The Last Two Remaining Populations of the Critically Endangered Estuarine Pipefish Are Inbred and Not Genetically Distinct

The critically endangered estuarine pipefish, Syngnathus watermeyeri, is one of Africa’s rarest fish species and currently faces a significant risk of extinction. A combination of anthropogenic and natural factors threaten submerged macrophyte beds in the two South African estuaries (Bushmans and Kariega) in which the species’ only two known remaining populations reside. Here, we genotyped 34 pipefish from both populations using genome-wide data to determine whether the two estuaries harbour distinct genetic diversity, such that translocating individuals between them might improve the genetic health of both. Our results show that both populations are highly inbred, and no statistically significant genetic structure was found between them. Moreover, individuals both within and between estuaries were very closely related to each other. These results indicate that the remaining populations of the estuarine pipefish suffer from the adverse genetic effects of small population sizes. Even though recent surveys have estimated population sizes in the order of thousands of individuals, these may fluctuate considerably. Although the translocation of genetically similar individuals between habitats will not increase local genetic diversity, the creation of additional populations across the species’ historical range may be a suitable conservation strategy to prevent further loss of genetic diversity, and to minimise the overall extinction risk posed by environmental stochasticity.

Genetic differentiation between inshore and offshore populations of northern shrimp (Pandalus borealis)

Many marine organisms have a permanent presence both inshore and offshore and spawn in multiple areas, yet their status as separate populations or stocks remain unclear. This is the situation for the northern shrimp (Pandalus borealis) around the Arctic Ocean, which in northern Norway represents an important income for a small-scale coastal fishery and a large-vessel offshore fleet. In Norwegian waters, we uncovered two distinct genetic clusters, viz. a Norwegian coastal and a Barents Sea cluster. Shrimps with a mixed heritage from the Norwegian coastal and the Barents Sea clusters, and genetically different from both, inhabit the fjords at the northernmost coast (Finnmark). Genetic structure between fjords did not display any general trend, and only the Varangerfjord in eastern Finnmark displayed significant genetic structure within the fjord. Shrimps in the Finnmark fjords differed in some degree from shrimps both in the adjacent Barents Sea and along the rest of the coast and should probably be considered a separate management unit.

Genetic differentiation in the genus Characodon: implications for conservation and taxonomy

The subfamily Goodeinae is a group of fishes endemic to the Mexican highlands. Most of the species are restricted to small and isolated streams or springs. Within this subfamily, the genus Characodon is the earliest diverging lineage of which three species have been described: C. lateralis, C. audax, and C. garmani, with the latter, considered extinct. Characodon lateralis and C. audax are classed as endangered, and have been the subject of taxonomic controversy since their description: previous studies have recognized a genetic differentiation in two groups separated by the El Salto waterfall, but morphological analyses contradict these genetic results. We perform a phylogeographic study using the mitochondrial cytb gene and d-loop region to elucidate the evolutionary history of C. lateralis and C. audax. The results with both markers show the presence of two highly differentiated haplogroups; one distributed north and the other distributed south of the waterfall, with genetic distances of 1.7 and 13.1% with cytb and d-loop respectively, and divergence calculated to have occurred 1.41 Mya. Significant genetic structure was found within each haplogroup and suggests the existence of at least four Evolutionary Significant Units (ESUs) within the examined populations. The possible processes identified as contributing to the formation of differentiated genetic groups are isolation, low population size, recurrent bottlenecks, and the strong sexual selection exhibited by the genus.

