Carnivorous wasps of the family Vespidae are known to seek out and disperse the diaspores of at least two North American and two Asian plant species. Attraction of the wasps to the diaspores is likely due to the release of volatile compounds that signal availability of an eliaiosome rich in protein and fat, which the wasps remove before releasing the diaspore. It is thought that this interaction between carnivorous wasps and plants is rare, occurring in just a few plant species. Here, we present our findings on dispersal of spicebush (Calycanthus occidentalis Hook. & Arn.) achenes by carnivorous wasps of the genus Vespula. Observations and experiments were performed with the goals of discovering: how geographically widespread this interaction is; what the reward system is, if any; and, how wasps detect the achenes. Eight populations of C. occidentalis in northern California were used to observe wasps and plants, and to perform experiments on wasp attraction to the achenes. In all examined populations, workers of western yellowjacket (Vespula pensylvanica [de Saussure, 1857]) were observed entering mature Calycanthus receptacles, removing achenes, taking flight with them, and successfully transporting achenes through the air. Receptacles were found to open upward at an average angle of 45° (SD = 29°), preventing the achenes from falling to the ground when mature. No animals other than wasps were observed visiting the receptacles during the observations. Experiments suggest that wasps are attracted to an elaiosome-like organ of the achene. Nutritional analysis shows that this organ is high in fat and protein. Further experiments using solvent extracts of the achenes suggest that the attraction is likely mediated by volatile compounds.

Arbutus xalapensis Kunth (Texas madrone, Ericaceae) is found in western and central Texas, but its ecological characteristics are little known. Mature A. xalapensis plants were found in the Albert and Bessie Kronkosky State Natural Area in Kendall and Bandera counties, central Texas (29.740278 N, –98.838333 W). Habitats studied included Acer grandidentatum Nutt. (bigtooth maple) canyon bottoms, Juniperus ashei J.Buchholz/Quercus L. sp. (Ashe juniper/mixed oak) hillsides, and J. ashei uplands. Population characteristics were compared to habitat and surface geology. A total of 98 A. xalapensis plants were found in the communities studied. Differences were found for all parameters except height. Upland A. xalapensis trees had the lowest mean (±SD) density (2 ± 3 plants/ha), highest basal area (210 ± 190 cm²/plant), community elevation (573 ± 14 m) and height (4.09 ± 1.70 m/plant). Hillside communities had the highest density (61 ± 38 plants/ha), but lower basal area (110 ± 170 cm²/plant). The canyon bottom plant basal area was 80 ± 100 cm²/plant and density was 10 ± 5 plants/ha. The canyon bottoms had the deepest soil (27.2 ± 20.4 cm) and lowest elevation (510 ± 16 m). When geological substrates were examined, 128 additional plants were found. The largest plants were on the Fort Terrett member of the Edwards limestone (hard limestone, 230 ± 220 cm²/plant), but density was the lowest (2 ± 3 plants/ha). Whereas greater density was on the Upper Glen Rose limestone (softer limestone, 16 ± 7 plants/ha), where plants were smaller (110 ± 150 cm²/plant). Community type and geological substrate seem critical for growth of this species.

In our search to document the fruits of Chenopodium L. taxa in North America to assist identifications, and after demonstrating fruits to be stable and diagnostic, we here focus on the some of the “narrow-leaved” group taxa prevalent in the western part of the continent. For this study, we sampled and classified, employing fruit characters as the leading criteria for categorization, more than 500 herbarium collections of Chenopodium of western North America, with a special focus on California. We concentrated only on taxa with fruits with adherent pericarp and lanceolate to lance-ovate, entire, un-lobed, or basally lobed leaves. Here, we recommend the recognition anew of C. incognitum Wahl as a separate species from C. hians Standley and 10 new species of Chenopodium in California and nearby states of western North America. The recognition of these taxa contributes to an ongoing study of the taxonomy of native Chenopodium in California, where an in-depth local taxonomic treatment of the genus has never before been presented. Our classification is supported both by biogeographical distribution and morphological characters. Taxonomic keys are provided.

The name Cylindropuntia wolfii, which has been used for a distinct cholla species, has had a problematic nomenclatural history. An attempt is made to clarify the validity of the name and to provide a revised description of the species and its presently-known distribution.

Some reports of Sonchus tenerrimus L. for North America north of Mexico, notably from Alabama and California, are based on misidentified specimens of S. oleraceus L.