Do dwarf chameleons (<i>Bradypodion</i>) show developmental plasticity?

Miller, Ashadee K.; Alexander, Graham J.

doi:10.1080/15627020.2009.11407438

Cited by 9 publications

(5 citation statements)

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“…Asplund ; Fleming ), which might also be the case here. Moreover, each form reaches different absolute body sizes (da Silva & Tolley ), which is not a consequence of phenotypic plasticity, as demonstrated by a common garden experiment on B. thamnobates and B. melanocephalum (Miller & Alexander ). Accordingly, the differences in absolute performance are likely indicative of ecological differences between them.…”

Section: Discussionmentioning

confidence: 99%

Linking microhabitat structure, morphology and locomotor performance traits in a recent radiation of dwarf chameleons

et al. 2014

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Summary Evidence that morphological traits associated with particular environments are functionally adapted to those environments is a key component to determining the adaptive nature of radiations. Adaptation is often measured by testing how organisms perform in diverse habitats, with performance traits associated with locomotion thought to be among the most ecologically relevant. We therefore explored whether there are relationships between morphology, locomotor performance traits (sprint speed, forefoot and tail grip strength on broad and narrow dowels) and microhabitat use in five phenotypic forms of a recent radiation of dwarf chameleon – the Bradypodion melanocephalum–Bradypodion thamnobates species complex – to determine whether morphological differences previously identified between the forms are associated with functional adaptations to their respective habitats, which can be broadly categorized as open or closed‐canopy vegetation. The results showed significant differences in both absolute and relative performance values between the phenotypic forms. Absolute performance suggests there are two phenotypic groups – strong (B. thamnobates and Type B) and weak (B. melanocephalum and Types A and C). Relative performance differences highlighted the significance of forefoot grip strength among these chameleons, with the closed‐canopy forms (B. thamnobates, Types B and C) exceeding their open‐canopy counterparts (B. melanocephalum, Type A). Little to no differences were detected between forms with respect to sprint speed and tail strength. These results indicate that strong selection is acting upon forefoot grip strength and has resulted in morphological adaptations that enable each phenotypic form to conform with the demands of its habitat. This study provides evidence for the parallel evolution of forefoot grip strength among dwarf chameleons, consistent with the recognition of open and closed‐canopy ecomorphs within the genus Bradypodion.

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Section: Discussionmentioning

confidence: 99%

Linking microhabitat structure, morphology and locomotor performance traits in a recent radiation of dwarf chameleons

et al. 2014

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“…These two morphs relate strongly to habitat structure, and it is unlikely that phenotypic plasticity can be invoked as a parsimonious explanation, given that common garden experiments show no evidence for plasticity in this genus (Miller & Alexander, 2009). The most reasonable explanation is that phenotypic divergence is partly driven by habitat specific selection pressures (Tolley et al ., 2006, 2008; Cox & Calsbeek, 2010).…”

Section: Discussionmentioning

confidence: 99%

Morphological variation in the Cape Dwarf Chameleon (Bradypodion pumilum) as a consequence of spatially explicit habitat structure differences

Hopkins¹,

Tolley²

2011

Biological Journal of the Linnean Society

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An organism's phenotype is to some extent influenced by costs and benefits in terms of natural and sexual selection. The intensity of natural selection can in part be driven by habitat structure, which may result in varying levels of crypsis and/or selection on traits related to maximizing performance in that habitat. This may be countered by sexual selection, which can lead to sexual dimorphism in body size and/or the expression of conspicuous ornamentation relating to maximizing reproductive success. The intensity of these forces can also be different between the sexes, resulting in complex patterns of phenotypic variation. With this in mind, we examined morphological variation within the Cape Dwarf Chameleon, Bradypodion pumilum. The species inhabits two geographically disjunct habitat types and, in the present study, we demonstrate that chameleons from the two habitats show morphological differences. Large, conspicuous individuals inhabit closed vegetation, whereas small, drab individuals inhabit open vegetation. However, when morphological traits are size-adjusted, the open vegetation morph displays many traits that are larger for its body size than the closed vegetation morph, especially for characters related to locomotion (limbs) and bite force (head width). Sexual dimorphism is also present, although the degree and number of dimorphic characters was very different between the two morphs, with size-adjusted male-biased dimorphism much more pronounced in the closed morph. Overall, our findings suggest that natural selection in open habitats limits both body size and conspicuous characters, although sexual selection in closed habitats favours the development of ornamentation related to display.

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“…Under some species concepts, this lack of (or limited) genetic differentiation would call into question the validity of the two described chameleon species (de Queiroz, ), leading some to deduce that the complex is simply comprised of phenotypically plastic forms of a single species. This hypothesis was recently disproven using a common garden experiment, where juveniles from both described species were raised under identical conditions and developed phenotypes similar to their original populations (Miller & Alexander, ).…”

Section: Introductionmentioning

confidence: 99%

Ecomorphological variation and sexual dimorphism in a recent radiation of dwarf chameleons (Bradypodion)

Silva

Tolley

2013

Biol J Linn Soc Lond

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Natural selection tends to favour optimal phenotypes either through directional or stabilizing selection; however, phenotypic variation in natural populations is common and arises from a combination of biotic and abiotic interactions. In these instances, rare phenotypes may possess a fitness advantage over the more common phenotypes in particular environments, which can lead to adaptation and ecological speciation. A recently radiated clade of dwarf chameleons (Bradypodion) restricted to southern KwaZulu‐Natal Province, South Africa, is currently comprised of two species (Bradypodion melanocephalum and Bradypodion thamnobates), yet three other phenotypic forms exist, possibly indicating the clade is far more speciose. Very little genetic differentiation exists between these five phenotypic forms; however, all are allopatric in distribution, occupy different habitats and vary in overall size and coloration, which may indicate that these forms are adapting to their local environments and possibly undergoing ecological speciation. To test this, we collected morphometric and habitat data from each form and examined whether ecological relevant morphological differences exist between them that reflect their differential habitat use. Sexual dimorphism was detected in four of the five forms. Yet, the degree and number of dimorphic characters was different between them, with size‐adjusted male‐biased dimorphism being much more pronounced in B. thamnobates. Habitat differences also existed between sexes, with males occupying higher perches in more closed canopy (forested) habitats than females. Clear morphological distinctions were detected between four of the five forms, with the head explaining the vast majority of the variation. Chameleons occupying forested habitats tended to possess proportionally larger heads and feet but shorter limbs than those in open canopy habitats (i.e. grassland). These results show that this species complex of Bradypodion is morphologically variable for traits that are ecologically relevant for chameleons, and that the variation among the five phenotypic forms is associated with habitat type, suggesting that this species complex is in the early stages of ecological speciation. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109, 113–130.

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Do dwarf chameleons (Bradypodion) show developmental plasticity?

Cited by 9 publications

References 1 publication

Linking microhabitat structure, morphology and locomotor performance traits in a recent radiation of dwarf chameleons

Linking microhabitat structure, morphology and locomotor performance traits in a recent radiation of dwarf chameleons

Morphological variation in the Cape Dwarf Chameleon (Bradypodion pumilum) as a consequence of spatially explicit habitat structure differences

Ecomorphological variation and sexual dimorphism in a recent radiation of dwarf chameleons (Bradypodion)

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