I took the opportunity to visit Benfield hill in Hangleton on Friday morning hoping to catch a glimpse of the solar eclipse. Like most folk in Sussex that morning, I was left disappointed. The smog that swept over from Europe just the day before had left a haze cloud which lingered in the skies just long enough to hide the moon moving across the sky to cover the sun.
Back on the ground my attention was drawn towards a sun-shaped flower – Carlina vulgaris. I had first come across this flower a few days before and was hoping to bump into it again to take some photos. The flowers are last years dead heads, persisting still, rather like the smog in the skies. They are strikingly sun-like, even in their dead and worn out state. The inner florets remain a rusty yellow colour with straw-coloured bracts radiating out like the suns rays.
I liked this thistle. I’m surprised I had never come across it before now. It is very distinctive and inhabits chalk grassland – of which there is plenty in Sussex where I have been studying botany these past few years. There is something momentarily beautiful about discovering something you are fascinated by and knowing it has been there all along. It has just taken time for you to discover it.
Viola odorata - sweet violet
Named so because it is the only violet species in Britain to be fragrant – I liken the smell as a mix between parma violets and urine, which makes sense considering the popular 90′s era sweets are in fact violet flavoured. As for the urine..it was not just because my specimen happened to be covered in dog wee….they all smell like it!
It’s that time of year when like little arms stretching up from their earth’s sleep, the fist signs of spring tell us that the seasons are changing and life is awakening. Yet just before I deter my focus to the eager angiosperms – I happen to stumble across yew cones. I was originally attracted to them as they looked like little yellow flowers hanging below the dark strap-shaped leaves of a yew tree. They made me wonder about how conifer pollination worked and this inadvertently brought me back to a phenomenon I have struggled to understand for quite some time. Sexual reproduction in plants.
As with most moments of realisation, they happen at the last minute. So for all this time I have been looking at diagrams on the internet and gaining some understanding, yet not managing to grasp how it applied to a real plant, I took a specimen branch of the yew and had a thought to look for youtube videos when I got back home – and hey presto!
In theory sexual reproduction is simple with plants. There is one reproductive cycle that applies to them all – the ‘alternation of generations’, whereby plants alternate between a gametophyte (n) and sporophyte (2n) stage. However the process varies slightly for bryophytes and vascular plants, with the sporophyte stage becoming dominant for vascular plants and the gametophyte becoming microscopic.
So taking this back to my yew cones, I can start to apply this knowledge to the plant I have observed – which I have struggled to do for so long. Firstly, the cones I have are male. They are very pretty, resembling little yellow flowers and as I tap them a shower of dusty yellow pollen covers my sleeve – here begins the multicellular gametophyte (n) stage.
On my sleeve lay the pollen grains which are the male gametophytes. The gametophytes produce the male gametes or sperm. When the pollen grains are dispersed by wind and come into contact with a compatible female cone, the pollen grain germinates producing a pollen tube that transfers the sperm to the ovule containing the female gametophyte. This marks the end of the gametophyte stage. Short and sweet.
The sperm and ovule then fertilise to form the zygote, which in turn develops into a seed. This is the beginning of the sporophyte (2n) stage of the cycle. In the yew, the seed develops a fleshy red outer coating – the aril – which attracts birds such as hawfinches and great tits to come and eat it. The seed is then dispersed elsewhere along with a small package of fertiliser (bird poo). When the seed finally germinates, the zygote undergoes mitosis to produce a yew sapling that eventually develops into a yew tree.
Once the yew tree has reached a certain age it will start developing cones, either male and female. In the case of the female, the cones contain ovules on each of its scales. Each ovule contains a megasporangium which contains a megasporocyte – a unicellular sex cell. It is here where the megasporocyte undergoes meiosis to produce megaspores (n). This marks the beginning of the gametophyte stage of the cycle.
Meanwhile, in the male cones are the micosporangium. These contain micosporocytes. The microsporocytes undergo meiosis to form the microspores (n). This again, marks the beginning of the gametophyte stage of the cycle. The megaspores and the microspores then both undergo mitosis to become the multicellular archegonium and pollen grains, respectively – similar to the pollen grains which earlier coated my sleeve.
It is now clear to me that when you are looking at a vascular plant, such a yew tree, you are generally looking at the sporophyte stage. The gametophyte stage consists of only a very short period when the male and female cones produce pollen and eggs up until the moment the eggs are fertilised. The same process can be applied to angiosperms and bryophytes with slight alterations – all acting out this alternation of generations – which as all sexual selection is intended for -allows the plant to shed off bad genes and add new ones in! Yet one questions still haunts me…which came first – the yew tree or the yew cone?
Derived from the Greek word pappos, meaning ‘old man’ ….for obvious reasons. It is actually a modified calyx, which is attached to the fruit of the plant (e.g. Achene in Asteraceae). Key to understanding this feature is the fact that members of the Asteraceae have an inferior ovary (they are ‘epigynous’) which means that the ovary develops below the calyx, so that the calyx part of the flower is in a good position to facilitate dispersal of the seed (being exposed to the environment).
I decided to visit Withdean Woods today as I needed to walk my dog and wanted to check out what early woodland flowers I could find popping up.
Firstly, I shall mention wild daffodil (Naricissus pseudonarcissus). This species belongs to the Liliaceae family and grows in clumps as I had found it today. It represents a now uncommon species, as most daffodils we see are the cultivated form. The most obvious difference between the two types are that the wild form has an outer pale yellow perianth and an inner golden yellow trumpet, whereas the cultivated form has an all golden yellow flower. The flower heads are also angled slightly downwards.
