Multiple paternity and mating patterns in the American alligator, Alligator mississippiensis.

Eggs were sampled from 22 wild American alligator nests from the Rockefeller Wildlife Refuge in south-west Louisiana, along with the females guarding the nests. Three nests were sampled in 1995 and 19 were sampled in 1997. Females and offspring from all clutches were genotyped using five polymorphic microsatellite loci and the three nests from 1995 were also genotyped using one allozyme locus. Genotypes of the hatchlings were consistent with the guarding females being the mothers of their respective clutches. Multiple paternity was found in seven of the 22 clutches with one being fathered by three males, and the remaining six clutches having genotypes consistent with two males per clutch. Paternal contributions of multiply sired clutches were skewed. Some males sired hatchlings of more than one of the 22 clutches either as one of two sires of a multiple paternity clutch, as the sole sire of two different clutches, or as the sole sire of one clutch and one of two sires of a multiply sired clutch. There was no significant difference between females that had multiple paternity clutches and those that had singly sired clutches with respect to female total length (P = 0.844) and clutch size (P = 0.861). Also, there was no significant correlation between genetic relatedness of nesting females and pairwise nest distances (r2 = 0.003, F1,208 = 0.623, P = 0.431), indicating that females in this sample that nested close to one another were no more related than any two nesting females chosen at random. Eleven mutations were detected among hatchlings at the five loci over the 22 clutches. Most of these mutations (eight of 11) occurred at Ami(mu)-17, the only compound microsatellite locus of the five used in this study, corresponding to a mutation rate of 1.7 x 10-3. Finally, most of the mutations (82%) were homoplasious, i.e., mutating to an allelic state already present in this Louisiana population.

Rapid screening of DNA diversity using dot-blot technology and allele-specific oligonucleotides: maternity of hybrids and unisexual clones of hybrid origin (lizards, Cnemidophorus).

Allele-specific oligonucleotide probes, together with dot-blot methods, can provide rapid and inexpensive screening of DNA types in large samples of organisms. Here we demonstrate their use in: (1) determining types of mitochondrial DNA in hundreds of lizards from a dynamic hybrid zone; (2) discovering intraspecific geographic variation in genes; and (3) determining and verifying the maternal ancestry of unisexual, parthenogenetic lizards in clones of hybrid origin. These methods are broadly applicable in research involving rapid screening of DNAtypes in large samples of specimens for any gene with sequence data from which to design specific probes.

Allozyme evidence for crane systematics and polymorphisms within populations of Sandhill, Sarus, Siberian, and whooping cranes.

Electrophoretic analysis of proteins yielded evidence on the relationships of species of cranes and on genetic diversity within populations of some species. Diversity within the Greater Sandhill crane and a Florida population of the Florida Sandhill crane was similar to that of most other vertebrates, but diversity was low in the Mississippi Sandhill crane, in the Okefenokee population of the Florida Sandhill crane, and within the Siberian and Sarus cranes. Diversity was surprisingly high among whooping cranes, whose number dropped to less than 25 early in this century. Phylogenetic analysis, using both character state and distance algorithms, yielded highly concordant trees for the 15 species. The African crowned cranes (Balearica) were widely divergent from all other cranes. Species of Anthropoides, Bugeranus, and Grus clustered closely but sorted into two lineages: a Whooper Group consisted of the whooping, common, hooded, black-necked, white-naped, and red-crowned cranes of genus Grus; and a Sandhill Group included the Sandhill, Siberian, Sarus, and Brolga cranes of genus Grus, the wattled crane of genus Bugeranus, and the Demoiselle and blue cranes of genus Anthropoides.

alpha-Crystallin A sequences of Alligator mississippiensis and the lizard Tupinambis teguixin: molecular evolution and reptilian phylogeny.

The amino acid sequences of the eye lens protein alpha-crystallin A from many mammalian and avian species, two frog species, and a dogfish have provided detailed information about the molecular evolution of this protein and allowed some useful inferences about phylogenetic relationships among these species. We now have isolated and sequenced the alpha-crystallins of the American alligator and the common tegu lizard. The reptilian alpha A chains appear to have evolved as slowly as those of other vertebrates, i.e., at two to three amino acid replacements per 100 residues in 100 Myr. The lack of charged replacements and the general types and distribution of replacements also are similar to those in other vertebrate alpha A chains. Maximum-parsimony analyses of the total data set of 67 vertebrate alpha A sequences support the monophyletic origin of alligator, tegu, and birds and favor the grouping of crocodilians and birds as surviving sister groups in the subclass Archosauria.

Axial differences in the musculature of uropeltid snakes: the freight-train approach to burrowing.

