KEYNOTE: Ecological significance of wood ants 

Jouni Sorvari 

Department of Biology, Section of Ecology, University of Turku, Finland. 

Wood ants of the Formica rufa group have ecological effects that extend over several trophic levels in forest ecosystems. They affect soil nutrition levels and carbon cycles by collecting organic material (nest building material, honeydew, and prey invertebrates) to their large nests. Wood ants disperse seeds of many plants and they may also spread some mosses. They can affect the growth of trees negatively by tending aphids, and positively by preying on herbivores. They are one of the dominant generalist predators of other arthropods; thus affecting the composition of arthropod communities. By strong resource competition they can affect the breeding success and nestling quality of insectivorous birds. Wood ants form a significant part of the diet of some vertebrates e.g. bears and woodpeckers. They are behaviourally dominant among ants affecting the distribution and abundance of other ant species. Their nest mounds are shared with numerous other arthropods, of which some can live only in wood ant nests (so called myrmecophiles). In addition, earthworm density can be higher in wood ant mounds than in surrounding forest floor. 

Wood ants are bound to trees and forests, especially the multiple nesting i.e. polydomous species/populations that need large forest patches for habitat. In many European countries such forests have become increasingly rare due to the spreading of urban settlements and agriculture. This habitat loss is the major factor threatening the existence of wood ants. In addition, industrial pollution and destructive forest management practices (clear-cutting) have negative effects on wood ant populations. In many countries wood ants are strictly protected by law while in some countries they are not protected at all. Because of their importance in forest ecosystems, the welfare of wood ant populations should be taken into account in land use planning, even in countries where they are still common. 

Nest mate recognition in the Narrow headed ant Formica exsecta 

Stephen J Martin 

Department of Animal and Plant Sciences, University of Sheffield, UK

It has been known for over 100 years that ants use chemicals found on their skin to distinguish friends (nest mates) from foes (non-nest mates). However, it is only in the past 30 years that the development of highly sensitive methods like Gas-chromatography-mass spectrometry have allow us to detect the minute amounts of chemicals that exist on the surface of ants. During the past ten years 1000’s of compounds have been detected from just 80 ant species. A major chemical class produced by ants are the cuticular hydrocarbons. These are simple molecules but occur in a vast array of forms making them suitable recognition compounds. The Narrow headed ant Formica exsecta has a very simple cuticular chemical profile and workers are very defensive on their mounds’ surface, so are ideal species with which to decode a nest mate recognition system. This is important since distinguishing nest mates from non-nest mates underlies key animal behaviours, such as territoriality, altruism and the evolution of sociality.  We found using aggression bioassays and synthetic compounds that worker aggression is only elicited by one part of the chemical profile.  A study of over 100 colonies found that every colony has a unique colony specific Z9-alkene hydrocarbon profile. Now we understand how F. exsecta encodes its nest mate signal i.e. within its Z9-alkenes, we have found that colonies headed by a single queen have a very diverse and distinct colony profile, but this is lost when many queens are present in the same colony and this explains the observed levels of colony aggression that may affect introduction programs.   

Wood ants and tree chemistry: effects on crown invertebrates 

Jenni Stockan & Glenn Iason 

The James Hutton Institute, Craigiebuckler, Aberdeen, UK. 

Within pinewoods, there is considerable genetically-based variation between individual trees including in the chemical composition of monoterpenes in particular: some trees contain 3-carene in their needles whilst other trees contain none. These volatile compounds have been demonstrated to act as toxins to invertebrate herbivores, repelling or even killing them. However, the relationship between tree chemistry and crown invertebrates is not a straightforward one and is further complicated by the presence of wood ants. Wood ants (Formica aquilonia and F. lugubris) are known to influence the populations of many crown-dwelling invertebrates. One of the best known examples is the mutualism between wood ants and honeydew-producing aphids. This is often termed a keystone interaction because the variation or occurrence of the interaction can have consequences for other organisms, particularly other invertebrates living in the tree crowns.  

We attempted to disentangle this three-way relationship between tree chemistry, crown invertebrates and wood ants. Within the native forest of Ballochbuie in north east Scotland, 45 trees were visited on a monthly basis over two years, and their ant foraging activity monitored. The crown invertebrate community was qualified by experimentally enclosing branches in insect proof nets on trees used by ants compared with trees not used by ants. More than half our trees were regularly foraged by ants with aphid honeydew dominating the diet. However, a large number of prey items were also removed from the tree canopies. Trees with zero 3-carene contained higher populations of crown (non-aphid) invertebrates than trees that contain 3-carene in their needles, but this effect is only evident when ants do not forage in the tree. These results demonstrate the complex interactive effects of tree chemistry and the presence of ants on crown invertebrate populations. As ecosystem engineers wood ants have strong effects not only on forest ecosystem function, but also on biodiversity which should be considered when planning and planting new forests.

