DOI: 10.5061/dryad.59zw3r2mt
title: Shorter recruitment period and higher fecundity in high latitudinal populations of <em>O. latipes</em> species complex

description: In many organisms, environmental temperature is a key determinant of the
 reproductive season, although physiological thermal responses related to
 reproduction often vary among taxa. Comparative analyses of reproductive
 seasonality within and between species can provide insights into the
 physiological constraints and local adaptation of reproductive traits in
 wild populations. This study examined wild populations of medaka (Oryzias
 latipes species complex). Although the photo-thermal thresholds for
 gonadal maturation in this species have been studied extensively in
 laboratory settings, geographical patterns of seasonality in gonad
 maturation, fecundity, and recruitment have not been thoroughly
 investigated in wild populations. We examined seasonal changes in gonad
 weight and the proportions of juveniles in wild populations of medaka at
 different latitudes. Our findings showed that seasonal changes in gonad
 weight were more pronounced in a high-latitude population in Aomori
 compared to a low-latitude population in Okinawa, irrespective of sex.
 Annual average proportions of juveniles tended to be higher in the Okinawa
 population compared to the Aomori and Chiba populations, suggesting a
 shorter recruitment period in high-latitude populations. A comparison of
 body size and egg number indicated that fecundity was relatively higher in
 high-latitude populations. We discuss whether gonad maturation at high
 latitudes can be explained by seasonal changes in temperature.
 Interpopulation differences in the gonadosomatic index and fecundity
 support the adaptive evolution of increased reproductive investment in
 high-latitude environments with shorter reproductive seasons.
 Additionally, trade-offs between survival and reproduction may influence
 ecological longevity and annual recruitment dynamics in these populations.
description: # Shorter recruitment period and higher fecundity in high latitudinal
 populations of *O. latipes* species complex Dataset DOI:
 [10.5061/dryad.59zw3r2mt](10.5061/dryad.59zw3r2mt) ## Description of the
 data and file structure * Monthly average water temperature in the habitat
 of medaka\ Aomori 2003-2005 and Okinawa 2012-2013\ The original dataset of
 Aomori was published in Fujimoto et al. 2021 - Seasonal change in body
 weight and gonad weight\ Aomori 2004 and Okinawa 2012-2013\ The original
 dataset of Aomori was published in Fujimoto et al. 2021 - Seasonal change
 in size frequency distribution\ and juvenile proportion in Aomori 2013,
 Chiba 1983-1985, Okinawa 2012\ The original dataset of Chiba was published
 in Egami et al. 1988 - Relationship between standard length and egg
 number\ The collection has performed in Aomori (2013, 2014), Hirosaki
 (2025),\ Kasumigaura (2024), Itako (2024), Nagasaki (2025), and Okinawa
 (2012, 2025)\ The original dataset of Aomori (2013) and Okinawa (2012) was
 published\ in Fujimoto et al. 2024 ### Files and variables #### File:
 rawdata_submitDryad_20260204.zip **Description:**  *
 Fig1_temperature_photoperiod\    
 waterTemperature_monthlyAverage_AoOk.csv: \         Monthly average water
 temperature in the habitat of medaka (Aomori and Okinawa)\          
  year: The year of the sampling date of water temperature (units: year)\  
          month: The month of the sampling date of water temperature
 (units: month)\            locality: Collection site name of water
 temperature (units: none)\            temperature: Monthly average water
 temperature (units: celsius)\     Fig_1_waterTempFigure_AoOk.R:\        
 Custom script to make the water temperature -
 Fig2_Tabl1_1-2_gonad_maturation\    
 gsi_ao2003-2004_ok2012-2013_ver1_0.csv: \         Seasonal change in body
 weight and gonad weight (Aomori and Okinawa)\            location:
 Collection site name of fish (units: none)\            year: The year of
 the collection date of fish (units: year)\            month: The month of
 the collection date of fish (units: month)\            collectDate: The
 collection date of fish (units: yyyy/mm/dd)\            individualID:
 Individual ID for each fish collection (units: none)\            sex: Sex
 phenotype identified by morphology (f: female, m: male)\            SLmm:
 Standard length of fish (units: mm)\            BW_fol: Wet body weight of
 fish fixed by formalin (units: mg)\            gonadW: Gonad weight of
 fish fixed by formalin (units: mg) \            OrdinalYear: Ordinal
 date converted from month and day (units: 1=1/1, 365=12/31)\          
  OrdinalFig: Ordinal date for figure illustration,\                      
           the date started from the time series of each collection site\  
                               (aomori: 1=2004/1/1, okinawa: 1=2012/1/1)\  
   Fig_2_gonadSomaindex_ver3_6.R:\          Custom script, Estimation
 of seasonal change in gonad-soma index\          using a generalized
 additive model\    
 Table_S1_S2_medakaGSI_curveEstimate_test_jes_ver3_5.R:\        
  Statistical test and summary table output of GAM *
 Fig3_Table3_size_distribution_recruitment\    
  histogramDataset_ao2013_ok2012.csv:\         Standard length dataset
 collected from Aomori and Okinawa\            population: Collection site
 name of fish (units: none)\            year: The year of the collection
 date of fish (units: year)\            collectDate: The collection date of
 fish (units: yyyymmdd)\            sex: Sex phenotype identified by
