DIVERSITY AND DISTRIBUTION OF TARDIGRADES (BILATERIA, TARDIGRADA) FROM THE IBERIAN PENINSULA, BALEARIC ISLANDS AND CHAFARINAS ISLANDS

Bibliographical information on the Tardigrada from Iberian Peninsula, Balearic Islands and Chafarinas Islands is compiled herein. 118 species are listed from the studied area. The first records of six Tardigrada species, Dactylobiotus parthenogeneticus, Dactylobiotus selenicus, Murrayon dianeae, Diphascon (Diphascon) nodulosum (first time in Europe), Diphascon (Diphascon) pingue and Isohypsibius marcellinoi that had not previously been found in the area are included. Bibliography data are analysed. After the analysis, it is concluded that more intensive, extensive and within more diverse habitats sampling effort should significantly increase the knowledge of tardigrade diversity in the studied area.


Introduction
Tardigrades are micrometazoans that can be found world-wide (McInnes, 1994;Nelson & Marley, 2000), in many types of habitats (aquatic and terrestrial) within a film of water (Ramazzotti & Maucci, 1983;Nelson, 1995).They are specially interesting for their capacity to enter in criptobiosis (Crowe, 1975;Nelson, 1995), with posible future applications in biomedicine (Crowe & Crowe, 2000).Another important point is that the phylogenetic position of the Tardigrada gives rise to controversy, depending on whether morphological characters (Nelson, 1982;Nielsen, 1995) or molecular characters (Garey et al., 1996;Giribet et al., 1996;Garey et al., 1999) are studied.Nowadays, it seems that preserving genetic dissimilarity, based on phylogenetic information, is often of a higher conservation priority (Humphries et al., 1995;Hartvingsen, 2001;Swingland, 2001).Although conservation based on ecosystem and landscape approaches might be better, a singlespecies approach may still be appropriate as a first order conservation tool (Kieser, 1993).Therefore, we need the studied group's complete taxonomical information, up-to-date check lists, species diversity studies, relative abundances, corology, etc. to define the phylogeny robustly and, from that, to infer its biodiversity.All of this information, and even more basic information, are incomplete in the Tardigrada phylum.
Tardigrade species description, as it is the case with many other invertebrate groups, accelerated during XX century, along with the growth in the number of researchers involved in its investigation.Tardigrade researches in Iberian Peninsula began in 1911 (Madrid Moreno, 1911), 138 years after the discovery of Tardigrada phylum in 1773 (Goeze, 1773).In the Iberian Peninsula, tardigrade studies are mainly one-off descriptions of new taxa, while in other countries tardigrade researchers work other than with the description of new taxa, with the biology and the ecology of the group.
The main objective of the present work is to compile and up-date the entire body of tardigrade information (species diversity, corology, autecology) for the Iberian Peninsula, the Balearic Islands and Chafarinas Islands, and to show how a small sampling effort (in many types of habitats) could greatly advance the knowledge of Iberian tardigrades, as one may infer from the bibliographic data.
These data are completed with information from new material collected by Dr. A. I. Camacho from groundwater (interstitial environments and caves) from Cantabria, Jaén and Madrid (North, South and Centre of Spain), and from stratified sampling (by the author) of leaf-litter, rock mosses, trunk lichens and mosses, and freshwater algae from different points in the province of Madrid (centre of Spain).In addition to the customary habitats (with respect to Tardigrada phylum) such as leaf-litter, mosses, and lichens from different substratums as: trunks and rocks; we also sampled such unusual habitats as interstitial ones associated with epigean streams or freshwaters algae, and habitats not previously sampled in the Iberian Peninsula (with respect to Tardigrada phylum), like interstitial habitats associated with subterranean rivers or gours in caves.III."X" marks new localities where have been found new tardigrade records for the Iberian Peninsula, the Balearic Islands and Chafarinas Islands.Region "A" includes next localities: 120b, 137,138,153,159,169,170,172,173,177,183,184,196,206,207,213,216,222,237.El número de identificación de las localidades se corresponde con el de la Tabla III.Hemos marcado con una "X" las nuevas localidades de la Península Ibérica, Islas Baleares e Islas Chafarinas donde hemos encontrado tardígrados.La región "A" incluye las siguientes localidades: 120b, 137, 138, 153,159, 169, 170, 172, 173, 177, 183, 184, 196, 206, 207, 213, 216, 222, 237.Table II.-IberianTardigrada species classified by class, order, family, genus and species.This table contains the following information: Tardigrada species names, supraspecific categories, synonymies, number of localities (corresponding to that in Table III and Fig. 1) in the Iberian Peninsula, the Balearic Islands and Chafarinas Islands, habitats-substratums where found and the first published record in the Iberian Peninsula per each species.Marked with a box new records for Iberian Peninsula, the Balearic Islands and Chafarinas Islands (inside brackets, number of specimens found).M= moss, L= lichen, H= leaf-litter, Hep= hepatic, R= rock, E= soil, Ac= freshwater, Ch= pool, Es= pond, TA= water tank, SM= marine sediment, AM= marine algae, Cirr= barnacle, ISR= interstitial habitats from subterranean rivers, ICR= interstitial habitats from cave rivers.*= habitat-substratum not specified in article.