My next find was from the family Violaceae, the early dog-violet (Viola reichenbachiana). This was an exciting find for me, having found V. odorata just last week. Admittedly not the best image as I only have my iphone as a camera, but you can just make out the pointed sepals on this plant, as well as the spur being straight and darker in colour than the corolla, which helps distinguish this plant from V. riviniana.
Next on the list is not a flowering plant at all, but the hart’s tongue fern (Asplenium scolopendrium) from the family Aspleniaceae. This fern is easily distinguishable by it’s unbroken strap-shaped fronds, and is common in damp woodlands.
And finally we have the unusual looking stinking hellebore (Helleborus foetidus) from the Ranunculaceae family. This plant almost looks almost out of place within our native flora with dark evergreen leaves and green flowers. In true buttercup style, the calyx forms what you see as ‘petals’ and have purple tinged edges.
March 20th heralded the first day of spring and what better way to spend it than travelling up to Devil’s Dyke with my little Phalène puppy to check out some of the early flowering plants of the chalk hills.
My mission proved to be successful, finding several well-known early flowering species such as sweet violet (Viola odorata), lesser celandine (Ranunculus ficaria), wild daffodil (Narcissus pseudonarcissus) and an all-year rounder, the common field speedwell (Veronica persica). The focus of today’s article will be the sweet violet.
I found several clumps of sweet violet along the hedge and road bank-sides leading up to Devil’s Dyke. The species belongs to the family Violaceae or ‘violets’ which are known most familiarly to me as clumps of heart-shaped leaves in their vegetative state from mid-winter. Violets are characterised by having stipules in pairs at the leaf-bases, solitary flowers which are irregular, and 5 petals with the lower lip-petal having a spur which is used in species identification.
The sweet violet is the only violet that is aromatic, which made the identification of this one fairly easy. Another key identification feature is the fact the leaf and flower shoots all arise from the rootstock of the plant, a feature it shares only with the hairy dog violet (Viola hirta), although V. odorata differs from V. hirta in having closely downy hairs and rooting runners. As well as this, the sepals on this species are blunt, another feature it shares with V. hirta.
This species, like other violets are shade-tolerant, often found along woodland edges or hedgebanks, and often on calcareous soil, as I had found this individual. Another interesting feature of this plant is that the flowers are hermaphrodite, meaning that it has both male and female organs (carpels and stamens) within the same flower. This feature makes this plant capable of self-fertilising or ‘cleistogamy’ in botanical terms, a useful feature if its pollinator species suffers a fall in numbers!
Ivy belongs to the family Araliaceae, a family of flowering plants to include a diverse array of habitual form such as trees, shrubs and lianas. Within this family lies the genus Hedera, a small group of evergreen climbing plants found across the Northern hemisphere, in which the species ‘Ivy’ (Hedera helix) as we English folk know it lies. But what may not be that well know to people is that there are several subspecies found in the UK, the number of which changes depending on which reference you are reading, however it is generally said that 2 subspecies can be found in the UK:
Next time you’re passing some ivy on your travels, the chances are you are looking at the ssp helix, as this is the most common, but you may be excited to find something more interesting than what you just assume.
Ivy is extremely underrated by people for its value for wildlife. Many dismiss it as a vigorous nuisance, dominating areas of shade and smothering some trees to the extent that they are unrecognisable. But is this such a bad thing? Ivy has many benefits such as adding structural diversity to habitats, providing cover for animals in winter and producing fruits in winter when other food sources are low. As well as this, ivy is known as one of two primary food plants of the holly blue butterfly, a species which is doing well amongst the ranks of butterfly numbers…perhaps helped due to the success of this plant.
The most striking thing to me about ivy is it’s berries. These are poisonous to humans, but act as a really useful food source to birds and mammals which eat the berries and disperse the seeds. Certainly, ivy is a must species for any wildlife garden wanting to attract birds in the winter. Many birds, such as blackbirds and thrushes, eat the berries. As well as this, when ivy is flowering in Sep/Oct, species such as hornets, hoverflies, bumblebees, red admirals, small tortoiseshells and peacock butterflies are known to drink the nectar. Branches and leaves of ivy also provide shelter and nesting sites for birds, and a ready supply of insects can be found living on and around them.
Although often unmistakable, the one confusing thing about ivy to the amateur is that the leaves vary with age. As shown below, only juvenile leaves (non flowering) produce the characteristic lobed leaf margins which we associate with ivy, whereas the mature (flowering) leaf margins are less lobed and more undulate. I must admit this difference has fooled me before!
The important thing to remember is that Ivy is not parasitic, it only receives structural support from it’s host, so is not a threat to healthy trees. Regular maintenance such as trimming back can prevent it from becoming too dominant and suppressing other plant species.
This afternoon whilst walking my dog back from Brighton Marina, I was lucky enough to catch sight of a great spectacle seen around Brighton pier…the starling murmuration.
The starlings (Sturnus vulgaris) perform this aerobatic display of swooping, soaring and diving around autumn and winter time before they roost. It really is an amazing thing to see with swarms of starlings flying elegantly in tightly synchronised groups, like undulating clouds of black smoke.There were flocks of starlings flying in from all different directions at the same time like eager teens on their way to a party.
By putting on this display, starlings gain safety in numbers and also benefit from the extra warmth from roosting together. Now is the best time to see this display as numbers are high due to over-wintering immigrants from northern Europe.