Strong genetic structure and limited connectivity among populations of Clark's Anemonefish (Amphiprion clarkii) in the centre of marine biodiversity

Populations of anemonefish species often show signs of local isolation due limited dispersal potential and oceanographic conditions. Additionally, anthropogenic pressure, such as overharvesting and coral reef exploitation causes reduced population size, eventually leading to local extinction. The understanding of the genetic population structure, as well as the influence of both historical and current connectivity, is required to design effective marine protected area (MPA) networks. In this study, the genetic structure of Clark's Anemonefish (Amphiprion clarkii) populations of the Indo-Malay Archipelago (IMA) is assessed through mitochondrial control region (mtCR) sequences and nuclear microsatellites. Results provided evidence of a significant genetic structure (mtCR: Phist = 0.42039, Phict = 0.63852; microsatellites: Fst = 0.01449, Fct = 0.05199). Genetic breaks were identified among Western (Padang Karimunjawa), Central (Sulawesi, Borneo, Bali, Komodo, Timor), and Eastern (Biak) IMA populations, which matches with patterns obtained for congeneric and other coral reef taxa. Due to the restricted connectivity among these three regions, it is suggested to consider them as separate management areas in the design of MPA networks.

Metapopulation dynamics of the migratory fish Prochilodus lineatus (Characiformes: Prochilodontidae) in a lotic remnant of the Grande River, Southeastern Brazil

ABSTRACT River impoundments for electricity generation lead to environmental changes which severely affect fish migration and species richness. However, little is known about their effect on the genetic structure and population dynamics downstream from the reservoir. Here, we analyzed a set of ten microsatellite loci of Prochilodus lineatus, an important South American migratory fish. Specimens (n = 150) were sampled from five sites in a remnant lotic system that includes sections of the Grande, Pardo and Mogi Guaçu rivers, southeastern Brazil. The data showed that all microsatellites were polymorphic with the allele number per locus ranging from 5 to 32, and genetic diversity (H e ) varied from 0.74 to 0.80. Indices of genetic differentiation and Bayesian analysis showed a significant genetic structure and three genetic clusters inhabiting this river system. An asymmetric gene flow suggests source-sink metapopulation dynamics from tributaries (genetic source) to the main river (genetic sink). A genetic cluster that was not detected in the upper Mogi and Pardo rivers tributaries may indicate there is a “trapped gene pool” downstream from the Porto Colômbia dam. Thus, here we provide new insights into the genetic structure and population dynamics of a migratory fish species in a highly dammed river basin.

Distribution of genetic diversity reveals colonization patterns and philopatry of the loggerhead sea turtles across geographic scales

Understanding the processes that underlie the current distribution of genetic diversity in endangered species is a goal of modern conservation biology. Specifically, the role of colonization and dispersal events throughout a species’ evolutionary history often remains elusive. The loggerhead sea turtle (Caretta caretta) faces multiple conservation challenges due to its migratory nature and philopatric behaviour. Here, using 4207 mtDNA sequences, we analysed the colonisation patterns and distribution of genetic diversity within a major ocean basin (the Atlantic), a regional rookery (Cabo Verde Archipelago) and a local island (Island of Boa Vista, Cabo Verde). Data analysis using hypothesis-driven population genetic models suggests the colonization of the Atlantic has occurred in two distinct waves, each corresponding to a major mtDNA lineage. We propose the oldest lineage entered the basin via the isthmus of Panama and sequentially established aggregations in Brazil, Cabo Verde and in the area of USA and Mexico. The second lineage entered the Atlantic via the Cape of Good Hope, establishing colonies in the Mediterranean Sea, and from then on, re-colonized the already existing rookeries of the Atlantic. At the Cabo Verde level, we reveal an asymmetric gene flow maintaining links across island-specific nesting groups, despite significant genetic structure. This structure stems from female philopatric behaviours, which could further be detected by weak but significant differentiation amongst beaches separated by only a few kilometres on the island of Boa Vista. Exploring biogeographic processes at diverse geographic scales improves our understanding of the complex evolutionary history of highly migratory philopatric species. Unveiling the past facilitates the design of conservation programmes targeting the right management scale to maintain a species’ evolutionary potential.

