October 22, 2021

tail length in Asian wild asses

(writing in progress)

Nobody seems previously to have noticed the intriguing variation in the length of the tail within the Asian wild ass (Equus hemionus).

The Mongolian wild ass (Equus hemionus hemionus, https://en.wikipedia.org/wiki/Mongolian_wild_ass) is similar in overall appearance to the Indian wild ass (Equus hemionus khur, https://en.wikipedia.org/wiki/Indian_wild_ass). This makes sense for two subspecies of the same widespread species.

However, for some strange reason the tail of the former is much longer than the tail of the latter.

Equus hemionus hemionus









Equus hemionus khur








(writing in progress)

Posted on October 22, 2021 09:42 by milewski milewski | 0 comments | Leave a comment

October 21, 2021

The forgotten domestication of the Eurasian wild ass

Everyone knows that the Asian wild ass (Equus hemionus) has never been domesticated (https://en.wikipedia.org/wiki/Onager and https://phys.org/news/2013-03-secret-wild-asses-negev.html). And everyone is probably wrong. Or, more precisely, forgetful.

If the European form, hydruntinus (https://en.wikipedia.org/wiki/European_wild_ass), is included, the Eurasian wild ass had an exceptionally wide natural distribution from Portugal in the west nearly to Beijing in the east.

This distribution included several of the world's original civilisations, making it unlikely that the Eurasian wild ass would have been exempt from domestication.

Perhaps the most important civilisation to remember is that of Mesopotamia (https://en.wikipedia.org/wiki/Mesopotamia). Here the Eurasian wild ass was the only species of equid available 5000 years ago, in the form of a subspecies combining exceptionally short ear pinnae with diminutive body size (https://en.wikipedia.org/wiki/Syrian_wild_ass and https://web.archive.org/web/20100506003501/http://www.petermaas.nl/extinct/speciesinfo/syrianwildass.htm).

Please see page 18-36 in https://oi.uchicago.edu/sites/oi.uchicago.edu/files/uploads/shared/docs/saoc20.pdf. Bones from Tell Asmar have been identified as Equus hemionus hemippus.

The archaeological depiction of short-eared equids in Mesopotamia 4600 years ago (https://spiritedhorse.wordpress.com/2017/12/23/the-standard-of-ur/) seems to show a domesticated form of the Eurasian wild ass - identified as the 'onager' by F E Zeuner in 1963 (https://www.semanticscholar.org/paper/A-History-of-Domesticated-Animals.-By-F.-E.-Zeuner-Cross/7c57568f42bfb10af5c0ea04ebe4bf2fdaf4f1bc and https://www.cambridge.org/core/journals/antiquity/article/abs/a-history-of-domesticated-animals-by-f-e-zeuner-london-hutchinson-1963-560-pp-355-figs-4-4s/61201B6CFADCC61957C5779D12DC1118). Zeuner's account was later relayed by Anthony Dent (1972) in his book 'Donkey: the story of the ass from east to west') and by Edward Hyams (1972) in his book 'Animals in the service of man: 10,000 years of domestication'.

The Sumerian cart/chariot had two or four-wheels, was manned by two, and was harnessed to four individuals of the 'onager' (https://en.wikipedia.org/wiki/Sumer and http://sumerianshakespeare.com/84201.html).

Note, however, that the subspecies occurring in Mesopotamia was the Syrian wild ass (Equus hemionus hemippus) - not the onager, indigenous to what is now Iran. These subspecies, the former now extinct, can be distinguished by ear length and body size.

Although little more has been written for half a century about this instance of domestication, it remains possible that the Eurasian wild ass was the ancestor of the first form of domestic equid to work in conjunction with the newly-invented wheel (https://www.newscientist.com/definition/the-wheel/).

What looks like the domestic form of the Eurasian wild ass was later replaced in Mesopotamia by the horse (Equus caballus) from the northeast and the donkey (Equus asinus) from the southwest.

The possible reason for this usurpation is that the Eurasian wild ass, being ecologically and physiologically intermediate between horse and donkey, was not as efficient in the service of humans as the two more specialised species with their division of labour.

However, there were probably attempts to hybridise the two species of asses before the Eurasian species was made redundant.

Dent (1972) states: "most asses east of the Euphrates must have an infinitesimal amount of onager blood in their ancestry. Unlike the cross between the ass and the horse, that between the domestic African and the Asiatic wild ass is fertile...in Asia Minor, in Persia, and in Mesopotamia there will have been a brief period...perhaps not more than a few centuries (about 3500 years ago)...during which the African ass and the onager were both in use, the one for pack-traffic and the other for driving. These would be crossed, either deliberately or now and again by accident...so that by the time the pure-bred onager ceased to be used in harness - because it was displaced by the horse in the second millennium B.C. - amid the donkey-stock of Asia east of, roughly, the Orontes River there would be a thin trickle of onager blood in the veins".

Assuming that the Sumerians subjected the Syrian wild ass to enough selective breeding to produce a domestic form, then this may possibly be the only species/subspecies of equid to exist for only a millennium from its origination to its extinction.

One of the reasons why this topic has lapsed is that it is easy to ignore an entity devoid of a name. In the case of the horse, the scientific name caballus is distinct from that of the wild ancestor, ferus. In the case of the donkey, we have asinus vs africanus. What about the hypothetical distinction in the case of the Eurasian form of ass?

In the interests of fostering a search-image for further scrutiny, perhaps we can give the extinct domestic descendent of the Syrian wild ass the working name 'Sumerian ass (Equus hemionus sumer)'?

Posted on October 21, 2021 04:19 by milewski milewski | 5 comments | Leave a comment

October 19, 2021

Did the wild dromedary break the rule of miniaturisation in Arabia?

In a previous Post (October 02, 2020, https://www.inaturalist.org/journal/milewski/archives/2020/10), I pointed out a pattern which is hard to explain biogeographically or ecologically. This is the remarkably consistent miniaturisation in the wild fauna of large mammals on the Arabian Peninsula.

