>Is anyone aware of any Phylogenetic work being done on the chromosomal
>relationship between Nepenthes and Sarracenia?
Chromosome nos. are:
_Sarracenia_ 2n=26, _Darlingtonia_ 2n=30, _Heliamphora_ 2n=42
_Nepenthes_ 2n=78
i.e. not very conclusive or suggesting close relationship. Well, if you
assume that _H._ is heptaploic (7x) and _N._ tricaedecaploic (13x), they
could share the basic no. of x=6. There is, however little reason to assume
such.
Genetical work has been performed mainly with the rbcL gene, showing that
Sarraceniaceae are close to Ericales (and apparently close to Roridulaceae)
but very distinct from an "extended caryophyllid clade" including
Droseraceae, Drosophyllaceae, Dioncophyllaceae, Ancistrocladaceae,
*Nepenthaceae*, Plumbaginaceae, Polygonaceae, Simmondsiaceae,
Frankeniaceae, and Tamaricaceae.
> I am trying to understand their evolutionary relationship (if there is one).
There does definitely not seem to be one besides the fact that both are
dicotyledons. The pitcher traps are morphologically very different and not
homologous. Sarraceniaceae do *not* contain plumbagin (Nepenthaceae and all
related families -the first 6 in the list above- do so). Chorologically,
the two families have virtually nothing in common. This means that
Sarraceniales in the traditional sense (including at least Nepenthaceae and
Sarraceniaceae) is very probably an artificial, polyphyletic assemblage.
BTW, according to rbcL analysis, the topology of the phylogenetical tree of
Sarraceniaceae is:
,---_Darlingtonia_
/
-< ,-_Sarracenia_
\ /
<
\
--_Heliamphora_
i.e. _Sarracenia_ is apparently closer to _H._ than to _D._.
Refs.:
Albert, V.A., Williams, S.E. & Chase, M.W. (1992) Carnivorous plants:
phylogeny and structural evolution, Science 257(5076):1491-1495
Cameron, K.M., Chase, M.W. & Swensen, S.M. (1995) Molecular evidence for
the relationships of _Triphyophyllum_ and _Ancistrocladus_,
Am.J.Bot.82(6):117-118
Kind regards
Jan