Urbanization is a prominent demographic process that can transform the landscape and create environmental gradients into natural environments. Cities can provide roosts for many bat species, while others avoid these anthropized environments. Therefore, species-specific studies are needed to understand the responses of bats to urbanization. Promops centralis is a poorly known Neotropical bat that occurs in a wide variety of ecoregions and habitats including cities, making it a good study model. Our main goal was to assess habitat use and temporal activity patterns of this bat across an urban-natural gradient using acoustic data. We also evaluated the use of acoustic space and relationships with sympatric and similar species, such as P. nasutus, Molossops temminckii, and M. neglectus. To our knowledge, this is the first study that uses acoustic monitoring to assess the habitat preferences of bats in Argentina. In 2,535 minutes of recording, 142 P. centralis passes were detected. Data were collected for all habitats (urban, grassland, forest) and for 3 time periods distributed at the beginning, middle, and end of the night. We were able to detect higher levels of activity of P. centralis in grasslands followed by urban habitats and forest, indicating a strong habitat preference at the landscape scale. We also found changes in echolocation behavior in response to habitat, specifically between grassland (open habitat) versus forest and urban (closed habitats), demonstrating echolocation plasticity and ability of the species to explore urban habitats. We found a peak of activity during the first 3 h of the night and a decrease the rest of the night, providing evidence of a unimodal pattern. Lastly, we observed a clear segregation in the acoustic parameters of P. centralis and its sympatric species. Interestingly, when there is overlap in the acoustic parameters of calls between species they emitted pulses with opposite modulation, suggesting a possible segregation mechanism.

Yerba mate (YM, Ilex paraguariensis) is an economically important crop marketed for the elaboration of mate, the third-most widely consumed caffeine-containing infusion worldwide. Here, we report the first genome assembly of this species, which has a total length of 1.06 Gb and contains 53,390 protein-coding genes. Comparative analyses revealed that the large YM genome size is partly due to a whole-genome duplication (Ip-α) during the early evolutionary history of Ilex, in addition to the hexaploidization event (γ) shared by core eudicots. Characterization of the genome allowed us to clone the genes encoding methyltransferase enzymes that catalyse multiple reactions required for caffeine production. To our surprise, this species has converged upon a different biochemical pathway compared to that of coffee and tea. In order to gain insight into the structural basis for the convergent enzyme activities, we obtained a crystal structure for the terminal enzyme in the pathway that forms caffeine. The structure reveals that convergent solutions have evolved for substrate positioning because different amino acid residues facilitate a different substrate orientation such that efficient methylation occurs in the independently evolved enzymes in YM and coffee. While our results show phylogenomic constraint limits the genes coopted for convergence of caffeine biosynthesis, the X-ray diffraction data suggest structural constraints are minimal for the convergent evolution of individual reactions.

Supernumerary chromosomes (B chromosomes) have been an intriguing subject of study. Our understanding of the molecular differentiation of B chromosomes from an interpopulation perspective remains limited, with most analyses involving chromosome banding and mapping of a few sequences. To gain insights into the molecular composition, origin, and evolution of B chromosomes, we conducted cytogenetic and next-generation sequencing analysis of the repeatome in the grasshopper Abracris flavolineata across various populations. Our results unveiled the presence of B chromosomes in two newly investigated populations and described new satellite DNA sequences. While we observed some degree of genetic connection among A. flavolineata populations, our comparative analysis of genomes with and without B chromosomes provided evidence of two new B chromosome variants. These variants exhibited distinct compositions of various repeat classes, including transposable elements and satellite DNAs. Based on shared repeats, their chromosomal location, and the C-positive heterochromatin content on the B chromosome, these variants likely share a common origin but have undergone distinct molecular differentiation processes, resulting in varying degrees of heterochromatinization. Our data serve as a detailed example of the dynamic and differentiated nature of B chromosome molecular content at the interpopulation level, even when they share a common origin.

