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Darwin and Downe Bank: The Wardens' Tale


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Darwin and Downe Bank: The Wardens' Tale

  1. DARWIN’S ‘ENTANGLED BANK’ AT DOWNE Photographs and presentation by John and Irene Palmer, Hon. Wardens of Downe Bank © Notes by Irene Palmer The Wardens’ Tale
  2. Downe Bank ~ Darwin’s ‘Entangled Bank’ It is interesting to contemplate an entangled bank, clothed with plants of many kinds, with birds singing in the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and so dependent on each other in so complex a manner, have all been produced by laws acting around us. Hangrove ‘ Orchis Bank’ Coppice and scrub Bee Orchid White Bryony Primroses
  3. <ul><li>Inspired our understanding of biodiversity and ecology </li></ul><ul><li>Provided evidence for the driving forces of evolution </li></ul><ul><li>Opened vast avenues of scientific endeavour world-wide </li></ul>Many of his most important insights originated within the ‘Darwin at Downe’ nominated World Heritage Site. The Origin of Species has more references from the Downe countryside than from anywhere else Darwin visited. Many of the species he studied still grow there. Darwin’s insights from his studies in the North Downs of Kent
  4. The origins of ‘The Origin’ We shall not cease from exploration And the end of all our exploring Will be to arrive where we started And know the place for the first time. T. S. Eliot Four Quartets Mojave Desert California Downe Bank, Kent Santa Fe, Galapagos John Hughes This tree-like cactus, Opuntia echios syn. myriacantha var. barringtonensis, takes its name from Barrington Island, Darwin’s name for Santa Fe. These giant cacti inhabit islands that have, or did have, populations of tortoises. Sturdy thorns on the lower part of its trunk suggest competition for light with the surrounding vegetation and with browsing tortoises were possible factors in their evolution. Wild clematis, Clematis vitalba is typically found on chalky soils. This climber is also called old man’s beard because of its white fluffy seeds. It was familiar to Chaucer’s pilgrims as they made their way to Canterbury; they called it travellers’ joy because it grew beside the North Downs’ ancient track-ways. It festoons trees and bushes with thick ropes, perhaps reminding Darwin of the lianas of the tropical jungles when he came to Kent. A plant on the edge of the desert struggles for life
  5. A traveller should be a botanist, for in all views plants form the chief embellishment. Group masses of naked rock even in the wildest forms, and they may for a time afford a sublime spectacle, but they will soon become monotonous. Paint them with bright and varied colours, as in Northern Chile, they will soon become fantastic; clothe them with vegetation, they must form a decent if not beautiful picture. The Atacama Desert, Chile A traveller’s view
  6. Downe Village Village about 40 houses with old walnut trees in the middle where stands and old flint church and the lanes meet. C. Darwin. Extract from a letter written by Charles to his sister Catherine, July 1842. He settled at Down House later that year with his young wife Emma. Winter scene of the Queen’s Head public house in the centre of Downe village between Walnut Tree House and the George and Dragon Inn A terrace cottage built of local flint and brick in the eighteenth century Walnut Tree House and Cottage, originally a fifteenth century Kentish Wealden Hall House was occupied in Darwin’s time by the village builder who helped him construct his laboratory. A silhouetted cross in the churchyard is symbolic of Darwin’s conflict with the Church. A sundial memorial on the tower below the spire is dedicated to Darwin. In Darwin’s time the village was called Down; ‘e’ was added later to avoid confusion with Co. Down in Ireland
  7. Francis Darwin recalled in his autobiography of his father I have heard my father say that the charm of this simple little valley helped to make him settle at Downe. It is a good,very ugly house with 18 acres, situated on a chalk flat, 560 feet above sea. There are peeps of far distant country and the scenery is moderately pretty: its chief merit is its extreme rurality. Downe Valley Down House Down House
  8. Darwin’s Garden Darwin’s experimental plots and greenhouse Wildflowers ( Verbascum sp. ) growing in the flower beds Dionaea muscipula Venus fly trap. Darwin grew this American carnivorous plant in his greenhouse Linaria vulgaris Linaria vulgaris (peloric) Darwin carried out countless experiments here. The plants in rows in the foreground are Primula veris. Back-crossing common toadflax produced regular (peloric) flowers, indicating they were ancestors of irregular flowers and evolved with insects. Dicentra spectabilis He had a great delight in the beauty of flowers according to his son Francis
