26 de noviembre de 2021

Balanites vs vachellia

Ingresado el 26 de noviembre de 2021 por milewski milewski | 0 comentarios | Deja un comentario

Five remarkable photos of giraffes

(writing in progress)

The following initially drew my attention because it shows the pedal flag in Giraffa tippelskirchi. Then I noticed the mother plus three juvenile individuals of the cheetah (Acinonyx jubatus) in the foreground, their spotted coats blending in so well that they virtually hide in plain sight. This photo nicely illustrates the analogy between giraffes and big cats in camouflage colouration, and the exceptional body size of giraffes as camouflaged megafauna. It also illustrates the phenomenon of flagging in otherwise inconspicuous animals. The pedal flag of this species of giraffe is easy enough to spot once one has a search-image, but note that the cheetah too has a flag: the white-and-black tail-tip (a caudal flag) visible on one individual.

The individuals of G. tippelskirchi are all males, ranging from juvenile to adult, which can be told by not only their genitalia but also the size and form of their horns.

Body mass is about 45 kg for the adult female cheetah and about 500-1000 kg for these individuals of G. tippelskirchi.

https://www.istockphoto.com/photo/giraffes-looking-at-cheetahs-gm532700725-56175692

https://www.istockphoto.com/photo/masai-giraffe-gm1257170721-368333347

https://www.istockphoto.com/photo/masai-giraffe-giraffa-camelopardalis-tippelskirchi-masai-mara-park-in-kenya-gm1262783396-369525685 and https://www.istockphoto.com/photo/masai-giraffes-fighting-gm1191233110-337981747 and https://www.istockphoto.com/photo/masai-giraffes-fighting-gm1191233151-337981921

https://www.istockphoto.com/photo/masai-girafffe-giraffa-camelopardalis-tippelskirchi-drinking-masai-mara-park-in-kenya-gm1256988943-368223297

https://www.naturepl.com/stock-photo-eland-tragolaphus-oryx--females-and-giraffe-giraffa-camelopardalis-nature-image01668932.html

https://www.gettyimages.ie/detail/photo/highland-eland-grazing-along-with-giraffe-in-the-royalty-free-image/1127579168?adppopup=true

https://depositphotos.com/249627558/stock-photo-vertical-photo-huge-eland-antelope.html

https://www.istockphoto.com/photo/giraffes-in-desert-habitat-gm873114432-243844351

https://www.istockphoto.com/photo/giraffe-walking-on-the-plains-of-the-masai-mara-national-park-gm1277799866-376914862

https://www.istockphoto.com/photo/wildlife-in-africa-gm180445872-25087728

(writing in progress)

Ingresado el 26 de noviembre de 2021 por milewski milewski | 6 comentarios | Deja un comentario

25 de noviembre de 2021

The mystery of megafaunal microcamouflage

Everyone knows that giraffes and big cats are spotted, and zebras are striped.

And most would agree that these patterns function as camouflage in at least a loose sense.

However, how many have noticed that the disruptive markings in giraffes include spotting/striping too small-scale to make sense as camouflage?

The dark blotches/spots on the pelage of giraffes range in diameter from tens of centimetres to mere millimetres, despite the likelihood that both sizes will be viewed from similar distances by potential predators (https://www.istockphoto.com/photo/masai-giraffe-gm900610478-248476170 and https://www.istockphoto.com/photo/baby-masai-giraffe-stands-near-thorn-trees-gm1163986460-319800417).

Under which circumstances could it possibly be true that the tiny spots - which are visible only at close range - on the forehead, temples and/or crown help giraffes to hide?

Forehead of adult female Giraffa tippelskirchi:
https://www.istockphoto.com/photo/giraffe-in-kennya-on-safari-africa-gm1354464097-429280909
https://www.istockphoto.com/photo/giraffe-in-kennya-on-safari-africa-gm1354465295-429280938
https://www.agefotostock.com/age/en/details-photo/africa-african-animal-background-beautiful-big-brindled-brown-camouflage-close-up-culture-cute-ear-face-fun-funny-giraffa-giraffe-head/ZON-8453742
https://www.istockphoto.com/photo/curious-giraffe-portrait-on-the-savannah-gm1128231346-297651521
https://pixels.com/featured/close-up-of-a-maasai-giraffes-eyes-panoramic-images.html
https://www.shutterstock.com/nb/image-photo/wild-giraffe-close-head-shot-chewing-2037362243

Temples and crown of mature male Giraffa tippelskirchi:
https://www.istockphoto.com/photo/masai-giraffe-gm1310309401-399758914

Temples of adolescent male Giraffa tippelskirchi:
https://www.istockphoto.com/photo/masai-giraffe-gm467510293-34473716

Temples and crown of infant Giraffa tippelskirchi:
https://www.agefotostock.com/age/en/details-photo/close-up-of-a-masai-giraffe-giraffa-camelopardalis-tippelskirchi-also-known-as-the-maasai-giraffe-or-kilimanjaro-giraffe/X5T-2549599

Temples and crown of mature male Giraffa camelopardalis:
https://www.istockphoto.com/photo/giraffe-eating-grass-giraffe-head-green-trees-in-the-background-gm1339433342-419773508

Forehead of mature female Giraffa camelopardalis:
https://www.istockphoto.com/photo/contented-giraffe-gm115789869-4253424

Forehead and temples of Giraffa reticulata:
https://www.istockphoto.com/photo/a-reticulated-giraffe-gm805665456-130614787

In zebras, the striping on the forehead and temples is smaller-scale than that on the neck. However, the disparity is not as great and the fine-grained pattern is not as anatomically localised as in giraffes:
https://www.worldanimalfoundation.org/animal_encyclopedia/params/category/173341/item/994138/#gallery
https://www.alamy.com/stock-photo-close-up-side-view-of-zebra-face-147513723.html
https://www.alamy.com/african-animal-lion-zebra-wildebeest-elephant-calves-giraffe-birds-stars-sunset-sunrise-image241375085.html
https://www.alamy.com/african-animal-lion-zebra-wildebeest-elephant-calves-giraffe-birds-stars-sunset-sunrise-image241395544.html

In big cats there is no particular disparity, because the spots are all of the same order of magnitude:

Panthera onca:
https://image.shutterstock.com/shutterstock/photos/53686768/display_1500/stock-photo-close-up-portrait-of-jaguar-panthera-onca-53686768.jpg
https://www.jacadatravel.com/wp-content/uploads/2016/08/pantanal-jaguar-1024x576.jpg

