The biogeographical anomaly of the brown honeyeater (Lichmera indistincta) in southwestern Australia
INTRODUCTION
Lichmera indistincta is common in southwestern Australia, including the Perth Metropolitan area (https://en.wikipedia.org/wiki/Perth).
https://www.tandfonline.com/doi/abs/10.1080/03014223.1985.10428310 and https://library.sprep.org/content/introductory-ecological-biogeography-australo-pacific-meliphagidae
This species is easy to take for granted in Perth, being the local counterpart for the sunbirds (Nectariniidae) so common in gardens in Africa and Asia.
However, L. indistincta is odd in two ways, as follows.
Firstly, it is extremely dull-coloured, particularly in the male in breeding condition. By comparison, most morphologically similar, sunbird-like birds are 'flashy', with bright hues and/or iridescence (https://en.wikipedia.org/wiki/Mrs._Gould%27s_sunbird#/media/File:Mrs._Gould's-Sunbird_cropped.jpg and https://www.thoughtco.com/sunbird-facts-4767483 and https://africageographic.com/stories/sunbird-feathers-and-the-sweltering-cost-of-beauty/).
Secondly, it is the southernmost outlier of a genus that is otherwise restricted to tropical islands, north of the Australian continent.
Lichmera is most speciose at an equatorial latitude of about 4 degrees South. The northernmost reach of the genus is 2 degrees 40 seconds North, considerably beyond the equator. By contrast, L. indistincta reaches as far south as 35 degrees in Australia (https://www.inaturalist.org/observations/63368637) - which is farther south than the southernmost tip of Africa (https://latitude.to/articles-by-country/za/south-africa/8352/cape-agulhas).
How can these anomalies be explained?
BIIGEOGRAPHICAL PERSPECTIVE
Meliphagids (Meliphagidae, https://en.wikipedia.org/wiki/Honeyeater) are diverse and abundant in Australasia.
Most forms are somewhat specialised for the consumption of nectar. The most specialised forms have long beaks, suitable for probing flowers and inflorescences.
Some genera of meliphagids are associated with the temperate zone of Australia, whereas others are associated with the tropics.
Genera associated mainly with the temperate zone include
- Acanthorhynchus (https://www.inaturalist.org/observations?taxon_id=12236&view=species),
- Phylidonyris (https://www.inaturalist.org/observations?taxon_id=12630&view=species), and
- Melithreptus (https://www.inaturalist.org/observations?taxon_id=12245&view=species).
The following genera are ambivalent:
- Gliciphila (https://www.inaturalist.org/observations?taxon_id=144339&view=species),
- Gavicalis (https://www.inaturalist.org/taxa/370319-Gavicalis-virescens), and
- Meliphaga (https://www.inaturalist.org/observations?taxon_id=12263&view=species).
Genera associated mainly with the tropics include
Comentarios
Ptilotula
https://www.inaturalist.org/observations?taxon_id=508966&view=species
Melidectes
https://www.inaturalist.org/taxa/12463-Melidectes-ochromelas
Xanthotis
https://www.inaturalist.org/observations?taxon_id=12496&view=species
Nectariniidae are small-bodied, with a long, curved beak, adapted for eating nectar, which is taken while perched rather than while hovering. Certain Meliphagidae are evolutionarily convergent, particularly Acanthorhynchus, Myzomela, and Lichmera. Worldwide, which other birds share this convergent syndrome?
https://www.perplexity.ai/search/nectariniidae-are-small-bodied-edEnUbi0Q7.KVVtzSRCDLg
SUNBIRD-LIKE FRINGILLIDAE
https://www.inaturalist.org/taxa/10684-Himatione-sanguinea
https://www.inaturalist.org/taxa/512251-Drepanis-coccinea
https://en.wikipedia.org/wiki/Hawaiian_honeycreeper
https://upload.wikimedia.org/wikipedia/commons/f/fe/DrepadinidaeSchnabel.jpg
SUNBIRD IN AUSTRALIA, AND ELSEWHERE EAST OF WALLACE'S LINE
Cinnyris frenatus (https://www.inaturalist.org/taxa/1504995-Cinnyris-frenatus) is relevant to the topic of this Post, for several reasons.
Firstly, it is one of the few members of Nectariniidae that have crossed Wallace's Line (https://www.perplexity.ai/search/which-nectariniidae-occur-east-utOahbY7TBuia9FJEXiKKA).
Secondly, it is the only member of Nectariniidae that occurs in Australia, where it is sympatric with Lichmera indistincta in northeastern Queensland.
Thirdly, it is sympatric with Lichmera in North Maluku.
Meliphagidae tend to have inconspicuous colouration. This applies to a large extent even to the small-bodied, long-billed spp. resembling sunbirds (Nectariniidae) morphologically. In particular, iridescence is absent in Meliphagidae while common in sunbirds.
Even in genus Myzomela, a species (namely Myzomela obscura, https://www.inaturalist.org/taxa/12376-Myzomela-obscura) sympatric with Nectarinia frenatus (https://www.inaturalist.org/taxa/1504995-Cinnyris-frenatus) is extremely dull-coloured.
However, the difference is not categorical. Dull colouration occurs one sunbird in southern Africa, viz. Cyanomitra olivacea (https://www.inaturalist.org/taxa/145136-Cyanomitra-olivacea), which is restricted to rainforest (sensu lato).
Evolutionary convergence seems strongest between Myzomela obscura (https://www.inaturalist.org/taxa/12376-Myzomela-obscura and https://animalinformation.com/animal/dusky-myzomela/) in Australia and Cyanomitra olivacea (https://www.inaturalist.org/taxa/145136-Cyanomitra-olivacea) in southern Africa.
Both forms are dull-coloured and associated with dense vegetation, and the Australian meliphagid is actually slightly more iridescent than the southern African nectariniid.
However, the beak is longer in the southern African species (25.5-30 mm, https://www.inaturalist.org/observations/237759940) than in the Australian species (https://en.wikipedia.org/wiki/Dusky_myzomela#/media/File:Myzomela_obscura_-_Daintree_Villiage.jpg).
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