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Margaret Kinnaird and Timothy O’Brien’s The Ecology & Conservation of Asian Hornbills: Farmers of the Forest

The views expressed are those of the author and are not necessarily those of Scientific American.


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Kinnaird & O'Brien (2007), front cover.

Hornbills are among the most charismatic, fascinating and awesome of birds, yet surprisingly little is known about them, dedicated studies are few, and they are incredibly elusive and hard to study. Approximately 60 hornbill species occur across tropical Africa and Asia, and also in the Middle East and Australasia. These are birds of superlatives. The largest species have wingspans of over 1.5 m and weigh as much as 6 kg (in the case of the Southern ground hornbill Bucorvus leadbeateri); some (the Great hornbill Buceros bicornis and Southern ground hornbill) can reportedly live for more than 60 or even 70 years. Sexual dimorphism is extreme in some species, with the males of some being as much as 66% larger than the females. Hornbills are slow to mature, Buceros not breeding until four or five years of age.

Hornbills are also birds of splendid and remarkable anatomy. Great casques that form huge cylinders or curved, rhino-like horns decorate the heads of some species. Furrows, grooves and serrations sometimes mark their great, curved bills; giant, lavish eyelashes, enormous tail feathers and brightly coloured neck and facial skin are present in some species; and fused cervical vertebrae and bilobular kidneys are peculiar to the group. The chicks of some hornbills possess paired air sacs located on either side of the dorsal midline, the function of which (if they have one) is completely unknown.

Remarkable casque anatomy of Rhinoplax, the Asian Helmeted hornbill. At top: cross-section of casque and bill, showing massively reinforced casque (image by Mathew Wedel; specimen in NHM, London); photo below by Doug Janson, licensed under Creative Commons Attribution-Share Alike 3.0 Unported license.

They are also birds of incredible habits. In most, the female becomes walled up – self-incarcerated – within the nest chamber; the Helmeted hornbill Rhinoplax vigil engages in aerial jousting contents [adjacent photo of live Rhinoplax by Doug Janson]; some species ‘paint’ their feathers and rhamphotheca with the oily secretions of their under-tail glands; and co-operative breeding is the norm in some groups of species (like the Anorrhinus brown hornbills). As large, slow-breeding animals that typically rely on large tracts of forest and reliable access to fruits and cavities in trees, hornbills are seriously endangered by habitat loss and degradation, and potentially by climate change and selective hunting.

Margaret Kinnaird and Timothy O’Brien’s 2007 The Ecology and Conservation of Asian Hornbills [previously mentioned here on Tet Zoo] is not a popular retelling of other people’s research on these fascinating birds, but a major piece of primary literature that presents, analyses and discusses a huge amount of new data (Kinnaird & O’Brien 2007). It is thus more like a monograph on the diversity, distribution, evolution, behaviour and conservation biology of Asian hornbills. Numerous subtitled sections, sidebars of text, graphs and tables of data feature throughout. The volume is very much required reading for anyone seriously interested in the biology, evolution, ecology and conservation of hornbills, but it’s comprehensive enough and well-illustrated enough to be of broader appeal as well. A colour plate section features a selection of beautiful, spectacular photos by Tim Laman. Small drawings by Jonathan Kingdon also feature throughout the book.

Great questions about hornbills

At top: Rhinoceros hornbill pair (image by JP Bennett); below: Knobbed hornbill or Sulawesi wreathed hornbill Aceros cassidix (image by Tobias). Images licensed under Creative Commons Attribution-Share Alike 2.0 Generic license.

There are several great questions about hornbills, and I hoped that some or all might be discussed or even answered here. How is the hornbill casque used? Does hornbill behaviour or ecology give us an insight as to which pressures contributed to casque evolution? How is the casque formed in anatomical terms? What role do hornbills play in the distribution of plant seeds and are they ‘keystone’ frugivores? How dependent are they on pristine areas of forest, and can they maintain viable populations in secondary or disrupted forest? How and why did their remarkable breeding strategy evolve? Do they find fruit (a notoriously ephemeral and sometimes unpredictable resource in the tropics) thanks to a well-developed memory, or are they merely opportunistic? How has their evolution and distribution been shaped by that of other fruit-eating groups, like primates? And so on. We’re not in the position to answer or even test many of these questions adequately for the simple reason that the relevant data hasn’t been collected (though note that some have been studied since Kinnaird & O’Brien (2007) was published: see Viseshakul et al. (2011) and Gonzalez et al. (2013a)). Nevertheless, Kinnaird and O’Brien provide copious data relevant to these issues, and discuss them within context. [Adjacent photos by JP Bennett and Tobias.]