Reproductive strategies of Formica lugubris, a sympatric sibling species of Formica paralugubris

Arnaud Maeder 

Museum of Natural History, Switzerland.

In this work we compared mating and dispersal abilities of the socially polymorphic Formica lugubris (either monogynous or polygynous) with its sympatric sibling species, the obligately polygynous F. paralugubris. During nuptial flight period we conducted semi-natural experiments with males and gynes collected on nest surface in Swiss mountains (Jura, Alps). We used two treatments: a) possibility or not to mate, b) possibility or not to fly. Gynes were examined for dealation (wing loss), insemination status and fat content. F. lugubris gynes from monogynous/monodomous populations revealed high dispersal and survival abilities: they always kept their wings, did not mate when unable to fly and had as much fat reserves as gynes found on mating places. F. lugubris gynes from polygynous/polydomous populations had lower lipid reserves and display a reproductive behaviour close to the local non dispersing strategy of F. paralugubris (early dealation even without mating, insemination without flight activity and low fat reserves). We also tested Temporary social parasitism (TSP) by introducing F. lugubris gynes into queenless or queenright artificial host colonies (F. S. lemani) and Intraspecific adoption¹ by introducing F. lugubris gynes into foreign nests (native population). After their artificial nuptial flight in the “Nuptial flight Ant Tent”, F. lugubris gynes from monogynous/monodomous population showed a high TSP success compare to the lower score of gynes from polygynous/polydomous colonies. Furthermore, only F. lugubris gynes from monogynous/monodomous populations had as much fat contents as gynes found in wild Serviformica nests. Intraspecifically, gynes were accepted to a high degree both in polygynous and monogynous nests but only as long as sexuals were produced in the nest (all gynes introduced later were killed). These results are in accordance with our spatial distribution analysis and suggest that wood ant gynes from polygynous/polydomous population rarely disperse and mate within their nests whereas gynes from monogynous/monodomous population rather disperse and perform TSP. Therefore, conservation measures directed toward wood ants should try to preserve a high habitat diversity level which is necessary to the maintenance of alternative dispersal strategies (mixed mating and founding system) and the related intraspecific social polymorphism. 

¹After dispersal, gynes can either start new societies by interspecific temporary social parasitism (TSP) or be adopted intraspecifically (= intraspecific adoption).

The conservation status of Formica rufa and Formica lugubris in northern England and the Midlands

Elva Robinson

Department of Biology, University of York, UK.

The two most widespread wood ant species in Britain are Formica rufa (the red wood ant) and Formica lugubris (the northern or hairy wood ant). F. rufa has a southern distribution within England, while F. lugubris is found in the north of England and in Scotland (Edwards and Telfer 2002). Both species are considered ‘Near Threatened’. Decline is likely to be most evident at the population margins. The midlands and north of England cover both the northern margin of F. rufa and the southern margin of F. lugubris, so these areas were surveyed to assess the populations. Historical records were used to identify former wood ant populations. This survey focussed on breadth of coverage of wood ant populations (82 sites) and this necessarily comes at the expense of detail about any one population. 

For both species, 60-70% of historical records were confirmed. The details of the picture differ however. The overall pattern seems to be that F. rufa is struggling at the northern edge of its range, while F. lugubris is doing well at its southern range edge. This view is at odds with the general climate-change driven pattern of species shifting their distributions north, as conditions become more clement. This may suggest that local weather patterns, habitat fragmentation and habitat loss are more significant drivers of extinction for wood ants than overall changes in climate. It may also indicate that F. lugubris are better climatic generalists, adapted to survive poor weather, but tolerant of warmer spells, whereas F. rufa may be better adapted to warmer climes, but more likely to be injured by periods of adverse weather. There was no evidence that either species is competitively excluding the other. Almost all the populations surveyed appeared to be healthy, in so far as multiple nests were present, these nests well-maintained by their inhabitants and numerous foragers were evident. Due to the lack of detail in most of the historical records with which to compare the current survey results, it was not possible to assess changes in population health. Detailed longitudinal studies of the size and vigour of wood ant populations which can be used for comparisons in future are required.

Red wood ants in Switzerland – thirty years of research 

Daniel Cherix  

Department of Ecology and Evolution, University of Lausanne, Switzerland. 