Panthera pardus:
https://pxhere.com/en/photo/617310
https://s2.best-wallpaper.net/wallpaper/1280x1024/1209/Leopard-face-HD-close-up_1280x1024.jpgi

Panthera uncia:
https://i.ebayimg.com/images/i/400990455879-0-1/s-l1000.jpg
https://images.freeimages.com/images/large-previews/da0/close-up-of-snow-leopard-1243841.jpg

Panthera tigris:
https://www.australiazoo.com.au/wildlife/our-animals/sumatran-tiger/
https://image.freepik.com/free-photo/close-up-tiger-s-face_58995-594.jpg
https://thumbs.dreamstime.com/z/close-up-tiger-s-face-25875004.jpg

One possible explanation is that the micro-spotting on the heads of giraffes functions not for camouflage but for individual recognition. This is not necessarily undermined by the fact that most individuals lack spotting on the forehead (https://www.istockphoto.com/photo/giraffe-at-tarangire-national-park-tanzania-africa-gm619525138-108056915 and https://www.istockphoto.com/photo/giraffe-mikumi-national-park-tanzania-gm1177849689-328971616), temples and crown.

This explanation would be in line with the general tendency for antelopes to be most individually variable in their colouration on the face, particularly the forehead (e.g. https://kith.co/blog/fear-in-crisis/). However, it is undermined by the observations that gregariousness in giraffes tends to be promiscuous, bonds among individuals seem to be weak, and the form of the horns and horn-tufts would seem sufficient for individual recognition.

Ingresado el 25 de noviembre de 2021 por milewski milewski | 1 comentario | Deja un comentario

22 de noviembre de 2021

Precociality of the mane as a peculiarity of giraffids

Giraffids look odd compared to deer and bovids, with their long necks, long tongues, skin-covered horns, and extreme colouration (https://www.dreamstime.com/royalty-free-stock-images-giraffe-butt-image14173949 and https://es.123rf.com/photo_97882739_okapi-close-up-detail.html). However, an unremarked oddness of giraffids is the precociality of their manes.

Manes occur on the nuchal region (i.e. the dorsal surface of the neck) in various mammals including Carnivora (http://diversityofanimalsandplants.weebly.com/maned-wolf.html), suids (https://safarihuntingafrica.com/project/warthog/), tapirs (https://www.stockfreeimages.com/10352184/Funny-tapir.html), equids (https://es.123rf.com/photo_16460957_zebra-mane-close-up.html), and various ruminants (https://www.greatbigcanvas.com/view/male-black-wildebeest-calling-mountain-zebra-national-park-south-africa,2403179/).

Various adaptive functions of manes remain to be studied, but an obvious one is to exaggerate body size, particularly in masculine display. Those ruminants in which both sexes have horns also tend to have nuchal manes, consistent with an antagonistic theme.

In the few ungulates in which hornless/antlerless females possess manes, these are raised in defensive anger (https://www.alamy.com/stock-photo-cow-moose-defends-her-newly-born-calf-from-the-grant-creek-wolf-pack-75290283.html), again consistent with a theme of antagonistic exaggeration of body size.

These patterns do not apply to giraffes, in which the nuchal mane is proportionately largest at birth, smaller in adult females, and smallest in mature males.

Let us examine Giraffa giraffa giraffa for example:

infants:
https://es.123rf.com/photo_85501756_a-very-young-baby-southern-south-african-giraffe.html
https://es.123rf.com/photo_85501759_a-very-young-baby-southern-south-african-giraffe.html
https://www.robertharding.com/preview/764-6139/baby-cape-giraffe-giraffa-camelopardalis-giraffa-kruger-national/

adult females:
http://www.africanreferencephotos.com/photo/3952/Giraffe-Female-in-Profile.html

juvenile males:
https://www.istockphoto.com/photo/young-male-giraffe-walking-savute-chobe-np-botswana-gm176053405-10245077

mature males:
https://www.alamy.com/stock-photo-cape-giraffe-adult-kruger-nationalpark-south-africa-africa-giraffa-98140864.html
https://www.independent.co.uk/news/world/africa/giraffe-headbutt-death-carlos-carvalho-filmmaker-south-africa-glen-afric-broederstroom-a8339616.html

Turning to Giraffa tippelskirchi tippelskirchi, the following shows the differences between adult females and infants. Note that the mane becomes proportionately smaller with age but the occipital horn-tufts (see https://www.inaturalist.org/journal/milewski/59906-occipital-horn-tufts-a-previously-overlooked-feature-of-certain-giraffes#) are proportionately smaller in infant than in adult: https://www.istockphoto.com/photo/giraffe-mother-and-calf-serengeti-national-park-tanzania-africa-gm618728448-107737387?utm_source=unsplash&utm_medium=affiliate&utm_campaign=srp_photos_top&utm_content=https%3A%2F%2Funsplash.com%2Fs%2Fphotos%2Fbaby-giraffe&utm_term=baby%20giraffe%3A%3A%3A.

Two other tracts of dorsal pelage are also proportionately largest at birth in giraffes.

The first is the main horn-tufts. The following show that, for example in Giraffa tippelskirchi, the main horn-tufts are proportionately larger in infants than in adult females:
https://www.dreamstime.com/stock-illustration-female-giraffe-baby-savannah-kenya-tanzania-east-africa-excellent-illustration-image78918560 and https://www.dreamstime.com/stock-photography-baby-giraffe-image17651562 and https://www.dreamstime.com/stock-photo-adorable-baby-giraffe-looking-silly-tufts-surrounded-foliage-kenya-s-masai-mara-image80848245).

The second is a caudal mane. Giraffes possess a slight mane on the tail-stalk, which is most distinct at birth:
https://www.dreamstime.com/stock-photo-masai-giraffe-calf-walking-young-across-savanna-nairobi-national-park-kenya-nairobi-skyline-background-image83751771 and https://www.dreamstime.com/stock-photo-mother-baby-giraffe-going-walk-camelopardalis-than-weeks-old-as-still-has-its-umbilical-cord-attached-image68333446 and https://www.dreamstime.com/stock-images-standing-tall-image622554.

The okapi (Okapi johnstoni, https://en.wikipedia.org/wiki/Okapi) has a hardly-noticeable mane. However, in this species again the nuchal mane is fully developed at birth, disappearing in juveniles (https://www.zooborns.com/.a/6a010535647bf3970b0240a48578ab200d-popup).

Ingresado el 22 de noviembre de 2021 por milewski milewski | 2 comentarios | Deja un comentario

21 de noviembre de 2021

Occipital horn-tufts: a previously overlooked feature of (certain) giraffes

It is well-known that the horns of giraffids are unlike those of deer or bovids, in being permanent, skin-covered, and adorned by tufts of hair instead of points.

