Greater prairie-chickens (Tympanuchus cupido pinnatus) were once found throughout the tallgrass prairie of midwestern North America but over the last century these prairies have been lost or fragmented by human land use. As a consequence, many current populations of prairie-chickens have become isolated and small. This fragmentation of populations is expected to lead to reductions in genetic variation as a result of random genetic drift and a decrease in gene flow. As expected, we found that genetic variation at both microsatellite DNA and mitochondrial DNA (mtDNA) markers was reduced in smaller populations, particularly in Wisconsin. There was relatively little range-wide geographical structure (FST) when we examined mtDNA haplotypes but there was a significant positive relationship between genetic (FST) and geographical distance (isolation by distance). In contrast, microsatellite DNA loci revealed significant geographical structure (FST) and a weak effect of isolation by distance throughout the range. These patterns were much stronger when populations with reduced levels of genetic variability (Wisconsin) were removed from the analyses. This suggests that the effects of genetic drift were stronger than gene flow at microsatellite loci, whereas these forces were in range-wide equilibrium at mtDNA markers. These differences between the two molecular markers may be explained by a larger effective population size (Ne) for mtDNA, which is expected in species such as prairie-chickens that have female-biased dispersal and high levels of polygyny. Our results suggest that historic populations of prairie-chickens were once interconnected by gene flow but current populations are now isolated. Thus, maintaining gene flow may be important for the long-term persistence of prairie-chicken populations.

The number of greater prairie-chickens in Wisconsin has decreased by 91% since 1932. The current population of approximately 1500 birds exists primarily in four isolated management areas. In previous studies of the Wisconsin populations we documented low levels of genetic variation at microsatellite loci and the mitochondrial DNA control region. Here we investigate changes in genetic structure between the four management areas in Wisconsin over the last 50 years. We estimated the harmonic mean effective population size (Ne) over the last 50 years by comparing allele frequencies from the early 1950s with those from contemporary samples. Using a pseudo-likelihood approach that accounted for migration, estimates of Ne (15-32 prairie-chickens within each management area) were 10 times lower than census numbers from booming-ground counts. These low estimates of Ne are consistent with increased habitat fragmentation and an increase in genetic isolation between management areas over the last 50 years. The reduction of gene flow between areas has reduced Ne, increased genetic drift and, consequently, reduced genetic variation. These results have immediate consequences for the conservation of the prairie-chicken, and highlight the importance of how mating systems and limited dispersal may exacerbate the loss of genetic variation in fragmented populations.

Translocations are becoming increasingly popular as appropriate management strategies for the genetic restoration of endangered species and populations. Although a few studies have shown that the introduction of novel alleles has reversed the detrimental effects of inbreeding over the short-term (i.e., genetic rescue), it is not clear how effective such translocations are for both maintaining neutral variation that may be adaptive in the future (i.e., genetic restoration) and increasing population viability over the long-term. In addition, scientists have expressed concerns regarding the potential genetic swamping of locally adapted populations, which may eliminate significant components of genetic diversity through the replacement of the target population by the source individuals used for translocations. Here we show that bird translocations into a wild population of greater prairie-chickens (Tympanuchus cupido pinnatus) in southeastern Illinois were effective in both removing detrimental variation associated with inbreeding depression as well as restoring neutral genetic variation to historical levels. Furthermore, we found that although translocations resulted in immediate increases in fitness, the demographic recovery and long-term viability of the population appears to be limited by the availability of suitable habitat. Our results demonstrate that although translocations can be effective management tools for the genetic restoration of wild populations on the verge of extinction, their long-term viability may not be guaranteed unless the initial conditions that led to most species declines (e.g., habitat loss) are reversed.

Over the last century, populations of the Greater Prairie Chicken ( Tympanuchus cupido ) have declined or gone extinct throughout midwestern North America. In Wisconsin the population declined by 50% from 1951 to 1961 and has remained at low (1500 individuals) but fluctuating levels for the past 40 years. We examined historic (1951) and contemporary (1996-1999) populations of prairie chickens in Wisconsin to determine whether there was a loss of genetic variation following the population bottleneck. We compared microsatellite DNA variation at six loci in historic (1951, n ϭ 47) and contemporary (1996-1999, n ϭ 87) populations. Population mean heterozygosity and number of alleles per locus were significantly lower in the late 1990s than in 1951. This loss of genetic variation following a population bottleneck is consistent with the results of a similar study in Illinois, but we found no evidence of a reduction in hatching success.Pérdida de Variación Genética en Tympanuchus cupido Después de un Cuello de Botella Poblacional en Wisconsin, EE.UU. (1996)(1997)(1998)(1999) de Tympanuchus cupido en Wisconsin para determinar si había una pérdida de variabilidad genética después de un cuello de botella poblacional. Comparamos la variación de ADN microsatélite en seis loci en poblaciones históricas (1951, n ϭ 47) y contemporáneas (1996-1999, n ϭ 87). La heterocigosidad y el número de alelos por locus fueron significativamente más bajos hacia finales de los años 90 que en 1951. Esta pérdida de variación genética posterior al cuello de botella poblacional es consistente con los resultados de un estudio similar en Illinois; sin embargo, no encontramos evidencia de una reducción en el éxito de incubación. ‡ Address correspondence to P. Dunn, Resumen: A lo largo del último siglo las poblaciones de pollos de la gran pradera ( Tympanuchus cupido ) han disminuido o se han extinguido en el Oeste medio de Norteamérica. En Wisconsin la población disminuyó un 50% entre 1951 y 1961 y se ha mantenido a niveles bajos (1500 individuos) pero fluctuantes durante los últimos 40 años. Examinamos las poblaciones históricas (1951) y contemporáneas

Population introduction is an important tool for ecosystem restoration. However, before introductions should be conducted, it is important to evaluate the genetic, phenotypic and ecological suitability of possible replacement populations. Careful genetic analysis is particularly important if it is suspected that the extirpated population was unique or genetically divergent. On the island of Martha's Vineyard, Massachusetts, the introduction of greater prairie chickens (Tympanuchus cupido pinnatus) to replace the extinct heath hen (T. cupido cupido) is being considered as part of an ecosystem restoration project. Martha's Vineyard was home to the last remaining heath hen population until its extinction in 1932. We conducted this study to aid in determining the suitability of greater prairie chickens as a possible replacement for the heath hen. We examined mitochondrial control region sequences from extant populations of all prairie grouse species (Tympanuchus) and from museum skin heath hen specimens. Our data suggest that the Martha's Vineyard heath hen population represents a divergent mitochondrial lineage. This result is attributable either to a long period of geographical isolation from other prairie grouse populations or to a population bottleneck resulting from human disturbance. The mtDNA diagnosability of the heath hen contrasts with the network of mtDNA haplotypes of other prairie grouse (T. cupido attwateri, T. pallidicinctus and T. phasianellus), which do not form distinguishable mtDNA groupings. Our findings suggest that the Martha's Vineyard heath hen was more genetically isolated than are current populations of prairie grouse and place the emphasis for future research on examining prairie grouse adaptations to different habitat types to assess ecological exchangeability between heath hens and greater prairie chickens.