Data from: Reproductive transitions and sperm utilisation in a facultatively parthenogenetic stick insect
Data files
Jan 15, 2026 version files 120.89 KB
-
all_seq_daughters.csv
14.94 KB
-
hatchling_dev_time.csv
36.25 KB
-
hatchling_sex_ratio.csv
5.74 KB
-
heterozygosity_all_offspring.csv
20.01 KB
-
paternity_full_active.csv
6.59 KB
-
README.md
5.92 KB
-
switch_main_analysis_for_publication.R
31.43 KB
Abstract
Facultative parthenogenesis enables females to switch from asexual (parthenogenetic) to sexual reproduction after mating, but the process of fertilisation is poorly understood in such animals. In particular, it is not known whether switching reproductive modes requires changes in the eggs themselves, delaying the transition from laying unfertilised to fertilised eggs. Likewise, very little is known about patterns of sperm precedence in facultatively parthenogenetic females that mate with multiple males. In this study, we manipulated reproductive mode in females of the facultatively parthenogenetic stick insect Megacrania batesii. We used offspring sex ratio, fertilisation rate, and paternity analysis to investigate how females descended from distinct natural populations switch between reproductive modes and utilise sperm from different males. In the switch treatment group, females were first allowed to lay unfertilised eggs, and then paired with a male. In the non-switch treatment group, females were instead paired successively with two different males. We collected eggs laid over two successive 10-day periods after male introduction (switch treatment) or substitution (non-switch treatment). We found little difference between the treatment groups in fertilisation rate or in the number of sons produced during the first and second 10-day egg-collection. We also observed similar reproductive performance between switch and non-switch treatment groups, but females’ population of origin influenced fertilisation rate and offspring sex ratio. In the non-switch group, we found near-equal fertilisation rates by the first and second male. Our results show that M. batesii females can quickly switch from producing parthenogenetic to fertilised eggs, suggesting that this transition does not require production of distinct types of eggs. Our results also show that M. batesii females can rapidly utilise sperm from a new mate, and exhibit near-complete sperm mixing which suggests that paternity may be evenly distributed in this species.
Dataset DOI: 10.5061/dryad.5hqbzkhhd
Description of the data and file structure:
There are five main csv files (listed below).
Files and variables
File: all_seq_daughters.csv
Description: Sequenced daughters
Variables: 9
- origin_mom_type: Whether the population is Mixed-sex (reported as NMS) or All-female (reported as SAF).
- dna_extracted_date: DNA extracted date
- treat_id: Treatment group ID
- treat_grp: Treatment group names: the reproductive switch mode, represented as switch for those females paired with males throughout the experiment while non-switch for those females' initial reproductive mode was asexual.
- timing_of_eggs: E1 represents first 10-day period while E2 represents second 10-day period egg collections
- hatched_date: Hatched date for each hatchling
- sex_offspring: The sex of the hatchling, represented as F for female
- adult_hatchling: Whether extracted individuals were hatchlings or adults
- percentage_hetero: Heterozygosity level
File: hatchling_dev_time.csv
Description: Hatchling developmental time
Variables: 8
- treat_id: Treatment group ID
- treat_grp: Treatment group names: the reproductive switch mode, represented as switch for those females paired with males throughout the experiment while non-switch for those females' initial reproductive mode was asexual.
- timing_of_eggs: E1 represents first 10-day period while E2 represents second 10-day period egg collections
- sex_hatchling: The sex of the hatchling
- origin_mom_type: Whether the population is Mixed-sex (reported as NMS) or All-female (reported as SAF).
- initial_mode: Whether females' initial reproductive modes were asexual (Parthenogenetic) or sexual (Mating)
- male_id: The unique individual ID of each male individual
- dev_time: Development time (days) for each hatchling
File: hatchling_sex_ratio.csv
Description: Hatchling sex ratio
Variables: 14
- origin_mom_id: The unique individual ID of each female individual
- origin_mom_type: Whether the population is Mixed-sex (reported as NMS) or All-female (reported as SAF).
- initial_mode: Whether females' initial reproductive modes were asexual (Parthenogenetic) or sexual (Mating)
- male_id: The unique individual ID of each male individual
- treat_grp: Treatment group names: the reproductive switch mode, represented as switch for those females paired with males throughout the experiment while non-switch for those females' initial reproductive mode was asexual.
