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?