For nearly thirty years we have been involved in the study of red wood ant biology and ecology. An important part of this work was done after the discovery in 1973 of a super-colony of Formica lugubris (as identified at this time) in the Swiss Jura mountains.  This was an excellent opportunity to study the relationships between nests within a polygynous and polydomous system. Among the results we found that wood ants rely on spruce aphids not only for honeydew but also for food. Nearly one third of their prey were spruce aphids of the genus Cinara. At the same time contact with Finnish colleages (R. Rosengren, P. Pamilo) helped us to find a  new species of red wood ant in Europe: F. paralugubris. From there investigations into reproductive strategies helped us to understand  the differences between these species and directed us to the discovery of one of the first sexual pheromones produced by females to attract males. During this time, studies within the Swiss Alps on distribution and density of red wood ants as well as related species (Formica exsecta) was recently achieved with a new red wood ant species, the strange behaviour of which is still under study. A summary of this study programme conducted mostly but not only in Switzerland will be presented.

Long term monitoring on red wood ants in Switzerland: concept and methods 

Anne Freitag 

Museum of Zoology, Switzerland. 

Red wood ants (Hymenoptera Formicidae, Formica rufa group) have large impacts on forest ecosystems. Because of their ecological importance, they are protected by laws in many countries, including Switzerland. Despite this, some species are listed on the IUCN Red List of Threatened Species and on the Swiss Red List. Wood ants suffer from habitat fragmentation, intensification of forest management and practices such as clear-cuts. Lack of management in woodlands that become more and more shaded can also reduce habitat suitability leading to mounds being abandoned. Hence a good understanding of the effects of forest management on wood ants is needed to ensure their long-term conservation. Unfortunately, little is known about how nest mounds evolve in managed vs. unmanaged forests. 

In this context, we’ve undertaken a long-term monitoring of nest mounds in Switzerland to understand which factors influence their evolution and survival. The study will be conducted in two kinds of areas: a) exploited forests and b) “natural forest reserves” (= areas without forest exploitation) where we can follow the natural dynamic of nest mounds as control. The monitoring concerns the six wood ant species represented in Switzerland: Formica rufa, F. polyctena, F. pratensis, F. lugubris, F. paralugubris and F. aquilonia. 

We first developed a field protocol to collect standardized data on nest mounds and their neighbourhood that we present here. A “sample-unit” consists of a nest mound and the area around it (circle with 25 m radius). Parameters characterising the mound itself, the environment close to the ant nest (circle with 8 m radius) and the whole study area are measured, including potential stress factors and forestry operations. To achieve the long term monitoring, each nest mound will be surveyed every 1 to 5 years (depending on habitat stability) over a 10-year period.

 Red wood ants in the Alps: today situation and new species  

Christian Bernasconi¹, Pekka Pamilo² & Daniel Cherix¹ 

¹Museum of Zoology, Switzerland. 

²University of Helsinki, Department of Biological and Environmental Sciences, University of Helsinki, Finland. 

Due to their importance in forest ecosystems, red wood ants (Formica rufa group) are protected in many European countries. However, despite this protection, since 1983 they are classified as globally threatened species by the IUCN. To date, the F. rufa group includes six species: F. rufa, F. polyctena, F. lugubris, F. paralugubris, F. aquilonia and F. pratensis. However, because of their morphological similarity and ability to hybridize, the morphological identification of these species can be quite complicated. Therefore, the taxonomy of the group has been much debated during the past decades. Since correct species identification is fundamental in conservation biology, more reliable methods for species recognition are strongly recommended. 

We therefore conducted a multidisciplinary approach (based on DNA, sex pheromones and behaviour) to clarify the taxonomy of the group and to investigate the biodiversity of these ants within the Swiss National Park area (Eastern Swiss Alps), in which red wood ants are abundant. 

Our study provided new reliable tools for wood ant species identification, which will help in future biomonitorings of these protected species. Furthermore, our data revealed the existence of an undescribed cryptic species within the Swiss National Park and this would be of great interest in terms of biodiversity and of conservation of these protected species.

Present state of wood ants 

Jonathan Hughes 

Scottish Wildlife Trust, Cramond House, Edinburgh. 

Drawing on both published material and anecdotal evidence, this presentation will provide an overview of the distribution and conservation status of wood ants in the UK. It will then go on to discuss the 'key threats' to wood ants in the short (5-10 years), medium (10-30 years) and long term (50+ years). Particular focus will be given to addressing the key threats to Formica aquilonia, F. lugubris and F. sanguinea and F. exsecta in Scotland to ensure long term population viability.

Wood ants in Scotland: Conservation action 

Stephen Corcoran  

Cairngorms National Park Authority Grantown on Spey, UK. 

Action on four species of wood ants (Formica aquilonia, F. lugubris and F.sanguinea and F. exsecta) in Scotland started following their inclusion in the UK Biodiversity Action Plan process in 1999. A brief overview of the four species is given, covering distribution, ecology and action plans. Some examples of practical action for wood ants is presented including a recent translocation programme following the upgrading of the A9 trunk road. A review of the literature available on wood ants is presented, with a final summary of key action required to conserve and enhance wood ants in Scotland. 

