vulgaris versus helveticus

[Jeroen Speybroeck]

A question to all who live in areas where both species of newt co-occur.

I think I know more or less what the books say (e.g. Griffiths' more or less failed attempts (but interesting results) to demonstrate niche seggregation in terms of pH etc.), but what is your impression (a hunch is already enough) on how the habitat choice of Lissotriton vulgaris and helveticus differ?

I'll start. My "home range" has an old, rather small (relictual) beech forest, but also a river valley (which sound deceiving, because it's all very flat) with more "geologically recent soil" (sorry for the crappy description...). The first area seems to me to have at least 10 helveticus for each vulgaris, whereas helveticus is absent from the valley area and vulgaris is widespread. The 1st area, I visit very often, so I can also tell that alpestris is much more common than vulgaris, but a little less than helveticus. Also, alpestris and (to a little lesser extent) helveticus can be found in shady forest pools (even tiny ones), whereas vulgaris rather lives in the larger ponds on the edges of the woods. We also have cristatus, but it is relatively rare, partially due to too much suitable ponds turning from typically cristatus habitat into a place where Salamandra will deposit + eutrophication in the few 'open' ponds (which is hopefully changing now, since new, perfect ponds have been dug out). Nevertheless, we also found that some ponds have reproduction of all 5.

What do you think about pH? OK, helveticus seems more tolerant to acidity, but it also seems to be dominant in hilly country with calcareous, buffered waters, right?

[Paul Lambourne]

Jeroen,

Further to our initial conversation,I would agree with your initial thoughts.

In the UK, certainly in my County, Kent, Helveticus seems to favour ponds in well established ancient would land, beech,oak or a combination of the two. The geology of this part of England is predominatly based on chalk.

In the UK I would suggset elevation plays less of a role, other than the underlaying rock type and vegetation type, as no where in the UK is particually mountainous

I would suggest shading is important, I have personally never observed helveticus in ponds in open areas, always surrounded by well established trees.

Ponds with helveticus in them always seem to have a great deal of of leaf debris and have water levels that appear to have a high "tanin" level.

Kent is something of an epicentre for European distribution of Cristatus, and that is certainly due to geology.

Cheers

Paul

[Alexander Pieh]

Hi Jeroen,
some years ago I kept L. helveticus for a fotosession.
The larva showed at last in the Aquarium the behavior of “bonsai” Cristatus larva.
“Swimming in the middle of the waterbody, floating for a long time, catching (very small) Daphnia s.l., and drifting back to the bottom just to start again.” (Has anybody seen this in the wild?) This behavior is most probably saver (predators…) in a dark and tannin colored pond compared to a sunny pond with clear water.
However, I think your characterization of the water habitats is correct. I know only one habitat with clear and sunfloated ponds and L. h.. An old stone pit in a forest.
Sincerely
Alex

[Jeroen Speybroeck]

Nice shots! Cool observation of helveticus larval behaviour. Would that be different in vulgaris? I mean - couldn't both species, as larvae, adapt to the pond's conditions?
Also, isn't that type of water bodies poorer in predators anyway (= cool forest with little aquatic vegetation versus sunny exposed pond with rich growth of vegetation and a wealth in larval invertebrate predators, seeking out warm water for swift development)?
I know a fool can ask more questions etc. etc. ...

I should perhaps clarify that pH is confusing me - helveticus is the dominant newt in acid bogs and fens, while it also dominates in hilly areas of calcium-rich soil. Part of what I remember from Griffiths' work is that vulgaris tends to be found in less acid places, but experimental results show that it can deal with acidity just as well.

[Jeroen Speybroeck]

BTW, I also wonder if there might be regional variability in the extent of webbing on the hindfeet in male nuptial helveticus. Of course, difficult to tell, because it changes throughout the breeding season and is probably also related to individual fitness etc.

[Sandra Panienka]

That kind of reminds me that I wanted to buy a device for the combined meausre of pH, oxygen content, temperature and conductivity to get a better picture of the ponds in my area.

Where I live the geology is mainly characterized by the tectonics of the Rhine graben and its graben shoulders, the latter are represented by the Odenwald in my area. Depending on where you are the Odenwald region is dominated by sandstones or more crystalline parts consisting of igneous rocks and in parts metamorphic rocks.

Based on the field work I did in my area I recognized that I. alpestris is the most common species in the lower parts of the graben structure as well as the ponds in the higher areas of the shoulders. I only found L. vulgaris in ponds in the lower parts including a pond of an old clay pit and in a gravel pit area. The species seems to be missing in artifical basins and eutrophic ponds with fish in them that are mostly frequented by Pelophylax spec.

