Position of Polyclithrum within Gyrodactylidae (Monogenoidea): incongruences between morphological and molecular phylogenies.

This study aimed to enhance our understanding in monogenoid evolution by using morphological and molecular data to determine kinship relationships between species and changes in morphological structures over time. We focused on variations in characteristics among the organisms of the family Gyrodactylidae, concentrating on the phylogenetic position of Polyclithrum with other genera in the family. We collected specimens of Polyclithrum from the striped mullet, Mugil cephalus and Swingleus, and Fundulotrema specimens from mummichog Fundulus heteroclitus in estuarine systems of South Carolina, United States. In addition, we analyzed them and other genera (including e.g., Mormyrogyrodactylus, Gyrodactyloides, and Macrogyrodactylus) using both morphological and molecular (18S rDNA) approaches. We performed phylogenetic trees based on Maximum Parsymony, Maximum Likelihood and Bayesian Inference, and constructed a character morphological matrix by Parsimony Reconstruction of Ancestral Character States method. Our results suggest a homoplastic origin with evolutionary convergences in characters, revealing that there is inconsistency between our data and previously published works based solely on morphological structures of the group. The homoplasy scenario found in Gyrodactylidae can be a result of the limited set of putative homologous morphological features. However, differences between the phylogenies based on morphology and those based on molecular data may arise from both databases. While morphology remains essential in understanding the evolution of this group, molecular data, otherwise, provide a less biased source of information for constructing phylogenetic hypotheses. Combining these data facilitates a better comprehension of the homologous status of morphological features and to understand Gyrodactylidae evolutionary history.

Effect of Host-Switching on the Ecological and Evolutionary Patterns of Parasites.

Speciation via host-switching is a macroevolutionary process that emerges from a microevolutionary dynamic where individual parasites switch hosts, establish a new association, and reduce reproductive contact with the original parasite lineage. Phylogenetic distance and geographic distribution of the hosts have been shown to be determinants of the capacity and opportunity of the parasite to change hosts. Although speciation via host-switching has been reported in many host-parasite systems, its dynamic on the individual, population and community levels is poorly understood. Here we propose a theoretical model to simulate parasite evolution considering host-switching events on the microevolutionary scale, taking into account the macroevolutionary history of the hosts, to evaluate how host-switching can affect ecological and evolutionary patterns of parasites in empirical communities at regional and local scales. In the model, parasite individuals can switch hosts under variable intensity and have their evolution driven by mutation and genetic drift. Mating is sexual and only individuals that are sufficiently similar can produce offspring. We assumed that parasite evolution occurs at the same evolutionary time scale as their hosts, and that the intensity of host-switching decreases as the host species differentiate. Ecological and evolutionary patterns were characterized by the turnover of parasite species among host species, and parasite evolutionary tree imbalance respectively. We found a range of host-switching intensity that reproduces ecological and evolutionary patterns observed in empirical communities. Our results showed that turnover decreased as host-switching intensity increased, with low variation among the model replications. On the other hand, tree imbalance showed wide variation and non-monotonic tendency. We concluded that tree imbalance was sensitive to stochastic events, whereas turnover may be a good indicator of host-switching. We found that local communities corresponded to higher host-switching intensity when compared to regional communities, highlighting that spatial scale is a limitation for host-switching. [Dispersal of parasites, opportunity and capacity of interaction, phylogenetic conservatism, and community structure.].

Hexabothriidae and Monocotylidae (Monogenoidea) from the gills of neonate hammerhead sharks (Sphyrnidae) Sphyrna gilberti, Sphyrna lewini and their hybrids from the western North Atlantic Ocean.

