Paralog switching facilitates diadromy: ontogenetic, microevolutionary and macroevolutionary evidence.

Identifying how the demands of migration are met at the level of gene expression is critical for understanding migratory physiology and can potentially reveal how migratory forms evolve from nonmigratory forms and vice versa. Among fishes, migration between freshwater and seawater (diadromy) requires considerable osmoregulatory adjustments, powered by the ion pump Na+, K+-ATPase (NKA) in the gills. Paralogs of the catalytic α-subunit of the pump (NKA α1a and α1b) are reciprocally upregulated in fresh- and seawater, a response known as paralog-switching, in gills of some diadromous species. We tested ontogenetic changes in NKA α-subunit paralog expression patterns, comparing pre-migrant and migrant alewife (Alosa pseudoharengus) sampled in their natal freshwater environment and after 24 h in seawater. In comparison to pre-migrants, juvenile out-migrants exhibited stronger paralog switching via greater downregulation of NKA α1a in seawater. We also tested microevolutionary changes in the response, exposing juvenile diadromous and landlocked alewife to freshwater (0 ppt) and seawater (30 ppt) for 2, 5, and 15 days. Diadromous and landlocked alewife exhibited salinity-dependent paralog switching, but levels of NKA α1b transcription were higher and the decrease in NKA α1a was greater after seawater exposure in diadromous alewife. Finally, we placed alewife α-subunit NKA paralogs in a macroevolutionary context. Molecular phylogenies show alewife paralogs originated independently of paralogs in salmonids and other teleosts. This study demonstrated that NKA paralog switching is tied to halohabitat profile and that duplications of the NKA gene provided the substrate for multiple, independent molecular solutions that support a diadromous life history.

Coevolution between MHC Class I and Antigen-Processing Genes in Salamanders.

Proteins encoded by antigen-processing genes (APGs) provide major histocompatibility complex (MHC) class I (MHC-I) with antigenic peptides. In mammals, polymorphic multigenic MHC-I family is served by monomorphic APGs, whereas in certain nonmammalian species both MHC-I and APGs are polymorphic and coevolve within stable haplotypes. Coevolution was suggested as an ancestral gnathostome feature, presumably enabling only a single highly expressed classical MHC-I gene. In this view coevolution, while optimizing some aspects of adaptive immunity, would also limit its flexibility by preventing the expansion of classical MHC-I into a multigene family. However, some nonmammalian taxa, such as salamanders, have multiple highly expressed MHC-I genes, suggesting either that coevolution is relaxed or that it does not prevent the establishment of multigene MHC-I. To distinguish between these two alternatives, we use salamanders (30 species from 16 genera representing six families) to test, within a comparative framework, a major prediction of the coevolution hypothesis: the positive correlation between MHC-I and APG diversity. We found that MHC-I diversity explained both within-individual and species-wide diversity of two APGs, TAP1 and TAP2, supporting their coevolution with MHC-I, whereas no consistent effect was detected for the other three APGs (PSMB8, PSMB9, and TAPBP). Our results imply that although coevolution occurs in salamanders, it does not preclude the expansion of the MHC-I gene family. Contrary to the previous suggestions, nonmammalian vertebrates thus may be able to accommodate diverse selection pressures with flexibility granted by rapid expansion or contraction of the MHC-I family, while retaining the benefits of coevolution between MHC-I and TAPs.

An experimental test of Lanchester's models of combat in the neotropical termite Nasutitermes corniger (Blattodea: Termitidae).

