No evidence of genetic structure in two populations of a threatened grassland bird, the Strange-tailed Tyrant (Alectrurus risoria)

MAHLER, B.; DI GIACOMO, A. S.; DI GIACOMO, A. G.; KLIGER, R.; REBOREDA, J. C.; TIEDEMANN, R.

Cusco

Congreso; IX Congreso de Ornitología Neotropical; 2011

Ornitología Neotropical

We explored the effects of fragmentation on patterns of population structuring and genetic diversity in two populations of the Strange-tailed Tyrant (Alectrurus risoria), a globally threatened South American grassland species. Populations of endemic grassland birds have declined dramatically over the recent decades in southern South America where they now exist mostly in isolated fragments scattered in an agricultural matrix. The Strange-tailed Tyrant has suffered a large contraction reaching a 90% loss of its original range. Remnant populations are found in protected areas containing grasslands. Only two populations are left in Argentina, in areas that are approximately 400 km apart. We sampled 63 adult individuals from both areas, and genotyped these birds at 8 microsatellite loci. F-statistics showed no differentiation between both populations. Genetic diversity was similar for both fragments and was unrelated to fragment size or number of sampled individuals. The observed pattern may be explained by both connectivity through inter-fragment dispersal and retained ancestral polymorphism in both populations.