Zoological Journal of the Linnean Society

Species-level delimitation within the genus Trichomycterus remains one of the main systematic challenges within the Trichomycterinae, particularly in lineages characterised by conservative external morphology, high apparent intraspecific variation, and historical diagnostic criteria based primarily on body proportions, colouration and a few meristic characters. In central Chile, Trichomycterus areolatus has traditionally been interpreted as a widely distributed and morphologically variable species, whilst T. maculatus, originally described from "Santiago du Chili", has remained subordinate to this broad conception without a modern phylogenetic reassessment. Here we reassess the specific boundaries of T. areolatus sensu lato using an integrative approach that combines complete mitogenomes, estimates of genetic divergence and comparative morphology of the cephalic laterosensory system associated with the neurocranium. Phylogenetic analyses reveal T. areolatus sensu lato to be non-monophyletic and identify a deeply divergent lineage, geographically coherent and attributable to T. maculatus. This lineage differs from restricted T. areolatus by extensive mitochondrial divergence, comparable to that observed between recognised species of Trichomycterinae, and by discrete characters of the cephalic lateral line system, primarily related to the continuity of the supraorbital canal and the arrangement of the associated pores. The congruence between mitogenomic, nuclear and morphological evidence supports the revalidation of Trichomycterus maculatus Valenciennes, 1846, and calls for a more restricted geographic circumscription of T. areolatus. These results demonstrate that the diversity of Trichomycterinae in central Chile has been underestimated, modify previous interpretation of the distribution of the species involved, and highlight the value of integrating mitogenomics and neurocranial/laterosensory characters into the taxonomy of morphologically conservative siluriform lineages.

Polytypic species with large ranges may harbor unrecognized diversity because taxonomy ranks populations differing subtly in plumage as subspecies. The Ruddy Foliage-gleaner (Clibanornis rubiginosus) exemplifies this problem. It ranges from Mexico to Brazil, with 15 subspecies, and forms a non-monophyletic complex with two congeners, yet its songs had not been compared. We measured ten spectral and temporal variables on 104 recordings covering 14 of 15 subspecies. Bayesian linear mixed models showed three song groups: eight subspecies west of the Andes share a single-note song, whereas Amazonian and Guianan populations add a short introductory note and sing longer, lower-pitched songs. Within this group, watkinsorum sings the lowest-pitched and longest song and is phylogenetically closer to C. cinnamomeigula than to its Amazonian neighbors. The third group is C. cinnamomeigula alone, a white-eyed taxon in an otherwise dark-eyed group. Its high-pitched, vibrato song resembles none other in the genus. One-note and two-note songs differ in kind without intermediates, and every two-note taxon sequenced to date falls in one clade, so C. rubiginosus is paraphyletic. We recognize four species, C. rubiginosus sensu stricto, C. cinnamomeigula, C. watkinsorum, and C. obscurus. This raises Clibanornis from five species to eight and divides its only polytypic species.

BackgroundThe tribal classification of scarab dung beetles (Coleoptera: Scarabaeinae) is currently largely incomplete due to the lack of robust phylogenetic evidence supporting the assignment of many Afro-Eurasian and American genera to tribes. MethodsWe used ultraconserved elements (UCEs) to infer phylogenetic relationships across most Afro-Eurasian dung beetle lineages, including 25 of the 27 extant genera currently incertae sedis. ResultsWe recovered full support for the monophyly of previously recognised tribes and for several phylogenetically and morphologically clearly delimited new tribal-level clades, allowing us to propose a complete tribal classification for all Afro-Eurasian dung beetle genera. Thirteen new tribes are described and diagnosed: Aphengoecini trib. nov., Bohepilissini trib. nov., Catharsiini trib. nov., Chalconotini trib. nov., Circelliini trib. nov., Dwesasilvasedini trib. nov., Haroldiini trib. nov., Heliocoprini trib. nov., Janssensantini trib. nov., Macroderini trib. nov., Nesovinsoniini trib. nov., Pycnopanelini trib. nov. and Tanzanolini trib. nov. The tribe Coprini sensu novo is redefined as comprising three subtribes: Coprina, Onychothecina subtrib. nov. and Pedariina subtrib. nov. The tribe Odontolomini is downranked to a subtribe of Endroedyolini sensu novo, becoming Endroedyolini Odontolomina stat. nov. The tribe Onthophagini sensu novo is redefined and divided into three subtribes: Helictopleurina stat. nov., Oniticellina stat. nov. and Onthophagina; the remaining former subtribes of Oniticellini (Attavicinina, Drepanocerina and Liatongina) are synonymised with Oniticellina; the subtribe Alloscelina of Onthophagini is synonymised with Onthophagina (syn. nov.). The tribe Panelini stat. rev. and sensu novo, comprising the single genus Panelus, is revalidated and redefined. Updated morphological diagnoses of Elassocanthonini, Gymnopleurini, Onitini and Scarabaeini are provided. The genus Phaedotrogus is synonymised with Haroldius (Haroldiini) (syn. nov.). An identification key to all Afro-Eurasian dung beetle tribes is provided. DiscussionOur results establish a robust phylogenetic framework and revised tribal classification for Afro-Eurasian Scarabaeinae dung beetles, providing a foundation for future taxonomic, comparative and macroevolutionary research.

