O. G. Dely szerk.: Vertebrata Hungarica 21. (Budapest, 1982)

Berger, L., Uzell, Th. ; Hotz, H.: Crossing experiments between some Western Palearctic species of water frogs (Salientia: Ranidae) 33-46. o.

rldtbund

a) is passed to all gametes. Its hybridity Is restored in the next generation when these gametes are combined with gametes of the parental species of which the genomes were excluded. Several papers published in the last decade discuss the systematic status of water frogs of southern Europe and northern Africa. Italian water frogs south of the Po Valley, morphologically distinct from the Central European taxa, can be divided into two forms (HOTZ 1974, UZZELL & HOTZ 1979).One of them (the "Italian non-hybrid") shares many electrophoretic markers with R. lessona

e, while the other (the "Italian hybrid") is highly heterozygous, having both lessonae-like and ridlbund

a-like electrophoretic markers; these hybridogenetic hybrid lineages pass rldlbund

a genomes hemlclonally to gametes (UZZELL & HOTZ 1979). Electrophoretic comparisons of oocytes and testes with somatic tissues confirm that the Italian hybrid is hybridogenetic (TUNNER 1980, UZZELL in press; HOTZ unpublished). These two taxa thus form a hybridogenetic system analogous to R. lessona

e and R. esculent

a in Central Europe (L-E system; UZZELL & BERGER 1975). In the Iberian peninsula and in southern France lives R. rldibunda perez

i Seoane, 1885. That this is a distinct species was suggested by HOTZ (1974) and confirmed by GRAF, KARCH & MOREILLON (1977), who demonstrated electrophoretlcally that R. perez

i and R. rldibunda hybridize, producing hybridogenetic hybrid lineages passing the rldibund

a genome to gametes. These hybrids are widespread within the range of R. perez

i (UZZELL & TUNNER, in press; UZZELL & HOTZ, unpublished) and again form a population system analogous to the L-E system. Still less well known are the water frogs of northern Africa, although HEMMER, KONRAD & BACHMANN (1980) proposed that there are two species as well as many trlplold interspecific hybrids. So far these taxa are distinguished only by the electrophoretic phenotypes for serum albumin. The present paper discusses the relationships of the Iberian and Italian peninsula forms on the basis of crosses between them and the Central European forms of water frogs. MATERIAL AND METHOD Individuals of Rana peréz

i were caught In April 1979 In southern Portugal, Algarve coast, at the airport of Alvor near Portlmao by M.F. BROGGI (Vaduz) and in May 1981 in southern France near Saintes Maries de la Mer, Camargue, Bouches-du-Rhone. Samples of the two Italian taxa were collected in April 1979 In Sicily on the Plana de Catania, about 12 km SW Catania. They were transported to Poland In May 1979 and May 1981, mostly as Immature frogs. Polish frogs were collected near Poznaá: R. lessona

e In Naramowice suburb, R. rldlbund

a in Malta suburb, R. esculent

a in Turew (40 km S Poznaá), parents of the F^ Rana esculent

a female (RL) were caught in Naramowice suburb In 1963. The Sicilian, Portuguese and French frogs were Identified as hybrids or non-hybrids by electrophoretic examination of several enzymes in the digits that were removed to mark them individually. The frogs were put Into an outdoor rearing area. Between 1979 and 1981 they were crossed with Polish frogs, and with the Fi R. rldibund

a female from Turkey (her mother was caught In Diizce at the seaside of the Black Sea, and her father In Kayseri, Cezarea, 1963). Thirty pairings between 28 females and 22 males produced progeny (Table 1). Six pairs were crossed artificially (cf. BERGER 1967); two pairs (crosses 14,28) laid eggs after pituitary injections (cf. RUGH 1934); some pairs laid eggs spontaneously in aquaria. All these frogs were tabulated with their own marked numbers, as a rule. The other frogs which mated and spawned spontaneously in basins received no number because we were not sure to which pair the progeny belonged. Polish frogs were tabulated without any number. Progeny mothered by the same female and two males received letters a and b. The eggs of each female were examined carefully; some from each female were put into dishes with water for development, water was changed frequently. At stage 25 (cf. LIMBAUGH & VOLPE 1957), all tadpoles were counted; some of them were saved for further development. Although the tadpoles of some pairs developed in large aquaria and outdoor basins, those destined for detailed observation developed in aquaria holding 1.6-5 liter (four tadpoles per liter); these were placed in a sunny room (Table 1). The water was changed daily or every other day. All tadpoles were fed with the same food: pureed peas, yolk of hard-cooked eggs, boiled lettuce and powdered nettle (cf. BERGER & PNIEWSKI 1981). Eruption of the front legs was taken as the beginning of metamorphosis. Immediately after completing transformation, body length snout-to-