Neonates of hammerhead sharks (Sphyrnidae), Sphyrna lewini (Griffith and Smith, 1834), the sympatric cryptic species, Sphyrna gilberti Quattro et al., 2013, and their hybrids were captured in the western North Atlantic, along the coast of South Carolina, USA, between 2018 and 2019 and examined for gill monogenoids. Parasites were identified and redescribed from the gills of 79 neonates, and DNA sequences from partial fragments of the nuclear 28S ribosomal RNA (rDNA) and cytochrome c oxidase I mitochondrial DNA (COI) genes were generated to confirm species identifications. Three species of monogenoids from Hexabothriidae Price, 1942 and Monocotylidae Taschenberg, 1879 were determined and redescribed. Two species of Hexabothriidae, Erpocotyle microstoma (Brooks, 1934) and Erpocotyle sphyrnae (MacCallum, 1931), infecting both species of Sphyrna and hybrids; and 1 species of Monocotylidae, Loimosina wilsoni Manter, 1944, infecting only S. lewini and hybrids. Loimosina wilsoni 28S rDNA sequences matched those of Loimosina sp. from the southern coast of Brazil. Based on limited morphological analysis, Loimosina parawilsoni is likely a junior synonym of L. wilsoni. This is the first taxonomic study of monogenoids infecting S. gilberti and hybrids of S. gilberti and S. lewini.

Ecological super-spreaders drive host-range oscillations: Omicron and risk space for emerging infectious disease.

The unusual genetic diversity of the Omicron strain has led to speculation about its origin. The mathematical modelling platform developed for the Stockholm Paradigm (SP) indicates strongly that it has retro-colonized humans from an unidentified nonhuman mammal, likely originally infected by humans. The relationship between Omicron and all other SARS-CoV-2 variants indicates oscillations among hosts, a core part of the SP. Such oscillations result from the emergence of novel variants following colonization of new hosts, replenishing and expanding the risk space for disease emergence. The SP predicts that pathogens colonize new hosts using pre-existing capacities. Those events are thus predictable to a certain extent. Novel variants emerge after a colonization and are not predictable. This makes it imperative to take proactive measures for anticipating emerging infectious diseases (EID) and mitigating their impact. The SP suggests a policy protocol, DAMA, to accomplish this goal. DAMA comprises: DOCUMENT to detect pathogens before they emerge in new places or colonize new hosts; ASSESS to determine risk; MONITOR to detect changes in pathogen populations that increase the risk of outbreaks and ACT to prevent outbreaks when possible and minimize their impact when they occur.

Neotropical Monogenoidea 64. Cosmetocleithrum falsunilatum sp. n. (Monogenoidea, Dactylogyridae) parasite of the gills of Megalodoras uranoscopus (Siluriformes, Doradidae) from the Solimões river, near Iquitos, Peru.

Megalodoras uranoscopus (Eigenmann & Eigenmann) (Siluriformes, Doradidae) (the giant-talking catfish or the giant-raphael catfish), from the Peruvian Amazon, hosts a new species of Cosmetocleithrum described herein as Cosmetocleithrum falsunilatum sp. n. The male copulatory organ of the new species closely resembles that of Unilatus spp. - with multiple tight loops and non-articulated accessory piece - which reveals its morphological uniqueness among members of Cosmetocleithrum. A phylogenetic analysis using 28S rDNA of available sequences suggests that Cosmetocleithrum is composed by two basal clades, one of them composed by sequences of the new species and C. trachydorasi.

Food security and emerging infectious disease: risk assessment and risk management.

Climate change, emerging infectious diseases (EIDs) and food security create a dangerous nexus. Habitat interfaces, assumed to be efficient buffers, are being disrupted by human activities which in turn accelerate the movement of pathogens. EIDs threaten directly and indirectly availability and access to nutritious food, affecting global security and human health. In the next 70 years, food-secure and food-insecure countries will face EIDs driving increasingly unsustainable costs of production, predicted to exceed national and global gross domestic products. Our modern challenge is to transform this business as usual and embrace an alternative vision of the biosphere formalized in the Stockholm paradigm (SP). First, a pathogen-centric focus shifts our vision of risk space, determining how pathogens circulate in realized and potential fitness space. Risk space and pathogen exchange are always heightened at habitat interfaces. Second, apply the document-assess-monitor-act (DAMA) protocol developing strategic data for EID risk, to be translated, synthesized and broadcast as actionable information. Risk management is realized through targeted interventions focused around information exchanged among a community of scientists, policy practitioners of food and public health security and local populations. Ultimately, SP and DAMA protect human rights, supporting food security, access to nutritious food, health interventions and environmental integrity.