So who would have expected zoologists to keep overlooking features as obvious - and with as much taxonomic significance - as secondary horn-tufts? And on animals with as high a profile as giraffes?

And yet these have indeed been overlooked.

Giraffes possess a main pair of horns, which are tufted in juveniles but become bald in adults, particularly males. However, they also potentially possess an additional pair of horns, located at the posterior edge of the cranium. This is the occipital part of the skull, just above the nape (e.g. https://pixabay.com/photos/giraffe-profile-close-up-830532/).

The occipital horns develop only in mature males, only in some of the species of giraffes, and only in some individuals. However, it is in their undeveloped (incipient), not developed, condition that the occipital horns bear small tufts, which can clearly be seen in many photos (e.g. https://www.dreamstime.com/wild-giraffe-profile-image-south-african-wild-close-up-giraffe-profile-south-africa-wild-image156441687).

It is these additional horn-tufts that have escaped notice, as far as I know by everyone.

The occipital horn-tufts are located close to the top (distal extreme) of the mane. So in profile view they might be assumed to represent nothing more than the end of the mane. However, they are actually distinct in both position and tone (https://www.istockphoto.com/photo/giraffe-in-kennya-on-safari-africa-gm1354463380-429280885). Unlike the brown of the mane, the occipital horn-tufts are always blackish (https://www.dreamstime.com/royalty-free-stock-photography-giraffe-profile-image7086897).

The occipital horn-tufts are most obvious in adult females, and they are clearest in Giraffa tippelskirchi. They are small in Giraffa giraffa, and vestigial or absent in Giraffa camelopardalis and Giraffa reticulata.

GIRAFFA TIPPELSKIRCHI:

Because the occipital horn-tufts distinguish between different types of giraffes, they are useful taxonomically. They indicate that G. tippelskirchi is more closely related to G. giraffa than to G. camelopardalis, an affinity also borne out by pedal and laryngeal flags (see https://www.inaturalist.org/journal/milewski/48447-conspicuous-features-of-colouration-in-giraffes#).

One of the clearest illustrations on the Web is https://www.pond5.com/stock-footage/item/75223817-masai-giraffe-chewing-maasai-mara-kenya-Africa. In this subadult female individual of Giraffa tippelskirchi, the occipital horn-tufts are almost as long as the tufts on the tips of the main horns.

However, even in females of G. tippelskirchi, the occipital horn-tufts are subject to individual variation: http://www.oceanlight.com/spotlight.php?img=29974 and https://fineartamerica.com/featured/maasai-giraffe-eating-acacia-leaves-serengeti-ross-warner.html and https://www.dreamstime.com/baby-giraffe-trees-background-giraffes-world-s-tallest-mammals-thanks-to-their-towering-legs-long-necks-alone-image200452303 and https://www.istockphoto.com/search/2/image?page=7&phrase=masai%20giraffe.

One of the peculiarities of the occipital horn-tufts is that they are neither masculine nor precocial.

In giraffes, the main horn-tufts are so precocial that they are present at birth, and are proportionally larger in infants than in adults. However, this does not apply to the occipital horn-tufts, as shown in the following of Giraffa tippelskirchi:

adult female with neonates/infants:
https://www.dreamstime.com/stock-photos-mom-giraffe-her-baby-savanna-image15611253 and https://www.shutterstock.com/nb/image-photo/gorgeous-touching-moment-mother-giraffe-takes-1989333311 and https://www.istockphoto.com/photo/masai-giraffe-gm1257170489-368333298 and https://www.dreamstime.com/adult-giraffe-watches-over-calf-giraffe-nursery-savannah-adult-giraffe-watches-over-calf-giraffe-image124421523 and https://www.dreamstime.com/royalty-free-stock-photography-mom-giraffe-kiss-her-baby-image15611237 and https://www.dreamstime.com/giraffe-mother-calf-standing-plains-masai-mara-national-reserve-giraffe-mother-calf-standing-great-image190720043 and https://www.dreamstime.com/stock-photo-female-giraffe-baby-savannah-kenya-tanzania-east-africa-excellent-illustration-image78933000

infants:
https://www.shutterstock.com/nb/image-photo/close-masai-giraffe-nibbling-on-thornbush-1939699015 and https://www.dreamstime.com/close-up-baby-masai-giraffe-watching-camera-image213135920 and https://www.dreamstime.com/stock-photo-masai-giraffe-calf-tail-flicking-young-its-savanna-mara-kenya-baby-s-umbilical-cord-still-visible-making-image83750176 and https://www.dreamstime.com/giraffe-zebras-newborn-giraffe-mingles-mother-zebra-her-foal-image108548253 and https://www.agefotostock.com/age/en/details-photo/close-up-of-a-masai-giraffe-giraffa-camelopardalis-tippelskirchi-also-known-as-the-maasai-giraffe-or-kilimanjaro-giraffe/X5T-2549599.

The above photos show that, although the occipital horn-tufts are present at birth, they are not proportionately large in infants in the way that the main horn-tufts are.

The following are further illustrations in Giraffa tippelskirchi:

https://www.istockphoto.com/photo/two-giraffe-gm599765514-102984869

second photo in https://www.loe.org/blog/blogs.html?seriesID=65&blogID=43

https://www.dreamstime.com/masai-giraffe-profile-closeup-isolated-studio-shot-facing-left-his-mouth-open-tongue-beginning-to-protrude-white-image186124860

https://www.alamy.com/stock-photo-masai-giraffe-up-close-140383640.html

https://www.dreamstime.com/stock-photo-masai-giraffe-eating-acacia-aka-kilimanjaro-maasai-kenyan-leaves-its-long-grey-tongue-wrapped-image83752427

https://www.projectnoah.org/spottings/8674285/fullscreen

https://www.dreamstime.com/giraffes-world-s-tallest-mammals-thanks-to-their-towering-legs-long-necks-giraffe-s-legs-alone-taller-than-many-image200452329

The following show that the occipital horn-tufts disappear in adult males, even in G. tippelskirchi:

adolescent male:
https://www.istockphoto.com/photo/masai-giraffe-gm467510293-34473716

adult male:
https://www.agefotostock.com/age/en/details-photo/closeup-of-masai-giraffe-scientific-name-giraffa-camelopardalis-tippelskirchi-or-twiga-in-swaheli-image-taken-on-safari-located-in-the-tarangire-national/ESY-045336775

GIRAFFA GIRAFFA:

The following show that, in G. giraffa, the occipital horn-tufts are usually small but are usually discernible by their blackness. The best-developed example I have found is the following: https://depositphotos.com/279388852/stock-photo-wildlife.html.

adult females:
https://www.dreamstime.com/head-giraffa-isolated-white-background-head-giraffa-isolated-image147209689 https://www.shutterstock.com/nb/image-photo/south-african-giraffe-close-namibia-568255321
https://www.dreamstime.com/father-son-watching-feeding-giraffe-zoo-happy-kid-ha-father-son-watching-feeding-giraffe-zoo-happy-kid-image113118222

juvenile males:
https://www.dreamstime.com/giraffe-profile-eyes-giraffe-profile-eyes-closeup-wildlife-image148755686
https://www.dreamstime.com/stock-photo-little-boy-feeding-giraffe-zoo-day-time-image46341041.