Hmm, this is all seeming a bit familiar. Did similar evolutionary pressures drive the evolution of hornbill, cassowary and ornithischian casques and crests? It looks plausible that, yes, they did. Images by Darren Naish.

Because the hornbill casque only develops at sexual maturity and often exhibits sexual dimorphism (it’s usually larger in males than in females), it seems plausible that it functions as an indicator of maturity, and evolved within the context of sexual selection pressure (as is probably the case for other cranial casques and crests in other archosaurs: Hone et al. 2012, Hone & Naish 2013). The concept that the casques are ‘species identification badges’ lacks compelling support, and might be contradicted by hybridisation events recorded between anatomically distinct species (Chamutpong et al. 2013). Adding support to a sexually selected role is the fact that the casques of some hornbill species seemingly function as acoustic resonating chambers used to broadcast their territorial vocalisations (Alexander et al. 1994) and that those of others are heavily reinforced internally and used in aerial head-butting contents (Kinnaird et al. 2003). However, suggestions have also been made that the heavy casques of some hornbills (the Helmeted hornbill in particular) help the bill work as a hammer.

The degree and distribution of sexual dimorphism in hornbills is unusual: some species are monomorphic, others have males that are slightly larger than females, and others have males that are more than twice as large as females (Kinnaird & O’Brien 2007). Quite why this range of dimorphism occurs, and why it’s distributed in the way that it is, remains mysterious, since there are few consistencies within particular hornbill lineages, or within species that share given regions or islands. More studies that link ecology and behaviour with phylogeny and distribution are much needed. [Image below by Magalhães.]

Sexual dimorphism is slight or just about absent in some hornbills, but well developed in others. The awesome Rufous hornbill (Buceros hydrocorax) is especially interesting in that some subspecies (like B. h. hydrocorax on Luzon) are monomorphic while others (like B. h. mindanensis on Mindanao) are strongly dimorphic. Image by Magalhães, licensed under Creative Commons Attribution-Share Alike 3.0 Unported license.

Hornbills: the historical perspective

While mostly based on the conservation biology, current threats, and future of hornbills, a substantial section of the book reviews the evolutionary history of these birds. Based on the fossil record of their close relatives (hoopoes and wood-hoopoes and their fossil kin), hornbills must have originated in the Eocene. However, essentially nothing is known in the way of their fossil record until the Miocene, and even then remains are scant and not especially informative with respect to patterns and trends in the evolution of the group (Naish 2012).

Bucorvids, or ground hornbills: the sorts of hornbills that might have been ancestral for Asian hornbills. Skull image by Mark Witton; photo by Darren Naish. From Naish (2012).

Of the several different phylogenetic hypotheses that have been published, most agree that ground hornbills (Bucorvus) are the sister-group of most remaining hornbills, and that early hornbill evolution occurred in Africa. Kinnaird & O’Brien (2007) favour the view that a hypothetical ancestral hornbill – they call it a ‘proto-Buceros’ and imagine it as a large, territorial, carnivorous hornbill – descended from Bucorvus-like ancestors and gave rise both to (assumed) endemic African taxa like Tockus and Tropicranus, and to a more forest-adapted, frugivorous lineage that moved into Asia. Here, the group radiated extensively, later reinvading Africa to give rise to Ceratogymna and Bycanistes. This model is more or less consistent with the topologies recovered in recent phylogenetic analyses (Gonzalez et al. 2013b).