'Accidents waiting to happen'-Insights from a simple model on the emergence of infectious agents in new hosts.

This study evaluates through modelling the possible individual and combined effect of three populational parameters of pathogens (reproduction rate; rate of novelty emergence; and propagule size) on the colonization of new host species-putatively the most fundamental process leading to the emergence of new infectious diseases. The results are analysed under the theoretical framework of the Stockholm Paradigm using IBM simulations to better understand the evolutionary dynamics of the pathogen population and the possible role of Ecological Fitting. The simulations suggest that all three parameters positively influence the success of colonization of new hosts by a novel parasite population, but contrary to the prevailing belief, the rate of novelty emergence (e.g. mutations) is the least important factor. Maximization of all parameters results in a synergetic facilitation of the colonization and emulates the expected scenario for pathogenic microorganisms. The simulations also provide theoretical support for the retention of the capacity of fast-evolving lineages to retro-colonize their previous host species/lineage by ecological fitting. Capacity is, thus, much larger than we can anticipate. Hence, the results support the empirical observations that opportunity of encounter (i.e. the breakdown in mechanisms for ecological isolation) is a fundamental determinant to the emergence of new associations-especially Emergent Infectious Diseases-and the dynamics of host exploration, as observed in SARS-CoV-2. Insights on the dynamics of Emergent Infectious Diseases derived from the simulations and from the Stockholm Paradigm are discussed.

Emerging infectious disease: An underappreciated area of strategic concern for food security.

Emerging infectious diseases (EIDs) increasingly threaten global food security and public health. Despite technological breakthroughs, we are losing the battle with (re)emerging diseases as treatment costs and production losses rise. A horizon scan of diseases of crops, livestock, seafood and food-borne illness suggests these costs are unsustainable. The paradigm of coevolution between pathogens and particular hosts teaches that emerging diseases occur only when pathogens evolve specific capacities that allow them to move to new hosts. EIDs ought to be rare and unpredictable, so crisis response is the best we can do. Alternatively, the Stockholm Paradigm suggests that the world is full of susceptible but unexposed hosts that pathogens could infect, given the opportunity. Global climate change, globalized trade and travel, urbanization and land-use changes (often associated with biodiversity loss) increase those opportunities, making EID frequent. We can, however, anticipate their arrival in new locations and their behaviour once they have arrived. We can 'find them before they find us', mitigating their impacts. The DAMA (Document, Assess, Monitor, Act) protocol alters the current reactive stance and embodies proactive solutions to anticipate and mitigate the impacts of EID, extending human and material resources and buying time for development of new vaccinations, medications and control measures.

The role of ecological opportunity in shaping host-parasite networks.

Despite the great interest to quantify the structure of host-parasite interaction networks, the real influence of some factors such as taxonomy, host body size and ecological opportunity remains poorly understood. In this paper, we investigate the general patterns of organization and structure of interactions in two anuran-parasite networks in the Brazilian Pantanal (seasonally flooded environment) and Atlantic Forest (non-flooded forest). We present theoretical models to test whether the structures of these host-parasite interaction networks are influenced by neutrality, host taxonomy and host body size. Subsequently, we calculated metrics of connectance, nestedness and modularity to characterize the network structure. We demonstrated the structure networks were influenced mainly by body size and taxonomy of the host. Moreover, our results showed that the seasonally flooded environment present networks with higher connectance/nestedness and lower modularity compared to the other environment. The results also suggest that seasonal floods may promote ecological opportunities for new species associations.

