The influence of sea currents, past disruption of gene flow and species biology on the phylogeographical structure of coastal flowering plants

Aim We investigate the geographical genetic structure of two coastal plant species, Cakile maritima Scop. (Brassicaceae) and Eryngium maritimum L. (Apiaceae), through three sea straits and along one continuous stretch of coast using amplified fragment length polymorphisms (AFLPs). The two species have a similar ecology in that they grow in sandy habitats, but differ in life‐form (annual vs. perennial) and dispersability of seeds by sea water as inferred from floating experiments. The sea straits differ in their geological history and their modern current systems. The primary goal of our study was to test the hypothesis that sea straits have an influence on the geographical patterns of genetic variation at the population level. Location The areas around the Strait of Gibraltar, the Dardanelles, the Bosporus and the Atlantic coast of western France. Methods For both species we investigated AFLP variation in several populations from each area. Bayesian clustering and diversity and differentiation measures were used to analyse the genetic data. Results In most areas the spatial genetic structure was similar between the two species. They share the presence of distinct genetic gaps along the coast through the Strait of Gibraltar and the Bosporus, and these genetic gaps coincide with the straits. Both species show genetic continuity along the coast of western France. A distinct genetic gap was found through the Dardanelles for C. maritima but not for E. maritimum. Main conclusions The study shows that sea straits have an influence on the geographical patterns of genetic variation. Sea currents are inferred to cause the genetic gap through the Strait of Gibraltar. In the Bosporus and, for C. maritima, through the Dardanelles, the genetic gaps found are explained by the past closure of these two straits as well as by present‐day factors. Simulations indicate that the lower differentiation of C. maritima through the Dardanelles than through the Bosporus cannot be explained by the difference in geological history of these two straits. The difference in seed dispersability between the two species is argued to be responsible for the observation that differentiation among genetic clusters is higher in E. maritimum than in C. maritima where a direct comparison is possible.     

Phylogeographical lineages in brown trout (Salmo trutta): investigating microgeographical differentiation between native populations from Northern Spain

SUMMARY 1. The large microgeographical differentiation revealed by allozyme studies in brown trout ( Salmo trutta) populations is one of the most striking features of this species. Additionally, allozymes showed great genetic differences between Atlantic and Mediterranean populations on a macrogeographical scale.
2. This study was carried out in order to assess whether the great differences observed between Atlantic and Mediterranean populations persisted where the two are geographically close (the 'microgeographical scale'). Sixteen populations of brown trout, S. trutta , were screened for genetic variation at 25 allozyme loci. The sampling sites, which occupied a relatively small geographical area, were distributed across Cantabrian (Atlantic) and Mediterranean drainages in Northern Spain.
3. The neighbour-joining tree, inferred from Nei's genetic distance, showed that brown trout populations clustered into two different groups. These groups corresponded to the Cantabrian and the Mediterranean groups of populations, although no clear geographical pattern emerged within each of the groups. This geographical pattern is basically caused by significant differences in the frequency distribution of the CK-A1 * locus, with a higher frequency of * 115 in Cantabrian samples (0.586 ± 0.091) while allele * 100 was more frequent in Mediterranean samples (0.931 ± 0.038). In addition, this study revealed alleles exclusive to the Mediterranean and Cantabrian populations, agreeing with previous findings.
4. Genetic differentiation between Cantabrian and Mediterranean regions (14.19%) was similar to that estimated in Spain at a larger scale (13%), showing that most of the differences between the regions can be observed even in a small geographical area.     

Geographic distribution and diversity of mitochondrial DNA haplotypes in South American sea lions (Otaria flavescens) and fur seals (Arctocephalus australis)

Genetic diversity and population structure of two species of South American pinnipeds, Otaria flavescens and Arctocephalus australis, from colonies located along the south-eastern coast of South America, were analysed using mitochondrial DNA haplotypes and compared with two populations of these species from the Pacific coast. A 445 base-pair segment, that included the tRNA-Glu gene (31 bp) and the adjacent cytochrome b gene (414 bp), was amplified using the polymerase chain reaction and sequenced directly. O. flavescens and A. australis showed six and seven haplotypes with 12 and 20 polymorphic sites, respectively. In the Atlantic Ocean there was an individual of A. australis that showed an haplotype that was highly divergent from the others. If this haplotype is excluded, the pattern of haplotype differentiation obtained for both species indicated a possible bottleneck that would have occurred 110,000 years ago, which also affected other pinnipeds. Colonies of the Atlantic and the Pacific did not share haplotypes. This result, based on a limited number of samples for the comparisons between oceans, suggests that populations from both oceans correspond to different evolutionarily significant units. O. flavescens on the Atlantic coast shows two clusters of breeding colonies in Uruguay and Patagonia, separated by a thousand kilometres. Colonies within clusters did not show significant differences in haplotype frequencies, but the difference between the clusters was significant, suggesting that they correspond to different conservation stocks.     