I have recently started a new project based on an area of shingle beach nearby the Marina in Brighton, which attracted me due to its small patch of coastal vegetation growing there. Coastal vegetation is very new to me so I will be learning lots from this site and progress on identifying the flora species there has started off very slow, with only 3 species on the list so far! Shingle beaches are particularly harsh environments that are unstable in nature; therefore usually feature changing and sporadic vegetation. There is also much less competition here from other species as it requires specialist plants that can tolerate the salinity, free-draining soils and high sun exposure of the beach. The site follows this pattern, having patches of bare ground and being composed of only a few dominant species at various zones. The lower end of the site appears to be more diverse as it is further away from the coastline and therefore more protected from salt spray, however closer inspection is still needed.
The following species were identified today in the uppermost zone:
Crambe maritima (Sea kale)
A small, shrub-like perennial from the Brassicaceae family (cabbages). Very large, thick, fleshy, grey-green leaves that are wavy and slightly pinnatifid. Fruits are pea-shaped. Common on shingle beaches. The young leaves can be cooked or eaten raw.
Beta vulgaris ssp. maritima (Sea beet)
Annual/perennial from the Chenopodiaceae family (Goosefoots), closely related to the Atriplex genus. It has leafy shoots which look like basal rosettes of long-stalked leaves with cordate-diamond shaped glossy green leaves, which are wavy at the edges. The fleshy stems are square and red-striped. The flowers of this plant resemble those of goosefoot in that they have 5 tepals. The other ssp. (vulgaris) is cultivated for its root (beetroot).
Atriplex laciniata (Frosted Orache)
Another from the Chenopodiaceae family (Goosefoots), from the genus Atriplex of which plants differ from other goosefoots in having separate male and female flowers. This particular plant differs from other Orache’s in having thick, silvery, frosted-looking whitish-grey leaves. Sprawling in habit, found on shingle or sandy habitats.
So the only 2 species I got mixed up today whilst being tested on my smart targets were the dandelion (Taraxacum officinale) and smooth sow-thistle (Sonchus oleraceus). It seems silly that a species as common and well known as the dandelion would be difficult to identify but in fact there are many species similar enough to get confused with! In fact the word ‘dandelion’ refers to a group of micro species which are too difficult to tell apart in the field.
So what is the main difference between a dandelion and a smooth sow-thistle? The most prominent difference is that the smooth sow-thistle has upper leaves which clasp the stem at their base. The triangular terminal lobes of the smooth sow-thistle are also more sharp than the dandelion which shows are more blunted and curved terminal lobe. Although it is important to note that both species have fairly jaggedy leaves. Finally, the flowers of the smooth sow-thistle, although resemble those of dandelion, are much paler towards their periphery.
So there you have it, the main differences between a dandelion and smooth sow-thistle. Of course there are other types of sow thistle to be confused with, however I have not had the chance to identify them out in the field yet, but when I do I will be sure to write an article about it!
It’s been a few weeks since I last posted on here as my life has been taken over by a project I’m currently working on for my internship. However this weekend I have spent back in Somerset where I grew up and I can’t help but relax and take a break from my busy life in Brighton.
This morning I took my mother’s collie ‘Mandy’ out for a walk over the fields of Temple Cloud and couldn’t help but notice the abundance of bluebells in the area. This makes a difference from the London borough of Sutton where my I practice most of my I.D as these were our native bluebell (Hyacinthoides non-scripta). The majority of bluebells in Sutton are either the invasive Spanish bluebell (Hyacinthoides hispanica) or the hybrid (Hyacinthoides x massartiana) that it produces when it crosses with our native species.
Our native species is distinguished from the other two in having a deeper purple-blue colour, drooping raceme and having a fragrant scent.
The colour red appears quite often in angiosperms but in various shades. Think of all the pink, purple, red and blue flowers, the bright fruits and the deep shades of autumn leaves.
This is due to anthocyanin. Anthocyanin is a vacuolar pigment that occurs in all tissues of angiosperms including the leaves, stems, roots, flowers and fruits. Think of all the red berries and fruits there are that range in colour from dark blue to bright red. Strawberries, peaches, blackberries, rose hips.
The most obvious advantage of this to the plant is dispersal. Both flowers and fruits are vital for reproduction and dispersal, therefore being a bright colour helps the creatures they depend upon find them easily.
As for the stem, roots and leaves, anthocyanin seems to have an added extra advantage. It helps aid against UV damage. This is apparent in the fact that young shoots tend to show a purple tinge, as this is when they are most vulnerable to damage, when energy is being invested in growth rather than protection. This is also true for maple leaves in autumn. Before deciduous trees lose their leaves, they extract the nutrients from them and so at this time they are vulnerable to UV. Anthocyanin acts as protection enabling the tree to complete its extraction process and giving this tree its famous deep red shade in the autumn.
Here are some common woodland flowers I discovered today in Stanmer Park, Brighton. Unfortunately I could not find any in flower as we have had such cold weather, however I have included some important leaf ID tips. For help on identifying plants not in flower, refer to ‘The Vegetative Keys To Plants Not In Flower’ section of The Wildflower Key, by Francis Rose.
