Phylogenetic relationships and the temporal context for the diversification of African characins of the family Alestidae (Ostariophysi: Characiformes): evidence from DNA sequence data

Paleogene emergence and evolutionary history of the Amazonian fossorial fish genus Tarumania (Teleostei: Tarumaniidae)

Tarumania walkerae is a rare fossorial freshwater fish species from the lower Rio Negro, Central Amazonia, composing the monotypic and recently described family Tarumaniidae. The family has been proposed as the sister group of Erythrinidae by both morphological and molecular studies despite distinct arrangements of the superfamily Erythrinoidea within Characiformes. Recent phylogenomic studies and time-calibrated analyses of characoid fishes have not included specimens of Tarumania in their analyses. We obtained genomic data for T. walkerae and constructed a phylogeny based on 1795 nuclear loci with 488,434 characters of ultraconserved elements (UCEs) for 108 terminals including specimens of all 22 characiform families. The phylogeny confirms the placement of Tarumaniidae as sister to Erythrinidae but differs from the morphological hypothesis in the placement of the two latter families as sister to the clade with Hemiodontidae, Cynodontidae, Serrasalmidae, Parodontidae, Anostomidae, Prochilodontidae, Chilodontidae, and Curimatidae. The phylogeny calibrated with five characoid fossils indicates that Erythrinoidea diverged from their relatives during the Late Cretaceous circa 90 Ma (108–72 Ma), and that Tarumania diverged from the most recent common ancestor of Erythrinidae during the Paleogene circa 48 Ma (66–32 Ma). The occurrence of the erythrinoid-like †Tiupampichthys in the Late Cretaceous–Paleogene formations of the El Molino Basin of Bolivia supports our hypothesis for the emergence of the modern Erythrinidae and Tarumaniidae during the Paleogene.

Accelerated Diversification Explains the Exceptional Species Richness of Tropical Characoid Fishes

The Neotropics harbor the most species-rich freshwater fish fauna on the planet, but the timing of that exceptional diversification remains unclear. Did the Neotropics accumulate species steadily throughout their long history, or attain their remarkable diversity recently? Biologists have long debated the relative support for these museum and cradle hypotheses, but few phylogenies of megadiverse tropical clades have included sufficient taxa to distinguish between them. We used 1,288 ultraconserved element loci (UCE) spanning 293 species, 211 genera and 21 families of characoid fishes to reconstruct a new, fossil-calibrated phylogeny and infer the most likely diversification scenario for a clade that includes a third of Neotropical fish diversity. This phylogeny implies paraphyly of the traditional delimitation of Characiformes because it resolves the largely Neotropical Characoidei as the sister lineage of Siluriformes (catfishes), rather than the African Citharinodei. Time-calibrated phylogenies indicate an ancient origin of major characoid lineages and reveal a much more recent emergence of most characoid species. Diversification rate analyses infer increased speciation and decreased extinction rates during the Oligocene at around 30 million years ago (Ma) during a period of mega-wetland formation in the proto-Orinoco-Amazonas. Three species-rich and ecomorphologically diverse lineages (Anostomidae, Serrasalmidae, and Characidae) that originated more than 60 Ma in the Paleocene experienced particularly notable bursts of Oligocene diversification and now account collectively for 68% of the approximately 2,150 species of Characoidei. In addition to paleogeographic changes, we discuss potential accelerants of diversification in these three lineages. While the Neotropics accumulated a museum of ecomorphologically diverse characoid lineages long ago, this geologically dynamic region also cradled a much more recent birth of remarkable species-level diversity.

Pattern and timing of diversification in the African freshwater fish genus Distichodus (Characiformes: Distichodontidae)

BACKGROUND

Distichodus is a clade of tropical freshwater fishes currently comprising 25 named species distributed continent-wide throughout the Nilo-Sudan and most Sub-Saharan drainages. This study investigates the phylogenetic relationships, timing of diversification, and biogeographic history of the genus from a taxonomically comprehensive mutilocus dataset analyzed using Maximum Likelihood and Bayesian methods of phylogenetic inference, coalescence-based species-tree estimation, divergence time estimation, and inference of geographic range evolution.

