Monday, 22 April 2013

Gene flow ...

Arundel Wetlands

The beautiful water vole, Arvicola amphibius, was once a common site along the banks of the Arun Valley waterways. However, the modification of landscapes for agriculture and urbanisation, and the colonisation of the American mink, Neovison vison, led to their dramatic decline both locally and nationwide. In Sussex alone, we have sadly lost over 90% of our historic populations.


The Arun Valley water vole project is studying the gene flow within and between water vole populations, and investigating the effect of different habitats and landscapes in Sussex. The research is being undertaken during 2012 and 2013 and involves both field and laboratory techniques.

With the help of volunteers, numerous ditches were surveyed over a three month period, and evidence of breeding water voles was found on 13% of the waterways surveyed. This was an encouraging sign but, for the most part, only a few latrines were recorded. However, it was on an agricultural drainage ditch at Houghton Bridge, near Amberley, that signs of recolonisation were evident. Large concentrations of water vole latrines, feeding stations and burrows were present, indicating a potentially viable breeding population. This was great news as it suggested that water voles were recolonising northwards up the valley.

This raised several questions:

Had this newly found population come from Arundel Wildfowl & Wetlands Trust (AWWT), which is a reintroduction site located approximately 6.5km downstream?

Was the population too isolated and unable to rely on new individuals that would provide demographic and genetic rescue?

Can farmland ditches, not managed for water voles, hold viable populations?

Over the last two years Rowenna Baker has set out to answer these questions by studying the genetic structure and demographics of water voles at Houghton Bridge and AWWT through live trapping individuals each year, PIT (passive integrated transponder) Tagging, and by taking hair samples to obtain DNA for genetic mapping. Encouragingly, the abundance of water voles at Houghton Bridge is comparable to other natural colonies occurring along similar habitats nationwide, with estimates ranging from 20 to 50 individuals along 1km of bank. The population is small in comparison to  AWWT (135 individuals in 2010), where they are not affected by the external pressures of grazing and predation that commonly constrain habitat availability and density in unprotected sites. Both populations remain genetically diverse, however dispersal between populations is low, which is unsurprising as the average dispersal of water voles is 1-2km.



Despite the importance of genetic fitness, little is currently known about the genetic structure of water vole populations and what factors facilitate or impede gene flow within and between populations. Other studies have found that increasing distance between populations, land use and habitat design can all influence gene flow in animal populations.

The Arundel population is clearly a vital source for the recolonisation of water voles within the valley, however it is crucial that landscape connectivity is improved to aid dispersal between newly established populations. With additional colonies being found as far north as Pulborough Brooks, Rowenna now uses remote hair tubes to obtain genetic samples from all occupied sites in order to investigate gene flow and factors that facilitate and impede dispersal. This information will help to guide management to strengthen isolated populations by creating habitat networks that will hopefully promote water vole dispersal and recolonisation.

An important project regarding an excellent flagship species and one which I was privileged to witness first hand.

My thanks to Rowenna ...

Saturday, 20 April 2013

Leaf-miners ...

Stigmella aurella

The large group of moths known as the Nepticulidae are all extremely small, and because of the manner in which their larvae feed internally within the leaf structure, they are known as leaf-miners. The shape of the pale gallery or blotch created by the larva as it feeds, is usually a much better means of identification than by comparing the adult insect.

Stigmella aurella, pictured below, is probably the commonest and most widespread in the British Isles, its whitish larval mines are a familiar sight on bramble leaves everywhere. In addition to bramble, the larvae will also feed in the leaves of wild strawberry, agrimony, dewberry, water avens, and wood avens. The adults have a wingspan of only 6mm, have a metallic sheen, and fly in May and later in the summer.

Miners are generally restricted to a certain range of food plants, so the identification of a miner is greatly assisted by correctly identifying these plants. The shape of the mines (gallery or irregular blotch) and the patterns of the droppings (frass) within, in addition to the characteristics of the larvae and pupae, can all be key diagnostic features. Lepidoptera tend to construct galleries or blotches with single lines of frass. Diptera characteristically make twin trails of frass. Hymenopteran mines have characteristically more abundant and generally darker frass, particularly when compared to dipterous mines. Several species, including certain Coleoptera, make cut-outs in the leaf and the structure of these can help aid correct identification.


