Supermatrix phylogeny resolves goby lineages and reveals unstable root of Gobiaria

The complete mitochondrial genome of a Biwa goby, Gymnogobius isaza (Tanaka, 1916)

We determined the complete mitochondrial DNA sequence of a Biwa goby, Gymnogobius isaza (Tanaka, 1916) using next-generation sequencing methods. The composition of its mitogenome is the same as that observed in most other vertebrates, comprising of 13 protein-coding genes, 22 tRNA genes, two rRNA genes, and two control regions. Our molecular phylogenetic analysis confirmed the close phylogenetic relationship between G. isaza and G. petschiliensis. This mitogenome information will be useful for distribution surveys using environmental DNA and the development of conservation strategies for this species.

A supermatrix phylogeny of the world's bees (Hymenoptera: Anthophila)

The increasing availability of large molecular phylogenies has provided new opportunities to study the evolution of species traits, their origins and diversification, and biogeography; yet there are limited attempts to synthesise existing phylogenetic information for major insect groups. Bees (Hymenoptera: Anthophila) are a large group of insect pollinators that have a worldwide distribution, and a wide variation in ecology, morphology, and life-history traits, including sociality. For these reasons, as well as their major economic importance as pollinators, numerous molecular phylogenetic studies of family and genus-level relationships have been published, providing an opportunity to assemble a bee 'tree-of-life'. We used publicly available genetic sequence data, including phylogenomic data, reconciled to a taxonomic database, to produce a concatenated supermatrix phylogeny for the Anthophila comprising 4,586 bee species, representing 23% of species and 82% of genera. At family, subfamily, and tribe levels, support for expected relationships was robust, but between and within some genera relationships remain uncertain. Within families, sampling of genera ranged from 67 to 100% but species coverage was lower (17-41%). Our phylogeny mostly reproduces the relationships found in recent phylogenomic studies with a few exceptions. We provide a summary of these differences and the current state of molecular data available and its gaps. We discuss the advantages and limitations of this bee supermatrix phylogeny (available online at beetreeoflife.org), which may enable new insights into long standing questions about evolutionary drivers in bees, and potentially insects more generally.

The complete mitochondrial genome of Acanthogobius lactipes and its phylogenetic analysis

Acanthogobius lactipes is a demersal, euryhaline fish belonging to the suborder Gobiodei. This study sequenced and described the complete mitochondrial genome of A. lactipes for the first time. The circular genome of A. lactipes is 16,592 bp in length and contains 13 protein-coding genes, 22 transfer RNA genes, two ribosomal RNA genes, and a control region. The overall A, C, G, and T contents were 27.78, 27.31, 17.52, and 27.39%, respectively. Based on the 13 protein-coding genes, the phylogenetic tree showed that A. lactipes formed a well-supported cluster with the genus Acanthogobius and rooted with other family Oxudercidae species.

Adhesion Behavior in Fish: From Structures to Applications

In nature, some fish can adhere tightly to the surface of stones, aquatic plants, and even other fish bodies. This adhesion behavior allows these fish to fix, eat, hide, and migrate in complex and variable aquatic environments. The adhesion function is realized by the special mouth and sucker tissue of fish. Inspired by adhesion fish, extensive research has recently been carried out. Therefore, this paper presents a brief overview to better explore underwater adhesion mechanisms and provide bionic applications. Firstly, the adhesion organs and structures of biological prototypes (e.g., clingfish, remora, Garra, suckermouth catfish, hill stream loach, and goby) are presented separately, and the underwater adhesion mechanisms are analyzed. Then, based on bionics, it is explained that the adhesion structures and components are designed and created for applications (e.g., flexible gripping adhesive discs and adhesive motion devices). Furthermore, we offer our perspectives on the limitations and future directions.

