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Pool Frog programme coming up |
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Caleb
Senior Member Joined: 11 Apr 2011 Status: Offline Points: 660 |
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They did colonise the pingo area, as the last known site was a pingo site- and this is where the water table dropped in the 80s and 90s. There are also historical records from other sites nearby. There was a (slightly) different colonisation route suggested by: Zeisset I., & Beebee T.J.C., (2001). Determination of biogeographical range: an application of molecular phylogeography to the European pool frog Rana lessonae. Proceedings of the Royal Society, London B, 268: 933-938 (diagram below). I don't remember David Bird's 'mountain' post, but this route doesn't seem to have any mountains in the way. |
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GemmaJF
Admin Group Joined: 25 Jan 2003 Location: Essex Status: Offline Points: 4359 |
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So if they colonised the entire Pingo area historically, which we presume was at the time exactly representative of the habitat that would have existed on the 'land bridge' and therefore ideal for dispersal, why not a widespread distribution in the area to this day?
Other native amphibians are still widespread if increasingly becoming discrete isolated meta-populations to this day, but not Pool Frogs? You see what I am saying, if they were native there should have simply been more of them as historically there would have been no barriers to their dispersal throughout what is now known as the Pingo area of Norfolk. I think also they would have been far more common in the literature of the past. There are only isolated mentions of what are thought to be references to Pool Frogs always linked with very localised locations. I might be wrong, but is it not correct that the Norfolk Pool frogs were recorded only from two sites in East Anglia. One being lost in the 19th Century the other being of course the famous 'last site'. It just doesn't conjure up the picture of immediately post glacial Britain to me, much of Norfolk littered with Pingos and Pool Frogs hopping across a land bridge in a noisy rabble to take up home all over Norfolk.
Edited by GemmaJF - 09 Aug 2012 at 3:00pm |
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Caleb
Senior Member Joined: 11 Apr 2011 Status: Offline Points: 660 |
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That kind of depends what you mean by 'site'. There are a number of references to water frogs from various places in the pingo area (and slightly further east), as well as a fen area in Cambs. These and other references from the literature relating to East Anglia were summarised in an EN publication: http://publications.naturalengland.org.uk/file/141025
I think a harder question is why pool frogs disappeared from all the pingos apart from the last site. The reintroduction programme claims that the cause of the final extinction is well understood, but that doesn't really tell us why their range contracted so much during the 20th century. There are lots of good ponds in the area- are they just not quite good enough? Was there a run of poor summers? |
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GemmaJF
Admin Group Joined: 25 Jan 2003 Location: Essex Status: Offline Points: 4359 |
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Well I guess my answer to the last part is I've yet to be really convinced by the evidence that they were ever there (as in a widespread historically native distribution as opposed to a one two or a few isolated locations).
I too thought about the Natterjack decline, but I had always considered them to be more specialised in their habitat requirements than Pool Frogs. Kind of more akin to Sand Lizards so to me it is easy enough to understand Natterjack decline in Norflolk and elsewhere, but not so easy to get a grasp on why Pool Frogs would have undergone huge declines particularly in the Pingo area where we can only guess some of the ponds have been filled with water since the last ice age. Are Pool frogs in Europe generally not that fussy about the water bodies they use? Certainly it was the impression I had. I guess it is possible if the notion of the Northern Clade colonising is correct (see you are slowly getting me to at least consider they might have been native) that isolation could have led to some evolutionary changes that led them to favour specific habitats. It seems true of Sand Lizards, Smooth Snakes, Natterjacks and even to some extent Adder that they appear more specific in the UK regarding habitat requirements than they do in mainland Europe, perhaps simply temperature/season related but it is a trend that tends to be noted as animals reach the limits of their range. Taking that in to consideration it would seem more possible that subtle factors led to a mass extinction.
Edited by GemmaJF - 10 Aug 2012 at 6:42pm |
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Caleb
Senior Member Joined: 11 Apr 2011 Status: Offline Points: 660 |
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As I understand it natterjacks aren't really that specialised (hence their appearance in odd places like the Cumbrian ironworks) but they do very poorly in competition with common frog and common toad. Their main requirement is a pond for late spring/summer breeding that the common species haven't got to first. As pool frogs are also late breeders, maybe they have similar issues? The last site supposedly had low numbers of common frogs. Romney Marsh also has few common frogs or toads- maybe this is part of the reason for the marsh frog's success there? Edited by Caleb - 13 Aug 2012 at 10:21am |
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sussexecology
Senior Member Joined: 30 Sep 2010 Location: United Kingdom Status: Offline Points: 411 |
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Just an idea Caleb - could this be competition with frog and toad populations (niches etc) if they can't compete with those species Or is it because being late breeders that the ponds they use have dried out by the time they come round to breeding? I'm assuming that they return to the same pond each year, as toads do?? If there aren't a cluster of ponds together and so the ponds are isolated, I'm guessing this could make sense. Just an idea though. Regards SE Reptile Ecologist |
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GemmaJF
Admin Group Joined: 25 Jan 2003 Location: Essex Status: Offline Points: 4359 |
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I would go along with that myself as more likely SE.
Looking at Marsh Frog populations I know in the UK they will often occupy ponds a little larger than usually used by common frogs, a little smaller than usually used by common toads and drainage ditches not used much by either common frogs or common toads. There is much to be said for the idea that they occupying a slightly different niche or perhaps more accurately in my mind a wider one than either common frogs or common toads (at least in terms of the large populations of toads and common frogs I've observed). So direct competition might be a factor at some sites, but not all. Much of the success of Marsh Frogs march across Kent can surely be attributed to the fact that they colonised areas not favoured by the two native species. Certainly the hypothesis that Pool Frogs being late breeders and ponds drying up during the 80's seems a better model to explain mass decline compared with direct competition with other species. One can only presume that competition had occurred throughout the period after colonisation without previously causing a mass decline.
Edited by GemmaJF - 13 Aug 2012 at 5:16pm |
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Richard2
Senior Member Joined: 01 Dec 2010 Status: Offline Points: 285 |
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Is it possible to make a supervised visit to the Pool Frog site for research purposes? Can anyone give me a contact address for this?
With thanks,
Richard
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Katie
New Member Joined: 02 May 2013 Status: Offline Points: 1 |
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Hi there
I am desperately trying to track down some marsh frogs to be filmed next week and was wondering if anyone knew of hotspots or had any? Email me at katie@humblebeefilms.com Many Thanks Katie
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Iowarth
Admin Group Joined: 12 Apr 2004 Status: Offline Points: 743 |
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Hi Kate
I have approved your post. There are Marsh Frogs aplenty on the Romney Marshes although I could not give you exact locations. Certainly we have forum members who will be able to do so and hopefully they will see this and respond in time. I have repeated your plea elsewhere in the forum. Chris |
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Chris Davis, Site Administrator
Co-ordinator, Sand Lizard Captive Breeding Programme (RETIRED) |
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