Geographic variation in Mexican jays (Aphelocoma ultramarina): local differentiation, polyphyly or hybridization?
Studies of genetic variation within highly variable taxa can provide valuable insight into the factors influencing biological diversification. We examined six microsatellite loci, a nuclear intron and the mitochondrial control region to determine if the Mexican jay subspecies Aphelocoma ultramarina couchii and A. u. potosina have hybridized with western scrub-jays (A. californica). We suspected hybridization because these Mexican Jay populations resemble scrub-jays in several traits. We sampled six Mexican jay (N = 105) and four scrub-jay (N = 78) populations. Suspected hybrid Mexican Jay populations did not share any mitochondrial types or intron alleles with scrub-jays. All microsatellite alleles found in the suspected hybrid Mexican jay populations are also found in the control Mexican jay populations. Genetic distance-based trees from microsatellites supported reciprocal monophyly of Mexican jays and scrub-jays with bootstrap support > 80%. We randomized genotypes among populations to test scenarios consistent with hybridization. In some areas where Mexican jays and scrub-jays occur in sympatry or geographical proximity, randomization tests yield results expected under hybridization (100% support for seven of nine scenarios). However, these populations were not the primary candidates for hybridization based on phenotype. Even if low-level hybridization did occur, hybridization does not appear to be the main reason some Mexican jay populations resemble scrub-jays more than others. The scrub-jay-like traits in these populations may be due to drift, adaptation or plasticity. Alternatively, ancient hybridization, followed by selection for scrub-jay like traits in some Mexican jay populations, might have given rise to the observed variation.
The Institute for Genomic Research, 9712 Medical Center Drive, Rockville, Maryland 20850, USA. nbhagaba@tigr.org
Nirmal K
NK
Bhagabati
Jerram L
JL
Brown
Bonnie S
BS
Bowen
D000818:Animals; D001483:Base Sequence; D001502:Beak / Q000254:growth & development; D001824:Body Constitution; D016000:Cluster Analysis; D017931:DNA Primers; D005787:Gene Frequency; D014644:Genetic Variation; D005843:Geography; D006824:Hybridization, Genetic; D019901:Locus Control Region / Q000235:genetics; D008800:Mexico; D018895:Microsatellite Repeats / Q000235:genetics; D008969:Molecular Sequence Data; D010063:Ovum / Q000502:physiology; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D012919:Social Behavior; D020308:Songbirds / Q000235:genetics*; D013045:Species Specificity; D014828:Vocalization, Animal / Q000502:physiology
D017931:DNA Primers