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

LISA M. DAVIS,^1,2 TRAVIS C. GLENN,^1,2 RUTH M. ELSEY,³ HERBERT C. DESSAUER⁴ and ROGER H. SAWYER¹

¹Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA,
²Savannah River Ecology Laboratory, Drawer E, Aiken SC 29802, USA,
³Louisiana Department of Wildlife and Fisheries, Rockefeller Wildlife Refuge, Grand Chenier, LA 70643, USA,
⁴Department of Biochemistry, Louisiana State University, New Orleans, LA 70119, USA

Abstract
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, F_1,208=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 Amiµ-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.

Keywords: alligator, mating systems, microsatellites, multiple paternity, mutation rate, population genetics

SREL Reprint #2530

Davis, L. M., T. C. Glenn, R. M. Elsey, H. C. Dessauer, and R. H. Sawyer. 2001. Multiple paternity and mating patterns in the American alligator, Alligator mississippiensis. Molecular Ecology 10:1011-1024.

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