Population genetic structure of the great star coral, Montastraea cavernosa, across the Cuban archipelago with comparisons between microsatellite and SNP markers

Coral reef habitats surrounding Cuba include relatively healthy, well-developed shallow and mesophotic (30–150 m) scleractinian communities at the cross-currents of the Tropical Western Atlantic (TWA). However, Cuba’s coral communities are not immune to the declines observed throughout the TWA, and there is limited information available regarding genetic connectivity, diversity, and structure among these populations. This represents an immense gap in our understanding of coral ecology and population dynamics at both local and regional scales. To address this gap, we evaluated the population genetic structure of the coral Montastraea cavernosa across eight reef sites surrounding Cuba. Colonies were genotyped using nine microsatellite markers and > 9,000 single nucleotide polymorphism (SNP) markers generated using the 2bRAD approach to assess fine-scale genetic structure across these sites. Both the microsatellite and SNP analyses identified patterns of genetic differentiation among sample populations. While the microsatellite analyses did not identify significant genetic structure across the seven shallow M. cavernosa sampling sites, the SNP analyses revealed significant pairwise population differentiation, suggesting that differentiation is greater between eastern and western sites. This study provides insight into methodological differences between microsatellite and SNP markers including potential trade-offs between marker-specific biases, sample size, sequencing costs, and the ability to resolve subtle patterns of population genetic structure. Furthermore, this study suggests that locations in western Cuba may play important roles in this species’ regional metapopulation dynamics and therefore may merit incorporation into developing international management efforts in addition to the local management the sites receive.

KERAGAMAN GENETIK KIMA KECIL (Tridacna maxima) DI PULAU KUR, PULAU BIAK, DAN MANADO SERTA IMPLIKASINYA UNTUK KONSERVASI

Kima merupakan jenis kerang yang secara ekologis penting pada ekosistem terumbu karang. Biota laut ini mengalami tekanan antropogenik hampir di sebagian besar wilayah Indonesia. Meskipun status spesies kima ini dilindungi berdasarkan Peraturan Pemerintah (PP) No. 7 tahun 1999, namun aktivitas pengambilan ilegal kima di alam masih terjadi. Hal ini tidak hanya menyebabkan penurunan jumlah jenis dan kelimpahan individu, tetapi dapat mengurangi keragaman genetik jenis kima tersebut. Oleh karena itu perlu dilakukan penelitian keragaman genetik Tridacna maxima berdasarkan marka genetik COI dari Pulau Kur, Pulau Biak dan Manado. Penelitian menggunakan 15 sampel dari Pulau Kur (Penelitian ini), kemudian dibandingkan dengan data genbank (11 sampel dari Biak dan 8 sampel dari Manado). Analisis sekuens DNA mitokondria (mtDNa) T. maxima menghasilkan 432 pasang basa. Terdapat 23 haplotipe dengan jumlah situs bervariasi sebanyak 59 situs. Hasil penelitian menunjukkan bahwa keragaman genetik populasi T. maxima termasuk sangat tinggi, yaitu 0,95. Jarak genetik antar populasi, berkisar antara 0,009 (Kur-Manado) sampai 0,051 (Biak-Manado). Hasil analisis pohon filogenetik menunjukkan dua kluster utama, yaitu kluster Kur, Biak, dan Manado, dan kluster Biak. Hasil analis Fst berpasangan menunjukkan perbedaan struktur genetik yang signifikan pada populasi T. maxima di Kur dengan Biak (Fst = 0,558; p = 0,000) dan Manado dengan Biak (Fst = 0,427; p = 0,012), sedangkan populasi Kur dan Manado tidak menunjukkan perbedaan genetik yang signifikan (Fst = 0,087; p = 0,064). Upaya Konservasi pada populasi T. maxima di Pulau Kur dapat dilakukan melalui penerapan konservasi sumber daya alam dalam bentuk kearifan lokal berupa sasi yang diperkuat dengan pembentukan kawasan konservasi laut daerah (KKLD) di lokasi penelitian. sedangkan untuk populasi Manado dan biak adalah penetapan wilayah konservasi. Selain itu, upaya pengawasan dan penegakan hukum terhadap aktifitas perburuan liar perlu ditingkatkan agar upaya konservasi tersebut dapat berhasil sehingga populasi kima tetap lestari. Giant clams are ecologically important bivalves in coral reefs. These marine organisms have been under anthropogenic pressures in almost all part of Indonesia. Even though this species is protected under Government Regulation (PP) No. 7, 1999, but the illegal harvesting is still happened. This not only caused the declining the number of individual and species, but also could lead to a decrease the genetic diversity of this species. Therefore, it is necessary to conduct research on the genetic diversity of Tridacna maxima based on COI genetic markers from Kur Island, Biak Island and Manado. The study used 15 samples T. maxima from Kur Islan (This study) then compared with genbank data (11 samples from Biak and 8 samples from Manado). Sequence analysis of mitochondrial (mt) DNA T. maxima resulted 432 base pairs, which contained 23 haplotypes with total numbers of 59 polymorphic sites. The results show that genetic diversity of the T. maxima population was very high (0.95). The genetic distance between populations in this study ranged from the lowest (0,009) for Kur vs Manado to the highest (0,043) for Biak vs Manado. The filogenetic tree showed that there were two main clades, i.e. 1) T. maxima calde of Kur, Biak, and Manado and 2) T. maxima clade of Biak. The pairwise method analysis (FST) showed a significant genetic structure in the population of T. maxima in Kur with Biak (Fst = 0.558; p = 0.000) and Manado with Biak (Fst = 0.427; p = 0.012), whereas there was relatively no significant differentiation within population in Kur and Manado (Fst = 0.087; p = 0.064). The conservation effort for T. maxima population in Kur island is prioritized by implementing the local wisdom called Sasi with strengthened by the formation of regional marine conservation area on research sites.