Catenulids are free-living flatworms, common in eutrophic freshwaters such as ponds, ditches, or peatbogs, with most of the diversity described from tropical regions to date. Although the majority of the species have been described from warmer climates, most molecular studies have been done on specimens from temperate zones in Europe. We addressed this gap by sampling for exotic species in localities available in a temperate climate. In this study, we investigated catenulid diversity in the greenhouses at the University of Warsaw Botanic Garden and recorded two species known only from tropical areas (Stenostomum paraguayense and Suomina evelinae) and one exotic species recorded previously from a greenhouse in Poland (Stenostomum corderoi). Additionally, in the latter species, we provide evidence for environmentally induced coloration of sensory pits, which has not been reported thus far. We placed the collected species on a phylogeny using barcoding of 18S, 28S, and COI genes and retrieved paraphyly of the family Catenulidae, with S. evelinae forming a sister group to the genus Paracatenula, and hence we propose a revision of its systematic position. In total, we recorded six species, including three with a wide cosmopolitan distribution (C. turgida, S. grande and S. tuberculosum), and provided sequences for five of them, three of which had no previous molecular records (S. paraguayense, S. evelinae and S. corderoi). Thus, we confirm that greenhouses represent an important source of exotic species for taxonomic work on microscopic invertebrates.

Tessellated calcified cartilage (TCC) is a hallmark of the chondrichthyan skeleton, yet its development early in ontogeny across the four major groups (batoids, galeomorphs, squalomorphs, and holocephalans) remains poorly understood. Specialised traits of TCC, such as multi-layered TCC and internal mineralised trabeculae, typically develop in response to feeding mechanics. In this study, we evaluated TCC morphology in the jaws of 12 representative taxa to observe its structure at an early ontogenetic stage to determine whether these specialised features had yet developed. Batoids consistently exhibited well-developed, homogeneous, polygonal tesserae early in ontogeny regardless of jaw morphology or feeding habit. In contrast, galeomorphs displayed high morphological heterogeneity. Notably, we document the first report of an extensive internal trabecular network in a non-batoid elasmobranch, observed in Ginglymostoma cirratum, which may serve to resist the mechanical pressures of specialised suction feeding. Furthermore, we identified voussoir tesserae in galeomorphs for the first time, extending their documented presence across all elasmobranch groups, where they display an inverted aspect ratio (wider than tall) compared to mature forms. The durophagous Mustelus mustelus exhibited surprisingly poor TCC development despite being a durophagous feeder, pointing to a pronounced ontogenetic lag. In Squatina oculata, TCC was characterised by large and thick tesserae and extensive fused tesseral regions which may relate to its explosive ambush predation mode, whereas the holocephalan Chimaera exhibited a poorly mineralized, mesh-like structure without resolvable discrete tesserae or trabeculae-matching findings from previous studies. Across all specimens, multi-layered TCC was absent, confirming that multi-layering develops later in ontogeny. These results demonstrate that generalised models of TCC development based on one group or a few taxa fail to capture the broader diversity of TCC morphology. It also opens up many exciting avenues for further study, and forms the basis for comparisons with fossil chondrichthyans, to investigate the evolution of TCC.

