Dudleya

Dudleya, commonly known as liveforevers, is a genus of rosette-forming succulent plants in the stonecrop family, Crassulaceae, consisting of about ~70 taxa found in southwestern North America and Guadalupe Island. The genus is very morphologically diverse, with species ranging from large evergreen plants to tiny deciduous geophytic plants. The flowers of Dudleya have parts numbered in fives, with the petals arranged in tubular, star-shaped, or bell-shaped forms and, when fruiting, are filled with tiny, crescent-shaped seeds.

The genus evolved as neoendemics, from ancestors in the stonecrop genus, Sedum. The ancestors probably radiated southward from Sedum during the creation of the dry summer climate, in the California region, five million years ago. Early botanists classified the larger species as Echeveria and Cotyledon, while the geophytic species were placed under Sedum. Taxonomic efforts, started by Joseph Nelson Rose and Nathaniel Lord Britton, created three genera, including Dudleya. These genera were all eventually subsumed into Dudleya proper with the work of Reid Moran. Phylogenetic research is still at an early stage in the genus, and is complicated by the fact that many species are becoming endangered and over-harvested (poached).

Dudleya is a relatively obscure genus, in comparison to other, more widely cultivated succulents; converging interests, by succulent collectors, native plant enthusiasts and gardeners alike, have led to the wider cultivation of many species as ornamental plants. In the wild, many species of Dudleya are vulnerable, as land development and poachers often threaten particularly niche populations of plants. Poached plants are often shipped to East Asia, especially South Korea, where hybridisation and cultivation of succulents is very popular. Conservationists, nurseries and governments combat Dudleya poaching through propagation programs and protection laws.

Description

Characteristics and subgenera

This genus is the only taxon of the Sedeae tribe to have evolved sympodial branching.

The genus is traditionally divided into three subgenera, two of which were formerly their own genera. The subgenera consist of Dudleya, Stylophyllum, and Hasseanthus.

Epicuticular wax

thumb|Dudleya brittonii, which has the highest ultraviolet reflectivity ever discovered in a plant.

One of the most famous features of some Dudleya is their waxy coating. Numerous species have their foliage covered in an epicuticular wax, or farina. This waxy coating is usually white, chalky, and mealy, and is the namesake in many epithets, like chalk dudleya, powdery liveforever, and giant chalk dudleya. The wax on the giant chalk dudleya is a surface with some of the highest ultraviolet reflectivity ever discovered in plants. When exposed to water, the wax may coat drops on leaves, preventing their evaporation. The farina is mostly composed of pentacyclic triterpenoids.

Other members, such as D. viscida and D. anomala, have a clear, sticky layer on their foliage. This adhesive layer ultimately helps the plant protect its leaves from the sun, much like ones with "white" wax. It accomplishes this solar protection by allowing dust to adhere to the sticky layer on the leaves, which coats the foliage with dust and debris, blocking solar radiation.

Taxonomy

Taxonomic history

Early history

The earliest species of the genus described was Cotyledon caespitosa, by Adrian Hardy Haworth in 1803, which would later be known as Dudleya caespitosa. The same species would later be described again as Sedum cotyledon by Joseph Franz von Jacquin in 1811, and in 1840 Thomas Nuttall described both Echeveria pulverulenta (Dudleya pulverulenta) and Echeveria lanceolata (Dudleya lanceolata). The differing generic placements of these early descriptions suggest that taxonomic disagreements over the genus had an early start, with some of these generic placements persisting even after the proper description of the genus by Britton and Rose.

In the 1930s, Alwin Berger revised the status of Dudleya and Stylophyllum into a sectional ranking within Echeveria, while merging the Hasseanthus genera into Sedum. This was in part due to a belief that Dudleya had evolved from Echeveria radiating northward from Mexico, evidenced by the similar tubular corollas, while Hasseanthus possessed aesthetic similarities to Sedum, primarily flowers with broadly spreading petals. Stylophyllum was believed to occupy a transitory position between Dudleya and Hasseanthus. These conclusions were widely accepted by botanists for the first half of the 20th century, until proper molecular and phylogenetic analyses began to appear.

Modern classifications and phylogenetic research

Around 1993, one of the only literary treatments of the genus was written, Paul H. Thomson's Dudleya and Hasseanthus Handbook.

Research in the 21st century has supported the hypothesis of Dudleya<nowiki/>'s relation to Sedum. Phylogenetic analysis has given weight to this hypothesis, concluding that Dudleya is much closer to North American members of Sedoideae than to Echeverioideae. The plant Sedum spathulifolium, which co-exists with Dudleya in Oregon and California, has been shown in multiple phylogenetic reconstructions to be a sister taxon to Dudleya, although it may not be the true sister taxon, as larger samplings are needed. Berger's hypothesis of a relationship between Hasseanthus and Sedum may still prove true, as in addition to morphological similarities, the Hasseanthus-type taxa could be basal to the genus. However, no truly conclusive evidence of significant divergence within Dudleya exists, and it remains unclear which groups are basal or derived.