Lanchester's models of combat have been invoked to explain the mechanics of group fighting in social animals. Specifically, Lanchester's square law posits that the fighting ability of the group is proportional to the square of the number of combatants. Although used to explain a variety of ecological phenomena, the models have not been thoroughly tested. We tested the Lanchester models using group battles between colonies of the termite Nasutitermes corniger. Our main goals were to determine if mortality rates fit the Lanchester models, and if so, whether the behavioural mechanisms underlying a group's success match those used in deriving the model. We initiated battles between pairs of colonies with different ratios of fighters and recorded deaths over time. We found that the numerically larger army has an advantage, but that the advantage is not as pronounced as predicted by Lanchester's square law. We also video-recorded battles to analyse individual behaviour, which did not support the mechanisms invoked by Lanchester. Instead, the killing power of an individual is increased by the presence of nest-mates, giving the larger group a disproportionate advantage. Although the behavioural mechanisms leading to the advantage may differ, our results still support some of the proposed ecological phenomena.

Out from under the wing: reconceptualizing the insect wing gene regulatory network as a versatile, general module for body-wall lobes in arthropods.

Body plan evolution often occurs through the differentiation of serially homologous body parts, particularly in the evolution of arthropod body plans. Recently, homeotic transformations resulting from experimental manipulation of gene expression, along with comparative data on the expression and function of genes in the wing regulatory network, have provided a new perspective on an old question in insect evolution: how did the insect wing evolve? We investigated the metamorphic roles of a suite of 10 wing- and body-wall-related genes in a hemimetabolous insect, Oncopeltus fasciatus. Our results indicate that genes involved in wing development in O. fasciatus play similar roles in the development of adult body-wall flattened cuticular evaginations. We found extensive functional similarity between the development of wings and other bilayered evaginations of the body wall. Overall, our results support the existence of a versatile development module for building bilayered cuticular epithelial structures that pre-dates the evolutionary origin of wings. We explore the consequences of reconceptualizing the canonical wing-patterning network as a bilayered body-wall patterning network, including consequences for long-standing debates about wing homology, the origin of wings and the origin of novel bilayered body-wall structures. We conclude by presenting three testable predictions that result from this reconceptualization.

Developmental temperature influences color polymorphism but not hatchling size in a woodland salamander.

Phenotypic plasticity can be an important adaptive response to climate change, particularly for dispersal-limited species. Temperature frequently alters developmental and phenotypic traits including morphology, behavior, and reproductive cycles. We often lack crucial information about if and how thermal conditions during development will interact with genetic responses and facilitate persistence or adaptation under climate change. Polymorphic species offer an ideal test for this, as alternative morphs often confer differential adaptive advantages. However, few studies have examined the effects of incubation temperature on color expression or development in polymorphic taxa. Here we test if developmental temperature mediates morph frequency in the polymorphic salamander Plethodon cinereus. Although previous research suggests geographic variation in morph proportions results from differential climate adaptation, it remains unknown if plasticity also contributes to this variation. We used a split-clutch common garden experiment to determine the effects of developmental temperature on the color and development of P. cinereus. Our results indicate developmental temperature affects coloration in P. cinereus, either via plasticity or differential mortality, with eggs incubated at warmer temperatures yielding a higher proportion of unstriped individuals than those from cooler temperatures. This temperature response may contribute to the spatial variation in morph frequencies in natural populations. Surprisingly, we found neither temperature nor egg size affected hatchling size. Our study provides important insights into the potential for climate-induced responses to preserve diversity in dispersal-limited species, like P. cinereus, and enable time for adaptive evolution.

The effects of inference method, population sampling, and gene sampling on species tree inferences: an empirical study in slender salamanders (Plethodontidae: Batrachoseps).

