Finalist in the Blog Awards Ireland

The finalists for the Science & Education section of the Blog Awards Ireland have been announced: and 21stcenturynaturalist has been named as one of the top 6! Again, thank you all for your support, I couldn't have done it without you. Results are to be announced at a gala event on the 13th of October at the Osprey in Naas, Co. Kildare so fingers crossed!

Yellow Bartsia Makes an Appearance

Yellow Bartsia, Parentucellia viscosa

In the past, the hemiparasitic Yellow Bartsia (Parentucellia viscosa) was a very common member of the flora of damp pastures through out south west Ireland (1). Unfortunately the prectice of draining such paludal habitats throughout the 20th century led to a dramatic reduction in its numbers in the Cork and Kerry and it can now only be found with any sort of frequency on the islands of Roaringwater Bay off Cork's west coast.

Yellow Bartsia, Parentucellia viscosa

All of which means I was very surprised and delighted to see two plants at a disused quarry just 17 km from Cork city center, the same quarry mentioned in my previous post on the Red Veined Darter. The plants were at the side of what was once the road leading to the main quarry, their wonderful cascade of yellow flowers immediately standing out from the surrounding scrub. The discovery of this scarce native in such an undisturbed demonstrates how our ever decreasing biodiversity could be maintained by the thoughtful management of our surroundings.

References:

1. O'Mahony, 2009. Wildflowers of Cork City and County pp. 97-99

Red Veined Darter at the Quarry

Female Red Veined Darter, Sympetrum fonscolombii

Human activity often leads to dramatic changes in our landscapes (1). These changes in turn can lead to often irreversible damage to our freshwater habitats. The building activity in Ireland during the boom in the 2000's involved drainage and development of sites that directly and indirectly lead to the destruction of many of the countries wetlands habitats. The crazed excesses of the so called "Celtic Tiger" are not wholly to blame however, as wetland destruction has been a feature of the Ireland's changing ecology for some years. For example the extensive wetland complex located around the Douglas and Tramore rivers near Cork city was replaced with the municipal dump for over 20 years. Such destruction generally leads to a homogenisation of biodiversity and the local extinction of many plants and animals (1).

Ballyhemiken Quarry

However this is not always the case. Sometimes human induced changes on the landscape have a positive effect on biodiversity. A prime example of this is unused quarries. When in use, water entering these sites is drained or pumped away. When no longer in use, this water is allowed to collect, forming wetlands that are not naturally present on Ireland (2). One such site is located in Ballyhemiken, a townland about 17 km from Cork city center. Unused for a number of years, this quarry has many shallow pools that provides the perfect habitat for odonates. A number of species have been recorded here, namely Beautiful Demoiselle (Calopteryx virgo), Emerald Damselfly (Lesta sponsa), Variable Damselfly (Coenagroin pulchellum), Common Blue Damselfly (Enallagma cyathigerum), Common Bluetip (Ischmura elegans), Large Red Damselfly (Pyrrhosoma nymphula), Migrant Hawker (Aeshna mixta), Emperor Dragonfly (Anax imperator), Four Spotted Chaser (Libellula quadrimaculata), Ruddy Darter (Sympetrum sanguineum), Black Darter (S. danae) and Common Darter (S. striolatum) (2).

Shallow Pond at Ballhemiken Quarry

On a recent visit to the quarry I was lucky to spot several Red Veined Darters (S. fonscolombii). This is a rare sighting for Ireland, as it is only seen here as a migrant, and seldom at that with only twenty records for Ireland, mostly near the coast. As far as I can tell, the record reported here is the westernly most sighting for S. fonscolombii in Ireland. All individuals were female, and two consecutive visits showed no males. They were very wary and took to wing upon my approach, flying a short distance before alighting on the surrounding Yellowworts, mint, low growing willow, Reed Mace and rushes. When undisturbed, the females congregated around shallow pools, some of which had dried up.

Female Red Veined Darter, Sympetrum fonscolombii

There are no record of S. fonscolombii ever breeding in Ireland, however in Britain there has been an increase in numbers breeding. It is predicted that Ireland may follow suit and the numbers of sightings may increase in the future (3).

