Interbreeding between two populations of Acartia californiensis (Copepoda : Calanoida): a laboratory study

Interbreeding between two populations (Estero de Punta Banda, Baja Californ ia, Mexico (PB) and Mission Bay California, USA (MB)) was tested using the live progeny (nauplii) of the marine calanoid copepod Acartia californiensi s, in a male to female ratio of 3:1. The laboratory conditions were 18 +/- 2 degrees C and a 12:12 h L:D cycle, during an experimental period of one w eek. The first filial progeny (F-1) present in the replicates were used in four combinational experiments (non-hybrids: PB-PB and MB-MB? and hybrids: PB-MB and MB-PB). To investigate the production of the F-2 generation, male s and females were selected from F-1 and 16 combinational experiments were conducted with five replicates each (non-hybrids: PBPB-PBPB and MBMB-MBMB, and hybrids: PBPB-MBMB, PBPB-PBMB, PBPB-MBPB, MBMB-PBPB, MBMB-PBMB, MBMB-MB PB, PBMB-PBPB, PBMB-MBMB, PBMB-PBMB, PBMB-MBPB, MBPB-PBPB, MBPB-MBMB, MBPB- PBMB and MBPB-MBPB). Statistical analysis for F-1 showed no significant dif ferences of the mean for live progeny between the non-hybrids and hybrids a nd between non-hybrids, but a significant difference between hybrids was fo und. For F-2, the mean live progeny between non-hybrids and hybrids, betwee n hybrids and between non-hybrids was found to be non-significant. These re sults show successful interbreeding between the populations studied.