Martijn Schenkel
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martijnschenkel.bsky.social
Martijn Schenkel
@martijnschenkel.bsky.social
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Evolutionary biologist with an interest in conflicts, unusual genetics, sex, and all the other funny things that make biology tick | Postdoc at Wagening University | STN Internal Conflicts & Organismal Adaptation https://internalconflictsstn.wordpress.com
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martijnschenkel.bsky.social
Join us this Friday at 13:00 UTC for the first Internal Conflicts STN seminar of this academic year, featuring Laurence Hurst and Phil Madgwick! Details via internalconflictsstn.wordpress.com/seminars/, also on several upcoming seminars.
Information on the seminar, with pictures of Laurence Hurst (left) and Phil Madgwick (right).
September 15, 2025 at 9:23 AM
martijnschenkel.bsky.social
Wonder if Bruce Wallace liked his dean.

From: B. Wallace (1975). Hard and soft selection revisited. Evolution 29:465-473.
Excerpt from a 1975 paper by Bruce Wallace which reads: "The relative ease with which homozygous mutant flies can be maintained in stock cultures fails to reflect the low survival values these same genotypes would exhibit were they to develop together with wild-type flies in a single culture bottle. In many respects an adult fly resembles the Dean of the Faculty at a university: the positions exists and needs filling; the creation of a dean does not require, however, the existence of faculty members with deanlike qualities because the position will be filled in any case."
July 16, 2025 at 8:24 AM
martijnschenkel.bsky.social
Join us tomorrow at 8:00 UTC (10:00 CEST) for the next Internal Conflicts STN seminar! Talks by Perran Stott Ross and Filip Husnik. For Zoom link + more info see internalconflictsstn.wordpress.com/seminars/
Overview of meeting details for the next Internal Conflicts STN seminar by Perran Stott Ross and Filip Husnik.
April 29, 2025 at 11:22 AM
martijnschenkel.bsky.social
This gets even worse when we compare the same trend across other places. Some Friday afternoon fun. Oh, such are the joys of postdoc life...
Series of graphs showing trends in the number of positions posted on ecoevojobs.net across 2020-2024. Both 2020 (pandemic) and 2024 show reduced numbers across various continents.
December 13, 2024 at 2:41 PM
martijnschenkel.bsky.social
Lab trip with the Kokkonuts @kokkonut.bsky.social @shikharabhat.bsky.social @tom-is-kean.bsky.social et al to Berlin was great fun! Definitely worth coming back in the future 👍😋
November 28, 2024 at 8:42 AM
martijnschenkel.bsky.social
These peculiar dynamics stem from an unconventional synergy between Distorter, Assister, and the Y-chromosome. [7/12]
A2 experiences fitness benefits by preferentially segregating to males under each evolutionary scenario for Assister. Sexual antagonism (SA): A2 confers a fitness benefit so that male bearers have higher-than-average fitness (w), whereas female bearers have lower-than-average fitness. Male-limited cis-segregation distortion (SD): A2 has a higher-than-Mendelian transmission (p) in males, but regular Mendelian transmission in females. Parental antagonism (PA): A2 confers a fitness benefit to its bearers when paternally inherited so that they have higher-than-average fitness, whereas it confers a fitness cost when maternally-inherited. (B) A2 and D2 each benefit from the other. A2 provides D2 a fitness or transmission benefit, and D2 provides A2 a “destination benefit,” i.e. indirectly delivers it to a destination where it fares better (i.e., in a male). This synergy is responsible for the gene frequency changes we observe.
November 22, 2024 at 12:54 PM
martijnschenkel.bsky.social
Under the second, we consider that only the X-chromosome is eliminated from any X-bearing sperm, converting them to 0-bearing sperm. This brings about a sex determination transition from XY to X0 sex determination (and again a biased sex ratio). [6/12]
Dynamics and scope of 0-chromosome drive via the trans-acting Distorter causing X-conversion, linked to a male-limited meiotic driver Assister. (A) Changes in the allele frequency of A2, D2, and the X-, Y-, and 0-chromosome across 500 generations. (B) Changes in the linkage disequilibrium of Assister-Distorter, Assister-XY, and Distorter-XY across 500 generations. (C) Haplotype frequencies over 500 generations. A1D2X and A1D2Y are near-zero, as D2 is introduced on an A2 background and recombination is low. The shaded area represents the frequency of D2 and primarily comprises the haplotypes A2D20 and A2D2X. (D) D2 equilibrium frequency after 1,000 generations. (E) Population sex ratio after 1,000 generations. Parameter values (if not otherwise defined): k_D=0.25,k_A=0.25,h_A= 0.5,z = 0.01,r = 0.001,w = 0.01.
November 22, 2024 at 12:54 PM
martijnschenkel.bsky.social
We show that Distorter can invade when it is linked to a nearby gene Assister that experiences optimal fitness in males (e.g. sexual antagonism). [4/12]
Dynamics and scope of Y-chromosome drive via the trans-acting Distorter. Here, Distorter is linked to a sexually antagonistic Assister locus and causes drive via the X-shredding mechanism. (A) Changes in the frequency of the A2¬ and D2 alleles and the X and Y chromosomes across 500 generations. (B) Changes in the linkage disequilibrium of Assister-Distorter, Assister-XY, and Distorter-XY across 500 generations. (C) Haplotype frequencies over 500 generations. A1D2X and A1D2Y are near-zero, as D2 is introduced on an A2 background and recombination is low. The shaded area represents the frequency of D2 and primarily comprises the haplotypes A2D2Y and A2D2X. (D) D2 equilibrium frequency after 1,000 generations. (E) Population sex ratio after 1,000 generations. Parameter values (if not otherwise specified): k_D=0.25,s,t=0.5,h_A=0.5,z=0.01,r=0.001.
November 22, 2024 at 12:54 PM
martijnschenkel.bsky.social

We model an autosomal segregation distorter (Distorter) that targets the X-chromosome to cause biased transmission of the Y- or even 0-chromosome, resulting in “remote control” drive. Effectively, Distorter acts in trans to meddle with segregation. [3/12]
Model overview. (A) Our model incorporates two linked autosomal loci, Assister (with alleles A¬1 and A2) and Distorter (with alleles D¬1 and D2); recombination between Assister and Distorter occurs at a rate r in both sexes. Assister may represent either a sexually antagonistic locus (A1 beneficial in females/detrimental in males, A2 detrimental in females/beneficial in males) or a locus experiencing cis-segregation distortion (D2 overtransmitted in D1/D2 heterozygotes). The D2 allele interferes with the Mendelian transmission of the X-, Y-, and/or O-chromosomes during spermatogenesis to achieve trans¬-segregation distortion.
November 22, 2024 at 12:54 PM