Biology subjects

Yeh, S.-D.

Publications and source records attributed to Yeh, S.-D..

4 recordsLinked to original sources

bioRxiv2025

Natural variation in pigmentation caused by cis-regulatory changes affecting expression of the ebony gene in Drosophila elegans

Repetitive evolution has offered valuable insights into how similar traits can arise across different populations and species. The dimorphic body color morphs (brown and black) of geographically isolated Drosophila elegans Bock & Wheeler, 1972, along with its closely related species Drosophila gunungcola Sultana et al., 1999, which exhibits black morph, raise intriguing questions about whether these traits have emerged through independent evolution, introgression, or shared ancestral variants. To investigate the genetic and evolutionary origins of these differences, we perform quantitative trait locus (QTL) mapping on recombinant hybrids generated from reciprocal crosses between brown and black morphs D. elegans. QTL mapping reveals significant contributions from the X chromosome and Muller element E to intraspecific pigmentation polymorphism, with ebony identified as one candidate gene. Analysis of ebony expression, including allele-specific expression in F1 hybrids, and sequence variation suggests that the intra- and interspecific pigmentation differences within D. elegans species subgroup may have evolved independently from the lineage-specific region upstream of ebony. By identifying a shared candidate regulatory region associated with both intra- and interspecific variation, our findings suggest that recurrent use of the same genetic region may contribute to the emergence of similar traits across populations and species.

evolutionary biology↗

bioRxiv2019

Co-evolving wing spots and mating displays are genetically separable traits in Drosophila

The evolution of sexual traits often involves correlated changes in morphology and behavior. For example, in Drosophila, divergent mating displays are often accompanied by divergent pigment patterns. To better understand how such traits co-evolve, we investigated the genetic basis of correlated divergence in wing pigmentation and mating display between the sibling species Drosophila elegans and D. gunungcola. Drosophila elegans males have an area of black pigment on their wings known as a wing spot and appear to display this spot to females by extending their wings laterally during courtship. By contrast, D. gunungcola lacks both of these traits. Using Multiplexed Shotgun Genotyping (MSG), we identified a [~]440 kb region on the X chromosome that behaves like a genetic switch controlling the presence or absence of male-specific wing spots. This region includes the candidate gene optomotor-blind (omb), which plays a critical role in patterning the Drosophila wing. The genetic basis of divergent wing display is more complex, with at least two loci on the X chromosome and two loci on autosomes contributing to its evolution. Introgressing the X-linked region affecting wing spot development from D. gunungcola into D. elegans reduced pigmentation in the wing spots but did not affect the wing display, indicating that these are genetically separable traits. Consistent with this observation, broader sampling of wild D. gunungcola populations confirmed the wing spot and wing display are evolving independently: some D. gunungcola males preformed wing displays similar to D. elegans despite lacking wing spots. These data suggest that correlated selection pressures rather than physical linkage or pleiotropy are responsible for the coevolution of these morphological and behavioral traits. They also suggest that the change in morphology evolved prior to the change in behavior.

evolutionary biology↗

bioRxiv2018

Tempo, mode, and fitness effects of mutation in Caenorhabditis elegans over 400 generations of minimal selection

The mutational process varies at many levels, from within genomes to among taxa. Many mechanisms have been linked to variation in mutation, but understanding of the evolution of the mutational process is rudimentary. Physiological condition is often implicated as a source of variation in microbial mutation rate and may contribute to mutation rate variation in multicellular organisms.\n\nDeleterious mutations are a ubiquitous source of variation in condition. We test the hypothesis that the mutational process depends on the underlying mutation load in two groups of Caenorhabditis elegans mutation accumulation (MA) lines that differ in their starting mutation loads. \"First-Order MA\" (O1MA) lines maintained under minimal selection for [~]250 generations were divided into high-fitness and low-fitness groups and sets of \"second-order MA\" (O2MA) lines derived from each O1MA line were maintained for [~]150 additional generations. Genomes of 48 O2MA lines and their progenitors were sequenced. There is significant variation among O2MA lines in base-substitution rate ({micro}bs), but no effect of initial fitness, whereas the indel rate is greater in high-fitness O2MA lines. Overall, {micro}bs is positively correlated with recombination and proximity to short tandem repeats and negatively correlated with 10 bp and 1 Kb GC content. However, probability of mutation is well-predicted by the three-nucleotide motif. [~]90% of the variance in standing nucleotide variation is explained by mutability. Total mutation rate increased in the O2MA lines, as predicted by the \"drift barrier\" model of mutation rate evolution. These data, combined with experimental estimates of fitness, suggest that epistasis is synergistic.

evolutionary biology↗

bioRxiv2017

The mutational decay of male and hermaphrodite competitive fitness in the androdioecious nematode C. elegans, in which males are naturally rare

Androdioecious Caenorhabditis have a high frequency of self-compatible hermaphrodites and a low frequency of males. The effects of mutations on male fitness are of interest for two reasons. First, when males are rare, selection on male-specific mutations is less efficient than in hermaphrodites. Second, males may present a larger mutational target than hermaphrodites because of the different ways in which fitness accrues in the two sexes.\n\nWe report the first estimates of male-specific mutational effects in an androdioecious organism. The rate of male-specific inviable or sterile mutations is [≤] 5 x 10-4/generation, below the rate at which males would be lost solely due to those kinds of mutations. The rate of mutational decay of male competitive fitness is ~0.17%/generation; that of hermaphrodite competitive fitness is ~0.11%/generation. The point estimate of ~1.5X faster rate of mutational decay of male fitness is nearly identical to the same ratio in Drosophila. Estimates of mutational variance (VM) for male mating success and competitive fitness are not significantly different from zero, whereas VM for hermaphrodite competitive fitness is similar to that of non-competitive fitness. The discrepancy between the two sexes is probably due to the greater inherent variability of mating relative to internal self-fertilization.

evolutionary biology↗