Assessing sequence heterogeneity in Chlorellaceae DNA barcode markers for phylogenetic inference

Phylogenetic inference is an important approach that allows the recovery of the evolutionary history and the origin of the Chlorellaceae species. Despite the species' potential for biofuel feedstock production, their high phenotypic plasticity and similar morphological structures among the species have muddled the taxonomy and identification of the Chlorellaceae species. This study aimed to decipher Chlorellaceae DNA barcode marker heterogeneity by examining the sequence divergence and genomic properties of 18S rRNA, ITS (ITS1-5.8S rRNA-ITS2-28S rRNA), and rbcL from 655 orthologous sequences of 64 species across 31 genera in the Chlorellaceae family. The study assessed the distinct evolutionary properties of the DNA markers that may have caused the discordance between individual trees in the phylogenetic inference using the Robinson-Foulds distance and the Shimodaira-Hasegawa test. Our findings suggest that using the supermatrix approach improves the congruency between trees by reducing stochastic error and increasing the confidence of the inferred Chlorellaceae phylogenetic tree. This study also found that the phylogenies inferred through the supermatrix approach might not always be well supported by all markers. The study highlights that assessing sequence heterogeneity prior to the phylogenetic inference could allow the approach to accommodate sequence evolutionary properties and support species identification from the most congruent phylogeny, which can better represent the evolution of Chlorellaceae species.

Diversification of the sleepers (Gobiiformes: Gobioidei: Eleotridae) and evolution of the root gobioid families

Eleotridae (sleepers) and five smaller families are the earliest diverging lineages within Gobioidei. Most inhabit freshwaters in and around the Indo-Pacific, but Eleotridae also includes species that have invaded the Neotropics as well as several inland radiations in the freshwaters of Australia, New Zealand, and New Guinea. Previous efforts to infer phylogeny of these families have been based on sets of mitochondrial or nuclear loci and have yielded uncertain resolution of clades within Eleotridae. We expand the taxon sampling of previous studies and use genomic data from nuclear ultraconserved elements (UCEs) to infer phylogeny, then calibrate the hypothesis with recently discovered fossils. Our hypothesis clarifies ambiguously resolved relationships, provides a timescale for divergences, and indicates the core crown Eleotridae diverged over a short period 24.3-26.3 Ma in the late Oligocene. Within Eleotridae, we evaluate diversification dynamics with BAMM and find evidence for an overall slowdown in diversification over the past 35 Ma, but with a sharp increase 3.5 Ma in the genus Mogurnda, a clade of brightly colored species found in the freshwaters of Australia and New Guinea.

Otoliths of Caspian gobies (Teleostei: Gobiidae): Morphological diversity and phylogenetic implications

Otoliths (ear stones) of the inner ears of teleost fishes, which develop independently from the skeleton and are functionally associated with hearing and the sense of equilibrium, have significantly contributed to contemporary understanding of teleost fish systematics and evolutionary diversity. The sagittal otolith is of particular interest, since it often possesses distinctive morphological features that differ significantly among species, and have been shown to be species- and genus-specific, making it an informative taxonomic tool for ichthyologists. The otolith morphology of the Caspian Sea gobiids has not been thoroughly studied yet, with data available for only a few species. The aim of the present paper is to examine the qualitative and quantitative taxonomic and phylogenetic information in the sagittal otoliths of these species. A total of 118 otoliths representing 30 gobiid species (including 53.5% of the Caspian gobiofauna) in three gobiid lineages (i.e., Gobius, Pomatoschistus, and Acanthogobius) and 11 genera (i.e., all Ponto-Caspian gobiid genera except Babka) were analysed at taxonomic levels using an integrated descriptive and morphometric approach. The results indicated high taxonomic efficiency of otolith morphology and morphometry at taxonomic levels for the Ponto-Caspian gobiids. Our qualitative and quantitative otolith data also (i) support the monophyly of neogobiin gobies, (ii) along with other morphological and ecological data, offer a new perspective on the systematics of Neogobius bathybius, (iii) suggest the reassignment of Hyrcanogobius bergi to the genus Knipowitschia, and (iv) question the phylogenetic integrity of the four phenotypic groups previously defined in the tadpole-goby genus Benthophilus; however, more studies are needed to complete these evaluations and confirm our otolith study findings.

