Southern Small White

[bugboy]

Just came across this, could this year really be the year we get a new species? Note the credits to some of the images
https://www.eadt.co.uk/business/will-th ... _YR4sGdoc0

[Padfield]

Here's to hoping! If it does make it over, I would expect it to be in later broods. Although the spring brood is sometimes numerous in the Rhône Valley of Switzerland, where the species is permanently resident, it is in high summer I more commonly see vagrants in the mountains. A similar phenomenon is likely with northward expansion.

Guy

[David M]

This phenomenon has crept up on us all.

Mannii seems to be intrinsically a southern European species with a distribution 'spike' through the east of France and into the low countries.

What we haven't ever yet learned is its ability (or lack of) to cross expanses of water.

It would be nice if it could do so and colonise the UK but until the first specimens are seen here, I remain hopeful rather than confident.

[essexbuzzard]

I’m hopeful, rather than confident of the arrival of Southern Small White. I have never found this species to be particularly common in France, or even Spain, so it seems unlikely to colonise Britain at this time, in my opinion at least. I would be delighted to be proved wrong, of course.

[David M]

...I have never found this species to be particularly common in France, or even Spain..

Nor me, Mark, although that may be down to its close resemblance to rapae and the fact that like many Pierids, it rarely settles to allow a definitive ID.

I'm intrigued at how it has spread northwards so quickly through eastern France yet has not done likewise in the west.

[essexbuzzard]

How many of it’s caterpillar food plants occur in the Uk? It appears to use Candytuft, but that is rare and unreliable, and scarcely appears at all in some years. It also has a very restricted range.

[Roger Gibbons]

This subject was discussed at the EBG committee meeting a couple of weeks ago. This was my email comment to the committee following on from that discussion:

Just to follow up on one point of the discussion yesterday, here is Lafranchis' distribution map (albeit dated 2015) for mannii: http://diatheo.weebly.com/pieris-mannii.html

I don't doubt that - as was stated - mannii has reached Belgium and the Netherlands, but it does not appear from this map that it took a route through France.

The small enclaves of purported sightings of mannii in eastern France do not appear - to me at least - to indicate any sort of route to the low countries. I strongly suspect that a number of "mannii" sightings are, in fact, rapae. Often the submission of sightings are made by people who are well-intentioned but not sufficiently expert to make a definitive identification, and the sightings are accepted without (photographic) validation.

Roger

[essexbuzzard]

Thanks for posting this, Roger. As well as miss-identifications, it is perhaps possible that some confirmed sightings outside the normal range were of wandering individuals or small numbers of migrants, rather than breeding populations.

Time will tell...

[Pieter Vantieghem]

Hi Roger, I don't know where your claim of misidentifications come from. I am a butterfly validator on a Belgian naturalist citizen science platform and I have described the expansion of P. mannii to the Low Countries and its possible drivers in this article here.
In the article I also give some information about the small resident populations of the western subspecies P. mannii andegava only recently discovered (present since at least the 1970's but only confirmed in 2012) in NE France and S of Grand Duché de Luxembourg (the small enclaves you talk about). There is no doubt the species is present there, I have seen both adults as larvae at one of the French locations (including L2-3 larvae with dark head capsule). At this point however also the expanding subspecies P. mannii alpigena is already present in the NE of France. There is more than one shortcoming to find in the distribution maps on the website of Lafranchis (for T. lineola/sylvestris for example he uses the same distribution map on his website while in his latest book the map for T. lineola shows it to be absent in the extreme NW of the country and T. sylvestris to be present, while in adjacent Belgium it is the other way around).
Ofcourse people in the Low Countries sometimes struggle with the determination of P. mannii but there is no doubt it is at this moment widespread in the eastern half of the Low Countries. Sightings uploaded to the local citizen science platforms are monitored closely, as well in Belgium as in the Netherlands, so misidentifications should not be of influence on our view of the distribution pattern. Especially in late summer & autumn generations the species can be locally common in gardens using Verbena bonariensis and Buddleja davidii as nectar source and using Iberis sempervirens as larval foodplant. It can use other Brassicaceae as well and reproduction on Diplotaxis tenuifolia for example has been confirmed in Germany.
The reason why they only slowly move west in France is in my opinion geographically as they have used the warmer SE-NW river valleys of Rhine and tributaries to expand northward (and as the species has up to 5 generations per year this goes rapidly), while a combination of colder mountaineous areas (fe Vosges), forested areas and large agricultural zones keep them from going W in France.
On my flickr page there is a whole bunch of pictures of the species in Belgium, NE France (including caterpillars) and elsewhere in Europe: https://www.flickr.com/photos/161811907 ... 1848145575
If you are interested in any information on the range expansion of this species I can always be reached by mail (my address is in the article). As the range expansion mainly took place in German speaking countries (Switzerland & Germany) there is a whole bunch of local German literature, I have most of it and would be happy to share.

