genera.

Discussion and Conclusion
The subterranean waters of the Iberian Peninsula and the Balearic Islands have been sampled very unequally.There are areas (e.g. the North of Spain) where a great deal of sampling has been carried out, whereas in other (e.g. the karsts of Cuenca and Andalucia) the invested sampling effort has been minimal.There is still a lot of virgin terretory remaining to be explored.As the interstitial waters associated with rivers is  the most easily accessible habitat, it has been the most "intensively" sampled.However the very big subterranean systems are practically unknown from a faunistic viewpoint, especially those reaching great depth (in Spain there are 14 sinkholes more than 1000 m depth, see Puch, 1998) and length (many caves are more than 30 km long).
Nevertheless, and in spite of the big gap of knowledge that still remain on this habitat, batinels have been found in almost all places sampled, and the number of species known to date (26, see Table 4) is the biggest the world around.
The most abundant genus in the study area, Iberobathynella (18 species), is the world most diversified of the Parabathynellidae (only the cosmopolitan genus Hexabathynella embraces a similar number of species).Iberobathynella is found in all habitat types studied, although it is more common in cave waters.
As sampling is intensified and sampling areas are expanded the number of new species found is growing up.This trend affects not only the family Parabathynellidae, but also the Bathynellidae, which also appears in almost every subterranean habitat sampled (data still unpublished).

Fig. 1 -
Fig. 1-Distribution of the genus Iberobathynella on the Iberian Peninsula.a) Iberian Peninsula and b) detail of Cantabric region, the area with the highest density of sampling points.Each number corresponds to a sampling site (see Appendix).Fig. 1-Distribución del género Iberobathynella en la Península Ibérica.a) Península Ibérica completa y b) detalle de la region Cantábrica, donde se da la mayor densidad de puntos de muestre.Los números corresponden a las localidades del Apéndice.

Fig. 2 -
Fig. 2-Distribution of the species of the genus Paraiberobathynella of the Iberian Peninsula and the Balearic Islands.Each number corresponds to a sampling site (see Appendix).

Fig. 3 -
Fig. 3-Distribution of the Hexaiberobathynella and Guadalopebathynella species of the Iberian Peninsula.Each number corresponds to a sampling site (see Appendix).

Fig. 5 .
Fig. 5.-Number of genera and species of the world Parabathynellidae.
Fig. 6.-A) Number of locations sampled per habitat type as a percentage of the total.B) Number of samples per habitat rendering each genus.C) Number of points sampled rendering each genus as a percentage of the total.D) Number of samples containing each genus per habitat.Fig.6.-A) Distribucion del número de puntos de muestreo en los medios acuáticos subterráneos considerados, en %.B) Reparto de géneros por medios.C) Número de puntos de muestreo en que se ha encontrado cada género, en % y D) reparto de medios por géneros.

Table 1 .
-Recognized names of taxa and corresponding taxonomic authories for all members of the Family Parabathynellidae of the Iberian Peninsula and Balearic Islands.Tabla 1.-Nombres y autorías taxonómicas de todos los taxa de la familia Parabathynellidae encontrados en la Península Ibérica e Islas Baleares.

Table 3 .
-Number of localities and habitat types where the different taxa of Parabathynellidae family are found on the Iberian Peninsula and Balearic Islands.P= Portugal and S= Spain Tabla 3.-Resumen del número de localidades y del número de habitat en que aparecen los diferentes taxa de la familia Parabathynellidae en la Península Ibérica y las Islas Baleares.*: P= Portugal and S= España.