Biology subjects

Torres, T. T.

Publications and source records attributed to Torres, T. T..

6 recordsLinked to original sources

bioRxiv2024

Demographic and Historical Processes Influencing Cochliomyia hominivorax (Diptera: Calliphoridae) Population Structure across South America

BackgroundThis study investigates the genetic variability and population structure of Cochliomyia hominivorax, the New World screwworm fly. This study tested the hypothesis that the species exhibits a center-periphery distribution of genetic variability, with higher genetic diversity in central populations (e.g., Brazil) and lower diversity in peripheral populations. MethodsUtilizing microsatellite markers, we analyzed larvae collected from infested livestock across South America. Larvae were collected directly from various wound sites to ensure a broad representation of genetic diversity. ResultsContrary to our initial hypothesis, the results revealed consistent genetic variability across the species distribution, low population differentiation, and no evidence of isolation-by-distance patterns among subpopulations. The genetic analysis indicated an excess of homozygotes, potentially due to the Wahlund effect, null alleles, or selection pressure. ConclusionsThese findings suggest a complex metapopulation structure for Co. hominivorax, challenging classical population genetics models. This complexity likely arises from the species high dispersal capability and frequent local extinctions followed by recolonization. These results have important implications for the design and implementation of control programs, emphasizing the need for coordinated and large-scale actions rather than isolated initiatives.

genetics↗

bioRxiv2022

Molecular and developmental signatures of genital size macro-evolution in bugs

With the advance of the evo-devo research program, our understanding of the genes and pathways that determine the architecture of novel traits has experienced drastic growth. Nevertheless, single-species approaches are insufficient to understand the processes by which evolution shapes morphological changes after their emergence. As such, we still have an elusive knowledge of how these genetic-developmental architectures evolve themselves for most of the structures, as well as how their evolution is mirrored in the phenotypic change across large time scales. Here, we tackle this gap by reconstructing the evolution of male genital size, one of the most complex traits in insects, together with its underlying genetic architecture. Using the order Hemiptera as a model, which spans over 350 million years of evolution, we estimate the correlation between genital size and three features: development rate, body size, and rates of DNA substitution in 68 genes previously associated with genital development. We demonstrate that genital size macro-evolution has been largely dependent on body size and weakly influenced by development rate and the phylogenetic history. Our results further revealed positive correlations between mutation rates and genital size for 18 genes. Interestingly, there is great diversity in the function of these genes, in the signaling pathways that they participate in, and in the specific genital parts that they control. These results suggest that fast genital size evolution has been enabled by molecular changes associated with diverse morphogenetic processes, such as cuticle composition, patterning of sensory apparatus, and organ growth itself. Our data further demonstrate that the majority of DNA evolution correlated with the genitalia has been shaped by negative selection or neutral evolution. This indicates that genital changes are predominantly facilitated by relaxation of constraints rather than positive selection, possibly due to the high pleiotropic nature of the morphogenetic genes.

evolutionary biology↗

bioRxiv2021

Supergene formation is associated with a major shift in genome-wide patterns of diversity in a butterfly

Selection shapes genetic diversity around target mutations, yet little is known about how selection on specific loci affects the genetic trajectories of populations, including their genome-wide patterns of diversity and demographic responses. Here we study the patterns of genetic variation and geographic structure in a neotropical butterfly, Heliconius numata, and its closely related allies in the so-called melpomene-silvaniform clade. H. numata is known to have evolved an inversion supergene which controls variation in wing patterns involved in mimicry associations with distinct groups of co-mimics whereas it is associated to disassortative mate preferences and heterozygote advantage at this locus. We contrasted patterns of genetic diversity and structure 1) among extant polymorphic and monomorphic populations of H. numata, 2) between H. numata and its close relatives, and 3) between ancestral lineages. We show that H. numata populations which carry the inversions as a balanced polymorphism show markedly distinct patterns of diversity compared to all other taxa. They show the highest genetic diversity and effective population size estimates in the entire clade, as well as a low level of geographic structure and isolation by distance across the entire Amazon basin. By contrast, monomorphic populations of H. numata as well as its sister species and their ancestral lineages all show lower effective population sizes and genetic diversity, and higher levels of geographical structure across the continent. One hypothesis is that the large effective population size of polymorphic populations could be caused by the shift to a regime of balancing selection due to the genetic load and disassortative preferences associated with inversions. Testing this hypothesis with forward simulations supported the observation of increased diversity in populations with the supergene. Our results are consistent with the hypothesis that the formation of the supergene triggered a change in gene flow, causing a general increase in genetic diversity and the homogenisation of genomes at the continental scale.

