INTRODUCTION
Australia and southern Africa are ecologically comparable.
Both landmasses possess a range of climates, from mediterranean and adjacent arid to summer-rainfall tropical. Furthermore, in both cases the substrates tend to be nutrient-poor, owing to profound weathering on a largely flat topography.
In both Australia and southern Africa, there are many and various plants pollinated mainly by birds. On both landmasses, the flowers/inflorescences in question tend to be bright-hued, bearing copious nectar deep within a structure that makes it adaptive for nectarivorous animals to have long mouthparts, including long, curved beaks in the case of birds.
It is widely believed that certain Meliphagidae in Australia and certain Nectariniidae in southern Africa show evolutionary convergence, as part of an adaptive syndrome of mutualism with ornithophilous plants (https://en.wikipedia.org/wiki/Ornithophily).
However, closer scrutiny undermines this 'textbook' interpretation.
The fallacy is evident not only because most meliphagids differ obviously from nectariniids in having relatively large bodies and relatively short beaks. Even when the closest intercontinental counterparts are carefully compared, noteworthy disparities emerge.
Meliphagids, which are broadly associated with ornithophily, have undergone an extreme evolutionary radiation in Australasia. However, my main finding is that it is the differences between meliphagids and nectariniids that are more significant than the similarities.
NON-CONVERGENT ASPECTS
The main intercontinental differences are as follows.
Firstly, the tongues are remarkably different.
In meliphagids, the tongue is fairly simple except for its length and its fimbriated (brush-like) tip (https://www.merriam-webster.com/dictionary/fimbriated and https://www.perplexity.ai/search/does-the-morphology-of-the-ton-dWPr2lh8Qi.prkVX4Uv7Jg).
By contrast, in nectariniids the tongue is extremely specialised, relative to all nectarivorous birds worldwide (https://www.biorxiv.org/content/10.1101/2024.05.14.594085v1.full.pdf). This is because it operates by means of suction, not capillarity or pressure exerted by the closure of the beak.
In other words, the tongue of nectariniids serves as a drinking straw (https://en.wikipedia.org/wiki/Drinking_straw), the main complication being the distal bifurcation of the straw.
Secondly, no meliphagid has iridescent plumage. By contrast, most nectariniids possess iridescent feathers, at least in males in breeding plumage.
Among meliphagids, the genus most closely approaching iridescence is Myzomela. However, the beak in Myzomela is relatively short, reflecting a relatively generalised diet, lacking any ornithophilous specialisation.
Thirdly and related to the last difference, meliphagids tend to be less sexually dimorphic than nectariniids
Fourthly, no meliphagid builds a 'dome' nest. By contrast, all nectariniids build nests with roofs. The closest convergence is achieved by e.g. Lichmera indistincta, the nest of which is sock-like - but still open at the top.
Fifthly, meliphagids tend to eat honeydew/lerp /manna/extrafloral nectar as well as floral nectar. By contrast, nectariniids have not been recorded eating these alternative sugary exudates.
CLOSEST INTERCONTINENTAL COUNTERPARTS
Please note: in all cases the difference remains that
(My values for body length and body mass refer to adult females.)
The meliphagid Sugomel nigrum (https://www.inaturalist.org/taxa/367631-Sugomel-nigrum, body length 11 cm, body mass 9.5 g) is fairly closely matched with the nectariniid Cinnyris fuscus (https://www.inaturalist.org/taxa/145189-Cinnyris-fuscus and https://thebdi.org/2024/06/04/dusky-sunbird-cinnyris-fuscus/, body length 10 cm, body mass ?8 g).
In both cases,
However, the following differences remain. The meliphagid
The meliphagid Acanthorhynchus superciliosus (https://www.inaturalist.org/taxa/12237-Acanthorhynchus-superciliosus, female length 14 cm, body mass 9 g) is somewhat similar to the nectariniid Anthobaphes violacea (https://www.inaturalist.org/taxa/145130-Anthobaphes-violacea, female length 12 cm, body mass ?7-8 g).
In both cases,
However, differences remains in
Myzomela sanguinolenta (https://www.inaturalist.org/taxa/12443-Myzomela-sanguinolenta, body length 10 cm, body mass 8 g) is fairly similar to Hedydipna collaris (https://www.inaturalist.org/taxa/145122-Hedydipna-collaris, body length 10 cm, body mass 8 g).
The meliphagid actually exceeds the nectariniid in sexually dimorphism in colouration.
