Resource use in native and imported populations of the red wood ant Formica paralugubris
Project Number: CH-6231
||01/01/2017 - ?
||Universiy of Florence
||Signor Giacomo Santini
Department of Biology
Univeristy of Florence
Via Madonna del Piano 6
IT-50019 Sesto Fiorentino
Phone: 055 4574721
red wood ant, Formica paralugubris, imported populations
Red wood ants belong to the subgenus Formica sensu stricto or F. rufa group, with seven species described in Europe and up to 19 species reported in North America (Stockan and Robinson 2016). The majority of European species are ecologically dominant, and have a key role in the structure and functioning of arthropod communities in temperate and boreal forests (Punttila et al. 2004). In Italy, red wood ants are restricted to the Alps with the only exception of F. pratensis, which also sporadically occurs in the Apennines (Baroni Urbani 1964; Pavan et al. 1971).
Since the mid 1900s, red wood ants were employed as biological control agents in many European countries, such as Germany and Italy (Gösswald 1950; Pavan 1959). Colonies of F. aquilonia, F. rufa, F. polyctena and, in particular, F. lugubris and F. paralugubris, were repeatedly transplanted from their original areas in the Alps to other sites where they were formerly absent. In Italy, the majority of introductions occurred in the Apennines mountains, where climatic conditions provided suitable habitat to these cold-climate species. Few transplants were also conducted in warmer areas, such as Sicily, Sardinia and Elba Island. In 1971, F. paralugubris was also intentionally introduced to one site in Canada (Valcartier, Quebec) (Finnegan 1975). The original sites where the nests were collected lay in the provinces of Bergamo and Brescia, in the Lombardia region, between 1100 and 1700 meters altitude. The sampling forests are prevalently formed by fir, spruce and beech trees. Information on nest density and size in the collection sites are limited, but available records report density values ranging from 4-5 to 20-30 nests per hectare, with average nest size around 150-200 cm in basal diameter and 100-150 cm height. The last available survey of nest distribution and size in one of these sites, the ‘Giovetto delle Palline’ Nature Reserve (Ronchetti and Groppali, 1995), showed values comparable to previous ones, suggesting a temporal stability of the populations.
The current status of most of the introduced populations is unknown, although in a few cases extinction has been documented, especially in less suitable and warmer areas (Ronchetti and Groppali 1995). However, some of the populations introduced on the Apennines have grown considerably. For example, Figures 1 and 2 show an increase in both the number of nests and total nest volume recorded in some of the populations introduced to the Campigna Forest (Foreste Casentinesi National Park), one of the most affected areas in Italy. According to Storer et al (2008), the colony introduced to Valcartier had, at the time of his study, spread over a forested area of 3.8 ha and grown to a supercolony of 95 living mounds with an estimated population of 8 million workers.
Red wood ants are potentially harmful when introduced in areas that are not part of their native habitat. There is extensive literature on the negative ecological effects of many of these species on other organisms including arthropods (e.g. Cherix and Bourne 1980; Heads 1986; Gridina 1990; Laakso 1999; Reznikova and Dorosheva 2004; Hawes et al. 2002), birds (Haeming 1992, 1994; Aho et al. 1999) and plants (Punttila et al. 2004; Kilpelainen et al. 2009; Wardle et al. 2011).
Stable Isotopes Analysis (SIA) is a useful tool in ecological studies. In particular, carbon and nitrogen stable isotopes have been widely used in trophic ecology in order to determine the diet, trophic position and niche characteristics of a species (e.g. Peterson and Fry 1987; Post 2002; Fry 2006; Newsome et al. 2007). Along a food chain, a consumer is expected to show an enrichment in isotopic ratios with respect to his food. In general, the nitrogen isotopic signature indicates the trophic level of a species, while the carbon signature provides information on the main carbon sources (e.g., C3 vs C4 plants, since they have different signatures).
In invasion biology, stable isotopes analyses can be used to infer the degree of niche overlap between native and invasive species, thus elucidating the potential impact of introduced species on local communities (e.g., Vander Zanden et al 1999). In ant ecology, SIA was used to examine the trophic structure of ant assemblages (e.g. Gibb and Cunningham 2011), or unveil the details of the trophic behavior of some species (e.g. Brewitt et al. 2015). As for invasive ants, SIA allowed to describe ecological interactions among species (e.g. Resasco et al. 2012; Iakovlev et al. 2017; Roeder and Kaspari 2017), and to reveal important determinants of the invasion success. For example, Tillberg et al. (2007) reported a progressive decrease in the trophic level of the Argentine ant, Linepithema humile, during its invasion history. Similarly, Wilder et al (2011) showed a greater consumption of aphid honeydew by the red imported fire ant, Solenopsis invicta, in the introduction areas than in its native range of distribution. The increase in carbohydrate provisioning, obtained through mutualistic partnerships with other organisms, represents a critical resource that may boost the success of these invasive species.
The main aim of this project is to provide information on the ecology of Formica paralugubris, comparing sites where this species naturally occurs and sites where it has been imported. In particular, we wish to understand if transplant to new habitats determined a shift in resource use comparable to that observed in other invasive ant species. This information would be crucial to understand the likelihood of expansion of this species to nearby habitats, and the resulting impact on autochthonous communities.
Last update: 10/5/17
Source of data: ProClim- Research InfoSystem (1993-2020)
Update the data of project: CH-6231