RESULTS

Analyses of comparative DNA sequence data in a phylogenetic context reveal the existence of two major clades of similar species-level diversity and provide support for the monophyletic status of most sampled species. Biogeographic reconstruction on a time-scaled phylogeny suggest that the origins of the genus date back to the late Oligocene and that current geographic distributions are the result of a Congo Basin origin followed by dispersal and range expansion into adjacent ichthyofaunal provinces at different times during the evolutionary history of the group.

CONCLUSIONS

We present the most comprehensive phylogenetic, chronological, and biogeographic treatment yet conducted for the genus. The few instances of species paraphyly (D. teugelsi, D. fasciolatus) revealed by the resulting phylogenies are likely a consequence of post-divergence introgressive hybridization and/or incomplete lineage sorting due to recent speciation. Historical biogeographic findings are both in agreement and conflict with previous studies of other continent-wide African freshwater fish genera, suggesting a complex scenario for the assemblage of Africa's continental ichthyofaunal communities.

Origins of Afrotropical freshwater fishes

The Afrotropics house a diverse freshwater ichthyofauna with > 3000 species, almost all of which are endemic. Recent progress in dated phylogenetics and palaeontology of several groups of Afrotropical freshwater fishes (AFFs) has allowed the testing of palaeoecology- and palaeogeography-based hypotheses explaining their early presence in Africa. Seven hypotheses were tested for 37 most-inclusive monophyletic groups of AFFs. Results indicated that ten lineages originated from direct, but asynchronous, marine-to-freshwater shifts. These lineages contribute < 2% to the current AFF species richness. Eleven lineages colonized the Afrotropics from the Orient after the Afro-Arabian plate collided with Eurasia in the early Oligocene. These lineages contribute ~20% to the total diversity. There are seven sister relationships between Afrotropical and Neotropical taxa. For only three of them (4% of the species diversity), the continental drift vicariance hypothesis was not rejected. Distributions of the other four younger trans-Atlantic lineages are better explained by post-drifting long-distance dispersal. In those cases, I discuss the possibility of dispersal through the Northern Hemisphere as an alternative to direct trans-Atlantic dispersal. The origins of ten AFF lineages, including the most species-rich Pseudocrenilabrinae (> 1100 species), are not yet established with confidence.

Phylogenetic systematics of the driftwood catfishes (Siluriformes: Auchenipteridae): a combined morphological and molecular analysis

A comprehensive phylogeny of species relationships of the Auchenipteridae is reconstructed here with a large-scale taxon sampling based on combined morphological and molecular datasets. The hypothesized phylogeny includes most species of Auchenipteridae (97 of 124 valid species) and multiple members of siluriform families as an outgroup (32 species) to embrace the diversity of forms among related catfishes. As the first large-scale phylogeny of the Auchenipteridae, comparison between taxa included information from both morphology (264 characters) and mitochondrial and nuclear molecular markers (3490 nucleotides) from five genes: coI, 16S, rag2, myh6 and SH3PX3. Trees were generated under two different optimality criteria (Maximum Parsimony and Bayesian Inference). A new classification for the family is presented herein to bring the taxonomy more in line with the new phylogenetic hypothesis. The strict consensus tree corroborates the monophyly of superfamily Doradoidea, family Auchenipteridae and its two subfamilies, Centromochlinae and Auchenipterinae. The new classification scheme proposes nine tribes in Auchenipteridae, based on the monophyly of major groups in both subfamilies. Centromochlus, Glanidium and Tatia are each recovered as paraphyletic. To maintain a monophyletic classification, some species treated as Tatia and Centromochlus are assigned to genera not previously recognized as valid.