Kinnaird & O’Brien (2007) provide an extensive discussion of hornbill phylogeny and biogeography in southeast Asia and northern Australasia, discussing the key features, distribution and biology of each hornbill genus in turn. Hornbill biogeography across the so-called Asian hornbill realm is an area made highly complex by the fact that different parts of the Sunda Shelf region were exposed and submerged at different points in the geological past, and that forests, woodlands and savannahs waxed and waned across this region in step with climatic cycles. Hornbills must have employed overwater dispersal at times: even during those parts of the Pleistocene when sea levels were about 180 m lower than present, the Philippines, for example, were separated from Borneo by long stretches of water, and yet members of the group ended up here in the form of several tarictic hornbills, and certain Buceros, Anthracoceros and Aceros species.

One of many illustrations from Kinnaird & O'Brien (2007) illustrating the ranges of hornbill taxa: this one concerns the Rhyticeros species... they should have reached (or passed through) Flores, Timor, Sulawesi and perhaps Australia.

From a historical perspective, the most interesting case of all concerns Rhyticeros, since these occur on New Guinea and some of the surrounding islands, but are otherwise birds of peninsular south-east Asia, Borneo, Sumatra and Java. The Rhyticeros species are “known as the great hornbill dispersers [being able to] fly 10-15 km in a day” (Kinnaird & O’Brien 2007, p. 30), and their absence from Sulawesi, Flores, Timor and even Australia is puzzling, since the birds either passed across these areas in getting to where they are today, or are close enough for them to be within easy flying distance. We might hope for fossils, archaeological specimens or even ethnic tales that demonstrate or hint at the presence of Rhyticeros hornbills in these regions, but nothing like this has been reported yet (Meijer 2014).

“Farmers of the forest”

Hornbills (this is a Great hornbill) are keystone species in the arboreal realm, playing a crucial role in the dispersal of seeds. Image by Lip Kee Yap, licensed under Creative Commons Attribution-Share Alike 2.0 Generic license.

Hornbills are specialised frugivores, able both to ingest huge quantities of fruit in a short period of time and (almost certainly) able to successfully capture and metabolise the very low protein concentrations present in many of the fruits they eat. Fruits are so crucial to hornbills that Kinnaird & O’Brien (2007) discuss fruit diversity and biology, and the importance to hornbills of the species concerned, at length. In keeping with other studies on tropical ecology, figs are emphasised as a keystone resource, searched for and utilised by frugivores even when other fruits are available (it should be noted that figs contain over 750 species, over 500 of which occur within the Asian hornbill realm). Chapter 4 – ‘Feeding ecology; how to survive on fruits’ – includes a huge amount of data and discussion as goes the figs and the other fruits utilised by hornbills. [Adjacent photo by Lip Kee Yap.]

Despite their efficiency as processors and digesters of fruit, hornbills still need to consume 60-600 g of them per day, quantities equivalent to 20-33% of their body weight (Kinnaird & O’Brien 2007). Presumably as a consequence of their fruit-rich diet, they hardly ever drink, and seem especially efficient at processing water. Kinnaird & O’Brien (2007) note that this may be linked to the unusual, bilobed form of hornbill kidneys. This efficient water extraction also almost certainly explains why hornbill faeces are drier than tends to be the case for birds, and this is turn might help explain how dung came to be co-opted as a nest-building material in the group.

A future for hornbills?

Palawan hornbills (Anthracoceros marchei): one of several species whose range has been extensively fragmented in recent decades. Image by Llimchiu, licensed under Creative Commons Attribution-Share Alike 3.0 Unported license.

The last section of The Ecology and Conservation of Asian Hornbills is devoted to the threats that face hornbills and their environments. Logging, the spread of plantations and loss of connected forest tracts, the ecology of fire, human population expansion, poor management, government corruption, hunting, fuelwood collection, local poverty, the development of infrastructure and other factors paint a highly complex picture of interaction, the links between them being confusing, sometimes counter-intuitive, complicated and under-researched. It is a deeply topical subject given the current pace of habitat change in the Asian hornbill realm and the near-unstoppable, unregulated monster that is the palm oil industry. [Adjacent photo by Llimchiu.]

Exactly what this grand, evolving mess means for the distribution and health of hornbill populations, and for sympatric plants and animals, is neither simple nor clear. Urbanisation, for example, means that people may have less impact on forests, and hence on hornbills, and also that regulations and rules concerning land-use will increasingly come into play… theoretically, that is. Indeed, as Kinnaird & O’Brien (2007) discuss, collusive corruption, bribery and unregulated logging have been serious problems across the hornbill realm, especially in Indonesia, the Solomon Islands and Papua New Guinea.

