Download Darwinian speciation in Amazon butterflies James Mallet Predictions

Darwinian speciation in Amazon butterflies
James Mallet
Predictions from classical geographic isolation ideas, in particular the "Pleistocene
refuge theory," are not fulfilled in heliconiine and ithomiine butterflies of the Amazon.
Instead, some lineages diversify rapidly, others slowly. This suggests a lineage's
ability to colonize new ecological niches is more important in diversification than
climatic forcing of the whole biota. I show how favourable local fluctuations in warning
colour and mimicry evolution can be amplified and spread to other locations. Spatial
spread behind moving hybrid zones, related to Phase III of Sewall Wright's "shifting
balance" theory, contributes to the diversification of Heliconius mimicry patterns.
Mimicry may also lead to the origin of species due to pleiotropic effects on mating
and hybrid fitness: these conditions are found in some Heliconius. Hybridization is
important among groups of closely related Heliconius species; adaptive variation may
be passed among species of Heliconius via occasional hybridization and backcrossing, and can lead to hybrid speciation. In conclusion, Amazonian butterflies
overturn a number of long-held ideas of how species originate.