Biology subjects

Sharma, M. D.

Publications and source records attributed to Sharma, M. D..

6 recordsLinked to original sources

bioRxiv2025

No association between metabolic rate and an exaggerated sexually selected trait

Exaggerated sexually selected traits are thought to be energetically costly to produce and to maintain. This is especially true of sexually selected weapons, traits that are frequently positively allometric, and therefore likely to be especially energetically costly. However, there have been few studies that directly measure these putative costs. Additionally, metabolic rate, a measure of energy expenditure, is highly variable across individuals, but the causes of this variation are not always well established. Here we tested for the associations between resting metabolic rate, during development and adulthood, and the size of a weapon used during adult male-male competition in the beetle Gnatocerus cornutus. We also tested for genetic variation metabolic rate and weapon size. We found that metabolic rate was not statistically associated with weapon size, but there were effects of genotype and mass during development (pupal size) on weapons. Additionally, age, mass and genotype all affected metabolic rate in various ways. Despite no evidence of energetic costs to weapon development or maintenance, direct predation costs associated with them have been detected previously, and hence enlarged weapons are costly in this system. Significance statementThe large weapons used in competition between males are thought to be energetically costly. However, there are rather few investigations of these putative costs. We investigate these potential costs by testing for associations between metabolic rate and weapon size in a beetle. We found no relationship between weapons and metabolism, indicating weapons are not always energetically costly.

ecology↗

bioRxiv2024

Automated detection of Bornean white-bearded gibbon (Hylobates albibarbis) vocalisations using an open-source framework for deep learning

Passive acoustic monitoring is a promising tool for monitoring at-risk populations of vocal species, yet extracting relevant information from large acoustic datasets can be time-consuming, creating a bottleneck at the point of analysis. To address this, we adapted an open-source framework for deep learning in bioacoustics to automatically detect Bornean white-bearded gibbon (Hylobates albibarbis) "great call" vocalisations in a long-term acoustic dataset from a rainforest location in Borneo. We describe the steps involved in developing this solution, including collecting audio recordings, developing training and testing datasets, training neural network models, and evaluating model performance. Our best model performed at a satisfactory level (F score = 0.87), identifying 98% of the highest-quality calls from 90 hours of manually-annotated audio recordings and greatly reduced analysis times when compared to a human observer. We found no significant difference in the temporal distribution of great call detections between the manual annotations and the models output. Future work should seek to apply our model to long-term acoustic datasets to understand spatiotemporal variations in H. albibarbis calling activity. Overall, we present a roadmap for applying deep learning to identify the vocalisations of species of interest which can be adapted for monitoring other endangered vocalising species.

ecology↗

bioRxiv2023

Manipulating multi-level selection in a fungal entomopathogen reveals social conflicts and a method for improving biocontrol traits

Changes in parasite virulence are commonly expected to lead to trade-offs in other life history traits that can affect fitness. Understanding these trade-offs is particularly important if we want to manipulate the virulence of microbial biological control agents. Theoretically, selection across different spatial scales, i.e. between- and within-hosts, shapes these trade- offs. However, trade-offs are also dependent on parasite biology. Despite their applied importance the evolution of virulence in fungal parasites is poorly understood: virulence can be unstable in culture and commonly fails to increase in simple passage experiments. We hypothesized that manipulating selection intensity at different scales would reveal virulence trade-offs in a fungal pathogen of aphids, Akanthomyces muscarius. Starting with a genetically diverse stock we selected for infectivity, parasite yield or speed of kill by manipulating competition within and between hosts and between groups of hosts over 7 rounds of infection. We characterized ancestral and evolved lineages by whole genome sequencing and by measuring virulence, growth rate, sporulation and fitness. While several lineages showed increases in virulence, we saw none of the trade-offs commonly found in obligately-killing parasites. Phenotypically similar lineages within treatments often shared multiple single-nucleotide variants, indicating strong convergent evolution. The most dramatic phenotypic changes were in timing of sporulation and spore production in vitro. We found that early sporulation led to reduced competitive fitness but could increase yield of spores on media, a trade-off characteristic of social conflict. Notably, the selection regime with strongest between-group competition and lowest genetic diversity produced the most consistent shift to early sporulation, as predicted by social evolution theory. Mutli-level selection therefore revealed social interactions novel to fungi and showed that these biocontrol agents have the genomic flexibility to improve multiple traits -virulence and spore production - that are often in conflict in other parasites. Author summaryUnderstanding the ecological forces that shape virulence is a key challenge in evolutionary biology. Here we investigated how competition at different levels of selection (within-hosts, between-hosts, between populations) could alter investment in virulence in a fungal entomopathogen. We predicted that cooperative investment in virulence would increase at higher scales of competition and aimed to further our understanding of potential trade-offs shaping life-history of a fungal insect pathogens. We found moderate increases in virulence in different selection regimes but importantly, none of the commonly expected trade-offs, such as that between spore production and virulence or a relationship between virulence and growth rate, which is consistent with cooperation. However, we found convergent genetic changes and significant differences in timing and production of spores, dependent how we manipulated scales of selection. Our data suggests that this is driven by social conflict regarding the timing of sporulation. This carries fundamental importance for understanding how varying selection pressure at different scales shape pathogen life history. In addition, these results also have applied importance for understanding how to improve and select for beneficial traits in biocontrol agents.