Population genetic structure of Tomicus piniperda L. (Curculionidae: Scolytinae) on different pine species and validation of T. destruens (Woll.)

Genetic diversity and population structure of Tomicus piniperda was assessed using mitochondrial sequences on 16 populations sampled on 6 pine species in France. Amplifications of Internal transcribed space 1 (ITS1) were also performed. Our goals were to determine the taxonomic status of the Mediterranean ecotype T. piniperda destruens, and to test for host plant or geographical isolation effect on population genetic structure. We showed that T. piniperda clusters in two mtDNA haplotypic groups. Clade A corresponds to insects sampled in continental France on Pinus sylvestris, P. pinaster and P. uncinata, whereas clade B gathers the individuals sampled in Corsica on P. pinaster and P. radiata and in continental France on P. pinea and P. halepensis. Insects belonging to clade A and clade B also consistently differ in the length of ITS1. Individuals belonging to both clades were found once in sympatry on P. pinaster. Genetic distances between clades are similar to those measured between distinct species of Tomicus. We concluded that clade B actually corresponds to the destruens ecotype and forms a good species, T. destruens. Analyses of molecular variance ( amova ) were conducted separately on T. destruens and T. piniperda to test for an effect of either geographical isolation or host species. Interestingly, the effect of host plant was significant for T. piniperda only, while the effect of geographical isolation was not. Pine species therefore seems to act as a significant barrier to gene flow, even if host race formation is not observed. These results still need to be confirmed by nuclear markers.     

Allozyme differentiation within and between red drum (Sciaenops ocellatus) from the Gulf of Mexico and Atlantic Ocean

Nine polymorphic nuclear-gene (allozyme) loci were surveyed among 491 red drum ( Sciaenops ocellatus ) sampled in 1988 and 1989 from nearshore localities in the northern Gulf of Mexico (Gulf) and the Atlantic coast of the southeastern United States (Atlantic). Data were combined with those from a previous study to generate a data set of 762 individuals representing 11 sample localities in the Gulf and 175 individuals representing five sample localities in the Atlantic. The combined data set included individuals from the 1986 and 1987 year classes and permitted rigorous testing of both temporal and spatial genetic heterogeneity. Average heterozygosity-per-locus values (estimated using 33 assumed monomorphic loci) were 0·048 (Gulf red drum) and 0·046 (Atlantic red drum). Tests of heterogeneity in allele frequencies between year classes at individual localities and across regions (Gulf and Atlantic) were non-significant. Tests of spatial (geographic) heterogeneity indicated that red drum are weakly subdivided: genetically-differentiated subpopulations occur in the northern Gulf and along the south-eastern Atlantic coast. Genetic data were consistent with the hypothesis that red drum within the Gulf and along the Atlantic coast comprise singie subpopulalions. Genetic differences between Gulf and Atlantic red drum seem likeiy to stem from historical or recent interactions between dispersal and impediments to gene flow.     

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.     

Allozymic variation of the endangered killifishAphanius iberus and its application to conservation

