Variety in Common Blue females

[millerd]

Does anyone know what governs the blueness of Common Blue females? I know I've read somewhere that northern ones are bluer than southern ones, but on the 20th I found a couple locally (Harmondsworth Moor - squeezed between the M25 and Heathrow) that were very different. In fact, these were the only two I saw that day.

[Jack Harrison]

Hypothesis.

The very blue females seem to be proportionally more numerous at times when the Common Blue itself is abundant. Last summer’s brood, which was generally a good one, gave the impression of a having greater percentage of blue females than usual. This May, when the Common Blue again seems to be having one of its better years, similarly seems to have a good proportion of blue females.

I surmise that the blue ones are more susceptible to diseases, etc, in the early stages and it is only in good years when mortality is low that these blue females make it all the way to adulthood.

Incidentally, I have thought that the same mechanism might apply to Silver Washed Fritillary valesina, the form seeming to be proportionally more numerous in good years, and indeed can crop up in unexpected places, eg North Gloucestershire in 1976. The variety might lurk in the genes all the time but only in favourable conditions does the form become apparent in the adult.

Jack

[Padfield]

I seem to remember reading, long ago (in Ford, I think), that the gene controlling valezina is recessive, and that the condition itself is significantly disadvantageous (notably in terms of being selected by males). Therefore, to explain its persistence in populations, some heterozygous advantage is proposed (similarly to the way sickle-cell anaemia persists in tropical countries, since heterozygotes have some malaria resistance). Good valezina years would obviously coincide with there being a high proportion of heterozygotes in the population, perhaps affecting the vigour of that brood.

Jeremy Thomas, on p. 218 of the new book, seems to suggest the gene is dominant, not recessive. It's difficult to see how a disadvantageous dominant gene can survive in a population - so there must be some other weird mechanism going on. But Thomas might have meant 'dominant' in a looser sense, implying that when mate selection isn't an issue valezina is more vigorous.

Guy

A bit more research and I find this:

https://openaccess.leidenuniv.nl/bitstr ... 29_165.pdf

See p. 183 (in the scanned text, not p. 183 of the pdf), right hand column.

[NickB]

Some interesting stuff there....indeed, it is difficult to see why a recessive gene persists if it does not infer some advantage - nature usually has a reason (millions of years of evolution to get to today's butterflies).
And Thomas (p132) does state that blue female CBs are more common the further west & north you go - whether there is evidence or he is re-stating common wisdom, he does not say. I have not visited enough colonies in the north and west myself to have an opinion on this, but blue females are present in most colonies, tho' not as extreme as Millerd's. (Nice Blue pic by the way!)

3 years ago I came across a couple of these extreme examples in a small patch on the Devil's Dyke nr Newmarket. I have been back to the same place each year since, but have not come across any similar specimens......so, is it genes, or is it environmental factors such as humidity, temperature or day-length (as Thomas would seem to infer by his western & northern bias).....

Someone should do their PhD on this.....
N

[Piers]

It is a dominant gene that produces the valesina form of the Silver Washed Fritillary, and when breeding in captivity from a valesina female, the female offspring are predominently of this type. Indeed, on occasions when breeding from a type female the entire brood of females is of the valesina form.

So why is valesina not the dominant form in the wild? there are no problems with the viability of ova or larvae from valesina females so why does valesina only make up a small percentage of the total female population? well there are theories for this: It could be that valesina is simply not as attractive to males than the type females. Or (and this is more likely IMHO) the valesina females do not have as much opportunity to mate successfully. Valesina (because of her dark colouration) prefers the shadier areas of a woodland, presumably due to her ability to absorb heat faster. Because of this behavioural adaptation valesina females are not going to be spotted as easily by patrolling males. It is also due to this behaviour that valesina are easy to overlook; even when basking valesina (if the ambient air temperature is warm enough) will often choose to bask wings open on a shaded area of bramble rather than on a flower exposed to the sun.

This behaviour was also very evident in the extreme oscillata aberration in Alice Holt last year: when feeding and basking the butterfly was more often than not to be found on the shaded or partially shaded bramble flowers rather than with her kindred on those flowers in full sun. It is fairly safe to assume that due to this individuals greatly increased area of dark scaling the butterfly absorbed heat far faster and therefore chose to keep out of the direct sunlight when the ambient temperature rose above a specific point.

Interestingly, while in many southern woodlands valesina makes up only a tenth of the female population, there are some woodlands (a couple in South Wilts in particular) where valesina accounts for up to a quarter of all females in 'good' years. There is clearly room for further research into this.

Felix

[Piers]

Ooops; I meant to add...

The blue in common blue females is certainly genetically inherited; this is easily demonstrated by breeding strains with varying degrees of blue (or brown) successfully through several generations from carefully selected females, from completely blue females to those that are totally chocolate brown. It is also easy to breed out particular characteristics (eg. blue hind wings only, blue at forewing base only etc. etc.) and continue these through many gererations.

