The influence of incubation temperature on offspring traits varies across northern and southern populations of the American alligator (Alligator mississippiensis)
Data files
Jun 10, 2025 version files 27.59 KB
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README.md
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Smaga_et_al_2024_ecol_evol_data.csv
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Smaga_et_al_2024_ecol_evol_hatch_counts.csv
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Abstract
Maternal provisioning and the developmental environment are fundamental determinants of offspring traits, particularly in oviparous species. However, the extent to which embryonic responses to these factors differ across populations to drive phenotypic variation is not well understood. Here, we examine the contributions of maternal provisioning and incubation temperature to variation in hatchling morphological and metabolic traits across four populations of the American alligator (Alligator mississippiensis), encompassing a large portion of the species’ latitudinal range. Our results show that whereas the influence of egg mass is generally consistent across populations, responses to incubation temperature show extensive population-level variation in several fitness-related traits, including mass, head length, head width, and residual yolk mass. Additionally, the influence of incubation temperature on developmental rate is greater in northern populations, while the allocation of maternal resources towards fat body mass is greater in southern populations. Overall, our results suggest that responses to incubation temperature, relative to maternal provisioning, are a larger source of interpopulation phenotypic variation and may contribute to the local adaptation of populations.
Alligator eggs were collected, weighed and measured from four populations and incubated under one of two temperature treatments: a constant male-promoting temperature (33.5C) and a constant female-promoting temperature (29.5C). At hatch, neonates were measured and raised for ten days in common garden conditions. Hatchlings were then euthanized to obtain additional tissue measurements.
Description of the data and file structure
Smaga_et_al_2023_ecol_evol_data - A .csv file containing phenotypic measurements. Blank values indicate missing data (n/a) from the experiment. Column names are as follows, with units in parentheses:
- edd_ID - individual egg ID
- site - population egg was collected from
- clutch - clutch number egg originated from by site abbreviation
- temp - incubation temperature treatment (degrees celsius)
- egg_mass - initial egg mass (g)
- st15_to_pip - incubation duration from st15 of development until pipping (days)
- mass - mass at hatch (g)
- svl - snout vent length (cm)
- tg - tail girth at the cloaca (cm)
- hl - head length (mm)
- hw - head width (mm)
- bmi - body mass index, calculated as mass/2*svl (g/cm^2)
- delta_mass - change in mass over 10 days (g)
- delta_svl - change in svl over 10 days (cm)
- delta_tg - change in tg over 10 days (cm)
- delta_bmi - change in bmi over 10 days (g/cm^2)
- res_yolk - mass of residaul yolk (g) at 10 days post hatch
- fat_body - mass of fat body (g) at 10 days post hatch
Smaga_et_al_2023_ecol_evol_hatch_counts - A csv file containing survival and hatch rates by temperature, clutch and site. Column names are as follows, with units in parentheses:
- site - population egg was collected from
- clutch - clutch number egg originated from by site abbreviation
- id - individual egg identifier
- temp - temperature treatment egg was incubated at (degrees celsius)
- hatch - whether an egg hatched (1 = yes, 0 = no)
- ten_day - whether an individual survived the 10-day post-hatch period (1 = yes, 0 = no)
Smaga_et_al_2024_ecol_evo_stats.R (Zenodo-Software) - Simplified R script for the models utilized in the analyses, using R (version 4.4.0) in RStudio.
Common garden incubation experiment. Alligator eggs were collected and incubated in a cross-foster design across two temperature treatments (29.5°C and 33.5°C). After hatching, neonates were raised in common garden conditions for ten days.