Selected species

Dudleya abramsii
Dudleya abramsii subsp. abramsii – Abrams' liveforever
Dudleya abramsii subsp. affinis – San Bernardino Mountains liveforever
Dudleya abramsii subsp. bettinae – Betty's dudleya
Dudleya abramsii subsp. calcicola – limestone dudleya
Dudleya abramsii subsp. murina – Mouse-gray dudleya
Dudleya abramsii subsp. setchellii – Santa Clara Valley dudleya
Dudleya acuminata – Vizcaino liveforever
Dudleya albiflora– White-flower liveforever
Dudleya anomala – Todos Santos liveforever
Dudleya anthonyi – Anthony's liveforever
Dudleya attenuata – Orcutt's liveforever, tapertip liveforever
Dudleya arizonica – Arizona chalk dudleya. Formerly a subspecies of Dudleya pulverulenta.
Dudleya blochmaniae – Blochman's liveforever, Blochman's dudleya
Dudleya brevifolia – Short-leaved liveforever, short-leaved dudleya. Formerly a subspecies of D. blochmaniae.
Dudleya brittonii – Britton's dudleya, giant chalk dudleya
Dudleya caespitosa – Coast dudleya, sea lettuce, sand lettuce
Dudleya campanulata – Punta Banda liveforever
Dudleya candelabrum – Candleholder liveforever
Dudleya candida – Coronados liveforever
Dudleya cedrosensis
Dudleya crassifolia – Thick-leaf dudleya
Dudleya cultrata – Knife-leaved liveforever, maritime succulent liveforever
Dudleya cymosa – Canyon liveforever
Dudleya cymosa subsp. agourensis – Agoura Hills dudleya
Dudleya cymosa subsp. crebrifolia – San Gabriel River dudleya
Dudleya cymosa subsp. costatifolia – Pierpoint Springs dudleya
Dudleya cymosa subsp. cymosa – Coast Range dudleya
Dudleya cymosa subsp. marcescens – Marcescent dudleya
Dudleya cymosa. subsp. ovatifolia – Santa Monica Mountains dudleya
Dudleya cymosa subsp. paniculata – Diablo range dudleya
Dudleya cymosa subsp. pumila – Transverse ranges liveforever
Dudleya densiflora – San Gabriel Mountains liveforever
Dudleya edulis – Fingertips, lady fingers, San Diego dudleya
Dudleya farinosa – Bluff lettuce, powdery liveforever, powdery dudleya
Dudleya formosa – La Mision liveforever
Dudleya gatesii – Gates' liveforever
Dudleya gnoma – Munchkin dudleya
Dudleya greenei – Greene's dudleya
Dudleya guadalupensis – Guadalupe liveforever
Dudleya ingens – Baja liveforever, rock liveforever
Dudleya hendrixii – Hendrix's liveforever
Dudleya lanceolata – Lanceleaf liveforever.
Dudleya linearis – San Benito Island liveforever
Dudleya multicaulis – Many-stemmed dudleya
Dudleya nubigena – Cape liveforever
Dudleya nesiotica – Santa Cruz Island liveforever
Dudleya pachyphytum – Cedros Island dudleya
Dudleya palmeri – Palmer's liveforever
Dudleya parva – Conejo dudleya
Dudleya pauciflora– Few-flower liveforever
Dudleya pulverulenta – Chalk lettuce, chalk dudleya, chalk liveforever
Dudleya rigida – Sierra de la Laguna liveforever
Dudleya rigidiflora – Playa Maria liveforever
Dudleya rubens – Red flowering liveforever
Dudleya saxosa – Panamint liveforever
Dudleya saxosa subsp. collomiae – Gila County liveforever
Dudleya saxosa subsp. aloides – Desert liveforever
Dudleya saxosa subsp. saxosa – Panamint liveforever
Dudleya stolonifera – Laguna Beach liveforever
Dudleya traskiae – Santa Barbara Island liveforever
Dudleya variegata – Variegated liveforever
Dudleya verityi – Verity's liveforever
Dudleya virens – Alabaster plant, Island liveforever
Dudleya viridicata – Colonet liveforever
Dudleya viridis
Dudleya viscida – Sticky dudleya

Etymology

The genus is named after William Russel Dudley, the first head of the botany department at Stanford University.

The name of the subgenera Stylophyllum is an allusion to the pencil-shaped leaves of the type species, Stylophyllum edule, now known as Dudleya edulis.