Variations in genetic structure and male genitalia suggest recent lineage diversification in the Neotropical dung beetle complex Canthon cyanellus (Scarabaeidae: Scarabaeinae)

We analysed the genetic divergence and morphology of the aedeagus (i.e. phallobase and parameres) in Canthon cyanellus at different geographical levels. The results from both approaches were compared with the current taxonomic assignment of the C. cyanellus complex, which includes three subspecies. We found a high variation in all the morphological characters of the aedeagus in the populations analysed; the morphometric variation was not geographically structured, either by population or by region. The genealogical analysis indicates a significant genetic structure that does not match either the morphological variation in the male genitalia or the previous subspecific taxonomic classification. Our results suggest that the morphological variation of the aedeagus is seemingly not an isolating reproductive barrier and that the intra- and interpopulation morphological variability of the aedeagus in the C. cyanellus complex does not permit the division into several species. We suggest that other evolutionary forces, such as genetic drift and sexual selection, have influenced the evolution of the male genitalia and the incipient differentiation of this species complex.

First insights into the phylogeography and demographic history of the common hermit crab Pagurus bernhardus (Linnaeus, 1758) (Decapoda: Anomura: Paguridae) across the Eastern Atlantic and North Sea

The common hermit crab Pagurus bernhardus (Linnaeus, 1758) is an abundant and ecologically important benthic crustacean in the northeastern Atlantic Ocean. While this species has been intensively studied in terms of its ecology, physiology, behavior, and larval development, knowledge about its population structure and demographic history is still lacking. We examined, for the first time, the genetic variability of P. bernhardus by analyzing two mitochondrial gene fragments (CO1 and 16S) from more than 150 specimens collected from various locations from the Iberian Peninsula to Norway. Our results provide evidence for a significant genetic structure according to the sampled regions for both genetic markers. Furthermore, a comprehensive demographic history reconstruction, mainly based on neutrality tests and a Bayesian Skyline Plot (CO1), revealed a recent demographic expansion of P. bernhardus that preceded the Last Glacial Maximum. Such pattern of retrieved demographic trend could have been likely a successive process to historical contraction of the species into potential climate refugia within the surveyed geographic spectrum.