Monday, August 23, 2010

Wasps Are Eating My Cake

The German Wasp, Vespula germanica
August in Ireland has a lot to recommend it: long, lazy evenings, (relatively) good weather, abundant free fruit in hedgerows. As a month though it does have a major drawback – wasps, sticking their faces into anything remotely sweet. Buzzing around mineral cans and ice lollies up and down the country, they are not only an annoyance, but also pose a risk to ones self as wasp stings are designed primarily to repel vertebrate attacks with little if no effect on other insects (Schmidt, 2009 Encyclopedia of Insects pp. 1049-1052). Easily the most numerous to be seen engaged in this activity are the very similar Common Wasp (Vespula vulgaris) and the German Wasp (V. germanica) (Chinery, 1997 Collins Gem Insects, pp. 234). Social, nest building wasps, these can reach very large numbers in the presence of foods, especially those with a high sugar content.

The animals engaged in this activity are workers, which normally receive sugary trophallactic secretions produced by larvae in response to food provided to them. Around August however, all the larvae have pupated, with the result that the workers must find their sugar rush somewhere else. Thus they descend on our picnics and barbecues to gorge themselves. And as well they might, because come winter they will all die away, the cold weather putting paid to them, along with any males and the previous year's queen. New queen wasps that were hatched between August and September will have mated at this time and hibernate over winter to begin new nests in the spring (Archer, 1985 Journal of Animal Ecology 54 pp. 473-485).

Saturday, August 21, 2010

Montbretia - Travelling Plants

A guest post by Ken.

So now it is August and we return, as promised, to Montbretia. The most prominent wildflowers at the moment on the sides of country roads are the bright oranged-coloured ones known as Montbretia (Crocosmia x crocosmiiflora). I have heard others refer to them as St. Anthony's Lilies.

Where to now Montbretia?

Montbretia is a man-made hybrid from France and is familiar in gardens and one of the most widely established escapes in Britain and Ireland. It is clump-forming and grows to approx. 60cm. The flowers are reddish-orange with six petal-lobes being the same length as the gradually widening tubes that form an unbranched one-sided spike. They can be seen between July and October (although it is usually August that I remember as the month for Montbretia). The leaves are iris-like but are not pleated and have a prominent mid-rib. It  can be seen around sea-cliffs as well as grassy-banks and less frequently found inland. (Wild Flowers of Britain & Ireland, Blamey, Blamey & Fitter, pp. 320-321).

Montbretia (Crocosmia x crocosmiiflora)

The pictures displayed here are taken around the Rocky Bay area. (A great place for a swim in the sea. In the distance there is the ever present oil-tanker[not-pictured]  - I have never seen it move!!).

Country road by Rock Bay

It is a cross between 2 South African species but I can only assume the cross took place in France. Those two species are Crocosmia aurea and Croscomia pottsii, the cross being listed on the Consolidated list of environmental weeds in New Zealand (Dept. of Conservation NZ, Howell 2008). It is an invasive species in New Zealand and indeed is an introduced one in Ireland too. See below picture of Montbretia with its other alien friend the fuchsia (Fuchsia magellanica).

Bedfellows (Crocosmia x crocosmiiflora and Fuchsia magellanica)

One of the species of the cross Crocosmia pottsi (Falling stars) is a Zulu medicinal plant called Undwendweni where the corms are used to treat infertility. (V. Steenkamp, Traditional herbal remedies used by South African women for gynaecological complaints, Journal of Ethnopharmacology, Volume 86, Issue 1, May 2003, pp. 97-108).

So, from Zulu medicine in South Africa, to botanists in France (didn't Buddleia davidii visit there too?) and then to Cork, I leave you now with the beauty of another wild Irish plant, Montbretia.



Thursday, August 19, 2010

Some Seashore Bivalve Shells

Common Cockle, Cardium edule

Common Otter Shell, Lutraria lutraria

Banded Wedge Shell, Donax vittatus

Thin Tellin, Tellina tenuis

Oyster, Ostrea edulis

Razor Shell, Ensis siliqua

Common Mussel, Mytilus edulis

Wednesday, August 18, 2010

How Galling To Be An Oak

Round clusters of marble shaped ones on the branches. Disc shaped ones on the under side of the leaves. Bizarrely shaped green ones on the acorns. Oaks do have a lot of galls associated with them. The most recognisable and common of these are caused by by the oak cynipids (Cynipini). These are wasps that develop as obligate herbivores in galls that they initiate on various growing parts of oaks (Hayward and Stone, 2005 Basic and Applied Ecology 6 pp. 435-443). The Cynipini lifecycle is cyclically parthenogenic, involving obligate alternation between a spring sexual generation and a summer/autumn parthenogenic generation (Stone et al., 2002 Annual Review of Entomology 47 pp. 633-668).

