Document: LYN-3-55-8

Maternal effects and heritability of host preference in a hemiparasitic plant.

ADLER, L.S.* and J.I.YODER

University of California, Davis, CA 95616 USA ¹

Abstract:
Generalist parasities may have fitness consequences from their choice of host. However, in order for host preference to evolve, parasites must possess the ability to discriminate between hosts and heritable variation for host preference. We conducted experiments to determine whether such variation exists in the hemiparasitic plant Triphysaria pusilla, which parasitizes a variety of hosts including grasses and the nitrogen-fixer Lupinus nanus. We collected seed from T. pusilla parasitizing lupines or other hosts, presumably grasses, in a coastal grassland. We then assayed maternal sibships for host preference using seedlings of L. nanus or the grass Bromus carinatus. Host preference was measured as number of haustoria initiated and time to initiation in a no-choice experiment. We found that in general, T. pusilla significantly preferred lupines to grass hosts, but that significant variation between families for host preference existed. In addition, T. pusilla whose maternal parent parasitized lupines showed a greater preference for lupines than T. pusilla whose maternal parent parasitized grasses. We also grew a generation of seed from the same field-collected sibships in a controlled environment without hosts, and assessed the host preference of their progeny. These offspring did not show a preference for lupines over grasses, suggesting that host preference is determined by maternal environment rather than genetics. Thus, some parasites may have a limited ability to evolve in response to selection pressure to parasitize specific hosts.

Keywords: hemiparasitic plants, host preference, heritable variation, _Triphysaria pusilla_, _Lupinus nanus_, _Bromus carinatus_, coastal grasslands, multispecies interactions

This abstract is being presented at: 11:15 AM in session:
Oral Session #61: Plant Responses to Nutrients.