LBI and Codfish Cooks petrel populations

[raynerm]

Hi All,

Interesting discussion so I thought I would give an update. A valid point that Co1 is not a particularly useful marker for investigating the long-term population genetics of Cook’s and the hypothesis of a haplotypes cline with intermediate populations (since wiped out) is a good one. However we have increasing evidence that the two Cook’s populations are incipient species…..what evidence you say…well we know:

a) The two populations have difference sin body size consistent with Bergmans rule and 1 month asynchrony in breeding timing indicating reproductive isolation (Imber 2003).
b) During breeding they occupy distinct foraging habitats in differing oceanic regions (Rayner et al 2008 MEPS)
c) They have strong population genetic structuring – for Co1 at least (Rayner et al 2010 Con Genetics)
d) Finally we have a manuscript in review detailing how the two populations are separated on their non-breeding grounds. LBI birds migrate to the north Pacific and Codfish birds (formerly named orientalis) migrate to the Humboldt Current. Co1 sequences from skins collected by Rollo Beck in the respective core areas of the modern populations (off Baja and Peru) confirm these populations have been doing this for a minimum of 100 years.

Tammy Steeves and I hope to get into some ancient DNA work looking at NZ Cook’s petrel bones soon to look at regional population genetics.

Cheers, Matt Rayner

[Neil Fitzgerald]

Thanks for the input Matt. I look forward to reading more on this story.

[Ian Southey]

The difference between the northern and southern Cook's Petrels has been formally recognised - Pterodroma cookii cookii (Little Barrier) and P. c. orientalis (Whenuahou). The results of ancient DNA were particularly interesting.

https://www.researchgate.net/publicatio ... management

Ian

[Michael Szabo]

"Morphological, behavioural, and genetic studies have identified the two remaining populations
of Cook’s Petrels as distinct conservation management units. As reviewed in Rayner et al.(2010a),
Imber (2003) identified differences in body mass between smaller birds on LBI and larger birds on
CDF, which parallels significant differences in the breeding season foraging habitat use (Rayner
et al.2008b,2010b). Moreover, the asynchronous breeding and migration schedules of the two
populations (approximately six weeks apart), as well as separate nonbreeding distributions, are a
recognised barrier to gene flow through local adaptation in combination with strong natal philo-
patry (Rayner et al.2011). In the first genetic study of the species, Rayner et al.(2010a) identified
significant population genetic structure between the extant populations in mitochondrial DNA
(mtDNA) cytochrome oxidase 1(COI) sequences. Five mtDNA haplotypes were detected, four in
the LBI population and one in the CDF population. No mtDNA haplotypes were shared between
populations and there was a single fixed polymorphism that could be used to separate samples from
both contemporary and historic (museum skin) individuals collected in the eastern Pacific Ocean
(Rayner et al.2010a,2011). As a result of these studies, it was recommended that the LBI and CDF
populations be treated as distinct conservation management units. However, taxonomic designa-
tion and an understanding of the level of genetic diversity within each population require further
analysis integrating nuclear markers and data from extirpated populations (Rayner et al.2010a)."