Grasshoppers in the genus Ronderosia (divergence time < 5 Mya) provide a special opportunity to examine the impact of chromosome rearrangements (CRs) in evolution and speciation, because they exhibit extensively rearranged karyotypes involving autosome-autosome and autosome-X chromosomes, the latter leading to the formation of a neo-sex chromosome system (neo-SCS). Despite the potential role of CRs in speciation, the general patterns of karyotype changes resulting from CRs in Ronderosia are still unclear. Here we investigated karyotype evolution in eight Ronderosia species using cytogenetic and phylogenetic models of ancestral character reconstruction. The overall findings suggest a central role for CRs in generating variability in chromosome number and neo-SCS across Ronderosia grasshoppers. It also suggests that incipient species with little morphological change, such as those observed in Ronderosia species, could accumulate marked differences in their karyotypes contributing to post-zygotic reproductive isolation. Besides the evolution of chromosome number in the phylogeny of the genus, chromosome change due to centric fusion is coupled with the divergence pattern observed in the group. While a cladogenetic event could represent a case where karyotypic differences result in speciation, further in-depth genomic studies are needed to better understand how these dramatic restructurings of karyotypes may have occurred.

B chromosomes are supernumerary elements that have a wide taxonomic distribution among eukaryotes. Although they are dispensable, they can acquire mechanisms to be overrepresented in the next generation and therefore avoid being eliminated. These elements have been discovered in < 2% of the karyotyped anurans. B chromosomes were described for Argentine and Brazilian populations of Boana albopunctata, a Neotropical tree frog widely distributed in the central region of South America. We assessed the distribution of B chromosomes in this species via cytogenetic studies of 365 specimens from Argentina, Brazil and Paraguay. We found that 101 individuals carried B chromosomes, with striking differences in their frequency of occurrence among localities. Our findings might be related to the evolutionary dynamics of these elements. Microdissection and chromosome painting experiments demonstrated sequence similarity between B chromosomes from localities that are > 1000 km apart, showing the most widely distributed B chromosome system known for anurans. The B chromosome system of B. albopunctata might help to fill the general knowledge gap for these elements in anurans compared with other vertebrates.

Neotropical fishes have highly diversified karyotypic and genomic characteristics and present many diverse sex chromosome systems, with various degrees of sex chromosome differentiation. Knowledge on their sex-specific composition and evolution, however, is still limited. Satellite DNAs (satDNAs) are tandemly repeated sequences with pervasive genomic distribution and distinctive evolutionary pathways, and investigating satDNA content might shed light into how genome architecture is organized in fishes and in their sex chromosomes. The present study investigated the satellitome of Megaleporinus elongatus, a freshwater fish with a proposed Z1Z1Z2Z2/Z1W1Z2W2 multiple sex chromosome system that encompasses a highly heterochromatic and differentiated W1 chromosome. The species satellitome comprises of 140 different satDNA families, including previously isolated sequences and new families found in this study. This diversity is remarkable considering the relatively low proportion that satDNAs generally account for the M. elongatus genome (around only 5%). Differences between the sexes in regards of satDNA content were also evidenced, as these sequences are 14% more abundant in the female genome. The occurrence of sex-biased signatures of satDNA evolution in the species is tightly linked to satellite enrichment associated with W1 in females. Although both sexes share practically all satDNAs, the overall massive amplification of only a few of them accompanied the W1 differentiation. We also investigated the expansion and diversification of the two most abundant satDNAs of M. elongatus, MelSat01-36 and MelSat02-26, both highly amplified sequences in W1 and, in MelSat02-26’s case, also harbored by Z2 and W2 chromosomes. We compared their occurrences in M. elongatus and the sister species M. macrocephalus (with a standard ZW sex chromosome system) and concluded that both satDNAs have led to the formation of highly amplified arrays in both species; however, they formed species-specific organization on female-restricted sex chromosomes. Our results show how satDNA composition is highly diversified in M. elongatus, in which their accumulation is significantly contributing to W1 differentiation and not satDNA diversity per se. Also, the evolutionary behavior of these repeats may be associated with genome plasticity and satDNA variability between the sexes and between closely related species, influencing how seemingly homeologous heteromorphic sex chromosomes undergo independent satDNA evolution.

