Portuguese native Artemia parthenogenetica resisting invasion by Artemia franciscana — Assessing reproductive parameters under different environmental conditions

There is widespread interest in the conservation of native Artemia biodiversity. In Portugal, only two known populations of native Artemia remain: one in the Rio Maior salina, the other in the Aveiro salina complex, both of the diploid Artemia parthenogenetica species. All other Portuguese hypersaline environments where Artemia can be found have been invaded by Artemia franciscana, which has eradicated the native strains. Invasiveness and resilience of, respectively, exotic and indigenous species are thought to depend on strain-specific traits and adaptation to local conditions. This work evaluates the reproductive performance of the two Portuguese native strains and the invasive species exposed to different salinities, temperatures, photoperiods and food supplies. Reproduction periods, quantity and quality of offspring varied significantly, depending on both the Artemia strain and environmental conditions. A. parthenogenetica from Rio Maior reproduced better than A. franciscana at high salinity (150) and low food supply, which may reflect an adaptation to its biotope that aids its resistance to invasion. But A. parthenogenetica form Aveiro performed much worse than its invasive competitor, under most of the conditions tested. It is unlikely that A. franciscana has not been introduced in this salina by chance alone. Other biological traits of the local A. parthenogenetica or adaptation to unstudied local factors (e.g. pollution) are probably responsible for this strainʹs survival. Further knowledge on specific local conditions and trait-specific tolerances to biotic and abiotic conditions are needed to understand (non-)invasion patterns and preserve the remaining native populations.