Conservation genetics of the loggerhead shrike (Lanius ludovicianus) in central and eastern North America

This study examines geneticstructure of central and eastern North American Loggerhead Shrike (Lanius ludovicianus)populations. Samples derived from 27populations (n = 206) covering the range of threerecognized subspecies: L. l. migrans,L. l. ludovicianus, and L. l.excubitorides, and included locales from aputative intergrade zone between twosubspecies. For L. l. migrans, samplesinclude both those from extant populations andfrom museum specimens spanning approximately130 years. For all samples we obtained 267 basepairs of mitochondrial control region sequenceand identified a total of 23 distincthaplotypes. For a subset of samplesrepresenting a locale centered on the Canadianportion of an intergrade zone between migrans and excubitorides and locales onalternate sides of the intergrade, we obtainedadditional sequence for an intron of thenuclear glyceraldehyde-3-phosphatedehydrogenase gene. Analyses of temporal trendsin control region diversity of L. l.migrans populations indicate a diminutioncoincident with the decline in populationnumbers. Results from an Analysis of MolecularVariance on the control region data showed thata significant amount of total control regionspatial variation was apportioned among thethree subspecies (24.42%; P < 0.01). Furtheranalyses indicated statistically significantdifferences between eastern and westernpopulations of L. l. migrans. We found nosignificant differences among consideredpopulations in frequencies of six identifiedGpdh alleles, although this result ispreliminary because of small sample sizes.However, both the mitochondrial and intron datasuggest a higher genetic diversity in theintergrade zone. Based on our analyses wedefine four management units for eastern andcentral populations of Loggerhead Shrikes.