Neotropical Monogenoidea. 63. Atopogyrodactylus praecipuus gen. et sp. n. (Gyrodactylidae), an oviparous gyrodactylid from the external surface of a bristlenose catfish Ancistrus sp. (Siluriformes: Loricariidae) from the Rondônian Amazon, Brazil.

Atopogyrodactylus n. gen. (Gyrodactylidae) is proposed for Atopogyrodactylus praecipuus n. sp. (type species by monotypy), a protandrous and oviparous gyrodactylid from the external surfaces of an unidentified bristlenose catfish Ancistrus sp. (Siluriformes: Loricariidae) from the head waters of the Rio Candeias in the State of Rondônia, Brazil. The new genus contains species morphologically similar to those of Nothogyrodactylus Kritsky Boeger, 1991 as shown by members of both genera having accessory copulatory sclerites associated with the male copulatory organ (MCO). Atopogyrodactylus differs from Nothogyrodactylus by its species lacking haptoral bars and having a sclerotized haptoral plate overlying the ventral anchors. The new species most closely resembles Nothogyrodactylus amazonicus Kritsky Boeger, 1991 by possessing a flared proximal filament on the egg and a single morphologically similar accessory copulatory sclerite associated with an allantoid MCO.

Dactylogyridae (Monogenoidea, Polyonchoinea) from the gills of Auchenipterus nuchalis (Siluriformes, Auchenipteridae) from the Tocantins River, Brazil.

Two species of Cosmetocleithrum Kritsky, Thatcher & Boeger, 1986 (both new) and two species of Demidospermus Suriano, 1983 (one new) are reported from the gills of the catfish Auchenipterus nuchalis, popularly known as "mapará", from the Tocantins River and tributaries, North Region of Brazil. Cosmetocleithrum berecae n. sp. differs from all other species presently known in the genus by the morphology of the anchors presenting an elongate shaft and short recurved point, a coiled male copulatory organ (MCO) with three rings, and an elongate slender accessory piece with a bifurcated distal end. Cosmetocleithrum nunani n. sp. differs from its congeners by the combination of the following features: (1) Ventral and dorsal anchors with moderately long curved shaft and short point; (2) Hooks with poorly developed thumb; (3) Hook pairs 5 and 6 similar to each other, but morphologically distinct from remaining hook pairs; and (4) MCO coiled, with approximately 1.5 rings. Demidospermus tocantinensis n. sp. is easily distinguished from other species of the genus by presenting an inverted-G-shaped MCO with a median knee-like expansion. Demidospermus osteomystax Tavernari, Takemoto, Lacerda & Pavanelli, 2010 is redescribed based on paratypes and specimens from the gills of A. nuchalis from the Tocantins River, a new host and locality records for this species. The monotypic Paracosmetocleithrum Acosta, Scholz, Blasco-Costa, Alves & Silva, 2017, the only other Neotropical genus reported in siluriforms besides Cosmetocleithrum with species presenting two ribbon-like projections on the posterior margin of the dorsal bar, is considered a junior subjective synonym of Cosmetocleithrum.

