Beach and Dune - Gower - page 152

Probably the most interesting of the dune spiders is the jumping spider Synageles venator , a very rare
species only recorded from a few locations, of which Gower is one. Unlike most jumping spiders, which
stalktheirpreyuntiltheyarenearenoughtopounce,thisspeciesdoesnotactuallyjump.Insteaditcatches
its prey byrunning fast along the stems ofthe marram grass. It is a particularly interesting spider in that it
isanantmimic.Spidersdislikeantssincetheyareabletosquirtformicacidasadefenceandthisjumping
spider has taken advantage of this, copying the behaviour and appearance of certain species of ants that
occur in the marram grass. To do this the spider runs around with its front legs held in the air like an ant's
antennae, giving it the appearance of having six legs like an ant. Two white curved lines also run across
the centre of the spider's abdomen like the two 'waists' of an ant. It carries out this deception so effect-
ively that it is protected from attack by other spiders, which mistake it for an ant and either leave it alone
or even retreat rapidly.
Other invertebrates found on the dunes include the common banded snail Cepaea nemoralis and the
gardensnail Helix aspersa .Vertebratesincludethenumerouscommonlizard,whichinhotweathercanbe
seen in exposed areas basking in the sun. There are also records of the rare sand lizard Lacerta agilis , but
these need checking as the current distribution maps show that it is limited to southern England. Adder,
grass snake and slow-worm can also be found.
FUNGI
Sand dunes are incredibly rich in fungi, and because of their role in decomposition and the mycorrhizal
associations they form with higher plants they have a crucial role. In particular by producing phosphorus,
nitrogenandothernutrients,suchascalcium,potassium,sulphurandzinc,theyhelpotherplantstocolon-
ise the dunes. Around ten species of large fungi are restricted to dunes and most of these are specifically
adapted to colonising the mobile dunes. As they are saprophytes, feeding on dead or decaying organic
matter, they require dead marram grass or buried rabbit dung and a continuous supply of incoming sand.
The commonest of these fungi is the marram brittle-cap Psathyrella ammophila , but the dune cup fungus
Peziza ammophila andthedunestinkhorn Phallus hadriani alsooccurfrequentlyinthishabitatinGower.
At Whiteford the field bird's nest Cyathus olla , an ally of the puffballs, has also been found in the mo-
bile dunes. This is a peculiar fungus that consists of a trumpet-shaped cup or 'nest', measuring about 10
millimetres in diameter, containing a number of small spherical spore masses or 'eggs'. The nests act as
'splash cups', and when hit by raindrops the spores, which are attached by very thin coiled cords to the
outer wall of the cup, are splashed out to distances of more than a metre. In this process the cord becomes
detached from the cup and helps the spore mass to stick to surrounding objects.
Other members of the Gasteromycetes, or stomach fungi, can be found in the mobile dunes alongside
thefieldbird'snest.Themorecommonspeciesincludebrownbovist Bovista nigrescens ,lead-greybovist
B. plumbea , grassland puffball Lycoperdon lividum and meadow puffball Vascellum pratense . Like the
field bird's nest they all rely on some external agency to spread their spores, such as mammals or insects,
or the physical effects of wind and rain. Rare species include the least bovist B. limosa , which was re-
centlyfoundatWhitefordBurrowsinanareathathadpreviouslybeenburnt,anditseemstobeaprimary
coloniser of such sites.
Further inland on the fixed dunes at Whiteford there is a surprisingly rich group of fungi. In fact
in well-grazed dune grasslands such as this the number of fungi species can outnumber that of vascular
plants. The most obvious fungi are the parasol mushrooms Macrolepiota spp., but these grasslands also
supportagreatnumberofwaxcaps Hygrocybe spp.Inallabout24waxcapspeciesandvarietieshavebeen
found in dune grassland in Britain, occurring only where the nitrate and phosphate levels in the soil are
very low. As they cannot tolerate even small amounts of fertiliser they are excellent indicators of good-