Abstract

Phenotypic divergence and recent radiation in dwarf chameleons: Adaptation to habitat or widespread speciation?

Jessica M da Silva1,2, Krystal A Tolley1

1Applied Biodiversity Research Division, Kirstenbosch Research Centre, South African National Biodiversity Institute, Private Bag X7, Claremont 7735, Cape Town
2Department of Conservation Ecology & Entomology, Stellenbosch University, Private Bag X1, Matieland 7602, Stellenbosch

Dwarf chameleons (Bradypodion) are thought to have adaptively radiated into different habitats, but the mode of these radiations is not well understood. In the present study, we examined the correspondence between genetic and morphological variation in a clade of Bradypodion from KwaZulu-Natal Province, South Africa. The clade is comprised of two species – B. thamnobates and B. melanocephalum; however, additional lineages radiating from both have been suggested based on morphological and habitat differences, yet, to date, they are only recognized as ‘morphotypes’. We used a combination of morphometric (n=351, 20 measurements) and genetic data (n=279, 10 microsatellite loci & one mitochondrial marker) to examine the hypothesis that recent radiation into novel habitats is accompanied by morphological changes for ecologically relevant characters. Because the radiation is recent (Pleistocene), we expected a lack of genetic divergence at the species level. Multivariate analyses on the morphometric data identified four distinct morphotypes (B. melanocephalum, B. thamnobates, and Types A and B). B. melanocephalum was the smallest in all aspects, while B. thamnobates had the largest head, and Type B the largest body. Type A resembled B. melanocephalum, yet had much longer limbs. These morphological patterns correspond with those in other Bradypodion clades, reflecting macro-habitat differences – B. melanocephalum and Type A occur in grasslands; whereas B. thamnobates and Type B occur in forest fragments. Bayesian clustering on the microsatellite data identified seven clusters, with two corresponding to the morphological data (B. thamnobates, Type B).  Shared mitochondrial haplotypes between most populations indicate a lack of divergence typically expected at the species level, and this incomplete lineage sorting suggests that populations were formerly connected.  The discordance between morphology and genetics, and the strong morphological divergence present in this group of chameleons does not reflect widespread speciation, but indicates that chameleon morphology is highly labile and coupled to habitat.

Presentation Topic

Phenotypic divergence and recent radiation in dwarf chameleons: Adaptation to habitat or widespread speciation?

 

Contact Ms Da Silva:

Department of Conservation Ecology & Entomology, Stellenbosch University, Private Bag X1, Matieland

 

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