Figure 10.

The biodiversity cycle for Heliconius. This diagram summarizes the sequence, of events and processes which constitute a positive feedback loop generating both wing pattern and species diversity in Heliconius. The unique thing about the Heliconius system, as proposed in this chapter, is the creation of novel wing pattern variants when genes of the MCS "tool box" recombine by introgression in hybrid zones (Step I). Steps II-VII: co-occurring evolutionary processes of migration, drift, and selection, summarized here as "shifting balance" (II), which filter among available variants, geographical differentiation in allopatry or parapatry (III) which refines the genomic correlates of a newly established pattern (IV) and later the evolution of reproductive isolation (VI) which completes the prerequisites for packing into an existing community (V-VII) have been previously proposed with the assumption that mutation alone (indicated by the dotted line) produces step I. Major innovations in courtship and mating (e.g.. pupal mating) or in behaviors such as larval host preference, or in habitat preferences promote the evolution of niche differences (IV) as well as reproductive isolation (VI) and lead to local saturation in coexisting species and mimicry rings. This local genetic diversity is stored in local communities (VII) from which individuals occasionally disperse into hybrid zones to mate with and mix genes with those of individuals whose source populations had experienced a different history (VIII and IX). Not shown are factors which constrain local diversity (relevant to II-IV and VI-VII) such as micro habitat and host plant diversity and predator-imposed selection for Müllerian convergence. While the packing of species and wing patterns is limited locally, diversity builds among areas so that the cycle described continues to increase the overall biodiversity of the genus both with respect to taxonomic as well as phenotypic diversification. Bold squares enclose the major products of the processes described, from novel patterns in hybrid zones to their ultimate output: genus-wide biodiversity. See text for further discussion.