Knopper Gall
Occurs in Pedunculate Oak (Quercus robur). Caused by Andricus quercuscalicis. Subsequent generation develops in galls induced in catkins of the Turkey Oak (Quercus cerris).

Spangle Gall
Occurs in both Pedunculate Oak and Sessile Oak (Quercus petraea). Formed by Neuroterus quercusbaccarum, they appear as discs on the underside of the leaf. Subsequent generation develops in galls induced in oak flowers.

Marble Gall
Occurs in both Pedunculate Oak and Sessile Oak. Form clusters of marble like galls caused by Andricus kollari. Subsequent generation develops in galls induced in bud leaves of the Turkey Oak.

Gall function may be either for food or protection. The gall may provide enhanced nutrition over other feeding modes, it may protect the larva from unfavourable environmental conditions or it may protect the larva from attack by natural enemies (Stone and Schonrogge, 2003 Trends in Ecology and Evolution 18 pp. 512-522). It is likely that it may be a combination of all three.

The mechanism for production of galls by Cynipini is not fully understood. Gall production by bacteria involves the bacterium exporting plasmid DNA, with gall induction resulting from host expression of theses genes (as in the case crown gall tumors induced by Agrobacterium tumefaciens) or the production of signal molecules such as nod factors (Rhizobium spp.). Cynipini larvae also secrete gall-inducing stimuli, yet their mode of action is unclear. What is known, however, is that gall morphologies represent the extended phenotypes of galler genes.

Tuesday, August 17, 2010

The Sea Gooseberry

Pleurobranchia pileus

The Sea Gooseberry (Pleurobranchia pileus) is a neretic Ctenophore that is common to the waters around Ireland. Its body is clear and 2-3 cm in diameter. This bears eight rows of equally spaced comb plates, each made of rows of long, fused cilia which it beats to move through the water. P. pileus is a non-selective carnivore, using 15 cm soild, highly extensile tentacles to lasso animals which are brought up to the mouth. This leads to a long, narrow pharnyx, which opens to the stomach (Kotpal, 2009 Modern Text Book of Zoology: Invertebrates pp. 318-319). It posses a sense organ called a statocyst at its aboral end and it has been shown that P. pileus can sense the presence of predators and move away accordingly, away from the sediment, reducing predation risk (Esser et al., 2004 Marine Biology 145 pp. 595-601).

Pleurobranchia pileus

P. pileus is at its most abundant in Irish seas in October to November, however a summer peak in numbers is often common (Fraser, 1970 Journal du Conseil 33 pp. 149-168). Populations can reach high densities during these periods (>10 individuals per cubic meter). Mills (2001, Hydrobiologia 451 pp. 55-68) has suggested that P. pileus numbers are increasing globally, along with other Ctenophores and Scyphozoa in response to changing ocean conditions. This could have serious consequences for fishery yields, and marine ecosystems as a whole, worldwide as both these organisms are both competitors and predators of young fish.

Monday, August 16, 2010

Scuttle, Scuttle, Scuttle: Its a Bristletail

Petrobius maritimus

Look among the crevices of the upper shore and splash zone of an Irish rocky shore and you will encounter a small, scurrying insect no more than 15 mm in length, often in large numbers. Indeed these creatures are to found in caves and other regions above the high tide mark where they feed on detritus, green algae and lichens. These are members of the Archaeognatha, the bristletails. Four species of Archaeognatha occur in Ireland: the local occuring Dilta saxicola and D. hibernica and the widespread Petrobius brevistylis and P. maritimus (Ferriss et al., 2009 Irish Biodiversity: a Taxonomic Inventory of Fauna p.97). P. maritimus is by far the most common in Ireland. It has an elongated body, with an eleven segmented body (Sterry, 2004 Collins Complete Guide to Irish Wildlife p. 122). Three filaments at its tail end explain it its bristletail moniker and its antennae are noticeably long. These features combined with its dense scale cover and its ability to jump give them protection against predators (Sturm, 2009 Encyclopedia of Insects pp. 48-50). Archaeognatha are quite an ancient class of insects which can be seen in their lack of wings and lack of true metamorphosis (Linssen, 1987 Insects of the British Isles pp. 39-40).

