Phylogeography of island canary (Serinus canaria) populations

Island canaries (Serinus canaria) are characterised as a species living exclusively on North Atlantic islands, mainly on the Azores, Madeira and Canary Islands. Although they are very common in their habitats, their behaviour and breeding system has only recently been studied systematically. To advance the understanding of their ecology and to see if the rather isolated archipelagos are already promoting a genetic differentiation, we investigated their phylogeographic relationship as revealed by mtDNA sequences of the cytochrome b gene and investigated whether this measure corresponds to morphological characteristics within the islands. Genetic distances were very low throughout the distribution range of the species. Although the variation of genetic distances within the population of Pico (Azores) was larger than that on Madeira and Canary Islands, the genetic distances between island populations were very low throughout which prevented a clear phylogeographic differentiation. Moreover, morphological measurements did not reveal a consistent pattern to reliably separate the populations, although the measures of beak length and body weight revealed a clear island-specific differentiation. These data lead to the assumption that the colonisation of the Atlantic islands by the canaries occurred very recently, while there is no persisting gene flow between the populations.     

Phylogeography and natural selection in the Tenerife gecko Tarentola delalandii: testing historical and adaptive hypotheses

Combining phylogeographic and matrix correspondence approaches in the analysis of geographical variation provides a fruitful approach to inferring the causes of molecular and morphological evolution within species. Here we present a study on the gecko Tarentola delalandii on the island of Tenerife, Canary Islands, which provides an outstanding model of an exceptionally high degree of phylogeographic differentiation in magnitude and pattern on a small spatial scale. We reconstruct the population history of T. delalandii using phylogeographic information, matrix correspondence tests and estimates of divergence times in conjunction with geological data. It appears that populations differentiated on three precursor islands and secondary contact followed the junction of these islands. The cytochrome b sequence appears to be evolving at least at approximately 1% per million years in this species. Matrix correspondence tests indicate that morphological character systems may reflect ecological selection regimes (colour pattern), history (body dimensions) or both (scalation). The results imply that natural selection can override a historical legacy, but also underline the potential relevance of molecular phylogenetic data for the interpretation of geographical variation in morphology.     

Phylogeography of skinks (Chalcides) in the Canary Islands inferred from mitochondrial DNA sequences

Mitochondrial DNA (mtDNA) evolution was investigated in skinks of the genus Chalcides found in the Canary Islands ( Ch. sexlineatus, Ch. viridanus and Ch. simonyi ), together with some North African congenerics ( Ch. polylepis and Ch. mionecton ). Several sites were included within islands to cover areas of known within-island geographical variation in morphology. Skinks from the islands of El Hierro and La Gomera appear to be sister taxa. The relationships between this clade and the Tenerife and Gran Canarian skinks were not fully resolved, although the best working hypothesis indicated monophyly with the former, with the latter forming a closely related outgroup. Ch. simonyi from Fuerteventura was more distantly related to the Western Canary Island skinks and did not show close relationships with the North African species Ch. mionecton and Ch . polylepis . Possible colonization sequences for the four most Western Canary Islands were considered. El Hierro appears to have been colonized relatively recently from La Gomera, commensurate with the recent origin of this island, while dispersal between La Gomera and Tenerife and between Gran Canaria and Tenerife or La Gomera appears to have taken place considerably earlier. Substantial within-island haplotype divergence was found in Gran Canaria and Tenerife. This may be a result of recent periods of intense volcanic activity found within these two islands. Lower levels of within-island differentiation are found in La Gomera and El Hierro and may be explained by lower levels of volcanic activity during recent geological history and a more recent colonization, respectively.     