In Acridoidea grasshoppers, chromosomal rearrangements are frequently found as deviations from the standard acrocentric karyotype (2n = 23♂/24♀, FN = 23♂/24♀) in either phylogenetically unrelated species or shared by closely related ones, i.e. genus. In the South American subfamily Ommexechinae, most of the species show a unique karyotype (2n = 23♂/24♀, FN = 25♂/26♀) owing to the occurrence of a large autosomal pair (L1) with submetacentric morphology. In the early 1960s, Alejo Mesa proposed the hypothesis of an ancestral pericentric inversion to explain this karyotype variation. Furthermore, in Ommexechinae, extra chromosomal rearrangements (e.g. centric fusions) are recorded between the ancestral X chromosome and autosomes that originated the so-called neo-sex chromosomes. However, the evolutionary significance of the pericentric inversions and centric fusions in Ommexechinae remains poorly explored. Aiming for a better understanding of chromosomal evolution in Ommexechinae, we performed a detailed cytogenetic analysis in five species. Our findings support the hypothesis about the occurrence of an early pericentric inversion in the ancestor of Ommexechinae. Moreover, our results show a complex karyotype diversification pattern due to several chromosome rearrangements, variations in heterochromatin and repetitive DNA dynamics. Finally, the chromosomal mapping of U2 snDNA in L1 provided new insights about the morphological evolution of this autosomal pair and revealed unnoticed chromosome reorganizations.

The larva of Zenithoptera lanei Santos, 1941 is described and illustrated based on three exuviae of reared larvae collected in Misiones, Argentina, Roraima and Amazonas, Brazil. A comparison with the larva of Z. anceps Pujol-Luz, 1993 is included.

Satellite DNA (satDNA) is an abundant class of tandemly repeated noncoding sequences, showing high rate of change in sequence, abundance, and physical location. However, the mechanisms promoting these changes are still controversial. The library model was put forward to explain the conservation of some satDNAs for long periods, predicting that related species share a common collection of satDNAs, which mostly experience quantitative changes. Here, we tested the library model by analyzing three satDNAs in ten species of Schistocerca grasshoppers. This group represents a valuable material because it diversified during the last 7.9 Myr across the American continent from the African desert locust (Schistocerca gregaria), and this thus illuminates the direction of evolutionary changes. By combining bioinformatic and cytogenetic, we tested whether these three satDNA families found in S. gregaria are also present in nine American species, and whether differential gains and/or losses have occurred in the lineages. We found that the three satDNAs are present in all species but display remarkable interspecies differences in their abundance and sequences while being highly consistent with genus phylogeny. The number of chromosomal loci where satDNA is present was also consistent with phylogeny for two satDNA families but not for the other. Our results suggest eminently chance events for satDNA evolution. Several evolutionary trends clearly imply either massive amplifications or contractions, thus closely fitting the library model prediction that changes are mostly quantitative. Finally, we found that satDNA amplifications or contractions may influence the evolution of monomer consensus sequences and by chance playing a major role in driftlike dynamics.

The scorpion Tityus bahiensis is the most common scorpion species of medical importance with sexual reproduction in South America. Many of the populations cytogenetically studied so far are polymorphic both for chromosome number and meiotic configuration in males. In this work, we perform cytogenetic analysis of three of the most meridional populations of T. bahiensis occurring in north-eastern Argentina (Misiones province), which showed numerical and structural variations with respect to previously studied populations. We describe four new diploid numbers in males for this species, from 2n = 12 to 2n = 15, seven different cytotypes, and we analyze the chromosome rearrangements involved in the different multivalent associations observed during meiosis (II, III, V, VI, VII and IX). Ribosomal DNA is invariably present at one terminal region on each of two chromosomes. Blocks of constitutive heterochromatin of different sizes are found at the terminal regions of every chromosome in the different cytotypes, along with subterminal and interstitial blocks in some chromosomes. Based on the rDNA and constitutive heterochromatin localization, we analyzed chromosome evolution within these populations. We propose that all the cytotypes could have originated from a hypothetical ancestral karyotype with 2n = 18 and 9 bivalents at meiosis I but followed two pathways with different sequences of mainly fusions and some translocations from the ancestral karyotype. Furthermore, we review all the cytogenetically studied populations of this species and their distribution to discuss the chromosomal evolution of this polymorphic species. (c) 2020 Elsevier GmbH. All rights reserved.