Phylogenetic relationships of sleeper gobies (Eleotridae: Gobiiformes: Gobioidei), with comments on the position of the miniature genus Microphilypnus

Microphilypnus and Leptophilypnion are miniaturized genera within the family Eleotridae. The evolutionary relationships among these taxa are still poorly understood, and molecular analyses are restricted to mitochondrial genes, which have not been conclusive. We compiled both mitochondrial and nuclear genes to study the phylogenetic position of Microphilypnus and the evolutionary history and relationships of eleotrids. We propose that Microphilypnus and Leptophilypnus (a non-miniature genus) are not sister groups as suggested by previous studies, but rather separate lineages that arose in the early Eocene, with Leptophilypnus recovered as a sister group to the other analyzed eleotrids. In fact, Microphilypnus is currently associated with the Neotropical clade Guavina/Dormitator/Gobiomorus. We also identified a well-supported clade that indicated Gobiomorus and Hemieleotris as paraphyletic groups, besides a close relationship among Calumia godeffroyi, Bunaka gyrinoides, Eleotris and Erotelis species. This is the first comprehensive report about the evolutionary relationships in members of the family Eleotridae, including multiloci and multispecies approaches. Therefore, we provided new insights about the phylogenetic position of some taxa absent in previous studies, such as the miniature genus Microphilypnus and a recently described species of Eleotris from South America.

One size does not fit all: Variation in anatomical traits associated with emersion behavior in mudskippers (Gobiidae: Oxudercinae)

Life histories involving transitions between differing habitats (i.e., aquatic to terrestrial or marine to freshwater) require numerous anatomical, physiological, and behavioral changes. Often, the traits associated with these changes are thought to come in suites, but all traits thought to be associated with particular life histories may not be required. While some traits are found in all species with a particular habitat transition, a grab bag approach may apply to other traits in that any trait may be sufficient for successful habitat transitions. We examine patterns of morphological traits associated with prolonged emersion in mudskipper, an amphibious fishes clade, where prolonged emersion appears twice. We test the evolutionary history of multiple characteristics associated with cutaneous respiration. We find most traits thought to be key for prolonged emersion show no phylogenetic signal and no tight correlation with prolonged emersion. Such traits appear in species with prolonged emersion but also non-emerging species. Only capillary density, which, when increased, allows for increased oxygen absorption, shows strong phylogenetic signal and correlation with prolonged emersion. Further experimental, functional genomics, and observational studies are needed to fully understand the mechanisms associated with each of these traits. With respect to traits associated with other particular behaviors, a comparative framework can be helpful in identifying evolutionary correlates.

Comprehensive taxon sampling and vetted fossils help clarify the time tree of shorebirds (Aves, Charadriiformes)

Shorebirds (Charadriiformes) are a globally distributed clade of modern birds and, due to their ecological and morphological disparity, a frequent subject of comparative studies. While molecular phylogenies have been key to establishing the suprafamilial backbone of the charadriiform tree, a number of relationships at both deep and shallow taxonomic levels remain poorly resolved. The timescale of shorebird evolution also remains uncertain as a result of extensive disagreements among the published divergence dating studies, stemming largely from different choices of fossil calibrations. Here, we present the most comprehensive non-supertree phylogeny of shorebirds to date, based on a total-evidence dataset comprising 353 ingroup taxa (90% of all extant or recently extinct species), 27 loci (15 mitochondrial and 12 nuclear), and 69 morphological characters. We further clarify the timeline of charadriiform evolution by time-scaling this phylogeny using a set of 14 up-to-date and thoroughly vetted fossil calibrations. In addition, we assemble a taxonomically restricted 100-locus dataset specifically designed to resolve outstanding problems in higher-level charadriiform phylogeny. In terms of tree topology, our results are largely congruent with previous studies but indicate that some of the conflicts among earlier analyses reflect a genuine signal of pervasive gene tree discordance. Monophyly of the plovers (Charadriidae), the position of the ibisbill (Ibidorhyncha), and the relationships among the five subfamilies of the gulls (Laridae) could not be resolved even with greatly increased locus and taxon sampling. Moreover, several localized regions of uncertainty persist in shallower parts of the tree, including the interrelationships of the true auks (Alcinae) and anarhynchine plovers. Our node-dating and macroevolutionary rate analyses find support for a Paleocene origin of crown-group shorebirds, as well as exceptionally rapid recent radiations of Old World oystercatchers (Haematopodidae) and select genera of gulls. Our study underscores the challenges involved in estimating a comprehensively sampled and carefully calibrated time tree for a diverse avian clade, and highlights areas in need of further research.

