Species diversification in chameleons

Species diversification in chameleons

by Alex Negro Science

From earlier studies, we know that the first chameleons evolved in the late Cretaceous, about 90 million years ago, on mainland of Africa. Around the border between the Cretaceous and Tertiary periods, about 65 million years ago, different species began to evolve. It is still unclear today which factors contributed to the diversity of species. Two researchers from Swansea University in Wales have now used various computational models of phylogenetics to investigate what might have influenced diversification (the splitting of chameleons into many different species).

First, they studied the diversification of chameleon species in Madagascar. In terms of evolutionary history, there are two points in time when chameleons apparently spread across the sea from mainland Africa to Madagascar. One is about 65 million years in the past, the other 45 million years. You could now think that the climatically extremely different habitats in Madagascar could have driven the evolution of the species very quickly after the spread across the sea. To the surprise of the researchers, however, no evidence of this was found. The species richness of chameleons on Madagascar must therefore come from the fact that chameleons spread there very early and thus simply had much more time to develop into different species than elsewhere.

Furthermore, the researchers investigated whether switching between two ecomorphs – from ground-dwelling stub-tailed chameleons to tree-dwelling chameleons with longer tails – had an impact on species diversity. Rather surprisingly, this did not seem to be the case. The evolution to tree-dwellers with longer tails occurred relatively early on one or two occasions. No evidence could be found that different ecomorphs accelerated diversification. Instead, speciation rates were found to slow down progressively over the last 60 million years. Only a very early dispersal event of the genus Bradypodion in South Africa around 10 million years ago was accompanied by a two- to fourfold diversification rate.

As a third focus of the study, the researchers examined the genus Bradypodion. During the climate change in the Miocene around 10 million years ago, South Africa changed a lot. Forests disappeared, leaving behind isolated forest habitats and, in between, savannahs, some of which are now so-called hot spots of biodiversity. Two of them, the Cape Floristic Region at the southwestern tip of South Africa and Maputuland-Pondoland-Albany on the east coast of South Africa, are home to a particularly large number of Bradypodion species. Each species is limited to a geographically very clearly defined area. The researchers, therefore, suspect that Bradypodion species have actually evolved faster under the influence of habitat change. It should be noted that the diversification rate of the genus Bradypodion is probably rather underestimated, as there are still many hidden species to be assumed.

Diversification dynamics of chameleons (Chamaeleonidae)
Stephen Giles, Kevin Arbuckle
Journal of Zoology, 2022
DOI: 10.1111/jzo.13019

Preferred perches in Bradypodion pumilum

Preferred perches in Bradypodion pumilum

by Alex Negro Science

It has long been known that most chameleon species move around on branches. However, research into how and which branches they prefer to use has so far been based mainly on nocturnal observations. At night, chameleons are easier to find in bushes and trees because they usually sleep on the ends of branches and are easy to spot with a torch. However, less is known about the use of perches during the chameleons’ active time, namely during the day. The herpetologist Kristal A. Tolley from the Kirstenbosch Research Centre in Cape Town, South Africa, has now conducted a study to find out which perch sizes Bradypodion pumilum prefers at night and during the day.

It is known from other tree-dwelling reptiles that they tend to seek out thinner perches at night, but use different perch sizes during the day. The result of the study was all the more surprising: the branches used by Bradypodion pumilum did not differ in diameter or variety during the day and night. An astonishingly high range of branches was used overall. The only correlation found was with body size, which seems logical in principle: The larger the chameleon, the thicker the perches used.


Is it like night and day? Nocturnal versus diurnal perch use by dwarf chameleons (Bradypodion pumilum)
Krystal A. Tolley
African Journal of Herpetology
DOI: 10.1080/21564574.2022.2098392

Chamaeleo chamaeleon in Turkey

Chamaeleo chamaeleon in Turkey

by Alex Negro Science

The European chameleon Chamaeleo chamaeleon inhabits a range that extends from North Africa through southern Portugal and Spain as well as Cyprus and Malta to Lebanon, Syria and Turkey. So far, however, very little is known about the populations in Turkey.