TITLE: Dactylogyridae (Monogenoidea, Polyonchoinea) des branchies d'Auchenipterus nuchalis (Siluriformes, Auchenipteridae) de la rivière Tocantins au Brésil. ABSTRACT: Deux espèces de Cosmetocleithrum Kritsky, Thatcher et Boeger, 1986 (toutes deux nouvelles) et deux espèces de Demidospermus Suriano, 1983 (une nouvelle) sont signalées des branchies du poisson-chat Auchenipterus nuchalis, communément appelé « mapará ¼, de la rivière Tocantins et affluents, Région Nord du Brésil. Cosmetocleithrum berecae n. sp. diffère de toutes les autres espèces actuellement connues dans le genre par la morphologie des anchors présentant un manche allongé et une pointe recourbée courte, un organe copulateur mâle (OCM) enroulé avec trois anneaux et une pièce accessoire allongée et mince avec une extrémité distale bifurquée. Cosmetocleithrum nunani n. sp. diffère de ses congénères par la combinaison des caractéristiques suivantes : (1) Anchors ventrales et dorsales avec tige incurvée modérément longue et pointe courte ; (2) Crochets avec pouce peu développé ; (3) Paires de crochets 5 et 6 similaires les unes aux autres, mais morphologiquement distinctes des paires de crochets restantes ; (4) OCM enroulé, avec environ 1,5 anneaux. Demidospermus tocantinensis n. sp. se distingue facilement des autres espèces du genre par un OCM en forme de G inversé avec une expansion médiane du genou. Demidospermus osteomystax Tavernari, Takemoto, Lacerda & Pavanelli, 2010 est redécrit sur la base de paratypes et de spécimens des branchies d'A. nuchalis de la rivière Tocantins, et représente un hôte nouveau et une localité nouvelle pour cette espèce. Le genre monotypique Paracosmetocleithrum Acosta, Scholz, Blasco-Costa, Alves & Silva, 2017, le seul autre genre néotropical signalé chez les Siluriformes en dehors de Cosmetocleithrum, avec des espèces présentant deux projections en forme de ruban sur la marge postérieure de la barre dorsale, est considéré comme synonyme subjectif junior de Cosmetocleithrum.

Gyrodactylus lilianae n. sp. (Polyonchoinea: Gyrodactylidae) from Rhamdia quelen (Quoy & Gaimard) (Siluriformes: Heptapteridae) from southern Brazil: a potential nuisance for aquaculture.

Species of Monogenoidea (Platyhelminthes) are in its majority ectoparasites of marine and freshwater fishes. Many species of the group can promote great economic losses to fish production systems worldwide. The present study describes a new species, Gyrodactylus lilianae n. sp., from the body surface, fins and barbels of a captive South American catfish, Rhamdia quelen (Quoy & Gaimard) (Siluriformes: Heptapteridae) from southern Brazil. The new species is morphologically similar to Neotropical species of Gyrodactylus von Nordmann, 1832 from Siluriformes from which it differs most conspicuously by the morphology of the hook with a pronounced convex heel, somewhat depressed, slightly pointed toe, and a small distal bulb. The identity of the new species is also strongly supported by phylogenetic analysis based on cytochrome c oxidase subunit 2 mitochondrial gene (cox2) sequences and the rDNA fragment ITS1-5.8-ITS2. Infections with the new species in captive R. quelen juveniles were considered the main causative agent of observed mortalities. Tissue damage caused by G. lilianae n. sp. apparently facilitated the occurrence of secondary infections by protists (Ichthyophthirius multifiliis) and bacteria (Aeromonas hydrophila).

Rapid divergence, molecular evolution, and morphological diversification of coastal host-parasite systems from southern Brazil.

This study assessed the role of historical processes on the geographic isolation, molecular evolution, and morphological diversification of host-parasite populations from the southern Brazilian coast. Adult specimens of Scleromystax barbatus and Scleromystax macropterus were collected from the sub-basin of the Nhundiaquara River and the sub-basin of the Paranaguá Bay, state of Paraná, Brazil. Four species of Gyrodactylus were recovered from the body surface of both host species. Morphometric analysis of Gyrodactylus spp. and Scleromystax spp. indicated that subpopulations of parasites and hosts could be distinguished from different sub-basins and locations, but the degree of morphological differentiation seems to be little related to geographic distance between subpopulations. Phylogenetic relationships based on DNA sequences of Gyrodactylus spp. and Scleromystax spp. allowed distinguishing lineages of parasites and hosts from different sub-basins. However, the level of genetic structuring of parasites was higher in comparison to host species. Evidence of positive selection in mtDNA sequences is likely associated with local adaptation of lineages of parasites and hosts. A historical demographic analysis revealed that populations of Gyrodactylus and Scleromystax have expanded in the last 250 000 years. The genetic variation of parasites and hosts is consistent with population-specific selection, population expansions, and recent evolutionary co-divergence.

