Alkaloid parsimony

Ecological theory would predict that the natural products produced by plants and animals would be multifunctional so as to be maximally adaptive for the producers. This phenomenon, described as alkaloid parsimony, has been detected with some frequency in spite of the fact that more appropriate in vivo ecological studies utilizing realistic bioassays are still required. 

Alkaloid parsimony has also been detected in animals that produce alkaloids. Fire ants in the genus Solenopsis produce venoms dominated by novel 2,6-dialkylpiperidines that are delivered into vertebrates subcutaneously. The venoms constitute outstanding examples of alkaloid parsimony as they provide their ant producers with a diversity of deterrents. The alkaloids cause dermal necrosis in humans and are very algogenic in addition to being very lytic. The piperidines also perturb enzymatic pathways and block neuromuscular junctions. Fire ants have obviously adapted their piperidines to function as extreme exanples of alkaloid parsimony. 

Fig. 1.7 Evolution of alkaloids in the phylogeny of plants. Using nucleotide sequences of the chloroplast gene rbcL a phylogenetic tree was computed with Maximum Parsimony. A bootstrap cladogram is shown with bootstrap values shown at the nodes. Branches leading to taxa that accumulate alkaloids are shown in bold.

Gercideae. (a) The occurrence of alkaloids. Key to branches leading to families that accumulate quinolizidines, pyrrolizidines (No. 1 see arrows) Erythrina (No. 3) indolizidines (No. 4) p-carbolines (No. 5) or simple indoles (No. 2) are marked. The rbcl sequences used (1400 bp) derived from Kass and Wink, 1997a,b Wink and Mohamed (2003). Trees were reconstructed with maximum parsimony. 

Stepmatrix representing hypothesized interrelationships of 3-alkylpiperidine alkaloids used for a single multiple state PAUP 3.1.1. [87] parsimony analysis of Haplosclerida family relationships. Column numbers are the various molecule types depicted in Figure 3.11 (see Section 3). Their biogenetic transformation is postulated as unidirectional from molecule 1 to the various types described. Hypothetical precursors are molecules 0, 1,4, 7 and 15. The data in the columns represent numbers of steps between molecule types, i = "infinite", an artificial coding in PAUP for indicating irreversible steps. 

The Vinca alkaloids metabolism and transport in the producing plant cells and in the treated animal cells illustrate some interesting aspects of how evolution can be winding and parsimonious in the solutions it creates. 

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