Delineating conservation units in the Pink Cockatoo

How many independent populations should conservationists consider?

The Pink Cockatoo (Lophochroa leadbeateri) – one of the most iconic species in Australia – is of conservation concern. This colorful species is threatened by the intensification of agriculture, habitat loss and the illegal pet trade. In order to safeguard the future of the Pink Cockatoo, we need to have a clear overview of the populations that require protection. Here, conservation units and evolutionary significant units (ESU) are useful concepts. Conservation units refer to demographically independent units of genetic variation, whereas ESUs correspond to independently evolving units of genetic variation. Currently, the Pink Cockatoo is divided into two subspecies – leadbeateri and mollis – mainly based on morphological differences, such as the color and pattern of the crest. A recent study in the Biological Journal of the Linnean Society investigated whether these subspecies correspond to conservation units or ESUs, which would facilitate conservation efforts to protect this species.

Nuclear and mitochondrial patterns

Kyle Ewart and his colleagues took a closer look at the genetic make-up of 87 individuals across the range of the Pink Cockatoo. Analyses of nuclear markers revealed two clear genetic clusters that correspond to the two known subspecies. A third cluster was composed of several specimens of the subspecies leadbeateri and probably represents an artifact from analyzing related individuals. Therefore, we will focus on the two main clusters. Additional analyses indicated “relatively low, but significant genetic differentiation” between the two subspecies.

The population structure in the nuclear markers was not apparent in the mitochondrial DNA. Here, the researchers could not discriminate between the two subspecies. This lack of reciprocal monophyly is probably the result of a recent population expansion in which a common mitochondrial variant spread across the range of the Pink Cockatoo.

Distribution of Lophochroa leabeateri leadbeateri (blue) and Lophochroa leabeateri mollis (orange) in Australia. Genetic analyses revealed two clear clusters that correspond to both subspecies. However, the genetic differentiation is not clear cut. From: Ewart et al. (2021).

Conservation Units

Based on the genetic patterns described above, the researchers argue that the two subspecies should be considered as separate conservation units. However, the lack of mitochondrial differentiation and the subtle differences in the nuclear markers suggest that they are not independent evolutionary units. Although interesting from a fundamental perspective, these labels are less relevant within a conservation context. In the end, both subspecies might require different conservation measures.

Moreover, the researchers developed a set of molecular markers that can be used to confidently discriminate between the subspecies. This technique will be extremely useful in identifying source populations and combating illegal trade in these birds. Hopefully, these efforts will ensure a bright future for these beautiful birds.

References

Ewart, K. M., Johnson, R. N., Joseph, L., Ogden, R., Frankham, G. J., & Lo, N. (2021). Phylogeography of the iconic Australian pink cockatoo, Lophochroa leadbeateriBiological Journal of the Linnean Society132(3), 704-723.

Featured image: Pink Cockatoo (Lophochroa leadbeateri) © JJ Harrison | Wikimedia Commons

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