In an attempt to unveil the origin of neo‐sex chromosomes in Ronderosia Cigliano grasshoppers, we performed a combined phylogenetic analysis based on morphological (external morphology and male genitalia) and molecular data (COI, COII, 16S and ITS2) to explore the chromosome evolution within the genus. We also analysed the distributional patterns of the various Ronderosia species and considered the possible role of chromosome rearrangements (CRs) in speciation processes within the genus in the light of ‘suppressed‐recombination’ models. We mapped the states of three chromosomal characters on the combined tree topology. The combined evidence supported Ronderosia as a monophyletic group. The cytogenetic analyses of the genus demonstrated the importance of rearranged karyotypes with single, complex and multiples neo‐sex chromosome determination systems in all species. The chromosome character optimisation suggests X‐autosome centric fusion as the mechanism responsible for neo‐sex chromosome formation in most Ronderosia species, except in R. dubia and R. bergii. Similar autosomes were involved in fusions with the ancestral X chromosome in Ronderosia, supporting previous hypotheses on the unique origin of X‐autosome fusion for the sex chromosome in the genus. As a source of chromosome variation, autosome‐autosome centric fusion played a secondary role in Ronderosia compared with other Dichroplini. Given the homogeneity in the morphological features, the sympatric distribution of closely related species and the intrinsic property of centric fusion as suppressors of the crossing over, we suggest that CRs may have played a key role during the speciation process within Ronderosia.

To better understand the structure and variability of the 45S rDNA cistron and its evolutionary dynamics in grasshoppers, we performed a detailed analysis combining classical and molecular cytogenetic data with whole-genome sequencing in Abracris flavolienata, which shows extraordinary variability in the chromosomal distribution for this element. We found astonishing variability in the number and size of rDNA clusters at intra- and inter-population levels. Interestingly, FISH using distinct parts of 45S rDNA cistron (18S rDNA, 28S rDNA, and ITS1) as probes revealed a distinct number of clusters, suggesting independent mobility and amplification of the 45S rDNA components. This hypothesis is consistent with the higher genomic coverage of almost the entire cistron of 45S rDNA observed in A. flavolineata compared to other grasshoppers, besides coverage variability along the 45S rDNA cistron in the species. In addition, these differences in coverage for distinct components of the 45S rDNA cistron indicate emergence of pseudogenes evidenced by existence of truncated sequences, demonstrating the rDNA dynamics in the species. Although the chromosomal distribution of 18S rDNA was highly variable, the chromosomes 1, 3, 6, and 9 harbored rDNA clusters in all individuals with the occurrence of NOR activity in pair 9, suggesting ancestry or selective pressures to prevent pseudogenization of rDNA sequences in this chromosome pair. Additionally, small NORs and cryptic rDNA loci were observed. Finally, there was no evidence of enrichment and association of transposable elements, at least, inside or nearby rDNA cistron. These findings broaden our knowledge of rDNA dynamics, revealing an independent movement and amplification of segments of 45S rDNA cistron, which in A. flavolineata could be attributed to ectopic recombination.

The Bluetongue virus appears to be restricted in Argentina to the northeastern area of the country. In the Neotropical region the main vector could be Culicoides insignis Lutz. This study was aimed to determine the population fluctuation of C. insignis in Posadas city and test the influence of climatic variables as determinants of the abundance of this species. The specimens were collected in Posadas city using CDC light traps from January to December 2013. The abundance of C. insignis in relation to environmental variables was analyzed using multivariate linear regression. A total of 2,952 specimens of C. insignis were collected representing 93.4% of the total Culicoides captured. The multivariate linear regression analyses show that the monthly mean relative humidity was the variable that best explained the population dynamics of C. insignis in the work area. The pathogen transmission is probably influenced by the abundance of the vector in this area. The population peaks observed are indicative of periods when there should be more control to prevent transmission of the disease. This is the first report of population fluctuation of C. insignis in northeastern Argentina.

