SOIL AND FRESHWATER NEMATODES OF THE IBERIAN FAUNA: A SYNTHESIS

The first available compilation of Iberian soil and freshwater nematodes is presented in this paper. The inventory is currently made up of 981 species belonging to 236 genera, 77 families and 12 orders. Data of the Iberian nematode fauna are compared with other components of the Iberian biota, as well as the nematode fauna of other geographical regions. Quantitative and qualitative aspects of the nematode inventory are analyzed and discussed, paying special attention to the kind of information available for each species, and concluding that practically one-third of Iberian species are deficiently characterized and need further study. Endemicity of Iberian species is also considered: 143 species, 14.6% of the total, are restricted (in their distribution) to the Iberian geography, most of them being members of the orders Dorylaimida (87) and Tylenchida (29), which are also the most diversified nematode taxa. Practical or applied interest of knowledge of the Iberian nematode fauna is commented and supported with examples and recent contributions. Finally, an alphabetical list of the species, ordered by specific name, is provided.


Introduction
The biodiversity of any territory is one of its main distinctive features and its characterization serves fundamental and applied purposes.The biota of soil and freshwater sediments has hitherto received little attention, although it plays an important role in their respective food webs.Nematodes (phylum Nematoda or Nemata) are a highly diversified zoological group, which displays a wide trophic spectrum and shows perhaps the widest geographical spread among animals.Moreover, they are a major component of living communities inhabiting soils and freshwater bodies.
Regional continental nematode faunas practically have not been studied, and little information is available on their distribution patterns as well as on processes behind them.Soil and freshwater Iberian nematodes have been recorded throughout the last five decades, starting with the work of Gadea (1952), the pioneering Spanish nematologist.In the following decades, other authors made relevant contributions in the field: Jiménez-Millán and his collaborators (Arias, Bello, Romero) and Tobar-Jiménez from the sixties; Jiménez-Guirado and Palomo from the seventies; de Andrés, Castillo, Hernández, Navas, Nombela, Ocaña and Peña-Santiago in the eighties; and several young nematologists (Abolafia, Armendáriz, Escuer, Galeano, Liébanas, Talavera) in the nineties.
The aim of the present contribution is to update the inventory of Iberian nematode species and provide a general panorama of our current knowledge (of them) as well to discuss its fundamental and applied interest.

Updating the inventory
This work has been undertaken to compile information recently available in specialized literature, to include new records or those data that were overlooked, and/or to correct some noted errors.
Twenty nine (six dorylaimid, 21 rhabditid, two tylenchid and one triplonchid) species were added to the Iberian Fauna catalogue (Appendix 1), as well as many new records of other species previously reported [see also Díez-Rojo et al. (2006) for a compilation of plant-parasitic species recorded in Castilla y León region].Nine (one dorylaimid, seven rhabditid and one triplonchid) species are tentatively considered to be Iberian endemisms since their current distribution is restricted to peninsular Spain and Portugal.
The new information is presented below, following a general scheme identical to that used in previous compendia.

Characterizing the nematode Iberian fauna
HOW MANY SPECIES?
Table 1 summarizes data from previous compendia on nematode Iberian fauna as well as the new records provided here, representing the 'state of the art' at the end of 2005.According to this updated information, 981 (soil and freshwater) nematode species belonging to 236 genera and 77 families have hitherto been reported from the Iberian geography.Two major orders, Dorylaimida and Tylenchida, each make up almost one-third of the Iberian fauna, having more than 60 genera and 300 species.Rhabditida is a medium sized order, with 40 genera and 100 species; and the rest are minor orders, being represented by less than 20 genera and less than 50 species.
Although these figures should be taken with caution (see below), they are interesting per se for comparative purposes.For instance, the number of nematode species is about one-sixth that of vascular plants (5597; see Smythies, 1984Smythies, -1986;;Castroviejo, 2002), one-fourth of butterflies (4243; see Vives-Moreno, 1994;Ortuño, 2002), and very close to the number of vertebrates (1068; see Ramos et al., 2002).
Unfortunately, available information for other territories or regions is very poor, and no detailed comparative study can be carried out.
Table 2 provides a compilation of available data from Europe (Bongers, 2006), the Netherlands (Bongers, 1988) and Hungary (Andrássy, 2005).Bongers (2006) has inventoried 115 families, 483 genera and 2952 nematode species in the 'Fauna Europea' project.Thus, Iberian nematodes currently represent about two-thirds (67%), one half (52%) and one-third (33%), respectively, of the total European fauna.On the other hand, the number of Iberian species is higher than those found in the Netherlands (635) and Hungary (720), two countries whose extension is less than that of the Iberian region but which have a longer tradition of nematological studies.

