Campton et al.: Genetic patchiness among Strombus gigas populations 



251 



In the study described here, allozymes were used to 

 examine the genetic structure of queen conch popula- 

 tions in the Florida Keys and Bimini. We collected 

 conch from the same localities in multiple years to com- 

 pare spatial and temporal components of genetic varia- 

 tion. Testing the relative significance of those two com- 

 ponents was a major objective of our study. 



Materials and methods 



Sampled populations 



Queen conch were collected between 1987 and 1990 

 from four localities in the Florida Keys and from 

 Bimini, a linear distance of approximately 350 km 

 (Table 1, Fig. 1). Samples of conch were obtained in 

 multiple years from Ballast Key, Coffins Patch, and 

 Craig Key. Single samples were obtained from Key Bis- 

 cajme and Bimini. All animals were collected by scuba 

 diving or snorkeling. 



The shell length, or major axis, of each conch was 

 measured with calipers to the nearest mm. Based on 

 size distributions, the Coffins Patch population (or ag- 

 gregation) appeared to be a single year-class or cohort 

 that we sampled in three consecutive years (Table 1). 

 All other populations represented mixtures of year- 

 classes with new recruits added each year. 



Tissues 



Conch collected in 1987 (three samples) were processed 

 according to the methods of Mitton et al. (1989): Only 

 the distal tip of the digestive gland, including gonad 



and associated connective tissue, was retained for en- 

 zyme extraction. We were not able to resolve some of 

 the enzymes or presumptive loci reported by Mitton 

 et al. (1989) but were able to resolve some enzymes and 

 loci not examined previously. Consequently, from each 

 of 12 conch collected from Ballast Key in February, 

 1988 (Table 1), we dissected six tissues for further 

 screening of enzymes and loci: (1) foot muscle, (2) 

 proboscis with radula, (3) eyes and eyestalks, (4) 

 crystalline style, (5) mantle tissue, and (6) distal tip of 

 the digestive gland (Little 1965). Thirty-eight enzjmies 



Figure 1 



Localities from which queen conch 

 Strombus gigas were collected. For 

 the study described here, conch were 

 collected from (1) Ballast Key, (2) Cof- 

 fins Patch, (3) Craig Key, (4) Key Bis- 

 cayne, and (5) Bimini. Localities 6-14 

 are from Mitton et al. (1989): (6) Ber- 

 muda, 1 site; (7) Turks and Caicos 

 Islands, 4 sites; (8) St. Kitts, 2 sites; 

 (9) Nevis, 1 site; (10) St. Lucia, 2 sites; 

 (11) Bequia, 1 site; (12) Barbados, 1 

 site; (13) Grenadines, 3 sites; and 

 (14) Belize, 2 samples, 1 each of the 

 normal and melanic forms. 