Key features of the family:
Creeping buttercup (Ranunculus repens)
Meadow buttercup (Ranunculus acris)
Jersey buttercup (Ranunculus paludosus)
Bulbous buttercup (Ranunculous bulbosus)
(CR) Corn buttercup (Ranunculus arvensis)
Small-flowered buttercup (Ranunculus parviflorus)
(AWI) Goldilocks buttercup (Ranunculus auricomus)
Celery-leaved buttercup (Ranunculus sceleratus)
Hairy buttercup (Ranunculus sardous)
Lesser celandine (Ranunculus ficaria)
Lesser spearwort (Ranunculus flammula)
Greater spearwort (Ranunculus lingua)
Marsh marigold (Caltha palustris)
(FPO, WO, AWI) Globeflower (Trollius europaeus)
(AWI) Green hellebore (Helleborus viridis)
(AWI) Stinking hellebore (Helleborus foetidus)
Pheasant’s-eye (Adonis annua)
(VU) Pasqueflower (Pulsatilla vulgaris)
(AWI) Wood anemone (Anemone nemerosa)
Winter aconite (Eranthis hyemalis)
(AWI) Monk’s-hood (Aconitum napellus)
(AWI) Columbine (Aquilegia vulgaris)
Larkspur (Consolida ajacis)
Traveller’s-joy (Clematis vitalba)
Common Meadow-rue (Thalictrum flavum)
Lesser Meadow-rue (Thalictrum minus)
(VU) Mousetail (Myosurus minimus)
Baneberry (Actaea spicata)
Wherever you were on Tuesday 5th March, I’m sure you would agree that it was nothing short of a beautiful spring day. The first days of sunshine in spring are always the most appreciated after a long, bitter winter like we had this year, and this day was certainly welcomed with high spirits. Luckily for the SNCV volunteers, this glorious day fell on one of their weekly task days, and better yet, was to be spent at the SNCV’s most beautiful and beloved site, Cuddington meadows.
Cuddington meadows, as Dave describes it is “the best bit of chalk grassland in Sutton” and is clearly treasured by the SNCV with respect for its ecological importance as a haven for plant diversity. But it’s not just plants that thrive here. Chalk grassland attracts many different species of butterfly to it’s rich nectar source and we were luckily enough to be joined by two species making the most of the sunshine that day, the brimstone (Gonepteryx rhamni) and the comma (Polygonia c-album).
Butterflies epitomize spring not only because we tend to see more of them at this time of year, but also because butterflies are creatures of change. Their lifecycle, referred to as ‘holometabolism’, consists of four different stages: ovum, larva, pupa and imago. The advantage of this kind of life style is that offspring do not have to compete with adults as they fill separate niches.
The ovum is another term for the egg and the female will lay these minuscule eggs upon vegetation in various different ways, depending on the species. Cuddington meadows is fortunate to harbor the rare and declining brown hairstreak butterfly (Thecla betulae), and that day we witnessed several of its urchin-shaped eggs positioned at the fork of branches on young blackthorn (Prunus spinosa) trees.
The larva are the more familiarly-named caterpillars, and once emerged will spend most of their time eating the leaves of it’s foodplant. The foodplant of a butterfly is often very specific, with most species laying their eggs on just one or two species of plant. It is at this stage which butterflies are most vulnerable to changes in land use as this often affects the distribution of vegetation. The foodplant of the brimstone is alder buckthorn (Frangula alnus) or buckthorn (Rhamnus cathartica), whereas the comma’s main foodplant is common nettle (Urtica dioica).
The pupa or chrysalis stage is when the larva undergoes complete metamorphosis into a sexually mature butterfly. Pupa are often highly camoflauged against leaves and trees and are very difficult to spot.
The imago stage refers to the sexually mature adult and this part of the butterflies’ life cycle can last from a single week to one year. The brimstone and the comma are quite unusual as they are part of a minority of butterflies which hibernate as adults and therefore live relatively long compared to other butterflies. This is also the reason for the multiple peaks in abundance throughout the year.
It’s clear to see that the life of a butterfly is extremely varied and each species is also very different from the next. Conserving butterflies is therefore a tough job and each species often needs to be targeted directly. The take home message from this blog is that is important to remember that our seasonal climate means that most of our species are creatures of change and when conserving our wildlife we must consider their needs at different stages in their lifecycle and at different times of year.
At this time of year, with spring slowly emerging around us, it can sometimes be a time of slight frustration for ecologists living in our seasonal climate. They cannot wait until the full summer sun is shining on their skin, and the nature around them reveals its full beauty and display. The early summer months are a time of great profusion and are consequently when most of an ecologist’s wildflower ID takes place. At this time, the presence of flowers makes it a lot easier to narrow down certain species, and in March this proves quite difficult, especially if you are an amateur like myself.
However, a lot of wildflower ID is actually focused on the leaves of wildflowers, and as perennial plants lay dormant through the winter of their first year, their vegetative structure is available for ID. So for those ecologists eager to get out and make their first plant ID’s of the year then go do it now! There are many leaves out there waiting and it also offers a chance to reflect upon the different lifespans of flowering plants. Below is a quick guide to leaf ID I drew up this morning. For more information of wildflower ID then I would recommend buying ‘The Wildflower Key’ by Francis Rose, an absolute essential for any budding botanist!
There are not many places you will go and not encounter trees. Trees really are everywhere. Everybody recognizes their famous body plan of a thick stem, branching limbs and towering crown, often sketched out by people all over the world as characteristic ‘background’ features. It seems that their presence is very strongly felt by their impressive structure, and with trees structure is everything.
Trees didn’t just evolve as a monophyletic group all descended from a single common ancestor. The very word ‘tree’ actually describes a type of body plan, which many different species of plant have evolved over time. The body plan is so successful that different species of plant have all blindly evolved the same adaptation. It’s similar to the fact that although there are many different religions in the world, no matter how big their differences are, they all believe in some version of a god. I’m not purposely comparing trees with god here, but come to think of it they do have a certain awe-inspiring presence. It’s not that surprising that there are examples of nature ‘repeating’ itself in this way, as there are certain ‘limits’ to evolution which I will discuss later in the article. The technical term for this type of pattern is convergent evolution, where similar features are found in species with separate lineages.
