Frequencies of multiple paternity in three Acrocephalus species (Aves Sylviidae) with different mating systems (A. palustris, A. arundinaceus, A. paludicola)

Genetic parentage was determined by DNA-fingerprinting with multilocus prob es and microsatellite PCR in three Acrocephalus species with different mati ng systems: the socially monogamous marsh warbler (A. palustris), the polyg ynous great reed warbler (A. arundinaceus) and the promiscuous aquatic warb ler (A. paludicola). The amount of extra-pair paternity (EPP)/multiple pate rnity (MP) was then related to ecological parameters (increasing productivi ty) and parental care (decreasing male participation) of Acrocephalus speci es. Marsh warblers (33 broods, 131 young plus putative parents) were studie d over 3 years in a German population. No case of social polygyny but four extra-pair young (EPY) were detected in three socially monogamous broods. T he low frequency of extra-pair fertilization (EPF, 9.1% of broods, 3.1% of offspring) may be best attributed to intense male mate-guarding and restric tions on mate assessment due to an extremely short breeding window. The rat e of social polygyny in a German great reed warbler population varied betwe en 8 and 35% of males during a 5-year period. In 48 broods (27 monogamous a nd 21 polygynous males) with 194 young, 5 nests (3 of polygynous, 2 of mono gamous males) with 19 EPY were recorded: EPF-rates are 10.4% of broods and 9.8% of offspring. In none of the nests were neighbouring males the genetic fathers, but in 2 nests, "bachelor" males from distant territories had sir ed the offspring. The EPP-rate in this species seems to be related to an in complete correlation between male and territory characteristics leaving som e females to correct their choice. Aquatic warblers were studied during thr ee years in a Polish population. In each of the years, MP was recorded in m ore than half of a total of 75 broods (mean 76%). The proportion out of 340 young sired by one to five "additional" males varied between 25 and 57% (m ean 39.1%). Food resources are neither critical nor economically defendable in the species' habitat and paternity assurance behaviours of males and fe male choice are yet not fully understood.