Neo-sex chromosome systems arose independently multiple times in evolution, presenting the remarkable characteristic of repetitive DNAs accumulation. Among grasshoppers, occurrence of neo-XY was repeatedly noticed in Melanoplinae. Here we analyzed the most abundant tandem repeats of R. bergii (2n = 22, neo-XY♂) using deep Illumina sequencing and graph-based clustering in order to address the neo-sex chromosomes evolution.

Additional parasitic elements known as B chromosomes have been described in approximatey 15% of eukaryotic species. They have primary characteristics that define their origin, composition, ways of accumulation and evolution, such as irregular modes of inheritance, pairing incapacity with standard A chromosomes during meiosis and accumulation of distinct repetitive DNAs. The grasshopper Abracris flavolineata presents diploid number 2n = 23, X0 (male) and 2n = 24, XX (female) and presence of one or two B submetacentric chromosomes were reported exclusively in Rio Claro/SP population, varying in frequency temporally from 13.5% to 31.5% in males. In this work aiming to understand the spatial variation of B chromosome we investigated presence and frequency of B chromosomes in males belonging to three populations, Santa Bárbara do Pará/PA, Cabo/PE and Posadas/Misiones/Argentina using 61, 19 and 14 individuals, respectively. For Argentina population the frequency estimated was only 7,14% (one individual), while for Pernambuco it was higher with about 21,05% (four individuals), and for Pará none of the individuals presented B chromosomes. None of the populations presented individuals with 2B chromosome as reported in Rio Claro/SP, suggesting differential drive and accumulation. The fluctuation of B chromosome frequency and accumulation in these natural populations could be explained by several factors, like differences in parasitism rate, genetic drift or else by negative effects for host development. Moreover local environment characteristics, associated to possible reproductive isolation, caused by vicariance processes, could also influence B chromosome frequency variation. Here we expanded the knowledge of B chromosome geographic distribution in A. flavolineata and the next step is to check if the B chromosome is the same variant in distinct populations, using for example the U2 snDNA as probe, wich is present in the B chromosome from Rio Claro/SP population.

BACKGROUND:Satellite DNAs (satDNAs) are organized in repetitions directly contiguous to one another, forming long arrays and composing a large portion of eukaryote genomes. These sequences evolve according to the concerted evolution model, and homogenization of repeats is observed at the intragenomic level. Satellite DNAs are the primary component of heterochromatin, located primarily in centromeres and telomeres. Moreover, satDNA enrichment in specific chromosomes has been observed, such as in B chromosomes, that can provide clues about composition, origin and evolution of this chromosome. In this study, we isolated and characterized a satDNA in A and B chromosomes of Abracris flavolineata by integrating cytogenetic, molecular and genomics approaches at intra- and inter-population levels, with the aim to understand the evolution of satDNA and composition of B chromosomes.RESULTS:AflaSAT-1 satDNA was shared with other species and in A. flavolineata, was associated with another satDNA, AflaSAT-2. Chromosomal mapping revealed centromeric blocks variable in size in almost all chromosomes (except pair 11) of A complement for both satDNAs, whereas for B chromosome, only a small centromeric signal occurred. In distinct populations, variable number of AflaSAT-1 chromosomal sites correlated with variability in copy number. Instead of such variability, low sequence diversity was observed in A complement, but monomers from B chromosome were more variable, presenting also exclusive mutations. AflaSAT-1 was transcribed in five tissues of adults in distinct life cycle phases.CONCLUSIONS:The sharing of AflaSAT-1 with other species is consistent with the library hypothesis and indicates common origin in a common ancestor; however, AflaSAT-1 was highly amplified in the genome of A. flavolineata. At the population level, homogenization of repeats in distinct populations was documented, but dynamic expansion or elimination of repeats was also observed. Concerning the B chromosome, our data provided new information on the composition in A. flavolineata. Together with previous results, the sequences of heterochromatic nature were not likely highly amplified in the entire B chromosome. Finally, the constitutive transcriptional activity suggests a possible unknown functional role, which should be further investigated.

