Mynas & comment on inbreeding depression

To: "Martin and Frances" <>, "canberrabirds" <>
Subject: Mynas & comment on inbreeding depression
From: "Philip Veerman" <>
Date: Tue, 28 Mar 2006 00:48:07 +1000
Hi Martin,
I don't see any relevance to the question or the issue, to COMMON Mynas. I would suggest that inbreeding depression (which is what this is called, not because of sadness of breeding with your sister but the possibility of reduced survival or fertility from close-relative matings). It probably kicks in at about a population size of under 50 or maybe 20 individuals in total. It also depends on levels of already existing genetic diversity and the number of deleterious genes existing in this sample. If there happens to be nil deleterious genes existing in this sample (and I'd suggest that is more likely than not), then there is little if anything to fear from inbreeding depression. Many species survive for a long time on much lower population sizes. Most of the bird species introduced to Australia came from very small initial samples. Inbreeding depression is a very theoretical concept. I wonder how many actual demonstrated cases of it exist. I'd suggest very few. I have heard concern of it for the Cheetah in Africa but it has many other problems. Inbreeding depression is only one of many factors likely to cause problems for critically low populations. Things like random catastrophe are much more likely to be the final straw. Myna populations in Australia are not isolated, they do disperse. Certainly the Canberra population of Mynas is many thousands of them and they are breeding very well. No sign of inbreeding depression here. As for "Do mynas need a lower number of individuals than other species/genera .. orders to achieve this effect?" How many other species/genera are you asking about, and how many millions of $ do we have, to invest in such obscure studies, to elucidate that question? Also there needs to be a theoretical or practical basis to ask the question.
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