Performance of intron 7 of the β-fibrinogen gene for phylogenetic analysis: An example using gladiator frogs, Boana Gray, 1825 (Anura, Hylidae, Cophomantinae)

Boana, the third largest genus of Hylinae, has cryptic morphological species. The potential applicability of b-fibrinogen intron 7 – FGBI7 is explored to propose a robust phylogeny of Boana. The phylogenetic potential of FGBI7 was evaluated using maximum parsimony, MrBayes, and maximum likelihood analysis. Comparison of polymorphic sites and topologies obtained with concatenated analysis of FGBI7 and other nuclear genes (CXCR4, CXCR4, RHO, SIAH1, TYR, and 28S) allowed evaluation of the phylogenetic signal of FGBI7. Mean evolutionary rates were calculated using the sequences of the mitochondrial genes ND1 and CYTB available for Boana in GenBank. Dating of Boana and some of its groups was performed using the RelTime method with secondary calibration. FGBI7 analysis revealed high values at informative sites for parsimony. The absolute values of the mean evolutionary rate were higher for mitochondrial genes than for FGBI7. Dating of congruent Boana groups for ND1, CYTB, and FGBI7 revealed closer values between mitochondrial genes and slightly different values from those of FGBI7. Divergence times of basal groups tended to be overestimated when mtDNA was used and were more accurate when nDNA was used. Although there is evidence of phylogenetic potential arising from concatenation of specific genes, FGBI7 provides well-resolved independent gene trees. These results lead to a paradigm for linking data in phylogenomics that focuses on the uniqueness of species histories and ignores the multiplicities of individual gene histories.

Museomics and the holotype of a critically endangered cricetid rodent provide key evidence of an undescribed genus

Historical DNA obtained from voucher specimens housed in natural history museums worldwide have allowed the study of elusive, rare or even extinct species that in many cases are solely represented by museum holdings. This has resulted in the increase of taxonomic representation of many taxa, has led to the discovery of new species, and has yielded stunning novel insights into the evolutionary history of cryptic or even undescribed species. Peromyscus mekisturus, is a critically endangered cricetid rodent endemic to Mexico and is only known from two museum specimens collected in 1898 and 1947. Intensive field work efforts to attempt to determine if viable populations still exist have failed, suggesting that this species is extinct or is nearing extinction. In addition, a recent study using mitogenomes demonstrated that P. mekisturus forms a well-supported clade outside the genus Peromyscus and hypothesized that this taxon is the sister group of the genus Reithrodontomys. Here, we used target enrichment and high-throughput sequencing of several thousand nuclear ultraconserved elements and mitogenomes to reconstruct dated phylogenies to test the previous phylogenetic hypothesis. We analyzed the holotype and the only other known specimen of P. mekisturus and museum samples from other peromyscine rodents to test the phylogenetic position of the species. Our results confirm that the only two specimens known to science of P. mekisturus belong to the same species and support the hypothesis that this species belongs to an undescribed genus of cricetid rodents that is sister to the genus Reithrodontomys. We dated the origin of P. mekisturus together with other speciation events in peromyscines during the late Pliocene – early Pleistocene and related these events with the Pleistocene climatic cycles. In light of our results, we recommend a taxonomic re-evaluation of this enigmatic species to properly recognize its taxonomic status as a new genus. We also acknowledge the relevance of generating genomic data from type specimens and highlight the need and importance of continuing to build the scientific heritage of the collections to study and better understand past, present, and future biodiversity.

A spectacular new species of Hyloscirtus (Anura: Hylidae) from the Cordillera de Los Llanganates in the eastern Andes of Ecuador

We have discovered a spectacular new species of frog in the genus Hyloscirtus, belonging to the H. larinopygion species group. The adult female is characterized by a mostly black body with large bright red spots on the dorsal and ventral surface, extremities, and toe pads. The adult male is unknown. Small juveniles are characterized by a yellow body with variable black markings on the flanks; while one larger juvenile displayed irregular orange or yellow marks on a black background color, with light orange or yellow toe pads. Additional distinctive external morphological features such as cloacal ornamentation are described, and some osteological details are imaged and analyzed. The performed phylogeny places the new species as the sister to a clade consisting of ten taxa, all of which are part of the H. larinopygion group. We use genetic distances to fit the new species into a published time-calibrated phylogeny of this group; our analysis based on the published chronology suggests that the divergence of the new species from its known congeners pre-dates the Quaternary period. The new species is currently only known only from Cerro Mayordomo, in Fundación EcoMinga´s Machay Reserve, at 2,900 m in the eastern Andes of Tungurahua province, Ecuador, near the southern edge of Los Llanganates National Park, but its real distribution may be larger.