Petrobius maritimus

Sailing with Barnacles

One of the most common sights on the intertidal zone of a rocky shore are barnacles encrusting the rocks. Water washing over the animals brings plankton which the crustaceans filter out using their legs.

Acorn barnacles attached to rock surface

However some species (a whole order in fact, Pedunculata) operate quite differently. While still attaching themselves to a substrate, they prefer the more dangerous life out on the ocean waves. Both the Goose Barnacle Lepas anatifera and the Buoy Barnacle Dosima fascicularis attach themselves to substrates floating in the pelagic zone and remain adrift at the mercy of winds, waves and the ocean currents, which often wash them ashore.

Lepas anatifera

L. anatifera is covered with five translucent plates, bluish white in appearance, and attaches to its substrate of choice by a long retractable stalk which is dark brown in colour (Sterry, 2004 Collins Complete Guide to Irish Wildlife p. 170). In the past, this substrate was often driftwood (but now is more likely to be plastic rubbish). This, along with its appearance, lent it its name “Goose Barnacle” as it was thought that L. anatifera was an immature form of the Barnacle Goose (Branta leucopsis). This idea supposed that there were trees that grow the barnacles as fruits on their branches. When ripe they would metamorphose into geese, but sometimes branches with unripe specimens could break off and were washed up on shore (Scholtz, 2008 Journal of Biology 7 pp. 16.1-16.4). Even though this had been rubbished as early as the 13th century by the great philospher-theologian Albertus Magnus, the idea persisted even to the point where the great plantsman John Gerard included a "Barnacle Tree" in his Herball of 1597 (Pavord, 2005 The Naming of Names pp. 336-337). Persistence with this myth may have had a practical purpose as it meant that B. leucopsis could be classed as a plant, not meat and thus be consumed at lent.

Dosima fascicularis

In appearance, D. fascicularis is similar to L. anatifera, except its plates are almost see through, being a light brown colur, with the stalk similarly pigmented. It differs from L. anatifera in one important aspect however: it produces its own buoyancy aid. Upon attachment to a small piece of sustrate, D. fascicularis secretes a cement that acts as a float (Barnes and Blackstock, 1974 Journal of Experimental Marine Biology and Ecolgy 16 pp. 87-91).

Friday, August 13, 2010

Chitons are Safe as Houses

The chiton Lepidochitona cinerea attached to the bottom of an intertidal rockpool

The chitons (class Polyplacophora) are exclusively marine molluscs that are characterised by eight calcium carbonate shell playes that cover the animals muscular foot and mouth (Okusu et al., 2003 Organisms Diversity and Ecology 3 pp. 281-302). These plates are articulated and can be curved to fit closely a range of surfaces. This gives chitons a great deal of protection and allows the chiton to roll into a ball if dislodged from the surface. Chitons possess laterial or posterior gills that run either side of their foot that are quite striking in some species.

Lepidochitona cinerea curled in a ball on removal from surface

They are a very ancient class of molluscs with fossil records from the Upper Cambrian (510-480 million years ago) (Slieker, 2000 Chitons of the World p. 154). Eleven species in Ireland have been described, from the families Lepidochitonidae, Hanleyidae, Ischnochitonidae and Acanthochitonidae and range from 8 - 33 mm in length. They can be found on hard bottoms and rocky coasts where they graze on algae (Ferriss et al., 2009 Irish Biodiversity: a taxonomic inventory of fauna p. 57).

Underside of Lepidochitona cinerea

Given to Fly

Rarely moving from near water, stoneflies (the Plecopterans) are an oft unnoticed order of insects. Stonefly nymphs grow in water of fast flowing streams, although some species can be found in still water. Upon emergence, the adults rarely move from near the waters edge, where they feed little if at all. Adults rest their wings flat over their body or wrapped tightly around it, although some species are wingless. They possess two cerci or tails that arise from the 10th abdominal segment (DeWalt, 2009 Encyclopedia of Inland Waters pp. 415-422).

