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University of the Witwatersrand (2006)

Reproductive isolation in the striped mouse Rhabdomys : a case for reinforcement ?

Ahamed, Ahamed Mohaideen Riyas

Titre : Reproductive isolation in the striped mouse Rhabdomys : a case for reinforcement ?

Auteur : Ahamed, Ahamed Mohaideen Riyas

Université de soutenance : University of the Witwatersrand

Grade : Master of Science (MS) 2006

Reproductive isolation was investigated in two chromosomally distinct populations of Rhabdomys on the Gauteng highveld. The two populations, Midrand (2n = 48) and Irene (2n = 46), occur 15 km apart, with no known contact or hybrid zone between them. Behavioural experiments, comprising male-female dyadic encounters and female preference tests for same-and different-population male odour, were used to test for premating barriers. Aggression levels were highest in different-population than same-population dyads, and females spent more time with odours of males from their own population than of those of the other population. Breeding and postnatal development studies were conducted to establish postmating barriers. Compared to different-population pairs, reproductive success was markedly reduced in different-population pairings, and the few hybrids that were produced did not breed. My studies indicate that behavioural isolation is well-developed between the Midrand and Irene striped mice, and suggest that the mate recognition system has diverged in allopatry, which would reduce gene flow between the two populations. Such divergence supports the findings of mtDNA studies by other workers who proposed that the two chromosomal forms used in my study represent two subspecies of R. dilectus. Previous studies showed that distant striped mice populations (>900km) displayed behavioural divergence and intermediately located populations ( 80km) were behavioural compatible but had hybrid failure ; the Irene population was used in both studies. In comparison, the behavioural incompatibility between the closely-located Midrand and Irene populations provides support for the reinforcement of previous postmating isolation seen in the intermediately located populations, particularly since no contact or hybrid zone exists between the two forms. However, I cannot rule out other explanations, such as dissimilar ecological conditions, influencing interfertility.


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