A novel widespread cryptic species and phylogeographic patterns within several giant clam species (Cardiidae: Tridacna) from the Indo-Pacific Ocean

Giant clams (genus Tridacna) are iconic coral reef animals of the Indian and Pacific Oceans, easily recognizable by their massive shells and vibrantly colored mantle tissue. Most Tridacna species are listed by CITES and the IUCN Redlist, as their populations have been extensively harvested and depleted in many regions. Here, we survey Tridacna crocea and Tridacna maxima from the eastern Indian and western Pacific Oceans for mitochondrial (COI and 16S) and nuclear (ITS) sequence variation and consolidate these data with previous published results using phylogenetic analyses. We find deep intraspecific differentiation within both T. crocea and T. maxima. In T. crocea we describe a previously undocumented phylogeographic division to the east of Cenderawasih Bay (northwest New Guinea), whereas for T. maxima the previously described, distinctive lineage of Cenderawasih Bay can be seen to also typify western Pacific populations. Furthermore, we find an undescribed, monophyletic group that is evolutionarily distinct from named Tridacna species at both mitochondrial and nuclear loci. This cryptic taxon is geographically widespread with a range extent that minimally includes much of the central Indo-Pacific region. Our results reinforce the emerging paradigm that cryptic species are common among marine invertebrates, even for conspicuous and culturally significant taxa. Additionally, our results add to identified locations of genetic differentiation across the central Indo-Pacific and highlight how phylogeographic patterns may differ even between closely related and co-distributed species

Allozyme variation in natural and cultured populations in two tilapia species: Oreochromis niloticus and Tilapia zillii

We investigated the electrophoretic polymorphism at 30 protein loci in 27 wild and cultured populations of two tilapia species, Tilapia zillii and Oreochromis niloticus. Single and joint segregations were analysed at 12 polymorphic loci in full-sib families. All the loci showed single segregation in agreement with the Mendelian expectations, and two nonrandom joint segregations were found. In total, 26 loci were polymorphic and 12 were diagnostic between the two species. A pronounced differentiation was observed between the Ivory Coast and Nilo-Sudanian T. zillii populations (average Nei's standard genetic distance = 0.13). Within the Nilo-Sudanian region, the level of variation observed in O. niloticus and T. zillii was rather low when compared with other freshwater species analysed at similar macrogeographical scales. The same pattern of geographical differentiation was found between the west and east African populations in both species suggesting that this structuring mainly reflected the same palaeo-geographical events. Most of the geographical variation observed in the Nile tilapia populations analysed here was present in the cultured stocks. In contrast to fish-farmed stocks analysed in other countries, those from the Ivory Coast and Niger displayed neither evidence of loss of genetic diversity nor any trace of introgression with other cultured tilapia species, indicating that these stocks have been properly managed

The population genetic structure of a common tropical damselfish on the Great Barrier Reef and eastern Papua New Guinea

Understanding patterns of connectivity in marine species is vital for the management and conservation of marine biodiversity. Here, the population genetic structure of a common and abundant tropical reef damselfish, Pomacentrus amboinensis, is reported. Using nine polymorphic microsatellite loci, the genetic structure at both small (i.e., around Lizard Island, Great Barrier Reef [GBR]) and large (GBR and Papua New Guinea [PNG]) spatial and temporal scales (2–1,600 km; 28 days– 6 years; n = 1,119) was analyzed. Temporal analyses found no evidence of genetic differentiation within or between Lizard Island recruitment pulses (RST = -0.001, P = 0.788), or corresponding established adult populations separated by 6 years of sampling (RST = 0.003, P = 0.116). The spatial analysis revealed that P. amboinensis populations are largely panmictic on the GBR and eastern PNG (RST = 0.001, P = 0.913), the only genetic discontinuity being between Kimbe Bay to the north of PNG and all populations south of PNG (RST = 0.077, P\0.0001). Despite assumed high levels of self-recruitment based on previous tagging studies (15–60%), data presented here indicate that enough recruits are dispersing to impede the evolution of genetic structure over distances as great as 1,600 kms in this species. Data therefore indicate that the temporal genetic stability recorded here is maintained by high levels of gene flow