Stonelfy Adult

Stoneflies don't fly very well. Individuals in flight can often be brought to earth with just a touch. Some don't even engage in proper flight at all, such as the North American species Taeniopteryx burksi which, upon emergence from the water, escapes to the river bank by skimming across the water surface (Marden and Kramer, 1994 Science 266 pp. 427-430). This form of flight does not generate total weight support as contact with the water removes this need. Observance of this mode of flight, as well as that of another stone fly Allocapnia vivipara (which are incapable of flapping, but raise their wings in response to wind and glide across the water; Marden and Kramer, 1995 Nature 377, 332 - 334) has lead Marden and Kramer to a controversial hypothesis on the evolution of flight in insects. They suggest that these modes of “flight” show a pathway for gradual evolution to true flight.

Thursday, August 12, 2010

Taking Smaller Bites

Male Tufted Duck, Aythya fuligula

An attractive little black and white bird, the Tufted Duck (Aythya fuligula) is to be found all year round on lakes, resevoirs and flooded pits where it can be seen diving for food (Chinery, 1987 Field Guide to the Wildlife of Britain and Europe p. 75). The male (an immature example of which is pictured) has a black back, neck, head and tail with a white belly and under-wing. The predominantly brown female also has a white belly and under-wing, though not as extensive, as well as a white patch where the bill the face. Both sexes have a gray bill with a black tip and have distinctive yellow eyes. It derives its common name from the little drooping crest or tuft on the back of its head (Hayman and Hume, 2010 The New Birdwatcher's Pocket Guide to Britain and Europe p. 43).

Male Tufted Duck, Aythya fuligula

When feeding, it would be assumed that A. fuligula would take the largest (and most profitable) prey available. According to Draulans (1982, Journal of Animal Ecology 51 pp. 943-956) however, this is not the case. It was found that birds selected smaller mussels over larger specimens, with an increase in the selection of smaller mussels as prey density increased and depth decreased. This may seem to be contrary to the optimal foraging theory (MacArthur and Pianka, 1966 American Naturalist 100 pp. 603-609): why chose a smaller prey over a larger one? Draulans suggests that A. fuligula uses this method of feeding as smaller mussels provide less of a choking risk than large ones, the ducks may do better swallowing two small mussels in a dive rather than one large ones and larger mussels have highly variable profitabilities as larger shells have a higher likelihood of being empty.

Black Nightshade Harbours Disease

An introduced plant in Ireland, Black Nightshade (Solanum nigrum) is a annual that grows in waste places, roadsides and often as a garden weed (Phillips, 1977 Wild Flowers of Britain p. 116). It has small flowers with white, united petals and yellow anthers that ripen to black berries. The broad, ovate leaves are born on stems that are angular, erect and broadly branched (Toušová, 1978, Wildflowers of Field and Woodland pp. 74-75). The berries are poisonous, containing alkaloids such as solasodine, solasonine and solanidine, (Perez et al., 1998 Journal of Ethnopharmacology 62 pp. 43-48) and are toxic if consumed.

Black Nightshade (Solanum nigrum) Flower

This cocktail of chemicals has lead to extensive research on the pharmacological activity of S. nigrum. Extracts from the fruit and dried plants have been shown to have hepatoprotective and antiulcerogenic effects: plant extracts are effective against liver fibrosis in mice (Hsieh, 2008 Journal of Ethnopharmacology 119 pp. 117-121) and fruit extracts inhibit gastric lesions in rats, as well as controlling gastric secretory volume, acidity and pepsin secretion (Jainu and Devi, 2006 Journal of Ethnopharmacology 104 pp. 156-163).

Black Nightshade (Solanum nigrum) Unripe Fruit

However as a member of the same family as potato (Solanaceae), S. nigrum has been shown to act as an alternative host for the late potato blight, Phytophthora infestans. Late blight is estimated to cause €10.2 million worth of losses per annum in Ireland (Copeland et al., 1993. Vulnerability of the Irish potato industry to harmful organisms pp. 95-106). The parasitic fungus infects the leaves of the plant, causing necrosis by its feeding action which leads to the characteristic black lesions associated with blight. Following an outbreak of the disease, the rate of development of an epidemic is weather dependent and in Ireland such epidemic proportions are thought to be reached in 7 out of 10 years (Dowley et al., 2008 Irish Journal of Agricultural and Food Research 47 pp. 69–78). Flier et al. (2003, Plant Pathology 52 pp. 595–603) have shown that S. nigrum is readily infected with late blight and infected plants generate a considerable source of infection, suggesting it could be a significant disease reservoir.

