MULTIPLE PATERNITY IN BROODS OF AQUATIC WARBLERS ACROCEPHALUS-PALUDICOLA - 1ST RESULTS OF A DNA-FINGERPRINTING STUDY

Female Aquatic Warblers always care alone for their broods, whereas males are obviously emancipated from any duties. Prerequisite for the uniparental care of the nestlings is the high abundance of arthropods in the Carex vegetation inhabited by Aquatic Warblers. Both sexes strive for copulations with several partners. The reproductive success of the males, which advertize constantly throughout the entire breeding season, was analyzed in this study by DNA-fingerprinting. Blood samples were collected in 1990 in a study plot on the Biebrza marshes/NE-Poland from 70 nestlings of 18 broods, their respective mothers and 32 males. DNA-fingerprint analysis was performed with synthetic multilocus probes ([CAC]5 or [GAA]5) and immunological methods (anti-digoxigenin antibodies coupled to phosphatase) were employed to visualize hybridized DNA bands. Analyzing 70 nestlings, intraspecific nestparasitism could not be detected in any case, i.e. the female feeding at a nest was always the corresponding mother. Nine of 18 broods originated from one single father, while the other nine broads had two to four fathers respectively. Multiple paternity occurred in all broods with five and six nestlings, whereas we found single paternity exclusively in broods with two to four nestlings (p < 0.01; Fisher's exact test). In most broods with multiple paternity the involved males fathered only just one nestling. The degree of multiple paternity in Aquatic Warbler broods was very high: 58 % of nestlings origined from multiple paternity broods and 44 % of all broods were fathered by 3 or even 4 males. Taking all nestlings into account, the 'extra-pair' paternity rate was 36 %.