  9. Lawn fungi at Down House Display of waxcaps on the lawn at Down House photographed November 1979 Hygrocybe puniceus Hygrocybe calyptraeformis Hygrocybe psittacinus Hygrocybe ceracea Hygrocybe coccinea Photographs of Down House garden reproduced with kind permission of English Heritage. These photographs of fungi are currently displayed in Down House. Clavulina incarnata
  10. Downe Valley In 1855 Darwin made the first study of plant biodiversity in Great Pucklands as he explored the principle of divergence. He identified and listed a total of 142 plants over the course of the year, assisted by his children’s governess Miss Thorley. He identified his first grass during this survey. I have just made out my first grass, hurrah! hurrah! I must confess that fortune favours the bold, for, as luck would have it, it was the easy Anthoxanthemum odoratum [sweet vernal grass}: nevertheless it is a great discovery. This grass gives a lovely scent to new mown hay. The survey was repeated in the summer of 2005 revealing the total number of species has declined since Darwin’s time, probably due to nutrient enrichment. The Big Woods Anthoxanthemum odoratum The Sandwalk Dactylorhiza fuchsii Sweet vernal grass Common spotted orchid
  11. Darwin’s neighbourhood today A typical local bridle path Saltbox where the Darwins had family picnics A London Wildlife Trust Nature Reserve today Darwin’s Musk Orchid Bank Holwood House Aesculus hippocastanum The Lubbock Memorial Horse chestnut trees planted in Darwin’s time can still be seen in the grounds of Holwood
  12. Keston Common Scene at Keston ponds in autumn Keston bog with cotton grass flowering Erica tetralix Sundew, Drosera rotundifolia Cross-leaved Heath Cotton Grass Darwin studied the sticky leaves of sundew plants and commented - glands sometimes as many as 260, exposed during the whole day to a glaring sun. Eriophorum angustifolium
  13. High Elms The Lubbock family owned this estate for several generations but their former mansion was destroyed by fire. Charles Darwin met Sir John Lubbock 111 here and became a mentor of his son, also called John, who eventually became the fourth baronet. The stately elms were characteristic of the English countryside and were once a feature of the estate but have since become victims of Dutch Elm Disease. Today High Elms is a Country Park owned by the London Borough of Bromley and is linked with the Downe Bank Site of Special Scientific Interest to ensure the conservation of its rich diversity of wildlife. Avenue of beech trees Pond with plants of purple loosestrife, Lythrum salicaria The Clock House Black wood ant Illustration from Ants Bees and Wasps , by John Lubbock
  14. we are absolutely at the extreme verge of the world The charm of the place to me is that almost every field is intersected by one or more footpaths. The country is extraordinarily rural and quiet with narrow lanes and high hedges and hardly any ruts. Rural scenes at Downe These rural scenes that charmed Charles Darwin still exist today. Greenhill and Downe Valley Hangrove Hill A footpath along the edge of a typical dry valley
  15. Squinancywort Yellow or Hay Rattle Common Bird’s-foot-trefoil Chalk Milkwort Fairy Flax Common Rock-rose Common Eyebright Wild Basil Chalk flora biodiversity . . . I was pleased with the diversified appearance of vegetation proper to a chalk district . . . Darwin. ‘Autobiography’ in Life and Letters (1887, p. 78) Helianthemum nummularium Asperula cynanchica Euphrasia nemorosa Rhinanthus minor Linum catharticum Clinopodium vulgare Polygala calcarea Lotus corniculatus
  16. Butterfly biodiversity on Downe Bank Brown Argus Small Tortoiseshell Gatekeepers Green Hairstreak Peacock Ringlets Common Blue Dingy Skipper Common Blues mating
  17. Darwin studied the local geology when he came to Downe, following the routine he had developed during the Beagle expedition. The flat summit land is covered with a bed of stiff red clay . . . Abounding with great, irregularly shaped unrolled flints, often with the colour and appearance of old bones. He described the geology in a short essay in he began in 1843 The red clay when ploughed shows the white-chalk, which shades away lower in the valley as invisibly as a colour laid on by a painters brush. A General Aspect 1843 View from the edge of the North Downs Clay-with-flints soil on the top of the North Downs