Wednesday, August 11, 2010

The Bank Vole, Myodes glareolus

Bank Vole, Myodes glareolus

The Bank Vole (Myodes glareolus, formerly Clethrionomys glareolus) is a small rodent, 9 – 11 cm in length that can be recognised by its reddish-brown coat and short (4 – 6 cm) tail (Sterry, 2004 Collins Complete Guide to Irish Wildlife p. 20). Found in scrub, deciduous woods and hedgerows, it is active at both day and night in short burst when it often climbs amongst bushes. It is omnivorous, eating a wide variety of plant material as well as some insects (Chinery, 1987 Field Guide to the Wildlife of Britain and Europe p. 36).

Bank Vole, Myodes glareolus

A cosmopolitan European species, M. glareolus is found from Ireland through Europe to Lake Baikal in Siberia and from northern Turkey and Kazakhstan to inside the Arctic circle (Henbrot and Krasnov, 2005 An Atlas of the Geographic Distribution of the Arvicoline Rodents of the World). However its presence in Ireland is relatively recent. It was first discovered by A. J. M. Claassens in 1964 (Claassens and O'Gorman, 1965 Nature 205 pp. 923-924) in Listowel, Co. Kerry. Since then it has spread to the whole of Co. Limerick, Co. Kerry (except parts of the mountainous peninsulas), part of east Co. Tipperary, south-east Co. Clare and Co. Cork with the exception of the south-east (Smal and Fairley, 1984 Mammal Review 14 pp. 71–78). Mitochondrial DNA analysis of 81 bank voles by Ryan et al. (1996, Acta Theriologica 41 pp. 45-50) from 6 localities indicated that the founder population was small.

Its presence in Ireland is something of an anomaly: most alien species are introduced via the large ports on the east coast and radiate from there. So why is M. glareolus only found in the south-west? The answer may lie in the import of equipment for a hydroelectric scheme on the River Shannon from Germany in the 1920s. Stuart et al. (2007, Irish Naturalists Journal 28) compared mitochondrial DNA from M. glareolus individuals in Ireland and Germany and showed a close relationship between them which suggests that the German origin hypothesis may indeed hold water.

Tuesday, August 10, 2010

My Cup Runneth Over With Fungi

The cup fungus Peziza succosa

Peziza succosa is a cup fungus that is easily identified by the yellow milk that exudes from the ascocarp when cut. It grows on the surface of disturbed soil and was believed to be saprobic (Hansen and Pfister, 2006 Mycologia 98 pp. 1029-1040). However Tedersoo et al. (2006, New Phytologist 170 pp. 581-596) isolated P. succosa from ectomycorrhizal root tips from forests in Estonia and Denmark, suggesting it is an ectomycorrhizal symbiont. It grows to 2-5 cm in diameter and has no stem. Microscopically, its ascospores are 17-19 x 9-10 μm in size and have 2 guttules or storage lipids and 2 μm warts on the spores (Spooner, 2001 Field Mycology 2 pp. 51-59).

The cup fungus Peziza succosa

Monday, August 9, 2010

Duckweed as a Biomonitor

Common Duckweed, Lemna minor, on a pond surface

Floating on the surface of still ponds and lakes, Common Duckweed (Lemna minor) forms a verdant green carpet on the aquatic surface. The individual plants are quite small, consisting of a leaf-like thallus about 5 mm in diameter with a single root that dangles into the water. It is widespread and locally common throughout Ireland (Sterry 2004, Collins Complete Guide to Irish Wildlife p. 286). Reproduction is primarily vegetative. Duckweed is well named: as an animal feed (for ducks, as well as other fowl, fish and livestock) it provides protein of a high biological value and is highly digestible with only 5% fibre in dry matter of cultivated plants (Leng et al., 1995 Livestock Research for Rural Development 7).

