Western North American Naturalist 80(1), © 2020, pp. 1–10 Self-compatibility in Lomatium dissectum (Apiaceae) and the diverse Andrena bees that dominate regional Lomatium pollinator faunas JAMES H. CANE1,*, MELISSA WEBER2, AND BYRON G. LOVE2 1Emeritus Research Entomologist, USDA Pollinating Insect Research Unit, Logan, UT 84341 2Biological Science Technician, USDA Pollinating Insect Research Unit, Logan UT 84341 ABSTRACT.—Species of biscuitroot (Lomatium: Apiaceae) are endemic to western North America, where multiple species can be common members of perennial wildflower communities from basin sagebrush-steppe and juniper woodlands up to alpine meadows. Despite Lomatium being the largest genus of Apiaceae in North America, little is known about its pollination needs or pollinators. Manual pollinations of the tiny flowers of one species, desert parsley (L. dissectum), showed it to be a self-compatible species, akin to other genera of Apiaceae. Seed production, however, largely requires pollinators to move pollen within and between the andromonoecious umbels. Regional sampling of floral visitors to L. andrusianum, L. dissectum, L. triternatum, and several other species revealed a sometimes abundant and exceptionally rich diversity of mostly Andrena bees. These 21 Andrena species together composed 94% of the indi- viduals methodically sampled at Lomatium plants; this number is at odds with claims of taxonomic promiscuity for pol- linator faunas of the Apiaceae. But for several Lomatium specialists, these Andrena species all seem to be floral gener- alists with apparent pollination value for Lomatium. These ground-nesting bees, as well as their Lomatium hosts, should survive the increasingly frequent and extensive wildfire events burning the sagebrush-steppe and juniper woodlands that they inhabit, owing to their springtime seasonalities and the insulative protection of overlying soil. RESUMEN.—Las especies de raíces biscuit o almidonosas (Lomatium: Apiaceae) son endémicas del oeste de América del Norte. Muchas de ellas pertenecen a comunidades de flores silvestres perennes provenientes de las estepas de artemisas, de los bosques de enebros de la cuenca y hasta de prados alpinos. A pesar de ser el género más grande de Apiaceae en América del Norte, es poco lo que se conoce sobre sus necesidades de polinización o sus polinizadores. Las polinizaciones manuales de las diminutas flores de una especie en particular, el perejil del desierto (L. dissectum), demostraron que se trata de una especie autocompatible, similar a otros géneros de Apiaceae. Sin embargo, para pro- ducir semillas, los polinizadores deben transferir el polen dentro y entre las inflorescencias andromonóicas. El muestreo local de los visitantes florales a las especies L. andrusianum, L. dissectum, L. triternatum y a otras especies reveló la diversidad abundante y excepcionalmente rica de abejas Andrena principalmente. Estas 21 especies de Andrena representaron el 94% de los especímenes metódicamente muestreados en Lomatium; número que no con- cuerda con las afirmaciones sobre la promiscuidad taxonómica de las faunas polinizadoras de las Apiaceae. Sin embargo, numerosos especialistas en Lomatium consideran a estas especies generalistas florales con claros valores de polinización para Lomatium. Dichas abejas que anidan en el suelo, así como sus hospederos Lomatium, deberían poder sobrevivir a la extensión y el aumento en la frecuencia de incendios forestales que afectan las estepas de artemisas y los bosques de enebros que habitan, dado sus estacionalidades de primavera y la protección aislante del suelo. The cosmopolitan family Apiaceae (or (dichogamy) and space (herkogamy) (reviewed Umbel liferae) consists of 3700 species, includ- in Koul et al. 1993). Umbels generally pre- ing many familiar vegetables (e.g., carrot, cel- sent a surface over which insects simply walk ery), herbs (e.g., parsley, dill), and spices (e.g., while they forage for the scant quantities of coriander, anise). Their generally numerous available pollen and nectar. Consequently, their and small flowers are white or yellow and are small, shallow flowers were traditionally con- borne in simple or complex umbels. Flowers of sidered to be promiscuous, owing to the sun - the Apiaceae are often andromonoecious, but dry generalist flies, bees, and beetles that visit species’ opportunities for autopollination can some species’ umbels (e.g., Grant 1949). How- be limited by separation of the sexes in time ever, several detailed field studies of wild *Corresponding author: [email protected] JHC orcid.org/0000-0002-4745-382X 1 2 WESTERN NORTH AMERICAN NATURALIST (2020), VOL. 80 NO. 1, PAGES 1–10 Apiaceae reported pollinator assemblages that sample the floral visitors at umbels of L. dissec- are