- treat_id: Treatment group ID
- timing_of_eggs: E1 represents first 10-day period while E2 represents second 10-day period egg collections
- num_females: Number of females hatched
- num_males: Number of males hatched
- ratio_females: Proportion of female hatchlings
- ratio_males: Proportion of male hatchlings
- total_emerged_hatchlings: Total emerged hatchlings
- unemerged_hatchlings: Total unemerged hatchlings
- total_eggs_laid: Total eggs laid
File: heterozygosity_all_offspring.csv
Description: Heterozygosity level for all offspring
Variables: 9
- dna_extracted_date: DNA extracted date
- treat_id: Treatment group ID
- treat_grp: Treatment group names: the reproductive switch mode, represented as switch for those females paired with males throughout the experiment while non-switch for those females' initial reproductive mode was asexual.
- initial_mode: Whether females' initial reproductive modes were asexual (Parthenogenetic) or sexual (Mating)
- timing_of_eggs: E1 represents first 10-day period while E2 represents second 10-day period egg collections
- hatched_date: Hatched date for each hatchling
- sex_offspring: The sex of the hatchling, represented as F for female and M for male.
- adult_hatchling: Whether extracted individuals were hatchlings or adults
- percentage_hetero: Heterozygosity level
File: paternity_full_active.csv
Description: Sperm precedence analysis
Variables: 13
- origin_mom_type: Whether the population is Mixed-sex (reported as NMS) or All-female (reported as SAF).
- treat_id: Treatment group ID
- timing_of_eggs: E1 represents first 10-day period while E2 represents second 10-day period egg collections
- mother_id: The unique individual ID of each female individual
- offspring_id: The unique individual ID of each hatchling
- offspring_sex: The sex of the hatchling, represented as F for female and M for male.
- sire_a: First male mated with a female
- sire_b: Second male mated with a female
- heterozygosity_offspring: Heterozygosity level
- count_sire_a: The number of mismatched loci from first male
- count_sire_b: The number of mismatched loci from second male
- which_father: Potential father for each hatchling whether it was first or second male
- full_partial: Full parents data represented as full when all parents DNA sequence was done, as partial for either of the parents DNA sequence is missing
Code/software
We carried out all statistical analyses in R version 4.4.3 (R Core Team, 2025). We fitted GLMMs with the function glmmTMB from the package glmmTMB (Brooks et al., 2017), and the LMM with the lmer function from the package lme4 (Bates et al., 2007). GLMM effects were tested using Wald z-tests. We made ad-hoc pairwise comparisons using the function emmeans from the package emmeans (Lenth, 2025). We also examined whether paternity success differed overall between the first and second male using a Wilcoxon matched-pairs test, with female identity as the grouping factor. Model assumptions were verified using the package DHARMa (Hartig, 2024). We did not detect overdispersion in any of the models according to the function check_overdispersion from the package performance (Lüdecke et al., 2021).
We used lab-reared females that were collected as eggs from natural Northern genotype mixed-sex (BK, CO, MB, MK) and Southern genotype all-female (B1, CB, TB) populations (Fig. 1) of M. batesii in far-north Queensland, Australia (population codes correspond to Wilner et al., 2025a). Adult females were divided into two treatment groups: “switch” (N = 17) and “non-switch” (N = 18). In the switch group, females were first housed alone and, after the onset of oviposition, allowed to lay unfertilised eggs for 20 days. In the non-switch group, females were paired with a male (first male) soon after their adult moult (mean = 1.78 ± 1.06 days) and, after the onset of oviposition, allowed to mate and lay eggs for 20 days. The eggs laid over the first 20 days were then removed. The number of eggs laid during this 20-day period did not differ between unpaired (switch treatment) females and male-paired (non-switch treatment) females (see Fig. 4A in Wilner et al., 2025a). Switch treatment females were then paired with a male for 20 days, while non-switch treatment females were paired with a new male (second male) for 20 days (Fig. 2). Following male-pairing (switch treatment) or replacement (non-switch treatment), we collected eggs laid by each female over two successive 10-day periods.