However; in the wild inheritance could well be multifactorial, with more in play than simply one recessive gene. Environmental factors could also influence the expression of the gene(s).

Felix.

[Padfield]

Yes - a little more research and the authoritative sources do say the form is dominant in the strict sense, though it is referred to as recessive on many websites (e.g. our own Adrian Hoskins' excellent Learn About Butterflies - http://www.learnaboutbutterflies.com/Br ... paphia.htm ).

That makes the condition much more intriguing! Disadvantageous recessive conditions persist much more readily in populations, as with increasing rarity they are expressed even more rarely and so may not be selected against. Couple that with some heterozygous advantage and the persistence is easy to understand. Dominant genes are always expressed and so always subject to selective pressures.

I'd be interested to know your theories on why valesina persists, Felix. Frustratingly, all my reference books are in England and I'm in Switzerland!!

Guy

[Piers]

...though it is referred to as recessive on many websites
Guy

Indeed; but they are incorrect, it is dominant. I suspect that they are unattractive and fail to mate on account of being so shy of the sunshine. (see above). In captivity of course this is not the case and the males pair readily with them when presented with no other options.

On the face of it valesina should become more common in cooler latitudes and down right scarce in bothersomely hot climes, but that is not the case. Odd.

Valesina does tend to go unnoticed due to it's habits. As a child I used to see them on the Polden Hills even though the literature said that they were restricted to south Dorset and the New Forest, but I had to stray into really quite shaded areas of the woodlands to find them.

Felix.

[Dave McCormick]

Nick, isn' the common blue in your images form caerulea? I never seen this before until I saw Adrian Rileys book "British and Irish Butterflies" and it was in it, image: http://www.enterprise-io.co.uk/british_ ... rfly_5.htm (Image 19 I think)

[NickB]

Nick, isn' the common blue in your images form caerulea?

Thanks, Dave. I have never seen an image which matches completely.......and tho' very similar....it does not really match the ab caerulea in the Cockayne index...
I would go for more like ab. apicta-thetis ......
http://www.nhm.ac.uk/jdsml/research-cur ... xonID=8765
..based on the similar lack of orange on this one and the one I posted........
...but I'm sure I could be wrong...

N

[NickB]

http://www.sciencedirect.com/science?_o ... 8942923ec5
Above link to paper on colouring in Common Blues...only read abstract .....
N

[Piers]

Hi Nick,

For what it's worth I am fairly certain that it's ab. apicata-supracaerulea.

The 'apicata' part refers to white inter neural lunules on the apex of the fore wings, which your specimen clearly exibits.

Without the white inter neural lunules it would be referred to as anticoelunata-supracaerulea in which the specimen is blue right out to the costa and with orange lunules on the hind wings only.
If there were orange lunules on all four wings it would be just known as supracaerulea.
If there were no orange lunules on any of the wings it would be referred to as fusca-supracaerulea.

And it is spelled 'apicata' not 'apicta'. The specimen on Cockayne Dbase should read apicata-thetis

Either way it is a beauty though Nick I have to say.

Felix.

[Padfield]

Apicatus means 'wearing a (priest's) conical hat' (from apex). Apicata is the feminine (presumably agreeing with forma). Apictus would mean 'unembellished' or 'undecorated'.

Guy

[NickB]

Thanks Guy & Felix - I really should have paid more attention during my Latin lessons!

(... got bored with declining and ultimately declined further torture...
...usually it was Caesar bashing the Gauls and others in various ways,
...tho' Asterix probably informed me more on that period of history than Caesar and the rest )

Anyway, it will be interesting to see what turns up this season... I keep re-visiting the same patch of the DD......
N

[NickB]

Further to females - I found this looking at some old shots from May this year - I had ignored it because it was so tatty,

But it does exhibit black banding on the forewings, which I have not seen before...

[millerd]

And this one, which has striking black lines across the margins, almost (but not quite) like an Adonis Blue. Apologies for the not quite natural colour - the chalk background defeated my attempts to make it look right. This one's from Totternhoe.

Dave

[NickB]

..found this female pic from 2008.
.

[Dave McCormick]

Your female Nick looks quite like females in the mariscolore subspecies you get here in Ireland, they have more blue than British ones and have the orange spots too.

I have not actually observed any upperside differences in common blues before, but I have noticed spots being missing or smaller in some common blue undersides I have came across. I have also noticed some very small females last year.

[Lee Hurrell]

I had this one in East Sussex last August:

Cheers

Lee

[NickB]

Nice ones. I think this just shows how widespread blue females are!
The mariscolore does have bigger lunuals on the hind wings, I think, but it is very similar Dave.
N