Tiipai: milhka’mey (wide-leaf); milh kajmila (narrow-leaf)

The flower morphology of Dudleya also corresponds with the aforementioned groups of Hasseanthus, Stylophyllum, and Dudleya. The flowers in Hasseanthus and Stylophyllum are broad, white to yellow, and spreading, with bumblebees and bees as primary pollinators, and hummingbirds as occasional pollinators. As these species grade towards the subgenus Dudleya, the petals begin to fuse at the base, with the flowers becoming tubular and red, due to an association with hummingbird pollinators. This shift in pollinators corresponds to larger nectar volumes and higher energy contents in accordance with the demands of hummingbird pollinators.<gallery perrow="6" widths="225">

File:2017-06-17-14.05.23 ZS PMax Dudleya caespitosa-1 - Flickr - John Rusk.jpg|subg. ' — The flowers of Dudleya caespitosa

File:2017-08-19-13.55.44 ZS PMax Dudleya anthonyi—1—DxO (36281178490).jpg|subg. ' — The flowers of Dudleya anthonyi

File:Dudleyaedulis.jpg|subg. ' — The flowers of Dudleya edulis

File:Dudleya virens hassei.jpg|subg. ' — The flowers of Dudleya virens subsp. hassei

File:Dudleyablochmaniae.jpg|subg. ' — The flowers of Dudleya blochmaniae

File:Dudleya variegata 186339494.jpg|subg. ' - The flowers of Dudleya variegata

</gallery>

Distribution and habitat

Dudleya species are widespread and diverse in their range, but are typically found in rock outcroppings, cliff faces, or road cuts, where their leaves help them store water in a setting too dry for most types of plants. Most are small and inconspicuous when not in bloom. The diversity of species of Dudleya is centered in Southern California and northern Baja California. This allows accumulated water to drain from the nestlike center of the plant, thus preventing microbial decay. Dudleya should not be watered from directly above, as this may damage their chalky coating known as farina, which is present on numerous species.

Clay is preferable to plastic pots when growing the plants due to the advantages with water drainage. Plastic pots may also kill the plants by overheating the roots. Powdery mildew has also been recorded in cultivated Dudleya.

Shade

The amount of shade a species of Dudleya requires is dependent on the location. Plants growing in coastal regions may require little shade at all, whilst plants growing in the deserts, inland valleys and mountains will require shade. The majority of plants in the genus will appreciate north-facing sites and shade during the heat of the day. During the summer months, 50% shade may be beneficial for plants. If a cold-tolerant Dudleya is grown during a freeze or snow, it should be shaded as not to damage the plant, as a quick thaw may be detrimental.

Asexual reproduction

Vegetative reproduction may occur in multiple ways: Most Dudleya will not reproduce from leaves, with the leaves simply dying after being severed.

Conservation

Several species of Dudleya are threatened by urban development in Coastal California and Mexico, and anthropogenic-induced wildfires. However, one of the most critical threats to Dudleya species is poaching, partially caused by a demand from East Asian succulent collectors paying lucrative prices for certain Dudleya species.thumb|[[Dudleya farinosa, which was threatened by poachers]] The population of Verity's liveforever (Dudleya verityi), which was nearly wiped out during the 2013 Springs Fire, was targeted by poachers.

The Cedros Island liveforever (Dudleya pachyphytum) is a rare and extremely specialized Dudleya endemic to Cedros Island. In 2016, Korean nationals began moving to Bahia Tortugas, a locality in Baja California Sur, to facilitate the poaching and shipping of the plants. The species was seriously threatened after Mexican soldiers discovered poachers taking nearly 5,000 rosettes in a tractor-trailer. It was suspected the poachers rappelled onto the succulent's location via helicopter, as D. pachyphytum occupies a nearly inaccessible habitat. In 2019, the deaths and injuries of several fishermen from Bahía Tortugas who were on Cedros Island was allegedly the result of Dudleya trafficking, a conflict with the Sinaloa Cartel, or both. In 2020, the Mexican Navy in the Second Naval Region revealed that two fishermen were killed after a dispute emerged over the trafficking of the rare plant.

Bluff lettuce (Dudleya farinosa) was also targeted by poachers in numerous large-scale operations. Although not particularly rare, the size of the poaching operation pose a serious ecological threat. Starting in 2017, the U.S. Customs and Border Protection, along with the California Department of Fish and Wildlife, discovered large amounts of D. farinosa being shipped out of the country. South Korean and Chinese nationals have both been arrested in the smuggling of D. farinosa. According to nursery owners responsible for legally exporting Dudleya, buyers in Asia desired plants directly from the wild, owing to the aesthetic quality of their long caudices and weathered leaves.

The candleholder dudleya (Dudleya candelabrum), native to the northern Channel Islands, was reported to have been poached, with the thieves shipping plants to South Korea.

In response to the poaching of Dudleya, California State Assembly member Chris Ward proposed Bill AB-223, sponsored by the California Native Plant Society, which would make it illegal to poach Dudleya from state or private lands without a permit. The California Native Plant Society and conservationists have also initiated propagation programs to oversaturate the market as a means to deter poachers. On September 28, 2021, governor Gavin Newsom signed AB-223 into law.