Soil Organisms Determining Plant Growth

When considering an organism within an ecosystem, the most important influences taken into account are above ground plant-plant interactions and animal-plant interactions and prevalent abiotic factors. However increasing evidence suggests that plant-microbial interactions in the rhizosphere play just as important a role. Take for example growth of the Hedge Woundwort, Stachys sylvatica. This unpleasant smelling perennial is generally found in hedgerows and forest verges, preferring humid soil and intermediate light (1). It can reproduce clonally by means of runners, and produces spikes of reddish-purple flowers from June to October.

Hedge Woundwort, Stachys sylvatica

In order to investigate the effect of different soil biota on S. sylvatica, plants were grown in artificial soil inoculated with soil the rhizospheres of two different locations: a hedgerow and a forest understory (2). The innocula were processed to remove soil fauna, leaving only the mycorrhizal ans microbial communities. Strikingly, the two different innocula produced two very different plant growth responses. The S. sylvatica plants grown in the presence of the hedgerow innoculum produced plants with a higher biomass and clonal runners than those with the forest verge innoculum. In addition, the forest verge innoculum plants showed a higher number of flower infloresences than the hedgerow innoculum plants. For S. sylvatica, this shows that soil biota drive possible adaptive growth strategies.

References:

1. Sterry Collins Complete Guide to Irish Wildlife p. 236
2. Peña and Bonte, 2011. Acta Oceologica 37 pp. 110-116

Colour Changing Spider

Misumena vatia

Misumena vatia is a common crab spider (Thomisidae), one of 14 species of crab spiders in Ireland (1). Resembling crabs in their appearance and in their movements sideways and backwards, the larger females can be found sitting on flowers, waiting to pounce on prey such as hoverflies and bees that feed on the flowers (2). M. vatia is most often seen on white or yellow flowers and quite amazingly the spider can change its colour, chameleon like, to camouflage to its background (3). Colour change occurs over a period of days and this ability is due to the presence of ommochromes in the spider, a group of pigments that are of widespread occurrence in insects and some other arthropods (4). There is some debate whether the ommochromes actually act primarily as a protection against photodestruction by intense UV light (4), but the fact that M. vatia possesses the physiological ability to distinguish between certain colours in its environment (5) lends credence to them playing a role in mimicry.

Misumena vatia

References:

1. Ferriss et al. 2009, Irish Biodiversity: A Taxonomic Inventory of Fauna p. 38
2. Sterry 2004, Collins Complete Guide to Irish Wildlife p. 152
3. Gibbons, 1999. Collins Nature Guide Insects of Britain and Europe p. 229
4. Théry and Casas, 2009. Philosophical Transactions of the Royal Society 364 pp. 471-480
5. Defrize et al., 2011. Journal of Insect Physiology 57 pp. 508–513

Know Your Neuropterans

Chrysoperla carnea

Very often I have come across species, of plant, animal and fungus, that upon searching the literature, reveal themselves to be actually a species complex, a number of species that are identical in many respects but are genetically distinct. The levels of these distinctions are often quite striking, as in the case of the Green Lacewing Chsysoperla carnea (Insecta: Neuroptera: Chrysopidae). This is a common insect of the summer months that is most recognisible from its almost ponderous flight and transparent, well veined wings. In the autumn time, the green adults hibernate, often indoors, their bodies turning a pinkish colour (1). The larvae feed on aphids and are used commercially to control aphid.

Chrysoperla carnea

C. carnea has been shown to be a complex of many cryptic species, based on the songs they make to attract mates (2). When sexually receptive, members of the C. carnea group vibrate their abdomens, which in turn causes the substrate (generally a leaf) on which it stands to vibrate, generating a song. This process is known as tremulation. Both sexes tremulate, so only individuals with the same songs will be attracted to each other, and since song is genetically determined, this results in reproductive isolation of populations charactrerised by song. At least 15 groups within the C. carnea group have been described, differentiated by song (3).