The following show that the occipital horn-tufts are absent in adults of G. camelopardalis, even in females: https://www.shutterstock.com/nb/image-photo/close-view-giraffe-head-behind-brown-1554923213 and https://www.alamy.com/stock-photo-a-single-giraffe-profile-closeup-against-a-bright-blue-sky-39860494.html and https://pxhere.com/en/photo/1271059 and https://fr.dreamstime.com/photo-stock-profil-d-t%C3%AAte-girafe-image45463715 and https://www.dreamstime.com/stock-photo-giraffe-head-profile-s-isolated-background-image77327021 and https://www.austockphoto.com.au/image/giraffe-close-up-side-view-bidOS and https://snappygoat.com/free-public-domain-images-giraffe_male_animal_head_0/TV8x2YVx0HyL_HdJArEIjIT4-hY9pBBtuOySKGxbpzQ.html#,0,156 and https://www.dreamstime.com/stock-photos-giraffe-head-image335733.

GIRAFFA CAMELOPARDALIS:

The only evidence of occipital horn-tufts in G. camelopardalis is a trace in some individuals:

adult females:
https://www.dreamstime.com/stock-photos-reticulated-giraffe-portrait-image16544343

juveniles:
https://www.dreamstime.com/stock-photo-beautiful-side-profile-giraffe-wild-image77492366
https://www.shutterstock.com/nb/image-photo/giraffe-portrait-head-close-2040205991

infants:
https://dallas.culturemap.com/news/city-life/06-19-19-zoo-baby-giraffe-death-witten-anesthesia-canadian-zoo/
https://www.dreamstime.com/royalty-free-stock-photos-young-giraffe-eating-close-up-leaves-image40437778

The following show hybrids between G. camelopardalis and G. reticulata: https://www.dreamstime.com/stock-photo-reticulated-giraffe-profile-isolated-image-head-viewed-image87307138 and https://www.dreamstime.com/stock-images-reticulated-giraffe-portrait-image17151984 and https://www.shutterstock.com/nb/image-photo/artiodactyl-mammal-giraffe-family-giraffes-head-2048048231 and https://www.dreamstime.com/stock-photo-profile-young-reticulated-giraffe-head-side-image45800720 and https://es.123rf.com/photo_11772370_baby-giraffe-high-detail-profile.html and https://es.123rf.com/photo_11353011_jirafa-beb%C3%A9-perfil.html.

GIRAFFA RETICULATA:

The following shows the absence of occipital horn-tufts in juvenile female G. reticulata: https://www.dreamstime.com/stock-photo-reticulated-giraffe-head-side-profile-view-young-image58518677.

Ingresado el 21 de noviembre de 2021 por milewski milewski | 6 comentarios | Deja un comentario

20 de noviembre de 2021

The giraffe of the Laikipia region of Kenya: time to correct its classification?

@michalsloviak @chewitt1 @johnnybirder @jakob @jwidness @bobby23 @dejong @maxallen @mikeloomis @kokhuitan @calebcam

The Laikipia region lies on a plateau just northwest of Mount Kenya. The protection of a form of Giraffa on privately-owned lands here has seemingly brought a success in conservation. However, re-examination of the identity of this form may be sobering.

The following map of the Laikipia region shows the complex patchwork of properties which are being managed partly for the conservation of wildlife: https://kwcakenya.com/regional-associations/laikipia-conservancies-association/.

In iNaturalist there are currently nearly 130 observations of Giraffa in the Laikipia region, most of which have been identified as Giraffa camelopardalis reticulata.

The following, just beyond the Laikipia region to its northwest, has yet to be identified but looks like Giraffa camelopardalis rothschildi:
https://www.inaturalist.org/observations/115397.

The following from the western edge of the Laikipia region has been identified as Giraffa camelopardalis rothschildi: https://www.inaturalist.org/observations/19525098.

The following, from the central parts of the Laikipia region, have ambivalent identifications:
https://www.inaturalist.org/observations/14224598
https://www.inaturalist.org/observations/46599973.

The following has been identified as reticulata but fails to conform to that taxon:
https://www.inaturalist.org/observations/30528961.

Most or all of the other observations from the Laikipia region also fail to conform to reticulata with respect to at least two features. Firstly, the whitish 'matrix' is too broad on the distal part of the neck to fit reticulata. Secondly, the lower legs are pale, resembling rothschildi rather than reticulata.

I have seen no observations from the Laikipia region that conform fully to reticulata as typified in the region of Kenya farther to the east, in and near Samburu National Reserve (https://en.wikipedia.org/wiki/Samburu_National_Reserve).

What the above indicates is that the whole population of Giraffa in the Laikipia region consists of hybrids between reticulata and rothschildi. Some individuals resemble reticulata closely enough to be identified as such by experienced iNaturalists, but on closer examination even these show signs of hybridisation (see https://www.inaturalist.org/journal/milewski/59852-reframing-the-reticulated-giraffe#).

An intermediate status makes sense given that the Laikipia region is located between the original ranges of reticulata and rothschildi. But which form inhabited the plateau at the time of European arrival?

I suspect that Giraffa was largely exterminated from the Laikipia region during the initial period of farming by European settlers, the surviving individuals being hybrids for reasons that remain to be established. With more recent conservation, the hybrid population seems to have spread, with the encouragement of landowners, to occupy most of the region.

What makes this ostensibly hybrid status all the more important is the growing realisation that reticulata and rothschildi belong to different species, not merely subspecies. If the population in the Laikipia region is an interspecific hybrid, its value for conservation is particularly questionable.

We need to search the literature to establish which form was originally indigenous to the Laikipia region. It cannot be assumed that this was a zone of natural hybridisation in the first place. It would also be helpful to document the degree to which the original population was depleted during the period when management was inimical to Giraffa.