Sequence Capture From Historical Museum Specimens: Maximizing Value for Population and Phylogenomic Studies

The application of high-throughput, short-read sequencing to degraded DNA has greatly increased the feasibility of generating genomic data from historical museum specimens. While many published studies report successful sequencing results from historical specimens; in reality, success and quality of sequence data can be highly variable. To examine predictors of sequencing quality, and methodological approaches to improving data accuracy, we generated and analyzed genomic sequence data from 115 historically collected museum specimens up to 180 years old. Data span both population genomic and phylogenomic scales, including historically collected specimens from 34 specimens of four species of Australian rock-wallabies (genus Petrogale) and 92 samples from 79 specimens of Australo-Papuan murine rodents (subfamily Murinae). For historical rodent specimens, where the focus was sampling for phylogenomics, we found that regardless of specimen age, DNA sequence libraries prepared from toe pad or bone subsamples performed significantly better than those taken from the skin (in terms of proportion of reads on target, number of loci captured, and data accuracy). In total, 93% of DNA libraries from toe pad or bone subsamples resulted in reliable data for phylogenetic inference, compared to 63% of skin subsamples. For skin subsamples, proportion of reads on target weakly correlated with collection year. Then using population genomic data from rock-wallaby skins as a test case, we found substantial improvement in final data quality by mapping to a high-quality “closest sister” de novo assembly from fresh tissues, compared to mapping to a sample-specific historical de novo assembly. Choice of mapping approach also affected final estimates of the number of segregating sites and Watterson's θ, both important parameters for population genomic inference. The incorporation of accurate and reliable sequence data from historical specimens has important outcomes for evolutionary studies at both population and phylogenomic scales. By assessing the outcomes of different approaches to specimen subsampling, library preparation and bioinformatic processing, our results provide a framework for increasing sequencing success for irreplaceable historical specimens.

Taxonomic Identification of Two Poorly Known Lantern Shark Species Based on Mitochondrial DNA From Wet-Collection Paratypes

Etmopteridae (lantern sharks) is the most species-rich family of sharks, comprising more than 50 species. Many species are described from few individuals, and re-collection of specimens is often hindered by the remoteness of their sampling sites. For taxonomic studies, comparative morphological analysis of type specimens housed in natural history collections has been the main source of evidence. In contrast, DNA sequence information has rarely been used. Most lantern shark collection specimens, including the types, were formalin fixed before long-term storage in ethanol solutions. The DNA damage caused by both fixation and preservation of specimens has excluded these specimens from DNA sequence-based phylogenetic analyses so far. However, recent advances in the field of ancient DNA have allowed recovery of wet-collection specimen DNA sequence data. Here we analyse archival mitochondrial DNA sequences, obtained using ancient DNA approaches, of two wet-collection lantern shark paratype specimens, namely Etmopterus litvinovi and E. pycnolepis, for which the type series represent the only known individuals. Target capture of mitochondrial markers from single-stranded DNA libraries allows for phylogenetic placement of both species. Our results suggest synonymy of E. benchleyi with E. litvinovi but support the species status of E. pycnolepis. This revised taxonomy is helpful for future conservation and management efforts, as our results indicate a larger distribution range of E. litvinovi. This study further demonstrates the importance of wet-collection type specimens as genetic resource for taxonomic research.

Simultaneous Barcode Sequencing of Diverse Museum Collection Specimens Using a Mixed RNA Bait Set

A growing number of publications presenting results from sequencing natural history collection specimens reflect the importance of DNA sequence information from such samples. Ancient DNA extraction and library preparation methods in combination with target gene capture are a way of unlocking archival DNA, including from formalin-fixed wet-collection material. Here we report on an experiment, in which we used an RNA bait set containing baits from a wide taxonomic range of species for DNA hybridisation capture of nuclear and mitochondrial targets for analysing natural history collection specimens. The bait set used consists of 2,492 mitochondrial and 530 nuclear RNA baits and comprises specific barcode loci of diverse animal groups including both invertebrates and vertebrates. The baits allowed to capture DNA sequence information of target barcode loci from 84% of the 37 samples tested, with nuclear markers being captured more frequently and consensus sequences of these being more complete compared to mitochondrial markers. Samples from dry material had a higher rate of success than wet-collection specimens, although target sequence information could be captured from 50% of formalin-fixed samples. Our study illustrates how efforts to obtain barcode sequence information from natural history collection specimens may be combined and are a way of implementing barcoding inventories of scientific collection material.