Synopsis Genetic differentiation and patterns of variability in the endangered Iberian endemic,Aphanius iberus, were analyzed by allozyme electrophoresis as a valuable database for conservation purposes. Genetic variability values expressed as heterozygosity (H = 0.015–0.097) were close to the values found in other members of Cyprinodontidae (H = 0.012–0.123). Polymorphism values (P = 0.125–0.542) were higher than reported in the literature (P = 0.036–0.150) for Cyprinodontidae. Significant correlation existed between salinity values and genetic variability expressed as heterozygosity (r = – 0.76, p < 0.01) and polymorphism (r = – 0.60, p = 0.04). Low genetic variability values (H = 0.024–0.055, P = 0.125–0.292) were exhibited by populations which inhabit salty lagoons. The highest values were found in populations occurring in marshes and irrigation channels (H = 0.051–0.097, P = 0.250–0.542). Associations among genetic, geographic and ecological parameters were tested using a Mantel test indicated that most of the genetic distances were explained by geographic distances but not by ecological factors, suggesting that isolation by distance could be the main factor explaining the differentiation between sites. According to the genetic distances obtained, two mainA. iberus groups were discernible: the Atlantic and Mediterranean. Genetic distances between both groups (DRogers = 0.179–0.261) were higher than values between recognized species of other cyprinodontids (DRogers = 0.11–0.27). On the basis of genetic distances we have dated the fragmentation of both populations to the Upper Miocene-Pliocene when most of the Mediterranean sea dried up. Subsequently, gene flow between Mediterranean and Atlantic populations was interrupted. The results of our genetic analyses suggested the existence of five operational conservation units (OCUs) forA. iberus. These units are defined as a continuous area limited by geographical boundaries, and inhabited by one or more populations sharing the same genetic pattern.     

Genetic diversity and genome size variability in Linum austriacum (Lineaceae) populations

Genetic diversity and genome size variability were studied in 16 geographical populations of Linum austriacum (Lineaceae). Genetic diversity parameters were determined in each population based on ISSR molecular markers. AMOVA test, Gst value and Hickory test revealed significant molecular difference among the studied populations. Mantel test showed correlation between genetic distance and geographical distance in these populations. NJ tree and NeighborNet network grouped the studied plant specimens in 3 major clusters. STRUCTURE analysis identified 12 allelic combinations in agreement with K-Means clustering result. These analyses revealed the presence of genetic variability both among and within studied population. The plant specimens of these geographical populations also differed significantly in their genome size.     

Allozyme analyses of the genus Trisopterus: taxonomic status and population structure of the poor cod

Genetic analysis of the four Trisopterus (Gadidae) taxa suggests that the interrelationships of the two morphs of poor cod ( T. minutus minutus in the Atlantic and T. minutus capelanus in the Mediterranean) should be reconsidered. The Mediterranean poor cod T. m. capelanus is more closely related to bib T. luscus than to the Atlantic poor cod, so the population structure in the Atlantic and Mediterranean poor cod must be considered separately. Among 635 Atlantic individuals there was some evidence of poor cod population differentiation (allele frequency heterogeneity test P <0·0005; F _ST=0·0135, P ≤0·0005). Levels of genetic variation were similar to those reported for related gadoid species. Some differentiation was present on the Norwegian coast (samples from Trondheimsfjord) and between the Faeroe Islands (Faeroe Bank) and the adjacent European coastal location. In contrast no statistically significant population differentiation was evident in Mediterranean poor cod, but fewer samples and individuals were screened.     

Regional population structure of a widely introduced estuarine invertebrate: Nematostella vectensis Stephenson in New England

Nematostella vectensis is an infaunal anemone occurring in salt marshes, lagoons and other estuarine habitats in North America and the United Kingdom. Although it is considered rare and receives protection in England, it is widely distributed and abundant in the United States, particularly along the Atlantic coast. Recent studies suggest that both anthropogenic dispersal and reproductive plasticity may significantly influence the genetic structure of N. vectensis populations. Amplified fragment length polymorphism (AFLP) fingerprinting of individuals from nine populations in the northeastern United States indicates that stable populations are maintained by both asexual and sexual reproduction; in some cases asexually reproducing lineages exist within sexually reproducing populations. F statistics reveal extraordinarily high degrees of genetic differentiation between populations, even those separated by very short distances (less than 100 m). Genetic distances show little to no correlation with geographical distances, consistent with a role for sporadic, geographically discontinuous dispersal coupled with limited gene flow. No single genotype was found at more than one site, despite apparent homogeneity of habitat. In contrast with reported genotypic distributions for Nematostella in the United Kingdom, where a single clonal genotype dominates at multiple sites through southern England, our data thus fail to support the hypothesis of a general-purpose genotype in the northeastern United States. However, they are consistent with important roles for reproductive plasticity, sporadic introductions and complex local population dynamics in determining the global and regional distribution of this species.     

