Species diversification in chameleons

Species diversification in chameleons

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

Neue Art der Gattung Kinyongia beschrieben

General topics

Aus dem Magombera Forest im Udzungwa Mountains National Park, süd-zentral Tansania, wird eine neue Chamäleonart,  Kinyongia magomberae sp. nov. (das Magombera Chamäleon), beschrieben.
Das neue Chamäleon ist K. tenuis und dem weiterverbreiteten, im Eastern Arc endemischen K. oxyrhina, durch seinen einzelnen rostralen Anhang ähnlich.
Es kann jedoch durch den kürzeren rostralen Anhang und das Fehlen einer beweglichen Spitze von diesen beiden Arten unterschieden werden.
K. magomberae sp. nov. ist, nur von zwei Orten bekannt, dem flachen und ungeschützten Magombera Forest und dem sub-montanen Mwanihana Forest innerhalb des Udzungwa Mountains National Park.

Quelle:
Michele Menegon, Krystal Tolley, Trevor Jones, Francesco Rovero, Andrew R. Marshall & Colin R. Tilbury (2009):
A new species of chameleon (Sauria: Chamaeleonidae: Kinyongia) from the Magombera forest and the Udzungwa Mountains National Park, Tanzania.
African Journal of Herpetology, 2009 58(2): 59-70

Neue Art der Gattung Kinyongia beschrieben

General topics

Kinyongia vanheygeni (NECAS, 2009)

Die 2002 erstmals von NAGY in den Tansanianischen Poroto-
Bergen entdeckte „neue“ Chamäleonart wurde jetzt von Petr NECAS anhand von Fotos (VAN HEYGEN, 2008) und einem toten Tier beschrieben und in die Gattung Kinyongia gestellt.

Kinyongia vanheygeni erreicht eine Gesamtlänge von nur etwa 15 cm und trägt einen Rostralfortsatz mit zwei parallel verlaufenden Längsreihen aus je drei vergrößerten Schuppen. Auffällig ist der hoch aufragende nach hinten und oben gewölbte Helm.
Die Tiere sind farblich unauffällig in Gelb- Braun- Grau- und Grüntönen gefärbt.

Bisher wurde nur ein männliches Tier lebend gefunden und fotografiert. – Eine ausführliche Beschreibung folgt in einer der nächsten Ausgaben der Chamaeleo.

Quelle: Ein neues Chamäleon der Gattung Kinyongia Tilbury, Tolley & Branch 2006 aus den Poroto-Bergen, Süd-Tansania (Reptilia: Sauria: Chamaeleonidae)