Abstract:
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
2
species was also taken, to aid in resolving phylogenies for these understudied taxa.
These results are presented as supplementary material (See files S1-3).
