Cheap molecular markers can help to identify the origin of birds that died as bycatch.
“Conserving biodiversity, then, means more than preventing the extinction of a species. It also means preventing loss of genetic diversity within that species.” This statement comes from a recent article at The Conversation by Laura Bertola, and I wholeheartedly agree. However, in order to protect this genetic diversity, we need to know how it is distributed across a species. Is there one genetically homogeneous population, or are there many small pockets with unique genetic variation? This question is particularly relevant for seabirds, such as albatrosses, which can explore large oceanic regions without any physical barriers. You might expect to find little genetic differentiation between different breeding colonies, because birds can easily soar between islands. Or perhaps there are subtle genetic differences between colonies as birds tend to stay loyal to their breeding grounds. Depending on the situation, different conservation measures are needed to protect these birds. A recent study in the journal Conservation Genetics to a closer look at two endangered species: the Atlantic Yellow-nosed Albatross (Thalassarche chlororhynchos) and the Indian Yellow-nosed Albatross (Thalassarche carteri).
Population Structure
Dilini Abeyrama and her colleagues collected blood samples from different breeding colonies across the range of both species (see map below). Genetic analyses based on a set of 13 microsatellites uncovered two clear clusters, corresponding to the Atlantic and the Indian Yellow-nosed Albatross. Within each species, the researchers detected more fine-scale patterns of population structure. In the Atlantic Yellow-nosed Albatross, for example, Gough Island birds were genetically distinct from birds that breed on the Inaccessible and Nightingale Islands. The separation between the Atlantic and the Indian Yellow-nosed Albatross was also obvious in the mitochondrial data, revealing two clusters separated by six mutations. Based on these patterns, the researchers argue that both species should be treated as separate units for conservation and management. Several island populations will probably need to be considered as distinct conservation units as well, but the population structure within each species requires further investigation with genomic data.
Bycatch
These findings cannot only inform future conservation measures, they also have a direct practical application. Every year, albatrosses die as bycatch in fishery activities. Because Atlantic and Indian Yellow-nosed Albatross are morphologically similar, it is often not possible to identify the right species (let alone pinpoint their island of origin). Here, the genetic data come in handy.
The species-specific primers developed in our study allowed us to differentiate Atlantic and Indian yellow-nosed albatrosses with a high accuracy and low cost. Using this knowledge, we can develop a rapid molecular test to identify the bycatch yellow-nosed albatross samples which cannot be identified from their morphology.
Knowing how birds from different breeding colonies move across the ocean can provide insights into the behavior and ecology of these species. Invaluable knowledge that can be used to improve the conservation of these iconic species.
References
Abeyrama, D. K., Dempsey, Z. W., Ryan, P. G., & Burg, T. M. (2021). Cryptic speciation and population differentiation in the yellow-nosed albatross species complex. Conservation Genetics, 22(5), 757-766.
Featured image: Atlantic Yellow-nosed Albatross (Thalassarche chlororhynchos) © Vincent Legendre | Wikimedia Commons
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