Apples on sticks

Yesterday the south-east group of the British Bryological Society visited the town of Wadhurst in the far east of Sussex, near Tunbridge Wells. A variety of habitats including streams, woodland, grassland and ditches led to an array of moss and liverwort species being recorded. All were new for the area as this was a place no bryologist had dared to tread before.

Highlights included my favourite liverwort, the large and fragrant Conocephalum conicum (Great Scented Liverwort), as well as non-bryophytes such as two new plant species for me – Orpine and Soft Shield Fern – and a new carabid in the form of Carabus monilis with its bronze lustre. However, apparently the best find of the day was one of mine. This was the apple-moss, Bartramia pomiformis.

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Bartramia pomiformis

This moss immediately struck me, growing on a sandy bank on the edge of a narrow lane. The patch was almost perfectly circular, a richer green than the surrounding winter vegetation. And it was easy to see how it got its name, from the rounded apple-like capsules.

These capsules, that many mosses have in some form or another, form the final stage in the life cycle of a moss. The capsules contain the spores. Like a fruit, the capsules darken with maturity, starting off green such as these but soon becoming dry and brown with age, at which point the spores will be released.

These spores, upon germination, will then grow into a protonema, which will develop into a sheet of felt-like rhizoids, from which the gametophore will arise. The gametophore will be the stage of a moss that many people will be familiar with. It is the typical plant-like form, with stems and leaves, resembling a flowering plant although without vascular structure. This means that mosses lack the transport systems that vascular plants use to transport water, nutrients and minerals to their cells through tubes such as the xylem and the phloem.

Mosses can be dioicous or monoicous. Dioicous mosses have the male and female reproductive organs on different individual gametophores, while monoicous mosses have both sex organs on the same plant. In both cases, the sperm from the male sex organ will be transported to the female sex organ by a drop of water, which is one reason why there is a higher density of moss species in wetter climates such as the Atlantic rainforests of western Scotland and Ireland.

Once fertilisation takes place, a sporophyte begins to emerge from the venter, where the embryo develops. Over a period of many months, a seta (stalk) will grow, on top of which a capsule will be produced. Eventually this will release spores, and the cycle will repeat itself.

When diving into the life cycles of many taxonomic groups, I am often amazed by the complexity behind what appear to be fairly simple organisms at a cursory glance.

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Species no. 3000!

Admittedly Stratiotes aloides, known vernacularly as Water-soldier, is not the most desired plant to have in an ecosystem. It is possible that it is native in East Anglia and Lincolnshire however in Sussex, where this species became number 3000 on my pan-species list, it is more likely to be introduced.

Yesterday I joined the Sussex Botanical Recording Society on a visit to Court Lodge Farm on the Pevensey Levels, which possesses a rich assemblage of aquatic plants in the many ditches. Some special species recorded included Potamogeton obtusifolius (Blunt-leaved Pondweed) and Petroselinum segetum (Corn Parsley), the latter growing on the banks of the ditches rather than within them as was the case with the pondweed.

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An example of one of the ditches where we were recording. The majority of the water plants you can see in the photo would  be Lemna trisulca (Ivy-leaved Duckweed), Elodea nuttallii (Nuttall’s Waterweed) and the aforementioned Potamogeton obtusifolius (Blunt-leaved Pondweed).

Although despite these Levels specialities being present, for the ditches it is hard to escape the colonisation of several non-native invasive plants. Fortunately we didn’t come across any ditches which were dominated by these unwanted waterweeds however both Azolla filiculoides (Water Fern) and Hydrocotyle ranunculoides (Floating Pennywort) were found along with the robust growth of Water-soldier.

Water-soldier can be quite problematic for native flora. Small populations can, if left undisturbed by boats or large numbers of waterfowl, develop into armies. These can completely annex stretches of canals or ditches, out-competing ‘friendlier’ water plants for resources. The following quote is from the Water-soldier’s species account in the recently published Flora of Sussex: “On Pevensey Levels it has spread considerably, and in 2010 was found to be completely covering a ditch for several hundred metres”.

Despite this, I find its biology quite interesting. In the autumn it will begin to stop photosynthesising, and gradually lose the gas in its leaves that keeps it afloat. It will sink to the bottom of the ditch or canal where the water is unlikely to freeze. In the spring the increased strength of the sun’s rays will penetrate deep enough to allow the sharp, serrated, sword-shaped leaves to photosynthesise again, producing oxygen which gives the rosettes their buoyancy.