Surveying for and monitoring the narrow-headed ant Formica exsecta in Scotland

Hayley Wiswell 

The James Hutton Institute, Craigiebuckler, Aberdeen, UK. 

The narrow headed ant (Formica exsecta) is listed as endangered on the UK's Red List and has a disjunct distribution in Britain, being found only at a single site in Devon, England and in three counties in Scotland. 

Current forest expansion schemes in the Cairngorms National Park do not favour this species due to its requirement for woodland edges and large open glades with short vegetation created by grazing. In many forest areas this habitat is under threat from tree regeneration and the narrow headed ant is considered to have a poor ability to disperse over large distances, making colonies even more vulnerable. Monitoring conditions surrounding nests is essential in order to assess the life span of existing colonies, but extensive surveys are needed in order to locate and map nests. The precise location of nests is also needed in order to ensure that they are incorporated into management practices. 

Surveys to find new nests were carried out during summer 2011 at Mar Lodge estate, Braemar (National Trust for Scotland) and Abernethy Forest National Nature Reserve (RSPB). Locating the nests of Formica exsecta is made difficult by the relative small size of nests mounds compared to wood ants and the small scale topography of the habitat in which it lives. 10m spaced transects across suitable habitat were sufficient to locate a significant number of nests on Tulloch Moor, Abernethy. 

At Mar Lodge, a monitoring method involving measurements of nest dimensions and surrounding vegetation heights on fixed bearings has been conducted every three years since 2005. Data collected suggests that on this estate vegetation height is increasing and some nests are at risk of pine regeneration. 

The pressure on land owners to reduce grazing levels and increase woodland cover makes management for this species challenging. However, this species should be a flagship for woodland diversity, as management of woodland mosaics with open glades will benefit a range of other species as well.

Promoting recording of wood ants

Glenn Roberts 

NESBReC, University of Aberdeen, UK. 

In the UK there is a vast amount of biodiversity data collected by individuals and organisations. This information is crucial in understanding the abundance and distribution of species and habitats. Without it, making decisions to protect UK wildlife would be much more difficult. The UK government, local government and non-governmental wildlife-related conservation agencies all use this data. One of the main ways of collating and interpreting this data is through local recording centres of which the North East Scotland Biological Records Centre (NESBReC) is one. Wood ants and related species, although often conspicuous within forests, have traditionally been under-recorded. This has lead to mis-interpretaions about the rarity of certain species. This presentation will outline the importance of biological recording and the role of recording centres.

Forestry design and management

Giles Drake-Brockman 

Forestry Commission Scotland, Inverness, UK.

Forestry is very important to Scotland as a contributor to industrial and rural economies through timber and tourism. But forests and woodlands are also the custodians of landscapes and many habitats and species which are vulnerable to change.

The role of the forest and changed significantly over the last 30 years in response to increased awareness, social demands and scientific research. Single focus timber plantations are being replaced by forests that function for a much wider audience and increasingly they site side by site with restoring native woodlands, open habitats, public access and social developments, such as hydro-energy schemes.

Wood ants represent one important component of a forest, but forest managers have to plan for a multitute of competing demands.

Forest planning and probably become the single most important activity in a moder forester's skill base. Forest planning provides the mechanism which brings together the needs of competing demands and sets priorities for implementation.

Planning does not stop at the production of a map. A plan has to be delivered and forest teams have developed processes to ensure that each individual site is assessed for specific species interest and approriate action is taken to reduce impacts or mitigate.

“But they’re only ants!” 

Alison Greggans 

RSPB Abernethy National Nature Reserve, Forest Lodge, Nethybridge, Inverness-shire, UK.

“Why is it that everywhere you put a sign post for walks, ants start building nests!” 

It’s obviously a problem for this warden, that wood ants exhibit their incredible building skills right on the footpath’s edge – with disastrous results! I’m advocating on behalf of the ant here, rather than this beleaguered warden.

But:

• They’re only ants
• They’re not terribly sexy or cute
• They sting, bite, crawl all over you
• They get in your pants
• They swarm and so need kettles of hot water poured over them to stop them getting out of control! 

 Challenging deep seated and misguided perceptions is crucial if wood ants are to receive the accolade they deserve for their ecological service to undisturbed pine woods. Anecdotes from various people from the conservation sector clearly demonstrate negative perceptions toward the humble wood ant. In some instances, this negativity drives an otherwise amenable and deferential visitor toward vandalism! The jury is out as to whether it’s sheer wickedness or high-spirited interest that causes “ants nests to have their windows continually put in” (as it where). 

The presentation also bears witness to the herculean efforts from colleagues to protect and restore wood ant nests and promote the image of these little solar power engineers. 

So, if you relish the chance to;

• reflect on best practices
• share ideas
• provide a forum to support a strategic approach to enhancing public interest about wood ants ...

...then please come along and participate in this pre-lunch 15 minute presentation.