Abstract Detail



Sexual selection in flowering plants: traits, processes, and estimation

Johnston, Mark O. [1], Woolaver, Elizabeth [2], Kozela, Christopher [3].

Intersexual genetic conflict, genome size and reproductive isolation in Lobelia cardinalis, a wide-ranging taxon of the sky islands and beyond.

In polyandrous species with multiple offspring per brood, the maternal parent optimally invests equally in all offspring, while each father benefits from garnering higher resource provisioning for its offspring. The result is described by two hypotheses, either a tug-of-war between maternal and paternal genes, thought to be facilitated by genomic imprinting with paternal growth enhancers and maternal growth suppressors, or recognition avoidance of paternal conflict loci by maternal counterparts. These mechanisms co-evolve independently in different populations, so while conflict over resources is matched within populations, it may differ among populations. Differences in parental conflict levels are expected to affect hybrid offspring size due to mismatched levels of paternal growth enhancers and maternal suppressors. Here we study intersexual conflict in Lobelia cardinalis (Campanulaceae), a broadly distributed taxon ranging from eastern North America to the sky islands and other regions of southwestern United States, through Mexico and into Central America. Eastern and western populations are reproductively isolated because they are pollinated by different hummingbird species, and their status a single species has historically been controversial. We raised L. cardinalis specimens from eight populations (five eastern and three western) in a common garden and reciprocally crossed them to produce hybrid offspring. We measured seed size and germination rate in offspring as well as genome size in parents. Within-population crosses revealed no difference in seed size between east and west. In crosses between regions, however, seed size increased with eastern fathers and decreased with eastern mothers. These opposite effects in reciprocal crosses are consistent with greater intersexual conflict in eastern populations. Furthermore, among all populations, the magnitude of change to hybrid seed size increased with greater geographic distance between parental populations. This pattern is predicted when geographic separation reflects evolutionary distance and evolutionary arms races occur primarily within populations. Molecular markers revealed that some eastern and western populations are reproductively isolated, producing apomictic (asexual) seeds following manual pollination. Overall, these results suggest that intersexual conflict in offspring provisioning within populations can lead to reproductive isolation among populations.


Related Links:
Mark Johnston Lab Group


1 - Dalhousie University, Department Of Biology, 1355 Oxford Street, PO Box 15000, Halifax, NS, B3H 4R2, Canada
2 - Dalhousie University, Biology, 1355 Oxford Street, Halifax, NS, B3H 4R2, Canada
3 - Dalhousie University,, Biology, 1355 Oxford Street, Halifax, NS, B3H 4R2, Canada

Keywords:
Genetic conflict
Sky island
reproductive isolation
transposable elements
Genome size
Seed size
Endosperm
hybrid
Apomixis
Asexual reproduction
Lobelia.

Presentation Type: Colloquium Presentations
Number: 0009
Abstract ID:997
Candidate for Awards:None


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