However, there may be one exception: the extinct wild ancestor of the dromedary (Camelus dromedarius). This occurred on the 'horn' of Arabia where Dubai now stands (https://upload.wikimedia.org/wikipedia/commons/c/cd/United_Arab_Emirates_%28orthographic_projection%29.svg). It seems to have lived not in the inland desert but on a mangrove-edged coastal strip on the Strait of Hormuz (https://www.pnas.org/content/113/24/6707 and https://en.wikipedia.org/wiki/Strait_of_Hormuz).

The reason to think that the wild dromedary was not miniaturised is that its domestic descendent far outsizes any species of ungulate indigenous to Arabia or the Sahara - or for that matter the Sahel (Oryx dammah, adult female body mass less than 140 kg, https://en.wikipedia.org/wiki/Scimitar_oryx).

Consider the average body mass of adult females of the dromedary. This is about 500 kg according to Tibary and Anouassi (1997, pages 2-4 in 'Theriogenology in Camelidae: anatomy, physiology, pathology and artificial breeding'). The figure ranges from 350 kg in parts of Kenya and Sudan to 640 kg in Syria.

The corresponding figures for the bactrian camel (Camelus bactrianus, page 10 of same reference) is about 550 kg, ranging from 480 kg in Mongolia to 650 kg in Kyrgystan.

The fact that the bactrian camel is the more massive is unsurprising because it is adapted to seasonally cold climates (https://en.wikipedia.org/wiki/Bergmann%27s_rule).

This climatic difference applies despite the bactrian camel and the dromedary having both been domesticated in the Iranian region.

Whereas the dromedary was domesticated in a warm coastal semi-desert just south of Iran and across the Strait of Hormuz, the bactrian camel was domesticated in a seasonally cold inland semi-desert in northeastern Iran, about 750 km from this strait.

If the wild ancestor of the dromedary was as massive as the domestic form so closely associated with Arabian culture, then this would break the rule of miniaturisation in Arabia. At about 500 kg, the dromedary is at least fourfold more massive than the next-largest ungulate indigenous to Arabia, namely the extinct Syrian wild ass (Equus hemionus hemippus, https://en.wikipedia.org/wiki/Syrian_wild_ass).

However, it remains possible that the relative gigantism of the dromedary is partly owing to the process of domestication - by a combination of hybridisation and selective breeding in prehistoric times.

It seems that artificial hybridisation with the bactrian camel began from the start of the domestication of the dromedary (https://iranicaonline.org/articles/camel-sotor#:~:text=The%20Iranians%20would%20thus%20have,it%20was%20probably%20not%20numerous.).

This was practicable partly because the bactrian camel had already spread, by that time, to southeastern Iran - where it was separated from the site of domestication of the dromedary by little more than a ride in a boat. It seems to have been easy enough, even four thousand years ago, to transport males of the bactrian camel to what is now the United Arab Emirates across the Strait of Hormuz.

Any systematic hybridisation would have doomed the dromedary in the strict sense of a distinct species. However, it might have facilitated the subsequent selective breeding of increased body size, from early in the process of its domestication.

The incentive for boosting the body size of the dromedary would have been to utilise it farther inland, where viable thresholds of drought-tolerance, mobility, production of milk and capacity for labour all depended on body size. And in view of the flexibility of body size in other species of domestic mammals it seems possible that the body mass could have been doubled within a few centuries.

The Syrian wild ass was diminutive and may also have been domesticated (contrary to Wikipedia), at least partly and for a limited period (see https://books.google.com.au/books/about/Donkey_the_Story_of_the_Ass_from_East_to.html?id=CHIvAQAAMAAJ&redir_esc=y). There is no evidence of any artificial boosting of body size in the case of Equus hemionus. However, its roles in domestication were different from those of the dromedary, the main one being draught of vehicles in warfare.

So, which is more likely for the ancestral, wild dromedary of Arabia: that its adult female body mass was about 500 kg from the start or that it was only about 250 kg until an artificial and rapid enlargement which has left no trace of the original diminutive form?

Posted on October 19, 2021 09:51 by milewski milewski | 2 comments | Leave a comment

October 17, 2021

Some reasons why the llama spits

The llama (Lama glama, https://en.wikipedia.org/wiki/Llama), as everyone knows, 'spits' (https://www.youtube.com/watch?v=gF4el-h3Yic and https://www.youtube.com/watch?v=nDi6NPQPAtI and https://www.agriculture.com/family/living-the-country-life/why-llamas-and-alpacas-spit and https://ramshornllamas.com/why-do-llamas-spit-and-how-to-stop-it/).

However, what may not be generally realised is how this relates to the combination of touch-aversion and hornlessness which characterises its wild ancestor, the guanaco (Lama guanicoe, https://en.wikipedia.org/wiki/Guanaco).

Spitting in the llama and the guanaco differs from spitting in humans, and may alternatively be described as non-nasal sneezing (https://www.youtube.com/watch?v=A_6XHB8D9vQ and https://www.facebook.com/watch/?extid=SEO----&v=566353500905689 and https://www.youtube.com/watch?v=AUQiP4FgzDQ and https://www.youtube.com/watch?v=o8cNLVD5pLo and https://www.jukinmedia.com/licensing/view/982504 and https://www.youtube.com/watch?v=bKkNyhq6EHo and https://www.youtube.com/watch?v=rjgDunX2SQk and https://www.youtube.com/watch?v=1bpJl1l3-K8 and https://www.youtube.com/watch?v=OeQsOxeiHjg).

A jet of droplets and aerosol is sprayed with surprising velocity and over a surprising distance while the mouth is only slightly open (https://www.youtube.com/watch?v=HszBEIn7EPo and https://www.facebook.com/watch/?v=4806245422755943).

The substance jet-sprayed is various combinations of saliva and stomach contents (https://www.youtube.com/watch?v=XLJpxhGmtH4). The composition of the 'spit' seems less important than the physical insult delivered. In other words, spitting in the llama and the guanaco does not seem to be a case of chemical defence as much as an unusual form of physical threat.

It is tempting to suggest that we call this behaviour 'agonistic sneezing', which sometimes includes 'vomit-sneezing'. However, this is also unsatisfactory because the llama and the guanaco breathe exclusively through the nose, and their true sneeze is purely nasal. Such are the difficulties of the English language for precise descriptions in science.