Friday, 12 April 2013

A golden opportunity ...

Mere Sands Wood, Lancashire

Simply stunning ...


Passport in hand (and phrase book at the ready), I recently took a long overdue opportunity to travel north and visit several locations in west Lancashire with friend and professional wildlife photographer Steven Round. Steve, who is based on the Wirral and specialises in bird photography, has had many hundreds of photographs published in books, calendars, advertising, educational literature and magazines (including many front covers). His images have also appeared on television, including the BBC programmes Springwatch, Autumnwatch and Countryfile. Steve's website can be found at www.stevenround-birdphotography.com. I highly recommend a look ...

Mere Sands Wood is a wildlife-rich haven in the heart of agricultural west Lancashire. It is owned and managed by Lancashire Wildlife Trust. The reserve covers 42 hectares (105 acres) of lakes, mature broadleaved and conifer woodland, sandy, wet meadows and heaths. In addition to its geology the site is of national importance for wildfowl and dragonflies and has a fascinating history. It stands on a large area of layered sand and peat, which was deposited by the wind over boulder clay during the last Ice Age and by periods of water logging following this period. The sand and peat layers have remained almost undisturbed since this time and are therefore of international importance in the understanding of the changes that occurred to the Lancashire coastline since the ice retreated northwards. In addition to the site's status as a Site of Special Scientific Interest (SSSI), the geological interest warranted the reserve being designated as a Geological Site of Special Scientific Interest (SSSI) in 1985.



The name 'Mere Sands' dates back to medieval times when the area was on the shore of a vast lake called 'Martin Mere'. Over time the area was gradually drained for agriculture along with large areas of surrounding peatland. Prior to drainage it formed the largest body of fresh water in England.

The sand proved to be of value for glass-making and extraction companies quarried the site between 1974 and 1982. During this period, the Wildlife Trust, its members and the local community worked with Lancashire County Council to require the extraction company, under a planning agreement, to landscape the site into a nature reserve once the extraction was completed. Close liaison with the quarrying company ensured that belts of the best woodland were left undisturbed during extraction to save as much wildlife as possible and screen the works. Extracted areas were landscaped into shallow-edged lakes with marsh and dry heath conditions nearby. On completion of the sand-winning, restoration and landscaping the Trust acquired the site in its entirety in 1982.

The mature woodland is mainly Birch with some Oak but there is also a mature Scots Pine plantation in the south-east corner of the reserve, which supports a small population of red squirrels. Large amounts of Rhododendron have been removed from the reserve, which has allowed the re-establishment of native flora such as Broad Buckler Fern and several species of Bramble. Over 200 species of fungi have been recorded. The lakes are developing an interesting aquatic flora; some of this has been augmented with the establishment of locally sourced reed beds on the lake shores. Wet grasslands and dry heaths occur on areas refilled after sand extraction and now support many wildflowers including Marsh Helleborine, Common Spotted, Early and Southern Marsh and Bee Orchids and notable populations of Golden Dock, Yellow Bartsia, Yellow-wort, Lesser Centaury and Royal Fern.


From a personal perspective, the main wildlife interest at Mere Sands is the over-wintering birds; particularly wildfowl. Winter populations include nationally important numbers of Gadwall and Teal, as well as Wigeon, Pintail, Shoveler, Pochard, Tufted Duck, Goldeneye (males pictured above) and Goosander. Locally important species include Mandarin Duck and Kingfisher and there are annual sightings of Willow Tit and Lesser-spotted Woodpecker. Tree Sparrow and Reed Bunting (female pictured above) can be found feeding amongst the Phragmites. Breeding species include Great Crested and Little Grebes, Shelduck (male pictured above), Gadwall, Pochard and Tufted Duck, alongside Little Ringed Plover and Lapwing. Over 170 bird species have been recorded on the reserve, of which 60 are known to have bred.

I highly recommend a visit ...

Saturday, 6 April 2013

Come dine with me ...

