Biodiversity describes diversity at different levels of biological organisation,
including: habitat diversity; species diversity; and genetic diversity.
Understanding the processes that contribute to maintaining biodiversity is a
primary concern for both ecology and evolutionary biology. To this end,
research into the factors influencing the different levels of biodiversity
independently are widespread. However, little is understood about the
relationship between the different levels. This study investigates the patterns of
habitat, species, and genetic diversity in fragmented internationally important
calcareous grasslands, and analyses the spatial and temporal factors
influencing them. Finally, the relationship between these levels of biodiversity is
examined. Within the South Downs National Park study area, substantial
change to habitat diversity and landscape structure was measured between the
1930s and 2012. The transition of semi-natural habitat to agricultural land was
the predominate change. Loss of habitat between the 1930s and 2012 was
found to influence both species richness and species evenness of vegetation in
twelve calcareous grassland study sites. By contrast, none of the variables
examined explained the variation in species composition between sites. Further
analysis, at the genetic level, for two target species showed that the amount of
habitat loss was important in explaining the genetic variation in Cirsium acaule,
and soil nutrients were important in explaining the variation of Ranunculus
bulbosus. In contrast to the predictions of the species genetic diversity
correlation theory, no relationship was established between species and genetic
diversity. Similarly, no relationships were found between habitat diversity and
diversity at the species or genetic level. Although there were similarities in the
factors influencing different levels of biodiversity, habitat diversity, species
diversity, and genetic diversity appear to be responding independently to the
processes acting on them. As such efforts to conserve biodiversity should
consider the influence of conservation strategies on biodiversity holistically, and
not focus on a single measure