Female Red Veined Darter, Sympetrum fonscolombii

References:

1. Dolný and Harabiš, 2012. Biological Conservation 145 pp. 109-117
2. Nelson and Thompson, 2004. The Natural History of Ireland's Dragonflies p. 391
3. Nelson and Thompson, 2004. The Natural History of Ireland's Dragonflies pp. 301-305

Perching for Prey

Four Spotted Chaser, Libellula quadrimaculata

Other than the ubiquitous Common Darter (Sympetrum striolatum), probably the most common dragonfly encountered in Ireland is the Four Spotted Chaser (Libellula quadrimaculata). This is due to its incredible aggressive behaviour. Both males and females move with an almost frantic speed around their territory and will challenge and fight any other odonates that encroach (1). The individuals pictured were observed around a c. 20 x 10 m pond in a dune slack which was 1 m at its very deepest. The pond had cluster of low growing willow (1 m above the waterline at its highest) at its center, ideal for the dragonflies to perch. L. quadrimaculata was observed to patrol the pond at high speed and challenge both the S. striolatum and Blue Emperors (Anax imperator) that were also present at the pond. A. imperator is considerably larger than L. quadrimaculata, but this did not deter it from the challenge. L. quadrimaculata was also seen to patrol the areas bordering the pond and to chase prey. One individual was seen to catch and eat a Comon Blue butterfly (Polyommatus icarus), taking the prey to the grasses in the surrounding dunes to consume it, as is illustrated in the photograph. After patrolling, L. quadrimaculata was seen to perch either among the willow in the middle of the pond or among the grasses in the surrounding dunes.

Four Spotted Chaser, Libellula quadrimaculata, feeding on a Common Blue butterfly, Polyommatus icarus

When perching, L. quadrimaculata held their bodies at a seemingly awkward angle (often 45°) in relation to the perch, even though resting their abdomens against the perch was often an option. The reason for this is not related to the animals body , but to its eyes. The compound eye of odonates, and many other insects, can be divided into dorsal and ventral areas where the structure of the fovea varies (2). In many odonate species, the different areas of the eye are quite easily distinguished from each other, with the dorsal side being much lighter in colour due to the presence of screening pigments (3). The dorsal fovea exhibits a high spatial resolution as well as a high degree of sensitivity to short wave resolution. This makes it ideally suited to the detection of prey flying against a blue sky. Therefore L. quadrimaculata perches in such a way that its dorsal fovea is exposed to the maximum amount of blue sky (4).

References:

1. Nelson and Thompson, 2004. The Natural History of Ireland's Dragonflies pp. 259-267
2. Kral, 2002. European Journal of Entomology 99 pp. 1-4
3. Labhart and Nilsson, 1995. Journal of Comparative Physiology 176 pp. 437-453
4. Sauseng et al., 2003. European Journal of Entomology 100 pp. 475-479

Common Blue Butterfly Second Brood

Second brood male (top) and female Common Blue butterfly (Polyommatus icarus), mating

In June, I reported on the first brood of the Common Blue butterfly (Polycommatus icarus) in Ireland, with an example of a mating pair. As was reported then, P. icarus has a second brood in August/September (1) and the butterfly can now be seen throughout the Irish coast, but also inland where its food plant, Common Bird's Foot Trefoil grows. The mating pair pictured were seen at some coastal dunes on the south coast. At least 6 other individuals were also seen in the vicinity.

Second brood male Common Blue butterfly (Polyommatus icarus)

References:

1. Nash et al., 2012. Ireland's Butterflies A Review pp. 156-158

Shortlisted for Blog Awards Ireland 2012

The Blog Awards Ireland Shortlist has just been announced - and 21stcenturynaturalist is on the shortlist for Best Science / Education Blog! Thanks for all your support! Again, results will be announced at the Blog Awards Ireland 2012 ceremony on the 13th of October.

Also, 21stcenturynaturalist is now on Facebook, so if you are interested in further natural science features and pictures, you can join us here.

Roads for the Ringlet

The Ringlet, Aphantopus hyperantus

As a wet, wet summer turns to autumn, one of the butterflies that remained flying despite of the rain will soon be gone until next year. The Ringlet (Aphantopus hyperantus) is on the wing from mid-May to the beginning of September in Ireland, but is most populous from the start to the middle of July. It is one of the most common species in Ireland and its preference for damp areas and ability to continue flying in light rain (1), unlike most other butterflies, means that this summer it was the species I personally encountered most often. Its larval food plants are almost exclusively grasses, such as Cocksfoot and False Brome, and it is around such grasses that adults are most likely to be encountered (1).

