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Judith Lowry's voice and experiences make a rich matrix for essays that include discussions of wildflower gardening, the ecology of native grasses, wildland seed-collecting, principles of natural design, and plant/animal interactions. This lyrical and articulate mix of the practical and the poetic combines personal story, wildland ecology, restoration gardening practices, and native plant horticulture.

Societal Impact Statement People plant, remove, and manage urban vegetation in cities for varying purposes and to varying extents. The direct manipulation of plants affects the benefits people receive from plants. In synthesizing several studies of urban biodiversity in Los Angeles, we find that cultivated plants differ from those in remnant natural areas. This highlights the importance of studying cultivated plants in cities, which is crucial for the design and planning of sustainable cities. Residents have created a new urban biome in Los Angeles, and this has consequences for associated organisms, ultimately resulting in a responsibility for society to determine what type of biome we wish to create. Summary Urbanization is a large driver of biodiversity globally. Within cities, urban trees, gardens, and residential yards contribute extensively to plant biodiversity, although the consequences and mechanisms of plant cultivation for biodiversity are uncertain. We used Los Angeles, California, USA as a case study for investigating plant diversity in cultivated areas. We synthesized datasets quantifying the diversity of urban trees, residential yards, and community gardens in Los Angeles, the availability of plants from nurseries, and residents’ attitudes about plant attributes. Cultivated plant diversity was drastically different from remnant natural areas; compared to remnant natural areas, cultivated areas contained more exotic species, more than double the number of plant species, and turnover in plant functional trait distributions. In cultivated areas, most plants were intentionally planted and dominated by exotic species planted for ornamental purposes. Most tree species sampled in Los Angeles were available for sale in local nurseries. Residents’ preferences for specific plant traits were correlated with the trait composition of the plant community, suggesting cultivated plant communities at least partially reflect resident preferences. Our findings demonstrate the importance of cultivated species in a diverse megacity that are driven in part through commercial distribution. The cultivation of plants in Los Angeles greatly increases regional plant biodiversity through changes in species composition and functional trait distributions. The pervasive presence of cultivated species likely has many consequences for residents and the ecosystem services they receive compared with unmanaged or remnant urban areas. People plant, remove, and manage urban vegetation in cities for varying purposes and to varying extents. The direct manipulation of plants affects the benefits people receive from plants. In synthesizing several studies of urban biodiversity in Los Angeles, we find that cultivated plants differ from those in remnant natural areas. This highlights the importance of studying cultivated plants in cities, which is crucial for the design and planning of sustainable cities. Residents have created a new urban biome in Los Angeles, and this has consequences for associated organisms, ultimately resulting in a responsibility for society to determine what type of biome we wish to create.

The olive fruit fly, Bactrocera oleae , is the main pest of the olive fruit and its expansion is exclusively restricted to the cultivation zone of the olive tree. Even though olive production has a century-old history in California, the olive fly was first detected in the Los Angeles area in 1998. Within 5 years of the first observation, the insect was reported from all olive cultivation areas of the state. Field-collected flies from five locations in California and another from Israel were analyzed on the basis of microsatellite polymorphisms in 10 microsatellite loci. These results were integrated with those of a previous study of olive fly populations around the European part of the Mediterranean basin. The analysis pointed to the eastern part of the Mediterranean as the putative source of the observed invasion. Moreover, samples from California were quite different from Mediterranean samples implying the participation of phenomena such as genetic drift during the invasion and expansion of the olive fly in California.

Reconstructing the introduction history of exotic species is critical to understanding ecological and evolutionary processes that underlie invasive spread and to designing strategies that prevent or manage invasions. The aims of this study were to infer the introduction history of the invasive apomictic bunchgrass Cortaderia jubata and to determine if molecular data support the postulated horticultural origin of invasive populations. Invaded areas in the USA (California, Maui) and New Zealand; native areas in Bolivia, Ecuador and Peru. We used nuclear microsatellite markers to genotype 281 plants from invaded areas in California, Maui and New Zealand, and 77 herbarium specimens from native South America, and compared the genotypic and clonal variation of C. jubata from the invaded and native ranges. Clonal diversity was determined from genotypic diversity using two analytical methods. Invasive C. jubata from invaded regions in California, Maui and New Zealand consisted of the same single clone that probably originated from a single introduced genotype. In contrast, 14 clones were detected in herbarium specimens from the native areas of Bolivia, Ecuador and Peru. The invasive clone matched the most common clone identified in herbarium specimens from southern Ecuador where horticultural stock is presumed to have originated. The lack of clonal and genotypic diversity in invasive plants, but moderately high diversity detected in native plants, indicates a significant reduction in genetic variation associated with the introduction of C. jubata outside of its native range. Based on historical accounts of the horticultural introduction of C. jubata and the results of this study, a severe founder effect probably occurred during deliberate introduction of C. jubata into cultivation. Our results are consistent with the postulated horticultural origin of invasive C. jubata and point to southern Ecuador as the geographical source of invasive populations.

1. Urban and agricultural activities are not part of natural disturbance regimes and may bear little resemblance to them. Such disturbances are common in densely populated semi-arid shrub communities of the south-western US, yet successional studies in these regions have been limited primarily to natural successional change and the impact of human-induced changes on natural disturbance regimes. Although these communities are resilient to recurrent and large-scale disturbance by fire, they are not necessarily well-adapted to recover from exotic disturbances. 2. This study investigated the effects of severe exotic disturbance (construction, heavy-vehicle activity, landfill operations, soil excavation and tillage) on shrub communities in southern California. These disturbances led to the conversion of indigenous shrublands to exotic annual communities with low native species richness. 3. Nearly 60% of the cover on disturbed sites consisted of exotic annual species, while undisturbed sites were primarily covered by native shrub species (68%). Annual species dominant on disturbed sites included Erodium botrys, Hypochaeris glabra, Bromus spp., Vulpia myuros and Avena spp. 4. The cover of native species remained low on disturbed sites even 71 years after initial exotic disturbance ceased. Native shrub seedlings were also very infrequent on disturbed sites, despite the presence of nearby seed sources. Only two native shrubs, Eriogonum fasciculatum and Baccharis sarothroides, colonized some disturbed sites in large numbers. 5. Although some disturbed sites had lower total soil nitrogen and percentage organic matter and higher pH than undisturbed sites, soil variables measured in this study were not sufficient to explain variations in species abundances on these sites. 6. Non-native annual communities observed in this study did not recover to a predisturbed state within typical successional time (< 25 years), supporting the hypothesis that altered stable states can occur if a community is pushed beyond its threshold of resilience.