Forest decline across Lampung Province, Sumatra. One of numerous graphs, maps and tables on Asian habitat change from Kinnaird & O'Brien (2007).

Anyway, as goes the future, hornbill species are under threat as forest blocks are broken up, degraded and made ever more accessible to hunters, loggers and others who exploit hornbill habitats. Birds like hornbills may persist across such fragmented landscapes, but at lower population densities. However, some studies indicate that big, frugivorous birds and other animals are relatively resilient to the activities of the logging industry or, counter-intuitively, may even benefit from them (Plumptre & Greiser-Johns 2001). Caveats that need to be kept in mind are that the term ‘frugivore’ is slightly ambiguous and not used consistently across all studies, and that it may be dangerous or misleading to assume that what goes for one hornbill species may go for another (Datta (1998) found that Great hornbills, Oriental pied hornbills Anthracoceros albirostris and Wreathed hornbills Rhyticeros undulatus differed in how they responded to logging disturbance). Kinnaird & O’Brien (2007) discuss simulations and projections that pertain to forest fragmentation and what it means for hornbills – there is, again, a huge quantity of data and discussion here.

There aren't many hornbill toys: here's a Rhinoceros hornbill (l) and Great hornbill. Lest you think this image is out of place, remember that toys and other bits of paraphernalia can serve useful roles in education and promoting environmental and zoological awareness. Image by Darren Naish.

The Ecology & Conservation of Asian Hornbills: Farmers of the Forest is excellent and data-packed and will be used regularly by those interested academically in hornbills, in the ecology or biology of tropical forest birds, or in avian conservation in the tropics. It is definitely not a general guide to hornbills or to Asian hornbills as a whole, however, and should be considered primarily focused on seed dispersal and ecology, and on conservation. As usual, the price is problematic and means that it is out of reach to interested amateurs and those without grants or institutional support. In summary, it is a highly impressive and important tour-de-force that provides a wealth of information on the past, present and future of Asian hornbill biology.

Margaret F. Kinnaird and Timothy G. O’Brien 2007. The Ecology and Conservation of Asian Hornbills: Farmers of the Forest. University of Chicago Press, Chicago. ISBN 13:978-0-226-43712-5, pp. 315. £47.50. Buy it here.

Hornbills have been discussed at Tet Zoo on several previous occasions. See…

Refs – -

Alexander, G. D., Houston, D. C. & Campbell, M. 1994. A possible acoustic function for the casque structure in hornbills (Bucerotidae). Journal of Zoology 233, 57-67.

Chamutpong, S., Ponglikitmongkol, M., Charoennitikul, W., Mudsri, S. & Poonswad. P. 2013. Hybridisation in the wild between the Great hornbill (Buceros bicornis) and the Rhinoceros hornbill (Buceros rhinoceros) in Thailand and its genetic assessment. Raffles Bulletin of Zoology 61, 349-358.

Datta, A. 1998. Hornbill abundance in unlogged forest, selectively logged forest, and a forest plantation in Arunachal Pradesh, India. Oryx 32, 285-294.

Gonzalez, J.-C. T., Sheldon, B. C., Collar, N. J. & Tobias, J. A. 2013b. A comprehensive molecular phylogeny for the hornbills (Aves: Bucerotidae). Molecular Phylogenetics and Evolution 67, 468-483.

- ., Sheldon, B. C. & Tobias, J. A. 2013a. Environmental stability and the evolution of cooperative breeding in hornbills. Proceedings of the Royal Society B 280, 20131297.

Hone, D. W. E., Naish, D. & Cuthill, I. C. 2012. Does mutual sexual selection explain the evolution of head crests in pterosaurs and dinosaurs? Lethaia 45, 139-156.

- . & Naish, D. 2013. The ‘species recognition hypothesis’ does not explain the presence and evolution of exaggerated structures in non-avialan dinosaurs. Journal of Zoology 290, 172-180.

Kinnaird, M. F., Hadiprakarsa, Y.-Y. & Thiensongrusamee, P. 2003. Aerial jousting by Helmeted hornbills Rhinoplax vigil: observations from Indonesia and Thailand. Ibis 145, 506-508.

