Revision of Passiflora Subgenus Decaloba ... - Passion Flowers

149
Passiflora is not necessarily due to association by descent and that it is quite
possible that evolution of the Heliconiinae occurred after the diversificiation of the
Passifloraceae. Part of the controversy lies in the fact that butterfly taxa are
often recorded for more than one host species (often from other subgenera),
making the test for mutual descent complicated. Spencer (1988) published a
paper on the chemical mediation of coevolution of the interaction between
Passiflora and the Heliconiinae. He statistically established a significant positive
correlation between the proposed phylogenies of Passiflora subgenera and
species (as interpreted from Killip's 1938 revision of the Passifloraceae) and the
Heliconiinae (based upon Brown's proposed phylogeny of the Heliconiinae
published in 1981) at several taxonomic levels (Brown, 1981; Killip, 1938).
However, he also found that they were not wholly congruent. Based upon his
detailed analyses of cyanogenic compounds in Passiflora, he proposed that the
initial relationship of the Heliconiinae with Passiflora was exploitative and
facilitated by insect adaptation to an initially undiversified plant chemistry, with
adaptive radiation of plant chemistry. This was followed by plant speciation,
resulting from several centers of intense herbivore pressure. However, despite
these detailed studies, the extent and nature of mutual descent in this system still
remain largely unknown, as well-supported phylogenies of the Passifloraceae
and Heliconiinae have not yet been proposed. Nevertheless, many
entomologists and botanists are currently accumulating morphological and
molecular data for cladistic analysis and this controversy will hopefully be
resolved in the coming years. Penz (1999) recently published a higher level