The odd couple: contrasting phylogeographic patterns in two sympatric sibling species of woodlouse‐hunter spiders in the Canary Islands

Comparative phylogeography seeks for commonalities in the spatial demographic history of sympatric organisms to characterize the mechanisms that shaped such patterns. The unveiling of incongruent phylogeographic patterns in co‐occurring species, on the other hand, may hint to overlooked differences in their life histories or microhabitat preferences. The woodlouse‐hunter spiders of the genus Dysdera have undergone a major diversification on the Canary Islands. The species pair Dysdera alegranzaensis and Dysdera nesiotes are endemic to the island of Lanzarote and nearby islets, where they co‐occur at most of their known localities. The two species stand in sharp contrast to other sympatric endemic Dysdera in showing no evidence of somatic (non‐genitalic) differentiation. Phylogenetic and population genetic analyses of mitochondrial cox1 sequences from an exhaustive sample of D. alegranzaensis and D. nesiotes specimens, and additional mitochondrial (16S, L1, nad1) and nuclear genes (28S, H3) were analysed to reveal their phylogeographic patterns and clarify their phylogenetic relationships. Relaxed molecular clock models using five calibration points were further used to estimate divergence times between species and populations. Striking differences in phylogeography and population structure between the two species were observed. Dysdera nesiotes displayed a metapopulation‐like structure, while D. alegranzaensis was characterized by a weaker geographical structure but greater genetic divergences among its main haplotype lineages, suggesting more complex population dynamics. Our study confirms that co‐distributed sibling species may exhibit contrasting phylogeographic patterns in the absence of somatic differentiation. Further ecological studies, however, will be necessary to clarify whether the contrasting phylogeographies may hint at an overlooked niche partitioning between the two species. In addition, further comparisons with available phylogeographic data of other eastern Canarian Dysdera endemics confirm the key role of lava flows in structuring local populations in oceanic islands and identify localities that acted as refugia during volcanic eruptions.     

DNA barcoding of Neotropical bats: species identification and discovery within Guyana

Sequence diversity in the cytochrome c oxidase subunit 1 gene has been shown to be an effective tool for species identification and discovery in various groups of animals, but has not been extensively tested in mammals. We address this gap by examining the performance of DNA barcodes in the discrimination of 87 species of bats from Guyana. Eighty‐one of these species showed both low intraspecific variation (mean = 0.60%), and clear sequence divergence from their congeners (mean = 7.80%), while the other six showed deeply divergent intraspecific lineages suggesting that they represent species complexes. Although further work is needed to examine patterns of sequence diversity at a broader geographical scale, the present study validates the effectiveness of barcoding for the identification of regional bat assemblages, even highly diverse tropical faunas.     

Diversification of the forest beetle genus Tarphius on the Canary Islands, and the evolutionary origins of island endemics

The flightless beetle genus Tarphius Erichson (Coleoptera: Colydiidae) is a distinctive element of the beetle fauna of the Canary Islands with 29 species distributed across the five western islands. The majority of Tarphius species are rare and intimately associated with the monteverde forest and only two species occur on more than one island. In this study we investigate the phylogeography of the Canary Island Tarphius, and their relationship to Tarphius from the more northerly archipelagos of Madeira and the Azores using maximum parsimony and Bayesian inference analysis of mitochondrial cytochrome oxidase I and II sequence data. We use geological datings for the Canary Islands, Azores, and Madeira to calibrate specific nodes of the tree for the estimation of divergence times using a penalized likelihood method. Data suggest that the Canary Island species assemblage is of some antiquity, however, much of this species diversity is relatively recent in origin. The phylogenetic relationships of species inhabiting the younger islands of El Hierro and La Palma indicate that colonization events between islands have probably been a significant factor in the evolutionary history of the Canary Island species assemblage. A comparison of molecular phylogenetic studies of arthropods on the Canary Islands suggests that, in the evolution of the arthropod species community of an island, the origin of endemic species is initially the result of colonizing lineages differentiating from their source populations. However, as an island matures a greater proportion of endemic species originate from intra-island speciation.     

