Electrophoretic Comparisons between Allopatric Populations of Five Australian Pseudomyine Rodents (Muridae)

Abstract

Allopatric populations of the pseudomyine rodents Pseudomys albocinereus, P. delicatulus, the P. nanus-P. gracilicaudatus complex, Zyzomys argurus and Mesembriomys gouldi were surveyed for electrophoretic variability of 14-17 red cell and plasma proteins. Few or no electrophoretic differences were found to parallel the chromosomal differences between populations of P. delicatulus, Z. argurus, and M. gouldi. Populations of the P. nanus-P. gracilicaudatus complex, however, fell into two groups defined both chromosomally and electrophoretically. The western form (P. nanus) extends from Western Australia into the Northern Territory whilst the eastern form (P. gracilicaudatus) occurs only along the east coast of Queensland and New South Wales. The biochemical differentiation between South Australian, Western Australian mainland and Bernier Island P. albocinereus parallels the chromosomal, morphological and breeding data, all of which indicate that the Western Australian mainland and Bernier Island forms belong to one species (P. albocinereus), whilst the South Australian form represents a distinct biological species (P. apodemoides).The relationship between electrophoretic variation and the biological species concept was explored using data from Drosophila and rodents. It was concluded that if two allopatric populations possess 'fixed' electrophoretic differences at at least 15 % of their loci, then it is highly probable that they belong to different biological species. However, populations that differ by less than 15 % of their loci need not necessarily belong to the same species especially if chromosomally they differ by several Robertsonian rearrangements.

Electrophoretic Resolution of Species Boundaries in Australian Microchiroptera. II. The Pipistrellus Group (Chiroptera: Vespertilionidae)

“…In the present study, for example, even across large geographic distances, P. westralis showed a maximum of 6% fixed differences, P. adamsi 3% fixed differences, and F. tasmaniensis zero fixed differences (between Victoria and Tasmania). Such results are typical of the level of genetic divergence found between geographically isolated populations of the same species (Baverstock et al 1977(Baverstock et al , 1980(Baverstock et al , 1983a(Baverstock et al , 1983bKitchener et al 1984). The observation that F. mckenziei and F. tasmaniensis have 22-25% fixed differences at 36 loci strongly supports their recognition as distinct species.…”

“…However, the extent of genetic divergence between them is well beyond that which we would normally consider characteristic of populations of the same species. For mammals, and indeed most animals, the extent of divergence between populations of the same species seldom exceeds 10% fixed differences, and never more than 15% (Baverstock et al 1977;Thorpe 1983;Richardson et al 1986; although see Patton 1981 for a possible exception). In the present study, for example, even across large geographic distances, P. westralis showed a maximum of 6% fixed differences, P. adamsi 3% fixed differences, and F. tasmaniensis zero fixed differences (between Victoria and Tasmania).…”

Delimiting species: a Renaissance issue in systematic biology

“…Specifically, he argued that groups of samples differing by a NEI GENETIC DISTANCE (Nei D) [30] of 0.15 or higher should be considered distinct species. Highton recognized that this value was arbitrary, but cited an earlier study [31] suggesting that allopatric populations differing by fixed alternative alleles at 15% of their loci were probably different 'biological species'. Highton also noted that most (97%) pairwise Nei identity (Nei I) between well defined species of vertebrates are , 0.…”

Allozyme genetic distances and evolutionary relationships in marsupials of North and South America

“…The study of soluble proteins coded by structural genes has been applied only to isolated marsupial groups, the majority being Australian (Richardson et al 1973, Baverstock et al 1977, 1979and 1980. Therefore, in the present work we report an allozymic study by means of electrophoretic techniques including five South American and one North American didelphid species whose phylogenetic relationships remain unclear.…”