Combining Genetics and Ecology to Protect an Unknown Sardine

Jenn Hoskins
9th March, 2024

Combining Genetics and Ecology to Protect an Unknown Sardine

Image Source: Natural Science News, 2024

Key Findings

  • Study in Brazil finds two distinct sardine lineages with unique DNA due to ocean barriers
  • Coastal sardines expanded in number, while island sardines shrank due to past climate changes
  • Researchers suggest separate conservation plans for coastal and island sardine populations
Understanding the genetic diversity within marine species is crucial for developing effective conservation strategies, particularly as human activities continue to alter the world's ecosystems. Researchers from the Universidade Federal do Rio Grande do Norte have taken a significant step in this direction with their recent study on an overfished yet undescribed sardine species within the genus Harengula[1]. This research is vital for informing conservation efforts, particularly in marine environments where many species are not fully described and are subject to overfishing, leading to conflicts between conservation needs and resource exploitation. The study focused on the distribution and genetic diversity of this sardine species along the Brazilian coast and two isolated oceanic archipelagos. The researchers discovered that salinity and depth are key factors determining the species' distribution. Interestingly, there's a continuous population along the mainland coast, while the populations on the oceanic islands are separated, forming distinct biogeographic barriers. Genomic data revealed two divergent lineages within the species, suggesting that they have been separated long enough to evolve differences in their DNA. This is where the study shines, as it combines niche modelling (which predicts where a species can live based on environmental conditions) with population genomics (the study of genetic variation within populations). This approach can help resolve conflicts in conservation and resource management by identifying distinct management units within a species. The researchers also looked into the past, examining how the last glacial cycle affected these sardine populations. They found that one of the coastal populations expanded approximately 3.6 times in size, while an island-associated population contracted to a third of the size of its ancestral population. This suggests that historical climatic events have shaped the current genetic landscape of these sardine populations. The implications of these findings are significant for conservation. The distinct genetic lineages and their different demographic histories indicate that the island population should be managed separately from the coastal population. Moreover, the study suggests that establishing a Marine Protected Area (MPA) that includes part of the island population's distribution could be crucial for preserving this lineage. This research aligns with previous studies that have highlighted the importance of considering intraspecific variation when assessing species' vulnerability to climate change[2]. Just as the Sino-Himalayan birds showed different responses to climate change based on their local adaptations, the sardine populations in this study exhibit different demographic histories likely driven by past climate events. The study also echoes findings about the influence of gene flow and habitat fragmentation on genetic structure[3]. Similar to the broadnosed pipefish, which showed strong genetic structure due to its fragmented eelgrass habitat and non-pelagic larval stage, the sardine populations in this study are genetically distinct due to the biogeographic barriers between them. Furthermore, this research contributes to the ongoing efforts to bridge the gap between the availability of genomic data and its application in conservation, as emphasized by initiatives like the Threatened Species Initiative in Australia[4]. By providing a clear example of how genomic data can inform management decisions, the study serves as a model for integrating genomics into conservation practice. Lastly, the study's approach to defining management units based on genetic data is reminiscent of the work done on Atlantic cod, where genomic tools revealed a more complex structure than previously recognized by management plans[5]. The delineation of separate management units for the island and coastal sardine populations could prevent overexploitation and ensure the sustainability of both stocks. In conclusion, the study by the Universidade Federal do Rio Grande do Norte offers a comprehensive look at how past climatic events and current environmental factors shape the genetic diversity and distribution of marine species. It provides a roadmap for identifying management units within a species, which is essential for targeted and effective conservation efforts. By recognizing the unique needs of different populations within a species, we can better protect marine biodiversity in the face of ongoing human-induced changes.

GeneticsEcologyMarine Biology


Main Study

1) Integration of genomic and ecological methods inform management of an undescribed, yet highly exploited, sardine species.

Published 6th March, 2024

Related Studies

2) The combination of genomic offset and niche modelling provides insights into climate change-driven vulnerability.

3) Combining population genomics with demographic analyses highlights habitat patchiness and larval dispersal as determinants of connectivity in coastal fish species.

4) Threatened Species Initiative: Empowering conservation action using genomic resources.

5) Genomic analysis reveals neutral and adaptive patterns that challenge the current management regime for East Atlantic cod Gadus morhua L.

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