Presentation Detail

Speciation

Stathos, Angela [1], Fishman, Lila [2].

Chromosomal rearrangements and the genetics of speciation in Mimulus lewisii and M. cardinalis.

Chromosomal rearrangements distinguish most sister taxa and can promote speciation by directly reducing hybrid fitness,or by suppressing recombination among diverging populations. Theory predicts that rearrangements with strong fitness costs should be opposed by natural selection, yet rearrangements with this property appear common in plants and some animals. Alternatively, rearrangements that limit recombination may be selectively favored for their ability to lock together combinations of locally adapted alleles, and only secondarily become associated with hybrid incompatibilities. The latter scenario can explain both the evolution of rearrangements with some fitness costs, as well as divergence with gene flow. To investigate how chromosomal evolution influences speciation, I examine the geographical distribution, fitness effects, and genomic differentiation of rearrangements distinguishing two sister species of monkeyflowers. Mimulus lewisii and M. cardinalis are strongly isolated by pollinator preference, elevational adaptation, and genic incompatibilities. Major quantitative trait loci (QTLs) for species-specific adaptive traits and pollen sterility localize to several rearranged regions, which appear fixed between species. To determine whether hybrid sterility is caused directly by rearrangements or by linked genic incompatibilities, I generated synthetic tetraploids of M.lewisii-M. cardinalis F1 hybrids. High fertility in tetraploids suggests rearrangements themselves carry high fitness costs. Comparative linkage mapping further reveals that translocations in M. lewisii and M. cardinalis lineages, rather than inversions, are primarily responsible for reducing hybrid fitness. Preliminary data also hint at increased genomic divergence in rearranged regions, possibly indicating a greater build-up of species barriers in non-recombining regions. Together, these data support a role for rearrangements during speciation with gene flow, as both facilitators of adaptive differentiation and causes of reproductive isolation.

1 - University of Montana, Organismal Biology and Ecology, Division of Biological Sciences, 32 Campus Drive, HS 104, Missoula, MT, 59812, USA
2 - University of Montana, Division of Biological Sciences, Missoula, MT, 59812, USA

Keywords:
chromosomal rearrangements
Mimulus
translocations
Speciation
genomic divergence.

Presentation Type: Regular Oral Presentation
Session: 62
Location: Cotton C/Snowbird Center
Date: Sunday, June 23rd, 2013
Time: 11:15 AM
Number: 62004
Abstract ID:180
Candidate for Awards:W.D. Hamilton Award for Outstanding Student Presentation,Student Travel Awards from the ASN