 morphology (F: female, M: male, I: inmatured sex)\          
  SLmm: Standard length of fish (units: mm)\            yyyymm: The year
 and month of the collection date (units: yyyymm)\            month: The
 month of the collection date of fish (units: month) \          
  dateConverted: The collection date of fish (units: yyyy/mm/dd)\          
  Ordinal: Ordinal date for figure illustration,\                          
       the date started from the time series of each collection site\      
                           (aomori: 1=2004/1/1, okinawa: 1=2012/1/1)\      
      panelOrder: The order of the panels for figure illustration\ \    
  egami1988_imbanuma_ver2.csv:\         Juvenile proportion collected by
 Egami et al. 1988, in Imbanuma, Chiba prefecture\           population:
 Collection site name of fish (units: none)\           date: The collection
 date of fish (units: yyyymmdd)\           month: The month of the
 collection date of fish (units: month) \           TotalNumbers: The total
 number of size measured individuals\                                      
   in each collection (units: individuals) \           totalArea_px: The
 total area of bins in original histgram figure \                          
               in each collection (units: pixels)\           area10mm_px:
 The area of bins with size class less than 10mm of\                      
                   original histgram figure in each collection (units:
 pixels)\           area15mm_px: The area of bins with size class less than
 15mm of\                                         original histgram
 figure in each collection (units: pixels)\           area20mm_px: The area
 of bins with size class less than 20mm of\                                
         original histgram figure in each collection (units: pixels)\ \    
  juvenileRecruitmentSummary.csv:\        Juvenile proportion of Aomori,
 Chiba, and Okinawa,\        The values summrized from
 "histogramDataset_ao2013_ok2012.csv" and\      
  "egami1988_imbanuma_ver2.csv" for figure illustration\        
      population: Collection site name of fish (units: none)\            
  year: The year of the collection date of fish (units: year)\            
  month: The month of the collection date of fish (units: month)\          
    yyyymm: The year and month of the collection date (units: yyyymm)\    
          collectDate: The collection date of fish (units: yyyy/mm/dd)\    
          totalNumbers: The total number of size measured individuals\    
                                     in each collection (units:
 individuals) \              juvenileRate: The proportion was calculated
 individual number with\                                       less than
 the standard length 15 mm divided by the total individual number\        
                               in each collection (units: ratio) \        
     ordinal: Ordinal date converted from month and day (units: 1=1/1,
 365=12/31)\             ordinalFig: Ordinal date for figure illustration,\
                                 the date started from the time series of
 each collection site\                                 (aomori: 1=2004/1/1,
 okinawa: 1=2012/1/1)\ \      Fig_3_sizeHistogram_ver3_6.R:\        
 Monthly change of size-frequency distribution based on each collection   
     \      Fig_3_sizeClusteringByMClust.R:\        Statistical clustering
 of size-frequency distribution to separate the year cohorts\    
  Fig_3_recruitmentSeasonality_dataExtract_ver1_1.R: \         Calculate
 the summary table of juvenile proportion (SL &lt; 15mm) in each
 collection\    
  Fig_3_Table_S3_S4_recruitmentSeasonality_juvenileProportion_ver1_1.R \  
      Estimation of seasonal change in juvenile proportion of Aomori,
 Chiba, and Okinawa * Fig4_eggNumComparison\    
  oryzias_size-fecundity_combined_2012-2025.csv:\        Standard
 length(SL) and egg numbers in six collection sites from different
 latitudes\            ExperimentSeries: The name of experimental series
 (units: none)\            Species: Scientific name of collected fish
 (units: none)\            Observed date: Spawned egg count date (units:
 yyyymmdd)\            Location/Strain: The collection city name of
 location or strain of fish colection (units: none)\          
  CollectionSite: The collection site name of fish colection (units: none)\
            individual: Individual ID of collected fish in each collection
 (units: none)\            photo: photograph file ID for morphological
 measurement (units: none)\            egg number: Spawned egg nummber in a
 female (units: count)\            SLmm: Standard length of fish (units:
 mm)\            body weight: Body weight of fish (units: mg)\          
  Reference: The original dataset references (units: none)\ \    
  Fig4_FigS1_eggNumComparison_oryzias_wild_20251022.R: Estimation of slope
 between SL\        and egg numbers using linear mixed model (LMM)  ##
 Access information Data was derived from the following sources: * Egami,
 N. et al. (1988). The life span of wild populations of the fish Oryzias
 latipes under natural conditions. *Zoological Science*, 5, 1149–1152. *
 Fujimoto, S. et al. (2021). Seasonal change in male reproductive
 investment of a fish. *Environmental Biology of Fishes*, *104*(2),
 107–118.
 [https://doi.org/10.1007/s10641-021-01059-x](https://doi.org/10.1007/s10641-021-01059-x) * Fujimoto, S. et al. (2024). Evolution of Size-Fecundity Relationship in Medaka Fish From Different Latitudes. *Molecular Ecology*, *33*(23), e17578. [https://doi.org/10.1111/mec.17578](https://doi.org/10.1111/mec.17578)