[Roger Gibbons]

Peter,

May I suggest that you have read an intent into my posting that was certainly not what I intended, so I will repeat the sentence here:

I don't doubt that - as was stated - mannii has reached Belgium and the Netherlands, but it does not appear from this map that it took a route through France.

I think this makes it explicitly clear that I am not doubting the existence of mannii in the low countries. I have many friends in the low countries, especially in the Netherlands, who are experts and I would not dream of disputing their identifications.

I am simply commenting that the distribution map of mannii in France strongly suggests that it took a route which does not appear to have been a northward spread through eastern France. It occurs in Switzerland as I think Guy has commented, so this seems a far more likely route northwards.

So let me expand on the rationale for my comment on mis-identifications which, given that my questioning related to the distribution of mannii in France, fairly obviously related to France. The OPIE PACA Atlas lists a few hundred contributors and to the best of my knowledge there was no validation process applied to the acceptance of sightings submitted. Clearly, a significant percentage of these people would not be classed as experts. I am on the validation committee for the soon-to-be-published CEN-PACA Atlas and I have queried several records which, when subject to scrutiny, turned out to be dubious and have been removed. I have recently queried a few records that did not appear to match the known distributions of easily-confused species and it turns out that the person recording it had no knowledge that there was a very similar (and much more common) species with which it could be confused. I also get asked for an opinion, especially on Pyrgus species, from French forums of enthusiasts/experts and some of the opinions that had been suggested are clearly not correct.

Having said that, I have been researching my local patch in southern Var and I have recorded species such as baeticus, tityrus, ilia, fidia, which are some tens of km from the nearest known locality. That is why I am glad to see that CEN are taking a much more rigorous approach.

Roger

[David M]

...I have described the expansion of P. mannii to the Low Countries and its possible drivers in this article here.

Pieter, many thanks for posting this. It has certainly helped me to increase my understanding of this species.

[Pieter Vantieghem]

Dear Roger,

I certainly don't want to start a large discussion here and apologise if my first post appeared a bit too defending, I shouldn't have put it that strong maybe.

Ofcourse every citizen science project has to cope with the quality of the data it gathers. I am fully aware of that (check this article on that matter ) and I think this will not be different with P. mannii in the PACA region or any other region. And very often it is the rarer of a species pair that has to cope with the (relatively) largest amount of false data.
This however is in my opinion not contradictory to the fact that P. mannii is spreading its range in France as well and has been seen on a large number of unusual places in the east of France, consistent with the pattern we have seen in Switzerland, southern halve of Germany and the low countries.
And indeed the range expansion was probably not made directly from S to N. The suggestion that Ziegler made when he described the species' expansion in N Switzerland (2008) was that the species reached that region through the French Rhône valley, and this still seems a vallid suggestion to me. From there the Rhine valley was quickly reached, enabling the species to move north and diluting to west (including NE France) and east from there.
It is however nowadays already present in large parts of NE France and I would think that P. mannii can be found locally in the correct habitat and at the right timing (generations seem to be a bit more concentrated here in the N than in P. rapae but this is just a feeling) in all northeastern departements of France and that the map on the website of Lafranchis is outdated and an underestimation.
It was for example already described from the Haut-Rhin in 2009, only one year after the article by Ziegler describing the species' expansion in Switzerland. Essayan et al. (2012) describe the species from several departements north of the Alps in E France (article in Alexanor, I have it in pdf if people are interested). Check also this information by Bourgogne Nature where there is a map of sightings at the end. In an article in the German local magazine Melanargia Werner Schmidt-Koel describes how he has found the species in a French village in the Moselle departement close to the German border in 2014, so in the very northeast of France. He also describes sightings near Nancy.
And some sightings on the Dutch based citizen science platform observation.org show the species to be present at the edges of villages, this one in the Vosges and this lady has a lot of observations in her suburban garden in the Loire.
So more than one example showing how widespread the species is in the NE of France.
So apologies for my too defending first post but don't underestimate how widespread the species is!

It has certainly helped me to increase my understanding of this species.

Thanks David!

[Roger Gibbons]

Hi Pieter,

No problem, I just wanted to make it explicitly clear that I was not doubting anything you said and to make it clear that my comments relating to mis-identifications related to some French regions. However, I think this is now changing as there is much more study (many French départements have, or are planning to have, their own Atlas) and there is much more scientific rigour being applied to the process of validation. I have the Atlas for Bourgogne and Franche Comté which includes the mannii page you referred to, which shows a small and rather isolated enclave in the north-east of the region.

It seems that a number of species are spreading northward in France, often along the Rhône valley. Last year I had a report that cleopatra had reached Lyon and today I had an email confirming that it had overwintered there, so is clearly becoming established.

France is still very much under-recorded, even in species-rich Var. It was believed that ballus was limited to just two localities in Var, but in my first few years in the region I located another five previously unknown sites. I have found betulae in northern Var and Chris Jackson has found it in the far west of Var. Maybe pumilio will even turn up one day in some unchecked spot.

Regards
Roger