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PHYLOGEOGRAPHY OF THE SARDINES (SARDINOPS SPP.): ASSESSING BIOGEOGRAPHIC MODELS AND POPULATION HISTORIES IN TEMPERATE
1Department. of Fisheries and Aquatic Sciences, University of Florida, 7922 NW 71st Street, Gainesville, Florida, 32653-3071.
Sardine populations show strong geographic structuring but shallow genetic divergence, suggesting recent dispersal events shaped their evolution. These findings challenge traditional biogeographic models, highlighting rapid adaptation to changing ocean conditions.
Area of Science:
- Marine Biology
- Evolutionary Genetics
- Biogeography
Background:
- Sardines inhabit temperate upwelling zones globally, with distinct populations separated by oceanic barriers.
- The evolutionary history of these populations is debated between vicariance and dispersal theories.
- Understanding sardine population dynamics is crucial for marine ecosystem management.
Purpose of the Study:
- To investigate the biogeographic history and evolutionary divergence of Sardinops spp. populations.
- To test the predictions of vicariance versus dispersal models using genetic data.
- To assess the impact of past climate and oceanographic changes on sardine populations.
Main Methods:
- Analysis of a 500 bp fragment of mitochondrial (mt) DNA control region.
- Electrophoretic survey of genetic variability at 34 nuclear loci.
- Comparison of genetic data with paleoclimate and oceanographic records.
Main Results:
- Strong geographic structuring of mtDNA lineages observed, but with shallow divergence within and between regional populations.
- Genetic data suggest a stepping-stone dispersal pattern around the Indian-Pacific Basin, likely driven by Pleistocene events.
- Divergence times are much more recent (within 500,000 years BP) than predicted by plate tectonics-based vicariance models.
- High mtDNA haplotype diversity and excess rare alleles suggest recent population expansions.
- Genetic data align with climate records, indicating unstable and ephemeral regional populations.
Conclusions:
- Sardine populations likely diverged recently due to dispersal events, not ancient vicariance.
- Recent evolutionary timescales and population instability are linked to climate and oceanographic changes.
- Sardine populations have experienced cycles of extinction and recolonization.
- Genetic data provide insights into the adaptive capacity of marine species to environmental fluctuations.
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