The effects of land use change on the population expansion of a poor disperser, the wood ant Formica lugubris

Habitat fragmentation and destruction is one of the most likely causes of recent biodiversity losses. Anthropogenic land use change can create highly fractured landscapes, in which patches of original habitat become isolated. Fragmentation and the associated habitat loss, can result in species range contractions, species declines and extinctions. In the UK, areas of ancient woodland which formerly covered a large proportion of the land, are now highly fragmented and isolated due to human activities. Since the 1900’s, large scale afforestation of non-native conifer plantations has occurred across the UK. Assessing the expansion of forest species into this new habitat is crucial to understand the extent to which non-native plantations support native woodland biodiversity, especially as significant colonization lags can occur when new habitat is created. This is important when considering that plantation woodland may act as corridors between ancient woodland that have acted as refuges for many UK forest species. The hairy wood ant, Formica lugubris, is a forest specialist and considered to be an ecosystem engineer due to its role in shaping energy flow through woodland ecosystems. Further to this, F. lugubris mounds provide a crucial habitat for many myrmecophile species. In this thesis, I show how populations of F. lugubris are continuing to expand and colonise new areas of plantation on the North York Moors. The populations of F. lugubris at three different field sites were resurveyed across multiple field seasons. A combination of steady, slow, expansion and rapid expansion into new areas was seen, dependent on stand heterogeneity. At a unique site where detailed past forest management strategies are known, I show how row thinning could be used as a potential strategy in increasing wood ant colonisation. Using row thinning could potentially act as corridors to connect populations which have been isolated since the woodland was fragmented. Nest attribute and microhabitat data was collected for all nests within the row thinned area in order to see whether certain factors could predict nest survival. A predictive GLM was built and I found that nest volume was the most important predictor of nest survival in the following year. The results from this study show that populations of F. lugubris at the field sites are continuing to expand and suggests that row thinning may be a conservation strategy forest managers could utilise to conserve wood ants and aid their expansion. The nest data collected at the newly colonised areas could be used to inform parameters used in future dispersal models.