DNA barcoding uncovers extensive cryptic diversity in the African long-fin tetra Bryconalestes longipinnis (Alestidae: Characiformes)

To investigate the presence of cryptic diversity in the African longfin-tetra Bryconalestes longipinnis, we employed DNA barcoding in a phylogeographic context, as well as geometric morphometrics, documenting for the first time genetic and body shape variation in the species. Analysis of cytochrome oxidase I gene (coI) sequence variation exposed extremely high levels of genetic differentiation among samples from across the geographic range of the species (up to 18%), certainly much greater than the traditionally employed c. 3% sequence divergence heuristic threshold for conspecifics. Phylogeographic analyses of coI data revealed eight clusters/clades that diverge by >4% and up to 18% (p-distance), potentially representing cryptic members of a species complex. A clear biogeographic pattern was also uncovered, in which the two main coI lineages corresponded geographically with the upper Guinea (UG) and lower Guinea (LG) ichthyofaunal provinces of continental Africa, respectively. Within each of these main lineages, however, no apparent phylogeographic structuring was found. Despite strong genetic differentiation, there is considerable overlap in body shape variation between UG and LG populations. For the most part, morphological variation does not match the strength of the molecular phylogeographic signal. Therefore, the ability to reliably utilise external body shape for regional delimitation remains elusive. Further anatomical investigation appears necessary to establish whether compelling diagnostic morphological features do exist between the divergent lineages of the B. longipinnis complex uncovered in this study.

Species of Characidotrema Paperna & Thurston, 1968 (Monogenea: Dactylogyridae) from fishes of the Alestidae (Characiformes) in Africa: new species, host-parasite associations and first insights into the phylogeny of the genus

BACKGROUND

African tetras (Alestidae) belonging to Brycinus Valenciennes are known to be parasitized with monogeneans attributed to two genera, Annulotrema Paperna & Thurston, 1969 and Characidotrema Paperna & Thurston, 1968 (Dactylogyridae). During a survey of monogeneans parasitizing alestids, species of Characidotrema were collected in Cameroon, D. R. Congo, Senegal, South Africa, Sudan and Zimbabwe. This paper provides new morphological data and the first molecular analysis broadening our knowledge on the diversity of these parasites.

RESULTS

Seven species (four known and three new) of Characidotrema are reported from two species of Brycinus: C. auritum n. sp. and C. vespertilio n. sp. from B. imberi (Peters); and C. brevipenis Paperna, 1969, C. nursei Ergens, 1973, C. pollex n. sp., C. spinivaginus (Paperna, 1973) and C. zelotes Kritsky, Kulo & Boeger, 1987 from B. nurse (Rüppell). Species identification was based on morphological analysis of the sclerotized structures supported by nuclear ribosomal DNA (partial 18S rDNA, ITS1, and 28S rDNA) sequence data. Morphological analysis confirmed that the most apparent character distinguishing species in the genus is the morphology of the male copulatory organ and vagina. Observations on the haptoral sclerotized elements of these parasites by means of phase contrast microscopy revealed the presence of a sheath-like structure relating to the ventral anchor, a feature that supplements the generic diagnosis of Characidotrema. Maximum Likelihood and Bayesian analyses of the large subunit (28S) rDNA sequences recovered Characidotrema species isolated from the two Brycinus hosts as monophyletic, and indicated a closer relationship of this group to monogeneans parasitizing African cyprinids (Dactylogyrus spp.) and cichlids (species of Cichlidogyrus Paperna, 1960, Scutogyrus Pariselle & Euzet, 1995, and Onchobdella Paperna, 1968) than to those from catfishes (species of Quadriacanthus Paperna, 1961, Schilbetrema Paperna & Thurston, 1968 and Synodontella Dossou & Euzet, 1993). The overall agreement between the morphological diversification of the MCOs and the molecular tree observed in this study indicates that significant phylogenetic signals for clarifying relationships among species of Characidotrema are present in the characteristics of the MCO.

CONCLUSIONS

It seems that intra-host speciation is an important force shaping the present distribution and diversity of Characidotrema but further studies are necessary to confirm this hypothesis and assess questions related to the phylogeny of these parasites. To identify potential co-speciation events, co-phylogenetic analyses of these monogeneans and their alestid hosts are required.