Eligmodontia is a genus of phyllotine rodents adapted to arid environments with seven recognized species. The sister species E. puerulus and E. moreni are distributed in the adjacent highland Puna and lowland Monte deserts respectively, and show remarkable morphological and chromosomal differences. However, analyses of the cytochrome b gene showed important variability, without reciprocal monophyly between them. In order to study the evolutionary processes involved in the diversification of both taxa, we analyzed 1161 bp of the mitochondrial control region and flanking sequences (N = 60), as well as 759 bp of the first exon of the nuclear gene IRBP (N = 14). Individuals of both species from Jujuy, Catamarca and Mendoza Provinces of Argentina were previously karyotyped. Results showed that the mitochondrial sequences present high haplotype and nucleotide diversity within all population, and no haplotype was shared between both species. FST indicated that populations of both species were moderately structured. The network was constituted by two major haplogroups, one composed by E. puerulus samples from Jujuy, and the other composed of sequences of all studied populations. The Bayesian analysis showed three clusters, matching the network. Phylogenetic analysis recovered two clades with high support, in coincidence with the network groups. There was only one close join between sequences of both species, corresponding to samples from Catamarca. Thus, mitochondrial data suggested hybridization between both species in Catamarca, with asymmetric introgression. The IRBP showed low variability and, in the phylogenetic analysis, the sequences of E. puerulus form a monophyletic group with intermediate support, whereas those of E. moreni collapse into a basal polytomy. Our data indicated a recent divergence and absence of introgression in the nuclear genomes. The results at the population level with mitochondrial sequences, together with integrative taxonomy at the species level in a biogeographic context, suggest that climatic and geologic changes could have had an important role in the determination of genetic variability patterns observed in these rodents.

In an attempt to track the chromosomal differentiation in the Dichroplus elongatus species group, we analyzed the karyotypes of four species with classical cytogenetic and mapping several multigene families through fluorescent in situ hybridization (FISH). We improved the taxon sampling of the D. elongatus species group adding new molecular data to infer the phylogeny of the genus and reconstruct the karyotype evolution. Our molecular analyses recovered a fully resolved tree with no evidence for the monophyly of Dichroplus. However, we recovered several stable clades within the genus, including the D. elongatus species group, under the different strategies of tree analyses (Maximum Parsimony and Maximum Likelihood). The chromosomal data revealed minor variation in the D. elongatus species group's karyotypes caused by chromosome rearrangements compared to the phylogenetically related D. maculipennis species group. The karyotypes of D. intermedius and D. exilis described herein showed the standard characteristics found in most Dichroplini, 2n = 23/24, X0♂ XX♀, Fundamental number (FN) = 23/24. However, we noticed two established pericentric inversions in D. intermedius karyotype, raising the FN to 27♂/28♀. A strong variation in the heterochromatic blocks distribution was evidenced at interespecific level. The multigene families' mapping revealed significant variation, mainly in rDNA clusters. These variations are probably caused by micro chromosomal changes, such as movement of transposable elements (TEs) and ectopic recombination. These observations suggest a high genomic dynamism for these repetitive DNA sequences in related species. The reconstruction of the chromosome character "variation in the FN" posits the FN = 23/24 as the ancestral state, and it is hypothesized that variations due to pericentric inversions has arisen independently three times in the evolutionary history of Dichroplus. One of these independent events occurred in the D. elongatus species group, where D. intermedius is the unique case with the highest FN described in the tribe Dichroplini.

We present here the physical mapping of the 5S rDNA locus in six wild and five cultivated taxa of Capsicum by means of a genus-specific FISH probe. In all taxa, a single 5S locus per haploid genome that persistently mapped onto the short arm of a unique metacentric chromosome pair at intercalar position, was found. 5S FISH signals of almost the same size and brightness intensity were observed in all the analyzed taxa. This is the first cytological characterization of the 5S in wild taxa of Capsicum by using a genus-derived probe, and the most exhaustive and comprehensive in the chili peppers up to now. The information provided here will aid the cytomolecular characterization of pepper germplasm to evaluate variability and can be instrumental to integrate physical, genetic and genomic maps already generated in the genus.