Spitting in the llama seems to function similarly to the gesturing that is performed in other ungulates by means of lowered horns or antlers (or lowered forehead in the case of females of many species), or flailing fore hooves. Because the llama and the guanaco lack both head-adornments (at all) and hooves (in a strict sense), and their fang-baring displays are limited by the small size of their caniniform teeth (https://shadyufo.tumblr.com/post/165100306068/what-are-the-differences-between-llama-and-alpaca), it is reasonable that the head might be used in this alternative way in communication.

On page 75 of her book 'Llamas and alpacas: a guide to management' (2006, The Crowood Press), Gina Bromage states: "Llamas and alpacas...express defiant disapproval by spitting. If they wish only to warn, then often they will spit past or away from the other animal, but if they are really angry, they will spit directly at it...Sub-dominant animals rarely dare to spit at the dominant one...Laid-back ears...always precedes spitting".

Also informative is what Bromage writes on page 16: "A well-brought-up llama or alpaca would never deliberately spit at a person, any more than a well-brought-up dog or a horse would bite. Spitting is something that camelids properly reserve for squabbles amongst themselves. However, it is possible accidentally to get caught in the crossfire during a dispute among them. The other circumstances in which people are on the receiving end is where the animal concerned has not been properly trained to respect humans, and then, just as a rogue dog or horse might bite, a llama or alpaca might spit".

To understand these peculiarities, it may help to realise that the llama and the guanaco are among the most touch-averse of ungulates. There is no caressing behaviour in these species, regardless of age or sex. This applies even to maternity: the mother does not clean the newborn, which is left to dry off by itself.

So, although spitting in the llama is not only defensive but also partly aggressive, its meaning seems in certain situations to be 'Respect my personal space!'

Bromage states on pages 79-80: "Alpacas and llamas do not indulge in mutual grooming...they never lick, nibble, tickle or rub each other for mutual benefit (e.g. parasite removal) or pleasure. Even newly delivered mothers do not lick their babies. The effect of this is that the touch of another animal or human is always unwelcome...Llamas and alpacas cannot help having a step-away reflex...Their handlers must understand that to tolerate touch and not be alarmed or distressed by it...it has to overcome a very deeply rooted sense of alarm".

This syndrome is so strongly developed in the llama that, if the infant is subjected to cuddling by humans (e.g. https://www.startribune.com/minnesotans-are-hugging-llamas-as-pandemic-pick-me-up/600037226/ and https://www.airbnb.com.au/experiences/882431?_set_bev_on_new_domain=1634612225_ZGViZDI5MTY4ZDcz&modal=PHOTOS&modalItem=767209842), it grows up so spoilt that its manners are permanently lost through adulthood. To give the infant physical affection is effectively to abuse it.

This inadvertent abuse tends to be terminal for the pet because the results are too dangerous for humans. Individuals of the llama that have been cuddled as infants may have to be killed once adult. This is because they are inclined to inflict on humans not only spitting but also the real violence of kicking, biting and trampling.

Posted on October 17, 2021 22:32 by milewski milewski | 7 comments | Leave a comment

October 15, 2021

The dromedary as a humping mule

Everyone knows that mules are a vigorous hybrid between female horse (Equus caballus) and male donkey (Equus asinus), and that the dromedary (Camelus dromedarius, https://en.wikipedia.org/wiki/Dromedary#Relationship_with_humans) is the form of livestock most suited to drought. However, what many may not realise is how similar mules and the dromedary are in various ways.

The first, obvious, similarity is in body mass: both weigh preferably more than 400 kg when adult. This size, combined with hybrid vigour and the natural endurance derived from ancestors adapted to semi-arid conditions, makes both mules and the dromedary excellent beasts of burden.

A far less obvious similarity is that both are interspecific hybrids (see https://pastoralismjournal.springeropen.com/articles/10.1186/s13570-020-0159-3).

The first generation of hybrids between the dromedary and the bactrian camel (Camelus bactrianus) has only one hump but tends to be more vigorous than either parent.

And, as in the case of mules, the hybrids cannot practicably be bred among themselves to perpetuate this vigour. As everyone knows, mules are by definition infertile hybrids. For camels there is no such infertility but the hybrid vigour tends to be lost by the second generation anyway (https://iranicaonline.org/articles/camel-sotor#:~:text=The%20Iranians%20would%20thus%20have,it%20was%20probably%20not%20numerous.).

Because hybridisation between the two ancestral species of camels was practised from the start of the domestication of the dromedary, all populations of what is now classified as the dromedary probably contain genetic modifications from the bactrian camel. The most common sign of this may be long fur on the neck of the dromedary (https://www.inaturalist.org/observations/38474885), which belongs to the bactrian camel rather than the heat-tolerant wild ancestor restricted to Arabia.

Furthermore, as in mules, the hybridisation in camels is most effective with a particular species as the father.

It is best for males of large-bodied breeds of the donkey to be mated with females of the horse, because the mules thus produced are large-bodied. In the case of camels, it is best for males of the bactrian camel to be mated with females of the dromedary. This is because females copulate while lying on their bellies, and the rear hump of the bactrian camel tends to obstruct the mating squat of males of the dromedary.

Both mules and the dromedary are more difficult to breed than most domestic ungulates. And in both cases this is partly because of complications in mating, and partly because the reproductive process is slower than in true ruminants such as oxen (Bos spp.).

In both cases, mating needs to be supervised. The horse, even when in oestrus, finds the donkey so sexually unattractive that some artificial forcing is necessary. In the dromedary, breeding is inconveniently seasonal, rutting males can attack the mother's previous offspring, libido can be lacking, and successful copulation is needed to induce ovulation in the first place (https://www.sciencedirect.com/science/article/abs/pii/0378432087900492 and https://www.researchgate.net/publication/275250659_Male_camel_behavior_and_breeding_management_strategies_How_to_handle_a_camel_bull_during_the_breeding_season and http://www.veterinaryworld.org/Vol.2/February/Reproduction%20in%20Camel.pdf).

Equids have long gestation and a prolonged juvenile period, and this is even more limiting for the dromedary, which gestates for 13 months, first breeds at four years old, and can produce at most one offspring every two years (https://www.sciencedirect.com/science/article/pii/S1658077X20300709).