- . & O’Brien, T. G. 2007. The Ecology and Conservation of Asian Hornbills: Farmers of the Forest. University of Chicago Press, Chicago.

Meijer, H. J. 2014. The avian fossil record in Insular Southeast Asia and its implications for avian biogeography and palaeoecology. PeerJ 2:e295 http://dx.doi.org/10.7717/peerj.295

Naish, D. 2012. Birds. In Brett-Surman, M. K., Holtz, T. R. & Farlow, J. O. (eds) The Complete Dinosaur (Second Edition). Indiana University Press (Bloomington & Indianapolis), pp. 379-423.

Plumptre, A. & Greiser-Johns, A. 2001. Changes in primate communities following logging disturbance. In Fimbel, R. A., Grajal, A. & Robinson, J. G. (eds) The Cutting Edge: Conserving Wildlife in Logged Tropical Forests. Columbia University Press, New York, pp. 71-92.

Viseshakul, N., Charoennitikul, W., Kitamura, S., Kemp, A.C., Thong-aree, S., Surapunpitak, Y., Poonswad, P. & Ponglikitmongkol, M., 2011. A phylogeny of frugivorous hornbills linked to the evolution of Indian plants within Asian rainforests. Journal of Evolutionary Biology 24, 1533-1545.

Darren Naish About the Author: Darren Naish is a science writer, technical editor and palaeozoologist (affiliated with the University of Southampton, UK). He mostly works on Cretaceous dinosaurs and pterosaurs but has an avid interest in all things tetrapod. His publications can be downloaded at darrennaish.wordpress.com. He has been blogging at Tetrapod Zoology since 2006. Check out the Tet Zoo podcast at tetzoo.com! Follow on Twitter @TetZoo.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. John Harshman 1:18 pm 04/22/2014

    …ground hornbills (Bucorvus) are the sister-group of most remaining hornbills…

    “most”?

    Link to this
  2. 2. naishd 1:24 pm 04/22/2014

    I wondered if anyone might comment on that. I used “most” since there are some studies (Woodruff & Srikwan 2011) where Bucorvus is not the sister-taxon to all other hornbills: they recovered a Bucorvus + Bycanistes clade.

    Woodruff, D. S. & Srikwan, S. 2011. Molecular genetics and the conservation of hornbills in fragmented landscapes. In Poonswad, P. (ed) The Asian Hornbills: Ecology and Conservation. National Center for Genetic Engineering and Biotechnology, Bangkok, pp. 257-264.

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  3. 3. Andreas Johansson 2:46 pm 04/22/2014

    Sexual dimorphism is extreme in some species, with the males of some being as much as 66% larger than the females.

    and

    males that are larger than females by a factor of two or three

    presumably use different size metrics? Say, wingspan in the former and weight in the second?

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  4. 4. naishd 3:24 pm 04/22/2014

    Oops. Let me check that. Watch this space.

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  5. 5. naishd 3:40 pm 04/22/2014

    Ok. Kinnaird & O’Brien (2007, p. 35) state: “Within a genus there can be great variation in body sizes; body mass varies by a factor of 2.3 among male Buceros, and by a factor of 3 among female Aceros. Within species, size dimorphism between males and females ranges from nonexistent to extreme with males up to 66% larger than females”. I’m pretty sure I became confused, and mistook intrageneric size variation for the range of sexual size variation. Thanks for flagging this up, Andreas.

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  6. 6. John Harshman 4:22 pm 04/22/2014

    a Bucorvus + Bycanistes clade

    That’s highly bizarre, and I wonder how they did it. I don’t have access to Woodruff & Srikwan, but the result is massively inconsistent with both Gonzalez et al. and Viseshakul et al.

    WTF?

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  7. 7. naishd 4:26 pm 04/22/2014

    John: yeah. Check out comments on Woodruff’s site here. I think the sequences came from feathers… I haven’t seen the article concerned either, only the resulting trees.

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  8. 8. LeeB 1 7:18 pm 04/22/2014

    That distribution pattern of Rhyticeros is interesting and familiar; a very similar distribution pattern occurs in the pitcher plant Nepenthes ampullaria which occurs on Peninsula Malaysia and Southernmost peninsula Thailand, on Sumatra and Borneo, and also on the island of New Guinea.
    But it is absent on all the intervening islands.