Results
There are 737 works from all over the World on tardigrades, based on information from Zoological Record.Eighteen scientists elaborated 34 works on the Iberian Peninsula, Balearic Islands and Chafarinas Islands, over a period of 85 years.These articles have described one new genus to science, 10 species and 2 subspecies; only 6 of these works deal with marine tardigrades (Table I and II).
Table II presents tardigrade species found in the Iberian Peninsula, the Balearic Islands and Chafarinas Islands, ordered by class, order, family, genus and species.We have included information about synonymies found within these species, an identification number of localities where each species was found (Table III, Fig. 1), habitat-substratums sampled, article references, and where each species was cited for first time in the Iberian Peninsula.
In the bibliography dealing with the studied area, I found 112 species (in Table II District (in Portugal) or Province (in Spain).I have included identification locality numbers (which correspond to those on Fig. 1), UTM coordinates (when available and as precise as it was possible), number of registers (a register correspond to a record that differs from any other in at least one information field: taxonomical, geographical or/and autecological; it can offer a clue about sampling effort), number of species per locality and type of habitat-substratums studied in each locality where tardigrades occur.
Tardigrades have been found in 228 localities in the studied area (Table III); one is in Andorra, another is in Gibraltar (U.K.), 126 in Portugal and 100 in Spain.On Figure 1 a black point indicates each studied locality where tardigrades occur; each black point is numbered with the number assigned to each locality in Table III.It seems that there is a major concentration of points in Portugal, specially in the Northwest (Fig. 1), while in Spain the points are sparse, but become a bit denser in the Pyrenees and in the centre of Spain (mainly in Madrid).
In Table IV we show world-wide taxonomic category information on tardigrades found in the studied area.Section A shows the number of classes, orders, families, genera and species in the entire World and in the Iberian Peninsula; also included percentage of world species found in the Iberian Peninsula for each taxonomic category.This section also displays the number of genera and species found in Portugal and in Spain, genera and species that occur only in Spain or in Portugal and percentages according to world-wide information.Section B, displays number and percentage of species per family and per genera according to world-wide information, in the Iberian Peninsula and in the rest of the world.
We can observe that the world-wide pattern is repeated in the Iberian Peninsula.The world's most diverse families (Table IV), in species and genus number, that are also found in the Iberian Peninsula, are the most diverse families there too (i.e., for Hypsibiidae, 43% of genera and 11% of species occur in the Iberian Peninsula; Table IV).With reference to species number in the generea, the world's most diverse genera, that are also found in the Iberian Peninsula are also the most diverse genera there (Table IV).
Table V displays p values and Spearman correlation coefficients and Table VI p values from Kruskal-Wallis analysis and indicates the variables with the highest values for continuous variables analyzed.Two parallel analysis have been made, one with data collected from all habitat-substratums sampled in the Iberian Peninsula where tardigrades were found (Tables V and VIA), and another analysis with data only from mosses (Tables V and  VIB), collected uniformly in points sampled in the Iberian Peninsula.Spearman correlation coefficients are qualitatively equal (always pisitive correlations and similar magnitudes), but vaules from analysis with mosses only are lower than those carried out over all habitats-substratums.
