Sympatric populations of white-tailed deer and mule deer (Odocoileus virginianus and Odocoileus hemionus, respectively) on a west Texas ranch share a common mitochondrial DNA restriction map genotype. Phylogenetic analysis indicates that this genotype is more characteristic of 0.virginianus than of 0. hemionus. The genotype of west Texas deer differs from that of 0. virginianus from South Carolina by five mutational events (1.3% sequence divergence), whereas it differs from that of 0. hemionus from California by 17 events (5.5% divergence). We suggest that interspecies hybridization has occurred, primarily between mule deer bucks and whitetailed deer does, with preferential absorption of hybrid offspring into the mule deer gene pool. Introgressive hybridization may be involved in ongoing displacement of mule deer by white-tailed deer in west Texas.Natural hybridization between white-tailed deer (Odocoileus virginianus) and mule deer or black-tailed deer (Odocoileus hemionus) has long been suspected (1, 2). In New Mexico and west Texas, white-tailed deer have expanded their range westward at the expense of mule deer for some 40 years, and it has been suggested that hybridization might contribute to this displacement. Captive-breeding studies indicate that interspecific crosses are possible. Although most such matings are sterile, both reciprocal crosses can produce viable offspring, and at least some of these F1 progeny have been fertile in all backcross combinations (3, 4). This problem is of interest from both practical and theoretical considerations. Deer are among the most economically important wildlife species in the United States (5), and hybridization between species of ungulates or other large mammals appears to be rare in nature (6, 7). We are aware of only one published genetic study of natural hybridization among ungulates, a study of bison subspecies (8). Up to the present, the hypothesis of interspecies hybridization in deer has not been tested by quantitative genetic means.Mitochondrial DNA (mtDNA) has been used extensively in studies of population biology in recent years (9-11). The entire molecule has been sequenced in four vertebrate species, as a result of which the positions and natures of the coding sequences, tRNA genes, and rRNA regions are known. The gene order is identical in the four species sequenced thus far (12-15). Because mtDNA is a separate genetic system, outside the nucleus, and seems to be strictly maternally inherited, it has been used as a probe of interspecies gene flow (16)(17)(18)(19)(20)(21).The two species of the genus Odocoileus are distributed throughout North America. Mule deer (including conspecific black-tailed deer of the Pacific Northwest) are primarily western animals, whereas white-tailed deer are more common in the central and eastern United States and in Central America. The two species are broadly sympatric over much oftheir range (22). They are distinguished morphologically by several criteria, including the form of the antlers and the size of the met...

Thirty allozyme loci and 35 mitochondrial DNA (mtDNA) restriction sites were examined in 24 white-tailed deer and 46 mule deer from a hybrid zone in West Texas. A common mtDNA genotype is shared by all of the mule deer with 67% of the white-tailed deer. At the albumin locus, 13% of the white-tailed deer and 24% of the mule deer are heterozygous, sharing alleles that are otherwise species-specific in allopatric populations; 7% of the mule deer are homozygous for the allele that is characteristic of allopatric white-tailed deer. Gene flow appears to have been bidirectional, with greater genetic introgression into mule deer. The mtDNA data suggest that matings between white-tailed and mule deer have occurred in the past. Despite evidence of genetic introgression, analysis of multilocus genotypes indicates that none of the deer examined is an F1 hybrid. Production of such hybrids appears to be generally uncommon in North American deer; management plans that assume otherwise should be reconsidered.

Summary. The prenatal and postnatal ovaries of the giraffe were studied, using histological and ultrastructural techniques. Corpora lutea found in the ovaries of fetal and immature giraffe were not present after puberty, when a single, much larger CL was found in one of the two ovaries during pregnancy.

White-tailed deer (Odocoileus virginianus) derive the majority of their dietary mineral intake from range forages which may be deficient in one or more essential minerals. We have described the macro and trace mineral concentration of 18 shrub, 26 forb, 7 grass, and 1 cactus species, known to occur in south Texas deer diets, collected from the Chaparral Wildlife Management Area in 1974 and 1975. Within each forage class, there were no seasonal differences in calcium (Ca), sodium (Na), potassium (K), or magnesium (Mg) concentrations. Phosphorus (P) concentrations in browse were higher (PI0 051 durinn the snrinn (0.20%) thnn dur-_~ _~~~~ _ __e__, ______ _ _..-=_____ \_ .__, ",-__-ing other seasons(O.U-0.16%). Forb P concentrations were greatest during the spring and winter periods (0.26 and 0.2970, respectively), and P levels in grasses (0.24-0.14%) decreased as the forage matured and reached senescence. Shrubs contained less P and K (p10.01) than either grasses or forbs; whereas, grasses contained lower concentrations of Ca and Mg (EO.01) than shrubs or forbs. Sodium concentrations did not diier among forage classes. Forbs contained greater (fiO.01) levels of copper (Cu) and zinc (Zn) than erasses or browse-nnd hr~wm c~n!ri~ed 1~9s ire" (Fe! m-I-(%0.01) than forbs or grasses. Manganese concentrations did not differ among forage classes. There were differences in mineral concentrations among species within forage class. Results suggest concentrations of all minerals except P met or exceeded minimum domestic animal requirements. Managers should provide a diversity of plant species and encourage practices that promote forb growth to provide optimum and nutritional benefits for deer.

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