Allozyme Electrophoretic Methods for Analysing Genetic Variation in Giant Clams (Tridacnidae)

Resource /Energy Economics and Policy,

Allozyme electrophoresis demonstrates that the scleractinian coral Montipora digitata is two species

Allozyme electrophoresis at five loci was used to clarify the species status of two morphs of the scleractinian coral Montipora digitata (Dana, 1846), using specimens collected from three locations off the Queensland coast between October 1991 and April 1993. The two morphs, occurring sympatrically, were distinguished by one fixed gene difference at Locus LT-2 and frequency differences at three other loci, indicating reproductive isolation between them. Populations of both morphs were generally in Hardy-Weinberg equilibrium, suggesting that sexual reproduction does occur. Despite sampling designed to reduce the chance of collecting clonemates, the genetic diversity ratio (GO:GE) indicated that asexual reproduction also occurs. This is in agreement with the known modes of reproduction for this species. There was significant genetic differentiation between populations of one of the morphs of M. digitata. This could have been influenced by greater degrees of asexual reproduction in this morph, selection within sites, or variation in larval survival and recruitment patterns. Relatively low F (st) (differentiation among populations) values found for a broadcast spawning species during this study are in accordance with the hypothesis that brooded planulae are adapted for rapid settlement, whereas planulae produced by broadcast spawners are adapted for widespread dispersal

Evidence of a biogeographic break between populations of a high dispersal starfish: congruent regions within the Indo-West Pacific defined by color morphs, mtDNA, and allozyme data

Both mtDNA variation and allozyme data demonstrate that geographic groupings of different color morphs of the starfish Linckia laevigata are congruent with a genetic discontinuity between the Indian and Pacific Oceans. Populations of L. laevigata sampled from Thailand and South Africa, where an orange color morph predominates, were surveyed using seven polymorphic enzyme loci and restriction fragment analysis of a portion of the mtDNA including the control region. Both allozyme and DNA data demonstrated that these populations were significantly genetically differentiated from each other and to a greater degree from 23 populations throughout the West Pacific Ocean, where a blue color morph is predominant. The genetic structure observed in L. laevigata is consistent with traditional ideas of a biogeographic boundary between the Indian and Pacific Oceans except that populations several hundreds kilometers off the coast of north Western Australia (Indian Ocean) were genetically similar to and had the same color morphs as Pacific populations. It is suggested that gene flow may have continued (possibly at a reduced rate) between these offshore reefs in Western Australia and the West Pacific during Pleistocene falls in sea level, but at the same time gene flow was restricted between these Western Australian populations and those in both Thailand and South Africa, possibly by upwellings. The molecular data in this study suggest that vicariant events have played an important role in shaping the broadscale genetic structure of L. laevigata. Additionally, greater genetic structure was observed among Indian Ocean populations than among Pacific Ocean populations, probably because there are fewer reefs and island archipelagos in the Indian Ocean than in the Pacific, and because present-day surface ocean currents do not facilitate long-distance dispersal

Microsatellite variation in Australian and Indonesian pearl oyster Pinctada maxima populations

Eight microsatellite markers were used to screen over 1700 individual pearl oysters Pinctada maxima from 5 Western Australian (Lacepedes, 80 Mile Beach Shallow, 80 Mile Beach\ud Deep, Port Hedland and Exmouth Gulf), 1 northern Australian (Darwin) and 2 Indonesian (Madura and Sumbawa) populations. There was a strong and highly significant relationship between the amount of genetic divergence between pairs of populations and their degree of geographical separation.\ud Within Australia, there was some indication for genetic differences between Exmouth Gulf and the other Western Australian populations and also between Darwin and the Western Australian populations. The Indonesian populations were significantly different from all Australian populations, suggesting little or no direct recruitment to Western Australia from Indonesian sources. Comparison\ud of 2 year-classes of spat (0+ and 1+) in some Australian populations showed no evidence of differences among Western Australian sites. Comparison of the same recruitment class at 2 different ages (0+ spat in 1998 and 1+ spat in 1999) provided no evidence for selection at the screened, or closely linked, loci. With the possible exception of Exmouth Gulf, Western Australian populations can be\ud considered 1 stock with a large effective population size (no <300 and more likely several 1000s)

Isolation and characterization of eight microsatellite loci from silver-lipped pearl oyster Pinctada maxima

We have developed di- and tetra-nucleotide microsatellite markers for the silver-lipped pearl oyster Pinctada maxima. Screening of approximately 50 000 clones resulted in the identification of 74 microsatellites. Fluorescent PCR was optimized for eight polymorphic loci. In a sample of 1637 individuals, these eight loci possessed between 14 and 68 alleles (average 29.8), with observed and expected heterozygosity ranging from 0.479 to 0.891 and 0.872 to 0.972, respectively

Genetic differentiation among populations of the brooding soft coral Clavularia koellikeri on the Great Barrier Reef

The contribution of sexual and asexual reproduction, the spatial patterns of genetic structure, and the potential gene flow among populations were determined for the soft coral Clavularia koellikeri (Octocorallia: Alcyonacea, Clavulariidae) at ten sites among six reefs from two well-separated regions of the Great Barrier Reef (GBR), Australia. Eight allozyme loci indicated that colonies of C. koellikeri separated ≥3 m were produced sexually. Genetic diversity was lower in the southern (18°S) compared with the northern (10°S) populations, suggesting that reefs closer to the southernmost limit of the distribution of C. koellikeri within the GBR (19°S) may represent a more marginal habitat for this species. High levels of genetic differentiation were significant at all spatial scales (sites within reefs, reefs, and regions) from <4 km up to 1,000 km, indicating that C. koellikeri has restricted dispersal, consistent with having brooded larvae