    This suggests that the climate during glacial periods was different on Sulawesi and the Makalu islands than today, probably wetter, and therefore more suitable for rainforest adapted species.

    Perhaps there are other species with this distribution pattern.

    LeeB.

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  9. 9. LeeB 1 11:37 pm 04/22/2014

    Oops I should have typed Maluku.

    LeeB.

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  10. 10. vdinets 4:17 am 04/23/2014

    Could the huge casque of some spp. be an honest signal/handicap? Should be really difficult to fly with.

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  11. 11. Dartian 5:08 am 04/23/2014

    Darren:
    Small drawings by Jonathan Kingdon also feature throughout the book.

    Ooh! Kingdon is one of my favourite contemporary wildlife artists. Too bad that this book is on the expensive side…

    (assumed) endemic African taxa like Tockus”

    Nitpick: Tockus may have originated in Africa, but one species, T. nasutus, is currently also found in Arabia (but I’m sure you knew that).

    “Rhyticeros [...] absence from Sulawesi, Flores, Timor and even Australia is puzzling

    Apologies for speculating (speculation, however, becomes almost irresistable in cases like this), but the absence of Rhyticeros from Sulawesi might conceivably be due to competitive exclusion by other local hornbill species, whereas the relatively small islands of Flores and Timor might lack enough suitable habitat (either now or in the recent geological past) for these hornbills. What’s most surprising, at least IMO, is the fact that these hornbills apparently failed to colonise Australia – even though there were land connections between New Guinea and Australia in the Pleistocene.

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  12. 12. Jerzy v. 3.0. 5:17 am 04/23/2014

    Among many things hornbill-related:
    Head-butting in Helmeted Hornbill (the only hornbill which head-butts): this was for the long time a sort of ornithologists fairy tale, known from local folklore but not positively observed by any naturalist. Strange that it is so rare behaviour in this species.

    Presence of casque in both sexes strongly suggests that there is sexual selection operating in both sexes. Perhaps it is related to the defense of nest cavity? Some parrots have quite bizarre adaptations of females to defend nest cavities.

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  13. 13. naishd 5:32 am 04/23/2014

    Thanks for comments, much appreciated. Dartian: you’re right about Tockus in Arabia (it’s the Middle Eastern animal I mentioned earlier in the article: specifically, T. (= Rhynchaceros) nasutus, the African grey hornbill), but, yes, this would still be consistent with Tockus being ancestrally African. Actually, a question: is it still right to describe a taxon as endemic to a region when one of its lineages has moved out of said region?

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  14. 14. naishd 5:39 am 04/23/2014

    Jerzy: interesting stuff. As goes casques (and other ornaments, like brightly coloured facial skin) being present in both sexes, my suspicion is that this is another group where mutual sexual selection is at play – females are selecting high-quality males as mates, but males need to be choosy about female partners too. That would seemingly make sense in this instance, given the biparental care and cooperation involved in breeding. I think that MSS is also at play in cassowaries: in that case, males (who provide essentially all parental care) may be selecting fit females, and evaluating their quality based on their ornaments (casques, wattles and skin colour). These are hypotheses that still require testing.

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  15. 15. Dartian 2:04 am 04/24/2014

    Darren:
    is it still right to describe a taxon as endemic to a region when one of its lineages has moved out of said region?

    Technically, no.

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  16. 16. irenedelse 2:55 am 04/24/2014

    The importance of figs in the diet of hornbills and other frugivores is interesting. Botanically, figs are false fruits: the individual fig or syconium is really a fleshy receptacle for the flowers, which are pollinated by tiny wasps laying their eggs inside the figs. There’s a complex symbiotic relationship between fig trees and pollinating wasps, with wasp larvae developing inside the fig. Some of the wasps also die inside the syconium and the plant uses a special enzyme (ficaine) to “digest” the bodies and re-use the proteins they contain.

    So I was wondering if part of the interest of frugivores in figs came from the extra protein potentially offered by the insect larvae or their by-products? Does the book discuss this? Or am barking up the wrong sycamore tree here?