Species tree methods are now widely used to infer the relationships among species from multilocus data sets. Many methods have been developed, which differ in whether gene and species trees are estimated simultaneously or sequentially, and in how gene trees are used to infer the species tree. While these methods perform well on simulated data, less is known about what impacts their performance on empirical data. We used a data set including five nuclear genes and one mitochondrial gene for 22 species of Batrachoseps to compare the effects of method of analysis, within-species sampling and gene sampling on species tree inferences. For this data set, the choice of inference method had the largest effect on the species tree topology. Exclusion of individual loci had large effects in *BEAST and STEM, but not in MP-EST. Different loci carried the greatest leverage in these different methods, showing that the causes of their disproportionate effects differ. Even though substantial information was present in the nuclear loci, the mitochondrial gene dominated the *BEAST species tree. This leverage is inherent to the mtDNA locus and results from its high variation and lower assumed ploidy. This mtDNA leverage may be problematic when mtDNA has undergone introgression, as is likely in this data set. By contrast, the leverage of RAG1 in STEM analyses does not reflect properties inherent to the locus, but rather results from a gene tree that is strongly discordant with all others, and is best explained by introgression between distantly related species. Within-species sampling was also important, especially in *BEAST analyses, as shown by differences in tree topology across 100 subsampled data sets. Despite the sensitivity of the species tree methods to multiple factors, five species groups, the relationships among these, and some relationships within them, are generally consistently resolved for Batrachoseps.

Hox genes require homothorax and extradenticle for body wall identity specification but not for appendage identity specification during metamorphosis of Tribolium castaneum.

The establishment of segment identity is a key developmental process that allows for divergence along the anteroposterior body axis in arthropods. In Drosophila, the identity of a segment is determined by the complement of Hox genes it expresses. In many contexts, Hox transcription factors require the protein products of extradenticle (exd) and homothorax (hth) as cofactors to perform their identity specification functions. In holometabolous insects, segment identity may be specified twice, during embryogenesis and metamorphosis. To glean insight into the relationship between embryonic and metamorphic segmental identity specification, we have compared these processes in the flour beetle Tribolium castaneum, which develops ventral appendages during embryogenesis that later metamorphose into adult appendages with distinct morphologies. At metamorphosis, comparisons of RNAi phenotypes indicate that Hox genes function jointly with Tc-hth and Tc-exd to specify several region-specific aspects of the adult body wall. On the other hand, Hox genes specify appendage identities along the anteroposterior axis independently of Tc-hth/Tc-exd and Tc-hth/Tc-exd specify proximal vs. distal identity within appendages independently of Hox genes during this stage. During embryogenesis, Tc-hth and Tc-exd play a broad role in the segmentation process and are required for specification of body wall identities in the thorax; however, contrasting with results from other species, we did not obtain homeotic transformations of embryonic appendages in response to Tc-hth or Tc-exd RNAi. In general, the homeotic effects of interference with the function of Hox genes and Tc-hth/Tc-exd during metamorphosis did not match predictions based on embryonic roles of these genes. Comparing metamorphic patterning in T. castaneum to embryonic and post-embryonic development in hemimetabolous insects suggests that holometabolous metamorphosis combines patterning processes of both late embryogenesis and metamorphosis of the hemimetabolous life cycle.

Metamorphic labral axis patterning in the beetle Tribolium castaneum requires multiple upstream, but few downstream, genes in the appendage patterning network.

The arthropod labrum is an anterior appendage-like structure that forms the dorsal side of the preoral cavity. Conflicting interpretations of fossil, nervous system, and developmental data have led to a proliferation of scenarios for labral evolution. The best supported hypothesis is that the labrum is a novel structure that shares development with appendages as a result of co-option. Here, we use RNA interference in the red flour beetle Tribolium castaneum to compare metamorphic patterning of the labrum to previously published data on ventral appendage patterning. As expected under the co-option hypothesis, depletion of several genes resulted in similar defects in the labrum and ventral appendages. These include proximal deletions and proximal-to-distal transformations resulting from depletion of the leg gap genes homothorax and extradenticle, large-scale deletions resulting from depletion of the leg gap gene Distal-less, and smaller distal deletions resulting from knockdown of the EGF ligand Keren. However, depletion of dachshund and many of the genes that function downstream of the leg gap genes in the ventral appendages had either subtle or no effects on labral axis patterning. This pattern of partial similarity suggests that upstream genes act through different downstream targets in the labrum. We also discovered that many appendage axis patterning genes have roles in patterning the epipharyngeal sensillum array, suggesting that they have become integrated into a novel regulatory network. These genes include Notch, Delta, and decapentaplegic, and the transcription factors abrupt, bric à brac, homothorax, extradenticle and the paralogs apterous a and apterous b.