Chrysoperla carnea

As Neuropterans, lacewings are considered some of the oldest insects with complete metamorphosis (4). Ancient, extinct Neuropterans can be traced back to the Late Permian period, 260-251 million years ago. Of the current c. 6000 species of Neuropterans described, about 1200 belong to the family Chrysopidae, to which the C. carnea group belong.

References:

1. Sterry, 2004. Collins Complete Guide to Irish Wildlife p. 132
2. Henry et al., 2002. Annals of the Entomological Society of America 95 pp. 172-191
3. Henry et al., 1999. Evolution 53 pp. 1165-1179
4. Tauber et al., 2009. Neuroptera in Encycolpedia of Insects, Resh and Cardé eds, pp. 695-707

Industrialisation of a Mushroom

Dryad's Saddle, Polyporus squamosus

The Dryad's Saddle mushroom (Polyporus squamosus) is a large, fleshy agaricomycete that grows in a semi-circular or saddle shaped fashion on a range of both living and dead broad-leaved trees, such as  ash, elm, sycamore and beech (1). Its upper surface is creamy yellow in colour which is marked with concentric rings of brown scales. The under surface appears as a network of pale yellow, polygonal spores.

Underside of Dryad's Saddle, Polyporus squamosus

While P. squamosus is edible, it needs to be picked young as the older mushroom is quite tough and corky. However, if processed, the resultant biomass may present a viable animal, and possible human, source of nutrition (2). In addition, P. squamosus produces pectinases (3), enzymes that degrade pectin and that are used in the fruit industry to improve juice extraction from apples, etc. (4). A polymer-polymer two phase system has been successfully used to produce both P. squamosus biomass and resultant secondary metabolites (5). This method consists of two mutually incompatible structural polymers (namely polyethylene glycol and crude dextran) in solution which brings about a spontaneous separation of phases. This reduces the need for mechanical separation of cells. P. squamosus fungal growth is restricted to the bottom phase, leaving the top phase free.  

Dryad's Saddle, Polyporus squamosus

P. squamosus has also been shown to produce useful xylanase (6) as well as a lectin that shows great potential for usein glycobiological studies in biomedical and cancer research (7), making this method of growth a useful biotechnological tool.

References:

1. Harding et al., 1996. How To Identify Edible Mushrooms p. 143
2. Antov and Peričin, 2000. APTEFF 31 pp. 567-573
3. Antov and Peričin, 2001. Enzyme and Microbial Technology 28 pp. 467-472
4. Antov, 2004. Carbohydrate Polymers 56 pp. 295-300
5. Antov et al., 2001. Journal of Biotechnology 91 pp. 83-87
6. Antov et al., 2006. Process Biochemistry 41pp. 232-235
7. Ho et al., 2000. The Journal of Biological Chemistry 275 pp. 10623-10629.

Its a Sawfly, But Not Really

Tenthredo livida is a common sawfly of holartic distribution that is often found in hedgerows and woodlands. The female lays eggs into plant tissue, using saw-like ovipositor to make the inscision. Larvae are polyphagus, feeding on a variety of plats such as hazel, willow and even bracken. The adults will hunt flies and take nectar from plants (1).

Tenthredo livida

Interestingly, calling T. livida a sawfly, or "Symphyta", is now considered incorrect. The Symphyta are a basal grade that leads to the long waisted hymenoptera. Therefore Symphyta is not a monophyletic group, that is within the group not all relatives are included (2). The terms "Symphyta" and saw fly are still used however, in an informal way.
References:

1. Calmasur and Ozbek, 2006. Proceedings of the Entomological Society of Washington 108 pp. 139-144
2. Resh and Carde, 2009. Encyclopedia of Insects p. 474