Neotropical Monogenoidea. 60. Two new species of Gyrodactylus (Monogenoidea: Gyrodactylidae) from the armored-catfish, Pareiorhaphis parmula Pereira (Loricariidae) and from the cascarudo, Callichthys callichthys (Linnaeus) (Callichthyidae) from Brazil.

Two new species of Gyrodactylus are described from the body surface of two catfish species from southern Brazilian rivers. Gyrodactylus anaspidus n. sp. is described from the armored-catfish, Pareiorhaphis parmula (Loricariidae) and Gyrodactylus polyadenus n. sp. is described from the cascarudo, Callichthys callichthys (Callichthyidae). The new species differ from previously described neotropical species of Gyrodactylus by the relative morphology of their haptoral hard structures and male copulatory organ (MCO). Gyrodactylus anaspidus n. sp. has a superficial bar without a shield and an MCO with one row of spinelets (9-11 spinelets). Gyrodactylus polyadenus n. sp. presents a shield associated to a superficial bar, a deep bar with narrow extremities connected to the anchors, a subrectangular hooklet with a short point, and an MCO with one row of six spinelets. We also report that G. anaspidus n. sp. co-occurs with oviparous species of Gyrodactylidae on their respective loricariid hosts.

Host use dynamics in a heterogeneous fitness landscape generates oscillations in host range and diversification.

Colonization of novel hosts is thought to play an important role in parasite diversification, yet little consensus has been achieved about the macroevolutionary consequences of changes in host use. Here, we offer a mechanistic basis for the origins of parasite diversity by simulating lineages evolved in silico. We describe an individual-based model in which (i) parasites undergo sexual reproduction limited by genetic proximity, (ii) hosts are uniformly distributed along a one-dimensional resource gradient, and (iii) host use is determined by the interaction between the phenotype of the parasite and a heterogeneous fitness landscape. We found two main effects of host use on the evolution of a parasite lineage. First, the colonization of a novel host allowed parasites to explore new areas of the resource space, increasing phenotypic and genotypic variation. Second, hosts produced heterogeneity in the parasite fitness landscape, which led to reproductive isolation and therefore, speciation. As a validation of the model, we analyzed empirical data from Nymphalidae butterflies and their host plants. We then assessed the number of hosts used by parasite lineages and the diversity of resources they encompass. In both simulated and empirical systems, host diversity emerged as the main predictor of parasite species richness.

Embracing Colonizations: A New Paradigm for Species Association Dynamics.

Parasite-host and insect-plant research have divergent traditions despite the fact that most phytophagous insects live parasitically on their host plants. In parasitology it is a traditional assumption that parasites are typically highly specialized; cospeciation between parasites and hosts is a frequently expressed default expectation. Insect-plant theory has been more concerned with host shifts than with cospeciation, and more with hierarchies among hosts than with extreme specialization. We suggest that the divergent assumptions in the respective fields have hidden a fundamental similarity with an important role for potential as well as actual hosts, and hence for host colonizations via ecological fitting. A common research program is proposed which better prepares us for the challenges from introduced species and global change.

Is Marine Dispersion of the Lethargic Crab Disease Possible? Assessing the Tolerance of Exophiala cancerae to a Broad Combination of Salinities, Temperatures, and Exposure Times.

Since 1997, an emergent fungal disease named lethargic crab disease (LCD) has decimated stocks of the edible mangrove land crab Ucides cordatus (Linnaeus, 1763) (Brachyura: Ocypodidae) along the Brazilian coast, threatening the mangrove ecosystem and causing socioeconomic impacts. Evidence from a variety of sources suggests that the black yeast Exophiala cancerae (Herpotrichiellaceae, Chaetothyriales) has been responsible for such epizootic events. Based on the spatiotemporal patterns of the LCD outbreaks, the well-established surface ocean currents, and the range of ecological traits of Exophiala spp., a marine dispersal hypothesis may be proposed. Using in vitro experiments, we tested the survival and growth of E. cancerae CBS 120420 in a broad combination of salinities, temperatures, and exposure times. While variation in salinity did not significantly affect the growth of colony-forming units (CFUs) (P > 0.05), long exposure times visibly influenced an increase in CFUs growth (P < 0.05). However, higher temperature (30 °C) caused a reduction of about 1.2-fold in CFUs growth (P < 0.05). This result suggests that sea surface temperatures either above or below the optimum growth range of E. cancerae could play a key role in the apparent north-south limits in the geographical distribution of LCD outbreaks. In light of our results, we conclude that a fundamental step toward the understanding of LCD epidemiological dynamics should comprise a systematic screening of E. cancerae in estuarine and coastal waters.