Nematodes of the superfamily Thelastomatoidea are found in the digestive system of various arthropods, feeding on their host microbiome. They are sometimes considered to be ecologically intermediate forms between free-living rhabditids and parasitic Spirurina, while phylogenetically they are nested within the latter. In addition to new morphological data on the male morphology, this manuscript presents the first nuclear genome assembly of a thelastomatid species, Cranifera cranifera, using long-read sequencing approach, making a total of three nuclear genomes available for superfamilyThelastomatoidea. The C. cranifera nuclear genome assembly presented here is 246 Mb long, consists of 7563 contigs, has an N50 of 43 kb and includes 94% of the BUSCO nematoda_odb12 genes. The mitochondrial genome is 24646 bases long, includes a complete set of protein coding, rRNA and tRNA genes, and a repetitive region 9731 bases long, which includes multiple copies of tRNA-Asn(gtt) and tRNA-Lys(ttt). The nuclear assembly also contained two sequence variants of the 28S rRNA gene, highlighting the presence of intragenomic variation within rRNA operon. The newly generated assemblies (nuclear and organelle) will add to a growing body of genomic resources for underrepresented and understudied animal parasitic nematodes from the Clade 3, enabling comprehensive studies in their phylogeny and trait evolution in the future.

Arcellidae is a family of testate amoebae within Arcellinida (Amoebozoa), comprising three recognized genera: Arcella, Galeripora, and Antarcella. Although species in the family have been studied for nearly two centuries, many historically described taxa and major morphological groups remain unsampled at the molecular level. Here, we provide a comprehensive review of Arcellidae and generate new cytochrome c oxidase subunit I (COI) sequences for arcellid species from Canadian peatlands, focusing on tall-shelled Arcella historically classified in section Altae sensu Deflandre. COI phylogenetic analyses recover a strongly supported monophyletic clade corresponding to North American representatives of Altae, providing the first molecular corroboration of this morphologically defined group. Within this clade, we redescribe Arcella leidyana based on modern material from Eeyou Istchee (Quebec). We further describe Galeripora purdoni sp. nov. from a calcareous fen in eastern Ontario, representing a novel terrestrial lineage within the genus, and redescribe Galeripora artocrea, which we transfer to Arcella based on congruent molecular and morphological evidence. Phylogenomic analyses of Arcellidae isolates from the Protist 10,000 Genomes Project reveal an additional deep lineage basal to Arcella and Galeripora. Together, these results highlight hidden diversity and demonstrate the importance of integrative approaches for resolving arcellid systematics and refining its classification.

Rapid radiations, where species quickly diversify with little to no change in the genetic composition of the taxa, provide unique opportunities to understand the processes underlying lineage divergence, especially when the newly formed species come into contact. This study examines three parapatrically distributed taxa of the Andean Diglossa carbonaria superspecies that differ strikingly in plumage and have been classified as an example of rapid lineage divergence. Using RADSeq data, we characterized the geographic structuring of genetic variation and investigated the possibility of introgressive hybridization at the contact zones between D. humeralis atterima and D. b. brunneiventris in northern Peru and between D. b. brunneiventris and D. carbonaria in Bolivia. We found weak genetic differentiation between D. humeralis atterima and D. b. brunneiventris and low, but diagnosable, differentiation between D. b. brunneiventris and D. carbonaria. At the contact zone between D. humeralis atterima and D. b. brunneiventris, the lack of genetic differentiation did not allow us to determine if hybridization was occurring between the taxa. In contrast, clustering analyses, diagnostic allele identification, and PCA analyses showed geographic patterns consistent with introgressive hybridization at the contact zone between D. b. brunneiventris and D. carbonaria, a geographic region where birds that are intermediate in plumage have been observed. Finally, we found a genetic break within the distribution of D. b. brunneiventris. The genetic divergence across this [~]450 km wide break is greater than that found between D. humeralis atterima and D. b. brunneiventris. Our results add to previous work documenting weak genetic differentiation between taxa that have striking plumage differences, and in showing that plumage color may be a poor phylogenetic marker. Lay SummaryO_LIWe studied three closely related avian taxa in Peru and Bolivia which have different plumages and adjacent ranges to examine how genetically distinct they are. C_LIO_LITo do this, we used RADseq data from 72 flowerpiercers sampled across their ranges to examine their population structure and to test whether the three taxa hybridize where their ranges meet. C_LIO_LIDespite their striking differences in plumage color, the three species showed few genetic differences. In one area where the ranges are adjacent, the groups were so similar that interbreeding could not be confirmed. In another, there was evidence of admixture, supported by observations of birds with intermediate plumage. C_LIO_LIFor these taxa, feather color may not reflect evolutionary relationships, and more extensive genetic sampling is needed to understand how these plumage differences evolved. C_LI

