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Aim: We tested whether populations of violet-crowned and green-fronted hummingbirds, Amazilia violiceps and Amazilia viridifrons, are genetically and environmentally differentiated, and examined the role of past geological and climatic changes in driving their diversification. Location: Trans-Mexican Volcanic Belt. Methods: Mitochondrial and nuclear DNA of individuals collected throughout the species' ranges were sequenced and then analysed using maximum-likelihood and Bayesian approaches. Species tree analysis, Bayesian species delimitation, divergence time inference, historical demography, palaeodistribution modelling, and niche divergence tests were used to reconstruct the evolutionary history of the Amazilia species, and the isolation-with-migration coalescent model was assessed to determine whether genetic divergence between Amazilia species occurred in the presence of gene flow. Results: Genetic divergence between A. violiceps and A. viridifrons was shallow, with incomplete lineage sorting and introgression. Species delimitation supported three independent lineages: A. violiceps populations located north of the Trans-Mexican Volcanic Belt; a mixture of A. violiceps south of the volcanic belt and A. viridifrons populations; and A. villadai populations east of the Isthmus of Tehuantepec. Gene flow and divergence time estimates, and demographic and palaeodistribution patterns support the model of species diversification by isolation with migration and habitat shifting in response to Pleistocene climatic fluctuations. Main conclusions: The process of speciation in the Amazilia species complex may be explained by the combined effects of isolation resulting from the Trans-Mexican Volcanic Belt and the lowlands at the Isthmus of Tehuantepec and habitat shifting in response to Quaternary climatic changes.

Aim: We test whether populations of the Mesoamerican azure-crowned hummingbird, Amazilia cyanocephala (Trochilidae), located east and west of the Isthmus of Tehuantepec are genetically, morphologically and environmentally differentiated and examine the relative role of drift and selection in driving diversification. Location: Mexico. Methods: We sequenced the mitochondrial ATPase-6 and ATPase-8 genes and the control region of 130 individuals collected throughout the range of the species in Mexico. Population genetic methods and coalescent tests were used to reconstruct the phylogeography of the species. Morphological and niche variation between genetic groups of A. cyanocephala were assessed. Results: The data revealed two genetic groups separated by the Isthmus of Tehuantepec in the late Pleistocene (49,300—75,800 years ago), with the split occurring in the presence of gene flow. Deviations from demographic equilibrium were detected for the two genetic groups, indicating more recent population expansions. Amazilia cyanocephala individuals from populations on either side of the Isthmus of Tehuantepec differed in morphology and were distributed in unique environmental space. A coalescent-based test indicated that selection is driving the observed morphological differentiation. Main conclusions: Our findings implicate the Isthmus of Tehuantepec as a permeable barrier driving recent diversification of A. cyanocephala in the presence of gene flow. The two A. cyanocephala mitochondrial DNA (mtDNA) groups corresponding with morphological and environmental niche differences, in concert with the results of a coalescent-based test, suggest that selection has been strong enough to counteract the effects of gene flow.

In December 2019, the first cases of the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) were identified in the city of Wuhan, China. Since then, it has spread worldwide with new mutations being reported. The aim of the present study was to monitor the changes in genetic diversity and track non-synonymous substitutions (dN) that could be implicated in the fitness of SARS-CoV-2 and its spread in different regions between December 2019 and November 2020. We analyzed 2213 complete genomes from six geographical regions worldwide, which were downloaded from GenBank and GISAID databases. Although SARS-CoV-2 presented low genetic diversity, there has been an increase over time, with the presence of several hotspot mutations throughout its genome. We identified seven frequent mutations that resulted in dN substitutions. Two of them, C14408T>P323L and A23403G>D614G, located in the nsp12 and Spike protein, respectively, emerged early in the pandemic and showed a considerable increase in frequency over time. Two other mutations, A1163T>I120F in nsp2 and G22992A>S477N in the Spike protein, emerged recently and have spread in Oceania and Europe. There were associations of P323L, D614G, R203K and G204R substitutions with disease severity. Continuous molecular surveillance of SARS-CoV-2 will be necessary to detect and describe the transmission dynamics of new variants of the virus with clinical relevance. This information is important to improve programs to control the virus.