Portuguese migration to the Canary Islands: an analysis based on surnames

As a part of a wider analysis of population and genetic exchange between Spain and Portugal, the long-term pattern of Portuguese immigration to the Canary Islands was studied by means of the frequency of Portuguese surnames. A database of 1,995,833 individuals was obtained from the Spanish National Statistics Institute (2006). Among the 826 most frequent surnames to appear, 79 surnames of Portuguese origin were selected. The distribution of these surnames by municipalities and islands, the Fisher index of diversity, and the Lasker inter-population relationship coefficients R(ij) were considered. These coefficients were inter-correlated and correlated with other variables that could have influenced the distribution of surnames. From the observed distribution of the frequency of surnames, a non-random migration pattern conditioned by economic factors was found. The greatest diversity of surnames existed in cane cultivating areas after the first arrival of Portuguese immigrants. A later dispersion of surnames among islands was correlated with the inter-island geographic distances. In some islands the arrival of new immigrants continued due to their strategic location within the Canary archipelago. The Canary Islands reveal a high frequency and diversity of Portuguese surnames. The results also prove a heterogeneous distribution of these surnames throughout the archipelago. In contrast to the Portuguese archipelagos, some Canary localities have received immigrants continuously because of their economic importance in sugar cane cultivation and strategic geographic location on the maritime routes to Africa and America.     

Genetic diversity and population structure of the commercially harvested sea urchin Paracentrotus lividus (Echinodermata, Echinoidea)

The population structure of the edible Atlanto-Mediterranean sea urchin Paracentrotus lividus is described by analysing sequence variation in a fragment of the mitochondrial gene cytochrome c oxidase subunit I in 127 individuals from 12 localities across south-west Europe. The study revealed high levels of genetic diversity but low levels of genetic structure, suggesting a large degree of gene flow between populations and panmixis within each, the Mediterranean and Atlantic basins. However, we found significant genetic differentiation between the two basins probably due to restricted gene flow across the geographical boundary imposed by the area of the Strait of Gibraltar. Populations of P. lividus appeared to have experienced a recent demographic expansion in the late Pleistocene. We provide new evidence on the population structure of this commercial species, predicting a healthy stock of this sea urchin on the Mediterranean and Atlantic coasts.     

Explanations for bird species range size: ecological correlates and phylogenetic effects in the Canary Islands

Aim To explore the determinants of island occupancy of 48 terrestrial bird species in an oceanic archipelago, accounting for ecological components while controlling for phylogenetic effects. Location The seven main islands of the Canary archipelago. Methods We obtained field data on population density, habitat breadth and landscape distribution in Tenerife, Fuerteventura and La Palma, aiming to sample all available habitats and the gradient of altitudes. In total, 1715 line transects of 0.5 km were carried out during the breeding season. We also reviewed the literature for data on occupancy, the distance between the Canary Islands and the nearest distribution border on the mainland, body size and endemicity of the 48 terrestrial bird species studied. Phylogenetic eigenvector regression was used to quantify (and to control for) the amount of phylogenetic signal. Results The two measurements of occupancy (number of occupied islands or 10 × 10 km UTM squares) were tightly correlated and produced very similar results. The occupancy of the terrestrial birds of the Canary Islands during the breeding season had a very low phylogenetic effect. Species with broader habitat breadth, stronger preferences for urban environments, smaller body size, and a lower degree of endemicity had a broader geographical distribution in the archipelago, occupying a larger number of islands and 10 × 10 UTM squares. Main conclusions The habitat‐generalist species with a tolerance for novel urban environments tend to be present on more islands and to occupy a greater area, whereas large‐sized species that are genetically differentiated within the islands are less widespread. Therefore, some properties of the ranges of these species are explicable from basic biological features. A positive relationship of range size with local abundance, previously shown in continental studies, was not found, probably because it relies on free dispersal on continuous landmasses, which may not be applicable on oceanic islands.     

MtDNA phylogeography and recent intra-island diversification among Canary Island Calathus beetles.