The marine sponge Hymeniacidon perlevis is a globally-distributed species, likely because it has been extensively spread through human means. The status of this species in the Western Atlantic has been difficult to discern due to the presence of a morphologically similar species Hymeniacidon heliophila. Here, we have collected Hymeniacidon specimens from the H. heliophila type location and compared their morphology and genotypes to material from Europe, North and South America, and publicly available datasets. Specimens from the type location closely matched the original description of H. heliophila, and were morphologically indistinguishable from H. perlevis. Multilocus sequencing data confirm that these samples are indistinguishable from H. perlevis, and that the name H. heliophila should therefore be considered a junior synonym of H. perlevis. Analysis of a global cox1 dataset further revealed significantly higher genetic diversity in Europe than in the remainder of the world combined, supporting a European origin for the species and suggesting that all other genotyped populations are introductions. In the Western Atlantic, we confirm the presence of H. perlevis in the Gulf of Mexico, but contrary to some past reports, are unable to confirm its presence in the Caribbean. Our results clarify the taxonomy, biogeography, and recent history of one of the worlds most widespread marine sponges.

Among Madagascar primates, the sportive lemurs (family Lepilemuridae) have seen their species diversity increase from eight in 2005 to 26 in 2009 mostly by applying the phylogenetic species concept to DNA barcode data. Despite the genus being speciose, only one case of sympatry is known from northern Madagascar, where two sportive lemur species described based on low mtDNA divergence, Lepilemur ankaranensis and Lepilemur milanoii, were found to co-occur at the center of their joint distribution range. Here, to clarify the taxonomy of these two species and examine their sympatry, we apply an integrative taxonomic framework to genomic and morphological data from 84 individuals of L. ankaranensis and L. milanoii, encompassing their entire distribution range and the forest of Analafiana, beyond their southernmost limit. Using clustering, multivariate, and isolation by distance analyses, we find no evidence of a sympatric zone and show that despite clear genetic differentiation between regions, the genomic and morphological diversity of the L. ankaranensis, L. milanoii-Analafiana group is clinal and explained by geographic distance. These results clarify that L. milanoii is a junior synonym of L. ankaranensis and that the Analafiana forest population belongs to L. ankaranensis, extending its distribution. It further implies that the 'sympatric' zone, the Andrafiamena forest, hosts conspecific individuals with slightly differentiated mtDNA backgrounds, rather than slightly differentiated sympatric species. Lastly, we re-evaluate the IUCN conservation metrics of L. ankaranensis, which continue to qualify as Endangered (EN) under the B1ab(i-v) criteria.

Despite their currently scarce taxonomic diversity, rhinocerotoids were among the most evolutionarily successful clades of large herbivorous mammals throughout the Caenozoic. Within an array of morphological adaptations, the cranial horn represents the clades most remarkable and name-giving feature, imposing significant morpho-functional demands on the skull. In this paper, patterns and drivers of the rhinos cranial evolution were investigated for the first time by compiling a three-dimensional geometric morphometric dataset of living and extinct species. Multiple aspects of morphological evolution were explored using phylogenetic comparative methods, including craniofacial evolutionary allometry (CREA - tendency of larger species to have longer faces), phylogenetic constraints, and tempo of evolution. Cranial shape variation linked to horn presence and size evolved under a phylogenetically constrained framework, with a notable transition from hornless to horned species. Rhinos significantly deviated from CREA, likely due to diversity of cranial forms and proportions that evolved independently across the clade in response to varying horn morphologies and dietary habits. Hornless and horned rhinos exhibited similar rates of cranial evolution, and shape variation was obtained through multiple episodes of accelerated evolution. This highlights the role of morphological innovations and Caenozoic global cooling events in the emergence of phenotypic diversity.