  18. A General Aspect 1844 The flowers Darwin described in this essay still grow on Downe Bank The first period of vegetation, and the banks are clothed with pale blue violets to an extent I have never seen equalled, and with primroses. A few days later some of the copses were beautifully enlivened by Ranunculus auricomus, wood Anemones and a white Stellaria. Again, subsequently, large areas were brilliantly blue with bluebells.-The flowers here are very beautiful. Ranunculus auricomus Anemone nemorosa Viola riviniana Primula vulgaris Stellaria media Dog Violets Common Primroses Wood Buttercups or Goldilocks Wood Anemones Greater Stitchwort Endymion nom-scriptus Bluebells
  19. The fields to the East of the house were pleasant & led to a steep wood called Hangrove - very full of primroses. Hangrove - whole ground beautiful blue in large patches of Viola canina – [the old name]. It is near where Cephalanthera grew - where so many primroses have grown this spring. [The Cephalanthera Darwin mentioned was Cephalanthera damasonium, an orchid commonly known as White Helleborine] Dog violets on Downe Bank Hangrove Wood in April Cephalanthera damasonium Viola riviniana Viola reichenbachiana Primroses, Primula vulgaris
  20. George brought me 17 flowers (Oxalis) from so many plants near Hangrove Hangrove Wood in May Bluebells carpet the woodland floor in May. Darwin identified grasses here and studied the structure of the flowers of wood sorrel, Oxalis acetosella, Oxalis acetosella Melica uniflora Bluebells, Endymion non-scriptus
  21. Marked some bushes (Spindle) coming out of Hangrove. Downe Bank in autumn Spindle fruits, Euonymus europaeus Scene photographed at north end of Hangrove and Downe Bank with spindle bush, Euonymus europaeus in foreground Two forms of spindle flowers, Euonymus europaeus Male or hermaphrodite Female
  22. Darwin’s two big ideas He drew a branching tree to show species had evolved from a common ancestor, unlike Linnaeus who believed related species were created according to the account in Genesis. Primrose Cowslip False Oxlip True Oxlip A book by Malthus gave him the idea that competition resulted in natural selection and this was the mechanism of evolution. He shared this idea with Alfred Russel Wallace. They published a joint paper in 1858 . Too many offspring Struggle to survive Individuals vary Characters are inherited Primula vulgaris Primula veris Primula elatior P. vulgaris x veris
  23. I can remember the very spot in the road, whilst in my carriage, when to my joy the solution occurred to me; and this was long after I had come to Downe . The solution, as I believe, is that the modified offspring of all dominant and increasing forms tend to become adapted to many and highly diversified places in the economy of nature . Variations between individuals in a species allow the fittest to adapt to their environment Darwin’s gleam of light
  24. The web-of-life Our conservation efforts are based on Darwin’s insights into complex interrelationships in the web-of-life that enable us to foster ‘linkage’ <ul><li>Darwin discovered only bumble-bees pollinated Red clover and Heartsease. He related this observation to a report by the hymenopterist Col. H. W. Newman that bumble bee nests were more numerous near towns and villages where cats predated the mice that raided their nests. ( 1851 Proceedings of the Entomological Society) Darwin then reasoned that: </li></ul><ul><li>The presence of many cats in a district might determine the numbers of red clover and heartsease and deduced that if bumble-bees became extinct these flowers might disappear. </li></ul><ul><li>He encouraged his children to mark bumblebees with flour. They helped him track patrolling male bumblebees as they alighted at ‘buzzing places’ and followed a fixed flight path. </li></ul>Red Clover & Bumblebee Viola tricolor Heartsease or Wild pansy Field mouse Billy The Kid Trifolium pratense
  25. Biostructure of coppice woodland species Male flower Hazel Female flower Hazel Hazel nuts Toothwort Encoelia furfuracea Wood Mouse Dormouse R. Francis R. Francis Moschatel Clouded Magpie Moth White-letter Hairstreak photographed at High Elms S. Davis Marsh tit young nesting in a dormouse box during monitoring so different from each other, and so dependent on each other in so complex a manner Corylus avellana (fruits ) Lathraea squamaria Adoxa moschatellina on Downe Bank
