Effects of water temperature on life history traits of selected South African Aquatic insects: implications for the ecological reserve

Includes bibliographical references.Life-history studies have informed all areas of aquatic ecological research, whilst also providing information relevant for conservation and management of aquatic systems. Given the large research gap that has existed in this regard for Southern Hemisphere lotic systems, there has been an urgent need to gather such data if effective management policies are to be implemented regionally, especially in the face of ongoing development, anthropogenic impacts, and global climate change. Furthermore, there has been a growing awareness of the need to incorporate thermal guidelines into legislation regarding environmental flows and associated water management plans. In South Africa radical new legislation introduced in 1996 resulted in rivers and aquatic ecosystems being given a right to water of their own- essentially environmental flows, required to protect the aquatic ecosystems associated with the water resource, that are determined separately for all or part of any significant water resource. This water, including both the quantity and quality, is referred to as the "Ecological Reserve." Baseline information on the relationship between temperature and life-history patterns of aquatic insects is required to inform the incorporation of thermal guidelines in the Ecological Reserve determination process. Assuming such information can be gathered, a problem arises as to how the data can be interpreted and incorporated into management guidelines. For instance if representatives of widespread species occurring throughout a country are collected from a single location (say perhaps a single province in South Africa) and then analysed in terms of their thermal limits for growth – would these limits hold true for that same species where it occurs elsewhere? Intra-specific variability, cryptic species and broader phylogenetic constraints all influence the thermal limits of species and need to be considered when examining thermal influences on life-history patterns. This thesis aimed to test the overarching hypothesis that while the life-history traits of aquatic insects could be constrained to some degree by their evolutionary history, they would also be impacted by thermal and hydrological regimes, inducing a degree of plasticity in their life cycles. This hypothesis was tested by examining the key life-history traits of three representative taxa of aquatic insect, namely Lestagella penicillata (Ephemeroptera), Aphanicercella spp. (Plecoptera) and Chimarra ambulans (Trichoptera), and how they are driven by environmental and genetic factors in six rivers situated in the south-western Cape Province of South Africa