Juvenile
forms of plantae can sometimes be used to infer phylogenetic relationship
between species. This can be due to some reasons:
First of
all, juvenile forms are often very different from adult forms, so they provide
additional phenotypic materials for phylogenetic reconstruction;
I speculate
they can provide useful information due to two main reasons:
Ecological
niches where seedlings grow are often less variables than niches of adult
plants, i.e. in Lithops, they grow under particularly favourable conditions
(high humidity and low predatory pressure due to their very small size). Then
seedlings tend to be less subject to the action of natural selection than adult
forms, with respect to their shape, colour etc.;
In general,
juvenile stages (embryo stages in animals) tend to be highly conservative and
to reflect the phylogenetic path followed by their species. In plants also,
some of the most important and basilar
classifications criteria are based on the characteristics of seedlings, i.e.
monocotyledons and dicotoledons.
In Lithops,
seedlings differ highly in shape. Take a look, for example to the following
pic. It compare L. schwantesii v. marthae seedlings and L. fulviceps v. laevigata
seedlings (original Cole material). You can easily recognize the similarity between
them, despite the differences in the adult plants. Interestingly enough, DNA
analysis pointed out the fact that L. schwantesii and L. fulviceps are closely
related, belonging to the same Clade (called "E" in the original
work).
Gionata
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