Tuesday, 19 May 2015

Caladium steudneriifolium

Leaf variegation is widespread in different genera of Araceae (Croat, 1994). Variegated leaves are characteristic of many species of Angiosperms, in particular among understorey herbs in tropical and temperate forests (Givnish 1990). The partial loss of photosynthetically active surface in variegated leaves affects absorption and utilization of light and, therefore, net photosynthesis, and as a consequence growth and reproduction (Soltau et al., 2009). The existence and relative success of variegated leaf colour forms within Caladium steudneriifolium populations, therefore, implies that there have to be particular selective pressures that support variegation despite the energetic handicap compared to plain leaves (Smith 1986).

Leaves of Caladium steudneriifolium. (a) Plain leaf. (b) Plain leaf with an infestation of leaf-mining moth larvae. (c) Variegated leaf. (d) Plain leaf painted with white correction fluid in a pattern mimicking the natural variegation. From Soltau et al. 2009.

In the case of Caladium steudneriifolium, the colour patterns are predicted to act as classical Batesian mimicry. Soltau et al. observed that the whitish areas of variegated leaves strongly resemble the leaf damages caused by the larvae of mining moths. This suggested that the colour patterns of the variegated leaves mimic these damages to escape oviposition by adult female moths. Among other chemical, tactile or visual cues, insects can visually detect and assess previous infestation during the process of host plant selection (Lev-Yadun and Inbar, 2002). Soltau’s study showed that in the presence of herbivores, leaf variegation can be of high selective advantage despite the loss of photosynthetically active leaf area compared to plain leaves (2009). As such, these plants provide a strong basis for the study of coevolution between plants and herbivores, and the mechanisms underlying predator-avoidance adaptations. 

Croat T 1994, “Taxonomic status of neotropical Aracea,” Aroideana, vol. 17, pp. 33–60.
Givnish TJ 1990, “Leaf mottling: relation to growth form and leaf phenology and possible role as camouflage,” Functional Ecology, vol. 4, pp. 463–474.
Lev-Yadun S and Inbar M 2002, “Defensive ant, aphid and caterpillar mimicry in plants,” Biologial Journal of the Linnean Society, vol. 77,pp. 393–398.
Smith AP 1986, “Ecology of a leaf color polymorphism in a tropical forest species: habitat segregation and herbivory,” Oecologia, vol. 69, pp. 283–287.
Soltau U, Dotterl S, and Liede-Schumann S 2009, “Leaf variegation in Caladium steudneriifolium (Araceae): a case of mimicry?” Evolutionary Ecology, vol. 23, pp. 503-512.

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