Basic HTML Version
Full Abstracts – EVOLUTION AND QUANTITATIVE GENETICS II
167
130
The genetic architecture of hybrid inviability between Drosophila melanogaster and D. santomea.
Daniel R. Matute, Jerry Coyne. Ecology &
Evolution, Univ Chicago, Chicago, IL.
Postzygotic isolation causes reduced gene flow between species after the zygote gets formed, for instance by causing hybrid inviability or sterility. Hybrids
between species experience hybrid breakdown because the long-diverged genomes of their parents cause developmental problems when they come together
in a single individual. I have identified ten genes that cause hybrid inviability between two species of fruit flies, Drosophila melanogaster and D. santomea.
Interestingly, five of these genes are involved in early embryogenesis, a developmental process that is very similar in all Drosophila species. Additionally,
the majority of these genes (9 out of 10) have experienced episodes of accelerated evolution at some point in their phylogenetic history. These results
constitute evidence that hybrid incompatibility can evolve as a by-product of adaptive protein evolution, even in processes that have been thought to be
highly conserved.
131
Mutations in the
neverland
gene turned
Drosophila pachea
into an obligate specialist species.
Virginie Orgogozo
1
, Michael Lang
1
, Sophie Murat
1
,
Géraldine Gouppil
1
, Luciano Matzkin
3
, Catherine Blais
2
, Émilie Guittard
2
, Takuji Yoshiyama-Yanagawa
4,5
, Hiroshi Kataoka
5
, Ryusuke Niwa
4,6
, René
Lafont
2
, Chantal Dauphin-Villemant
2
. 1) Institut Jacques Monod, CNRS UMR7592, Paris, France; 2) UPMC, Univ Paris 06, Paris, France; 3) University of
California San Diego, Section of Ecology, Behavior and Evolution, La Jolla, CA; 4) Graduate School of Life and Environmental Sciences, University of
Tsukuba, Tennoudai, Japan; 5) Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan; 6)
Initiative for the Promotion of Young Scientists' Independent Research, University of Tsukuba, Tsukuba, Japan.
Most living species exploit a limited range of resources. However, little is known on how tight links build up during evolution between such specialist
species and their host. We have unraveled the genetic basis of the dependence of
Drosophila pachea
on its single host, the senita cactus
Lophocereus
schottii
.
D. pachea
has lost the capacity to transform cholesterol into 7-dehydrocholesterol (first reaction in the steroid hormone biosynthetic pathway,
catalyzed by the Neverland oxygenase) and requires uncommon plant sterols. We found that four amino acid changes in the Neverland protein have rendered
D. pachea
dependent on the sterols of its cactus host. This study illustrates how relatively few genetic changes in a single gene may restrict the ecological
niche of a species.
132
Seasonal variation in life history traits in two species of Drosophila.
Emily Behrman, Katherine OBrien, Paul Schmidt. University of Pennsylvania,
Philadelphia, PA.
Drosophila is used widely as a genetic model in evolutionary biology, yet there is little information regarding age structure and trait variation in wild
populations. Such information is critical in evaluating the basic evolutionary and population dynamics in this species. The rapid generation time of
Drosophila allow for both selection and demography to vary over seasons within years; previous work has documented cyclical, seasonal change in the
frequency of specific alleles and phenotypes associated with fitness. Here, the age structure in natural populations of both D. melanogaster and simulans is
examined at four distinct time points across the growing season. In addition, patterns of variation in basic life history traits for the sibling taxa are
investigated and partitioned into effects associated with seasonal change in environmental quality (e.g., phenotypic plasticity) and temporal change in the
genetic composition (e.g., response to environmentally mediated selection). The results show that age structure varies greatly across sampling intervals with
later collections exhibiting an increasing skew towards older age classes. The taxa have distinct age structure patterns with different trajectories; D.
melanogaster is present throughout the entire season while D. simulans is absent in the spring but grossly outnumbers D. melanogaster by the fall.
Development time and stress tolerance also vary with season, indicating pervasive genetic changes in the population composition over time. Overall, the data
demonstrate that wild Drosophila routinely survive to an age where senescence should be evident if not pronounced; age-specific performance is thus
predicted to have significant effects on organismal fitness, but selection on age-specific parameters would covary with observed temporal changes in the
underlying age structure of the population. The observed variance in age structure and life histories across seasonal time is predicted to have a significant
impact on the evolutionary dynamics of life histories and associated traits in natural populations of this genetic model.