The phylogeny of Dendropsophini (Anura: Hylidae: Hylinae)

The relationships of the hyline tribe Dendropsophini remain poorly studied, with most published analyses dealing with few of the species groups of Dendropsophus. In order to test the monophyly of Dendropsophini, its genera, and the species groups currently recognized in Dendropsophus, we performed a total evidence phylogenetic analysis. The molecular dataset included sequences of three mitochondrial and five nuclear genes from 210 terminals, including 12 outgroup species, the two species of Xenohyla, and 93 of the 108 recognized species of Dendropsophus. The phenomic dataset includes 46 terminals, one per species (34 Dendropsophus, one Xenohyla, and 11 outgroup species). Our results corroborate the monophyly of Dendropsophini and the reciprocal monophyly of Dendropsophus and Xenohyla. Some species groups of Dendropsophus are paraphyletic (the D. microcephalus, D. minimus, and D. parviceps groups, and the D. rubicundulus clade). On the basis of our results, we recognize nine species groups; for three of them (D. leucophyllatus, D. microcephalus, and D. parviceps groups) we recognize some nominal clades to highlight specific morphology or relationships and facilitate species taxonomy. We further discuss the evolution of oviposition site selection, where our results show multiple instances of independent evolution of terrestrial egg clutches during the evolutionary history of Dendropsophus.

Mitochondrial DNA sequencing of a wet-collection syntype demonstrates the importance of type material as genetic resource for lantern shark taxonomy (Chondrichthyes: Etmopteridae)

After initial detection of target archival DNA of a 116-year-old syntype specimen of the smooth lantern shark, Etmopterus pusillus, in a single-stranded DNA library, we shotgun-sequenced additional 9 million reads from this same DNA library. Sequencing reads were used for extracting mitochondrial sequence information for analyses of mitochondrial DNA characteristics and reconstruction of the mitochondrial genome. The archival DNA is highly fragmented. A total of 4599 mitochondrial reads were available for the genome reconstruction using an iterative mapping approach. The resulting genome sequence has 12 times coverage and a length of 16 741 bp. All 37 vertebrate mitochondrial loci plus the control region were identified and annotated. The mitochondrial NADH2 gene was subsequently used to place the syntype haplotype in a network comprising multiple E. pusillus samples from various distant localities as well as sequences from a morphological similar species, the shortfin smooth lantern shark Etmopterus joungi. Results confirm the almost global distribution of E. pusillus and suggest E. joungi to be a junior synonym of E. pusillus. As mitochondrial DNA often represents the only available reference information in non-model organisms, this study illustrates the importance of mitochondrial DNA from an aged, wet collection type specimen for taxonomy.

A new reproductive mode in anurans: Natural history of Bokermannohyla astartea (Anura: Hylidae) with the description of its tadpole and vocal repertoire

Anurans have the greatest diversity of reproductive modes among tetrapod vertebrates, with at least 41 being currently recognized. We describe a new reproductive mode for anurans, as exhibited by the Paranapiacaba Treefrog, Bokermannohyla astartea, an endemic and poorly known species of the Brazilian Atlantic Forest belonging to the B. circumdata group. We also describe other aspects of its reproductive biology, that are relevant to understanding the new reproductive mode, such as courtship behavior, spawning, and tadpoles. Additionally, we redescribe its advertisement call and extend its vocal repertoire by describing three additional call types: courtship, amplectant, and presumed territorial. The new reproductive mode exhibited by B. astartea consists of: (1) deposition of aquatic eggs in leaf-tanks of terrestrial or epiphytic bromeliads located on or over the banks of temporary or permanent streams; (2) exotrophic tadpoles remain in the leaf-tanks during initial stages of development (until Gosner stage 26), after which they presumably jump or are transported to streams after heavy rains that flood their bromeliad tanks; and (3) tadpole development completes in streams. The tadpoles of B. astartea are similar to those of other species of the B. circumdata group, although with differences in the spiracle, eyes, and oral disc. The vocal repertoire of B. astartea exhibits previously unreported acoustic complexity for the genus. Bokermannohyla astartea is the only bromeligenous species known to date among the 187 known species within the tribe Cophomantini. We further discuss evolutionary hypotheses for the origin of this novel reproductive mode.