The Ringlet, Aphantopus hyperantus

Unfortunately, changes in agricultural practices and development have lead to a destruction of the semi-natural grassland habitats where these plants thrive, putting pressure on populations of A. hyperatus. Not all such development is without some benefit, however. Roadside verges and intersections have become home to many of the plant species associated with these habitats (2). It has been shown in a study on Finnish roads that the correct management of these areas through practices such as mowing can maintain populations of A. hyperantus and provide an alternative habitat for the butterfly (2). Intensive mowing should be avoided and mowing in mid-summer should only take place if road safety dictates. Even then only partial mowing in mid-summer is preferable, with a total mowing in late summer.

References:

1. Nash et al., 2012. Ireland's Butterflies a Review pp. 205-207
2. Valtonen and Saarinen, 2005. Annales Zoologici Fennici 42 pp. 545-556

Strawberry Trees Forever

Flowers of the Strawberry Tree, Arbutus unedo

As an island, Ireland has less plant species than Britain, which in turn has less than continental Europe. It would stand to reason then to expect all the botanical species present here to be present in Britain, and then some. Yet this is not the case, with Ireland being home to a number of plants not present in the wild in Britain. There are three main classes of such plants, based on the regions that they are characteristic of, namely the Atlantic flora, the American flora and the Mediterranean-Atlantic flora (1). Of the last group, the most intriguing member has to be the Strawberry Tree, Arbutus unedo. As a member of the Ericacea family, it has wonderful bell shaped, heather-like flowers. The fruit give the plant its common name, being shaped like strawberries. These take a year to reach their full ripeness, and so the tree often has both flowers and fruit present, as was the case in the specimen pictured. It is of common occurrence throughout the Mediterranean (to the extent that it features on the coat of arms of the city of Madrid) where it tends to grow as a low shrub. Its range in Ireland extends along the west coast, with extant sites in Kerry, West Cork and Sligo (1). Here, it is more likely to be found as a tree and can grow up to 10 meters in height (2). A. unedo seemingly had a much wider distribution in Ireland in the past as it was a protected species under Brehon Laws here in the eight century. It was then known as "Caithne" and this is still present in many Irish place names (1).
 

Strawberry Tree, Arbutus unedo

So why is this plant present in Ireland but not Britain? The theory behind Ireland's floral distribution is that the communites we have with us now began arriving after the last major glaciation event c. 15,000 years ago from mainland Europe. Since sea levels were much lower at that time, the coast lines of Ireland and Britain must have been very different from what they are now and possible landbridges between these two islands and Europe may have existed (3). The exact nature of these is considered to be a possible reason for the presence of A. undeo in Ireland but not Britain. Post-glacial movement by human populations may similarly have brought the tree to Ireland, bypassing Britain (4).

Fruits of the Strawberry Tree, Arbutus unedo

However, the idea of Ireland being a clean slate for plant species after the last glaciation event has been challenged by recent genetic evidence from the Fringed Sandowort (Arenaria ciliata). This low growing plant, found in mountainous habitats is found in only one location in Ireland, on top of the mountain Ben Bulben in Co. Sligo. Analysis of a number of European populations has shown that the Irish plants in this location survived the last glaciation event and have been present here for at least 100,000 years (5). The presence of such a refuge indicates that other areas in the country may have similarly avoided the ice sheet, providing the possibility that A. unedo may have been in the country for a similar length of time. There is also the possibility that A. unedo was present in Britain prior to the last major glaciation event, but the next either left no refuges as were left in Ireland or, more likely, left refuges that were in areas where no populations of A. unedo existed.
 

Strawberry Tree, Arbutus unedo

And yet all of this is supposition and the real origins of A. unedo in Ireland remains a mystery. This may become lessened in the near future, however, as a research project being spearheaded by Colin Kelleher of the Irish National Botanic Gardens is sampling A. unedo plants from Ireland and from areas within its European to try to elucidate what the relationships are between populations. Results of this work will certainly help to bridge some of the gaps in our knowledge of this wonderful plant.

References:

1. O'Mahnoy, 2009. Wildflowers of Cork City and County pp. 118-138
2. Sterry, 2004. Collins Complete Guide to Irish Wildlife p. 188
3. Pilcher and Hall, 2001. Flora Hibernica pp. 1-17
4. Teacher et al., 2009, Heredity 102 pp. 490–496
5. Dang et al., 2012. Molecular Ecology Resources 12 pp. 894–908