Common Duckweed, Lemna minor, showing fronds and roots out of water

L. minor has an ability to respond in recognised patterns to various stresses, which has lead its use as an ISO standard for water quality (ISO 20079, 2005 Water quality—Determination of the toxic effect of water constituents and waste water to duckweed (L. minor)—duckweed growth inhibition test). Indeed, recently Appenroth et al. (2010, Chemosphere 78 pp. 216-223) has shown that L. minor is highly sensitive to nickel ions, making it a suitable tool for ecotoxilogical testing for this metal in accordance with the ISO 20079 protocol. On exposure to nickle ion concentrations of 1-100μM, fronds formed were quantitatively smaller and less green than innoculated mother fronds (above this level Appenroth et al. observed saturation in the dose–response curves but the phytotoxic responses can still be observed).

Decline of the Cinnabar Moth Suggests Larger Threat

Larva of the Cinnabar moth, Tyria jacobaeae feeding on ragwort

August, and the larvae of the Cinnabar moth (Tyria jacobaeae) are to be seen feeding manfully on ragwort plants (Senecio jacobaeae) throughout the country. The adult moths, with their wonderful charcoal and red wings, prefer the duck and night time where males are often attracted to outdoor lights. The black and yellow stripes of the larvae make a surprisingly good camouflage against the yellow of the ragwort flowers, however where once plants seemed to be infested with them, numbers of T. jacobaeae have decreased steadily in the past 30 years to a point where now only one or two individuals may be spotted on a plant, if at all.

While rarely killing the plant, T. jacobaeae is an important grazer of ragwort, often entirely defoliating individual plants and reducing seed production by 65 to 98% (Cameron, 1935 Journal of Ecology 23 pp. 266-322; Bornemissza, 1966 Australian Journal of Ecology 14, pp. 201-243). this is important as ragwort is classed as a noxious weed in both Ireland and the UK. This is due to the production of toxic alkaloids by the plant which cause cirrhosis in livestock if consumed (Dempster, 1982 Advances in Ecological Research 12 pp. 1-36). The alkaloids do make ragwort unpalatable if consumed fresh, so is avoided by grazers but toxicity is not lost upon drying so plant material ensiled may cause death in livestock.

Larva of the Cinnabar moth, Tyria jacobaeae feeding on ragwort

This toxicity does not effect T. jacobaeae: indeed it uses it to its advantage, as it stores alkaloids from the plants making it distasteful to most predators (Aplin et al., 1968 Nature 219 pp. 747-748). It announces this toxicity in its bold black and yellow stripes, which also warn of high levels of histamines which the moth produces itself (Bisset et al., 1962 Proceedings of the Royal Society 152 pp. 255-262). These are far quicker acting than the alkaloids and would deter a predator before it has killed the moth.

The moth is now under threat. While not in the same category as the endangered Marsh Fritillary Butterfly (Euphydryas aurinia), T. jacobaeae has been placed on the UK Biodiversity Action Plan which recognises a sharp decline in numbers (Whitehouse, 2007 Managing Coastal Soft Cliffs for Invertebrates pp. 12, 17). This reflects a general decline in moth numbers as a whole in Ireland and the UK. Conrad et al. (2006, Biological Conservation 132 pp. 279-291) showed in a 35 year study of 337 most common moth species that two thirds of them had declined, with 21% declining by 30% or more. This is a worry as the decline will surely have a knock on effect on the populations of insectivorous birds and bats. Moreover it suggests that as-yet undetected declines may be widespread among temperate-zone insects.

Thursday, August 5, 2010

The Cushion Starfish and the Pillars of Hercules

The Cushion Starfish, Asterina gibbosa

With its short arms projecting as short tips from its pentagonal body, the Cushion Starfish (Asterina gibbosa) is deserving of its name. Pincushion would be the more appropriate moniker though, as the animal, though capable of growing to 5 cm, is rarely seen bigger than 3 cm in diameter. It is found in the lower shore, often feeding on worms, brittle stars, sponges, star ascidians and hydroids in intertidal rock pools (Challinor et al., 2003 A Beginner's Guide to Ireland's Seashore p. 156), although it can be found to depths of 130 m (Hook, 2008 A Concise Guide to the Seashore p. 125). A. gibbosa shows a high variability in colour, ranging from red to yellow to green and is dispersed throughout the Atlantic and the Mediterranean.

