The population genetic structure of the Greater Rhea ( Rhea americana) in an agricultural landscape

Abstract

Although population genetic structure and geographic differentiation have been reported for many bird species with insular distributions, high vagility typically results in high levels of gene flow and thus little local differentiation among continental populations. This study provides the first survey of population genetic variation in a South American ratite, suggesting that, in an agricultural landscape, recent fragmentation and isolation may affect the genetic structure of flightless bird species. Using randomly amplified polymorphic DNA (RAPD) analysis, I evaluated the population genetic structure of the greater rhea, Rhea americana albescens, by quantifying genetic variability within and among four isolated wild populations located in a highly fragmented region of the Argentinean Pampas. Levels of genetic diversity of the natural populations were compared to those of a captive population used as an inbred “control.” An analysis of molecular variance (AMOVA) based on a phenotypic analysis of 54 RAPD markers showed that 94.38% of the total observed variance was explained by differences within populations ( P<0.001) whereas 6.37% was due to differences among populations ( P=0.006). In addition, measures of genetic diversity (D: mean genetic diversity, and P: percentage of polymorphic bands) estimated for the wild populations were similar to those of the inbred “control.” The pattern of genetic variation reported combined with data on the sizes of eight wild populations and the reproductive success of a focal population are consistent with the idea that relatively recent fragmentation and isolation may have increased local genetic differentiation and decreased within-population levels of genetic variation as a result of genetic drift and inbreeding.