The genus Calathus Bonelli comprises 24 species on the Canary Islands. Sequences of 927 and 687 bp of the mitochondrial cytochrome oxidase I and II genes, respectively, as well as the intervening tRNA leu gene in 21 of the 24 species, have identified three genetically divergent and unequivocally monophyletic groupings. A phylogeographic analysis is presented for the major monophyletic group comprising all the species of Gran Canaria, La Gomera, and El Hierro, and two Tenerifean species. A distance-based phylogenetic analysis and maximum parsimony analysis have clearly shown that this clade is composed of four distinct lineages. DNA sequence data suggest a recent origin for this clade and that lineages have not evolved at the same rate. Compared with diversification patterns observed in other Coleoptera on the Canary Islands, diversification has been recent relative to the time of colonization within the islands of Gran Canaria and La Gomera. Calathus diversification on La Gomera has been greater than on Gran Canaria. The influences of geological and ecological history are discussed in relation to Calathus diversification.     

Phylogenetic relationships among the Canary Island Steganacaridae (Acari, Oribatida) inferred from mitochondrial DNA sequence data

The mite genus Steganacarus is represented in the Canary Islands by three endemic species, one recently discovered species, and several morphotypes of uncertain taxonomic position. We used a fragment of the mitochondrial cytochrome oxidase I gene to reconstruct the phylogenetic relationships among representatives of the different taxa from the three central islands of the archipelago, Tenerife, La Gomera and Gran Canaria. Sequence data were analysed by both maximum parsimony and maximum likelihood methods. The inferred phylogenetic relationships do not correlate well with current morphological taxonomy but reveal four deeply divergent and geographically coherent lineages, one each on Gran Canaria and La Gomera and two on Tenerife. No pattern of molecular differentiation was observed among different morphotypes. Possible explanations for this incongruence are suggested in relation to the ecology and biogeography of the group. A recently discovered Steganacarus species from La Gomera, morphologically quite distinct from the other Canarian Steganacarus, is clearly identified as a taxon distantly related to all the other Canarian samples.     

Interpreting colonization of the Calathus (Coleoptera: Carabidae) on the Canary Islands and Madeira through the application of the parametric bootstrap

The Canary Islands have proven to be an interesting archipelago for the phylogeographic study of colonization and diversification with a number of recent studies reporting evolutionary patterns and processes across a diversity of floral and faunal groups. The Canary Islands differ from the Hawaiian and Galapagos Islands by their close proximity to a continental land mass, being 110 km from the northwestern coast of Africa. This close proximity to a continent obviously increases the potential for colonization, and it can be expected that at the level of the genus some groups will be the result of more than one colonization. In this study we investigate the phylogeography of a group of carabid beetles from the genus Calathus on the Canary Islands and Madeira, located 450 km to the north of the Canaries and 650 km from the continent. The Calathus are well represented on these islands with a total of 29 species, and on the continent there are many more. Mitochondrial cytochrome oxidase I and II sequence data has been used to identify the phylogenetic relationships among the island species and a selection of continental species. Specific hypotheses of monophyly for the island fauna are tested with parametric bootstrap analysis. Data suggest that the Canary Islands have been colonized three times and Madeira twice. Four of these colonizations are of continental origin, but it is possible that one Madeiran clade may be monophyletic with a Canarian clade. The Calathus faunas of Tenerife and Madeira are recent in origin, similar to patterns previously reported for La Gomera, El Hierro, and Gran Canaria.     

Biogeographical and evolutionary patterns in the Macaronesian shield-backed katydid genus Calliphona Krauss, 1892 (Orthoptera: Tettigoniidae) and allies as inferred from phylogenetic analyses of multiple mitochondrial genes

