Related Experiment Video
Updated: Jul 6, 2026
09:32
Development of New Methods for Quantifying Fish Density Using Underwater Stereo-video Tools
Published on: November 20, 2017
Annual variation in source contributions to a mixed stock: implications for quantifying connectivity.
Karen A Bjorndal1, Alan B Bolten
1Archie Carr Center for Sea Turtle Research, Department of Zoology, University of Florida, PO Box 118525, Gainesville, FL 32611, USA. kab@zoology.ufl.edu
Molecular Ecology
|April 1, 2008
Summary
Green sea turtle (Chelonia mydas) genetic data reveal significant yearly changes in population composition. This temporal variation, primarily driven by recruitment, impacts estimates of connectivity and genetic diversity in migratory species.
Area of Science:
- Marine Biology
- Conservation Genetics
- Population Dynamics
Background:
- Understanding connectivity in migratory species is crucial for conservation.
- Genetic markers are commonly used to assess population structure and gene flow.
- Temporal variation in population composition can influence genetic analyses.
Purpose of the Study:
- To investigate temporal structuring in mitochondrial DNA (mtDNA) haplotype frequencies of green turtles (Chelonia mydas) in the southern Bahamas.
- To identify the primary drivers of observed temporal variation in this foraging aggregation.
- To assess the impact of temporal variation on estimates of population connectivity and genetic diversity.
Main Methods:
- Mitochondrial DNA (mtDNA) sequencing of 350 green turtles across 10 annual samples over 12 years.
- Analysis of temporal structuring in haplotype frequencies.
- Application of a Bayesian hierarchical model to estimate rookery contributions and identify causes of temporal variation (recruitment, mortality, emigration).
Main Results:
- Significant temporal structuring in haplotype frequencies was observed for both the overall turtle aggregation and for new recruits.
- Substantial year-to-year variation in the relative contributions from different nesting rookeries was detected.
- Recruitment was identified as the main driver of temporal variation, more so than mortality or emigration.
Conclusions:
- Temporal variation in population composition significantly affects estimates of connectivity and genetic diversity in green sea turtle populations.
- The findings highlight the importance of considering temporal dynamics in genetic studies of migratory species.
- Further research is needed to understand the extent of temporal variation in other mixed-stock migratory populations.
Related Concept Videos
01:07Speciation Rates
Speciation can proceed at markedly different rates, and evolutionary biologists commonly describe these differences through the models of gradualism and punctuated equilibrium. Both patterns explain how new species arise, but they differ in the tempo and continuity of evolutionary change. In both cases, evolutionary change arises from heritable variation within populations, with natural selection often shaping traits that improve survival and reproduction under specific environmental conditions.
02:07Conservation of Declining Populations
Conservation of declining population focuses on ways of detecting, diagnosing, and halting a population decline. The approach uses methods to prevent populations from going extinct.
01:09Mutation, Gene Flow, and Genetic Drift
In a population that is not at Hardy-Weinberg equilibrium, the frequency of alleles changes over time. Therefore, any deviations from the five conditions of Hardy-Weinberg equilibrium can alter the genetic variation of a given population. Conditions that change the genetic variability of a population include mutations, natural selection, non-random mating, gene flow, and genetic drift (small population size).Mechanisms of Genetic VariationThe original sources of genetic variation are mutations,...
02:16Genetics of Speciation
Speciation is the evolutionary process resulting in the formation of new, distinct species—groups of reproductively isolated populations.The genetics of speciation involves the different traits or isolating mechanisms preventing gene exchange, leading to reproductive isolation. Reproductive isolation can be due to reproductive barriers that have effects either before or after the formation of a zygote. Pre-zygotic mechanisms prevent fertilization from occurring, and post-zygotic mechanisms...
02:39Gene Flow
Gene flow is the transfer of genes among populations, resulting from either the dispersal of gametes or from the migration of individuals.
02:04Conservation of Small Populations
Small population sizes put a species at extreme risk of extinction due to a lack of variation, and a consequent decrease in adaptability. This weakens the chances of survival under pressures such as climate change, competition from other species, or new diseases. Large populations are more likely to survive pressures such as these, as such populations are more likely to harbor individuals that have genetic variants that are adaptive under new stresses. Small populations are much less likely to...