Unveiling the Genetic Blueprint of a Desert Scorpion: A Chromosome-level Genome of Hadrurus arizonensis Provides the First Reference for Parvorder Iurida.

Over 400 million years old, scorpions represent an ancient group of arachnids and one of the first animals to adapt to life on land. Presently, the lack of available genomes within scorpions hinders research on their evolution. This study leverages ultralong nanopore sequencing and Pore-C to generate the first chromosome-level assembly and annotation for the desert hairy scorpion, Hadrurus arizonensis. The assembled genome is 2.23 Gb in size with an N50 of 280 Mb. Pore-C scaffolding reoriented 99.6% of bases into nine chromosomes and BUSCO identified 998 (98.6%) complete arthropod single copy orthologs. Repetitive elements represent 54.69% of the assembled bases, including 872,874 (29.39%) LINE elements. A total of 18,996 protein-coding genes and 75,256 transcripts were predicted, and extracted protein sequences yielded a BUSCO score of 97.2%. This is the first genome assembled and annotated within the family Hadruridae, representing a crucial resource for closing gaps in genomic knowledge of scorpions, resolving arachnid phylogeny, and advancing studies in comparative and functional genomics.

Distal-less and dachshund pattern both plesiomorphic and apomorphic structures in chelicerates: RNA interference in the harvestman Phalangium opilio (Opiliones).

The discovery of genetic mechanisms that can transform a morphological structure from a plesiomorphic (=primitive) state to an apomorphic (=derived) one is a cardinal objective of evolutionary developmental biology. However, this objective is often impeded for many lineages of interest by limitations in taxonomic sampling, genomic resources, or functional genetic methods. In order to investigate the evolution of appendage morphology within Chelicerata, the putative sister group of the remaining arthropods, we developed an RNA interference (RNAi) protocol for the harvestman Phalangium opilio. We silenced the leg gap genes Distal-less (Dll) and dachshund (dac) in the harvestman via zygotic injections of double-stranded RNA (dsRNA), and used in situ hybridization to confirm RNAi efficacy. Consistent with the conserved roles of these genes in patterning the proximo-distal axis of arthropod appendages, we observed that embryos injected with Dll dsRNA lacked distal parts of appendages and appendage-like structures, such as the labrum, the chelicerae, the pedipalps, and the walking legs, whereas embryos injected with dac dsRNA lacked the medial podomeres femur and patella in the pedipalps and walking legs. In addition, we detected a role for these genes in patterning structures that do not occur in well-established chelicerate models (spiders and mites). Dll RNAi additionally results in loss of the preoral chamber, which is formed from pedipalpal and leg coxapophyses, and the ocularium, a dorsal outgrowth bearing the eyes. In one case, we observed that an embryo injected with dac dsRNA lacked the proximal segment of the chelicera, a plesiomorphic podomere that expresses dac in wild-type embryos. This may support the hypothesis that loss of the cheliceral dac domain underlies the transition to the two-segmented chelicera of derived arachnids.

Molecular systematics of Batrachoseps (Caudata, Plethodontidae) in southern California and Baja California: mitochondrial-nuclear DNA discordance and the evolutionary history of B. major.

Inferences about species boundaries and evolutionary history are often complicated by discordance between datasets. In recent times, considerable effort has been devoted to understanding the causes of discordance between the patterns of genetic variation and structure shown by different unlinked molecular markers. The genus Batrachoseps (Caudata, Plethodontidae), the most diverse group of salamanders in western North America, is characterized by limited morphological variation and discordance between molecular datasets, making it a challenging group for taxonomists but also a good model to test newly developed analytical methods to sort out possible sources of discordance. In this study, we present a comprehensive assessment of the evolutionary history of B. major, one of the most widespread species in the genus, based on extensive sampling and phylogenetic and coalescent analyses of data from mitochondrial and nuclear markers. We found non-monophyly of mtDNA in B. major, with two lineages (northern and southern) that are more closely related to other species in the genus than to each other, but this division was not apparent in nuclear DNA. Despite non-monophyly in gene trees, species tree analyses recovered a sister group relationship between the two lineages of B. major, and coalescent simulations suggested that there is no need to invoke gene flow to account for the discordance across gene trees. The possibility that these two lineages represent sister, cryptic taxa, is discussed in the context of Bayesian methods of species/lineage delineation. Contrary to prior expectations, B. major has experienced extensive diversification on the Baja California Peninsula, where four endemic lineages have persisted for at least 4 million years.