Integrative approach reveals a new species of Nematocharax (Teleostei: Characidae)

An integrative approach based on morphological and multilocus genetic data was used to describe a new species of Nematocharax from the headwaters of the upper Contas River on the Diamantina Plateau, north-eastern Brazil and to infer the relationships among evolutionary lineages within this fish genus. Multispecies coalescent inference using three mitochondrial and five nuclear loci strongly supports a basal split between Nematocharax venustus and the new species, whose distinctive morphological characters include absence of filamentous rays on pelvic fins of maturing and mature males, reduced anal-fin lobe length and lower body depth. The unique morphological and genetic traits of the population from the upper Contas River were supported by previous reports based on cytogenetics, DNA barcode and geometric morphometrics, reinforcing the validation of the new species. The conservation status of this new species is discussed.

Phylogenomic Perspective on the Relationships and Evolutionary History of the Major Otocephalan Lineages

The phylogeny of otocephalan fishes is the subject of broad controversy based on morphological and molecular evidence. The primary unresolved issue pertaining to this lineage relates to the origin of Characiphysi, especially the paraphyly of Characiformes. The considerable uncertainty associated with this lineage has precluded a greater understanding of the origin and evolution of the clade. Herein, a phylogenomic approach was applied to resolve this debate. By analyzing 10 sets of transcriptomic data generated in this study and 12 sets of high-throughput data available in public databases, we obtained 1,110 single-copy orthologous genes (935,265 sites for analysis) from 22 actinopterygians, including 14 otocephalan fishes from six orders: Clupeiformes, Gonorynchiformes, Cypriniformes, Siluriformes, Characiformes, and Gymnotiformes. Based on a selection of 125 nuclear genes screened from single-gene maximum likelihood (ML) analyses and sequence bias testing, well-established relationships among Otocephala were reconstructed. We suggested that Gymnotiformes are more closely related to Characiformes than to Siluriformes and Characiformes are possibly paraphyletic. We also estimated that Otocephala originated in the Early-Late Jurassic, which postdates most previous estimations, and hypothesized scenarios of the early historical biogeographies of major otocephalan lineages.

Data on the multilocus molecular phylogenies of the Neotropical fish family Prochilodontidae (Teleostei: Characiformes)

The data presented herein support the article "Molecular phylogenetics of the Neotropical fish family Prochilodontidae (Teleostei: Characiformes)" (B.F. Melo, B.L. Sidlauskas, B.W. Frable, K. Hoekzema, R.P. Vari, C. Oliveira, 2016) [1], which inferred phylogenetic relationships of the prochilodontids from an alignment of three mitochondrial and three nuclear loci (5279 bp) for all 21 recognized prochilodontid species and 22 related species. Herein, we provide primer sequences, museum voucher information and GenBank accession numbers. Additionally, we more fully describe the maximum-likelihood and Bayesian phylogenetic analyses of the concatenated dataset, detail the Bayesian species tree analysis, and provide the maximum likelihood topologies congruent with prior morphological hypotheses that were compared with the unconstrained tree using Shimodaira-Hasegawa tests.

Molecular phylogenetics of the Neotropical fish family Prochilodontidae (Teleostei: Characiformes)

Migratory detritivores of the characiform family Prochilodontidae occur throughout the freshwaters of much of South America. Prochilodontids often form massive populations and many species achieve substantial body sizes; a combination that makes them one of the most commercially important fish groups on the continent. Their economic significance notwithstanding, prochilodontids have never been the subject of a comprehensive molecular phylogenetic analysis. Using three mitochondrial and three nuclear loci spanning all prochilodontid species, we generated a novel phylogenetic hypothesis for the family. Our results strongly support monophyly of the family and the three included genera. A novel, highly supported placement of Ichthyoelephas sister to the clade containing Prochilodus and Semaprochilodus diverges from a previous morphological hypothesis. Most previously hypothesized interspecific relationships are corroborated and some longstanding polytomies within Prochilodus and Semaprochilodus are resolved. The morphologically similar P. brevis, P. lacustris, P. nigricans and P. rubrotaeniatus are embedded within what is herein designated as the P. nigricans group. Species limits and distributions of these species are problematic and the group clearly merits taxonomic revision.