Abstract.  We investigated the phylogenetic patterns, evolutionary processes, and their taxonomic implications, of two closely related shield-backed katydid genera endemic to the Macaronesian archipelagos: the monotypic Psalmatophanes Chopard, 1938 endemic to Madeira and Calliphona Krauss, 1892, which includes three species restricted to the Canary Islands. Two main hypotheses have been proposed to explain the origin and colonization pathways of these two genera: a single origin with subsequent sequential colonization of the islands, or three independent colonization waves from continental Africa. We used DNA sequence information from the mitochondrial genes cox1, tRNAleucine, rrnL and nad1 to infer phylogenetic relationships among Psalmatophanes and Calliphona species. Our results provide support for the independent colonization of Madeira and the Canary Islands, and suggest that Psalmatophanes is actually more closely related to the continental genus Tettigonia than to the Canarian representatives. Deep genetic divergence among Canarian species provides further support for the assignment of the Canarian species into two subgenera. Tree topology along with Bayesian-based estimates of lineage age suggest a pattern of colonization from Tenerife to La Palma, and from Tenerife to Gran Canaria with subsequent dispersal to La Gomera. We report the first collection of a Calliphona specimen in the island of El Hierro, which molecular data suggest is a recent immigrant from La Gomera. We hypothesize that the patterns of distribution and genetic divergence exhibited by Calliphona in the Canary Islands are compatible with a taxon cycle process. Our results have further implications for the higher level phylogeny of the subfamily Tettigoniinae and suggest that some of the tribes as currently delimited may not correspond to natural groups.     

Disentangling the complex evolutionary history of the Western Palearctic blue tits (Cyanistes spp.) – phylogenomic analyses suggest radiation by multiple colonization events and subsequent isolation

Isolated islands and their often unique biota continue to play key roles for understanding the importance of drift, genetic variation and adaptation in the process of population differentiation and speciation. One island system that has inspired and intrigued evolutionary biologists is the blue tit complex (Cyanistes spp.) in Europe and Africa, in particular the complex evolutionary history of the multiple genetically distinct taxa of the Canary Islands. Understanding Afrocanarian colonization events is of particular importance because of recent unconventional suggestions that these island populations acted as source of the widespread population in mainland Africa. We investigated the relationship between mainland and island blue tits using a combination of Sanger sequencing at a population level (20 loci; 12 500 nucleotides) and next‐generation sequencing of single population representatives (>3 200 000 nucleotides), analysed in coalescence and phylogenetic frameworks. We found (i) that Afrocanarian blue tits are monophyletic and represent four major clades, (ii) that the blue tit complex has a continental origin and that the Canary Islands were colonized three times, (iii) that all island populations have low genetic variation, indicating low long‐term effective population sizes and (iv) that populations on La Palma and in Libya represent relicts of an ancestral North African population. Further, demographic reconstructions revealed (v) that the Canary Islands, conforming to traditional views, hold sink populations, which have not served as source for back colonization of the African mainland. Our study demonstrates the importance of complete taxon sampling and an extensive multimarker study design to obtain robust phylogeographical inferences.     

Origin and diversification of Hibiscus glaber, species endemic to the oceanic Bonin Islands, revealed by chloroplast DNA polymorphism

Abstract Two woody Hibiscus species co-occur in the Bonin Islands of the northwestern Pacific Ocean: Hibiscus glaber Matsum. is endemic to the islands, and its putative ancestral species, Hibiscus tiliaceus L., is widely distributed in coastal areas of the tropics and subtropics. To infer isolating mechanisms that led to speciation of H. glaber and the processes that resulted in co-occurrence of the two closely related species on the Bonin Islands, we conducted molecular phylogenetic analyses on chloroplast DNA (cpDNA) sequences. Materials collected from a wide area of the Pacific and Indian Oceans were used, and two closely related species, Hibiscus hamabo Siebold Zucc. and Hibiscus macrophyllus Roxb., were also included in the analyses. The constructed tree suggested that H. glaber has been derived from H. tiliaceus, and that most of the modern Bonin populations of H. tiliaceus did not share most recent ancestry with H. glaber. Geographic isolation appears to be the most important mechanism in the speciation of H. glaber. The co-occurrence of the two species can be attributed to multiple migrations of different lineages into the islands. While a wide and overlapping geographical distribution of haplotypes was found in H. tiliaceus, localized geographical distribution of haplotypes was detected in H. glaber. It is hypothesized that a shift to inland habitats may have affected the mode of seed dispersal from ocean currents to gravity and hence resulted in geographical structuring of H. glaber haplotypes.     