L. helveticus I only found in higher locations close to the forest edge or in clear ponds with a flow-through character. Parts of these ponds are in a rhyolite quarry with some of them being clear or even murky without a flow-through. Others are located inside the forest are on a sanstone foundation, have clear water with a creek running through. In all ponds the number of indiviuals of L. helveticus or L. vulgaris was small with only a few specimen found while I. alpestris is abundant. S. salamandra is syntopic to I. alpestris and L. helveticus in the clear forest ponds.
T. cristatus can only be found in some artifical basins in the city area.
In 2010 I mapped the old clay pit in the lower city area which was supposed to be habitat of all four newt species in the 80ies and 90ies. But I was only able to find a couple of I. alpestris and two individuals of L. vulgaris.

@Alexander: I observed this behaviour in I. alpestris larvae and T. cristatus larvae in an artifival basin with clear water at daytime last spring. There were more I. alpestris larvae floating close to the water surface in open water than T. cristatus larvae. Some of the I. alpestris larvae would hover longer in the free water area than the T. cristatus larvae, some for a much shorter time span. It was very interesting to observe. However, T. cristatus larvae seemed to be the better swimmers in the open water areas due to their body shape.

[Liam Russell]

My suspicion is that helveticus is better able to cope with a variety of environmental conditions that vulgaris and cristatus just can't handle. However, when conditions are 'good' the two larger species outcompete the smaller helveticus. I also think that cristatus will readily predate the other two species.

In the hundreds of ponds I've surveyed many have supported all three species, but only one will be in significant numbers. In my experience palmate newts can be dominant in a variety of types of ponds, for example:

- Woodland ponds which are shaded and full of leaf litter which leads to cold, oxygen-poor water which is often acidic.
- Lowland heathland ponds which are completely unshaded and very warm (in the summer, but cold in the winter), but acidic and oligotrophic.
- Upland ponds which are also unshaded, acidic and oligotrophic, but generally cold.

I don't necessarily think that palmate newts favour these conditions, but they are able to survive and reproduce well in them, which the other two species can't. There are obviously a few variables here, but acidity could certainly be a major one and this can vary from pond to pond over very short distances. For example, a site I know has two ponds of similar size within 50m of each other. One is in open heather heathland, the other is in grassland/scrub/woodland. The heathland one only supports helveticus, whereas the other supports all three species but the ratio of cristatus:vulgaris:helveticus is about 100:20:1. My hypothesis is that although these are close and the underlying soil is the same, the grass and scrub have raised the pH of the soil (only slightly) in the vicinity of the second one (as would occur due to natural succession in this area) and this has tipped the balance in favour of cristatus/vulgaris. The cristatus then keep vulgaris numbers down through predation (this pond used to have an introduced population of Hyla arborea which persisted for ca. 90 years, and then declined to extinction as the increasing population of cristatus munched it's way through them). Within the UK as a whole, distribution patterns seem to support this as helveticus is dominant in upland areas in the north and west which are on granite and other rocks which produce acidic conditions.

Although acidity seems important, it might not be the only factor which gives palmate newts an advantage - maybe water temperature plays a part and the palmate newts can tolerate a wider variation. Also vulgaris and cristatus both favour mesotrophic (even perhaps slightly eutrophic) ponds whereas the palmates seem to cope with nutrient-poor waters well.

[Liam Russell]

BTW, I also wonder if there might be regional variability in the extent of webbing on the hindfeet in male nuptial helveticus. Of course, difficult to tell, because it changes throughout the breeding season and is probably also related to individual fitness etc.

I have certainly observed this, there seems to a be a lot of variety in the size and shape of the webbing.

[Jeroen Speybroeck]

Verrry interesting. There seem to be enough parallels, after all.

I believe I might have been mislead by my limited knowledge of geology. Maybe those hilly country ponds I'm thinking of are not at all well-buffered and have a lower pH than I would think. In my area, pH does not really tell the tale, as there is little variation.

I think Liam may be right, although the real reasons are likely to be more complex than what available research has been able to test so far, e.g. Griffiths could not find a clue in pH, but it may be a lot of factors together, leading to a poorer and somewhat harsher and less average environment for helveticus.

Woodland ponds which are shaded and full of leaf litter which leads to cold, oxygen-poor water which is often acidic.

oxygen-rich, no?

cristatus:vulgaris:helveticus is about 100:20:1

That strikes me as weird - I would imagine this to be unstable, as the top predator occurs in much higher numbers than its prey?

[Liam Russell]

Kent is something of an epicentre for European distribution of Cristatus, and that is certainly due to geology.

This is sort of true, it's more to do with the type of agriculture that the underlying geology would allow (before agricultural intensification). Kent is an epicentre of European distribution for ponds as the heavy clay in the Weald was no good for crops so was traditionally (and still is to a certain extent) used for livestock, for which lots of ponds were dug to provide them with water. Typical pond density for the Kent Weald before WW1 would have been 30-50 per square km.