Strong variation in frequencies of male and female determiners between neighboring housefly populations

Abstract

Sex‐determination mechanisms evolve rapidly and vary between species. Occasionally, polymorphic systems are found, like in the housefly. Studying the dynamics and stability of such systems can provide a better understanding of the evolution of sex‐determination systems. In the housefly, dominant male‐determining loci (M) can lie not only on the Y chromosome (MY), but also on autosomes (MA) or the X chromosome (MX). M enforces male development by inhibiting the female‐determining gene transformer (tra). A mutant tra allele, traD, is insensitive to M and is a dominant female determiner. MY prevails at high latitudes and polymorphic M loci together with traD at low latitudes. To get more insight into the stability and frequencies of these sex determiners with mutually exclusive dominance, we investigated 5 regional Spanish populations. We found strong variation among populations. Two populations with hemizygous MIII were found, 2 contained homozygous MX with additional hemizygous MI and MII in 1 population. One population contained homozygous and hemizygous MX with additionally hemizygous MII. All females in populations with homozygous M, had traD, whereas no traD was found in populations without homozygous M. Our results indicate locally stable systems may either harbor a single hemizygous M and no traD, corresponding to a male heterogametic system, or homozygous and/or multiple M and heterozygous traD, reminiscent of a female heterogametic system. They support that M loci can accumulate in the presence of a dominant female determiner. Limited migration between populations may contribute to the stability of these systems.

Frequencies of house fly proto-Y chromosomes across populations are predicted by temperature heterogeneity within populations

“…This discrepancy between our observations and prior measurements from California can likely be explained by a >50 km distance between our site and the previous sampling locations. Similar differences in the frequencies of house fly male-determining chromosomes have been observed over relatively short distances in Japan and Spain (Tomita and Wada 1989; Li et al 2022) . Therefore, small-scale variations in Y M and III M frequencies appear to be a global phenomenon, in addition to the large-scale variation observed across the entire continent (Figure 2) .…”

Adult sex ratios affect mating behaviour in the common housefly Musca domestica L. (Diptera; Muscidae)

“…Moreover, male seminal fluid proteins are associated with increased female fecundity and lifespan (Arnqvist & Andrés, 2006). Adult sex ratios may vary in natural housefly populations (Feldman-Muhsam, 1944) and interpopulation crosses can cause strong sex ratio biases as populations differ in the number and composition of male and female sex determiners (Feldmeyer et al, 2008;Kozielska et al, 2008;Pastor et al, 2014;Hamm et al, 2015;Li et al, 2022). Houseflies also display protandry, the faster development and earlier emergence of males compared to females (L. Francuski, data not shown).…”