Mechanical reproductive isolation facilitates parallel speciation in western North American scincid lizards.

Mechanical reproductive barriers have been dismissed as a major driver of animal speciation, yet the extent to which such barriers cause reproductive isolation in most animal groups is largely unknown and rarely tested. In this study, we used hierarchical Bayesian modeling of mate compatibility experiments to show that body size divergence in lizards of the Plestiodon skiltonianus complex contributes to reproductive isolation in at least three ways: males preferably court females that are more similar in size, females reject males that are highly divergent in size, and the size difference of a male and female in copula constrains the ability to align the genitalia for intromission. We used a predictive model to estimate the contributions of behavioral and mechanical barriers to reproductive isolation between populations with differing degrees of size divergence. This model shows that the mechanical barrier is more important than behavioral barriers at small and intermediate degrees of size divergence, suggesting that it acts earlier during speciation when body morphology is more similar between diverging lineages. Given that correlated divergence in size and ecology is common in animals, similar constraints imposed by the geometry of the mating posture may apply to a variety of major animal lineages and merit further attention in speciation research.

Something old, something new, something borrowed, something red: the origin of ecologically relevant novelties in Hemiptera.

Comparative transcriptomics, applied in an evolutionary context, has transformed the possibilities for studying phenotypic evolution in non-model taxa. We review recent discoveries about the development of novel, ecologically relevant phenotypes in hemipteran insects. These discoveries highlight the diverse genomic substrates of novelty: 'something old', when novelty results from changes in the regulation of existing genes or gene duplication; 'something new', wherein lineage-restricted genes contribute to the evolution of new phenotypes; and 'something borrowed', showcasing contributions of horizontal gene transfer to the evolution of novelty, including carotenoid synthesis (resulting in 'something red'). These findings show the power and flexibility of comparative transcriptomic approaches for expanding beyond the 'toolkit' model for the evolution of development. We conclude by raising questions about the relationship between new genes and new traits and outlining a research framework for answering them in Hemiptera.

Molecular Evolution of Antigen-Processing Genes in Salamanders: Do They Coevolve with MHC Class I Genes?

Proteins encoded by antigen-processing genes (APGs) prepare antigens for presentation by the major histocompatibility complex class I (MHC I) molecules. Coevolution between APGs and MHC I genes has been proposed as the ancestral gnathostome condition. The hypothesis predicts a single highly expressed MHC I gene and tight linkage between APGs and MHC I. In addition, APGs should evolve under positive selection, a consequence of the adaptive evolution in MHC I. The presence of multiple highly expressed MHC I genes in some teleosts, birds, and urodeles appears incompatible with the coevolution hypothesis. Here, we use urodele amphibians to test two key expectations derived from the coevolution hypothesis: 1) the linkage between APGs and MHC I was studied in Lissotriton newts and 2) the evidence for adaptive evolution in APGs was assessed using 42 urodele species comprising 21 genera from seven families. We demonstrated that five APGs (PSMB8, PSMB9, TAP1, TAP2, and TAPBP) are tightly linked (<0.5 cM) to MHC I. Although all APGs showed some codons under episodic positive selection, we did not find a pervasive signal of positive selection expected under the coevolution hypothesis. Gene duplications, putative gene losses, and divergent allelic lineages detected in some APGs demonstrate considerable evolutionary dynamics of APGs in salamanders. Overall, our results indicate that if coevolution between APGs and MHC I occurred in urodeles, it would be more complex than envisaged in the original formulation of the hypothesis.