Underside of Asterina gibbosa

A study on the relatedness of A. gibbosa in these areas (Baus et al., 2005 Molecular Ecology 14 pp. 3373 – 3382) revealed an interesting fact: that populations showed high levels of genetic differentiation between the Atlantic and the Mediterranean. This suggests that the Strait of Gibraltar represents a major barrier to dispersal for A. gibbosa dispersal. This so called “Pillars of Hercules” hypothesis has been reported for a number of other marine species (the spider crab Maja squinado (Neumann, 1998 Journal of Natural History 32 pp. 1667 – 1684), the sea bream Diplodus puntazzo (Bargelloni et al., 2005 Molecular Phylogenetics and Evolution 36 pp. 523-535), the barnacle Chthamalus montagui (Pannacciulli et al., 1996 Marine Biology 128 pp. 73-82)) and postulates that the Strait of Gibraltar represents a phylogeographic break, or a disruption in the geographical distribution of species. However Patarnello et al. (2007 Molecular Ecology 16 pp. 4426-44), on analysing numerous studies on genetic differentiation between the two regions suggest that observed differences are due to a combination of signature of vicariance, palaeoclimate fluctuation and life-history traits.

Tuesday, August 3, 2010

Butterflies, Flies, Bushes & Bees

"Butterfly, butterfly where have you gone?
To Buddleja davidii ever and anon."

Anonymous, 2010.

Butterfly bush (Buddleja davidii)

And indeed they do. The butterfly bush (Buddleja davidii) or summer lilac is a tall shrub growing anywhere up to 8m and well known in gardens for the numerous butterflies that are attraceted to the long dense spikes with their fragrant pale purple 4-pettalled flowers. These spikes are in flower around June to September. The leaves are opposite, lanceolate (narrowly oval and pointed, or lance-like), can be toothed and downy beneath. It was a cultivar developed in France in the 1890s and not the original wild Chinese plant. It has become increasingly an escape and can be found on bare and waste ground, particularly in or around towns and suburbs (Wild Flowers of Britain & Ireland, Blamey, Fitter and Fitter, A&C Black, London 2003, pp386).

I regularly encounter this plant as an escape when taking train journeys around Ireland and England. It is often near the track and/or peeping through the railway fencing. This is due to the abundance of associated waste ground.

Butterfly bush (Buddleja davidii)

On taking photographs of the plant recently, I found a few species of insect: a common green-bottle fly (Lucilia sericata), a bumble-bee (Bombus terrestris), a honey-bee (Apis mellifera) and a peacock butterfly (Inachis io).

Common green-fly (Lucilia sericata)

Bumble-bee (Bombis terrestris)

Honey-bee (Apis mellifera)

Peacock butterfly (Inachis io)

Alien plants or animals which become naturalised are often a concern and can cause disapproval among ecologists and conservationists. These species tend to 'take over' from native species and can come to be unwelcome weeds or pests. But buddleia is different: it rarely colonises natural areas, the plant is in no sense a farm or garden weed, and as a result of its special requirements cannot be viewed as a threat to native plants. Moreover, in Britain there must have been a 'vacant niche' for a woody shrub able to exploit dry rubble, old walls, building sites, and similar places, a niche that no native plant could fill so effectively. The Biological Records Centre, Institute of Terrestrial Ecology provide information that suggests buddleia first became naturalised on a significant scale in the 1930s in limestone quarries, on old walls, and on areas of exposed chalk. But not until the late 40s and 50s did the plant experience a population explosion which could be attributed to the sudden availability of sites created by bomb damage and subsequent re-building programmes following the Second World War. In London and other cities, dense thickets formed and since then buddleia has flourished in almost every piece of land where there is rubble. Owen and Whiteway suggest that as a plant increases its range and abundance it might be expected to acquire more and more associated insects: buddleia provides confirmation of this expectation but as is not the case in certain other introduced plants there appear to be no introduced insects associated with it. (D. F. Owen, W. R. Whiteway, Buddleia davidii in Britain: History and development of an associated fauna, Biological Conservation, Volume 17, Issue 2, February 1980, pp149-155).

From China, to France in the nineteenth century, through to the 21st century we are proud to present to you The Butterfly Bush.


The 21st Century Naturalists.