  26. Cudham Valley ~ view from High Elms to Downe Bank Darwin collected seeds here to grow in his garden from naturally hybridising wild plants. The main plants he studied were Verbascum sp., and Anagallis sp. (Mulleins and Pimpernels). Darwin compared wild and cultivated plants in his garden These species are colonisers of disturbed land Anagallis arvensis Anagallis arvensis Verbascum thapsus Verbascum lychnitis Verbascum nigrum Scarlet pimpernel flowers are usually red, sometimes they are blue, although they are the same species. These photographs were taken in Cudham Valley where Darwin collected seeds of these plants. Great Mullein Dark Mullein White Mullein
  27. No little discovery of mine ever gave me so much pleasure as the making out the meaning of heterostyled flowers. The driving forces of evolution ‘What sexual selection explains, better than natural selection, is diversity that seems arbitrary’ Richard Dawkins Dimorphic flowers of Primula vera (above) and P. vulgaris (below) Trimorphic flowers of Purple Loosetrife Darwin discovered that sexual reproduction was crucial for evolution and heterostyly ensured cross-fertilisation. A Eureka moment with two common local species! Lythrum salicaria
  28. Bryonia dioica Male B. dioica Female Silene dioica Male S. dioica Female Strategies to ensure cross-fertilisation Sexual reproduction enables variations in the characters of both parents to be passed to future generations. Plants have evolved different strategies to ensure cross-fertilisation. Dioecious species achieve this with male and female flowers on different plants. Glechoma hederacea Male G. hederacea Female Cross section of female flower Silene dioica (female) White Bryony flowers Red Campion flowers Ground Ivy flowers
  29. . . . tendrils: their irritability is beautiful, as beautiful in all its modifications as anything in Orchids. I have more than once gone on purpose during a gale to watch a Bryony growing in an exposed hedge . . . the Bryony safely rode out the gale, like a ship with two anchors down . . . Tendrils became Darwin’s ‘hobby horse’ Darwin studied local climbing plants. He discovered they had the power of movement and tendrils had evolved from leaves Hops from the hop fields of Kent were the first climbers Darwin studied. They climb aided by tiny ice-axes on their stems. Climbing plants at Downe Bryonia dioica, White Bryony a tendril climber Humulus lupulus, Hop Tamus communis, a twiner Darwin’s son Francis described how black bryonies twined together like snakes in the hedgerow Black Bryony photographed in the hedge opposite Down House Drawing from Darwin’s book on climbing plants
  30. I am a complete millionaire in odd and curious little facts ! Floral structure ensures cross- fertilisation ‘ sleep movements’ of leaves (nyctitropism) Wood sorrel has a fail-safe system of seed production in case insect pollination fails in spring (fruits of cleistogamous flowers) Insectivorous plant studies Mistletoe fruits dispersed by birds Plumed seeds of rosebay willowherb dispersed by the wind Bees pierce the dog violet’s spur to obtain nectar Arum maculatum Viscum album Viola riviniana Drosera anglica Chamaenerion angustifolium Digitalis purpurea Foxglove flowers are adapted for cross-fertilisation by bumble bees Oxalis acetosella Oxalis acetosella
  31. Rough Pell Darwin’s son Bernard recorded this was the proper name of ‘Orchis Bank’. Randal Keynes located Rough Pell on the 1847 Tithe Map and found it coincided with Downe Bank; further valuable proof of its authenticity. No single point in natural history interests me so much as the self-fertilisation of the Bee Orchis <ul><li>In 1859 Darwin published The Origin of Species </li></ul><ul><li>In 1860 he suddenly made ground-breaking botanical discoveries. He followed two themes and published 6 books on plants: </li></ul><ul><li>The function of flowers, especially adaptations for cross-fertilisation. His first book concerned the fertilisation of orchids. He followed this with other studies of flowers. </li></ul><ul><li>The sensitivity of plants. The subject led to further books on climbing plants, sleep movements and insectivorous plants. </li></ul>Charles Darwin called Downe Bank ‘Orchis Bank’; it was just ½ a mile from his home and it became crucial to his studies from 1860 onwards. Bee Orchid Ophrys apifera