Complex population genetic structure in the endemic Canary Island pine revealed using chloroplast microsatellite markers

The Canary archipelago, located on the northwestern Atlantic coast of Africa, is comprised of seven islands aligned from east to west, plus seven minor islets. All the islands were formed by volcanic eruptions and their geological history is well documented providing a historical framework to study colonization events. The Canary Island pine (Pinus canariensis C. Sm.), nowadays restricted to the westernmost Canary Islands (Gran Canaria, Tenerife, La Gomera, La Palma and El Hierro), is considered an old (Lower Cretaceous) relic from an ancient Mediterranean evolutionary centre. Twenty seven chloroplast haplotypes were found in Canary Island pine but only one of them was common to all populations. The distribution of haplotypic variation in P. canariensis suggested the colonization of western Canary Islands from a single continental source located close to the Mediterranean Basin. Present-day populations of Canary Island pine retain levels of genetic diversity equivalent to those found in Mediterranean continental pine species, Pinus pinaster and Pinus halepensis. A hierarchical analysis of variance (AMOVA) showed high differentiation among populations within islands (approximately 19%) but no differentiation among islands. Simple differentiation models such as isolation by distance or stepping-stone colonization from older to younger islands were rejected based on product-moment correlations between pairwise genetic distances and both geographic distances and population-age divergences. However, the distribution of cpSSR diversity within the islands of Tenerife and Gran Canaria pointed towards the importance of the role played by regional Pliocene and Quaternary volcanic activity and long-distance gene flow in shaping the population genetic structure of the Canary Island pine. Therefore, conservation strategies at the population level are strongly recommended for this species.Communicated by D.B. NealeA. Gómez and S.C. González-Martínez as joint authors     

Population history,gene flow,and bottlenecks in island populations of a secondary seed disperser,the southern grey shrike (Lanius meridionalis koenigi)

Studying the population history and demography of organisms with important ecological roles can aid understanding of evolutionary processes at the community level and inform conservation. We screened genetic variation (mtDNA and microsatellite) across the populations of the southern grey shrike (Lanius meridionalis koenigi) in the Canary Islands, where it is an endemic subspecies and an important secondary seed disperser. We show that the Canarian subspecies is polyphyletic with L. meridionalis elegans from North Africa and that shrikes have colonized the Canary Islands from North Africa multiple times. Substantial differences in genetic diversity exist across islands, which are most likely the product of a combination of historical colonization events and recent bottlenecks. The Eastern Canary Islands had the highest overall levels of genetic diversity and have probably been most recently and/or frequently colonized from Africa. Recent or ongoing bottlenecks were detected in three of the islands and are consistent with anecdotal evidence of population declines due to human disturbance. These findings are troubling given the shrike's key ecological role in the Canary Islands, and further research is needed to understand the community‐level consequences of declines in shrike populations. Finally, we found moderate genetic differentiation among populations, which largely reflected the shrike's bottleneck history; however, a significant pattern of isolation‐by‐distance indicated that some gene flow occurs between islands. This study is a useful first step toward understanding how secondary seed dispersal operates over broad spatial scales.     

Amphi-Atlantic distribution of the Mancocumatinae (Cumacea: Bodotriidae), with description of a new genus dwelling in marine lava caves of Tenerife (Canary Islands)