Genetic patterning in the adult capitate antenna of the beetle Tribolium castaneum.

Antenna structure varies widely among insects, in contrast to the well-conserved structure of legs. The adult capitate antenna of the red flour beetle, Tribolium castaneum, is composed of eleven articles, organized into four distinct morphological regions (scape, pedicel, funicle and club). Here, we report the use of RNA interference to examine the functions of 21 genes during antenna metamorphosis in T. castaneum. Genes with conserved functions relative to the developmental model species Drosophila melanogaster include Distal-less and EGF signaling (antennal growth), spineless (determination of antennal identity) and the Notch signaling pathway (antennal growth, joint formation, and sensory bristle development). However, the functions of many genes differed from those predicted from the Drosophila model. In addition to a conserved gap phenotype, depletion of dachshund transformed funicle articles toward club-like identity. Depletion of Distal-less or homothorax did not cause antenna-to-leg transformation. Lim1 was required only for development of the scape-pedicle joint. Depletion of odd-skipped-related genes led to the loss of the entire funicle, while spalt, rotund, spineless, and dachshund affected smaller regions. Growth and joint formation were linked developmentally in the funicle, but not in the club. Joint formation within the club required bric-a-brac, aristaless, apterous, and pdm. Gene functions are discussed in terms of a model of antenna development in T. castaneum. This model provides a contrast to knowledge of antenna development in D. melanogaster, insight into the likely ancestral mode of antenna development, and a framework for considering diverse antenna morphologies.

The expression of wingless and Engrailed in developing embryos of the mayfly Ephoron leukon (Ephemeroptera: Polymitarcyidae).

The expression of the segment polarity genes wingless (wg) and engrailed (en) is highly conserved across arthropods, and these genes play a crucial role in patterning of the segmental body plan. Investigations of the expression and function of wg and en have focused primarily upon holometabolous insects, with the notable exception of recent detailed work in Oncopeltus (Hemiptera), Schistocerca, and Gryllus (Orthoptera). An increase in the phylogenetic breadth of our understanding of molecular patterning is crucial to ascertain the extent of conservation and divergence in molecular patterning mechanisms during insect embryogenesis. We examined the expression of wg mRNA transcripts and localization of En protein during embryogenesis in the mayfly Ephoron leukon (Ephemeroptera: Polymitarcyidae). These data represent one of the first embryonic gene expression pattern data for a mayfly, a lineage that may be the sister group to all other winged insects. Many aspects of wg and En expression are highly conserved, notably their expression in juxtaposed stripes in each parasegment, as well as expression domains in the procephalon, mouthparts, thoracic limbs, and nervous system. Future work in mayflies can be used to determine if conservation extends to other components of the segmentation hierarchy.

Co-option of wing-patterning genes underlies the evolution of the treehopper helmet.

Understanding the origin of novelty is a key question in evolutionary developmental biology. In arthropods, the body wall has served as a repeated source of morphological novelty. In treehoppers, an ancestrally flat part of the dorsal body wall (the pronotum) was transformed into a three-dimensional structure (the helmet), which was subsequently moulded by natural selection into diverse shapes. Here, we test three hypotheses for the developmental origin of the helmet by comparing body-region transcriptomes in a treehopper and a leafhopper that retains more ancestral morphology. In leafhoppers, pronotal gene expression is most similar to that of its serial homologue, the mesonotum. By contrast, in treehoppers, helmet gene expression is most similar to that of wings, supporting the wing-patterning network co-option hypothesis for the origin of the helmet. These results suggest that serial homologues may diverge evolutionarily through replacement of, rather than tinkering with, their ancestrally shared patterning network.

Slender salamanders (genus Batrachoseps) reveal Southern California to be a center for the diversification, persistence, and introduction of salamander lineages.