We need to decide whether reticulata and camelopardalis are different species. In my view, one of the few reasons to doubt such taxonomic separation is the apparent fertility of the hybrids.

A survey would be helpful among landowners within the Laikipia region, based on questionnaires re the historical status of Giraffa on the various properties.

For now, I recommend that all current identifications of reticulata in this region should be changed to reticulata X rothschildi. If the species-distinction is accepted, the change should be to Giraffa reticulata X Giraffa camelopardalis rothschildi.

The current assumptions give a misleadingly encouraging impression of the overall status of reticulata (see https://www.researchgate.net/figure/The-distribution-of-giraffes-in-Laikipia-Samburu-MarsabitMeru-Ecosystems-2017_fig7_325145734). Some 60% of what have been counted as reticulata Kenya-wide occur in Laikipia county, which is only part of the Laikipia region (https://wildlifedirect.org/wp-content/uploads/2018/06/CS-report-GGR-2018v-4.pdf and https://en.wikipedia.org/wiki/Laikipia_County). This means that the true remaining population of unhybridised reticulata in Kenya is possibly only a third of what has been published recently.

There is no cause for complacency in the conservation of subspecies reticulata, partly because it is now as rare (in unhybridised form) as the West African Giraffa camelopardalis peralta, and partly because it may deserve the attention of a full species.

Ingresado el 20 de noviembre de 2021 por milewski milewski | 4 comentarios | Deja un comentario

19 de noviembre de 2021

Reframing the reticulated giraffe

Which iNaturalists would identify the following as the reticulated giraffe? https://www.discoverimages.com/herd-reticulated-giraffes-common-zebra-background-5743413.html#openModal. This Post may help you to correct some misperceptions.

Everyone knows that a diagnostic feature of the reticulated giraffe (Giraffa reticulata) is the conversion of the normal blotchiness of giraffes into a network effect (http://cannundrum.blogspot.com/2014/08/reticulated-giraffe.html and https://www.sciencephoto.com/media/989443/view/reticulated-giraffe-young-standing-close-to-its-mother and https://similarbutdifferentanimals.com/2017/08/27/kenyan-giraffes-whats-the-difference-between-a-masai-a-reticulated-and-a-rothschilds-giraffe/).

However, now that we have examined flags (https://www.inaturalist.org/journal/milewski/48447-conspicuous-features-of-colouration-in-giraffes#) and pallor (https://www.inaturalist.org/journal/milewski/59814-the-puzzle-of-conspicuous-pallor-in-a-sahelian-giraffe-part-1#), we can re-characterise the reticulated giraffe from a broader perspective.

Here we have the most uniformly-coloured and most thoroughly camouflaged of all giraffes (https://www.dreamstime.com/reticulated-giraffe-digital-painting-large-male-computer-oil-image198653708 and https://www.westend61.de/en/imageView/RHPLF07893/reticulated-giraffe-giraffa-camelopardalis-reticulata-kalama-conservancy-samburu-kenya-east-africa-africa).

The caudal flag is the same as in other giraffes, the tail-tassel being black:
https://www.youtube.com/watch?v=4LRkGVhmXx8
https://www.canstockphoto.com/reticulated-giraffe-walking-in-the-15692006.html

Here is a reminder of what a laryngeal flag looks like: https://www.ardeaprints.com/reticulated-giraffe-grazing-small-tree-1305806.html#modalClose.

There is no laryngeal flag in Giraffa reticulata:
https://www.robertharding.com/preview/817-127671/reticulated-giraffe-giraffa-camelopardalis-reticulata-samburu-national-reserve/
https://africafreak.com/reticulated-giraffe
https://animal.fandom.com/wiki/Reticulated_Giraffe?file=Giraffe1.jpg
https://www.shutterstock.com/image-photo/reticulated-giraffe-giraffa-camelopardalis-reticulata-samburu-648809500
https://www.westend61.de/en/imageView/RHPLF07894/a-portrait-of-a-reticulated-giraffe-giraffa-camelopardalis-reticulata-kalama-conservancy-samburu-kenya-east-africa-africa

Giraffa reticulata also lacks the pale and/or spotless patches on the cheeks that are seen in other giraffes.

There is no pedal flag in Giraffa reticulata:
https://www.dreamstime.com/reticulated-giraffe-samburu-national-reserve-feeding-kenya-image182437028
https://www.alamy.com/a-reticulated-giraffe-standing-in-the-open-at-shaba-national-reserve-in-kenya-image223136384.html

Many photos do show lower legs pale enough to qualify as a pedal flag, but these are from the Laikipia region of Kenya (https://www.inaturalist.org/observations/30528961) and from zoos (https://www.gettyimages.com.au/detail/news-photo/reticulated-giraffes-seen-at-the-wroclaw-zoological-garden-news-photo/1226313463?adppopup=true and https://naturerules1.fandom.com/wiki/Reticulated_Giraffe?file=D4y0zv7-751d12ae-d3a6-478e-a05c-320ec6721756.jpg), where there has been hybridisation with Giraffa camelopardalis.

The following unhybridised individual shows the maximum paleness on the feet in Giraffa reticulata, which does not qualify as a pedal flag: https://focusedcollection.com/167577218/stock-photo-reticulated-giraffe-standing-on-ground.html.

Here is a reminder of what an ilial flag looks like: https://www.shutterstock.com/nb/image-photo/two-giraffes-standing-bushland-chobe-flood-1282706323 and https://www.shutterstock.com/nb/image-photo/south-african-giraffe-cape-giraffa-herd-1173965401.

There is no ilial flag in Giraffa reticulata:
https://artofsafari.travel/wp-content/uploads/2020/04/Shutterstock_Kenya_Samburu_ReticulatedGiraffe.jpg
https://www.gettyimages.com.au/detail/photo/reticulated-giraffes-on-lewa-downs-royalty-free-image/534357716?adppopup=true
http://shutterstock.puzzlepix.hu/kep/1846122715.