Lagomorpha (lagomorphs), the order of mammals including pikas, hares, and rabbits, is distributed on all continents. The order currently is hypothesized to comprise 12 genera and 108 species, split into two families: Ochotonidae (pikas) and Leporidae (rabbits and hares). Molecular and morphological attempts have been undertaken to resolve the phylogeny of lagomorphs, although chronological relationships are still to be established. The aim of this research was to unravel lagomorph phylogeny using ultraconserved elements. We focused on Romerolagus , in light of its largely unknown phylogenetic relationships and sparse fossil record, to assess times of divergence for the genus. We obtained samples from at least one species in each of 11 genera (except Caprolagus ) comprising the order and captured and sequenced ultraconserved elements (UCEs). A Maximum-Likelihood phylogenetic analysis was carried out on the 4,195 loci captured, resulting in 59,112 informative sites. We further used BEAST2 v2.6.3 on the CIPRES computing cluster to estimate the timing of cladogenesis in lagomorph evolution. Our results confirm that lagomorphs and rodents split about 65 million years ago. The former further split into its constituent families, Leporidae and Ochotonidae, about 60 million years ago. Pronolagus rupestris and Nesolagus timminsi were retrieved as basal sister taxa; the most recent common ancestor of that clade and remaining leporids was estimated to have existed about 47 million years ago. Romerolagus diazi is sister to remaining Leporidae excluding Pronolagus and Nesolagus , a topology that generally matches previously published phylogenies, although our results suggest a most recent common ancestor of Romerolagus and remaining ingroup leporids at ca. 4.8 Ma (95% highest posterior density [HPD] interval: 5.9 – 3.8 Ma), with an internal diversification in the Middle to Late Pleistocene (0.9 Ma; 95% HPD 1.8 – 0.2 Ma). Our final results yielded a robust phylogeny with high support values for every clade of the order Lagomorpha and unraveled previously unresolved phylogenetic relationships. In addition, we further conclude that the method we used, UCEs, may serve to complete the entire phylogeny of mammals by using existing museum specimens.

The Tropical Montane Cloud Forest (TMCF) is a highly dynamic ecosystem that has undergone frequent spatial changes in response to the interglacial-glacial cycles of the Pleistocene. These climatic fluctuations between cold and warm cycles have led to species range shifts and contractions-expansions, resulting in complex patterns of genetic structure and lineage divergence in forest tree species. In this study, we sequenced four regions of the chloroplast DNA ( trnT-trnL, trnK5-matk , rpl32-trnL , trnS-trnG ) for 20 populations and 96 individuals to evaluate the phylogeography, historical demography, and paleodistributions of vulnerable endemic TMCF trees in Mexico: Magnolia pedrazae (north-region), M. schiedeana (central-region), and M. schiedeana population Oaxaca (south-region). Our data recovered 49 haplotypes that showed a significant phylogeographic structure in three regions: north, central, and south. Bayesian Phylogeographic and Ecological Clustering (BPEC) analysis also supported the divergence in three lineages and highlighted the role of environmental factors (temperature and precipitation) in genetic differentiation. Our historical demography analyses revealed demographic expansions predating the Last Interglacial (LIG, ~125,000 years ago), while Approximate Bayesian Computation (ABC) simulations equally supported two contrasting demographic scenarios. The BPEC and haplotype network analyses suggested that ancestral haplotypes were geographically found in central Veracruz. Our paleodistributions modeling showed evidence of range shifts and expansions-contractions from the LIG to the present, which suggested the complex evolutionary dynamics associated to the climatic oscillations of the Pleistocene. Habitat management of remnant forest fragments where large and genetically diverse populations occur in the three TMCF regions analyzed would be key for the conservation of these magnolia populations.

Global climate change is associated with changes in precipitation patterns and an increase in extreme weather events, which might shift the geographic distribution of species. Despite the importance of this topic, information is lacking for many species, particularly tropical birds. Here, we developed species distribution models (SDMs) to evaluate future projections of the distribution of the widespread Buff-bellied Hummingbird (Amazilia yucatanensis) and for each of the recognized subspecies (A. y. yucatanensis, A. y. cerviniventris, A. y. chalconota), under climate change scenarios. Using SDMs we evaluate current and future projections of their potential distribution for four Representative Concentration Pathway (RCPs) for the years 2050 and 2070. We also calculated the subspecies climatic niche breadth to test the relationship between their area of distribution and climatic niche breadth and their niche overlap. Future climate-change models suggested a small increase in the potential distribution of the species and the subspecies A. y. yucatanensis, but the predicted potential geographic range decreased in A. y. chalconota and remained unaffected in A. y. cerviniventris. The climatic niche of A. y. cerviniventris contained part niche space of A. y. yucatanensis and part of A. y. chalconota, but the climatic niches of A. y. yucatanensis and A. y. chalconota did not overlap. Our study highlights the importance of correctly choosing the taxonomic unit to be analyzed because subspecies will respond in a different manner to future climate change; therefore, conservation actions must consider intrinsic requirements of subspecies and the environmental drivers that shape their distributions.

Aim We used mitochondrial DNA sequences to reconstruct the phylogenetic relationships of Mesoamerican Amazilia hummingbirds (Trochilidae). The phylogeny was used to identify vicariance scenarios, reconstruct ancestral biogeographical areas, and investigate the role of geological events in generating genetic divergence through vicariance events. Location Mesoamerica. Methods Molecular sequence data were gathered from three mitochondrial genes (ND2, ND5 and 12S) for samples taken within the Mesoamerican region and analysed using maximum parsimony, maximum-likelihood and Bayesian approaches. Statistical dispersal–vicariance analysis (S-DIVA) was used to reconstruct biogeographical areas and changes in distribution during the evolutionary history of Amazilia. The phylogeny was calibrated using fossil dates, mean substitution rates and coalescent-based divergence time inference. Results Amazilia can be split into two divergent lineages, with high levels of sequence divergence within some Mesoamerican species. Ancestral area reconstructions favour an ancestral distribution west of the Isthmus of Tehuantepec, with subsequent dispersals east of the isthmus and to South America. Divergence time estimations suggest that major diversification events occurred in the Miocene and Pliocene, corresponding temporally and geographically to the formation of the mountain systems and establishment of the major biomes in Mesoamerica. Main conclusions The diversification of Amazilia corresponds to vegetation shifts in combination with regional orogenesis. Intriguingly, the timing of the major diversification events and dispersal into South America pre-dates the completion of the Panamanian isthmus c. 4 Ma before present.