Horse Chestnut Scale on a Linden Tree: a Polyphagus Insect

Horse Chestnut Scale, Pulvinaria regalis

While I have previously written on this blog that scale insects tend to be quite small, a large example has recently come to my attention. Pulvinaria regalis, or the Horse Chestnut Scale, is c. 6 mm in diameter, and the female is particularly visible this time of year when they produce a large, white, fluffy, ovisac into which up to 2,000 eggs are layed (1). Upon laying the eggs, the female dies, but remains attached to the ovisac as a protective shield. Without the ovisac, Pulvinaria regalis is excellently camouflaged against the bark of its hosts, Horse Chestnut, Linden and Elm species (its many hosts making it polyphagus), where it feeds by extraction of sap. Once the young hatch, they are easily dispersed by the wind due to their small size (2)

Horse Chestnut Scale, Pulvinaria regalis

P. regalis is thought to be of asian origin, and was first recorded in Europe in 1968 (2). The first record for Ireland was as recent as 2000 on a horse chestnut tree in Dublin, and the authors speculated then that P. regalis may spread throughout the country (3). This has proved to be the case as shown by this sighting in Cork city.

Horse Chestnut Scale, Pulvinaria regalis on Linden Tree

P. regalis is a particularly urban insect in Ireland, and Britain, where its host plants are not native (2). It rarely causes significant damage to trees, proving to be just rather unsightly.

References:

1. Speight and Nicol, 1985. Antenna 9 pp. 175–178
2. Speight et al., 1998. Ecology 79 pp. 1503-151
3. O'Connor and Fox, 2000. Entomologist's Gazette 51 pp. 145-146

Saint Patrick's Cabbage

Saint Patrick and Shamrock go hand in hand, like bread and butter or Laurel and Hardy. Legend has it that the saint used the three leaved Shamrock to demonstrate the Christian holy trinity, how the father, son and holy spirit could exist as one. Yet, while Saint Patrick makes numerous references to the trinity in his writings, nowhere does he mention the Shamrock (1). The association came some time after his death, most likely the co-opting of a pagan symbol into Christianity. Indeed the identity of the Shamrock is hazy to say the least, with various sources identifying it as wood sorrel, white clover and black meddick (2,3).

Flowers of Saint Patrick's Cabbage, Saxifraga spathularis

However, there is another plant that honours Ireland's patron saint, one much more deserving of the role. Saint Patrick's Cabbage is a saxifrage that bears the saints name both in its common name and its binomial moniker, Saxifraga spathularis. It is a distinctly Irish plant, being found only on the Island of Ireland as well as northwestern Spain and the mountains of north Portugal (4), where it is commonly called abelairiña. Its clusters of green leaves bear stalked pannicles of pretty white flowers that show numerous pink dots on the petals. S. spathularis has a wide tolerance to soil conditions and can be found in a variety of habitats, from exposed mountains to the shade of humid woodlands. In Ireland, it is distributed along the west coast, from Cork to Donegal, however its main base is in Kerry and West Cork. Records have been reported from Tipperary, Waterford and Wicklow, but pressure on hedge banks could be reducing its incidence (4).

Saint Patrick's Cabbage, Saxifraga spathularis

S. spathularis is closely related to another saxifrage species particular to Ireland and northern Iberia, Kidney Saxifrage (S. hirsuta). The two species can in fact hybridise to form S. x polita, which is commonly found growing in gardens as False Londonpride. Areas where S. spathularis and S. hirsuta grow in close proximity have seen an increase in the hybrid to the detriment of the populations of these two species (5).

References:

1. Edna Barth, 2001. Shamrocks, Harps, and Shillelaghs: The Story of the St. Patrick's Day Symbols pp. 146-149
2. Colgan, 1892. The Irish Naturalist 1 pp. 95-97
3. Frazer, 1894. The Journal of the Royal Society of Antiquaries of Ireland 4 pp. 132-135
4. O'Mahony, 2009. Wildflowers of Cork City and County pp. 128-130
5. O'Mahnoy, 1994. Irish Botanical News 4 pp. 17-19