The form of the forehead and rostrum is distinctive in both sexes of Giraffa reticulata. The bump on the forehead is relatively abrupt. In mature males, the rostrum remains free of enlargement by ossification:

female:
https://www.istockphoto.com/photo/reticulated-giraffe-head-profile-gm177117647-1906905
https://www.gettyimages.com.au/detail/photo/reticulated-giraffe-browsing-on-acacia-leaves-royalty-free-image/520073474?adppopup=true
https://www.dreamstime.com/girafe-reticulee-giraffa-camelopardalis-reticulata-reticulated-giraffe-head-adult-behind-acacia-tree-samburu-park-kenya-image170944255

male:
https://www.alamy.com/head-portrait-of-reticulated-giraffe-giraffa-camelopardalis-reticulata-samburu-national-reserve-kenya-africa-image262992203.html
https://www.gettyimages.com.au/detail/news-photo/close-up-of-two-reticulated-giraffes-in-the-samburu-news-photo/1053083674?adppopup=true
https://www.dreamstime.com/reticulated-giraffe-giraffa-camelopardalis-reticulata-bird-its-neck-red-billed-oxpecker-buphagus-erythrorhynchus-samburu-image196305808
https://www.alamy.com/stock-photo-reticulated-giraffe-head-shot-samburu-national-reserve-kenya-africa-31573358.html
https://www.gettyimages.com.au/detail/news-photo/reticulated-giraffe-giraffa-camelopardalis-reticulata-close-news-photo/578258890?adppopup=true
https://www.gettyimages.com.au/detail/photo/reticulated-giraffe-portrait-samburu-national-royalty-free-image/1311465280?adppopup=true

Compare the latter with mature males of Giraffa tippelskirchi, in which not only the forehead bump but also the rostrum become ossified: https://www.alamy.com/close-up-view-of-the-head-of-a-male-giraffe-in-profile-image338486132.html.

Another difference between Giraffa reticulata and the hybrid population in the Laikipia region is that, in the latter, some individual mature males develop pallor on the head (e.g. https://www.gettyimages.com.au/detail/news-photo/male-reticulated-giraffe-stands-in-the-lewa-wildlife-news-photo/1234044912?adppopup=true).

Having begun this Post with a test, let me end it with another one along similar lines. iNaturalists, how would you identify the following? https://www.gettyimages.com.au/detail/photo/giraffes-walking-royalty-free-image/522081236?adppopup=true.

Ingresado el 19 de noviembre de 2021 por milewski milewski | 0 comentarios | Deja un comentario

The puzzle of conspicuous pallor in a Sahelian giraffe, part 2

To appreciate fully the meaning of the pallor in G. c. peralta, it may also be useful to review the incidence of anomalous darkness in giraffes - which is of a different kind.

In Giraffa giraffa in particular, there is a pattern of sexual dimorphism in which fully mature males - which can weigh up to 1.5 tonnes as opposed to the average 0.8 tonnes of adult females - darken in conjunction with producing strong odours from skin glands (https://www.facebook.com/jumbojunction/photos/a.1554448954625642/6189916674412157/). This change is unpredictable, individually variable, and not necessarily permanent.

The darkness and smelliness of males at the peak of breeding condition detract from their camouflage, but pose no particular puzzle. This is because a) it is normal for males, particularly in sexually dimorphic species, to trade off security for sexual advantage, b) the self-advertisement of males need not compromise the camouflage of females and juveniles, because gregariousness is loose in giraffes, c) males may possibly be less vulnerable than females to predation, and d) darkness, although somewhat conspicuous by day, remains inconspicuous by night or in twilight.

The following illustrations of masculine darkness suggest that this pattern applies to only a limited extent in some of the species and subspecies of giraffes:

Giraffa giraffa giraffa
https://www.tripadvisor.in/LocationPhotoDirectLink-g312616-d7122939-i314711382-Moholoholo_Mountain_View_Bush_camp-Hoedspruit_Limpopo_Province.html
http://www.timaverybirding.com/photos/albums/2013/08-09_africa/20130901/safari/giraffe_b.jpg
https://es.123rf.com/photo_21431497_giraffe-bull.html
https://www.facebook.com/mafojanisafaris-100408458676624/photos/pcb.143965800987556/143965734320896/
https://www.africahunting.com/threads/dark-giraffe-bull-hunt-south-africa.55821/
https://www.facebook.com/mafojanisafaris-100408458676624/photos/pcb.143965800987556/143965737654229/
https://www.shutterstock.com/image-photo/big-dark-male-giraffe-swaziland-nature-1719565081
https://www.alamy.com/stock-photo-southern-giraffe-giraffa-camelopardalis-giraffa-bull-collects-flowers-73318924.html
https://www.dreamstime.com/stock-photo-giraffe-browsing-high-leaves-bush-image50867157

Giraffa tippelskirchi
https://www.flickr.com/photos/davidbygott/4037387278
https://www.istockphoto.com/photo/masai-giraffe-gm1296042780-389584472

Giraffa reticulata
https://www.dreamstime.com/royalty-free-stock-photos-reticulated-giraffe-image26813158
https://www.dreamstime.com/full-body-portrait-reticulated-giraffe-giraffa-camelopardalis-reticulata-walking-northern-kenya-savannah-landscape-africa-image131865776
https://www.dreamstime.com/stock-images-male-reticulated-giraffe-zoo-waiting-food-miami-south-florida-image38695804

Giraffa camelopardalis camelopardalis
https://www.dreamstime.com/reticulated-giraffe-reticulated-giraffe-standing-sun-nice-day-image108993437
https://www.dreamstime.com/stock-photo-giraffes-mysore-zoo-i-clicked-photo-my-visit-baby-giraffe-was-eating-food-box-known-s-unique-image46191110

Giraffa camelopardalis rothschildi
https://www.istockphoto.com/photo/female-giraffe-with-a-baby-in-the-savannah-gm669752120-122872959
https://www.alamy.com/stock-photo-mature-male-rothschilds-giraffe-giraffe-camelopardis-rothschildi-at-47964879.html
https://www.flickr.com/photos/kukkaibkk/48788810726
https://blog.goway.com/globetrotting/2016/10/flamingos-galore-and-more-in-lake-nakuru-national-park-kenya/
https://www.shutterstock.com/nb/video/clip-2484515-wild-group-extremely-endangered-rothschild-giraffe-giraffa

In the case of G. c. peralta, the blotches do seem to darken in mature males (see e.g. https://www.inaturalist.org/observations/28558145). However, this is not enough to give the figure a dark aspect overall, because a) the matrix remains the same as in females and immature males, and b) the head does not darken.

Is it not apparent in this dual context that - relative to both other ruminants of the Sahel/Sahara and other forms of giraffe across Africa - any tendency towards conspicuous pallor in giraffes shows a basic adaptive shift? And is this not a significant exception to any generalisation that the colouration of giraffes is designed for camouflage?

Ingresado el 19 de noviembre de 2021 por milewski milewski | 1 comentario | Deja un comentario

18 de noviembre de 2021

The puzzle of conspicuous pallor in a Sahelian giraffe, part 1

Does anyone doubt that, in general, the colouration of giraffes is a form of camouflage?

