THE MECHANISMS AND CONSEQUENCES OF PHENOLOGICAL EVOLUTION
Abstract: Phenological shifts are clearly biologically important as they
contribute to both ecological speciation and persistence during global warming. However,
the genetic and physiological mechanisms behind shifts remain unclear. This is due to
complicated genetic and genomic bases, as well as the cryptic nature of the phenotype. The
consequences of phenological shifts also remain largely ... read moreunexplored. We expect that a novel
temporal habitat will have a different thermal profile than the ancestral habitat due to
seasonal thermal variation. Therefore, for successful phenological shifts we predict
correlated evolution in thermal tolerance. My dissertation investigates both the mechanisms
and evolutionary consequences of phenological shifts, and adds to a growing body of
literature on these topics. I first investigate the physiological mechanism underlying
evolution in life-history timing of corn borers. Using metabolic trajectories, I find that
variation in the length of the diapause termination phase underlies an ~30-day shift
observed in seasonal timing between E and Z-strains. While the E-strain exits diapause
within 7 days, the Z-strain remains in diapause termination for ~30 more days. These
metabolic trajectories are further used to target days for whole transcriptome profiling to
nominate molecular mechanisms for the shift in timing. I nominate 48 candidate genes within
the quantitative trait locus (QTL) for seasonal timing, and find that shorter E-strain
termination is defined by a burst of genome-wide transcriptional activity involved in cell
cycling, the stress response, and hormone production. I next interrogate the genomic
architecture surrounding the QTL for differences in seasonal timing. I investigate if a
chromosomal inversion could be present near the QTL for timing as previous studies found
evidence of a large region of suppressed recombination in this region. Our results confirm
that there is evidence for a large-scale rearrangement covering at least 20% of the Z (sex)
chromosome that harbors the basis for seasonal timing differences. A final study looks at
the consequences for evolved differences in seasonal timing between corn borer strains. As
shifts in phenology displace populations across a season, they also expose populations to
novel thermal environments. I find that earlier-emergence from winter diapause is
correlated with enhanced cold-tolerance.
Thesis (Ph.D.)--Tufts University, 2016.
Submitted to the Dept. of Biology.
Advisor: Erik Dopman.
Committee: Sean Mullen, Frances Chew, Philip Starks, and Colin Orians.
Keyword: Biology.read less
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