Recent historical and anthropogenic changes in the landscape causing habitat fragmentation can disrupt the connectivity of wild populations and pose a threat to the genetic diversity of multiple species. This study investigated the effect of habitat fragmentation on the structure and genetic diversity of the Mexican greater funnel-eared bat (Natalus mexicanus) throughout its distribution range in Mexico, whose natural habitat has decreased dramatically in recent years. Genetic structure and diversity were measured using the HVII hypervariable domain of the mitochondrial control region and ten nuclear microsatellite loci, to analyze historical and contemporary information, respectively. The mitochondrial and nuclear results pointed to a differential genetic structuring, derived mainly from philopatry in females. Our results also showed that genetic diversity was historically high and currently moderate; additionally, the contemporary gene flow between the groups observed was null. These findings confirm that the effects of habitat fragmentation have started to be expressed in populations and that forest loss is already building barriers to contemporary gene flow. The concern is that gene flow is a process essential to ensure that the genetic diversity of N. mexicanus populations (and probably of many other forest species) distributed in Mexico is preserved or increased in the long term by maintaining forest connectivity between locations.

Two sibling bare-backed bat species (Pteronotus fulvus and P. gymnonotus) have been traditionally differentiated by their size. However, intermediate specimens between the two species have been found in sympatric populations along southern Mexico and it has been suggested that they may be the outcome of a hybridization process between the two species. We used one mitochondrial (COI), three nuclear markers (PRKCL, STAT5A and RAG2) and 13 microsatellites to explore the evolutionary relationships between these two species and elucidate whether the intermediate morphotypes correspond to hybrid individuals. These markers have been analyzed in sympatric and allopatric populations of the two species plus the closely related species Pteronotus davyi. We confirmed the species-level differentiation of the three lineages (P. fulvus, P. davyi and P. gymnonotus), but the phylogenetic hypotheses suggested by the nuclear and mitochondrial markers were discordant. We confirm that the discordance between markers is due to genetic introgression through the mitochondrial capture of P. fulvus in P. gymnonotus populations. Such introgression was found in all P. gymnonotus specimens across its sympatric distribution range (Mexico to Costa Rica) and is related to expansion/retraction species distribution pulses associated with changes in forest distribution during the Quaternary climate cycles. Microsatellite analyses showed contemporary genetic contact between the two sympatric species and 3.0% of the samples studied were identified as hybrids. In conclusion, we found a historical and asymmetric genetic introgression (through mitochondrial capture) of P. fulvus into P. gymnonotus in Mexico and Central America and a limited contemporary gene exchange between the two species. However, no relationship was found between hybridization and the intermediate-sized specimens from southern Mexico, which might likely result from a clinal variation with latitude. These results confirm the need for caution when using forearm size to identify these species in the field and when differentiating them in the laboratory based on mitochondrial DNA alone.

The gut microbiome of wild birds contributes to host fitness by supporting nutrient absorption, toxin processing, and immune function. It also fights bacterial pathogens through competitive exclusion and the production of antimicrobial metabolites. This study analyzed the in vitro antagonistic activity of bacteria isolated from the feces of the violet-crowned hummingbird ( Ramsomyia violiceps ) against strains of Bacillus spp., Escherichia coli , Salmonella enterica , and Acinetobacter baumannii . Mist nets were placed in three parks within the Guadalajara Metropolitan Area. Fecal samples were collected from captured R. violiceps and inoculated into culture media. Bacteria exhibiting antagonist activity were identified using molecular techniques that targeted the V1-V9 region of the 16S rRNA gene. The gut strains Bacillus sp. 1, Bacillus sp. 2, B. altitudinis , B. thuringiensis , and B. subtilis exhibited antagonistic activity against Bacillus cereus , B. tequilensis , and A. baumannii . Pseudomonas putida M5 antagonized Bacillus spp., E. coli, S. enterica , and A. baumannii. This result indicates that some Bacillus spp. and Pseudomonas spp. in the cultivable bacterial assembly of the gut of R. violiceps produce secondary metabolites that can inhibit the growth of both Gram-positive and Gram-negative strains. Since diet plays a determining role in the gut bacterial assemblage of birds, our results suggest that the strains that showed antagonistic activity in vitro could be related to the nectar consumed by the hummingbird. This may help promote the synthesis of antimicrobial compounds as a resistance mechanism.