In compensation for the slow reproduction of equids and particularly camelids, mules and the dromedary are both surprisingly long-lived. The dromedary has a working life fourfold longer than that of the average ox (https://en.wikipedia.org/wiki/Ox), while carrying or pulling twice the load, locomoting more rapidly, working more frequently, and being able to forgo drinking for longer.

Both mules and the dromedary can be kept on food too poor for the horse or oxen. This is partly because the donkey is far better-adapted than the horse to eat fibrous, dead material, and partly because camelids have a digestive system less specialised, and thus less demanding and more versatile, than that of oxen and other true ruminants.

Whether mules or the dromedary were utilised by early civilisations was not necessarily dependent on climate. For example, in ancient Egypt and the Levant of the Old Testament it was mules that were prized for two thousand years, before their roles were largely usurped by the dromedary (https://www.mulemuseum.org/history-of-the-mule.html). It was only at this later stage that the latter species (or, strictly speaking, hybrid) was recruited from nearby Arabia for general service in farming, commerce and warfare in Egypt and the Levant.

Posted on October 15, 2021 21:03 by milewski milewski | 6 comments | Leave a comment

October 14, 2021

Why Eucalyptus erythrocorys tends to self-amputate in cultivation

Eucalyptus erythrocorys (https://apps.lucidcentral.org/euclid/text/entities/eucalyptus_erythrocorys.htm and https://twitter.com/eucalyptaus/status/1168440927628795904 and https://www.ecovoice.com.au/the-illyarrie-wins-eucalypt-of-the-year-2020/ and http://anpsa.org.au/e-ery.html and https://alchetron.com/Eucalyptus-erythrocorys) has large blooms: bright yellow and with exotic-looking red opercula (https://www.inaturalist.org/observations/70992084).

This makes for a cheerful -even spectacular - appearance as summer becomes autumn in the mediterranean-type climate.

So it is unsurprising that this species has become a horticultural favourite as a large shrub or small tree (https://www.bgpa.wa.gov.au/about-us/information/our-plants/plants-in-focus/eucalyptus-erythrocorys). It is planted in gardens and along streets in Australia (particularly in the west) and in the similar climate of southern California.

However, cultivating the species in this way (https://cals.arizona.edu/yuma/plant_index/eucalyptus_erythrocorys.htm and https://www.eranurseries.com.au/eucalyptus-erythrocorys) brings the practical disadvantage that the several boles of each individual plant tend to grow at angles, not upright.

As a result of this leaning tendency, top-heaviness often results in partial collapse. One of the boles suddenly breaks, felling that part of the crown and its growing foliage in what looks like spontaneous auto-amputation.

Now, everyone knows that various species of eucalypts, which grow naturally as large trees, have a disconcerting habit of suddenly dropping large branches (https://treesafe.com.au/blog/tree-removal/eucalyptus-trees-dangers/ and https://sydneytreeremovals.com.au/tree-facts/widow-maker-gum-trees-clear-deadwood/). It is understandable that tall trees would benefit from getting rid of redundant lower branches and dead sticks, but what is noteworthy about eucalypts is that the branches are usually shed with the foliage still growing.

The fact that various species of eucalypts spontaneously - and dangerously - jettison branches in a state of apparent vitality has led to the term 'self-pruning' (https://en.wikipedia.org/wiki/Cladoptosis).

Seen in this context, the proneness of cultivated E. erythrocorys to partial collapse seems incongruous. This is because, on this relatively small plant, such a large proportion of the stem system is 'shed' that the action resembles not self-pruning as much as an unsuccessful attempt at suicide.

Curious about this apparently maladaptive behaviour, I visited the plant in its natural habitat near the coast south of Dongara in southwestern Western Australia (https://apps.lucidcentral.org/euclid/text/entities/eucalyptus_erythrocorys.htm and https://en.wikipedia.org/wiki/Dongara,_Western_Australia and https://twitter.com/RichardMcLellan/status/1168669607059570689/photo/1). Here E. erythrocorys is locally dominant on ridges of coastal limestone, with a heathy understorey (see photo no. 12 in http://ianfrasertalkingnaturally.blogspot.com/2014/01/i-love-sunburnt-country.html).

What I noticed immediately is that, in its natural state, E. erythrocorys is more like a mallee (https://en.wikipedia.org/wiki/Mallee_(habit)) than it appears to be in the suburbs or in photos singling out the more statuesque specimens in the wild (e.g. https://www.inaturalist.org/observations/42711339). In nature, each individual usually has more than six stems emerging at ground-level even if the lignotuber, so typical of mallees, is not particularly well-developed.

This brought me to the realization that the growth-form encouraged in cultivation is different from the wild, multi-stemmed one. Gardeners, ignorant of the natural shape of the plant, understandably tend to cull the stems to a few which resemble boles of a (small) tree.

Closer examination distinguished E. erythrocorys from all the other species of mallees with which I am familiar in the wild. The stems, although initially growing upwards as expected, sprawl down to the become prostrate in their distal sections. The result is a growth-form similar to mallee but with much of the outer foliage trailing along the ground.

Why does E. erythrocorys differ from other multi-stemmed, wildfire-tolerant eucalypts in having this oddly recurved growth-form?

One possible reason is its tenuous relationship with fire in a type of vegetation which is not easily classified as either typical mallee (https://www.anbg.gov.au/photo/vegetation/mallee-woodlands-shrublands.html) or typical kwongan (https://en.wikipedia.org/wiki/Kwongan).

Most species of mallee are not only tolerant of wildfire, but intimately adapted to a regime of periodic combustion in which all their stems die by scorching, and growth resumes from ground level. Usually the vegetation is dense enough that the flames engulf all including the crowns of the mallees. However, eucalypts tend to exclude flammable shrubs from the patch directly under the crown, which means that, if the stand is sparse, there is a chance that the fire will fail to ignite the foliage of the upper storey, simply burning through the heathy understorey and leaving the eucalypts partly unburnt.

In the case of E. erythrocorys, the vegetation is indeed relatively sparse, partly because the surface is so stony. The heathy understorey looks barely dense enough to carry the flames across the empty patches under the mallees.

What E. erythrocorys seems to arrange, by having its outermost foliage trailing back down to the ground, is a ladder whereby the flames can climb up into the crown. This would ensure the desired combustion of the foliage, which as in other mallees rejuvenates the plant and self-fertilises it with its own ash.