Discord in the family Sparidae (Teleostei): divergent phylogeographical patterns across the Atlantic-Mediterranean divide

The Strait of Gibraltar has been proposed to be the divide between two marine biogeographical regions, the Mediterranean Sea and the Northeast Atlantic. Intraspecific studies have shown, for several of the examined species, a reduction of gene flow between the two basins. The present study examines genetic variation at nuclear and mitochondrial loci in five marine teleost species belonging to the family Sparidae. Four samples for each species were analysed spanning the Northeast Atlantic and the Mediterranean. For all individuals 17 allozyme loci were scored and a combined single strand conformation polymorphism-sequencing approach was used to survey approximately 190 bp of the mitochondrial DNA (mtDNA) D-loop region. All five species share similar biological features. For three species, namely Lithognathus mormyrus, Spondyliosoma cantharus, and Dentex dentex, large mtDNA divergence was observed between Atlantic and Mediterranean samples. Little or no mtDNA differentiation was found in the other two species, Pagrus pagrus and Pagellus bogaraveo. Allozyme data revealed strong differentiation when comparing Atlantic and Mediterranean samples of L. mormyrus and D. dentex, moderate for P. pagrus, and no differentiation for P. bogaraveo and S. cantharus. These results provide evidence for a sharp phylogeographical break (sensu Avise) between the Atlantic and the Mediterranean for two (or possibly three) sparid species of the five investigated. At the same time, the obtained results for the other two species raise the question on which ecological/historical factors might have caused the observed discrepancy in the geographical distribution of genetic variation among otherwise biologically similar species.     

Genetic diversity and spatial correlation patterns unravel the biogeographical history of the European sweet vernal grasses (Anthoxanthum L., Poaceae)

Different processes have contributed to shaping the present distribution of the European biotas. Up to three different tertiary- to quaternary-time-scale evolutionary scenarios have been proposed to interpret the divergence and genetic structuring of plant species in Europe. In the present study, the Amplified Fragment Length Polymorphisms technique has been used to unravel the species and regional phylogeography of the European sweet vernal grasses (Anthoxanthum L. Poaceae). Forty-six populations belonging to all seven European species of Anthoxanthum and covering a broad geographical and ecological range were selected. Different phylogeography and population genetics diversity and structure estimates indicated a clear divergence of old Messinian Mediterranean lineages, followed by a pre-Pliocene split between Mediterranean annuals and Eurosiberian perennials and a more recent Pleistocene differentiation of Arctic-Alpine, Atlantic and Submediterranean diploid to polyploid landraces. Regional and population correlation tests between geographical and genetic distances allowed to postulate distinct pre- and post-glacial colonization pathways across Europe for the taxa of this widespread genus.     

Genetic Variation Within and Among Metal-Tolerant and Non-Tolerant Populations of Armeria maritima (Mill.) Willd. s.l. (Plumbaginaceae) in Central and Northeast Germany

Abstract: Six metal-tolerant populations and sub-populations of Armeria maritima ssp. halleri, ssp. hornburgensis, and ssp. bottendorfensis and two non-tolerant populations of ssp. elongata in Central and Northeast Germany have been analysed using RAPD markers. The populations show very strong genetic differentiation (Φ_ST = 0.46), corresponding gene flow between them is low (N_em = 0.29). A moderate positive correlation between the matrices of genetic and geographical distances was found between the seven populations and sub-populations of central Germany (r = 0.68, p < 0.001). Calculated parameters of genetic variability are molecular variance, percentage of heterozygosity and percentage of polymorphic loci. A significant correlation between population size and parameters of genetic variability was not recognisable. Genetic structure was investigated by an analysis of molecular variance (AMOVA). The studied populations show strong genetic differentiation. Genetic variation within populations ("normal" as well as metalliferous) is higher (53.9 %) than among them (46.1 %). Six hypotheses of possible genetic relatedness between the studied populations have been tested by AMOVA. A data set structure above the populational level is hardly recognisable. It was impossible to combine the populations to edaphic (tolerant and "non-tolerant") or taxonomic groups. A. maritima ssp. halleri of the north Harz mountains and ssp. hornburgensis are clearly separated from a geographical group containing all other populations (across taxonomic and edaphic boundaries). These results are a further indication for a polyphyletic origin of metal-tolerant populations of A. maritima s.l. by multiple colonizations of metalliferous sites from neighbouring populations on non-metalliferous soil.     

