GEOGRAPHIC-VARIATION IN ALLOZYMES OF POPULATIONS OF SALAMANDRA-SALAMANDRA (AMPHIBIA, URODELA) EXHIBITING DISTINCT REPRODUCTIVE MODES

The populations of the urodele Salamandra salamandra in the Northern I berian Peninsula exhibit very different coloration patterns and a rema rkable range in reproductive modes (from giving birth to a large numbe r of aquatic larvae to a parturition event of just a few fully metamor phosed, i.e. terrestrial, offspring). Electrophoretic study of geograp hic variation in allozymes shows that this extraordinary diversity, pa rticularly in reproductive modes, is not accompanied by a genetic diff erentiation of similar magnitude. All the populations sampled along a transect crossing the Northern part of the Iberian Peninsula and encom passing the various reproductive strategies, as previously described, can be ascribed to a single species, because of small interpopulationa l genetic distances (ranging D-Nei from 0.05 to 0.199) and absence of fixed (diagnostic) alleles. A variety of phenetic and cladistic method s were used to elucidate the relationship among populations, based on allozyme data. These methods defined two well corroborated clusters: t he first contains populations of salamanders with a blotched dorsal co loration pattern and characterized by parturition of aquatic larvae; t he second group is composed of populations exhibiting a striped dorsal coloration pattern, smaller adult body size, and giving birth to full y metamorphosed terrestrial offspring. The latter group also encompass es some populations where mixed parturition events, which include both larvae and metamorphosed offspring, which have been recorded (Dopazo and Alberch, 1994). The absence of a correlation between genetic and g eographic distance suggests that the mode of differentiation of the sp ecies is based on at least two successive events of isolation, radiati on, and secondary contact between populations. Furthermore, the validi ty of the described ''subspecies'' is questioned by our data, which po int out the need for a detailed systematic study of Salamandra from a global perspective. ''Viviparity'', here meaning giving birth to fully metamorphosed offspring, originated once and occurs as intraspecific, and even as intrapopulational variation. Thus, we confirm a system wh ere a major evolutionary innovation -the acquisition of independence f rom the aquatic media in the primitive amphibian complex life cycle-, can be studied at the microevolutionary, i.e., intra- and inter-popula tional level.