Bioecology of large Branchiopods in Central District, Botswana

The bioecology of large branchiopods in Central District, Botswana, was analysed to

determine if genetic relatedness or environment of origin determined the thermal

physiology of large branchiopods. Two temporary wetland types (Rock-pools and

Pans) were identified and their thermal conditions characterised. Temperatures

experienced in each wetlands type were measured for synchronised periods spanning

both dry phases and hydroperiods of the temporary wetlands. Anostraca and

Spinicaudata specialists from each temporary wetland were then identified and their

thermal physiology assessed. Physiological thermal fitness of large branchiopods were

measured using critical thermal limits and thermal preferences. Finally, the effect of

light and temperature on dormant cysts of a dominant large branchiopod were

assessed. Streptocephalus cafer dormant cyst hatching success was analysed using

variable temperatures and light durations. The thermal properties of rock-pools and

pans were grouped according to wetland type, highlighting the thermal differences

between these different temporary wetland types. Rock-pools experienced high

temperatures compared to pans in general. However, thermal physiologies of large

branchiopods differed according to taxonomic orders in thermal limits. Spinicaudatans

were tolerant to higher temperatures than anostracans. The results for thermal limits

and thermal preference differed across species. The hatching success of S. cafer was

optimal at 27 °C in 12hrs:12hrs light:dark regime. In conclusion, the thermal

physiologies of large branchiopods appear to primarily determined by genetic

relatedness with the environment of origin being secondary. While not part of the thesis

itself, the opportunity to describe the complete mitochondrial DNA of the studied

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species was also taken, to aid in resolving phylogenies for these understudied taxa.

These results are presented as supplementary material (See files S1-3).