evolutionary biology↗

bioRxiv2020

Natural selection reverses the exaggeration of a male sexually selected trait, which increases female fitness.

Theory shows how sexual selection can exaggerate male traits beyond naturally selected optima and also how natural selection can ultimately halt trait elaboration. Empirical evidence supports this theory, but to date, there have been no experimental evolution studies directly testing this logic, and little examination of possible associated effects on female fitness. Here we used experimental evolution of replicate populations of broad-horned flour-beetles to test for evolutionary effects of sex-specific predation on an exaggerated sexually selected male trait, while also testing for effects on female lifetime reproductive success. We found that populations subjected to male-specific predation evolved smaller sexually selected traits and this indirectly increased female fitness, seemingly through intersexual genetic correlations we documented. Predation solely on females had no effects. Our findings support fundamental theory, but also reveal novel outcomes when natural selection targets sex-limited sexually selected characters.

evolutionary biology↗

bioRxiv2019

De novo genome assembly of the meadow brown butterfly, Maniola jurtina

BackgroundMeadow brown butterflies (Maniola jurtina) on the Isles of Scilly represent an ideal model in which to dissect the links between genotype, phenotype and long-term patterns of selection in the wild - a largely unfulfilled but fundamental aim of modern biology. To meet this aim, a clear description of genotype is required.\n\nFindingsHere we present the draft genome sequence of M. jurtina to serve as an initial genetic resource for this species. Seven libraries were constructed using DNA from multiple wild caught females and sequenced using Illumina, PacBio RSII and MinION technology. A novel hybrid assembly approach was employed to generate a final assembly with an N50 of 214 kb (longest scaffold 2.9 Mb). The genome encodes a total of 36,294 genes. 90.3% and 88.7% of core BUSCO (Benchmarking Universal Single-Copy Orthologs) Arthropoda and Insecta gene sets were recovered as complete single-copies from this assembly. Comparisons with 17 other Lepidopteran species placed 86.5% of the assembled genes in orthogroups.\n\nConclusionsOur results provide the first high-quality draft genome and annotation of the butterfly M. jurtina.

genomics↗

bioRxiv2018

Changes in temperature alter susceptibility to a virus following a host shift

Host shifts - where a pathogen jumps between different host species - are an important source of emerging infectious disease. With ongoing climate change there is an increasing need to understand the effect changes in temperature may have on emerging infectious disease. We investigated whether species susceptibilities change with temperature and ask if susceptibility is greatest at different temperatures in different species. We infected 45 species of Drosophilidae with an RNA virus and measured how viral load changes with temperature. We found the host phylogeny explained a large proportion of the variation in viral load at each temperature, with strong phylogenetic correlations between viral loads across temperature. The variance in viral load increased with temperature, whilst the mean viral load did not, such that as temperature increased the most susceptible species become more susceptible, and the least susceptible less so. We found no significant relationship between a species susceptibility across temperatures and proxies for thermal optima; critical thermal maximum and minimum or basal metabolic rate. These results suggest that whilst the rank order of species susceptibilities can remain the same with changes in temperature, the likelihood of host shifts into a given species may increase or decrease.\n\nAuthor SummaryEmerging infectious diseases are often the result of a host shift, where a pathogen jumps from one host species into another. Understanding the factors underlying host shifts is a major goal for infectious disease researchers. This effort has been further complicated by the fact that host-parasite interactions are now taking place in a period of unprecedented global climatic warming. Here, we ask how host shifts are affected by temperature by carrying out experimental infections using an RNA virus across a wide range of related species, at three different temperatures. We find that as temperature increases the most susceptible species become more susceptible, and the least susceptible less so. This has important consequences for our understanding of host shift events in a changing climate, and suggests that temperature changes may affect the likelihood of a host shift into certain species.

evolutionary biology↗