The problem in cultivation is that no gardener or arborist, private or municipal, wants an untidy sprawl-mallee. So the natural shape of the plant is modified in the sapling. However, this cannot correct the leaning which is 'hardwired' in the remaining few boles. This inclination of the foliage towards the ground, now made dysfunctional, results sooner or later in partial collapse.

In summary, my finding is that the auto-amputation of the stem-system of E. erythrocorys is not a case of the sort of self-pruning so well-known in tree eucalypts. Instead it is a result of artificial distortion of the natural shape of the plant.

Horticulturally desirable though this species is, its natural adaptations are such that growing it as a tree is unlikely to be achieved without selective breeding.

Posted on October 14, 2021 22:25 by milewski milewski | 1 comment | Leave a comment

October 13, 2021

Bird-beak hakea epitomises plants dedicated to combustion

Bird-beak hakea (Hakea orthorrhyncha, http://anpsa.org.au/h-ort.html and https://en.wikipedia.org/wiki/Hakea_orthorrhyncha and https://florabase.dpaw.wa.gov.au/browse/profile/2192 and https://www.bgpa.wa.gov.au/about-us/conservation/plant-of-the-month/2001-july-2015) has the 'perfect resume' as an example of adaptation to an ecological syndrome which is seen at its most extreme in Western Australia.

It is one of those plants that 'says it all' in its combination of the various adaptive features of organisms to a particular regime in the natural environment.

Australia - and particularly Western Australia - has the poorest soils in the world: extensive deep sands exhausted of most nutrients by eons of weathering and leaching on a flat landscape.

On such soils, plants are not worth eating, which means that they tend to be consumed and recycled by combustion instead of digestion.

Plants well-suited to such environments, with their periodic wildfires, include multi-stemmed shrubs. They have foliage which is flammable even when green, and the means to regenerate new foliage rapidly from the ashes.

In the case of bird-beak hakea this means a woody burl just below ground-level, which survives even if all the stems of the plant are killed by the heat. This lignotuber (https://en.wikipedia.org/wiki/Lignotuber) produces new shoots without having to start again from seed.

And a crucial point to understand about plants is that - if appropriately adapted and living in sunny climates - they can make plenty of carbohydrate even on poor soils. This is partly because the enzymes of photosynthesis depend on metals, particularly magnesium and iron, which remain sufficient even where the core nutrients (particularly phosphorus and zinc) have become vanishingly scarce.

Carbohydrate is what sugar, plant fibre and wood are made of, depending on the degree of polymerisation. Because carbohydrate is the one product that nutrient-poor plants are affluent in, they use it in various ways to offset all the other disadvantages in their environments.

This is why bird-beak hakea has recruited birds to transport its pollen. Instead of settling for bees, it has the nectar to attract far larger, more energetic pollinators. Red is a hue invisible to bees but conspicuous to birds (https://apps.des.qld.gov.au/species-search/details/?id=1482#!lightbox-uid-0), and it signifies a font of sugar as well as hinting at the flames that propagate the plant in the longer term.

So bird-beak hakea is both 'pyrophilic' (loving fire) and 'ornithophilic' (loving honeyaters https://en.wikipedia.org/wiki/Honeyeater and other pollinating birds).

Bird-beak hakea uses its carbohydrates to fortify its leaves with lignin, making them stiff, spinescent and nearly as flammable as cardboard. And it also converts its roots into a dense, cardboard-like mat, protected from fire by being just below the sand (see https://en.wikipedia.org/wiki/Cluster_root). This mat absorbs, before they are lost, any nutrients that land in the form of dust and ash, thus providing the means for regrowth.

Furthermore, this species uses its carbohydrates in a remarkable way to protect its seeds. The seed-capsule is fortified into a lump of wood, 2 cm by 4 cm, which remains sealed and alive for years until the next fire arrives.

This makes bird-beak hakea both 'bradysporous' (storing the seed on the plant instead of in the ground, https://en.wikipedia.org/wiki/Bradyspory) and woody-fruited (protecting the seed from parrots and other seed-eating animals).

Various flammable plants on other continents show one or two of the above features, but none beyond Australia combines them all in one species. This is largely because nutrient-poverty is not as extensive and extreme, and wildfire does not replace herbivory as thoroughly, on other continents.

For example, in the Mediterranean Basin there are several types of shrub which possess lignotubers (https://www.researchgate.net/publication/229476710_Resprouting_of_the_Mediterranean-type_shrub_Erica_australis_with_modified_lignotuber_content and https://en.wikipedia.org/wiki/Erica_Australis and https://jgpausas.blogs.uv.es/?s=Phillyrea). Others have evergreen, spinescent leaves (https://en.wikipedia.org/wiki/Juniper). But none of these plants is ornithophilous or bradysporous, and all lack cluster roots.

In South Africa there are proteas, belonging to the same family as bird-beak hakea, that have lignotubers, cluster roots, bird-pollinated flowers, and even bradyspory (e.g. https://en.wikipedia.org/wiki/Protea_cynaroides). But they lack leaf-spinescence and woody fruits.

In North America there are 'closed-cone pines (see https://en.wikipedia.org/wiki/Pinus_serotina and https://en.wikipedia.org/wiki/Pinus_contorta) with what amount to woody fruits. However, these lack all the other features of the syndrome, including a shrubby growth-form.

Plants such as bird-beak hakea (http://www.northqueenslandplants.com/Australian%20Plant%20Families%20N-S/Proteaceae/Hakea/Hakea%20orthorrhyncha%20.html and https://domusnursery.com.au/plants/plant.cshtml?plant_code=hakort and https://www.australianseed.com/shop/item/hakea-orthorrhyncha and https://mucheatreefarm.com.au/product/hakea-orthorrhyncha/ and https://davesgarden.com/guides/pf/showimage/413766/#b and https://triggplants.com.au/product/hakea-orthorrhyncha-in-50mm-forestry-tube/ and http://www.consultaplantas.com/index.php/en/plants-from-d-to-l/2218-hakea-orthorrhyncha-or-bird-beak-hakea-care-and-growing) nowhere dominate the vegetation, even on the coastal sandplains of southwestern Australia (https://www.alamy.com/biodiversity-of-flora-in-heath-kwongan-habitat-wheatbelt-frank-hann-national-park-november-2013-image342310831.html).