A three‐way contact zone between forms of Patella rustica (Mollusca: Patellidae) in the central Mediterranean Sea

Previous studies have reported the occurrence of three differentiated mtDNA lineages within Patella rustica in the Mediterranean Sea. Two hypotheses have been proposed to explain these observations: (1) the maintenance of ancestral polymorphism within a single species; (2) the occurrence of cryptic species not identified previously. To distinguish between these hypotheses, we screened the genetic variability at nine allozyme loci, an intron from the α‐amylase gene and a mitochondrial gene for 187 individuals of P. rustica sampled from seven Mediterranean localities. Eight additional localities were screened for the last two markers to place the differentiated lineages in a clear geographic context. Our results demonstrate that the three mtDNA lineages correspond to three distinct nuclear genotype clusters and provide further details on their distribution: the cluster corresponding to the mtDNA lineage from the Atlantic and western Mediterranean extends as far as the south coast of Italy, whereas the remaining two clusters occur in sympatry in the eastern Mediterranean. One of the eastern Mediterranean clusters is highly differentiated and seems to be reproductively isolated from the codistributed form; we therefore suggest that it corresponds to a new species. The remaining two clusters are less differentiated and form a contact zone across south Italian shores. This three‐way contact zone constitutes an interesting model for the study of speciation in the marine realm. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 154–169.     

Genetic variation in the soil phthiracarid mite, Steganacarus (S.) magnus (Nicolet, 1855) (Acarida, Oribatida) (Notulae Oribatologicae XL)

Genetic divergence and variability at 14 enzyme loci were examined in and between Italian populations of two edaphic Oribatid (Acarida, Oribatida) species, Steganacarus (Steganacarus) magnus (8 populations) and S. (S.) hirsutus (1 population). The seven populations belonging to S. (S.) magnus can be divided into two groups according to their phenotype, form anomala (A) (MON, ARG, AST, CDO) and form magna (M) (MAL, MAM, RIF) while another can be considered as hybrid between the two preceding groups (ZOC). Genetic identity (I) values between the S. (S.) magnus populations in spite of their morphological differences ranged from 0.977 to 1.000 showing the great genetic similarity of simple local populations while those of S. (S.) hirsutus indicated two distinct morphological species. The genetic distances between all the populations examined were very low despite the ecological differences and geographical distances between the collecting sites. Genetic variability estimates in all the populations of both species were very low when compared to those reported for most arthropods. Some explanatory considerations are suggested.     

Genetic structure and history of populations of the deep-sea fish Helicolenus dactylopterus (Delaroche, 1809) inferred from mtDNA sequence analysis

Helicolenus dactylopterus is an Atlantic benthopelagic fish species inhabiting high-energy habitats on continental slopes, seamounts and islands. Partial sequences of the mitochondrial control region (D-loop) and cytochrome b (cyt b) were used to test the hypothesis that H. dactylopterus disperses between continental margin, island and seamount habitats on intraregional, regional and oceanic scales in the North Atlantic. Individuals were collected from five different geographical areas: Azores, Madeira, Portugal (Peniche), Cape Verde and the northwest Atlantic. D-loop (415 bp) and cyt b (423 bp) regions were partially sequenced for 208 and 212 individuals, respectively. Analysis of variation among mitochondrial DNA sequences based on pairwise F-statistics and AMOVA demonstrated marked genetic differentiation between populations in different geographical regions specifically the Mid-Atlantic Ridge (Azores)/northeast Atlantic (Portugal, Madeira) compared to populations around the Cape Verde Islands and in the northwest Atlantic. Some evidence of intraregional genetic differentiation between populations was found. Minimum-spanning network analysis revealed star-shaped patterns suggesting that populations had undergone expansion following bottlenecks and/or they have been colonized by jump dispersal events across large geographical distances along pathways of major ocean currents. Mismatch distribution analysis indicated that Azores and northwest Atlantic populations fitted a model of historical population expansion following a bottleneck/founder event estimated to be between 0.64 and 1.2 million years ago (Ma).     

Phylogeographic evidence for the postglacial colonization of the North and Baltic Sea coasts from inland glacial refugia by Triglochin maritima L.

We investigated the geographical distribution of genetic variation in 67 individuals of Triglochin maritima from 38 localities across Europe using AFLP markers. Analysis of genetic variation resulted in the recognition of two major genetic groups. Apart from few geographical outliers, these are distributed (1) along the Atlantic coasts of Portugal, Spain and France and (2) in the North Sea area, the Baltic Sea area, at central European inland localities, the northern Adriatic Sea coast and the Mediterranean coast of southwest France. Considering possible range shifts of T. maritima in reaction to Quaternary climatic changes as deduced from the present-day northern temperature limit of the species, Quaternary changes of coastline in the North Sea area and the very recent origin of the Baltic Sea, we conclude that the coastal populations of T. maritima in the North Sea and Baltic Sea areas originated from inland populations.     