The flags which I have described (see https://www.inaturalist.org/journal/milewski/48447-conspicuous-features-of-colouration-in-giraffes#) hardly negate this generalisation, because they are subsidiary features.

However, one subspecies of giraffe has overall colouration so conspicuously pale that it does seem to mean a partial negation (https://africa.cgtn.com/2018/11/22/niger-to-move-protected-giraffes-as-habitat-shrinks/ and https://www.dreamstime.com/stock-photo-salivating-giraffe-its-dripping-saliva-epic-image70986808).

I refer to Giraffa camelopardalis peralta (https://en.wikipedia.org/wiki/West_African_giraffe and https://www.researchgate.net/profile/Bertrand-Chardonnet/publication/296408231_Antelope_Survey_Update_n9_November_2004_IUCN_SCC_Antelope_Specialist_Group_Report_Special_Issue_West_and_Central_Africa/links/56d5466608ae2cd682b9a145/Antelope-Survey-Update-n9-November-2004-IUCN-SCC-Antelope-Specialist-Group-Report-Special-Issue-West-and-Central-Africa.pdf#page=36 and http://travel2unlimited.com/niger-koure-giraffes/) of the western Sahel.

The particular pallor of Giraffa camelopardalis peralta is owing mainly to the breadth of the whitish 'matrix' among the blotches (see https://www.inaturalist.org/observations/91931958 and https://www.inaturalist.org/observations/67258492).

This differs from any pale overall effect in the form of giraffe inhabiting the edge of the Namib desert in southern Africa, which is owing mainly to fading of the blotches themselves and does not particularly affect the head or legs (Giraffa giraffa angolensis, see https://app.nimia.com/fpvideo/746972087/746972087-giraffe-walking-namibia and https://giraffeconservation.org/programmes/nw-namibia/).

The following photos of the most pallid individuals show how the camouflage effect has been compromised in Giraffa camelopardalis peralta in its current habitat. Although a corollary of the pallor is that the auricular and pedal flags are reduced, the caudal flag is if anything enhanced, because the tail-tassel remains black in all individuals.

https://www.inaturalist.org/observations/89357382
https://www.inaturalist.org/observations/66647598
https://www.inaturalist.org/observations/66511242
https://www.inaturalist.org/observations/66511269
https://www.inaturalist.org/observations/91633228
https://www.inaturalist.org/observations/84033823
https://www.inaturalist.org/observations/66511261
https://www.inaturalist.org/observations/66510605
https://www.inaturalist.org/observations/66510563
https://www.bornfree.org.uk/articles/conservation-update-gcf

Can it not be said that G. c. peralta has, in evolutionary terms, switched from inconspicuous colouration to conspicuous colouration? The mechanism has been a quantitative shift (mainly an encroachment of the pale matrix relative to the blotching), but the effect seems qualitative.

If so, this seems convergent with the conspicuous pallor of three other gregarious ruminants of the southern fringes of the Sahara, as exemplified by the following views of Oryx dammah:

https://www.shutterstock.com/nb/image-photo/herd-scimitar-horned-oryx-dammah-walking-1114267055 and https://www.shutterstock.com/nb/image-photo/herd-scimitar-horned-oryx-dammah-walking-1114267097.

Oryx dammah (https://www.inaturalist.org/observations/80301962), Addax nasomaculatus and Nanger dama ruficollis (https://www.hatadaranch.com/dama) all inhabited the vicinity of the Sahara, with O. dammah coexisting in the Sahel with giraffes (including G. c. peralta), A. nasomaculatus penetrating the Sahara itself, and N. d. ruficollis living in the eastern Sahel (where the local form of giraffe was not as pallid). In converging on a pattern of conspicuous overall pallor, these species set an unique pattern among the arid-adapted ungulates of the world.

I realise that:

  • arid-adapted reptiles, birds, and small mammals tend to be pallid as a form of crypsis in the pale environments of deserts, particularly sandy deserts;
  • there is seasonal variation in the colouration of A. nasomaculatus and possibly also the other two bovids referred to here; and
  • hippotragins and gazelles tend to be adaptively conspicuous even in savannas, which can be partly explained by the futility of trying to hide as gregarious animals in the open.

However, ruminants in the southern African deserts and semi-deserts (https://www.istockphoto.com/photo/gemsbok-oryx-in-namib-desert-gm146923746-14197980 and https://www.agefotostock.com/age/en/details-photo/springbok-antidorcas-marsupialis-adults-walking-on-sand-namib-desert-in-namibia/YS1-1722745) lack the relevant pattern of colouration. In the degree of their pallor, our three bovids seem to have adapted in convergent ways to the particular conditions of the Sahara and its southern edges.

Seen in this context, does the pallor of G. c. peralta not seem to be part of a regional faunistic pattern?

The following illustrate the pallor of our three bovids, and the adaptive convergence that this represents.

Oryx dammah:
https://www.shutterstock.com/nb/image-photo/huge-herd-scimitarhorned-oryx-sahara-wildlife-1988644823
https://www.shutterstock.com/nb/image-photo/herd-scimitar-horned-oryx-dammah-walking-1114267079
https://www.inaturalist.org/observations/74899599
https://www.shutterstock.com/nb/image-photo/antelope-scimitar-horn-oryx-leucoryx-due-1605546127 https://www.shutterstock.com/nb/image-photo/antelope-scimitar-horn-oryx-leucoryx-due-1606769167 https://www.shutterstock.com/nb/image-photo/scimitar-oryx-aka-sahara-endangered-animal-1093058519 https://www.shutterstock.com/nb/image-photo/very-rare-scimitarhorned-oryx-dammah-extinct-1932362348
https://www.shutterstock.com/nb/image-photo/scimitar-oryx-aka-sahara-endangered-animal-1093058531
https://www.shutterstock.com/nb/image-photo/scimitar-oryx-aka-sahara-endangered-animal-1219348936
https://wildlifeconservation101.files.wordpress.com/2012/04/images-2.jpeg

Addax nasomaculatus:
https://www.dreamstime.com/stock-photo-beautiful-addax-desert-eilat-image72805856
https://www.dreamstime.com/addax-walking-jebil-national-park-tunisia-image126127489
https://creatures-of-the-world.fandom.com/wiki/Addax?file=Adult_addax.jpg https://pixabay.com/photos/addax-negev-desert-desert-dweller-4764789/
https://www.istockphoto.com/photo/a-critically-endangered-addax-also-known-as-the-screwhorn-or-white-antelope-stops-to-gm1141454086-305811175
https://www.dreamstime.com/royalty-free-stock-photos-antelope-addax-image19237788

Nanger dama:
https://naturerules1.fandom.com/wiki/Dama_Gazelle?file=3e2b7d460fe86e7d50d1bfec49723c12.jpg
https://www.iucn.org/ssc-groups/mammals/mammals-a-e/antelope/resources http://lh3.ggpht.com/_1wtadqGaaPs/TCiTe14fKOI/AAAAAAAAGm4/SeKuL3yo1c4/s1600-h/tmp1127_thumb4.jpg
https://www.texasdivide.com/dama-gazelle

to be continued...

