Published May 6, 2022 | Version v1
Dataset Open

Sperm limitation produces male biased family sex ratios


Haplo-diploid sex determination in the parasitoid wasp, Nasonia vitripennis (Walker), allows females to adjust their brood sex ratios. Females influence whether ova are fertilized, producing diploid females, or remain unfertilized, producing haploid males. Females appear to adjust their brood sex ratios to minimize "local mate competition," i.e., competition among sons for mates. Because mating occurs between siblings, females may optimize mating opportunities for their offspring by producing only enough sons to inseminate daughters when ovipositing alone and producing more sons when superparasitism is likely. Although widely accepted, this hypothesis makes no assumptions about gamete limitation in either sex. Because sperm is used to produce daughters, repeated oviposition could reduce sperm supplies, causing females to produce more sons. In contrast, if egg-limited females produce smaller broods, they might use fewer sperm, making sperm limitation less likely. To investigate whether repeated oviposition and female fertility influence gamete limitation within females, we created two treatments of six mated female wasps, which received a series of six hosts at intervals of 24 or 48 hrs. All females produced at least one mixed-sex brood (63 total broods; 3,696 offspring). As expected, if females became sperm limited, in both treatments, brood sex ratios became increasingly male-biased with increasing host number. The interhost interval did not affect brood size, total offspring number or sex ratio, indicating females did not become egg limited. Our results support earlier studies showing sperm depletion affects sex allocation in N. vitripennis¸ and could limit adaptive sex ratio manipulation in these parasitoid wasps.


The dataset from Holditch et al. (2022, attached) contains brood data from an oviposition series produced by 12 different Nasonia vitripennis females. We report the total number of male and female offspring and sex ratio for each of six host pupae (Sarcophaga bullata), which were distributed to mated female wasps at varying intervals (i.e., every 24 or 48 hrs).

The first row identifies information for each column. Each row contains data for a brood produced by a single female, on a single host. The interval at which females received unparasitized host pupae is given in Column 1 (i.e., 24 or 48 hrs). Individual females are distinguished by a lowercase letter in Column 2 (i.e., Female Identity). The six host pupae provided to females during the experiment are identified by Host Order (1-6) in Column 3.

Host pupae that females successfully parasitized (i.e., yielded >1 offspring) are identified in Column 4 under Host Number. The total number of male and female offspring counted in each host is given in Columns 5 and 6 (i.e., Nmales and Nfemales, respectively). Wasp offspring which could not be identified to either sex are counted in Column 7, (i.e., Nunknown). Brood size for each host is given in Column 8, and is the sum of Nmales, Nfemales, and Nunknown. Finally, Column 9 contains the brood sex ratio and is calculated as the proportion of males within the brood.

Funding provided by: Undergraduate Research Mentoring Program (URM) NAU*
Crossref Funder Registry ID:
Award Number:

Funding provided by: Initiative for Maximizing Student Development (IMSD) NAU*
Crossref Funder Registry ID:
Award Number:

Funding provided by: J. O. Wolff Distinguished Faculty Award NAU*
Crossref Funder Registry ID:
Award Number:


Files (25.6 kB)

Name Size Download all
11.8 kB Download
13.8 kB Download