Furthermore, both spp.
However,
The intercontinental difference in the nests - in size as well as shape - is illustrated in:
The meliphagid Myzomela obscura (https://www.inaturalist.org/taxa/12376-Myzomela-obscura, body length 13 cm, body mass
? g) is a counterpart for the nectarinid Cyanomitra olivacea (https://www.inaturalist.org/taxa/145136-Cyanomitra-olivacea, body length 13 cm, body mass 9 g).
Both forms
Finally:
Cinnyris frenatus (https://www.inaturalist.org/taxa/1504995-Cinnyris-frenatus, body length 10 cm, body mass ?8 g) of tropical northeasternmost Australia is extremely similar to Cinnyris venustus (https://www.inaturalist.org/taxa/145188-Cinnyris-venustus, body length 10 cm, body mass 7 g) of northeasternmost southern Africa. Both spp. are equatorial to tropical. The colouration is similar, including the sexual difference.
Is the Australian species the less sexually dimorphic in colouration?
This, the closest matching of all, is - of course - not a case of evolutionary convergence. This is because the intercontinental counterparts belong to a single, exceptionally widespread and speciose (total 63 spp.) genus of nectariniids.
DISCUSSION
In general, the norm in meliphagids is relatively large-bodied and short-beaked, whereas the norm in nectariniids is small-bodied and long-beaked.
However, the intercontinental differences pointed out here cannot be explained by means of phylogenetic constraints and the geographical isolation of Australia.
This is partly because:
Meliphagids have not reached southern Africa, but the converse does not apply. Nectariniids, although originating in Africa/Asia, have in fact reached Australasia - where they have failed to undergo evolutionary radiation.
There are two permanent sea barriers between southeast Asia and first Wallacea (https://en.wikipedia.org/wiki/Wallacea) and then Australasia. The first is called the Wallace Line (https://en.wikipedia.org/wiki/Wallace_Line), and the second is called the Weber Line.
The following nectariniids occur in Wallacea:
The following nectariniids occur in Australasia (https://en.wikipedia.org/wiki/Australasia):
It is noteworthy that C. fuscatus coexists in northeastern Australia with the superficially nectariniid-like meliphagid, Myzomela obscura (https://www.inaturalist.org/taxa/12376-Myzomela-obscura).
Further investigation is warranted of the possible difference between meliphagids and nectariniids in predation on relatively large and venomous spiders. My impression from the literature is that nectariniids are the family more resembling 'arachnophages', in the sense that they use their long beaks not only to probe flowers, but also to kill spiders safely (https://www.inaturalist.org/posts/98889-failure-of-evolutionary-convergence-in-nectarivorous-birds-between-australia-meliphagidae-and-southern-africa-nectariniidae#activity_comment_0590a394-7178-4d76-bec2-11bc68b0e569).
Comentarios
https://onlinelibrary.wiley.com/doi/abs/10.1002/jmor.21513
https://www.perplexity.ai/search/describe-the-mechanism-whereby-XKc5Q4GJS.O9qT7_2fMR2g
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3497234/
https://www.perplexity.ai/search/describe-the-mechanism-whereby-XKc5Q4GJS.O9qT7_2fMR2g
Lichmera indistincta:
https://besjournals.onlinelibrary.wiley.com/doi/full/10.1002/2688-8319.12262
https://www.researchgate.net/publication/371046295_Observations_of_nectarivorous_birds_and_potential_biological_control_agents_in_berry_orchards
https://www.perplexity.ai/search/describe-the-tongue-of-lichmer-BzCqnntsT0uxLdzgJoNHog
Paton and Collins (1989):
https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1442-9993.1989.tb01457.x
https://link.springer.com/article/10.1007/BF00985098
https://www.aavac.com.au/files/2000-17.pdf
https://www.perplexity.ai/search/has-any-member-of-the-nectarin-0iY88OrKSKO5C0VQBB2V4A
Pizzey G (1980) A field guide to the birds of Australia, pages 356-357, re Cinnyris frenatus:
"Many spiders are eaten,,,takes quite large spiders, dismembering them while hovering before their webs".
https://www.perplexity.ai/search/do-any-nectariniids-in-africa-q8meL8wTQMuCpRG1SKagnQ
Lichmera indistincta
https://www.inaturalist.org/taxa/12526-Lichmera-indistincta
body length ?13 cm
body mass 9 g
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