The shield-tailed snakes (family Uropeltidae) extend and widen the tunnels in which they live by alternately curving and straightening the anterior portion of their vertebral columns within the skin, a burrowing method that proves to be most effective for tunneling amid roots and rocks, as well as for producing tunnels wider than the trunk through unpredictably heterogeneous substrates. The muscles of the anterior portion of the uropeltid trunk are larger and thicker than those of the posterior and are further modified by the inclusion of large amounts of myoglobin, numerous mitochondria, and diverse other ultrastructural and enzymatic specializations, which presumably represent adaptations for sustained work loads. The very much thinner, serially homologous, but unmodified musculature of the posterior trunk occupies only a much smaller fraction of the cross-sectional area. This regional modification increases the effectiveness of the posterior body for storing viscera and developing embryos.

Fingerprint correspondence of hemoglobins and the relationships of sea snakes.

1. Peptide fingerprints of tryptic digests of the globins of sea snake species of Hydrophis, Pelamis, Aipysurus, Laticauda and the terrestrial elapid Naja were compared. 2. Globin divergence, as estimated from peptide fingerprints, paralleled closely transferrin divergence, as measured immunologically. 3. Taxonomic affinities, suggested by the fingerprint data, are concordant with McDowell's taxonomic system for sea snakes with the following exceptions: (a) Laticauda shows a closer affinity to the true sea snakes than to the terrestrial elapid Naja. (b) Sea snakes appear to be more widely divergent from terrestrial elapids than his scheme suggests.

Genic homozygosity in an ancient reptile (Alligator mississippiensis).

Proteins assayed electrophoretically showed variation at only three of 49 presumed genetic loci in alligators from southwestern Louisiana. Average heterozygosity per individual was 0.021+/-0.012; proportion of polymorphic loci was 0.06. Data on the history, structure, and ecology of this alligator population are consistent with natural selection as the primary factor accounting for this low genetic variability. However, neither a historic population bottleneck nor some genetic mechanism limiting variability can be dismissed as a possible factor.

High genetic variability in an ecologically variable vertebrate, Bufo viridis.

Allozymic variation in proteins encoded by 26 loci was analyzed electrophoretically in 517 specimens of green toads from 11 populations from Israel and one population from Vis Island in the Adriatic Sea. Genetic variation in this toad is the highest yet reported in any vertebrate. All three genetic parameters, mean number of alleles per locus (A), mean proportion of loci polymorphic per population (P), and mean number of heterozygous loci per individual (H), are very high (A = 1.65, range 1.38-2.04; P = 0.423, range 0.346-0.615; H = 0.133, range 0.108-0.159). Central and marginal mainland populations are only slightly more variable than desert isolates, but much more variable than the Vis Island population. Genetic similarity is very high between mainland populations (S = 0.951, range 0.93-0.97). Frequencies of two alleles (Icd-lc and Tfa) are correlated with an ecological gradient of increasing aridity. Regulatory enzymes appeared to contribute more to overall polymorphism than non-regulatory enzymes. The genetic variation observed suggests that selection for heterozygosity as an adaptive strategy is operating in the ecologically variable environment in which green toads live.

Variability of polymorphic cellular enzymes in medical students with different serum lipid levels: a preliminary survey.

Groups of male Caucasian medical students who had, relative to their classmates, eitherhigh or low lipid levels were screened for electrophoretic variants of haptoglobin, transferrin, and 10 polymorphic erythrocyte enzymes. Members of both the "high" and "low" lipid groups were found to be polymorphic at 7 genetic loci, 6 of which were enzymatic. Consistently, at most polymorphic loci the high lipid groups had somewhat higher frequencies of nonpredominant phenotypes (patterns other than the phenotype reported to occur most frequently in U.S.A. Caucasian populations). A higher frequency of the less common nonpredominant phenotypes (reported Caucasian population frequency less than 0.200) in the high lipid groups was primarily responsible for the observed variations in the phenotypic distributions. Gene frequency distributions were correspondingly skewed. In 14 comparisons between the high and low lipid groups the least common allele of the 7 polymorphic series had a higher frequency in the high lipid group 9 times and in the low lipid group only once. Collectively, our preliminary observations suggest quantitative and qualitative genetic trends related to serum lipid levels that warrant more extensive investigation.

Genetic variation as a test of natural selection.

Allozymic variation encoded by 26 loci was analyzed electrophoretically in 507 specimens representing 12 populations of green toads, Bufo viridis, in Israel and the Vis Adriatic Island. Genetic variation in Bufo viridis is higher than in any vertebrate yet studied. Mean heterozygosity per locus per individual (H) is 0.133 (range, 0.105 to 0.159). H is higher in central populations as compared with isolates, and varies among four major protein classes, being highest in transferases and hydrolases and lowest in oxidoreductases and nonenzymatic proteins. Differential gene frequencies among polymorphisms was tested as an indicator of natural selection. Significant heterogeneity between loci in their apparent inbreeding coefficients Fe=S-2p/P(1-p) was found for all alleles and for each of the four major classes of proteins tested, which may be taken as evidence of selection. Both uniform and diversifying selection are suggested by the low and high Fe values, respectively. The general pattern of high heterozygosity in Bufo viridis is best explained as an adaptive strategy in heterogeneous environments.