Long-distance seed dispersal, clone longevity and lack of phylogeographical structure in the European distributional range of the coastal Calystegia soldanella (L.) R. Br. (Convolvulaceae)

Aim  To explore the relative effects of Quaternary climatic history vs. species-specific biological properties (high seed dispersability, high seed longevity, clonal growth) on phylogeographical structure in European Mediterranean and Atlantic Ocean and Black Sea material of the coastal dune plant Calystegia soldanella (L.) R. Br.
Location  Black Sea and European Mediterranean and Atlantic Ocean coasts.
Methods  Variation in amplified fragment length polymorphism was analysed at two different sampling levels. First, an entire-range sample from the Black Sea to the North Sea, including single individuals from sites evenly spread along this entire coast was analysed. Second, in a population-level sample, seven populations from the European Mediterranean and Atlantic Ocean coasts were analysed.
Results  Neither the entire-range nor the population-level sampling resulted in clear phylogeographical patterns. Instead, individuals from geographically distant areas were often genetically more similar to each other than individuals from the same area. Non-significant isolation-by-distance was found for both sampling approaches, and comparatively low levels of intrapopulational genetic variation were observed.
Main conclusions  The lack of phylogeographical structure in C. soldanella , in comparison with the clear phylogeographical patterns observed in other coastal plant species analysed previously, is postulated to be the result of the specific biology of C. soldanella . The combination of high seed longevity, high dispersability of seeds by sea water and clonal growth and probable high clone age are likely to be responsible for the observed absence of phylogeographical structure. This implies that extreme biological properties such as those shown by C. soldanella can either erase or prevent the formation of historical patterns of genetic variation.     

Genetic assessment of the Atlantic Forest bristle porcupine, Chaetomys subspinosus (Rodentia: Erethizontidae), an endemic species threatened with extinction

The bristle-spined porcupine, Chaetomys subspinosus, an endemic rodent from Atlantic Forest, was considered to be abundant in the recent past, but population reductions due to habitat loss and expansion of human activities caused this species to be included in the "vulnerable" category of the World Conservation Union Red List. We performed the first genetic assessment in natural populations of this focal species along its geographical distribution. Thirty-five non-invasive samples (hair) were collected from three natural populations in the Brazilian States of Sergipe, Bahia and Espírito Santo. Genetic similarity obtained by Jaccard's index, based on dominant RAPD and ISSR markers, varied between 25 and 100%. Four clusters, mainly coincident with the geographical distribution of the populations, were observed. Analysis of molecular variance based on 47 polymorphic loci showed that there was 15.99% genetic variability among populations and 84.01% within populations. The estimated genetic structure among populations (Φ(ST)) was 0.16. The populations may have formed a continuum along the past distribution of the Atlantic rainforest but historical events of human occupation resulted in recent divergence among sampled populations.     

Isoenzymatic analysis of four Anopheles (Kerteszia) bellator Dyar & Knab (Diptera: Culicidae) populations

Anopheles bellator is a small silvatic bromelia-breeding mosquito and is a primary human malaria vector species in Southern Brazil. The bromelia-breeding habitat of the species should accompany the Atlantic forest coastal distribution, where bromeliads are abundant. Nonetheless, records on An. bellator collections show a gap in the species geographical distribution. An. bellator has been recorded in Southern Brazil and in the Brazilian states of Bahia and Paraíba. It appears again in the island of Trinidad, in Trinidad and Tobago. The aim of this work was to measure gene flow between different populations of An. bellator collected in the northern and southern extremes of the geographic distribution of this species. Mosquitoes were captured in forest borders in Santa Catarina, S?o Paulo, and Bahia states in Brazil and in the island of Trinidad in Republic of Trinidad and Tobago. Genetic distances varied between 0.076 and 0.680, based on enzymatic profiles from 11 distinct isoenzymes. Results indicate the existence of low-level gene flow between Brazilian populations of An. bellator, and a gene flow was even lower between the Brazilian and the Trinidad populations. This finding lead us to hypothesize that An. bellator did not spread along the coast, but reached northeastern areas through inland routes.