So what is it about the body plan of a tree that is so iconic and successful that people and plants are reproducing them everywhere? First we must consider the 3 basic needs of a tree – light, nutrients and water. It is obvious when looking at the structure of a tree that it is adapted well to these 3 basic needs. It has a big crown of leaves to uptake light for photosynthesis and a complex network of roots to absorb nutrients and water from the soil. The size of the tree is a different matter. Not only our trees driven by these 3 basic needs, but they are also driven by the competition for these needs with other species of plant. Whereas fast-growing herbs die back every year, trees maintain a permanent woody structure, a permanent platform from where they can grow their leaves every year above everything else. This is all straightforward stuff, but what is interesting is that trees are products of a process that we call succession.
Ecological succession is the ‘change in species composition of an ecological community over time’ and it plays out with a fairly predictable course. Take a patch of bare ground. Studies of succession have told us that the first species to colonize the patch will generally be fast growing, well dispersed, so-called ‘r-selected’ species. This is because these are quick enough to take advantage of the light, nutrients and water available in the patch. However, over time there will be a transition to slower growing species that invest more energy into growth (like trees), the so-called ‘k-selected’ species. This is because, as they slowly grow taller than the other plants, they cast out shade over the patch and suppress the growth of the less shade-tolerant species that were present before. It’s a classic case of the tortoise and the hare, where the slowest eventually wins the race!
As I mentioned before, there are limits to evolution but these limits are roughly circumstantial. The ‘end’ type community of succession in the UK is predominantly woodland, a community of trees of various heights and shapes all adapted to life in different layers of the canopy and all driven by those 3 basic needs – light, nutrients and water. This community is referred to as a climax community because there is little despite stochastic effects that will change it any further. The community of trees would have altered the environment around them enough to make competition with them almost inevitable. That is until a great storm or disease breaks out and creates a gap in the canopy. The gaps would then flood with light, nutrient and water levels would increase in the soils and those r-selected species we talked of before would quickly carpet the floor with spectacular colours, desperate to pollinate before they suffer the consequence of living such a fast life.
However what I meant by ‘limits’ to evolution is that succession always seems to have a limit, a community or structure which cannot grow beyond what it is, it can only revert to earlier stages. This is because there are limits to an organisms ability to evolve new structures in competition with others. There is only so much light, nutrients and water available and only so much energy you can invest into growth until it compromises on survival in some way. Plants are slaves to their body size and their ability to reach light and reproduce before their time runs out. It’s no wonder we have terms for different plants based on their longevity – annuals, biennials, perennials! Plants are structures, different structures with different heights, blocking out different levels of light. Interestingly, no structure or species has been so successful without altering their environment enough to make competition from other species too tough. Just take a look at ourselves.
Common snowdrop (Galanthus nivalis) is one of the first flowers to carpet the floor in spring and it is for this reason it is deemed the flower of hope. These featured above were pictured just earlier today after a few patchy days of sunlight. The snowdrop is an introduced species which is now naturalised in the UK. It is a perennial plant which grows from a bulb and flowers between January and May. It has 2 long lanceolate leaves and a single leafless flowering stalk which bears a drooping bell shaped flower which gives the flower it’s delicate beauty. This beauty can be deceiving however as if eaten in vast quantities it is poisonous to humans.
A few weeks ago I received the fantastic news that the Sutton Nature Conservation Volunteers (SNCV’s), had accepted me onto their ‘Biodiversity Graduate Training Programme’. Unlike everybody else who dismissed the opportunity as‘stupid’ or ‘crazy’, I was quite happy to be accepted onto a voluntary placement which would take up 3 days of my week, require 2 hours of commute everyday and also leave me financially struggled. This is the reality facing a lot of graduates who are looking for a career in wildlife conservation and I am no exception to this fate. However the competition out there is fierce and the way I see it is that I am young, hard-working and have few enough responsibilities to be able to accept an opportunity like this, and by the end of it I will be in a good position to qualify for the paid positions I so frequently receive rejection letters from. Just a few hours ago this evening I received a call back from an interview I had just yesterday with the London Wildlife Trust, which was to regretfully inform me that I hadn’t been successful. Despite my professional manner, they explained, the other applicants just had more experience than I had. Although disheartening, it was kind of a relief that I wouldn’t have to make a choice between the two positions, as although this one was paid, it didn’t provide the diversity of training that the SNCV’s were offering. The outcome of the interview just reinforced what I knew already-not even a first class honours degree will get you anywhere in conservation without decent experience to back it up.
But there was something extra special about this role that had attracted me towards it – Biodiversity Gardens. Biodiversity Gardens is a 2-year HLF project that aims to increase biodiversity in people’s gardens through extensive surveys and gardening advice. Immediately my head was filled with the words: habitat loss and fragmentation, evolution, extinction, scale, landscape, species, diversity. These are all concepts within the field of ‘biogeography’, an exciting branch of ecology that looks into the patterns of species distribution. This project had stimulated the island junkie in me. So what has Biodiversity Gardens got to do with islands? Or what has your back garden got do with the exotic islands of Barbados or Borneo?
As most of us are aware, species are becoming extinct at a much faster rate than is the norm. This is largely due to habitat loss and fragmentation. The cause, human civilization. I stress civilization, as Homo sapiens in their ancestral hunter-gatherer form lived a relatively sustainable life. It’s ever since the dawn of agriculture thousands of years ago, that humans have moved to a more civilized, but less sustainable life. In a similar way to other ‘accelerative’ ideas such as tool making and language, agriculture opened up opportunities for people; it allowed our population to grow exponentially as we learned how to manipulate the environment around us to support our needs. Nowadays the iconic British landscape as we know it consists of vast expanses of farmland with only remnants or ‘islands’ left of once widely abundant habitats, such as woodland, meadow or scrubland.