Phylogeny and biogeography of Triportheidae (Teleostei: Characiformes) based on molecular data

Triportheidae represents a relatively small family of characiform fishes with highly modified morphology. The relationship among characiform families is still unclear, and a phylogenetic analysis for the family including a representative number of Triportheus species has never been performed. Here, we inferred a phylogeny for 19 of the 22 species recognized for this family and two possible new Triportheus species using two mitochondrial and three nuclear genes. Our results show that (1) Triportheidae is monophyletic and a sister group of the clade consisting of the families Bryconidae and Gasteropelecidae; (2) Triportheus is monophyletic, but some species need to be reviewed and described; (3) all genera in Triportheidae, except for Agoniates originated in the period between Early Oligocene and Early Miocene; and (4) speciation in Triportheidae coincides with important geological events in South America, reinforcing the importance of time-calibrated trees to study fish evolution.

Annulotrema (Monogenea: Dactylogyridae) from the gills of African tetras (Characiformes: Alestidae) in Lake Turkana, Kenya, with descriptions of four new species and a redescription of A. elongata Paperna and Thurston, 1969

Four new and four previously described species of Annulotrema were collected from the gills of four species (three genera, i.e. Alestes, Hydrocynus and Brycinus) of African tetras from Lake Turkana, Kenya: Annulotrema alestesnursi Paperna, 1973 from Brycinus nurse; Annulotrema ansatum n. sp., Annulotrema besalis Řehulková, Musilová and Gelnar, 2014, Annulotrema bipatens n. sp., Annulotrema cucullatum n. sp., Annulotrema nili Paperna, 1973, and Annulotrema pontile n. sp. from Hydrocynus forskahlii; and Annulotrema elongata Paperna and Thurston, 1969 from Alestes baremoze and Alestes dentex. A. elongata is re-described on the basis of new material from A. baremoze. The sclerotized structures of the haptor and male copulatory organ of A. alestesnursi and A. elongata are illustrated from their type material. H. forskahlii is a new host record for A. besalis. The findings of A. besalis and A. elongata in Kenya represent a new locality records for these helminths. Three Annulotrema spp., namely A. besalis, A. elongata and A. pontile n. sp., share the same type of male copulatory organ, which may indicate a close relationship among these species.

Systematic and historical biogeography of the Bryconidae (Ostariophysi: Characiformes) suggesting a new rearrangement of its genera and an old origin of Mesoamerican ichthyofauna

Background

Recent molecular hypotheses suggest that some traditional suprageneric taxa of Characiformes require revision, as they may not constitute monophyletic groups. This is the case for the Bryconidae. Various studies have proposed that this family (considered a subfamily by some authors) may be composed of different genera. However, until now, no phylogenetic study of all putative genera has been conducted.

Results

In the present study, we analyzed 27 species (46 specimens) of all currently recognized genera of the Bryconidae (ingroup) and 208 species representing all other families and most genera of the Characiformes (outgroup). Five genes were sequenced: 16SrRNA, Cytochrome b, recombination activating gene 1 and 2 and myosin heavy chain 6 cardiac muscle. The final matrix contained 4699 bp and was analyzed by maximum likelihood, maximum parsimony and Bayesian analyses. The results show that the Bryconidae, composed of Brycon, Chilobrycon, Henochilus and Salminus, is monophyletic and is the sister group of Gasteropelecidae + Triportheidae. However, the genus Brycon is polyphyletic. Fossil studies suggest that the family originated approximately 47 million years ago (Ma) and that one of the two main lineages persisted only in trans-Andean rivers, including Central American rivers, suggesting a much older origin of Mesoamerican ichthyofauna than previously accepted.

Conclusion

Bryconidae is composed by five main clades, including the genera Brycon, Chilobrycon, Henochilus and Salminus, but a taxonomic review of these groups is needed. Our results point to a possible ancient invasion of Central America, dating about 20.3 ± 5.0 Ma (late Oligocene - early Miocene), to explain the occurrence of Brycon in Central America.