An integrative phylogenetic approach for inferring relationships of fossil gobioids (Teleostei: Gobiiformes)

The suborder Gobioidei is among the most diverse groups of vertebrates, comprising about 2310 species. In the fossil record gobioids date back to the early Eocene (c. 50 m.y. ago), and a considerable increase in numbers of described species is evident since the middle Miocene (c. 16 m.y. ago). About 40 skeleton-based gobioid species and > 100 otolith-based species have been described until to date. However, assignment of a fossil gobioid species to specific families has often remained tentative, even if well preserved complete specimens are available. The reasons are that synapomorphies that can be recognized in a fossil skeleton are rare (or absent) and that no phylogenetic framework applicable to gobioid fossils exists. Here we aim to overcome this problem by developing a phylogenetic total evidence framework that is suitable to place a fossil skeleton-based gobioid at family level. Using both literature and newly collected data we assembled a morphological character matrix (48 characters) for 29 extant species, representing all extant gobioid families, and ten fossil gobioid species, and we compiled a multi-gene concatenated alignment (supermatrix; 6271 bp) of published molecular sequence data for the extant species. Bayesian and Maximum Parsimony analyses revealed that our selection of extant species was sufficient to achieve a molecular ‘backbone’ that fully conforms to previous molecular work. Our data revealed that inclusion of all fossil species simultaneously produced very poorly resolved trees, even for some extant taxa. In contrast, addition of a single fossil species to the total evidence data set of the extant species provided new insight in its possible placement at family level, especially in a Bayesian framework. Five out of the ten fossil species were recovered in the same family as had been suggested in previous works based on comparative morphology. The remaining five fossil species had hitherto been left as family incertae sedis. Now, based on our phylogenetic framework, new and mostly well supported hypotheses to which clades they could belong can be presented. We conclude that the total evidence framework presented here will be beneficial for all future work dealing with the phylogenetic placement of a fossil skeleton-based gobioid and thus will help to improve our understanding of the evolutionary history of these fascinating fishes. Moreover, our data highlight that increased sampling of fossil taxa in a total-evidence context is not universally beneficial, as might be expected, but strongly depends on the study group and peculiarities of the morphological data.

Patterns of Phenotypic Evolution Associated with Marine/Freshwater Transitions in Fishes

Evolutionary transitions between marine and freshwater ecosystems have occurred repeatedly throughout the phylogenetic history of fishes. The theory of ecological opportunity predicts that lineages that colonize species-poor regions will have greater potential for phenotypic diversification than lineages invading species-rich regions. Thus, transitions between marine and freshwaters may promote phenotypic diversification in trans-marine/freshwater fish clades. We used phylogenetic comparative methods to analyze body size data in nine major fish clades that have crossed the marine/freshwater boundary. We explored how habitat transitions, ecological opportunity, and community interactions influenced patterns of phenotypic diversity. Our analyses indicated that transitions between marine and freshwater habitats did not drive body size evolution, and there are few differences in body size between marine and freshwater lineages. We found that body size disparity in freshwater lineages is not correlated with the number of independent transitions to freshwaters. We found a positive correlation between body size disparity and overall species richness of a given area, and a negative correlation between body size disparity and diversity of closely related species. Our results indicate that the diversity of incumbent freshwater species does not restrict phenotypic diversification, but the diversity of closely related taxa can limit body size diversification. Ecological opportunity arising from colonization of novel habitats does not seem to have a major effect in the trajectory of body size evolution in trans-marine/freshwater clades. Moreover, competition with closely related taxa in freshwaters has a greater effect than competition with distantly related incumbent species.