Turkish biologists have recently undertaken the first small study to change this state. They examined 29 European chameleons for their snout-vent-length and, using skeletochronology, for their age. 15 of them were males, 14 females. The animals studied were museum specimens from Dokuz Eylül University. They were collected in the surroundings of the Akyatan lagoon at earlier times. Akyatan is located in the south of Turkey directly on the Mediterranean Sea, about 200 km from the Syrian border. The nearest major Turkish cities are Mersin and Adana.

The average head-torso length of Chamaeleo chamaeleon from Akyatan was 85.34 mm, with females slightly larger than males. The smallest chamaeleon measured 59.71 mm, and the largest 106.84 mm. Thus, the studied population in Akyatan seems to be possibly somewhat smaller than the comparative populations in Spain and Egypt. However, the numbers of animals examined are too small to be able to make reliable statements about this. The age of the animals was between two and four years. The males reached sexual maturity after the first hibernation, while the females did not reach sexual maturity until the second year of life.

Age and body size of the Mediterranean Chameleon, Chamaeleo chamaeleon (Linnaeus 1758) (Lacertilia: Chamaeleonidae) specimens collected from Adana, Türkiye
Elif Yildirim, Nurettin Beşer, Can Yilmaz, Kamil Candan, Yusuf Kumlutaş, Çetin Ilgaz, Elnaz Najafi Majd
Commagene Journal of Biology
DOI: 10.31594/commagene.1104020

Factors in the geographical dispersal of chameleons

Factors in the geographical dispersal of chameleons

by Alex Negro Science

For a long time, people have been trying to find out how and why chameleons have spread across the African continent, to islands and as far as Europe and Asia. French scientists, in collaboration with international colleagues, have now used phylogenetics and various computational models to investigate how the factors of body size, coastal habitat and extreme lifestyles may have affected the distribution of different chameleon species. The study examined 181 species divided into nine main biogeographical regions: North Africa and Arabia, Central Africa, Southeast Africa, Southwest Africa, India, Socotra, Madagascar, Comoros and Seychelles.

Chameleon species that occurred more than 10 km from the sea historically spread significantly less than the 74 coastal chameleon species. A similar phenomenon is known from skinks and crocodiles. Dispersal probably took place mainly along the coasts, mostly on the same continent and only rarely across the water to other continents or islands.

The size of the different chameleons also seems to have influenced their dispersal throughout history: Large chameleons spread further and more frequently than small chameleons. This could be related to the fact that larger chameleons have a lower metabolic rate – so they need less energy overall relative to smaller competitors. In addition, larger chameleons lay clutches with significantly more eggs, which simply gives them an advantage in numbers.

A somewhat unexpected result came from the study of different life cycles. One would initially assume that short life cycles are associated with faster dispersal. In fact, the calculations showed that especially chameleon species with extreme life cycles spread further. Thus, those that reproduced particularly slowly or particularly quickly were historically more successful among chameleons than the species “in the middle”. In this regard, the authors consider whether particularly slow life cycles with late sexual maturity and long gestation might be more successful on the same continent, while faster reproductive strategies with large clutches are more favourable for dispersal across the sea to islands and other continents. In line with this, Furcifer polleni and Furcifer cephalolepis in Comoros and Chamaeleo zeylanicus in India, all three examples of aquatic dispersal, have a very fast life cycle.

The 34 chameleon species with the combination of living close to the coast, large size and extreme life cycle had a 98% higher dispersal rate than species without these characteristics.  All in all, this is certainly a very theoretical study, but it nevertheless provides exciting insights into the historical distribution and dispersal of chameleons.

Chameleon biogeographic dispersal is associated with extreme life history strategies
Sarah-Sophie Weil, Laurie Gallien, Sébastien Lavergne, Luca Börger, Gabriel W. Hassler, Michaël P.J. Nicolaï & William L. Allen
Ecography
DOI: 10.1111/ecog.06323

Hidden species within the genus Chamaeleo

Hidden species within the genus Chamaeleo

by Alex Negro Science

Thanks to genetic studies, the identification of species is much more precise today than it was a few decades ago. However, genetics always raises new questions. The genus Chamaeleo currently has 14 species. Scientists from South Africa have now investigated whether there might be other ‘hidden’ species of the genus Chamaeleo. At the same time, they investigated where the origin of the genus Chamaeleo might lie. For this purpose, the genetic material of all 14 species recognised so far was examined. Exciting results came to light: of the fourteen Chamaeleo species, thirteen were confirmed, but one was questioned. In addition, several new candidate species were identified.