The mitochondrial genome of the egg-laying flatworm Aglaiogyrodactylus forficulatus (Platyhelminthes: Monogenoidea).

BACKGROUND: The rather species-poor oviparous gyrodactylids are restricted to South America. It was suggested that they have a basal position within the otherwise viviparous Gyrodactylidae. Accordingly, it was proposed that the species-rich viviparous gyrodactylids diversified and dispersed from there. METHODS: The mitochondrial genome of Aglaiogyrodactylus forficulatus was bioinformatically assembled from next-generation illumina MiSeq sequencing reads, annotated, and compared to previously published mitochondrial genomes of other monogenoidean flatworm species. RESULTS: The mitochondrial genome of A. forficulatus consists of 14,371 bp with an average A + T content of 75.12 %. All expected 12 protein coding, 22 tRNA, and 2 rRNA genes were identified. Furthermore, there were two repetitive non-coding regions essentially consisting of 88 bp and 233 bp repeats, respectively. Maximum Likelihood analyses placed the mitochondrial genome of A. forficulatus in a well-supported clade together with the viviparous Gyrodactylidae species. The gene order differs in comparison to that of other monogenoidean species, with rearrangements mainly affecting tRNA genes. In comparison to Paragyrodactylus variegatus, four gene order rearrangements, i.e. three transpositions and one complex tandem-duplication-random-loss event, were detected. CONCLUSION: Mitochondrial genome sequence analyses support a basal position of the oviparous A. forficulatus within Gyrodactylidae, and a sister group relationship of the oviparous and viviparous forms.

Postglacial expansion pathways of red mangrove, Rhizophora mangle, in the Caribbean Basin and Florida.

PREMISE OF THE STUDY: The Last Glacial Maximum (LGM) was a period of massive range contraction. Post-LGM, water-dispersed coastal species, including the red mangrove (Rhizophora mangle), expanded poleward as propagules were transported by ocean currents. We assessed postglacial marine expansion pathways for R. mangle within the Caribbean Basin and Florida. METHODS: Six microsatellite loci were used to genotype 237 individuals from nine R. mangle populations in the Caribbean, Florida, and Northwest Africa. We evaluated genetic variation, population structure, gene flow along alternative post-LGM expansion pathways to Florida, and potential long-distance dispersal (LDD) from West Africa to Caribbean islands. KEY RESULTS: These R. mangle populations had substantial genetic structure (FST = 0.37, P < 0.0001) with three discrete population clusters (Caribbean mainland, Caribbean islands, and Florida). Genetic connectivity along the mainland pathway (Caribbean mainland to Florida) vs. limited gene dispersal along the Antilles Island pathway (Caribbean islands to Florida) supported Florida recolonization from Caribbean mainland sources. Genetic similarity of Northwest Africa and two Caribbean islands provided evidence for trans-Atlantic LDD. We did not find a pattern of decreasing genetic diversity with latitude. CONCLUSIONS: We outline a complex expansion history for R. mangle, with discrete pathways of recolonization for Florida and Caribbean islands. Contrary to expectation, connectivity to putative Caribbean mainland refugial populations via ocean currents, and not latitude, appears to dictate genetic diversity within Caribbean island and Florida R. mangle. These findings provide a framework for further investigation of additional water-dispersed neotropical species, and insights for management initiatives.