QUALITY OF AVAILABLE INFORMATION
Appendix 2 provides the complete list of Iberian species ordered by specific epithet, with indication of the order to which they belong.Nevertheless, data from both Table 1 and Appendix 2 should be taken and managed with some caution because the quality of information varies depending on the taxon considered.We have (tentatively) classified/divided Iberian species into four groups on the base of type of data available about them.
(1) Species whose presence in Iberian soils or freshwater bodies needs to be confirmed: only occasional (generally old) records are known, usually obtained as results of general surveys other than monographic studies on particular taxa; identification presents serious doubts (for instance, Helicotylenchus cf.rohtangus) and/or the species in question is more typical of other biogeographical regions.(2) Species which have been studied under a taxonomical point of view (often with available description, measurements, etc.) but whose information does not fit that previously known for the same species, and/or that were identified many years ago, and have not been found later.
(3) Cosmopolitan or widely distributed species which have never been studied under a taxonomical point of view, but whose presence in the Iberian geography is confirmed because they have been reported repeatedly, and/or identified in monographic studies although information concerning their morphology and morphometry was never published.This is the case of a good number of Xiphinema species.(4) Confirmed and well characterized Iberian species, whose populations were the object of specialized published papers or monographies, and whose identification does not present reasonable doubts.This occurs with species of the genera Dorylaimoides, Tylencholaimellus, Amplimerlinius, many criconematids, etc.
The corresponding status of every species is indicated (see figures between brackets) in Appendix 2, while Table 3 summarizes information concerning each nematode order.Hardly more than half of Iberian nematode species (508, 51.8%) are well studied and characterized, and practically onethird (262+57, 32.5%) of the total needs additional information.The situation, however, is not identical in all taxa.Three (minor) orders, Chromadorida, Mononchida or Plectida, are known best, with their average being quite higher than 3.0; most orders display values within the range 2.5-3.0, and this means that their status is not satisfactory; only the order Enoplida shows a very deficient panorama, although it is a minor order in number of species.In conclusion, it is evident that additional studies are needed and should be undertaken to complete our knowledge of these taxa.

LEVEL OF ENDEMICITY
Table 1 shows the number of soil and freshwater nematode endemisms currently registered in the Iberian inventory.The corresponding species are marked with an asterisk (between brackets) in PEÑA-SANTIAGO, ABOLAFIA, GUERRERO, LIÉBANAS & PERALTA Table 1.-Quantitative information on Iberian (soil and freshwater) nematode taxa, with special reference to (tentative) endemic species (Percentages in brackets).

Nº taxa
Families Genera Species Endemic species 1 Endemicity (%) Appendix 2. It has been mentioned above that the inventory is tentative or provisional, and this is particularly so concerning endemisms.At least two principal causes contribute to this provisionality.On the one hand, the nematode fauna of the Mediterranean region has not been studied in detail yet -perhaps with the exception of Italy (including its peninsular territory and some of the islands, for instance Sicily)-and it is very likely that at least part of the Iberian endemisms might be recorded in other geographical areas, a fact that should entail a decrease in the number of Iberian endemic species.On the other hand, the highest number of endemisms appears in the most important (diversified) nematode orders, mainly dorylaims (order Dorylaimida) and tylenchs (order Tylenchida), which are those that have received more attention, that is, there is a logical correlation between sampling and/or 'faunistic' effort and results obtained.In this sense, we must take into account that the Iberian territory has not been covered regularly with general surveys, and that new taxa will be recorded and/or described in the future, some of them certainly new Iberian endemisms.
No study has been published up to now concerning endemic soil and freshwater nematodes from other natural regions, and this makes it impossible to analyze the case of the Iberian Peninsula from a comparative point of view.APPLIED ASPECTS OF THE IBERIAN NEMATODE FAUNA Soil and freshwater nematodes have been studied in the Iberian region not only for basic or fundamental purposes but also to accomplish practical or applied aims.Free-living forms are dominant in both natural and cultivated terrestrial areas and, of course, in freshwater bodies, and the faunistic composition of their respective taxocoenoses is useful to assess the 'health' of the corresponding habitat.But plant parasitic?species are also frequent, and particularly important in agroecosystems where they may cause severe damages.