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  17. 17. naishd 4:29 am 04/24/2014

    Dartian (comment # 15): thanks; I agree that this would be technically incorrect. But what about saying “the group is endemic to Africa [as in, it originated there] but later spread to Asia [or whatever]“. Is this wrong? I’m really not sure, since ‘endemic’ is sometimes used to mean ‘originated in a certain place’, not just ‘restricted to a certain place’. Hmm.

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  18. 18. Dartian 5:52 am 04/24/2014

    Darren:
    But what about saying “the group is endemic to Africa [as in, it originated there] but later spread to Asia [or whatever]“. Is this wrong?

    The problem there is that if one uses the word ‘endemic’ in that sense, where does one stop? E.g., if you can say that “Tockus hornbills are endemic to Africa”, what’s stopping you from saying that “humans Homo sapiens are endemic to Africa”? (AFAWK, both taxa almost certainly originated in Africa.)

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  19. 19. Dartian 6:04 am 04/24/2014

    Perhaps some of the confusion regarding the correct use of ‘endemic’ comes from the fact that this word is used somewhat differently in non-biogeographical – and non-biological – contexts? E.g., a medically trained person might say that “malaria is endemic to Africa” and by that mean that this disease is found there (but it’s not necessarily restricted to that place).

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  20. 20. naishd 6:21 am 04/24/2014

    Yeah, I’m not disagreeing, just curious.

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  21. 21. DavidMarjanovic 10:21 am 04/24/2014

    Some of the wasps also die inside the syconium and the plant uses a special enzyme (ficaine) to “digest” the bodies and re-use the proteins they contain.

    No need for scare quotes.

    ‘endemic’ is sometimes used to mean ‘originated in a certain place’, not just ‘restricted to a certain place’

    Really? I’ve never seen that.

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  22. 22. irenedelse 12:58 pm 04/24/2014

    David:
    Thanks for the confirmation that digest is the proper term here, my biology days are such a long way off that they may well be from a previous life.

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  23. 23. Andreas Johansson 3:06 pm 04/24/2014

    Re “endemic”, Wiktionary list all three usages mentioned above:
    http://en.wiktionary.org/wiki/endemic

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  24. 24. naishd 6:51 pm 04/24/2014

    irenedelse (comment # 16): the book does not talk about the idea that fig ingestion by hornbills might involve the benefits inferred from the insects inside the fruit… at least, not so far as I recall. Does this symbiosis with parasitic wasps apply to all figs, or most, or some, or what? It’s been a while and I can’t recall. My standard source of reference on figs as seen from the tetrapod’s-eye-view is…

    Shanahan, M., So, S., Compton, S. G. & Corlett, R. 2001. Fig-eating by vertebrate frugivores: a global review. Biological Reviews 76, 529-572.

    Oh, and — yay, 23 comments. Now we can move on…

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  25. 25. vdinets 7:58 pm 04/24/2014

    Do figs really utilize the proteins from dead wasps? I find it a bit difficult to believe. Carnivorous plants don’t “eat” insects in the same sense as animals eat. They don’t use their prey to get energy or amino acids; instead, they just use it as fertilizer, an extra source of nitrogen, calcium, phosphorus and probably potassium.

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  26. 26. irenedelse 3:05 am 04/25/2014

    Darren:
    Pollination by wasps that lay their eggs in the immature fruit is the norm in fig trees, from what I gather:
    http://en.wikipedia.org/wiki/Ficus#Fig_fruit_and_reproduction_system

    It’s a mutualistic relationship, often species-specific, and coevolution between fig trees and pollinating fig wasps (Agaonids) has been suggested. The Wikipedia article mentions “the frequent presence of insect larvae” in the figs, but alas with no specific reference.

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  27. 27. irenedelse 3:23 am 04/25/2014

    vdinets:
    That’s a good point. I’m afraid I just read that fig trees secreted a protease to break down the dead insects’s bodies and jumped to the conclusion that the plant must then re-use the proteins, it’s not what the references say. My bad.

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  28. 28. DavidMarjanovic 5:12 am 04/25/2014

    an extra source of nitrogen

    …so they can build new amino acids. Same thing as utilizing the amino acids directly, just takes longer.