I was not originally planning to write a blog post on the Water-soldier until I realised today while inputting yesterday’s finds into my list that it fits into the 3000th slot. I am quite relieved that I have managed to reach this milestone, as the target I set myself in a blog post I wrote when I reached 2000 was to record my 3000th species before my 15th birthday. As of today I’m 14 years, 11 months and 1 day old. So I reached my target, but only just. It is hard for me to imagine stopping pan-species listing, however with upcoming GCSEs and A Levels I imagine I might have to slow down a little. But to keep it ticking, I have decided to set myself another target: 4000 by the end of 2019. Wish me luck!

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Two plants surrounded by Frogbit (Hydrocharis morsus-ranae) resembling miniature water-lilies.

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The snow-white flower of Water-soldier. The flowers are not seen too often, with the main method of reproduction being vegetative: the lowest leaves of the plant have axillary buds which will detach when the leaves decay and can disperse long distances before resprouting. This species is what’s known as dioecious – this means that male and female flowers are found on different plants. For some reason, there are very few if any male plants in England, so all reproduction in this country is vegetative as described above.

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The four or five plants in the photo here represent about half of the largest population of them I saw, luckily it hasn’t reached the levels of dominance seen at other parts of the Levels.

Sussex Rarities – Hairstreaks & Clubtails

This morning, having heard some exciting news on the website of the Sussex branch of Butterfly Conservation, I found myself in Ditchling Common Country Park, scanning bracken after bracken with my binoculars. I was looking for a Black Hairstreak or two. The windy and overcast conditions were not conducive to my hopes of sightings along the lines of the day-count of 98 that was made earlier in the month!

These numbers are quite extraordinary considering the fact that this species was only confirmed to be found in Sussex just over a week ago. Following a few battered individuals found at the same site last year, a survey has been undertaken to determine the presence of this colony. Its appearance here is particularly notable as this site is far from the existing distribution of this species in the UK. It is thought to be confined to a band of clay soil in the Midlands, mainly Cambs, Northants and Oxon.

The closest Black Hairstreaks have previously come to Sussex is Surrey, where they were introduced in the middle of the 20th century. However, the habitat at the introduction site was destroyed and the species disappeared there. The species is not known for their long distance movements or dispersal at all, in fact patches of identical habitat to where they are found elsewhere on the same site often go uninhabited due to the reluctance of the butterfly to travel long distances. Therefore it is thought that this colony is also an introduction similar to the Surrey one, although despite it only being discovered very recently it is likely that the species first appeared in the 1990s – this is because the expanse of the population at Ditchling Common suggests that it has been expanding for quite a while. It’s so slow that the rate of expansion, even of a healthy population, is estimated to be only about a kilometre per decade!

Now, back to this morning. The foodplant of the Black Hairstreak is Blackthorn, and it was in abundance at the country park. This was especially true at a corridor that extends from the fish pond south-west to the Folders Lane East. This was where we focused our searching, which turned out eventually to be the right idea. At 10.30 the sunshine finally made a prolonged appearance and the wind died down slightly. This appeared to trigger the daily emergence of the hairstreaks to warm up on the bracken. The first one we found was perched at quite a gradient on one of the fronds, perfectly angled towards the sun. After a few minutes of sitting very still, it switched sides rather in the fashion of a sunbather aiming for an even tan. As it had not yet gained enough thermal energy it was being quite ‘co-operative’, allowing for great views. This sighting was repeated with up to three other Black Hairstreaks, a very satisfying way to see a new butterfly species for me: not a common occurrence!

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Although the sexes are hard to differentiate on physical appearance, it is likely that those we found were females. The males will emerge earlier, in order to have established a territory prior to the emergence of the females. They will fiercely defend their territory, which is usually centred around an oak known as the ‘master oak’, and approaching the end of the flight period this activity will render them quite battered and damaged. It is likely that this species is past its peak already this year. The species’ very short flight period is one reason why this colony may have remained undiscovered for such a long period of time. Years where the population is dramatically increased compared to previous and following years are also characteristic of this species. It is likely that this year is one of these ‘boom years’ which is what may have lead to this year being the one in which this colony was finally discovered. So if you haven’t yet had a chance to visit this true Sussex rarity, I would recommend that you do so sooner rather than later. Their short adult stage will be over before the end of June, and in future years there probably won’t be as many as there have been this year.

