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| Ovicula biradiata Manley, in Manley, Marck, Peralta, Castro, Wogan, Whiting et Powell, 2025. |
Abstract
Here, we describe and illustrate a new monospecific genus of Compositae, Ovicula biradiata gen. et sp. nov., from the Chihuahuan Desert in Big Bend National Park, Texas. Ovicula biradiata is a very locally abundant, yet range-limited, spring annual herb found in coarse calcareous alluvium. Based on its pistillate ray florets, pappus of hyaline, aristate scales, tomentose foliage and slightly saucer-shaped to flat, epaleate receptacle, we determine that the new species has affinities with the Helenioid subtribe Tetraneurinae in the Heliantheae alliance. Molecular phylogenetic analysis of nrDNA (ITS) sequence data supports the phylogenetic position of Ovicula biradiata within the subtribe Tetranuerinae, where it is resolved as the sister lineage to the genus Psilostrophe. We also present detailed habitat information, high-resolution images captured using a dissecting microscope and scanning electron micrographs of vegetative and reproductive characters of Ovicula biradiata and related taxa, as well as provide an updated key to the genera of Tetraneurinae. Finally, we discuss the significance of this remarkable discovery for community science, biodiversity exploration and plant conservation in the Chihuahuan Desert.
Key words: Asteraceae, biodiversity, calciphile, Chihuahuan Desert, Helenieae, taxonomy, Tetraneurinae
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| First photograph of Ovicula biradiata taken by Deb Manley on 2 March 2024. |
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| Researchers examining individuals in habitat. A Patty Manning scanning the ground in appropriate habitat for individuals of Ovicula biradiata B NPS botanist Carolyn Whiting photographing O. biradiata (circled in red). photos by Cathy Hoyt on 20 April 2024. |
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| Examples of moderately sized individuals found occasionally throughout the known locations. Photographs by Cathy Hoyt (A) & Deb Manley (B) on 2 March 2024 and James Bailey in April 2024 (C). |
Ovicula biradiata Manley, gen. et, sp. nov.
Etymology: The generic name from Latin Ovis “sheep” and -cula (diminutive ending) references the dense woolly indumentum of this new plant. The name honours the desert bighorn sheep (Ovis canadensis nelsonii), an iconic, but threatened desert animal that is currently rebounding in this part of the Chihuahuan Desert, providing hope for other rare species like O. biradiata. The specific epithet biradiata references the typically two conspicuous ray florets, occasionally three per head, positioned on opposing margins of the capitulum (Figs 1, 4). A recommended common name for O. biradiata is “woolly devil”, in reference to the woolly indumentum, the proximity of populations to the locality known as Devil’s Den and the tendency for the ray florets to resemble horns.
Debra L. Manley, Isaac H. Lichter Marck, Keily Peralta, Arturo Castro Castro, Kelsey A. Wogan, Carolyn V. Whiting and A. Michael Powell. 2025. Ovicula biradiata, A New Genus of Compositae from Big Bend National Park in Trans-Pecos Texas. PhytoKeys. 252: 141-162. DOI: doi.org/10.3897/phytokeys.252.137624
Resumen: Se ilustra y describe un nuevo género monoespecífico de Compositae, Ovicula biradiata gen. et sp. nov., del Desierto Chihuahuense en el Parque Nacional Big Bend, Texas. Ovicula biradiata es una hierba annual muy localmente abundante, pero con un rango limitado, florece en la primavera y se encuentra en aluviones calcáreos gruesos. Con base en sus flores pistiladas con corola radiada, vilano de escamas aristadas y hialinas, follaje tomentoso y receptáculo ligeramente en forma de platillo a plano y epaleado, determinamos que la nueva especie tiene afinidades con Helenieae subtribu Tetraneurinae, en la alianza Heliantheae. Análisis cladísticos moleculares de secuencias del ADN ribosomal nuclear (ITS) apoyan la posición filogenética de O. biradiata dentro de la subtribu Tetraneurinae, donde resulta el lineage hermano del género Psilostrophe. También presentamos información detallada sobre el hábitat, imágenes de alta resolución usando un microscopio de disección y micrografías electrónicas de barrido de caracteres vegetativos y reproductivos de O. biradiata y taxa relacionados, así como una clave actualizada para los géneros de Tetranuerinae. Finalmente, discutimos la significancia del descubrimiento en relación a la ciencia ciudadana, exploración de biodiversidad, y la conservación de plantas en el Desierto Chihuahuense.
Palabras clave: Asteraceae, biodiversidad, calcifilo, Desierto Chihuahuense, Helenieae, taxonomía, Tetraneurinae
