Abstract Detail

Ecological factors that drive patterns of population genetic structure in plants

Nason, John [1].

Abiotic and Biotic Processes Underlying Cophylogeography in the Senita Cactus-Senita Moth Nursery Pollination Mutualism.

The spatial distribution of genetic variation within a species influences its potential for adaptive evolution and is itself a dynamic character reflecting a cumulative history of evolutionary change. The relative importance of geological and climatic factors on present-day distributions of plant and animal taxa has long been of interest, and features intrinsic to a species’ biology can also impact geographical patterns of genetic variation. Less well studied is the extent to which geographic patterns of intraspecific genetic structure are expected to covary between strongly interacting species. On the one hand, fundamental differences in the characteristics of symbionts (e.g., dispersal mechanism, longevity, and effective population size) may underlie large differences in genetic structure. On the other hand, the covariance in genetic structure may depend too on the nature of the interspecific interaction, being systematically higher for more intimate symbionts and for some forms of coevolution than others (e.g., mutualism vs. host-parasitism). Here we quantify the covariance in geographical genetic structure of two coevolving mutualists to determine the extent to which their genetic structures can be decomposed into effects attributable to extrinsic abiotic factors versus potential coevolutionary interactions. Specifically, we investigate the Sonoran Desert columnar cactus senita (Pachycerus schottii; Cactaceae) and its seed-eating pollinator, the senita moth (Upiga virescens; Pyralidae). Two features of this obligate, species-specific mutualism may act to strengthen the congruence of gene flow within these species: (1) migration in the pollen-bearing female moths are likely associated with pollen gene flow in the plant, and (2) range shifting in obligate pollination mutualisms must, by definition, occur concurrently in both symbionts. Genetic marker data reveals strong signals of vicariance and range expansion as well as highly restricted effective gene flow in the senita cactus, whereas we found very limited genetic differentiation and high rates of effective gene flow in the senita moth over the same geographic scales. A joint nuclear-mitochondrial analysis of the moths indicates that males are responsible for the high observed rate of gene flow, and that restricted dispersal of pollen-bearing female moths is consistent with the low effective gene flow observed in the host plant. Interestingly, despite myriad differences in life history characteristics and an order of magnitude difference in the degree of mean population differentiation (FST) between cactus and moth, the spatial pattern of differentiation plant and moth is significantly correlated.

1 - Iowa State University, Ecology, Evolution, And Organismal Biology, 251 Bessey Hall, Ames, IA, 50011, United States

senita cactus
senita moth
genetic structure.

Presentation Type: Colloquium Presentations
Number: 0013
Abstract ID:1065
Candidate for Awards:None

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