It is here which lays the connection between Biodiversity Gardens and islands. In our patchy landscape, remnant patches of habitat are synonymous to islands, in that an inhospitable matrix surrounds them. They are often compared with continental islands, like Barbados and Borneo, which were formerly connected to the mainland via a land bridge. This is because, like continental islands, they were once a part of the mainland, therefore are likely to contain a small sample of species present on the mainland, rather than colonizers. Such species are called relicts. It is known through the study of islands, that island size and isolation has a great influence on its rate of species extinction. The smaller and more isolated the island, the greater its rate of extinction, and this concept can be applied to our thinking of habitat loss and fragmentation. If we can find ways of increasing the size and decreasing the isolation of habitat then we can reduce the rate of species extinction. As gardens make up a large part of the green space left in our landscape that is free from intensive agriculture, increasing biodiversity in gardens is a great way to reconnect the landscape, providing links and even whole habitats between remnant patches. Increasing size and decreasing isolation of habitats, thus decreasing extinction.
The island analogy is a neat and simple comparison, which is responsible for introducing the concept of time and space to our thinking on habitat loss and fragmentation. However, modern day biogeographers aren’t happy with this simplicity anymore. There is now much more focus on how remnants are unlike islands than vice versa. It’s a shame as I think there is only clarity in such simple concepts, but as ever ecologists are determined to understand the complexities of nature that are so unattainable. Maybe it was the transition from the island concept to the island theory by MacArthur and Wilson that raised ears amongst the critics. In fact we shouldn’t compare woodland remnants to continental islands, as they are islands in their own right. It is our stereotype of islands being small patches of land surrounded by water that deems this comparison untrue. All islands have a matrix, be it water, grassland, road, and they all have varying levels of hospitability for different species, so when considering islands, it is vital to consider which species you are relating it too. A rock that sits in a stream may be an island for some species of fungi or moss but this rock may merely be a resting place for an otter passing through the stream.
Nevertheless, I immediately recognised this project as something that would be extremely worthwhile. The only way to help our threatened species survive in our patchy landscape is to reconnect it. Nature reserves do their best to help this but our gardens also play a part, especially in suburban areas where they may make up the majority of green space available. Biodiversity Gardens therefore has a lot of potential and I am excited to know that I will be a part of it. If the SNCV’s are able to find enough landowners to cooperate, not only will their gardens become miniature wildlife havens, but also more people will be educated and inspired by the wildlife in their gardens and the connection between wildlife and people will be made again, as it was before the dawn of agriculture.
So there is a lot to look forward to in 2013, a whole new year with exciting prospects! Although I may not be island hopping on the Malay Archipelago like Alfred Wallace did on his journey to discovering evolution, I can still find a way to feed my addiction for islands….or at least until I find the money to fund such a journey?
For the past few weeks I have been lucky enough to re-visit the University of Brighton where I undertook my undergraduate degree, to assist with a project on the European hedgehog (Erinaceus europaeus). A current student of Ecology and Biogeography and ex-classmate of mine, Christina Kimbrough is undertaking her dissertation on the survival of hedgehogs post-rehabilitation. The Royal Society for the Prevention of Cruelty to Animals (RSPCA) initiated the study in response to the numbers of hedgehogs bought in for rehabilitation. Although you may think most hedgehogs bought into the RSPCA may be the injured soldiers back from battle with England’s roads, actually a lot of hedgehogs are bought in because they aren’t gaining enough weight for hibernation. They are so common in fact, the RSPCA have gone to the lengths of abbreviating a term for them, ‘TSTH’ meaning ‘Too Small To Hibernate’. Usually TSTH’s are taken in over winter and rehabilitated for release in spring, however there are more hedgehogs than pens to keep them in and money to feed them with. To help reduce such costs, there have been attempts to hibernate hedgehogs in captivity as well as releasing them into the wild once in hibernation. However the former still costs way too much and the latter is currently being looked into at the University of Reading (see http://www.rspca.org.uk/ImageLocator/LocateAsset?asset=document&assetId=1232728996691&mode=prd). Although the final outcome of the study is yet to be defined, its intention is to look into speeding up the process of rehabilitation and releasing hedgehogs in late autumn to see if they are able to adjust and enter hibernation in the wild.
So based on current research what are their chances of survival? Well several studies have actually shown that hedgehogs do very well after rehabilitation and even orphaned hedgehogs that have been in captivity for a long time can quickly adapt to life in the wild. However this is based on studies where hedgehogs were released in spring, not in autumn when they are about to enter hibernation. At this time, hedgehogs should have a good chance of survival if they manage to adjust to their surroundings quickly and find a place to hibernate before loosing too much weight. But this part is crucial. The loss of weight threatens them the most as many studies show that on release, hedgehogs loose weight initially but regain it once they have adjusted to their new environment. Releasing them at this time of the year means that there will be fewer foods available and so the hedgehogs will need to find a safe place to hibernate quickly before their reserves decline. I didn’t have the knowledge to ask this when I was working with Christina, however I expect that a key feature of this study will be to release hedgehogs above the minimum weight (450g) so that they are compensated if weight loss should occur. For more information on this see ‘The new hedgehog book’ by Pat Morris (ISBN: 9781873580714).
