Parioglossus rainfordi

Rui Wang & Richard Winterbottom, 2006, Osteology and phylogeny of Parioglossus (Teleostei, Gobioidei), with a revised key to the species., Zootaxa 1131, pp. 1-32 : 15

Intraspecific Variation of Osteology in P. rainfordi

The structure of the caudal complex, and the shape of the first dorsal fin pterygiophores and of the pectoral fin girdle exhibit considerable intraspecific variation in fishes (Schlueter and Thomerson, 1971; Bruner, 1976; Arratia, 1983; Doyle, 1998). Intraspecific variability may make it unwise to judge a character on the basis of a very small number of specimens (only one or two specimens of some species were available). We examined this variation in one common species of Parioglossus , and use the results as a reference for character selection. Doyle (1998) showed that some characters were inappropriate for use as indicators of phylogenetic relationship in dactyloscopids because of their high intraspecific variability. We found the following characters to be congruent with this limitation: i) within the caudal skeleton, the tips of the spines of vertebra 24 are sometimes bifurcated or trifurcated; ii) the position of the insertion of the posterior second dorsal-fin pterygiophores and posterior anal-fin pterygiophores with respect to the neural and haemal spines may vary; and iii) the length of premaxilla ascending process may be either long or short. These characters are, therefore, deemed unsuitable for the study of phylogeny in Parioglossus . It is important to have some idea of how “robust” a character is for the study of phylogeny before one begins character selection. However, due to a limited sample size and lack of detailed ontogenetic data, sources of the observed variation with P. rainfordi remain speculative. Its remains possible that either some potentially informative characters have been excluded because of overestimated variation, or some potentially variable characters were included because of an underestimated variation.