But the fact that any such species exists is testimony to the ecological peculiarity of Australia among the continents. In its own way, bird-beak hakea is as odd, by global standards, as the kangaroos which exert a minimal effect in its habitat (https://www.rswa.org.au/publications/Journal/80(2)/80(2)wann.pdf).

Posted on October 13, 2021 20:36 by milewski milewski | 4 comments | Leave a comment

October 10, 2021

Diet of the feral camel in Australia, part 2

The most recent wild ancestor of the dromedary (Camelus dromedarius) lived in what is now Dubai (https://www.pnas.org/content/113/24/6707 and https://www.pnas.org/content/pnas/suppl/2016/05/04/1519508113.DCSupplemental/pnas.1519508113.sapp.pdf) on a remote coastal plain which is hard to relate to the directions of the compass but forms a 'horn' of the Arabian subcontinent in the same way that the Horn of Africa relates to the African continent.

Given this origin, it might be informative to refer the favourite food-plants of the dromedary, in its feral state, in Australia to the flora of Arabia. In particular, which of the genera preferred in Australia are also indigenous to Arabia, albeit as different species?

A principle to bear in mind is that, in general, the leaves and shoots of stem-spinescent or hedge-forming plants are more palatable and nutritious than those of plants lacking these structural defences. Leaf-spinescent plants (other than thistles, https://www.farmonline.com.au/story/4243900/scotch-thistles-secret-enemy/#:~:text=%E2%80%9CThey%20love%20Scotch%20thistle%20in,and%20camels%20are%20the%20answer. and https://www.armstrongorganics.com/camels) tend to follow the opposite trend. Their foliage tends to be nutrient-poor, epitomised by the distinctively Australian hummock grasses (Triodia, see https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1469-185X.2007.00017.x).

In comparing Australia with Arabia, we can start with the amaranths and other halophytes (https://en.wikipedia.org/wiki/Halophyte).

Atriplex, a cosmopolitan genus of sodic-adapted shrubs and herbaceous plants, is locally conspicuous in semi-arid Australia (https://www.daf.qld.gov.au/business-priorities/agriculture/plants/crops-pastures/pastures/saltbush#:~:text=Saltbushes%20are%20members%20of%20a,staple%20diet%20of%20many%20animals.), and inconspicuous in Arabia (https://www.cabi.org/ISC/abstract/20013152218).

Wherever it occurs, Atriplex is a fairly nutritious plant for herbivores (http://researchhub.buan.ac.bw/bitstream/handle/123456789/284/ and https://www.tandfonline.com/doi/abs/10.2989/10220110309485822). However, its food-value tends to be limited because its concentraction of sodium is not necessarily matched by other useful elements.

Probably more important in the diet of the dromedary in Arabia is the related genus Caroxylon, which does not occur in Australia and is associated with nutrient-rich soils rather than merely sodic ones. The branching stems and diminutive leaves (e.g. see https://en.wikipedia.org/wiki/Salsola_vermiculata and https://en.wikipedia.org/wiki/Salsola_imbricata) provide antiherbivore defences lacking in Atriplex and most of the other amaranths in Australia. This suggests that Caroxylon is more palatable than Atriplex to the dromedary.

One way to view the various halophytic amaranths (Atriplex, Chenopodium, Enchylaena, Maireana, Sclerolaena, Tecticornia) eaten by the feral dromedary in Australia is as nutrient-poor counterparts - which were relatively exempt from herbivory in Australia before the arrival of domestic livestock - to Caroxylon.

The amaranth Ptilotus (https://en.wikipedia.org/wiki/Ptilotus) is non-halophytic but conforms to this pattern in being common but not nutritious enough to be under pressure from herbivores. This is true notwithstanding the phosphorus-richness of certain species of Ptilotus (https://www.publish.csiro.au/bt/BT19188).

Zygophyllaceae are unrelated to amaranths phylogenetically, but show a similar relationship to sodicity and herbivory. Although Zygophyllum occurs in Arabia and in Australia, the closely related genus Tetraena - absent from Australia - has a growth-form convergent with Caroxylon in its adaptation for intense herbivory (https://en.wikipedia.org/wiki/Tetraena_alba and https://en.wikipedia.org/wiki/Tetraena_qatarensis).

The zygophylls also contain Tribulus, which is not halophytic. This is a favourite food of the dromedary (https://arkbiodiv.com/2019/05/05/camels-flower-%D8%B2%D9%87%D8%B1-tribulus-is-the-precious-flora-of-the-arabian-desert/) and indigenous to both Australia and Arabia, although the commonest species has probably been introduced anthropogenically (https://en.wikipedia.org/wiki/Tribulus).

Portulaca is yet another genus indigenous to both Australia and Arabia, and likely to be a favourite food-plant of the dromedary in both regions.

Acacias occur in both Australia and Arabia, but in the form of different genera. Whereas the species eaten by the feral dromedary in Australia belong to the genus Acacia and have phyllodes instead of leaves, those likely to have been eaten in Arabia belong to the genus Vachellia, have bipinnately compound leaves, and are extremely spinescent (https://en.wikipedia.org/wiki/Vachellia_tortilis and https://en.wikipedia.org/wiki/Vachellia_flava).

Carissa and Capparis nowhere dominate the vegetation, but exemplify preferred species shared between Australia and Arabia. Not only is the dromedary likely to eat these plants (which are variably spinescent depending on pressure from herbivory) in both regions, but the same species is indigenous in both cases (https://en.wikipedia.org/wiki/Carissa_spinarum and https://en.wikipedia.org/wiki/Caper).

The feral dromedary in Australia coexists in places with kangaroos. However, there is little competition for food, for several reasons.

Firstly, all species of kangaroos prefer grasses, which are generally not preferred by the feral dromedary. Secondly, kangaroos do not generally eat acacias, eucalypts or eremophilas. Thirdly, the dromedary can reach twice - and perhaps threefold (https://www.naturepl.com/stock-photo-bactrian-camel-camelus-bactrianus--three-beneath-tree-one-standing-on-nature-image01643198.html) - as high as kangaroos can. And fourthly, much of the range of the feral dromedary is in the Australian Empty Quarter, where all kangaroos were scarce at the time of European arrival and remain scarce today.