FREE-LIVING FORMS AND THEIR INTEREST
Iberian nematode species have been used to test and monitorize the quality of both soil and freshwater habitats.Ocaña & Picazo (1991) studied the response of the nematode community to organic pollution in the Monachil river (Granada), and found significant correlations between among species distribution and a series of physico-chemical parameters, concluding that a group of species are indicators of organic water pollution.
Members of the orders Dorylaimida and Mononchida -two of the best known Iberian nematode taxa-have been used to evaluate the impact of the perturbation caused by the mining accident occurred in the Guadiamar river basin (Seville) in 1998 and to monitorize the re-colonization process (Peña-Santiago et al., 2003, 2005) in the soils of this area.Two well defined patterns, one spatial and another temporal, were identified, and the interest of these nematode orders as useful bioindicators was corroborated.

PLANT PARASITES
Many nematode species feed on vascular plants, producing a variable range of damages.
Among the members of the order Aphelenchida reported from the Iberian Peninsula, fourteen species of the genus Bursaphelenchus, including the pine wilt desease nematode (B.xylophilus), have been reported from the Iberian peninsula (Arias et al., 2004;Penas et al., 2004) in association with pine and other conifer forests.There are also eleven species of the genus Aphelenchoides, some of them showing pathogenicity on several crops such as rice, ornamental plants and strawberry (Escuer & Bello, 2000).
The order Tylenchida provides the highest number of plant parasitic neamatodes.The genus Meloidogyne (root-knot nematodes), one of the most damaging agricultural pests, is represented in the Iberian fauna by eleven species, three of which (M. arenaria, M. javanica and M. incognita) are particularly ubiquitous and exhibit an extreme polyphagy (Flores- Romero & Navas, 2005).Thirteen Heterodera species (cyst nematodes) have been recorded from Iberian soils, mainly in association with cereals and pulses (Romero et al., 1973).Also thirteen species of root lesion nematodes of the genus Pratylenchus have been found parasitizing a wide range of host plants, P. penetrans, P. pratensis, P. vulnus and P. thornei being among the most fre- The dorylaimid family Longidoridae is very highly diversified in the Iberian region (see Arias, 1979), with 81 species belonging to three genera: Longidorus (20 spp.), Paralongidorus (3 spp.) and Xiphinema (58 spp.).Longidorid nematodes are ectoparasites, and some species are able to transmit plant viruses.Among the 18 longidorid species considered by Taylor & Brown (1997) to be virus vectors, there seven species reported from the Iberian geography: Longidorus attenuatus, L. elongatus, L. macrosoma, Xiphinema diversicaudatum, X. index, X. italiae and X. rivesi.
Finally, the order Triplonchida is represented with 15 species (López-Pérez et al., 2001) in two genera: Paratrichodorus (6 spp.) and Trichodorus (9 spp.).Like longidorids, trichodorid nematodes are ectoparasites and, in some cases, virus vectors; in fact, Decraemer (1995) has provided a list of trichodorid species which are certainly virus vectors, and eight out of the 15 Iberian species (four Paratrichodorus and four Trichodorus species) are included in this list.QUARANTINE SPECIES Bello et al. (2005) have very recently provided a review of the geographical distribution in Spain of quarantine nematodes regulated by the European Union (EH Directive 2000/29/EC and/or the EPPO quarantine lists), concluding that only four species (Ditylenchus dipsaci, Globodera pallida, Globodera rostochiensis and Xiphinema rivesi occur in peninsular Spain, and that extensive surveys are needed to delimit the spread of the regulated nematodes and to detect the introduction of exotic quarantine species.

Table 2 .
-Data on the Iberian nematode fauna compared to those from Europe, Hungary and the Netherlands.Tabla 2.-Táxones de la fauna de nematodos ibéricos comparados con los de Europe, Hungría y Holanda.

Table 3 .
-Number of Iberian nematode species with an evaluation of the quality of information available about them.Tabla 3.-Número de species de nematodos ibéricos con estimación de la calidad de la información disponible sobre ellos.