  32. The remarkable length of the nectary, containing much free nectar,the white colour of the conspicuous flowers, and the strong sweet odour emitted by them at night, all show that this plant [butterfly orchid] depends for its fertilisation on the larger nocturnal Lepidoptera. Madagascar Comet Orchid Lesser Butterfly Orchid Greater Butterfly Orchid Evidence of co-evolution Co-adaptation between orchids and their insect pollinators provided one of the finest of all test-cases for Darwin’s theory of evolution by natural selection Platanthera bifolia Angraecum sesquipedale The Madagascar Comet Orchid with its pollinator, Xanthopan morgani praedicta . Printed with kind permission of Kew artist Judi Stone. Darwin compared local and foreign orchids Judi Stone Platanthera chlorantha
  33. It is difficult to believe in the dreadful but quiet war of organic beings going on in the peaceful woods and smiling fields. The struggle for existence on Downe Bank A crab spider confronts an empid fly on an ox eye daisy An empid fly visits a common spotted orchid An empid fly devours another fly A crab spider eating an empid fly Crab spiders mating on orchid
  34. Man Orchid Pyramidal Orchid White Helleborine Common Spotted Orchid Broad-leaved Helleborine Fragrant Orchid Common Twayblade Bee Orchid Fly Orchid Nine species of orchid recently recorded on Downe Bank Downe Bank’s Orchids See notes page for details of recent name changes Cephalanthera grandiflora Anacamptis pyramidalis Epipactis helleborine Ophrys apifera Aceras anthropophora Dactylorhiza fuchsii Gymnadenia conopsea Listera ovata Ophrys insectifera
  35. Darwin’s orchids at Downe Kent appears to be the most favourable county in England for the order, and within a mile of my house nine genera, including thirteen species, grow; but of these one alone, Orchis morio, is sufficiently abundant to make a conspicuous feature in the vegetation; as is O. maculata [Dactylorhiza fuchsii] in a lesser degree in open woodlands. Green-veined Orchid Orchis morio at Marden Meadow, a Kent Wildlife Trust Nature Reserve 8 species of orchid that Darwin recorded locally currently grow on Downe Bank; these are illustrated on the previous page. His list excluded the Man Orchid that grows on Downe Bank and locally today. The illustrations above show the other 5 species he found around Downe. The Greater Butterfly Orchid and the Bird’s-nest Orchid grow at High Elms. Neottia nidus-avis Orchis mascula Platanthera chlorantha Herminium monorchis Bird’s-nest Orchid Early Purple Orchid Greater Butterfly Orchid Musk Orchid Orchis morio
  36. Orchid pollination on Downe Bank . Only wasps pollinate the Broad-leaved Helleborine Small insects alight on the labellum for the sake of the nectar copiously secreted by it [Twayblade Orchid] Close up view of nectar tubes of Fragrant Orchid flowers These orchids offer a reward Listera ovata Gymnadenia conopsea Epipactis helleborine
  37. Strategies of deceit Male Digger Wasp ( Argogorytes mystaceus ) pollinating Fly Orchid ( Ophrys insectifera ) Anacamptis pyramidalis Skipper butterfly with orchid pollinia Burnet moth with orchid pollinia Butterflies and day-flying moths pollinate the Pyramidal Orchid Nothing can be more perfect than the contrivances in Orchis pyramidalis [Anacamptis pyramidalis] for its fertilisation
  38. Frank Brightman, the first Hon. Warden of Downe Bank, designed a series of wallcharts that were produced as a result of a collaboration with the skilled artist Barbara Nicholson. They were published in 1972 by the Natural History Museum where he worked as Education Officer. The initial series of five wallcharts was inspired by the diversity of chalk grassland species on Downe Bank and included one that depicted a typical chalk grassland plant community. The wallcharts represented a new direction in botanical illustration that was subsequently widely adopted for numerous purposes. More importantly they depicted the plant biodiversity of different habitats and interpreted the concept of ecology clearly and effectively. They became a valuable interpretation aid for a wide range of people, especially teachers and conservationists. Today’s ecologists studying biostructures in the ecosystem are developing the studies that Darwin began at Downe. Pollination webs provide a new way of portraying a habitat by analysing and quantifying insect visitation. The evolution of ecology Southern England heathland pollination web with kind permission of Dr. Jane Memmott A portion of the Chalk Downs Wallchart reproduced with kind permission of the Natural History Museum
  39. Downe’s evolving landscape Cudham Valley view N. towards High Elms Meadow at Bottom Barn Farm (Part of a Countryside Stewardship Scheme) New wildlife corridor linking High Elms, Downe Bank & Musk Orchid Bank
  40. There is a grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved. Darwin’s Insights are fundamental to our understanding of the natural world Charles Darwin The Origin of Species