Hydrozoa is a group of relatively simple animals with a well-developed nervous system. The nervous system in all hydrozoan medusae is highly conserved and includes outer and inner nerve rings at the bell margin, a neural network in the manubrium, and radial neural pathways that connect them. However, one element of the nervous system shows substantial variability among species: the subumbrella neural network. We examined the structure of the nervous and muscular systems in the subumbrella of 14 species of hydrozoan medusae. The main conclusion of this study is that the distribution of neural networks in the subumbrella strongly correlates with the distribution of smooth radial muscles. This correlation suggests that smooth radial muscles are the primary target of the subumbrella nervous system. Most species in the order Anthoathecata show a trend toward secondary loss of the neural networks and radial smooth muscle fibers in the subumbrella region, concentrating neural elements and smooth muscles only in the radial pathways along the radial canals. By contrast, all studied species in the order Leptothecata have neural networks in the subumbrella area, as well as radial smooth muscle fibers spread throughout the entire subumbrella region. The correlation between radial smooth muscles and the nervous system is also observed in the radial pathways along the radial canals. All species with thick bundles of smooth radial muscles along the radial canals have clearly defined, dense neural pathways running along or even embedded within the smooth muscle bundles.

Color polymorphism can facilitate local adaptation, maintain intraspecific diversity, or reflect early stages of speciation. Clownfishes (Amphiprion spp.) typically display a simple black, orange, and white pattern, but the saddleback clownfish (Amphiprion polymnus) shows striking variation in melanism and the number of vertical bars, which are thought to play a role in species recognition. In 2024, a revision on iNaturalist split A. polymnus into multiple species based solely on color pattern and geographic range. This raises the question of whether these morphs represent true species or intraspecific polymorphism, which we tested using genomic and image-based data. We sampled 97 individuals from seven populations across the species range and quantified color patterns from standardized photographs. Phenotypic and genomic analyses reveal a complex pattern of divergence. Image analysis identified three distinct phenotypic clusters, with A. polymnus, A. annamensis, and A. laticlavius each showing consistent differences in saddle shape and vertical bar extent. ADMIXTURE resolved three distinct genetic groups corresponding to the morphs. Pairwise FST (0.54-0.71) and dxy indicate extremely high differentiation between A. polymnus and A. annamensis, consistent with species-level divergence, whereas A. laticlavius shows much lower differentiation from A. polymnus (FST 0.09-0.18) and higher differentiation from A. annamensis (FST 0.64-0.66). Overall, phenotypic and genomic data show structured variation, but the status of A. laticlavius remains ambiguous. Our study reveals clear and structured divergence across the full range, yet the taxonomic interpretation of this variation remains inherently challenging. The key question remains: do these patterns reflect a single polymorphic species or a complex of closely related species?

Land-bridge islands are former mainland areas isolated by post-glacial sea-level rise (<15,000 years) and the most common island type. Because of their recurrent connectivity with continents, it is unclear whether species on land-bridge islands can undergo evolutionary changes associated with the more isolated oceanic islands ( island syndrome). Here, we test the hypothesis that the selective environment on land-bridge islands exerts predictable and consistent evolutionary shifts in morphological traits of songbirds. We apply Bayesian hierarchical models to a morphological dataset of 6,917 individuals comprising 185 species of songbirds from four land-bridge islands (Bioko, Sri Lanka, Taiwan and Trinidad) and adjacent continents. Across all 185 species, we find that occurrence on a land-bridge island has clear directional effects on five morphological traits related to beak, wing, and tarsus, as well as a general increase in body size. At the species level, 57 out of 90 tested species exhibit significant morphological divergence between land-bridge island and mainland, yet for only 20 of these are the land-bridge island populations recognised as distinct endemic subspecies. Our results show that occurrence on land-bridge islands has a detectable effect on passerine morphology consistent with the island syndrome, and suggest these islands harbour previously unrecognized unique biodiversity.