Sperm evolution in the family Alestidae with comparative data for the genus Chalceus (Ostariophysi: Characiformes)

Spermiogenesis and spermatozoa in six genera of the African family Alestidae plus the Neotropical genus Chalceusare described. Spermiogenesis is quite similar in all Alestidae and is identified as Type I and its variants. In Type I spermiogenesis, the flagellum of earliest spermatids lies lateral to the nucleus, and rotation of the nucleus towards the centriolar complex is observed. Nuclear rotation is complete reaching 90 degrees in Bryconalestes longipinnis, Brachypetersius altus, Brycinus imberi, B. lateralis, and Alestopetersius compressus; and is incomplete reaching 20 degrees in Micralestes acutidensand Rhabdalestesrhodesiensis. Spermatozoa morphology varies from a medial nucleus with fibrillar chromatin in the most basal genus Brycinusto a strongly eccentric nucleus with highly condensed chromatin in the more derived Rhabdalestesand Micralestes. Chalceushas a very similar spermatozoon to that found in Brycinussharing the fibrillar aspect of the chromatin in the nucleus. This feature is so far only observed in these two genera among African and Neotropical characiform fishes.

Are characiform fishes Gondwanan in origin? Insights from a time-scaled molecular phylogeny of the Citharinoidei (Ostariophysi: Characiformes)

Fishes of the order Characiformes are a diverse and economically important teleost clade whose extant members are found exclusively in African and Neotropical freshwaters. Although their transatlantic distribution has been primarily attributed to the Early Cretaceous fragmentation of western Gondwana, vicariance has not been tested with temporal information beyond that contained in their fragmentary fossil record and a recent time-scaled phylogeny focused on the African family Alestidae. Because members of the suborder Citharinoidei constitute the sister lineage to the entire remaining Afro-Neotropical characiform radiation, we inferred a time-calibrated molecular phylogeny of citharinoids using a popular Bayesian approach to molecular dating in order to assess the adequacy of current vicariance hypotheses and shed light on the early biogeographic history of characiform fishes. Given that the only comprehensive phylogenetic treatment of the Citharinoidei has been a morphology-based analysis published over three decades ago, the present study also provided an opportunity to further investigate citharinoid relationships and update the evolutionary framework that has laid the foundations for the current classification of the group. The inferred chronogram is robust to changes in calibration priors and suggests that the origins of citharinoids date back to the Turonian (ca 90 Ma) of the Late Cretaceous. Most modern citharinoid genera, however, appear to have originated and diversified much more recently, mainly during the Miocene. By reconciling molecular-clock- with fossil-based estimates for the origins of the Characiformes, our results provide further support for the hypothesis that attributes the disjunct distribution of the order to the opening of the South Atlantic Ocean. The striking overlap in tempo of diversification and biogeographic patterns between citharinoids and the African-endemic family Alestidae suggests that their evolutionary histories could have been strongly and similarly influenced by Miocene geotectonic events that modified the landscape and produced the drainage pattern of Central Africa seen today.

Evolutionary origin and early biogeography of otophysan fishes (Ostariophysi: Teleostei)

The biogeography of the mega-diverse, freshwater, and globally distributed Otophysi has received considerable attention. This attraction largely stems from assumptions as to their ancient origin, the clade being almost exclusively freshwater, and their suitability as to explanations of trans-oceanic distributions. Despite multiple hypotheses explaining present-day distributions, problems remain, precluding more parsimonious explanations. Underlying previous hypotheses are alternative phylogenies for Otophysi, uncertainties as to temporal diversification and assumptions integral to various explanations. We reexamine the origin and early diversification of this clade based on a comprehensive time-calibrated, molecular-based phylogenetic analysis and event-based approaches for ancestral range inference of lineages. Our results do not corroborate current phylogenetic classifications of otophysans. We demonstrate Siluriformes are never sister to Gymnotiformes and Characiformes are most likely nonmonophyletic. Divergence time estimates specify a split between Cypriniformes and Characiphysi with the fragmentation of Pangea. The early diversification of characiphysans either predated, or was contemporary with, the separation of Africa and South America, and involved a combination of within- and between-continental divergence events for these lineages. The intercontinental diversification of siluroids and characoids postdated major intercontinental tectonic fragmentations (<90 Mya). Post-tectonic drift dispersal events are hypothesized to account for their current distribution patterns.

