The Effect of Habitat Condition and Vegetation on the Moth Communities of the Limestone Habitats at Hutton Roof and Farleton Knott Sites of Special Scientific Interest, North West England

Patton, Justine and Menendez Martinez, Rosa and Wilby, Andy (2022) The Effect of Habitat Condition and Vegetation on the Moth Communities of the Limestone Habitats at Hutton Roof and Farleton Knott Sites of Special Scientific Interest, North West England. Masters thesis, Lancaster University.

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Abstract

Moths in western Europe have seriously declined since the mid-20th century, mirroring the trends seen in other insect groups. The drivers of decline are multifarious, with agricultural intensification, habitat loss and degradation, eutrophication and climate change being key factors. In the UK, Sites of Special Scientific Interest (SSSI) protect some of the rarest flora, fauna, and geological features and are of high conservation value. The designation protects against damage and development through maintaining ‘favourable’ condition. This thesis aimed to investigate how habitat type (grassland vs pavement), habitat condition (declining, recovering, favourable) and vegetation composition affects the moth communities of Hutton Roof and Farleton Knott SSSIs, NW England, by assessing moth samples and data on vegetation along with existing macro-moth trait data. Observed levels of species richness, estimated measures of moth diversity, functional diversity, community composition and trait composition did not differ between habitat types or habitat condition. Instead, the moth community and trait composition differed between SSSI units and reserves, being driven by forb cover. More woodland macro-moth species were sampled at the grassland habitat despite the limestone pavement supporting taller, woody plants, suggesting the vegetation surrounding the grasslands is a key driver. The findings highlight advancing stages of succession from undermanagement: encroachment is not being actively managed, and a lack of rotational livestock grazing is promoting swards dominated by rank grasses. The increased grass cover in place of forbs negatively affected moth species richness. The macro-moth community was represented by many ubiquitous species, with a range of complementary generalist life-history traits. A number of specialist moths have been identified at both reserves, some of which are locally abundant. Bryophytes, lichens, and algae play an important role at the limestone pavement habitat; there is potential for them to provide a medium in which to pupate, a food source for larval stages, support for plant species to develop in an extreme environment and have a positive effect on estimated moth diversity. Condition assessments fail to acknowledge the value of bryophytes and lichens in a water and nutrient limited environment. This thesis highlights the limitations of condition assessments that focus on vegetation, supporting the need for the integration of additional taxa.