Diversification Rate is Associated with Rate of Molecular Evolution in Ray-Finned Fish (Actinopterygii)

Understanding the factors that drive diversification of taxa across the tree of life is a key focus of macroevolutionary research. While the effects of life history, ecology, climate and geography on diversity have been studied for many taxa, the relationship between molecular evolution and diversification has received less attention. However, correlations between rates of molecular evolution and diversification rate have been detected in a range of taxa, including reptiles, plants and birds. A correlation between rates of molecular evolution and diversification rate is a prediction of several evolutionary theories, including the evolutionary speed hypothesis which links variation in mutation rates to differences in speciation rates. If it is widespread, such correlations could also have significant practical impacts, if they are not adequately accounted for in phylogenetic inference of evolutionary rates and timescales. Ray-finned fish (Actinopterygii) offer a prime target to test for this relationship due to their extreme variation in clade size suggesting a wide range of diversification rates. We employ both a sister-pairs approach and a whole-tree approach to test for correlations between substitution rate and net diversification. We also collect life history and ecological trait data and account for potential confounding factors including body size, latitude, max depth and reef association. We find evidence to support a relationship between diversification and synonymous rates of nuclear evolution across two published backbone phylogenies, as well as weak evidence for a relationship between mitochondrial nonsynonymous rates and diversification at the genus level.

Phylogenetics And The Evolution Of Terrestriality In Mudskippers (Gobiidae: Oxudercinae)

The initial vertebrate conquest of land by stegocephalians (Sarcopterygia) allowed access to new resources and exploitation of untapped niches precipitating a major phylogenetic diversification. However, a paucity of fossils has left considerable uncertainties about phylogenetic relationships and the eco-morphological stages in this key transition in Earth history. Among extant actinopterygians, three genera of mudskippers (Gobiidae: Oxudercinae), Boleophthalmus, Periophthalmus and Periophthalmodon are the most terrestrialized, with vertebral, appendicular, locomotory, respiratory, and epithelial specializations enabling overland excursions up to 14 hours. Unlike early stegocephalians, the ecologies and morphologies of the 45 species of oxudercines are well known, making them viable analogs for the initial vertebrate conquest of land. Nevertheless, they have received little phylogenetic attention. We compiled the largest molecular dataset to date, with 29 oxudercine species, and 5 nuclear and mitochondrial loci. Phylogenetic and comparative analyses revealed strong support for two independent terrestrial transitions, and a complex suit of ecomorphological forms in estuarine environments. Furthermore, neither Oxudercinae nor their presumed sister-group the eel gobies (Amblyopinae, a group of elongated gobies) were monophyletic with respect to each other, requiring a merging of these two subfamilies and revealing an expansion of phenotypic variation within the "mudskipper" clade. We did not find support for the expected linear model of ecomorphological and locomotory transition from fully aquatic, to mudswimming, to pectoral-aided mudswimming, to lobe-finned terrestrial locomotion proposed by earlier morphological studies. This high degree of convergent or parallel transitions to terrestriality, and apparent divergent directions of estuarine adaptation, promises even greater potential for this clade to illuminate the conquest of land. Future work should focus on these less-studied species with "transitional" and other mud-habitat specializations to fully resolve the dynamics of this diversification.

