Editing Houtman Abrolhos (section)

==Biogeography==
Under the [[Interim Biogeographic Regionalisation for Australia]] (IBRA), the islands of the Houtman Abrolhos fall within the [[Geraldton Hills]] subregion of the [[Geraldton Sandplains]] region.<ref name="IBRA 5.1">{{cite book|author=[[Environment Australia]] |title=Revision of the Interim Biogeographic Regionalisation for Australia (IBRA) and Development of Version 5.1 – Summary Report |publisher=[[Department of the Environment and Water Resources]], [[Government of Australia|Australian Government]] |url=http://www.deh.gov.au/parks/nrs/ibra/version5-1/summary-report/index.html |access-date=2007-01-31 |archive-url=https://web.archive.org/web/20060905215218/http://www.deh.gov.au/parks/nrs/ibra/version5-1/summary-report/index.html |archive-date=5 September 2006 |url-status=dead }}</ref><ref name="IBRA 6.1">[http://www.deh.gov.au/parks/nrs/ibra/version6-1/index.html IBRA Version 6.1] data {{webarchive |url=https://web.archive.org/web/20060908221444/http://www.deh.gov.au/parks/nrs/ibra/version6-1/index.html |date=8 September 2006 }}</ref> The main [[biogeography|biogeographic]] significance of the islands is their isolation, allowing them to provide [[Refugium (population biology)|refugia]] for such threatened fauna as [[Tammar wallaby|tammar wallabies]] (''Macropus eugenii''), [[Australian sea lion]]s (''Neophoca cinerea'') and rare breeding seabirds.<ref name="Desmond 2001">{{cite book | first = Anthony | last = Desmond |author2=Alanna Chant | year = 2001 | chapter = Geraldton Sandplains 2 (GS2 – Geraldton Hills subregion) | chapter-url = http://www.naturebase.net/pdf/science/bio_audit/geraldton_sandplains02_p265-292.pdf | access-date = 2008-03-02 | title = A Biodiversity Audit of WA | url = http://www.naturebase.net/content/view/960/1397/ | publisher = Department of Environment and Conservation | location = Western Australia}}</ref>

In marine terms, the Houtman Abrolhos is located within the [[Southwest Shelf Transition]], an [[Integrated Marine and Coastal Regionalisation of Australia]] (IMCRA) [[biotone]] that takes in the continental shelf from [[Perth, Western Australia|Perth]] to [[Geraldton, Western Australia|Geraldton]]. This province is defined as the area of shelf where tropical waters intergrade into temperate, thus supporting both tropical and temperate biota.<ref name="IMCRA 3.3">{{cite book|title=Interim Marine and Coastal Regionalisation for Australia: an ecosystem-based classification for marine and coastal environments |url=http://www.environment.gov.au/coasts/mbp/publications/imcra/pubs/imcra3-3.pdf |access-date=2008-02-19 |author=IMCRA Technical Group |publisher=Environment Australia, Department of the Environment, Australian Government |url-status=dead |archive-url=https://web.archive.org/web/20080803001612/http://www.environment.gov.au/coasts/mbp/publications/imcra/pubs/imcra3-3.pdf |archive-date=3 August 2008 }}</ref><ref name="IMCRA 4.0 data">IMCRA 4.0 data</ref> In addition, this area contains the highest concentration of west coast endemics.<ref name="Wells 1997">{{cite book | first = Fred E. | last = Wells | year = 1997 | chapter = Introduction to the marine environment of the Houtman Abrolhos Islands, Western Australia | pages = 1–10 | editor = Wells, F. E.| title = The marine flora and fauna of the Houtman Abrolhos islands, Western Australia, Volume 1 | publisher = Western Australian Museum}}</ref>

Consistent with this, the Houtman Abrolhos contains a mix of tropical, temperate and west coast endemic fauna, resulting in unusual associations such as the occurrence of tropical corals in close association with temperate macro-algae. The proportions of tropical, temperate and west coast endemic biota vary from taxonomic group to group, but in general the biota is dominated by tropical species. This is attributable to the location of the Houtman Abrolhos at the northern limit of the Southwest Shelf Transition, together with the warming influence of the Leeuwin Current.<ref name="Wells 1997"/>

Under IMCRA, the Southwest Shelf Transition divides into two meso-scale bioregions. One is named ''Abrolhos Islands'', and covers the shelf waters surrounding the Houtman Abrolhos, with an area of {{convert|6,645|km2}}. The other bioregion, [[Central West Coast]], covers the remaining area.<ref name="IMCRA 3.3"/><ref name="IMCRA 4.0 data"/>