Eastern bristlebird (Dasyornis brachypterus monoides) northern subspecies - rejection of subspecies listing

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to REJECT a proposal to list the northern subspecies of the Eastern Bristlebird Dasyornis brachypterus monoides Schodde & Mason, 1999 as a CRITICALLY ENDANGERED SPECIES in Part 1 of Schedule 1A of the Act. Rejection of nominations is provided for by Part 2 of the Act.

See the determination for the Eastern Bristlebird endangered species listing.

NSW Scientific Committee - final determination

The Scientific Committee has found that:

1. Following the exhibition of a Preliminary Determination in October 2008 to support a proposal to list the northern subspecies of the Eastern Bristlebird Dasyornis brachypterus monoides Schodde & Mason, 1999 as a CRITICALLY ENDANGERED SPECIES, subsequent DNA research casts doubt on the validity of designating this population as subspecifically distinct.

2. The Eastern Bristlebird Dasyornis brachypterus, formerly regarded as monotypic, was split into two subspecies (Schodde & Mason 1999),  Dasyornis brachypterus monoides (northern subspecies) and  Dasyornis brachypterus brachypterus (southern subspecies). The northern subspecies was described as follows (Schodde & Mason 1999): “Dorsum  dark olive-brown; breast and upper flank feathers with  obsolete dusky centres and fringes, effecting a rather  plain facade; lower flanks  extensively olive-brown, the tone washing over breast and belly.” This description contrasts with that of the southern subspecies described as having: “Dorsum  mid-deep olive-brown; breast and upper flank feathers with dull but  distinct dusky centres and fringes, effecting a  mottled-scalloped facade; lower flanks  restrictedly olive-brown, leaving lower breast and belly extensively greyish white” (Schodde & Mason 1999).

3. Recent DNA analysis (Roberts et al. 2011) does not support the recognition of subspecies for northern and southern populations of the Eastern Bristlebird. The phylogeny of mitochondrial DNA sequences identified two clades, but the distribution of haplotypes within each clade was not geographically structured, with haplotypes from northern and southern populations represented in each clade (Roberts  et al. 2011). The lack of phylogenetic distinctiveness does not support the separation of subspecies. This work confirms previous analysis of DNA sequence data (M. Elphinstone, cited in Higgins & Peter 2003), which detected little or no genetic divergence between northern and southern populations of Eastern Bristlebirds.

4. There are four disjunct, natural populations of the Eastern Bristlebird in New South Wales, as well as two translocated populations within the natural range. All four natural populations, including the northern population described by Schodde & Mason (1999) as Dasyornis brachypterus monoides, are genetically isolated from each other as determined by analysis of microsatellite markers (Roberts  et al. 2011). The northern population is disjunct from the nearest population south by  c. 700 km and is now confined to the Conondale Range and Border Ranges of south-east Queensland and north-east NSW. The total number of individuals in the northern population (including Queensland birds) is extremely low, estimated as  c. 35 birds (Garnett & Crowley 2000; Stewart  et al. 2004).

5. The subject of the original proposal, identified as the northern subspecies of the Eastern Bristlebird Dasyornis brachypterus monoides Schodde & Mason, 1999 is not eligible to be listed as a Critically Endangered species as, in the opinion of the Scientific Committee, recent molecular evidence does not support the conclusion that it is subspecifically distinct Consequently, the full species of the Eastern Bristlebird  Dasyornis brachypterus (Latham, 1802) remains listed in Part 1 of Schedule 1 (Endangered species) of the Act. Furthermore, the northern population of the Eastern Bristlebird  Dasyornis brachypterus is facing an extremely high risk of extinction in New South Wales in the immediate future owing to its extremely low population size.

Dr Richard Major
Chairperson
Scientific Committee

Gazettal date: 28/10/11
Exhibition period: 28/10/11 - 20/01/12

References:

Garnett S, Crowley G (Eds) (2000) ‘The action plan for Australian birds 2000.’ (Environment Australia: Canberra)

Higgins PJ, Peter JM (Eds) (2003) ‘Handbook of Australian, New Zealand and Antarctic birds (Vol. 6).’ (Oxford University Press: Melbourne)

Roberts DG, Baker J, Perrin C (2011) Population genetic structure of the endangered Eastern Bristlebird, Dasyornis brachypterus; implications for conservation.  Conservation Genetics 12, 1075-1085.

Schodde R, Mason IJ (1999) ‘The directory of Australian birds: Passerines.’ (CSIRO: Melbourne)

Stewart D, Gillman S, Rounsevell D (2004) The recovery process for the Eastern Bristlebird in Queensland. Sunbird 34, 66-79.