It is noteworthy that the feral camel accepts eucalypts and proteas to a greater extent than hummock grasses.

I can summarise as follows.

Although the vegetation differs greatly between semi-arid Australia and Arabia, the dromedary is mobile and versatile enough to find equivalent, and in many cases closely related, plants to eat in both regions. Among comparable genera of favourite food plants, Australian species tend to be less spinescent or hedged than Arabian species, which may allow the dromedary to forage more efficiently - but not necessarily more sustainably - in its adopted than in its original habitat.

Posted on October 10, 2021 22:44 by milewski milewski | 9 comments | Leave a comment

Diet of the feral camel in Australia, part 1

Camelus dromedarius (https://en.wikipedia.org/wiki/Dromedary) is unusual among the feral animals in Australia.

Firstly, among all the domestic species of mammals, the dromedary is least closely associated with any known wild ancestor - despite domestication having occurred as recently as four thousand years ago.

Secondly, this is the only feral ungulate successful in the extensive nutrient-desert that I have called the Australian Empty Quarter (see my last Post and https://www.researchgate.net/figure/Map-of-project-study-area-showing-the-camel-distribution-boundary-major-desert-features_fig1_255687533).

Thirdly, the dromedary has such slow metabolism, growth and reproduction, relative to most other artiodactyls, that it seems somewhat convergent with extinct large marsupials (e.g. https://en.wikipedia.org/wiki/Palorchestes) of the Pleistocene in Australia (none of which is known to have occurred in the Australian Empty Quarter).

Given how odd the dromedary is for a domestic herbivore - resembling a wild animal 'pre-adapted' for the Australian semi-arid zone - its diet in its adopted habitat (https://dpir.nt.gov.au/__data/assets/pdf_file/0004/233455/tn116.pdf and https://www.dreamstime.com/stock-photo-australian-camels-outback-pair-wild-dromedary-graze-image34710910 and https://www.alamy.com/dromedary-camels-two-grazing-camelus-dromedarius-feral-animals-living-wild-introduced-to-australia-now-widespread-in-wild-image181672328.html) is of obvious interest.

What can we say about the ecological nature of those genera and species of plants most preferred by the dromedary in its feral state in Australia?

The overall finding is hardly surprising. The preferred plants tend to belong to:

  • cosmopolitan genera and weedy species
  • nutritional categories which boost palatability (e.g. nutrient-parasitism and symbiotic nitrogen-fixation)
  • genera and species restricted to the patches of relatively nutrient-rich soils (by Australian standards), and
  • regeneration after wildfires.

The plant species preferred by the dromedary in Australia are generally not the dominant/commonest ones, and this is particularly so in the Australian Empty Quarter. Instead, they tend to belong to families such as the Amaranthaceae, possessing soft foliage and growing on the least acidic soils or as temporary flushes dependent on ash.

Favourite food-plants of the feral dromedary, in the category of symbiotic nitrogen-fixers, belong to the Mimosaceae and Fabaceae.

In the former family are Acacia oswaldii (https://en.wikipedia.org/wiki/Acacia_oswaldii and http://worldwidewattle.com/speciesgallery/oswaldii.php) and several other species in the same genus, some of which are spinescent (http://worldwidewattle.com/speciesgallery/descriptions/pilbara/html/victoriae.htm and http://worldwidewattle.com/speciesgallery/descriptions/pilbara/html/tetragonophylla.htm)

In the latter family are Erythrina (https://en.wikipedia.org/wiki/Erythrina_vespertilio), Crotalaria, Indigofera, Rhynchosia, and Swainsona (https://en.wikipedia.org/wiki/Swainsona)

Favourite food-plants in the category of parasites (including both mistletoes and free-standing shrubs which parasitise the roots of other plants) are Amyema, Anthobolus, Cassytha, Cuscuta, Lysiana (https://en.wikipedia.org/wiki/Lysiana_exocarpi) and Santalum spp. (https://en.wikipedia.org/wiki/Santalum).

Other favourite food-plants tend to belong to genera occurring naturally on several continents, some of which can be called cosmopolitan.

These are (in alphabetical order):

Kali (https://en.wikipedia.org/wiki/Kali_(plant))

The following genera are restricted to Australia but associated with sodic soils: Enchylaena, Lawrencia, Maireana, Sclerolaena and Tecticornia.

This brings us to what are perhaps the most interesting of the favourite food-plants, i.e. those belonging to typically Australian families/genera.

These are (in no particular order) as follows:

Eucalyptus gammophylla (https://en.wikipedia.org/wiki/Eucalyptus_gamophylla)
Grevillea juncifolia (https://en.wikipedia.org/wiki/Grevillea_juncifolia) and G. eriostachya (https://en.wikipedia.org/wiki/Grevillea_eriostachya)
Codonocarpus cotinifolius (https://en.wikipedia.org/wiki/Codonocarpus_cotinifolius)
Eremophila longifolia (https://en.wikipedia.org/wiki/Eremophila_longifolia and http://anpsa.org.au/APOL15/sep99-2.html)
Brachychiton gregorii (https://en.wikipedia.org/wiki/Brachychiton_gregorii)
Lechenaultia divaricata (https://en.wikipedia.org/wiki/Lechenaultia)
Ptilotus spp. (https://en.wikipedia.org/wiki/Ptilotus_macrocephalus and https://en.wikipedia.org/wiki/Ptilotus_polystachyus)
Calotis hispidula (https://en.wikipedia.org/wiki/Calotis_hispidula)
Rhodanthe floribunda (https://en.wikipedia.org/wiki/Rhodanthe_floribunda)
Scaevola parvifolia (https://en.wikipedia.org/wiki/Scaevola_parvifolia)
Stylobasium spathulatum (https://en.wikipedia.org/wiki/Stylobasium_spathulatum).

Atalaya hemiglauca (https://en.wikipedia.org/wiki/Atalaya_hemiglauca) belongs to a mainly Australian genus with one species in southern Africa.