more taxonomically restricted (reviewed tum, L. triternatum and, at a few sites, L. in Zych 2007). ambiguum (Nutt.) J.M. Coult. & Rose, L. andru- With 70+ species, Lomatium is the largest sianum McK. Stevens & Mansfield, L. grayi, genus of Apiaceae in North America. The and L. nudicaule (Pursh) J.M. Coult. & Rose. species in this genus are all perennial, herba- Taxonomy of the Lomatium species follows that ceous, and endemic to the West (Cronquist found in Cronquist (1997) and Stevens et al. 1997). Their common name “biscuitroot” refers (2018). Bee taxonomy follows the nomenclature to the large starchy taproots of some Loma - of LaBerge (1986 and references therein) and tium species (e.g., L. dissectum (Pursh) J.M. DiscoverLife (https://www.discoverlife.org/). Coult. & Rose) that were extensively roasted and consumed by native American tribes of METHODS the region, along with various species’ shoots, Field Study of Pollination flowers, or seeds (Moerman 2010). This species and others also feature in the diets of Greater In April 2005, a wild population of L. dis- Sage-Grouse chicks, a species of grave con- sectum was chosen for study along Right servation concern (Drut et al. 1994), as well as Hand Fork Canyon within the Bear River in the larval diets of those bees that collect Range 17 km northeast of Logan, Utah (41.78° N, Lomatium pollen and nectar. Various species 111.61° W; 1770 m elevation). Sixty available of the genus Lomatium are thus valued for budded umbels on as many plants were tagged their ecological, conservation, and/or tradi- and assigned 1 of 2 pollination treatments. tional dietary and medicinal traits. Half were merely tagged to allow unrestricted In early spring, species of Lomatium pre- pollinator visitation. The other 30 umbels served sent one or more compound umbels of tiny to evaluate the species’ capacity for autopolli- staminate or hermaphroditic yellow (or occa- nation by the method of enclosing each bud- sionally purple) flowers. The hermaphroditic ded umbel in a fine-mesh bag that was sup- flowers of some species are typically protogy- ported by a bamboo skewer for the duration nous (Schlessman 1982). Each bisexual flower of bloom. All resulting large green fruits were can yield 2 seeds. Among species of Apiaceae, harvested and counted. the crop species (e.g., carrot) have been the Experimental Pollination focus of most manipulative studies of breeding biologies (reviewed in Zych 2007); the thou- To establish a convenient plot of L. dissec- sands of wild species of Apiaceae have received tum for daily manual pollinations, 100 taproots scant attention, perhaps because of the physi- were excavated in November from a second cal challenges of manipulating and marking large population growing in Right Hand Fork the tiny flowers in their congested umbels. Canyon. At an outdoor research garden at Grown as a specialty seed crop, stands of L. the PIRU lab (USDA–ARS Pollinating Insect dissectum and L. grayi (J.M. Coult. & Rose) Research Unit, Logan, UT), these taproots have been readily established from seed. Indi- were transplanted on 1-m centers. The fol- viduals in cultivation begin flowering when lowing April, 25 transplants produced budded each is 3–4 years old; mature plants yield large umbels; the rest had either died or remained annual seed crops for many years (Shock et vegetative. Before flowering, the transplants al. 2009). Furthermore, their seed is easily were enclosed in walk-in field cages (7 × 7 × harvested and cleaned. Seed of widespread, 2 m) whose translucent fine mesh excluded all often common species, such as L. dissectum potential pollinators (Chicopee Lumite, Gaines - and L. triternatum (Nutt.) Mathias & Constance, ville, GA). should be useful to land managers rehabili- Caged plants were manually pollinated in tating postfire landscapes, particularly in the May to evaluate their breeding biologies. Two sagebrush-steppe of the Intermountain West pollination treatments were applied: geito nog - (Cane 2011). amy (transfer of self pollen) and xenogamy (out- The objectives of this study were twofold: crossing). Two bisexual umbels per plant were (1) to document the breeding biology of L. dis- selected, and within each, 3 randomly assigned sectum using experimental pollination treat- bisexual umbellets were tagged for manual pol- ments, and (2) to widely and methodically lination treatments. Stigmatic receptivity on an CANE ET AL. ♦ POLLINATION AND BEES OF LOMATIUM DISSECTUM 3 Fig. 1. Map of collection surveys for bees visiting 6 species of Lomatium across the U.S. Intermountain West. umbel was tested by immersing the pollen-free vidually clipped and returned to the laboratory. stigmatic tips of a few clipped test pistils in 3% Seeds produced by each umbel were counted. hydrogen