Sundews and insect declines

1

Anyone got lots of old pictures of sundews?

I was looking at sundews yesterday and seeing that some of the leaves had old husks of the insects they had caught. Then wondering if this was yet another way of looking at insect declines but in a habitat that might not have been sampled as much as other long-term surveys.

There seemed almost no insects around on the New Forest bogs that I was looking at, most common were small red damselflies which I think used to be rare, but very few if any biting insects that used to be such a pain.
However I then looked more closely at the sundews and although they initially looked clear of insects, when you looked in detail quite a lot of the leaves did have remains of an insect on them. Will add some of the photos to iSpot later Sundew | Observation | UK and Ireland | iSpot Nature
sundew | Observation | UK and Ireland | iSpot Nature
sundew | Observation | UK and Ireland | iSpot Nature
sundew | Observation | UK and Ireland | iSpot Nature. Each observation was from a different general area, each image has its own coordinates if needed.

Wondering if it would be possible to count the number of leaves with remains of an insect on now and compare with photos taken perhaps 10 or 20 (or more) years ago to see if there is a change in the proportion of clear leaves vs those with insect remains on.

I am sure there are very many sources of sampling bias in this idea but first thing is to see if there is any data i.e. does anyone have old images of sundews with dates and at least approximate locations. If there is data then consider the bias and whether it is still possible to say something.

2

Mike, I’m sure you’ll find something useful if you check out the project :recycle:iFocus: Sundews:

https://www.ispotnature.org/communities/uk-and-ireland/view/project/849251/

3

Thanks for adding in the sundew project although I did not notice anything there that had looked at the proportion of leaves with and without prey. I was worried that the plant itself may regulate the proportion by growing more leaves or ones with prey dieing off or something like that.

4

Fair enough, Mike.
Why not duplicate some of your Forum post above as a comment so that at least those who commented in the project will be alerted.
J

5

WikiMedia Commons has over 3,000 images related to Drosera; probably still over 3,000 when you strip out distribution maps, etc., but perhaps closer to 2,000 when you remove the images of flowers. Might not be all that useful however, as they include lots of different species in lots of different habitats.

Drosera - Wikimedia Commons

CalPhotos has 136 Drosera anglica, among lots of others.

CalPhotos: Browse Plant Photos by Scientific Names (berkeley.edu)

PlantNet has 1,250 observations of Drosera rotundifolia, and a few hundred for Drosera anglica, and for some other species.

World flora: Species - Pl@ntNet identify (plantnet.org)

6

At first thought you have two alternative ways forward; either read up the literature on Drosera insectivory to see whether the possibility of a signal is plausible, or grab some images and see whether it shows any signal (and then worry about confounders). One potential issue is that any seasonal signal may obscure any secular signal - if plants have been photographed on different dates in different years.

7

https://www.researchgate.net/profile/Balazs-Baranyai-2/publication/351765637_Seed_germination_and_seedling_survival_of_Drosera_rotundifolia_L_cultivated_on_Sphagnum_Influence_of_cultivation_methods_and_conditions_seed_density_Sphagnum_species_and_vascular_plant_cover/links/60a81ef9299bf1031fbd5190/Seed-germination-and-seedling-survival-of-Drosera-rotundifolia-L-cultivated-on-Sphagnum-Influence-of-cultivation-methods-and-conditions-seed-density-Sphagnum-species-and-vascular-plant-cover.pdf
This is an interesting paper it does not give an answer about whether a signal is plausible but interesting that they could not grow the plants in greenhouse as they were not allowed to give supplimentary food and there were not enough insects in the greenhouse.

8

I missed this year’s Sundews but there IS a crisis brewing.
I suspect the lack of insects this year will show up next year with the lack or very low count of seed heads on plants.
I found it interesting yesterday that CLOUDS of biting midges were around me and that the swallows have also done quite well.
I recently did this https://www.ispotnature.org/communities/uk-and-ireland/view/observation/885524/ one of two. The tag might be useful - anyone?