The Hesperiine genus Atrytonopsis Godman, 1900, occurs broadly across the American Southwest. Atrytonopsis margarita (Skinner, 1913) and Atrytonopsis python (W. H. Edwards, 1882) have look-alike appearances, concurrent flights, and geographic distributions which converge in New Mexico. Their similar wing markings and intertwined taxonomic history has made it challenging to fully understand the identity and occurrence of each. Burns (2015) revealed differences in genitalia, clarifying that they are distinct species. Genomic DNA analysis of more than 100 specimens now illuminates their genetic uniqueness, phylogenetic relationship, field identification challenges and details of their geographic distributions.

Urbanization has been previously shown to affect evolution of plants and animals by restricting gene flow, increasing genetic drift, and causing divergent selection between rural and urban populations, however, the effect of urbanization on terrestrial gastropod evolution has only been minimally researched. Most research on terrestrial gastropods primarily focusing on invasive pest species, and little attention is given to native species like Ariolimax columbianus (Pacific banana slug). There is no current published research on the phylogeography of A. columbianus. In this study, surface epithelial cells from 66 Ariolimax columbianus individuals were collected from 11 locations around Corvallis, Oregon, and one site in northern California. These samples were amplified and sequenced at two loci: cytochrome oxidase 1 (CO1) and the internal transcribed spacer 2 (ITS-2). This data was used to generate maximum-likelihood phylogenetic trees to better understand the population genetics of these local native gastropods. The CO1 phylogenetic analysis showed two major haplotypes around the city of Corvallis - northwestern and southern, while the ITS-2 phylogenetic analysis showed three general haplotypes around the city - northern, western, and southern. The results in this study show the presence of genetic breaks between many of these populations, possibly due to a combination of factors including anthropogenic fragmentation, natural barriers, and the low active dispersal ability of A. columbianus. However, the extent that each of those factors has on disrupting gene flow and explaining patterns of genetic variation in this species requires further research. The present study acts as a foundation for the development of future research on banana slug phylogenetics and population genetic structure.

This study presents a systematic revision of the suborder Astrophorina for the temperate Pacific coast of the United States and Canada. Major findings include a reduction in the number of species previously thought to range into the region from Japan; validation of most Geodia species erected by Lendenfeld (1910), which were later synonymized by de Laubenfels (1932); the formal description of 10 new species (Poecillastra alaskensis sp. nov., Vulcanella explorata sp. nov., Vulcanella rupta sp. nov., Stelletta cardenasi sp. nov., Stelletta nicolenya sp. nov., Stelletta limuwensis sp. nov., Dercitus (Stoeba) giveni sp. nov., Penares anyapax sp. nov., Penares foxi sp. nov., and Thenea diastra sp. nov.); and one new combination, Penares orientalis comb. nov. Extensive SCUBA-based collection efforts yielded new samples for 11 of the 26 species identified in the region, which enabled an integrative taxonomic approach that combined field photography, fresh material for DNA sequencing, and improved characterization of species ranges and morphological variability in previously described taxa. Illumina sequencing generated complete nuclear ribosomal haplotypes for five species, while Sanger sequencing of the 28S and cox1 loci placed 20 of the 26 species within molecular phylogenies. The use of very short "mini-barcode" amplicons also enabled sequence recovery from historic type specimens up to 137 years old. This study additionally reports the discovery of sponge grounds of abundant, large Geodia at diving depths in Southern California. Together, these results substantially advance our understanding of global astrophorid diversity and systematics, and the biogeography of sponge diversity in the Northeast Pacific. Note about species names: this pre-print is not intended to be a publication of the associated species names for the purposes of zoological nomenclature.

