No abstract

No abstract

Little is known about the breeding systems of perennial Lupinus species. We provide information about the breeding system of the perennial yellow bush lupine, Lupinus arboreus, specifically determining self-compatibility, outcrossing rate, and level of inbreeding depression. Flowers are self-compatible, but autonomous self-fertilization rarely occurs; thus selfed seed are a product of facilitated selfing. Based on four isozyme loci from 34 maternal progeny arrays of seeds we estimated an outcrossing rate of 0.78. However, when we accounted for differential maturation of selfed seeds, the outcrossing rate at fertilization was lower, ∼0.64. Fitness and inbreeding depression of 11 selfed and outcrossed families were measured at four stages: seed maturation, seedling emergence, seedling survivorship, and growth at 12 wk. Cumulative inbreeding depression across all four life stages averaged 0.59, although variation existed between families for the magnitude of inbreeding depression. Inbreeding depression was not manifest uniformly across all four life stages. Outcrossed flowers produced twice as many seeds as selfed flowers, but the mean performance of selfed and outcrossed progeny was not different for emergence, seedling survivorship, and size at 12 wk. Counter to assumptions about this species, L. arboreus is both self-compatible and outcrosses ∼78% of the time.

Across large spatial scales, plants often exhibit genetically based differentiation in traits that allow adaptation to local sites. At smaller spatial scales, sharp boundaries between edaphic conditions also can create strong gradients in selection that counteract gene flow and result in local adaptation. Few studies, however, have examined the degree to which continuous populations of perennial plants exhibit genetically based differentiation in life‐history traits over small spatial scales. We quantified the degree of genetically based differentiation in adaptive traits among bush lupine (Lupinus arboreus) from nearby dune and grassland sites (sites separated by <0.75 km) that formed part of a larger continuous population of L. arboreus. We also investigated the spatial genetic structure of bush lupine by examining how genetic structure differed between seeds and juvenile plants that were less than two years old. We calculated F‐statistics from gel electrophoresis of 10 polymorphic loci. We then used these values to infer levels of gene flow. To examine differentiation in adaptive traits, we created full‐sibling/half‐sibling families of lupine within each area and established reciprocal common gardens at each site. Across two years, we measured canopy volume, flowering time, seed set, and mortality of progeny planted in each garden. Spatial genetic structure among seeds was virtually nonexistent (FST= 0.002), suggesting that gene flow between the three areas could be quite high. However, genetic structure increased 20‐fold among juvenile plants (FST= 0.041). We found strong evidence for fine‐scale genetically based differentiation and local adaptation in adaptive traits such as plant size, flowering phenology, fecundity, and mortality. Thus, it is likely that strong but differing selection regimes within each area drive spatial differentiation in lupine life‐history traits.

Variation in plant defensive profiles can be affected by environmental factors, genetic factors, and their interactions, and different feeding guilds may have different responses to variation in defenses. Here we present results of a factorial breeding design in Lupinus arboreus from three sites of origin to determine how parental effects, population differences, and environmental effects influence alkaloid profiles and resistance to multiple herbivores. Alkaloids were identified and quantified in seeds and adult plants grown at each of the three sites. We also censused five different herbivores on plants over 2 years and determined the relationship between each herbivore density and total alkaloids, alkaloid profiles, plant size and site. We found strong effects of origin, maternal parent, and maternal  paternal interactions on seed alkaloid profiles, and effects of origin, destination site, their interactions, and maternal  paternal interactions on leaf alkaloid profiles. However, there was no correlation between alkaloid concentration or specific compounds in seeds and full-sib adult plants. Density of the leaf galler Dasineura lupinorum and the fungus Colletotrichium spp. was affected by total alkaloid concentration and alkaloid profiles, while density of apical flies and bud gallers was not affected by any alkaloid measure. Red and green forms of the leaf galler had different responses to alkaloids, and green leaf gallers and fungi had opposite responses to measures of alkaloid profiles. These results highlight the complexity of interactions between herbivores and plant defenses, and indicate that measuring selection for defense traits may not be straightforward in natural environments that include multiple herbivore guilds. #