Complete mitochondrial genomes of two sand diver species (Perciformes, Trichonotidae): novel gene orders and phylogenetic position within Gobiiformes

The complete mitochondrial genome sequences of two species of the family Trichonotidae, Trichonotus elegans (Shimada and Yoshino 1984) and Trichonotus filamentosus (Steindachner 1867), were determined using a polymerase chain reaction-based method. The genomes ranged from 16,517 to 17,235 bp in length and included 37 genes (13 protein-coding genes, 22 transfer RNA genes, and 2 ribosomal RNA genes) and two non-coding regions (control region and origin of the light strand replication) as in other vertebrates. However, they shared a unique gene order among vertebrates with multiple gene switching and insertions. Phylogenetic analysis showed that Trichonotidae and Apogonidae are sister groups, which together with Kurtidae are placed as a closely related clade of Gobioidei. These results would be useful for analyzing the evolutionary relationships of Gobiiformes and the evolutionary study of fish mitogenomes.

Gonad morphology of Rhyacichthys aspro (Valenciennes, 1837), and the diagnostic reproductive morphology of gobioid fishes

Rhyacichthys aspro is a “basal” taxon in the Suborder Gobioidei of the teleost order Gobiiformes. We provide detailed descriptions of the reproductive morphology of adult males and females to assess the diagnostic reproductive morphological characters of this speciose clade of bony fishes. Female R. aspro are asynchronous spawners: they are able to spawn more than once in a breeding season. Oocytes are inferred to have short attachment filaments. A conspicuous feature of the external anatomy of the reproductive system (RSy) of female R. aspro is an ornate fimbriate pad upon which the urogenital papilla rests. The male reproductive system is characterized by an intralobar collection system in both the testicular and secretory lobes, termed the “sperm‐collecting canal” and “milt‐collecting canal,” respectively. These may provide additional storage for sperm and milt. The spermatogenic lobe, or testis, is that portion of the male gobioid RSy comprising seminiferous lobules and separate from other RSy components. The secretory lobe is that portion of the male gobioid reproductive system that consists of secretory lobules and is separated from other components of the male RSy. The secretory lobe has also been called, in English, the sperm‐duct gland, accessory gonadal structure, or seminal vesicle, and is endorsed as a synapomorphy of gobioid fishes.

Correlation between acoustic divergence and phylogenetic distance in soniferous European gobiids (Gobiidae; Gobius lineage)

In fish, species identity can be encoded by sounds, which have been thoroughly investigated in European gobiids (Gobiidae, Gobius lineage). Recent evolutionary studies suggest that deterministic and/or stochastic forces could generate acoustic differences among related animal species, though this has not been investigated in any teleost group to date. In the present comparative study, we analysed the sounds from nine soniferous gobiids and quantitatively assessed their acoustic variability. Our interspecific acoustic study, incorporating for the first time the representative acoustic signals from the majority of soniferous gobiids, suggested that their sounds are truly species-specific (92% of sounds correctly classified into exact species) and each taxon possesses a unique set of spectro-temporal variables. In addition, we reconstructed phylogenetic relationships from a concatenated molecular dataset consisting of multiple molecular markers to track the evolution of acoustic signals in soniferous gobiids. The results of this study indicated that the genus Padogobius is polyphyletic, since P. nigricans was nested within the Ponto-Caspian clade, while the congeneric P. bonelli turned out to be a sister taxon to the remaining investigated soniferous species. Lastly, by extracting the acoustic and genetic distance matrices, sound variability and genetic distance were correlated for the first time to assess whether sound evolution follows a similar phylogenetic pattern. The positive correlation between the sound variability and genetic distance obtained here emphasizes that certain acoustic features from representative sounds could carry the phylogenetic signal in soniferous gobiids. Our study was the first attempt to evaluate the mutual relationship between acoustic variation and genetic divergence in any teleost fish.