What does the vegetation look like when/where the favourite food-plants of the feral dromedary are so common that they dominate the scene? Here are some glimpses.

Regeneration after wildfire: https://keys.lucidcentral.org/keys/v3/scotia/key/Plants%20and%20Fungi%20of%20south%20western%20NSW/Media/Html/Codonocarpus_cotinifolius.htm

Prominence of phyllodinous acacias: https://www.malleeconservation.com.au/blog/acacia-oswaldii

Prominence of 'saltbush' and other amaranths adapted to sodic soils: https://www.nationalparks.nsw.gov.au/plants-and-animals/saltbush.

to be continued...

Posted on October 10, 2021 08:45 by milewski milewski | 2 comments | Leave a comment

October 09, 2021

The Australian Empty Quarter: epitome of a nutrient-desert

Everyone knows that Australia is the driest continent. However, how many know that 'desert' in Australia refers less to a lack of water than to a lack of nutrients?

On most maps of land use in Australia, a large-scale pattern is obvious but does not seem to have been pointed out as such. This is a broad vertical band across the western half of the continent, centred just west of the border between Western Australia (https://en.wikipedia.org/wiki/Western_Australia#/media/File:Western_Australia_in_Australia.svg) and South Australia/Northern Territory. The climate varies from tropical in the north to temperate in the south.

In this broad band there is, to this day, negligible farming or other utilisation of the land (see https://www.agriculture.gov.au/abares/aclump and https://www.veganaustralia.org.au/impact_of_a_vegan_agricultural_system_on_land_use and https://www.researchgate.net/figure/A-2000-01-national-scale-land-use-map-illustrating-the-broad-distribution-of-pastures_fig1_230817486 and https://www.moffittsfarm.com.au/2014/01/04/land-use-australia-2005-2006-source-abares/ and https://ars.els-cdn.com/content/image/1-s2.0-S0959378016300231-gr1.jpg and https://www.researchgate.net/figure/Sample-locations-and-land-use-types-in-Australia-The-agricultural-areas-of-Australia-are_fig1_288059143 and https://www.researchgate.net/figure/a-Carnahan-classification-of-current-vegetation-for-Australia-AUSLIG-1990-and-b_fig1_236770005 and https://www.creativespirits.info/aboriginalculture/land/aboriginal-homelands-outstations).

This feature needs a name, and I suggest we call it the Australian Empty Quarter.

What is most surprising about the Australian Empty Quarter is how densely-vegetated it is with evergreen perennial plants (https://diamantina-tour.rezdy.com/95387/great-victoria-desert-nullarbor-expedition?lang=ja and https://www.worldatlas.com/articles/where-does-the-great-victoria-desert-lie.html and https://www.abc.net.au/science/photos/2012/11/21/3636626.htm?xml=3636626.mediarss.xml#bigpicturepos and https://www.istockphoto.com/photo/marble-gum-gm532574825-55893698 and https://upload.wikimedia.org/wikipedia/commons/8/81/Eucalyptus_gongylocarpa.jpg and https://www.exploroz.com/wildflowers/395+marble-gum and https://www.alamy.com/stock-photo-camel-crossing-the-great-victoria-desert-western-australia-97792062.html).

The driest part of Australia, which has sparse vegetation, occurs far to the east and is a different geographical feature (http://www.truganinaweather.com/weather-education/australian-climate-maps.htm and https://en.wikipedia.org/wiki/Lake_Eyre_basin).

The Australian Empty Quarter, despite looking far more luxuriant than the conventional image of desert, is even poorer in large animals than the rest of the continent. The emu (Dromaius novaehollandiae, https://upload.wikimedia.org/wikipedia/commons/f/ff/Emu_distribution.png and https://upload.wikimedia.org/wikipedia/commons/8/8b/Dromaius_novaehollandiae_map_distribution_2.svg) and kangaroos (mainly Osphranter rufus, http://www.ecoclimax.com/2017/05/kangaroo-distribution-in-australia-vs.html and https://www.echidnawalkabout.com.au/macropods-kangaroos-of-australia/ and https://bio1152.nicerweb.com/Locked/media/ch52/kangaroo.html) are largely absent.

Various other species of animals show a similar gap in their distributions (https://www.researchgate.net/figure/Magpie-plumage-variants-and-their-distribution-across-the-Australian-continent_fig1_232248336 and https://edition.cnn.com/2019/09/15/australia/australia-magpie-death-intl-hnk-scli/index.html).

The most significant plants in the Australian Empty Quarter are hummock grasses belonging to the genus Triodia (https://en.wikipedia.org/wiki/Triodia_(plant)). These are adapted to nutrient-poverty and fire to the degree that they have minimal value for herbivores (https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1469-185X.2007.00017.x). Their leaves are woody, resinous and unpalatable.

The ultimate environmental reason for the Australian Empty Quarter is a combination of extreme flatness and underlying bedrock of nutrient-poor sediments such as sandstone. This land has been geologically stable since the time of dinosaurs, so that the soils, sandy and poor to start with, have become profoundly depleted of phosphorus and zinc in particular.

This limits herbivory so much that vegetation is left to grow until wildfire returns, and combustion has replaced digestion as the most important recycler of nutrients.

The Australian Empty Quarter is best understood as a nutrient-desert rather than a rainfall-desert because, even if it were well-watered, it would remain largely devoid of large animals. Although this zone is semi-arid, it is ecologically aligned with the African Empty Quarter (see my Post of July 18, 2021) rather than the conventional concept of a desert.

As an example of a nutrient-desert, the Australian Empty Quarter is far more extreme than the Kalahari-derived sand-sheet, covered with miombo woodland (https://en.wikipedia.org/wiki/Miombo), in Angola - in which the incidence of large animals is minimal by African standards but categorically greater than in any part of Australia.

One of the principles illustrated is this:

There are some climates just too dry for the vegetation to maintain cover over the land, and this is the conventional concept of desert. However, no soils on this Earth are so nutrient-poor that woody plants cannot grow on them, albeit slowly. Thus arises the combination we see in the Australian Empty Quarter: a vegetated plain effectively useless to man and beast.

Except, that is, for a camel...

Posted on October 09, 2021 06:08 by milewski milewski | 4 comments | Leave a comment