New records found in our samplings in the Iberian Peninsula are presented in Table II, which specifies class, order, family and genus of each species found.Synonymies found for each new species, identification number that corresponds with the numerical order on Table III and Figure 1 (new localities sampled in Iberian Peninsula, mainly from centre of Spain, are marked on Figure 1 with an "X"), UTM coordinates, habitat-substratums analyzed and number of specimens found for each species.New records for the Iberian Peninsula are: Dactylobiotus parthenogeneticus, Dactylobiotus selenicus, Murrayon dianeae, Diphascon (Diphascon) nodulosum (first record in Europe), Diphascon (Diphascon) pingue and Isohypsibius marcellinoi.These results increase the number of Tardigrada phylum species found in the Iberian Peninsula to 118, 5% more than the specific diversity previously known in the Iberian Peninsula.
There are broadly distributed limnoterrestrial species (large number of registers per species involving a large number of habitat-substratums and localities; Table V), appearing in Portugal and Spain in a large number of localities (Table II and III, Fig. 1), such as Macrobiotus hufelandi (130 localities) or Milnesium tardigradum (53 localities).The majority of these species are considered to be cosmopolitan by McInnes, in the revision made in 1994.However, there are other species with a more restricted distribution, appearing only in one locality (Table II and III; Fig. 1).The majority of species that are more or less widely distributed in the Iberian Peninsula appear in many of the habitat-substratums studied (i.e., Macrobiotus hufelandi) (Table II) with a high correlation coefficient (+0.81;Table V); but species that occur in many of the habitat-substratums studied do not (c) Sociedad de Amigos del Museo Nacional de Ciencias Naturales y Consejo Superior de Investigaciones Científicas Licencia Creative Commons 3.0 España (by-nc) http://graellsia.revistas.csic.esTable IV.-(A)Absolute number and percentage of limnoterrestrial species with respect to world-wide distribution of each Tardigrada taxonomy category in the World and in the Iberian Peninsula (IP).* = percentage with respect to world information; + = percentage with respect to Iberian Peninsula information; # = genus and species that appear only in Spain or in Portugal.(B) In the first part of the Table (left), number (No) and percentage (%) of limnoterrestrial genus and species (spp) with respect to World information in each of Tardigrada families found in the Iberian Peninsula (IP).In second part of the Table (right), number (No) and percentage (%) of limnoterrestrial species (spp) with respect to World information in each of the Tardigrada genus found in the Iberian Peninsula.
Mosses plus lichens are the habitats with the highest tardigrade species specific and genera diversity (Table II, VIA and B), but the greatest extensive sampling effort (number of localities) have been made too in these habitats (Tables VIA  and B).Similar situation is in leaf-litter (Table VIA).While considerable sampling effort has been directed towards certain habitats (such as mosses; Table VIB), others have been greatly overlooked and a lot of habitats in the Iberian Peninsula where tardigrades can live have been not sampled at all (i.e., interstitial habitats in caves; Table II) or else insufficiently (marine habitats that have high species diversity without a great sampling effort associated), as demonstrated by new sampling (Table III).These habitats seem to have new tardigrade species to add to the previously known Iberian Tardigrada diversity (Table II).While there are species restricted to few habitat-substratums, this does not mean that a specific species-habitat relationship exists.It could be that in some localities few or rare habitat-substratums were sampled and the rela-tionship would then be between locality-species instead of habitat-species.To verify the existence of a true species-habitat relationship, further studies are required.
With reference to localities, of the few (Tables II  and III) populated by 10 or more species, one is in Andorra (number of locality: 29), one in Spain (13) and 7 in Portugal (43,25,139,40,9,107,114), with the majority in Northwest Portugal (Fig. 1).These localities are characterised by the highest number of registers and number of sampled habitatsubstratums (Table V).The results for genera are the same (Table V).The greatest sampling effort has been made in Portugal, both in locality number (55.3% from total) and in register number (68.1% from a total of 1020 registers) (Table III).Nevertheless, the highest percentages of limnoterrestrial species and genera in the Iberian Peninsula were found in Spain (78.3% and 82.6%, respectively) (Table II).