Cryptic diversity of African tigerfish (genus Hydrocynus) reveals palaeogeographic signatures of linked neogene geotectonic events

The geobiotic history of landscapes can exhibit controls by tectonics over biotic evolution. This causal relationship positions ecologically specialized species as biotic indicators to decipher details of landscape evolution. Phylogeographic statistics that reconstruct spatio-temporal details of evolutionary histories of aquatic species, including fishes, can reveal key events of drainage evolution, notably where geochronological resolution is insufficient. Where geochronological resolution is insufficient, phylogeographic statistics that reconstruct spatio-temporal details of evolutionary histories of aquatic species, notably fishes, can reveal key events of drainage evolution. This study evaluates paleo-environmental causes of mitochondrial DNA (mtDNA) based phylogeographic records of tigerfishes, genus Hydrocynus, in order to reconstruct their evolutionary history in relation to landscape evolution across Africa. Strong geographical structuring in a cytochrome b (cyt-b) gene phylogeny confirms the established morphological diversity of Hydrocynus and reveals the existence of five previously unknown lineages, with Hydrocynus tanzaniae sister to a clade comprising three previously unknown lineages (Groups B, C and D) and H. vittatus. The dated phylogeny constrains the principal cladogenic events that have structured Hydrocynus diversity from the late Miocene to the Plio-Pleistocene (ca. 0-16 Ma). Phylogeographic tests reveal that the diversity and distribution of Hydrocynus reflects a complex history of vicariance and dispersals, whereby range expansions in particular species testify to changes to drainage basins. Principal divergence events in Hydrocynus have interfaced closely with evolving drainage systems across tropical Africa. Tigerfish evolution is attributed to dominant control by pulses of geotectonism across the African plate. Phylogenetic relationships and divergence estimates among the ten mtDNA lineages illustrates where and when local tectonic events modified Africa's Neogene drainage. Haplotypes shared amongst extant Hydrocynus populations across northern Africa testify to recent dispersals that were facilitated by late Neogene connections across the Nilo-Sahelian drainage. These events in tigerfish evolution concur broadly with available geological evidence and reveal prominent control by the African Rift System, evident in the formative events archived in phylogeographic records of tigerfish.

Phylogenetic relationships within the speciose family Characidae (Teleostei: Ostariophysi: Characiformes) based on multilocus analysis and extensive ingroup sampling

BACKGROUND

With nearly 1,100 species, the fish family Characidae represents more than half of the species of Characiformes, and is a key component of Neotropical freshwater ecosystems. The composition, phylogeny, and classification of Characidae is currently uncertain, despite significant efforts based on analysis of morphological and molecular data. No consensus about the monophyly of this group or its position within the order Characiformes has been reached, challenged by the fact that many key studies to date have non-overlapping taxonomic representation and focus only on subsets of this diversity.

RESULTS

In the present study we propose a new definition of the family Characidae and a hypothesis of relationships for the Characiformes based on phylogenetic analysis of DNA sequences of two mitochondrial and three nuclear genes (4,680 base pairs). The sequences were obtained from 211 samples representing 166 genera distributed among all 18 recognized families in the order Characiformes, all 14 recognized subfamilies in the Characidae, plus 56 of the genera so far considered incertae sedis in the Characidae. The phylogeny obtained is robust, with most lineages significantly supported by posterior probabilities in Bayesian analysis, and high bootstrap values from maximum likelihood and parsimony analyses.

CONCLUSION

A monophyletic assemblage strongly supported in all our phylogenetic analysis is herein defined as the Characidae and includes the characiform species lacking a supraorbital bone and with a derived position of the emergence of the hyoid artery from the anterior ceratohyal. To recognize this and several other monophyletic groups within characiforms we propose changes in the limits of several families to facilitate future studies in the Characiformes and particularly the Characidae. This work presents a new phylogenetic framework for a speciose and morphologically diverse group of freshwater fishes of significant ecological and evolutionary importance across the Neotropics and portions of Africa.