    Link to this
  29. 29. Jerzy v. 3.0. 7:26 am 04/25/2014

    @irenedelse
    Protein content in figs is rom the plant, insects are minuscule part of the mass.

    #23
    Near-endemic would be correct. But south Arabian Peninsula is Afrotropic zoogeographically.

    @general
    It would be curious to know if sealing of nest chambers in hornbills is especially hard, and if hornbill neck adaptations are especially for breaking the nest chamber?

    Also, what happens if a female hornbill loses the nest immediately after sealing? Is she able to stop dropping all the feathers simultaneously?

    Link to this
  30. 30. Heteromeles 10:21 am 04/25/2014

    There’s probably as much protein in the seeds as in the wasp eggs that replace the seeds, possibly even more (since the wasp eats the seed). I’m wondering about the protease secreted by the figs too.

    There’s probably a good paper in there: is the fig secreting a protease as an antiseptic (to clean up the dead wasps, and keep them from rotting and destroying the fruit), or as a digestive aid? Carnivorous plants are known to have hairs specialized for nutrient uptake (remember that a plant hair is a specialized cell, not a keratinous structure). Off hand, I don’t know of any such cells in a fig syconium. Also, figs aren’t close to other carnivorous plants in evolutionary terms. Doesn’t mean they couldn’t pull a bit of nitrogen from the wasps, but wouldn’t the slowly digesting wasps decrease the fruit value and endanger the baby wasps? There’s probably a way for some clever grad student to figure out how to answer this.

    By the way, there are fruits and there are functional fruits (aka “eco-berries” to those who like to annoy plant anatomists–it’s the ecological equivalent of a berry, whatever it is structurally). A syconium is a functional fruit built from stem tissue, but it’s not worth getting too worried about whether it’s a fruit, a false fruit, an “eco-berry” or an inside-out mulberry, unless you’re a plant anatomist.

    As for why hornbills eat figs, isn’t it because they’re sort of the McDonalds of the rainforests, meaning that they’re in the business of owning the prime real estate in a particular area and finance that by providing a predictable product that’s cheap to get?

    Link to this
  31. 31. Yodelling Cyclist 10:23 am 04/25/2014

    *sotto voce*: crocodile skulls.

    Link to this
  32. 32. John Scanlon FCD 11:00 am 04/25/2014

    ‘Autochthonous’ should be a useful word for a group that’s not strictly endemic any more, but it doesn’t get much love these days.
    Lots of forest groups never made it from New Guinea to Australia, and it’s generally thought that the Torres landbridge was a long stretch of open savannah. A lot would depend on the habits of the particular species, and the detailed distribution of necessary resources, but it seems odd to regard this as ‘surprising’ (I’ve never seen a hornbill outside a zoo, so I’d have chosen a different adjective).
    Figs are highly iconic and culturally significant trees in Australia (e.g. Moreton Bay figs in Sydney’s parks) but there seem to be remarkably few vertebrate species that really depend on them: Figbird, Gulf Snapping Turtle, Flying Foxes, probably some pigeons. Pretty important for Greater and Western/Spotted Bowerbirds, and Northern Quoll… but it’s hard to imagine any habitat in Australia being able to support monkeys or hornbills.

    Link to this
  33. 33. irenedelse 2:05 pm 04/25/2014

    Come to think of it, all sorts of fruits growing in a rainforest are likely to be hosts to insect larvae at any given time, be it from a mutually beneficial relationship or to simple parasitism. It matters to the plant, but from the frugivore’s perspective, it’s all the same…

    Link to this
  34. 34. Torvosuchus 6:09 pm 04/25/2014

    Regarding figs, I’ve seen in several sources that figs fruit essentially year-round, and thus are a vital food source for frugivores in monsoon forests that experience a distinct dry season (when other fruit-bearing plants are barren).

    I can’t find much peer-reviewed work to back that up, but I found at least a couple that mention something to that effect. Not all figs or all ecosystems with figs necessarily work that way, from what I can gather. See this and this.

    Link to this
  35. 35. Dartian 11:30 am 04/27/2014

    Jerzy:
    south Arabian Peninsula is Afrotropic zoogeographically

    That may be so, but the African continent is not the same thing as the Afrotropical zoogeographic realm.

    Link to this

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