Black Hairstreaks are not the only entomological rarity I’ve had the good luck to see in Sussex this month. At the beginning of the month I took a walk along a small stretch of the River Rother, near Fittleworth in West Sussex. Having been advised about their presence there by Amy Robjohns and Olly Frampton, I was on the lookout for Common Clubtails, a species that isn’t actually as common in the UK as its name suggests. On the British Dragonfly Society website it is described as “extremely local”, only being found on a few rivers in Wales and southern and central England.

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However, its scarcity on a national basis was certainly not evident along this tranquil, luscious river in the mid-morning sun. Along only a few hundred metres of the river we managed to find at least 10 either hunting along the river or perched on bankside vegetation and overhanging willows. The vast majority were males which were patrolling their recently acquired territories while many females would be seeking protection in the nearby woodlands away from the water. They will soon return to mate and lay a new batch of eggs, which will complete their immature stages in the silty riverbed within 3-5 years.

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Orchid on the Hill

The Early Spider-orchids Ophrys sphegodes at Castle Hill NNR have one of the best views of the South Downs as well as Brighton to their south-west. On the northern edge of Woodingdean, a chalk grassland slope supports this nationally scarce species, which has only a scattered distribution along the South Coast from Dorset to Kent.

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This orchid is named after its appearance, with its flowers apparently resembling the abdomen of orb-weaver spiders. However, its flower shape has evolved so that it resembles bees, which come to try and mate with the flower, known as pseudo-copulation. This is also the case in the perhaps more appropriately named Bee Orchid for example. To complement the shape of the flower, these orchids also release the scent of female bees which further entices the male bees to unknowingly pollinate the plants.

However this technique may show to be detrimental towards the success of the species in the face of climate change. Despite the strength and accuracy of the scents wafted by the flower, they cannot compete with actual female bees. Therefore, the plants most likely to pollinate and reproduce successfully are those which blossom after the male bee has emerged although before the females. Although sadly warmer spring temperatures are pushing the phenology (life cycles) of these two species out of sync.

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It is also interesting to observe the variation in the exquisite patterns shown on different individual flowers, such as these:

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Travelling to find these orchids (a new plant for me) was a perfect break from revision. Despite their rarity, there are several reliable sites such as Durlston Country Park and Dancing Ledge in Dorset, Samphire Hoe in Kent and of course where I visited today, Castle Hill NNR in East Sussex. I would definitely recommend looking for them before they stop flowering in early June!

 

Eastbourne Strikes Twice

This morning, after struggling through incredibly thick mud, I reached a huddle of birders all looking at a small Robin-sized bird with a faint blue crescent on its breast feeding on the edge of a large reedbed. It was a male Bluethroat, a fantastic record for the time of year and for Sussex.

The bird was first seen last Sunday at West Rise Marsh in Eastbourne and identified from photos on Tuesday. Luckily it stayed around and has since allowed many Sussex and national birders to see it although it has been elusive. Unusually for me, it was not as elusive when I went to see it as I immediately had it in my binocular view after arriving. Much better than standing around for hours in the biting wind which some birders have had to do over the past week!

It appears to be a White-spotted Bluethroat, one of two subspecies of Bluethroat that have been recorded in the UK. It seems to be the less frequent subspecies, with the Red-spotted Bluethroat being the other that sometimes reaches our shores. Due to the difference in latitude of the two subspecies’ breeding ground, they typically arrive at different times of year. The White-spotted is most commonly found in late March and April whereas the Red-spotted is more likely to be found in May. Although White-spotted is the earlier arriver, it is more likely that this bird has been wintering in the UK, rather than having overshot its breeding grounds on its spring migration.

Occasions of Bluethroats wintering in the UK are occasionally recorded, for example last year a bird was found in February in Lincolnshire which remained until the end of March. Presumably it then attempted to migrate to where it thinks its breeding grounds are. It will be interesting to see if this Eastbourne bird stays much longer and whether it tries to set up a territory here or flies elsewhere to breed.

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Fantastically, this is not the first Sussex rarity that Eastbourne has had to offer this winter. Black Guillemots, although they breed on remote islands in the north of England, are even rarer in Sussex than Bluethroats, so for one to turn up in Eastbourne’s Sovereign Harbour was quite special. It has been present since late November, although I waited until the New Year before going along to see it. It’s a wonderfully confiding bird in a great setting!