Ingresado el 18 de noviembre de 2021 por milewski milewski | 3 comentarios | Deja un comentario

17 de noviembre de 2021

Could Gleditsia have been made by megafungi as well as megaherbivores?

Among leguminous woody plants, mimosas (Mimosaceae) are far more likely than caesalps (see https://www.inaturalist.org/journal/milewski/59528-caesalps-on-southern-continents-part-1#new_comment) to be favourite foods of large herbivores. Accordingly, it is mimosas, not caesalps, that tend to possess large spines.

However, the genus Gleditsia (https://en.wikipedia.org/wiki/Gleditsia) is exceptional among caesalps (see https://www.inaturalist.org/journal/milewski/59528-caesalps-on-southern-continents-part-1#) in the degree to which it looks and acts like a member of the mimosas (http://www.nzdl.org/cgi-bin/library?e=d-00000-00---off-0hdl--00-0----0-10-0---0---0direct-10---4-------0-1l--11-en-50---20-help---00-0-1-00-0-0-11----0-0-&a=d&c=hdl&cl=CL1.12&d=HASH011ec19a37bb817d72319187.33).

Gleditsia has extremely large spines (https://en.wikipedia.org/wiki/Honey_locust and (https://www.britannica.com/plant/honey-locust-tree-genus and https://www.feedipedia.org/content/honey-locust-gleditsia-triacanthos-thorns-madrid-spain and https://canr.udel.edu/udbg/?plant=gleditsia-triacanthos)
and https://www.etsy.com/au/listing/1065477392/huge-honey-locust-thorns-real-acacia?ref=pla_sameshop_listing_top-1 and https://www.etsy.com/au/listing/777216641/huge-honey-locust-thorns-real-acacia?ref=pla_sameshop_listing_top-2&cns=1), as well as small leaflets, flowers lacking obvious petals, and fruits functionally similar to those of mimosas such as that widespread 'acacia', Vachellia nilotica (https://en.wikipedia.org/wiki/Vachellia_nilotica).

Implicit in this convergence with mimosas is that nutritional modes will have likewise converged: we can expect Gleditsia to be adapted to exploit nutrients recycled in urine and faeces, while at the same time fixing atmospheric nitrogen.

It comes as a surprise, therefore, that Gleditsia not only lacks nitrogen-fixing nodules but is listed as possessing ectomycorrhizae (see https://www.inaturalist.org/journal/milewski/59485-the-mystery-of-the-missing-mycorrhizae#). These macroscopic fungal root-extensions are rare among mimosas (https://mycorrhizas.info/ecm.html) and antithetical to the nutritional strategy typical of mimosas.

Because the largest mycorrhizal fungi tend to be associated with the roots of plants unattractive to large herbivores, and to promote nutritional regimes antagonistic to herbivory, Gleditsia presents a puzzle. Is its nutritional strategy really similar to those of caesalps which are neither attractive as food for herbivores, nor spinescent (https://mycorrhizas.info/ecm.html)?

If it really is ectomycorrhizal, Gleditsia is unique in combining some of the largest stem-protecting spines and some of the largest root-assisting fungi.

I cannot resolve this question because I have yet to find the original paper reporting ectomycorrhizae in Gleditsia. However, I can further explain spinescence in the context of ectomycorrhizal plants generally.

Spines, thorns and prickles vary greatly in their size, the part of the plant from which they are derived, and their adaptive functions. The large spines of many species of 'acacias' (now genus Vachellia) are derived from stipules (e.g. http://elephantseyegarden.blogspot.com/2010/06/fever-tree-umbrella-thorn-mimosa-port.html).

The largest spines derived from stipules and stems of dicotyledonous plants serve to control the foraging of the largest herbivores. This control should not be confused with deterrence, because plants with large spines are likely to be promoted by regimes of intense herbivory that recycle nutrients via faeces and urine while retarding competing plants. The function of these large spines is not to prevent loss of foliage as much as to protect the crucial regenerative organs/tissues, such as shoots and cambium, in the interests of plant and herbivore alike.

Spines have been established to occur in several genera of ectomycorrhizal plants, but they are of a different kind, compatible with a nutritional regime marginalising large herbivores.

The boreal conifer Picea (https://www.shutterstock.com/nb/video/clip-17336719-closer-look-picea-pungens-blue-spruce-thorny), the Australian pea Gastrolobium (https://www.ukwildflowers.com/Web_pages/gastrolobium_spinosum_prickly_poison.htm), and several Mediterranean and Californian species of oaks Quercus (https://naturenet.net/blogs/2009/01/15/crimson/) are ectomycorrhizal and possess leaf-spines similar to that familiar plant, holly (https://en.wikipedia.org/wiki/Ilex_aquifolium).

Leaf-spinescent plants are basically different from stem- or stipule-spinescent plants in that the leaves are too sclerophyllous (rigidly fibrous and lignified) to be particularly attractive to herbivores in the first place. They generally occur in ecosystems poor in large herbivores, where the main consumer of plant matter is episodic wildfires (https://www.academia.edu/7565234/Ecology_of_Australia_the_effects_of_nutrient_poor_soils_and_intense_fires). The spines can be thought of as an extension of the unpalatability of the leaves themselves, rather than a means of collaboration with herbivores as seem in spinescent 'acacias'.

Spinescence in ectomycorrhizal plants can therefore be summarised as follows:

In general, ectomycorrhizal plants lack spines, which is unsurprising because the nutritional regimes to which they are adapted are unsuitable for large herbivores. Those ectomycorrhizal species possessing spines tend to have a form of spinescence (i.e. leaf-spinescence) associated with limited herbivory. The stem-spinescence of Gleditsia is so unusual among ectomycorrhizal plants, and the association of Gleditsia with large herbivores is so obvious, that it calls into question the very claim that Gleditsia possesses ectomycorrhizae.

Ingresado el 17 de noviembre de 2021 por milewski milewski | 9 comentarios | Deja un comentario