evolutionary biology↗

bioRxiv2020

De novo construction of a transcriptome for the stink bug crop pest Chinavia impicticornis during late development

Chinavia impicticornis is a Neotropical stink-bug (Hemiptera: Pentatomidae) with economic importance for different crops. Little is known about the development of the species, as well as the genetic mechanisms that may favor the establishment of populations in cultivated plants. Here we conduct the first large-scale molecular study with C. impicticornis. We generated RNA-seq data for males and females, at two immature stages, for the genitalia separately and for the rest of the body. We assembled the transcriptome and conduct a functional annotation. De novo assembled transcriptome based on whole bodies and genitalia of males and females contained around 400,000 contigs with an average length of 688 bp. After pruning duplicated sequences and conducting a functional annotation, the final annotated transcriptome comprised 39,478 transcripts of which 12,665 had GO terms assigned. These novel datasets will provide invaluable data for the discovery of molecular processes related to morphogenesis and immature biology. We hope to contribute to the growing research on stink bug evo-devo as well as the development of bio-rational solutions for pest management.

genomics↗

bioRxiv2020

Innate behavior sequence progression by peptide-mediated interorgan crosstalk

Innate behaviors consist of a succession of genetically-hardwired motor and physiological subprograms that can be coupled to drastic morphogenetic changes. How these integrative responses are orchestrated is not completely understood. Here, we provide insight into these mechanisms by studying pupariation, a multi-step innate behavior of fly larvae that is critical for survival during metamorphosis. We find that the steroid-hormone ecdysone triggers parallel pupariation neuromotor and morphogenetic subprograms, which include the induction of the relaxin-peptide hormone, Dilp8, in the epidermis. Dilp8 acts on six Lgr3-positive thoracic interneurons to couple both subprograms in time and to instruct neuromotor subprogram switching during behavior. Our work reveals that interorgan feedback gates progression between subunits of an innate behavior and points to an ancestral neuromodulatory function of relaxin signaling.

animal behavior and cognition↗

bioRxiv2019

Functional genomics of the parasitic habits of blowflies and botflies

Infestation by dipterous larvae - myiasis - is a major problem for livestock industries worldwide and can cause severe economic losses. The Oestroidea superfamily is an interesting model to study the evolution of myiasis-causing flies because of the diversity of parasitism strategies among closely-related species. These flies are saprophagous, obligate parasites, or facultative parasites and can be subdivided into cutaneous, nasopharyngeal, traumatic, and furuncular. We expect that closely-related species have genetic differences that lead to the diverse parasitic strategies. To identify genes with such differences, we used gene expression and coding sequence data from five species (Cochliomyia hominivorax, Chrysomya megacephala, Lucilia cuprina, Dermatobia hominis, and Oestrus ovis). We tested whether 1,287 orthologs have different expression and evolutionary constraints under different scenarios. We found two up-regulated genes; one in species causing cutaneous myiasis that is involved in iron transportation/metabolization (ferritin), and another in species causing traumatic myiasis that responds to reduced oxygen levels (anoxia up-regulated-like). Our evolutionary analysis showed a similar result. In the Ch. hominivorax branch, we found one gene with the same function as ferritin that may be evolving under positive selection, spook. This is the first step towards understanding origins and evolution of parasitic strategy diversity in Oestroidea.

genetics↗