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Myrmecomorphy in action!

Sunday the 15th October was the date of the Amateur Entomologists’ Society field meeting at Rye Harbour Sussex Wildlife Trust reserve. It’s not often that I do a focused invertebrate hunt at this time of year, so I was looking forward to seeing what we found.

The field meeting was unexpectedly good on the arachnid side of things. I had no idea that the reserve was so rich in numbers and species of spider. We spent most of our time in a compartment of saltmarsh and shingle, where the shingle was really shallow. The layer of shingle was about two stones thick, and the soil beneath it was compact. This meant that the spiders could not escape deeper into the shingle as they would at most shingle sites.

One of the highlights of the field meeting spider-wise was the fantastic Myrmarachne formicaria. As the scientific name suggests, this species of spider is an ant-mimic (the prefix ‘myrm’ means ‘ant’ and a formicarium is an ant farm). The mimicry of ants in the animal kingdom is known as ‘myrmecomorphy’ and is quite common across a number of invertebrate orders. Invertebrates that are known to be ant mimics include young grasshoppers, true bugs (Hemiptera), flies, beetles and of course spiders.

But why do so many invertebrates mimic ants? Ants are known among the predators of invertebrates to be aggressive or distasteful, so they are avoided. And the predators will also avoid any insects that look like them, but lack any means of defence such as the young grasshoppers. This is known as Batesian mimicry, as it was first described by H W Bates. Some ant mimics have even gone as far as to mimic the ants chemically as well, by emitting ant-like pheromones, which is referred to as Wasmannian mimicry.

However, Myrmarachne formicaria may mimic ants for a different reason. It is thought that some spiders mimic ants not only for protection against predators but also so that they can hunt the ants themselves. Ants will overlook the spiders as one of their own colony, giving the spider the perfect opportunity for a meal. This type of mimicry is aggressive mimicry. As you can see from the photo below, the spider has a long abdomen, which helps it to resemble an ant.

Myrmarachne formicaria male by Evan Jones

Myrmarachne formicaria, photo by Evan Jones, one of the field meeting attendees.

Myrmarachne formicaria really was a fantastic sight, and I hadn’t personally seen anything like it before. It was fascinating to learn how and why so many different invertebrates mimic ants. The sheer number of ant mimics must indicate that ants are one of the most successful of all invertebrates.

Royalty visits Peacehaven

Across the country there are loads of lepidopterists who walk transects across pieces of land to record all the butterflies present at these locations. We have them to thank for a wealth of data on the distribution and statuses of the UK’s butterfly fauna but also for a number of interesting sightings. An example of the latter was an incredible sighting of no less than 3 male Queen of Spain Fritillaries lekking around a bonfire on a farm on the edge of Peacehaven, near Piddinghoe!

These exotic butterflies were first seen on the Saturday (26 August) by Dave Harris on his transect. It’s private land, however I am incredibly grateful to the farmer Colin Appleton for allowing access, as I was able to visit the site yesterday (29th).

Upon arrival at the location we could immediately tell that this was the place! There were quite a few naturalists spread out across the narrow meadow, searching for the fritillaries. It was about 2.15pm and they had not been seen since 12.45 – which was worrying – however there were still many other nice butterflies to look at while we searched.

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Clouded Yellow – also a migrant butterfly however significantly more common!

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Small Copper

Eventually, 30 minutes after arrival (not too bad considering we could have been waiting for a lot longer!), the keen eyes of Amy Robjohns spotted one fly in and land on the ground. It proceeded to sun itself for the next minute or so before moving to a separate patch of dry earth for a little while longer. Just the one – and it appeared to be much more elusive than on previous days. I would be surprised if any are seen again after today’s forecast bad weather.

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The fritillary sunning itself

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The only photo I got that shows the large white spots on the underside of the wings, characteristic of this species.

It may seem odd that 3 were seen at this same site together, for such a rare migrant. However, they are known to travel in groups, like some birds. However, once they had arrived at the farm, they turned hostile against each other, and used the aforementioned bonfire as a lekking site. Here they would fight against each other, and even drive away innocent butterflies of other species such as the Clouded Yellows and the Common Blues. A lek is used to attract the attention of females and for the females to choose a mate. No females have been seen (yet), however they are more elusive, so perhaps we could be seeing another generation of these exotic butterflies sometime soon.