History & Ecology of Goldeneyes Teloschistes chrysophthalmus in England

Introduction

Goldeneyes Teloschistes chrysophthalmus is under going what is clearly a large scale colonisation event along the south central and south east coast of England after being extinct in this area for over 100 years. This seems to be a lichen equivalent to the Little Egret, an exotic southern species which has suddenly colonised the south. Like the Little Egret it is likey to have got here under its own steam, so is a native species. Presumably spores have blown over the channel from France; its locally abundant in Brittany, where has also recently started to expand its range (link).

It would be an easy assumption to take this as a straight forward result of recent warmer temperatures but the fact that the species was found in much the same areas in the 19th century before disappearing is intriguing and suggests more is going on.

History

The NBN has six dated records from the 19th century 1809 – 1892, five were recorded between the Isle of Wight and Lewes, East Sussex and one from Torquay, Devon in 1842. There are also two undated, but presumably 19th century, records from Lewis and Lyme Undercliff, Devon. The majority of these records were within the core area of 21st century recolonisation between Poole Harbour and East Sussex; Goldeneyes Teloschistes chrysophthalmus appears to be returning to the same areas it inhabited in the 19th century.

In the 20th century there were no records before 1966, but this may just represent a lack of lichen recording. In 1966 and 1998, two isolated records were recorded in the south west on the south coast of Devon and Cornwall respectively. Neither of these seems to have been more than isolated colonisations that failed to establish and both were outside of the area where the lichen was recorded in the 19th century.

In 2007 Goldeneyes came back with a surprising record from Herefordshire, followed by records from Poole Harbour and Kent, then the rush of records between the latter two areas as described in this website. So far the Herefordshire record seems to have been a one off colonisation, but the south coast has acquired established populations. Given the sparse nature of lichen recording in the 19th century, there were probably established populations then as well. The date of loss from the south can not be securely fixed as after WWI lichenology declined in Britain. The lack of records might be as much to do with the lack of lichenologists, but the species was certainly gone from its southern strongholds by the 1950/60s.

How does this pattern pattern of records match the temperature history of the last 200 years? One of the longest temperature records is the Central England Temperature record maintained by the Met Office link. The mean temperatures, as annual anomalies, are given below with the period when Goldeneyes was recorded from the south coast in the 19th century indicated.

The 19th century period when Goldeneyes Teloschistes chrysophthalmus was regularly recorded was marked by frequently colder years than the early 21st century. There were also occasional years which were as warm as most years during the current warmer period. The first record of Goldeneyes was made in 1809, which was in the depths of the end of the Little Ice Age. As it was present in the 19th century, why was the species lost in the first place? Conditions got warmer in the 1940s to 1960s, but no Goldeneyes was recorded along the south coast. Other factors must also be in play.

Ecology

A good source for the ecology of lichen species is ITALIC The Information System on Italian Lichens, which has an interesting entry on Goldeneyes Teloschistes chrysophthalmus. This gives the following information on this lichen:

pH of the substrata: intermediate between very acid and subneutral (2) to subneutral (3)

Light: in sun-exposed sites, but avoiding extreme solar irradiation (4) to sites with very high direct solar irradiation (5)

Humidity requirements: mesophytic (3) to xerophytic (4)

Eutrophication: in sites with very weak eutrophication (2) to sites with weak eutrophication (3)

Italian distribution: from the eu-mediterranean belt (1) to the submediterranean belt (2)

Note: this is a lichen typical of situations with a dry climate with frequent spells of fog. It is found on twigs of shrubs and isolated trees in open habitats. It was much more common in the past, and presently it is extinct in many regions (esp. of the north).

This is an intriguing description of the environmental requirements of Goldeneyes, especially the note that, although it is typical of dry climates, it requires periodic high humidity and that it is declining and rare in Italy. Clearly a sensitive lichen with very specialised requirements. The description of the requirements for pH of the substraight and eutrophication in Italy, do seem a bit lower than those observed in England.

Goldeneyes is a twig species and can clearly rapidly and efficiently colonise, including over long distances. The English populations have clear habitat preferences; the see Keyhaven report. They are found on the sunny side of rosaceous shrubs, so far, in order of frequency, Blackthorn, Hawthorn, Domestic Apple and Dog Rose. However, it grows on other types of trees or shrubs in other parts of the world and Vince Giavarini, found it on a windblown Oak twig in the Poole area. It has most frequently been found close to the sea and raised pH from wind blown salt was observed as a positive factor it its distribution at Keyhaven; this has also been observed in Brittany. Vince has observed that dust, especially from roads is also a positive factor in raising the pH in inland sites. It seems to typically avoid the most eutrophicated situations, with Xanthoria parietina totally dominant, and is most often found in communities with mixtures of highly nutrient tolerant species such as Xanthoria and Physcia adscendens and less nutrient resistant grey Ramalina species and, most significantly, Evernia prunastri. The latter lichen is regarded as a good negative indicator of eutrophication, so the frequent presence of this species with Goldeneyes in the largest colonies does support the low estimation of its tolerance of eutrophication in ITALIC. It may require reasonably high pH bark, but has a lower tolerance of ammonia pollution. The Irish sites rediscovered by Vince are in similar communities.

Why Has Goldeneyes Colonised?

With the above in mind I had a look at some of the climate maps available on the Met Office website. There were no 10 year averages, which would have been useful, but the year 2007, about the time when the colonisation must have been getting under way, seemed the most informative.

The core area of recent colonisation (and of historic occupation) can be best characterised as a combination of the sunniest and warmest part of the county, which is also quite humid. Further north east is warmer but drier and less sunny, further west is cooler and also less sunny.

Why was Goldeneyes lost from this favourable area in spite of being present here in the depths of the Little Ice Age and surviving right through to at least the end of the 19th century? My thought is that it was actually lost to acidifying pollution in the early 20th century, with only spasmodic unsuccessful colonisation occurring in clean air, but less sunny and cooler, areas to the west. With declining acidification, along with the the boost provided by warmer weather at the end of the last century, this very mobile lichen has been able to colonised back into its historic English heartland.

The maps also suggest to me that Goldeneyes should also be looked for further west along the coast as far as east Devon to about Torquey.

Neil A Sanderson 1/5/2013 (with thanks to Vince Giavarini for comments)