Mud-puddling and other Bad Habits

As with most insects, butterflies do the majority of their growing and eating during the larval stage. Nevertheless, the adults still require nutrition. This is predominantly obtained in the form of floral nectar, along with tree sap and other sugar-based foods for flight energy, with other micronutrients being required for egg maturation and successful reproduction. It is these that are gained from a number of apparently strange sources including animal dung, bird droppings, urine, human sweat, rotting fruit, fermenting juices from timber, dead fish, animal carcasses, honeydew (sugar-rich excrement produced by aphids) and even dew covered embers from fires.

The term ‘puddling’, which originates from the tropics, is often used when butterflies visit animal dung and urine-soaked ground. This behaviour can often be observed on patches of damp ground or streamside mud where animals have been drinking and then defecated. In our own quest for finding ‘exotic’ species in Britain, the magnificent Purple Emperor being a classic example, it is possible to use the equivalent, including human body fluids, to attract such butterflies. Puddling also occurs on seepages, muddy puddles, drying riverbanks and has been observed on roadside verges after heavy rain. The main purpose of this act appears to be the collection of key nutrients, which are otherwise scarce in their regular diets. Evidence suggests that the primary target is sodium, although nitrogen and phosphorous rich compounds may also be essential.

There is still debate as to why butterflies and indeed other insects require these additional nutrients. It has been suggested that sodium plays an important role in a number of physiological processes including assisting amino acid uptake during the digestive process and assisting neuromuscular activity. Another theory suggests that these additional nutrients are important to the male of the species by allowing them to better provision their spermatophores prior to passing to the female during copulation, due to the additional nutrients it contains. Whatever the reason, the act of ‘puddling’ is undoubtedly a fascinating behaviour. Whether it is for a slightly unusual choice of nuptial gift or the entomological equivalent of drinking a can of Red Bull (other makes of high energy drink are available), many aspects of this behaviour still remain unanswered …



Friday, 5 April 2013

Hypoponera ...

MISTAKEN IDENTITY

Hypoponera punctatissima (Roger, 1859), [Formicidae: Ponerinae], is a small brown ant with a functioning sting, a single substantial petiole (the body section connecting the alitrunk (mid-section) and gaster (the bulbous rear section) in hymenopterous insects) and a constriction between the first and second segments of the gaster. It is an underground species, where it lives and forages on small soil living arthropods. Only the alate gynes (the winged reproductive females of ants) are likely to be seen above ground.

The underground colonies can be polydomous (occupying and maintaining multiple nests) usually containing several queens, a few wingless worker-like males and around 200 workers. Its flight period is from May to September.

There is some dispute as to whether this should be treated as a native species because it is most often come across in greenhouses and other permanently heated buildings, though there is evidence for its presence 1600 years ago in northern Britain. Colonies have occasionally been discovered a long way from human habitation. It has been recorded outdoors from waste spoils warmed by fermentation or decay. It is a cosmopolitan species distributed throughout Europe, the tropics and sub-tropics. Isolated records have come from England, Wales and Ireland. At the time of writing it has not been recorded from Scotland.



















Hypoponera schauinslandi (Emery, 1899) has rarely been recorded in Britain. It is a little smaller than punctatissima and can be separated in the gynes by measuring the head-width, head-length and scape length (the basal segment of the antenna). It has a tropical or sub-tropical origin and cannot survive outdoors in Britain. It has an unusual flight period of November to February which can act as a useful guide in its identification. H. schauinslandi was only recognised as present in Britain in 2000.

The alate gyne pictured above came from a small colony discovered living underground in a heated commercial premises in Worthing, West Sussex on 13th January 2012. The original colony, discovered in December 2004, was originally identified as H. punctatissima. My thanks to Mike Fox, Ant Record Coordinator for the Bees, Wasps & Ants Recording Society (BWARS), for confirming correct identification as H. schauinslandi. On 2nd January 2013, another single winged female was recorded from the same location.

It is possible that this is only the fourth known substantiated record for the UK.

Image copyright OUMNH. Photomicrography by James Hogan, Hope Department of Entomology.