UV radiation is important for plant life as it induces essential processes such as growth, germination, and secondary metabolite pathways. However, prolonged exposure to UV-A and UV-B radiation can have negative effects on organisms. For example, UV radiation can directly or indirectly damage DNA molecules and cause enzyme denaturation. Sessile organisms have multiple mechanisms, such as the evolution of various UV-absorbent pigments, that protect them from the negative effects of constant UV radiation exposure. While liverworts are a group of plants commonly associated with mesic and shaded environments, there are multiple species within this group that inhabit dry and sunlight-exposed environments. For example, the complex thalloid liverwort Calasterella californica (Hampe ex Austin) D.G.Long & T.X.Zheng lives in exposed outcrops across California, where it is exposed to a great amount of solar radiation. During the dry season, C. californica thalli dehydrate and become surrounded by their large purple ventral scales. The plants remain in this “dormant” state until the subsequent wet season, when the thalli rehydrate. Since the purple-red pigmentation in plants is often associated with light-damage protection, we hypothesize that the purple scales of xerophytic liverworts—like C. californica—protect the particularly vulnerable desiccated thalli from potential damage associated with UV radiation. As a first step to test this idea, we document the sunlight absorbance spectrum of the purple scales of C. californica and compare it to the more-common, translucent liverwort scales and to commercial sunscreen. We found that purple scales absorb UV radiation in a pattern that matches that of sunscreen, particularly for UV-A and UV-B radiation. Both sunscreen and purple liverwort scales absorb two to three times more UV-A radiation than translucent scales. These results are consistent with the idea that purple scales play a role in protecting dormant xeric liverworts against UV damage. Although we focused on the scales of C. californica, there are other liverwort species (like Reboulia hemisphaerica (L.) Raddi and Targionia hypophylla L.) that have similar purple scales and rolling mechanism; this points to a relatively widespread adaptive mechanism used by distantly related liverworts that could allow them to thrive in dry regions.

The shift from fleshy to dry fruit in phylogenetic lineages is assumed to be an adaptation to climates in which plants experience dry, potentially stressful conditions during fruit maturation. Arctostaphylos Adans. (Ericaceae) is a good example of this, and the transition to dry fruit is accompanied by earlier flowering that permits earlier fruit development. Earlier flowering in Arctostaphylos is accomplished by dormant inflorescences produced the previous year. These dormant inflorescences, termed nascent inflorescences, are immature rachises and flower buds that develop at the end of the previous season's new stem growth, facilitating the earlier flowering and fruiting phenology. Recent work has shown that two other related genera in the Arbutoideae, Xylococcus Nutt. and Ornithostaphylos Small, share similar traits of earlier phenology in flowering and fruit production as well as dry fruit at maturity. The current study investigates whether Xylococcus and Ornithostaphylos also produce nascent inflorescences like Arctostaphylos. Nascent inflorescences are used as an important taxonomic character in Arctostaphylos, but there has been no discussion of their ecological role, and current hypotheses are provided for context. Field observations confirmed the presence of nascent inflorescences in the two sister Arbutoid genera, suggesting a larger ecological role as part of a reproductive trait syndrome.

Xylorhiza panamintensis B.G.Baldwin & M.Berger is described as a new species from carbonate bedrock exposures in the southern Cottonwood Mountains and adjacent Panamint Range west of Death Valley in the Mojave Desert of southeastern California. Unlike other species of Xylorhiza, X. panamintensis is a compact, densely leafy, glandular-hirsute to glandular-hirtellous shrub with leaves spinose-margined, ±ovate to mostly narrowly elliptic or oblanceolate, heads often in densely corymbiform capitulescences with involucres broadly obconic to campanulate, ≤2 cm diam, ray florets 19–29, ray corolla laminae 6–11.5 × 1–1.75 mm, 6.5–9.5 mm long, disk corollas narrowly cylindric to slightly funnelform, style branch appendages ca. as long as stigmatic lines, cypselae sericeous, and pappus bristles 15–25, the longest 5.5–10 mm long, white to tawny. Morphologically, X. panamintensis is not easily confused with other taxa of Xylorhiza. Comparison of nuclear ribosomal internal transcribed spacer (ITS) DNA sequences across the genus revealed diagnostic nucleotide states shared by all three representatives of the new species. Samples of the new species were resolved in ITS phylogenetic analyses as constituting a well-supported lineage most closely related to X. tortifolia sensu lato. Discovery of X. panamintensis reinforces evidence for floristic endemism in the Death Valley region and for evolutionary divergence of desert lineages in Xylorhiza. Although all known populations receive protection by occurring within Death Valley National Park, the small number of individuals found to date indicates that X. panamintensis warrants conservation concern as potentially vulnerable to climate change, to any local anthropogenic impacts to its limited habitat, or to stochastic events.

Bryum flabelliforme, a new facultative rheophytic moss, is described based on detailed morphological and molecular evidence. Examination of historical and recent specimens revealed that this moss has had a long history of confusion with several members of the Bryaceae that have rounded leaf apices. It has a broad distribution in North America, from California and Oregon eastward to Oklahoma and Kansas. A detailed description and photographs, known distribution, ecological data, and distinctions from similar-looking taxa are included. The unique rhizoidal tuber morphology of this species was previously unknown among North American bryaceous mosses. Splachnobryum valdiviae Müll.Hal. from temperate areas of the Southern Hemisphere was re-confirmed to belong to the Bryaceae rather than the Splachnobryaceae. This transfer to Bryum was corroborated by molecular data and subsequently formalized here.

Sobre la base de evidencia morfológica y molecular, se describe la nueva especie Bryum flabelliforme, un taxón reófito facultativo de Norteamérica. El estudio tanto de material histórico como de especímenes recientemente recolectados revelaron que este musgo ha sido reiteradamente confundido con varias otras especies de Bryaceae de hojas con ápices redondeados. Este taxón tiene una distribución amplia en Norteamérica, desde California y Oregon por el oeste hasta Oklahoma y Kansas por el este. Se presenta una detallada descripción de esta nueva especie, incluyendo fotografías, su distribución conocida, datos ecológicos, y se discuten sus diferencias con especies similares. La singular morfología de los tubérculos rizoidales de este taxón es única entre las Bryaceae de Norteamérica. Además, se confirma la posición del austral Splachnobryum valdiviae Müll.Hal. en la familia Bryaceae, ubicándose en el género Bryum. Este cambio sistemático ha sido corroborado por datos moleculares y es formalizado en la presente contribución.