I must admit I was a little jealous of Christina when I found out about her project, as not only did she get to handle the species she was studying (my dissertation was spent on my hands and knees searching for hazelnuts gnawed by dormice without the slightest chance of even seeing one), but she got to play around with some awesome radio tracking equipment courtesy of the RSPCA! The equipment used to track the hedgehogs included a radio transmitter, receiver and aerial. The transmitter is the piece you attach to the hedgehog; the receiver is the tool used to tune into frequencies and listen to them and the aerial is used to catch the signal. Christina was kind enough to invite me along to see the transmitter being fitted to the hedgehog, which I will now make an attempt to recall. Firstly, the hedgehog was secured into a position by holding it firmly in one place, then a small patch of its spines were trimmed along the vertebral line on its dorsal side (see pictures below). You have to be careful that the hedgehog doesn’t erect its spines at this point so that the patch isn’t lost! Meanwhile the glue to attach the transmitter was being prepared which was some sort of dental acrylic that I quickly caught whiff of, a very potent smell and Christina quite rightly pointed out its similarity to the smell of a nail salon. The glue was then smoothed onto the bottom of the transmitter, which was then placed onto the freshly trimmed patch of spines and held firmly for a few minutes whilst it dried. The hedgehog was then ready for release, which was undertaken at a site not too far from the University in open grassland with woodland adjacent to it-perfect for hedgehogs.
When it came to tracking the hedgehogs, a tracking team would head out to the release site with the receiver and aerial and tune into a particular transmitter (each transmitter had its own frequency so you can track more than one hedgehog). The aerial is then attached to the receiver and held up horizontally to catch the signal. It is a good idea to start of with a 360-degree turn to begin with and listen out for the beeps, which tell you where the signal is. Once a signal is located you can ‘home’ in on it by steadily moving the aerial until you get the strongest signal, or the loudest beeps. This is then repeated so you have a signal from several different directions to enable triangulation, and Christina recommends 3 for this. Although triangulation is prone to error it is often the only method you can use in scrubby terrain, especially when hedgehogs are burrowed under trees finding places to hibernate. It is always a good idea to brush up on your tracking skills before going out as there are many things to consider when using the equipment. I would discuss them here but I’ve realized that this article is getting rather long, but you can find a good guide on the Biotrack website (http://www.biotrack.co.uk/), as well as information on some of the equipment. Biotrack also mention that you can download a programme called Ranges8 to analyse tracking data with, and after a quick browse of the site I found out there is a demo version free of charge which is perfect for mucking around with if you’re interested (http://www.anatrack.com/home.php)!
Swiftly moving on before I delve to deeply into the subject, the main idea of the project is that the radio tracking equipment can be used to track the movements of the hedgehogs so that Christina is able to keep track of how they are doing through the winter and see how many survive until spring. With any hope, the hedgehogs will do well, although we would be naïve to expect them all to survive! Unfortunately Christina was unable to capture any wild hedgehogs to use in comparison but the study will at least be a starting point and Christina is even thinking about using it as a pilot study in preparation for an MRes or PhD, which could be interesting. I also plan to carry on helping out with the study so I promise to write another article on it if the data reveals any surprises.
A lot of questions in ecology are to do with a species’ evolution, and evolution is distinctly concerned with the survival and reproduction of genes in their environment-be it an organism or a woodland. Although natural selection may refer to a gene’s and hence species’ survival, it goes hand in hand with sexual selection, which is concerned with its reproduction. There is no point for any gene to survive if it does not reproduce, a stark fact that is met by some male spiders in the genus Latrodectus, who are eaten by the female after copulation to give the offspring a better chance of survival. With this in mind, I feel it must be important to understand the very process that drives the great diversity of life we see today-inheritance. But first it might be useful to point out that all living organisms reproduce, but not all sexually reproduce. For now I shall explain inheritance in sexually reproducing species, particularly humans.
Consider a human that is made up from the building blocks of life-cells. Within each cell is a nucleus containing DNA (deoxyribonucleic acid), which carries the information needed to ‘function’ the human. This DNA is in the form of chromosomes, 46 altogether in each human somatic cell. Each chromosome is a long strand of DNA made of two chromatids joint together in the center by the centromere (see figure below). As humans are diploid (they inherit genes from both parents), there are two sets of chromosomes (one from the mother and one from the father), and these sets ‘hang out’ with each other’s matching chromosome to form homologous pairs (23 altogether). Each homologous pair shares the same size shape and function. It is quite confusing as the chromosomes themselves look like pairs, but a chromosome pair refers to two whole chromosomes that share similar characteristics (see figure below).
It is on the chromosomes, where the genes are situated. Each chromosome contains many genes, each of which contains information for different traits in an organism e.g. eye colour. Now here is the tricky part. An organism’s entire set of genes is called its genome, but not all genes in the genome are expressed in an organism. For every gene, there are several alleles, which are variations of a particular gene, and only one of these is expressed in an organism. Again, as humans are diploid, there are 2 alleles (one from each parent) per gene. The alleles for a particular gene are located at the same position or locus of a homologous pair (see figure above). An example of a gene is eye colour, and variations (alleles) of this gene could be green or brown. A person could have both these alleles but they will only express one of them. The collection of genes (or more rightly alleles) that are expressed is called an organism’s phenotype. So what are the other genes doing if they are not expressed? They are essentially getting a free ride on the back of the phenotype. To answer this we must understand what goes on during the process of inheritance.
So how do we inherit genes? Through reproduction of course, and this process begins with meiosis. Earlier I mentioned that humans have 42 chromosomes in every somatic cell. Somatic cells are the cells that make up the human body, but these exclude gametes, which are the other type of cells we find in humans and they are involved with reproduction. It is the gametes, which are responsible for passing genes on to the next generation. Each gamete-be it a spermatozoa or an ovum (male or female gamete), contains half the number of chromosomes than somatic cells, as humans only ever pass on half of their genes to the next generation. The other half comes from a sexual partner. This halving of the chromosome number to produce gametes is called meiosis.