BACKGROUND: The southern California biodiversity hotspot has had a complex geological history, with both plate tectonic forces and sea level changes repeatedly reconfiguring the region, and likely driving both lineage splittings and extinctions. Here we investigate patterns of genetic divergence in two species of slender salamanders (Plethodontidae: Batrachoseps) in this region. The complex geological history in combination with several organismal traits led us to predict that these species harbor multiple ancient mitochondrial lineages endemic to southern California. These species belong to a clade characterized by fine-scale mitochondrial structure, which has been shown to track ancient splits. Both focal species, Batrachoseps major and B. nigriventris, are relatively widely distributed in southern California, and estimated to have persisted there across millions of years. Recently several extralimital populations of Batrachoseps were found in the San Joaquin Valley of California, a former desert area that has been extensively modified for agriculture. The origins of these populations are unknown, but based on morphology, they are hypothesized to result from human-mediated introductions of B. major. METHODS: We sequenced the mitochondrial gene cytochrome b from a geographically comprehensive sampling of the mitochondrial lineages of B. major and B. nigriventris that are endemic to southern California. We used phylogenetic analyses to characterize phylogeographic structure and identify mitochondrial contact zones. We also included the San Joaquin Valley samples to test whether they resulted from introductions. We used a bootstrap resampling approach to compare the strength of isolation-by-distance in both Batrachoseps species and four other salamander species with which they co-occur in southern California. RESULTS: The northern lineage of B. major harbors at least eight deeply differentiated, geographically cohesive mitochondrial subclades. We identify geographic contact between many of these mtDNA lineages and some biogeographic features that are concordant with lineage boundaries. Batrachoseps nigriventris also has multiple deeply differentiated clades within the region. Comparative analyses highlight the smaller spatial scales over which mitochondrial divergence accumulates in Batrachoseps relative to most other salamander species in southern California. The extralimital populations of Batrachoseps from the San Joaquin Valley are assigned to B. major and are shown to result from at least two independent introductions from different source populations. We also suggest that B. major on Catalina Island, where it is considered native, may be the result of an introduction. Some of the same traits that facilitate the build-up of deep phylogeographic structure in Batrachoseps likely also contribute to its propensity for introductions, and we anticipate that additional introduced populations will be discovered.

New insights into the identities of the elasmobranch fauna of Sri Lanka.

Identities of elasmobranchs from Sri Lanka encountered during collections conducted in an intensive nine-day survey of fish markets and landing sites at 11 localities in the North Western, Northern, and Eastern Provinces in March of 2018 were assessed. In total, 111 specimens representing 34 elasmobranch species were examined. Sequence data for the NADH2 gene were generated for all specimens. Independent Neighbor-Joining analyses, which included data for related taxa, were conducted for 25 subgroups of elasmobranchs to help confirm specific identifications. Five of the 34 species encountered are likely new to science. These consist of one species each of the batoid genera Brevitrygon, Narcine, and Torpedo, and the selachian genera Centrophorus, and Chiloscyllium. The specific identities of 12 species previously known to occur in Sri Lanka are updated to conform to current taxonomy; four of these (Gymnura cf. poecilura 2, Carcharhinus cf. limbatus, Echinorhinus sp. 1, and Iago cf. omanensis 1) represent what appear to be undescribed species reported previously from other localities. Three species (Maculabatis arabica, Acroteriobatus variegatus, and Centroscymnus owstonii) are reported from Sri Lanka for the first time; the latter species also represents the first documented record of this genus and family for the island nation. One of the two specimens on which the recent description of the new species of Planonasus indicus was based was also collected as part of this survey. Although some of the species confirmed to occur in Sri Lanka have also been found in India, others were previously known only from the Persian Gulf, Gulf of Oman, or localities in Southeast Asia. The high amount of novelty discovered as a result of a survey of such short duration emphasizes the importance of more intensive survey efforts in this region now that the civil unrest that precluded such work for nearly three decades has come to an end.