A new cumacean genus and species, Speleocuma guanche gen et sp. nov. , belonging to the subfamily Mancocumatinae Watling 1977 , is described from marine lava caves of Tenerife, Canary Islands. This genus differs from others in the subfamily in having two pairs of pleopods in males and exopods on first to third pereopods, but not on fourth pereopod, in both sexes. Correlation between phylogenetic relationships of the new genus and the geological history of the Canarian archipelago points to a probable origin of this endemism: the subfamily Mancocumatinae show a disjunct distribution on both sides of the Atlantic Ocean, a pattern which has been associated with fauna of Tethyan origin. It is suggested that present-day genera of the subfamily evolved from a common shallow water ancestor living in the late Mesozoic ( c . 120 Myr BP), when the opening of the Atlantic Ocean had begun. It survived in shallow waters off the west African coast before the emergence of the Canary Islands from the sea floor. Later on, between the late Cretaceous and the Mio-Pliocene, it was able to colonize crevicular habitats of the eastern Canary Islands through continental or land bridges. Finally, their numbers increased to occupy more recent biotops like flooded lava tube caves as well as westward islands such as Tenerife. © 2002 The Linnean Society of London. Zoological Journal of the Linnean Society , 2002, 134 , 453–461.     

Living on the edge: demographic and phylogeographical patterns in the woodlouse-hunter spider Dysdera lancerotensis Simon, 1907 on the eastern volcanic ridge of the Canary Islands

The Eastern Canary Islands are the emerged tips of a continuous volcanic ridge running parallel to the northeastern African coast, originated by episodic volcanic eruptions that can be traced back to the Miocene and that, following a major period of quiescence and erosion, continued from the Pliocene to the present day. The islands have been periodically connected by eustatic sea-level changes resulting from Pleistocene glacial cycles. The ground-dwelling spider Dysdera lancerotensis Simon, 1907 occurs along the entire ridge, except on recent barren lavas and sand dunes, and is therefore an ideal model for studying the effect of episodic geological processes on terrestrial organisms. Nested clade and population genetic analyses using 39 haplotypes from 605 base pairs of mitochondrial DNA cytochrome c oxidase I sequence data, along with phylogenetic analyses including two additional mitochondrial genes, uncover complex phylogeographical and demographic patterns. Our results indicate that D. lancerotensis colonized the ridge from north to south, in contrast to what had been expected given the SSW-NNE trend of volcanism and to what had been reported for other terrestrial arthropods. The occurrence of several episodes of extinction, recolonization and expansion are hypothesized for this species, and areas that act as refugia during volcanic cycles are identified. Relaxed molecular clock methods reveal divergence times between main haplotype lineages that suggest an older origin of the northern islets than anticipated based on geological evidence. This study supports the key role of volcanism in shaping the distribution of terrestrial organisms on oceanic islands and generates phylogeographical predictions that warrant further research into other terrestrial endemisms of this fascinating region.     

Historical demography and genetic differentiation of the giant freshwater prawn Macrobrachium rosenbergii in Bangladesh based on mitochondrial and ddRAD sequence variation

Macrobrachium rosenbergii, the giant freshwater prawn, is an important source of high quality protein and occurs naturally in rivers as well as commercial farms in South and South‐East Asia, including Bangladesh. This study investigated the genetic variation and population structure of M. rosenbergii sampled from four rivers in Bangladesh (sample size ranged from 19 to 20), assessing sequence variation, both in the mitochondrial cytochrome oxidase subunit 1 (CO1) gene and in 106 single nucleotide polymorphisms (SNPs) sampled randomly from the genome with double digest RAD sequencing (ddRADseq). The mitochondrial variation presented a shallow genealogy with high haplotype diversity (h = 0.95), reflecting an expansion in population size for the last ~82 kyr. Based on the CO1 variation the current effective population size (N_e) was 9.7 × 10⁶ (CI: 1.33 × 10⁶ – 35.84 × 10⁶) individuals. A significant population differentiation was observed with the mitochondrial CO1 sequence variation and based on the ddRADseq variation, which could be traced to the divergence of the population in the Naf River in the South‐East border with Myanmar from the other populations. A differentiation in mtDNA haplotype frequencies was also observed between the Biskhali River and the Karnaphuli Rivers in eastern Bangladesh. This study demonstrated the use of high‐throughput genotyping based on the ddRADseq method to reveal population structure at a small geographical scale for an important freshwater prawn. The information from this study can be utilized for management and conservation of this species in Bangladesh.