Cryptocentrus steinhardti (Actinopterygii; Gobiidae): a new species of shrimp-goby, and a new invasive to the Mediterranean Sea

A new species of shrimp-goby was collected at depths of 60–80 m off the southern Israeli Mediterranean coast. A unique ‘DNA barcoding’ signature (mtDNA COI and Cytb) revealed that it differs from any other previously bar-coded goby species clustered phylogenetically with the shrimp-gobies group, in which Cryptocentrus is the most speciose genus. A morphological study supported the assignment of the fish to Cryptocentrus and differentiated the new species from its congeners. The species is described here as Cryptocentrus steinhardti n. sp. However, the present phylogenetic analysis demonstrates a paraphyly of Cryptocentrus and emphasizes the need for revision of the genus based on integrating morphological and genetic characteristics. This finding constitutes the third record of an invasive shrimp goby in the Mediterranean Sea. An intriguing ecological issue arises regarding the possible formation of a fish-shrimp symbiosis in a newly invaded territory. Describing an alien tropical species in the Mediterranean prior to its discovery in native distribution is an unusual event, although not the first such case. Several similar examples are provided in the present article.

Bendy to the bone: Links between vertebral morphology and waterfall climbing in amphidromous gobioid fishes

Locomotor force production imposes strong demands on organismal form. Thus, the evolution of novel locomotor modes is often associated with morphological adaptations that help to meet those demands. In the goby lineage of fishes, most species are marine and use their fused pelvic fins to facilitate station holding in wave-swept environments. However, several groups of gobies have evolved an amphidromous lifecycle, in which larvae develop in the ocean but juveniles migrate to freshwater for their adult phase. In many of these species, the pelvic fins have been co-opted to aid in climbing waterfalls during upstream migrations to adult habitats. During horizontal swimming, forces are produced by axial musculature pulling on the vertebral column. However, during vertical climbing, gravity also exerts forces along the length of the vertebral column. In this study, we searched for novel aspects of vertebral column form that might be associated with the distinctive locomotor strategies of climbing gobies. We predicted that stiffness would vary along the length of the vertebral column due to competing demands for stability of the suction disk anteriorly and flexibility for axial thrust production posteriorly. We also predicted that derived, climbing goby species would require stiffer backbones to aid in vertical thrust production compared to non-climbing species. To test these predictions, we used microcomputed tomography scans to compare vertebral anatomy (centrum length, centrum width, and intervertebral space) along the vertebral column for five gobioid species that differ in climbing ability. Our results support our second prediction, that gobies are more flexible in the posterior portion of the body. However, the main variation in vertebral column form associated with climbing ability was the presence of larger intervertebral spaces in Sicyopterus stimpsoni, a species that uses a distinctive inching behavior to climb. These results build on past kinematic studies of goby climbing performance and lend insights into how the underlying vertebral structure of these fishes may enable their novel locomotion.

Diversification and colonization processes in Gobioidei predicted based on mitochondrial 12S rRNA with focusing on Oxudercidae

Gobioidei is one of the largest vertebrate taxa with over 2000 species observed around the globe. The largest group in Gobioidei is gobies that had been classified as one family, Gobiidae, based on morphological features. Molecular phylogenetic studies revealed that gobies consisted of two monophyletic families, Gobiidae and Oxudercidae, in which 19 lineages have been proposed, despite some claims arisen about the relationship among these lineages or species. We analyzed 58 Gobioidei species, including 45 East Asian oxudercids, based on 12S rRNA sequences to reconstruct the spatiotemporal diversification history of gobies. Our analysis yielded the results compatible with the previous reports in a large framework. The common ancestor of Gobiidae and Oxudercidae were estimated to appear at 38.66 Mya. Genus-level splits occurred in Gobiidae and Oxudercidae predominantly at Miocene and late Miocene to early Pleistocene, respectively. Gobies have likely originated in many parts of the northern and western Pacific Ocean, of which a large proportion of Oxudercidae have adapted to various environments in the North Pacific.