The two different populations of Chamaeleo anchietae in western Angola and in south-eastern Congo and Tanzania probably represent two different species. If the animals from the Democratic Republic of Congo and Tanzania were true to be elevated to species status in the future, they would have to be named Chamaeleo vinckei according to taxonomy and a species description from 1950.

Chamaeleo gracilis seems to hide – which would not be surprising due to its wide distribution – at least three independent species. The “real” Chamaeleo gracilis would be found in Liberia, Sierra Leone and Guinea. The other two groups originate from the triangle of countries between Chad, Cameroon and the Central African Republic and from the border between Kenya and Tanzania. Unfortunately, only single specimens of Chamaeleo gracilis have been sampled, so no more far-reaching recommendation on the splitting of species can be made at this point.

The flap-necked chameleon (Chamaeleo dilepis), currently described as a single species, could contain a total of three species. One of the genetically distinct populations occurs in eastern Africa in Tanzania and Rwanda, while a second species is found in southern and eastern Africa, from South Africa through Botswana, Zambia, Namibia, Mozambique and Malawi to southern Tanzania. The third species would be distributed in west central Africa between Angola and the Congo. None of the candidate species matches the eight subspecies described so far purely on the basis of appearance. Therefore, a complete review of the previous subspecies, their status and the species status of the three newly emerged clades is necessary.

The results of the study on Chamaeleo necasi from Benin are also interesting. It turned out that the genetics identified the sampled animal as Chamaeleo gracilis. However, the specimen itself was not examined by the researchers. It could be a Chamaeleo gracilis misclassified by its appearance. In this case, the specimens used for the species description in 2007 would have to be viewed and sampled again in order to obtain more information about the actual species’ status.

In the course of the genetic investigations, the researchers found out that the origin of the genus Chamaeleo probably lies in South Africa. Chamaeleo namaquensis, the only terrestrial chameleon of the genus Chamaeleo, split off from the other Chamaeleo species as early as 40 million years ago in the Eocene. This makes the Namaqua chameleon from the Namib Desert and Damaraland the “oldest” chameleon of the genus Chamaeleo. Chamaeleo anchietae followed about 29 million years ago.

Out of southern Africa: origins and cryptic speciation in Chamaeleo, the most widespread chameleon genus
Devon C. Main, Bettine Jansen van Vuuren, Colin R. Tilbury & Krystal A. Tolley Conceptualisation
Molecular Phylogenetics and Evolution, Volume 175
DOI: 10.1016/j.ympev.2022.107578

Unexpected genetic diversity in leaf chameleons in western Madagascar

Unexpected genetic diversity in leaf chameleons in western Madagascar

by Alex Negro Science

Until now, it was thought that the earth chameleon Brookesia bonsi occurs exclusively in the Tsingy of Namoroka in western Madagascar. German and Malagasy researchers have now discovered that very close relatives of the species live a good 150 km further north, not far from the coastal town of Mahajanga. The earth chameleons from a forest near Antsanitia look more like Brookesia decaryi on the outside, but genetically they are more closely related to Brookesia bonsi. In contrast, the true Brookesia decaryi from Ankarafantsika, 80 km east of Mahajanga, seems to be exclusively restricted to this occurrence and not more widespread, as originally assumed. In the same studies, the scientists found that another population of leaf chameleons from the UNESCO World Heritage Site Tsingy de Bemaraha is also closely related to Brookesia bonsi. The leaf chameleons of the population found there had previously been assigned to Brookesia brygooi on a purely visual basis.

