North Island Rifleman - cryptic species?

Discussion about the evolution, relationships, and naming of New Zealand birds
Bobolink
Posts: 15
Joined: Sat Jul 04, 2009 10:17 am

North Island Rifleman - cryptic species?

Postby Bobolink » Mon May 10, 2021 4:25 am

Withers S.J., Parsons S., Hauber M.E., Kendrick A. & Lavery S.D. (2021). Genetic divergence between isolated populations of the North Island New Zealand Rifleman (Acanthisitta chloris granti) implicates ancient biogeographic impacts rather than recent habitat fragmentation. Ecology and Evolution, first published: 04 may 2021.
https://onlinelibrary.wiley.com/doi/ful ... /ece3.7358

Abstract
"This research investigates the extent and causal mechanisms of genetic population divergence in a poorly flighted passerine, the North Island Rifleman or Titipounamu (Acanthisitta chloris granti). While this species has a historically widespread distribution, anthropogenic forest clearance has resulted in a highly fragmented current distribution. We conducted analyses of mitochondrial DNA (COI and Control Region) and 12 nuclear DNA microsatellites to test for population divergence and estimate times of divergence. DiyAbc and BioGeoBears were then used to assess likely past dispersal scenarios based on both mtDNA and nDNA. The results reveal several significantly divergent lineages across the North Island of New Zealand and indicate that some populations have been isolated for extensive periods of time (0.7–4.9 mya). Modeling indicated a dynamic history of population connectivity, with a drastic restriction in gene flow between three geographic regions, followed by a more recent re‐establishment of connectivity. Our analyses indicate the dynamic influence of key geological and climatological events on the distribution of genetic diversity in this species, including support for the genetic impact of old biogeographic boundaries such as the Taupo Line and Cockayne's Line, rather than recent anthropogenic habitat fragmentation. These findings present a rare example of an avian species with a genetic history more like that of flightless taxa and so provide new general insights into vicariant processes affecting populations of passerines with limited dispersal."

Based on genetic divergence times, there may be a case for splitting South Island and North Island Riflemen, and also clades corresponding to Northern North Island from Southern North Island, and even Insular, Mainland and Southern from each other. A project for a PhD Student?
SomesBirder
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Joined: Wed Dec 05, 2012 4:02 pm

Re: North Island Rifleman - cryptic species?

Postby SomesBirder » Fri Sep 24, 2021 10:35 pm

Is there a specific reason for why the paper treats the Stout-legged Wren as still being one species, or is it just an oversight?
Ian Southey
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Joined: Tue Sep 08, 2009 5:45 pm

Re: North Island Rifleman - cryptic species?

Postby Ian Southey » Sat Sep 25, 2021 12:01 pm

Maybe an oversight, but maybe an attempt to be 'cutting edge'.

Officially there are two species differentiated only on size, in the North and South Islands but the size difference seems less convincing as more material has come to light and it has suggested somewhere that there may only be one species. As far as I know, no one has done the work either to check if there is still a clear difference or if there are any other characters that may differentiate the two.

Until this work is done the checklist should be followed. There have been some strange beliefs circulating about our fossil birds in the past and it is simpler in the long run to wait for someone to do the work.

Ian
SomesBirder
Posts: 1336
Joined: Wed Dec 05, 2012 4:02 pm

Re: North Island Rifleman - cryptic species?

Postby SomesBirder » Sat Oct 09, 2021 9:52 pm

Thanks, Ian.

I notice that there has been a trend in taxonomy with lumping extinct taxa in with other taxa (extinct and extant) in recent years. To my understanding it has mostly been happening with large mammal species overseas, but it also happened here with the Chatham Island Raven. Is this trend purely a result of better understanding of genetic differences, or is there perhaps an ulterior motive at work?

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