Meiosis is a rather complicated process, which I will not describe in detail here but the main gist of it is that there are two divisions (meiosis I and II). The first division is the splitting of a homologous pair of chromosomes and the second is the division of each chromosome into four chromatids. The final result is four haploid nuclei. It is actually more complicated than that but the most crucial point is this. During these divisions, mixing occurs between the chromosomes so that the final four haploid nuclei contain a mixture of genes from each original homologous pair. During fertilization, a gamete from the opposite sex will fuse with the gamete, which restores the amount of chromosomes in the offspring. The offspring therefore can be said to have a mixture of genes from both parents, which is also a mixture of genes of each parent’s own genes. So why do we pass on only half of our genes and why are these genes not always the ones we express? Surely if they worked for the parent, they should work for the offspring too? Doesn’t this go against the whole selfish gene (see Dawkins, The Selfish Gene) concept? Well no because with the case of phenotypes, this is just another way of introducing variation and hence adaptability into individuals without having to lose genes. But we can’t ignore that at some point it in our evolution (by this I am not referring to human evolution but the evolution of life in general), it benefited one of our ancestors to sacrifice half of its genes and replace them with somebody else’s genes. Shouldn’t the selfish genes want a good chance of being passed on? Why did sex evolve?
This is a very complicated question, which there are many theories for, and I will not attempt to answer but just open up a way of thinking about it. Lets start with thinking about the alternative-asexual reproduction. This does exist in nature but to a lesser extent in the animal kingdom. With asexual reproduction, there is no reliance on another individual to reproduce and all of an individual’s genes may be passed on. If this is true then can there still be different species of asexual beings, given that species are defined as those that are reproductively isolated? This begs us to look deeper into the concept of a species. We may be able to distinguish a monkey from a seahorse because they look totally different. But why do they look different? How are new species formed?
Most new species are formed by an initial barrier to gene flow, such as a river separating a population of individuals. Whether these two populations were asexual or sexual, they would still eventually form different ‘species’ through natural selection. Although ‘species’ in this sense refers to groups of organisms that share certain characteristics, as opposed to those, which can only interbreed with each other. Sexual reproduction in this sense provides an extra barrier to gene flow-it helps form species! It concentrates evolution into one type of organism instead of working on individuals. Sexual reproduction forms gene pools instead of genomes, which are more adaptable, more changeable, more varied. Genes have formed organisms, which have in turn formed species. Genes have now become so hidden behind their ‘machines’; it is easy to forget they are there!
The benefits of sex are quite obvious for species or individuals but less obvious from a selfish gene point of view. Have genes now had to account for the organisms and species they have built? This aside, although sexual reproduction might be difficult to explain, it is undoubtedly shaped the evolution of life in so many ways. Without sex, the world would be a less colorful place, as sexual selection is the driver of so many fascinating traits, which the peacocks tail, is only one example of.
The following books were used to help make this article:
Mastering Biology (3rd edition), by OFG Kilgour and PD Riley.
Introducing Genetics, by Alison Thomas.
Throughout this blog, I shall often look into the past to help explain things going on in the present, and this article is intended as an introduction to this reasoning as well as some important facts that will make my future articles more comprehendible. If you are an ecologist, like myself, you might wonder someday why anybody bothers to study nature, as it is so unpredictable. I recall during my undergraduate degree, having spent the first two years studying theoretical ecology, being told in my final year, “Just take it all with a pinch of salt”. However, although this may ring some truth, I think the problem here is misinterpretation. Every single organism on this earth is the product of years of evolution. It wouldn’t exist unless it could do so in it’s natural environment. These organisms do not have a purpose they are simply a consequence of the process of natural selection. Because of this, quite fascinatingly, but nonetheless ‘blindly’, organisms have become adapted to their environments. It is the selection pressures in an organism’s environment that drive natural selection and it is these pressures that ecologists are often trying to understand.
What I am trying to say is there is always a reason why things are the way they are. To explain why a giraffe has such a long neck is a question into its ecology or what its purpose is in its daily life. A single giraffe in present time however, is just one of many giraffes that have lived in the past. Its long neck certainly did not crop up during the lifetime of a single giraffe in the present-that would go against everything we epitomize a giraffe to be. The giraffe’s neck is the product of years of evolution with its natural environment, as species are products of their environment. Therefore to explain why a giraffe has a long neck, we must look at the selection pressures that acted on it during its evolution – we must look to the past. I think the problem with studying the ecology of a species is actually the misinterpretation of findings. For example, a study might conclude that giraffes prefer to eat the leaves of Acacia trees. However this does not mean that all giraffes only eat Acacia trees, and that they won’t eat other trees if they need to (I might just point out here that some humans have been known to become cannibalistic in survival situations). It just means that the majority of giraffes eat these leaves because it has benefited them in the past. We must remember although we define groups of organisms as different ‘species’, every organism is essentially its own species; the only thing that binds them together is their interdependency to reproduce. We must also remember that species are always evolving and although the past can explain the present, it is the selection pressures of today’s environment that will determine the future ecology of different ‘species’.
To accompany this article, I present here a diagram of the geological timescale courtesy of the U.S. Geological Survey, which will be useful when referred to in the future. For now all I will explain is that this scale begins at 4.5 billion years ago at the birth of our planet and ends in the present. The past 4.5 billion years of Earth’s history is broken down into periods of time that relate to significant changes in the Earth’s geology.