Understanding the evolutionary history of species within a geographic context is key to historical biogeography, as it reveals how geological and climatic changes shaped biodiversity. This is especially important in ecologically significant regions like the Amazon and Orinoco basins. Together, they host the worlds greatest freshwater fish diversity ([~]3,500 species), sharing a common but not yet fully understood evolutionary history. The gilded catfish (Brachyplatystoma rousseauxii), an ancient species widely distributed as a metapopulation in Neotropics, is an important model for studying past connectivity, divergence, and historical processes shaping fish diversity between these basins. This study analyzed the genetic structure, connectivity routes, and demographic history of B. rousseauxii using nuclear (microsatellite and ddRADseq) and mitochondrial DNA. Population structure analyses and coalescent models indicate that B. rousseauxii populations from the Orinoco and Amazon basins are genetically distinct, with no evidence of current gene flow. However, our results support the occurrence of a possible secondary contact event after the divergence, with the Boa Vista population retaining the genetic signal of this process. The ancestral population split occurred at the Rupununi Portal around 2.54 Ma (ddRAD) or 1.31 Ma (mtDNA). Then, the species colonized the Branco and Orinoco Rivers [~]1.90 Ma (ddRAD) or 0.6 Ma (mtDNA), rapidly expanding in the Orinoco (>1.3 or >0.29 Ma), while colonization of the Amazon from the Branco River was more recent ([&le;]1.0 or [&le;]0.15 Ma). Population expansion signal was detected in the Orinoco ([~]0.20 Ma), whereas the Amazon remained stable. Our findings suggest that the rise of the Vaupes Arch in the Late Miocene does not explain the observed genetic divergence. Likewise, the Casiquiare Canal and Japura-Guaviare headwaters are not connectivity routes between basins. Instead, the Rupununi Portal, including the recent capture of the Branco River by the Negro River, was the last point of connection and played a key role in shaping B. rousseauxiis distribution. These findings provide insights into Neotropical fish biogeography and the historical configuration of the Orinoco and Amazon basins.

Humans are widely regarded as unusually slow to develop, exhibiting prolonged childhood and extended dependence on caregivers. However, this view is based primarily on comparisons with other primates, leaving unresolved whether humans remain distinctive within the broader diversity of mammals. We addressed this question by situating human development in a comparative framework using gestation length, weaning age, and age at sexual maturity for both sexes across 462 mammalian species representing 25 orders. Each trait was examined both as an absolute value and as a proportion of the longest verified captive lifespan. In absolute terms, human developmental traits fell within the upper range of mammalian variation. When expressed relative to lifespan, however, gestation shifted toward the lower end of the distribution, whereas weaning age and sexual maturity occupied intermediate positions, indicating that human developmental timing largely follows general mammalian scaling patterns rather than representing a pronounced outlier. These findings suggest that key features of human dependency are better understood as extensions of broader evolutionary trends than as uniquely human life-history characteristics.

EU has reclassified the sika deer (Cervus nippon) as an undesirable invasive species based on reports that hybridization with the indigenous red deer (C. elaphus) may produce fertile offspring. Since sika-derived DNA previosuly introduced into the red deer population (introgression) cannot be removed, the crucial question is whether new (F1) hybridisation occur. To address this, we analysed the chromosomes in 56 sika and 22 red deer. All red deer had a chromosome number 2n=68. In contrast, the chromosome number in sika ranged from 64 to 67, due to the variable presence of two sika-specific Robertsonian translocations (ROB1,ROB2). In the free-ranging sika population in Jutland, >90% of the sika deer were homozygote for at least one of these ROBs, excluding that they could be F1-hybrids. Moreover, ROB2 was in Hardy-Weinberg equilibrium, further supporting the absence of gene flow between the two species. In contrast, ROB1 was in Hardy-Weinberg disequilibrium, suggesting negative fitness of heterozygotes, including potential F1-hybrids. In Jaegersborg Deer Park, the eight examined sika deer had the same genotype (absence of ROB1, homozygosity of ROB2), supporting that it is a founder population which may have been isolated for [~]100 years. Again, none of these can be F1-hybrids due to the homozygosity of ROB2. We conclude that F1-hybridisation between sika and red deer either does not occur or occur very rarely in Denmark. The study establish the Danish sika-populations as unique models for adressing important biological questions: What underlies the absence of hybridisation? Why are ROBs frequent in sika deer but not in the closely related red deer? How fast do new species/subspecies develop in isolated founder populations? Which factors determine, that some ROBs have little heterozygous effects, whereas others are selected against, with implications for the role of ROBs as genetic barriers promoting speciation, and for fertility problems in some human ROB carriers.