Floral phenotype data from Mimulus parishii x M. cardinalis hybrids

Pollination syndromes are a key component of flowering plant
diversification, prompting questions about the architecture of single
traits and genetic coordination among traits. Here, we investigate the
genetics of extreme floral divergence between naturally hybridizing
monkeyflowers Mimulus parishii (self-pollinated) and M.
cardinalis (hummingbird-pollinated). We mapped quantitative trait loci
(QTLs) for 18 pigment, pollinator reward/handling, and dimensional traits
in parallel sets of F2 hybrids plus recombinant inbred lines and generated
nearly isogenic lines (NILs) for two dimensional traits, pistil length,
and corolla size. Our multi-population approach revealed a highly
polygenic basis (n = 190 QTLs total) for pollination syndrome divergence,
capturing minor QTLs even for pigment traits with leading major loci.
There was significant QTL overlap within pigment and dimensional
categories. Nectar volume QTLs clustered with those for floral dimensions,
suggesting a partially shared module. The NILs refined two pistil length
QTLs, only one of which has tightly correlated effects on other
dimensional traits. An overall polygenic architecture of floral divergence
is partially coordinated by genetic modules formed by linkage (pigments)
and likely pleiotropy (dimensions plus nectar). This work illuminates
pollinator syndrome diversification in a model radiation and generates a
robust framework for molecular and ecological genomics.