Prickly postglacial pioneers: freshwater plankton community composition influences fatty acid desaturase (FADS2) copy number in Southern Greenland threespine sticklebacks
Data files
Oct 07, 2024 version files 59.49 KB
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Env_Data.csv
763 B
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Fads_Data.csv
52.44 KB
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README.md
3.89 KB
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summary_FADS.csv
2.40 KB
Abstract
The adaptation of marine fish to freshwater environments includes prodigious examples of rapid evolution. Given the scarcity of ω-3 long-chain polyunsaturated fatty acids (LC-PUFA) in freshwater, we expect selection to be strong on fish transitioning to freshwater habitats and yet the underlying ecological causes of genomic and phenotypic differentiation are poorly understood for traits associated with lipid content and composition. Threespine stickleback (Gasterosteus aculeatus) have repeatedly colonized, and adapted to, freshwater habitats across the northern hemisphere. These freshwater populations often show elevated copy number of the fatty acid desaturase 2 gene (FADS2), which increases the biosynthetic capacity of LC-PUFA. The starkly lower content of LC-PUFA in freshwater compared to marine prey, especially docosahexaenoic acid (DHA), likely imposes strong positive selection on freshwater fish for either increased biosynthesis or greater dietary acquisition of LC-PUFA. The recently colonized and relatively undisturbed threespine stickleback populations in postglacial coastal lakes of Southern Greenland offer an exceptional opportunity to study how variation in the copy number of FADS2 is related to abiotic and biotic conditions of lakes and their morphometry. As expected, given its position on the stickleback X chromosome, we found strong sexual dimorphism in FADS2 copy number in all populations (19 freshwater, 1 marine, and 1 brackish), and an increased dimorphism in some freshwater populations. We also found that FADS2 copy number was negatively correlated, for both males and females, with the abundance of copepods, which are a DHA-rich food source in the zooplankton community. Overall, our results suggest that the prey community context of lakes might influence the process of metabolic adaptation of marine fish colonizing freshwater ecosystems.
Readme File for “Prickly postglacial pioneers: adaptation of threespine stickleback to freshwater influences fatty acid desaturase (FADS2) copy number in Southern Greenland” Datasets
Dataset 1 - FADS_Data
This dataset contains information on threespine stickleback fatty acid desaturase 2 gene copy number (FADS2) from populations sampled in southern Greenland as they relate to environmental characteristics of freshwater lakes.
We collected information on the plankton community composition of freshwater lakes by sampling water bodies with plankton nets, and sampled threespine stickleback tissue to determine gene copy number with qPCR (after DNA extraction)
These data were then used to investigate whether variation in FADS2 gene copy number among populations was related to differences in environmental conditions.
Fishec: Unique individual ID numbers for collected specimens
Sex: Sex identification for each specimen (categorical, M or F)
Site: Name of collection site
Site2: Collection site with marine populations pooled
Site3: Sites split into freshwater or marine categories
ASIN_Plank_Comp: Arcsin transformed column of plankton composition
Plank_Comp: Proportion of copepods in the plankton community (1 = entirely copepods, 0 = no copepods)
Total_BM: The total zooplankton biomass (BM) in ug/L for a given lake (sum of Copepod_BM and Cladocera_BM)
Log_Total_BM: Log transformation of Total_BM
Copepod_BM: Sum of Calanoid_BM and Cyclopoid_BM (ug/L)
Calanoid_BM: Total biomass calanoid copepods in our sample (ug/L)
Cyclopoid_BM: Total biomass cayclopoid copepods in our sample (ug/L)
Cladocera_BM: Total biomass of cladocera in our sample (ug/L)
Region: Q, A, and T represent the three regions Qassiarsuk, Akia, and Tuttutoq sampled in this study
Salty: Sites scored as saltwater or freshwater
Salty2: Same as Salty, but with saltwater split into Marine and Coastal brackish populations
Areaha: Lake area in hectares
Log_Areaha: Log transformed lake area
Elevation: Lake elevation in meters
Log_Elevation: Log transformed lake elevation
FADS2: Relative FADS2 copy number from our gqPCR - This is our estimate of the number of gene copies that are present in the genome of a particular fish
Dataset 2 - Env_Data
This dataset contains information on the phyiscal properties of freshwater lakes in Greenland (e.g. lake area and elevation) along with the biomass of plankton and proportion of copepods captured from field sampling of zooplankton.
Lake: Name of sampling site
Prop_Copepods: Proportion of copepods found in the zooplankton sample from 0-1 (1 = entirely copepods, 0 = no copepods)
Lake_Area: Lake area measured in hectares
Lake_Elevation: Lake elevation measured in meters
Total_Zoop_BM: Total zooplankton biomass measured in ug/L
Dataset 3 - summary_FADS
This is a summarized version of the first dataset (FADS_Data.csv), showing the mean and maximum FADS2 copy number for males and females from each lake with standard error, standard deviation, and number of individuals per site.
Estimates of FADS2 gene copy number are derived from qPCR
Site: Name of collection site
Type: A categorical variable describing whether fish were sourced from freshwater, brackish, or saltwater populations
N_fem: Number of female fish collected at this site
mean_fem: The mean FADS2 gene copy number for females for a given site
max_fem: The maximum FADS2 gene copy number found in female fish from a given site
sd_fem: Standard deviation around the FADS2 mean for females
se_fem: Standard error for FADS2 mean for females
N_male: Number of male fish collected at this site
mean_male: The mean FADS2 gene copy number for males for a given site
max_male: The maximum FADS2 gene copy number found in male fish from a given site
sd_male: Standard deviation around the FADS2 mean for males
se_male: Standard error for FADS2 mean for males