Sex determination in amphibians
Sexual selection in amphibians - Wikipedia
The heterogametic sex is male in all mammals, whereas it is female in almost all birds. Though the original heterogametic sex was female in amphibians, the two heterogametic types were probably interchangeable, suggesting that sex chromosomes evolved several times in this lineage. The XY and ZW geographic forms with differentiated sex chromosomes probably have a common origin as undifferentiated sex chromosomes resulted from the hybridization between the primary populations of West Japan and Kanto forms. It is clear that the sex chromosomes are still undergoing evolution in this species group.
Sexual selection in amphibians
Sexual selection in amphibians involves sexual selection processes in amphibians , including frogs , salamanders and newts. Prolonged breeders, the majority of frog species, have breeding seasons at regular intervals where male-male competition occurs with males arriving at the waters edge first in large number and producing a wide range of vocalizations, with variations in depth of calls the speed of calls  and other complex behaviours to attract mates. The fittest males will have the deepest croaks and the best territories, with females known to make their mate choices at least partly based on the males depth of croaking. There is a direct competition between males to win the attention of the females in salamanders and newts, with elaborate courtship displays to keep the females attention long enough to get her interested in choosing him to mate with.
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