Further work is now necessary to clarify the exact genetic identity of Brookesia aff. bonsi. Are they separate species or merely locally isolated populations of Brookesia bonsi? One thing, however, is already certain: the habitat near Mahajanga should urgently be placed under protection. The leaf chameleons must be protected so that they can be studied further. According to current data, they could already be critically endangered (IUCN). And further research could still be very exciting!

New records of threatened leaf chameleons highlight unexpected genetic diversity of the Brookesia decaryi / B. bonsi species complex in western Madagascar
Frank Glaw, Njaratiana A. Raharinoro, Rojo N. Ravelojaona, David Prötzel und Miguel Vences
Der Zoologische Garten 90, 2022 (1)
DOI 10.53188/zg003

Influence of UV-B on growth

Influence of UV-B on growth

by Alex Negro Short messages Science

An interesting husbandry experience from the USA was presented in a short note in the Herpetological Review. Twelve carpet chameleon hatchlings (Furcifer lateralis) from the same clutch were divided into four groups of three animals each. During the first ten weeks after hatching, two groups were provided with a daily UV index of up to 3 for 12 h, the other two groups with a UV index of up to 7. Reptisun 5.0 was used to achieve the different UV indices. Measurements were taken with the Solarmeter 6.5. The chameleons were allowed to avoid UVI up to 0. After six, eight and ten weeks, the carpet chameleons were measured and weighed. It was noticed that in weeks 6 and 10, the groups with the lower UV index were up to 25% heavier than the comparison groups.

The two authors conclude that higher UV indices during rearing in the first weeks could lead to slower growth rates in carpet chameleons. This would correspond to the observation in nature that young animals “sunbathe” rather rarely and stay more hidden in the bushes. Due to the small group of test subjects and mixed groups instead of individual keeping, you must still be cautious with conclusions here. In addition, it is unfortunately still largely unexplored whether and how chameleons can regulate their vitamin D3 regulation in artificial light compared to natural sunlight. Nevertheless, it is a very interesting approach that is certainly worth pursuing.

Furcifer lateralis (carpet chameleon): Impact of Ultraviolet Light on growth
Michael J. Nash, Christopher V. Anderson
Herpetological Review 52 (2), 2022

New research on the Labord’s chameleon in Kirindy, Madagascar

New research on the Labord’s chameleon in Kirindy, Madagascar

by Alex Negro Science

Furcifer labordi is known as the world’s shortest-lived chameleon. Within three months, these animals grow from hatchling to adult chameleons, mate, lay eggs and mostly die immediately afterwards. Scientists at the University of Göttingen researched whether the short lifespan has an influence on the mating strategy of Furcifer labordi.

The study site was the dry forest of Kirindy in western Madagascar. Kirindy is located about 60 km north of the coastal town of Morondava and about 20 km from the sea in the Menabe region. During the rainy season in early 2020, 39 Furcifer labordi of both sexes were fitted with radio transmitters there. Weight and body length at the time of discovery as well as some other values were measured, and the sleeping height of the animals found at night was noted. The animals were released at the site where they were found. The researchers then tracked the chameleons twice during the day and once at night for several weeks using telemetry to record GPS data and establish movement and behaviour patterns.

The results of the study show that female Furcifer labordi in Kirindy are very site-faithful. They only cover short distances. In contrast, male Furcifer labordi move much more and over longer distances, so that seven to fourteen times more males than females could be observed in a forest section. The observed females mated with up to six different males – however, the researchers repeatedly found unmarked males among the observed females. This suggests that Furcifer labordi could actually have a significantly higher number of different reproductive partners. The individually very different body sizes of the males as well as differently pronounced nasal processes had no connection to movement patterns. Furthermore, it could be shown that Furcifer labordi does not occupy and defend territories. This means that presumably the short lifespan actually leads to competition for the few available females being more intense – and as observations show also more aggressive – than in other chameleon species. This study is the first investigation of the mating system of a Malagasy chameleon.

Sex-specific movement ecology of the shortest-lived tetrapod during the mating season
Lennart Hudel & Peter M. Kappeler

Published in Scientific Reports 12
Open Access (free download possible)
DOI https://doi.org/10.1038/s41598-022-14156-3