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

100%

Barrantes G. E., Daleffe L.

Acta Theriologica

1999

tom 44

nr 3

AUozyme genetic distances and variability were studied by horizontal starch gel electrophoresis in 6 species of marsupials from North and South America representing 4 different genera. Twenty-one presumptive loci were assessed in a total of 151 specimens. Only 1 of 21 loci was found to be monomorphic in the whole sample. Phenetic and cladistic interspecific analysis coincided in rendering two sharply differentiated subgroups: one comprising species of the genus Didelphis Linnaeus, 1758 CD. marsupialis Linnaeus, 1758, D. virginiana Kerr, 1792 and D. albiventris Lund, 1840), and the other comprising Monodelphis dimidiata fWagner, 1847}, Lestodelphys halli (Thomas, 1921) and Lutreolina crassicaudata (Desmarest, 1804). No relationships between the bradytelic condition, the karyotype stability of this group, and genetic variability were found. On the other hand, the existence of species with brief life span such as Lestodelphys halli and Monodelphis dimidiata (Marmosini tribe) and species with long life span (Didelphini tribe) allowed us to test the hypothesis which correlates generation-time with genetic variability. We conclude that a general explanation for genetic variability must involve more than just generation-time,

Growth studies in Akodon dolores [Rodentia: Muridae] in captivity

100%

Piantanida M., Barrantes G. E.

Acta Theriologica

1998

tom 43

nr 2

Growth processes in Akodon dolores Thomas, 1916 were studied by measuring morphological variables in a captive colony of 1500 specimens. Sex differences were not statistically significant. Most variables fitted to a sigmoid function and showed the same behaviour up to 3 months of age: an acceleration in growth up to the first month, followed by a deceleration up to the third month. Growth variables reached their asymptotic value after the fourth month of age. An exception was the lens weight which continually increased with age without reaching an asymptotic value. The instantaneous growth rates became less than unity at the third month of age, indicating that the maximal percentile growth should be before this stage. The latter was corroborated with the body weight increase and body length curves in which the inflexion point was observed at the 1-month stage. In A. dolores this stage is physiologically associated with puberty and in the present study was reached when the animals achieved 40% of their adult body weight. This study is the basis of an age distribution study of A. dolores with a biological foundation.

Ograniczanie wyników

2 Acta Theriologica

2 Barrantes G. E.

1 Daleffe L.

1 Piantanida M.

1 1999

1 1998

Wyniki wyszukiwania

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

Growth studies in Akodon dolores [Rodentia: Muridae] in captivity