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| Croton guaritensis A.P.N.Pereira & Caruzo, in Pereira, Riina, Valduga et Caruzo, 2022. |
Abstract
Croton guaritensis, sp. nov. is here described, illustrated, and classified based on morphological and molecular data. The new species is restricted to the Pampa biome where it grows around rocky outcrops. Examination of the morphology from herbarium collections and field observations, as well as evidence from molecular analysis, indicate that Croton guaritensis belongs to Croton section Barhamia subsection Medea. Croton subsection Medea is represented by several rare and endemic species and stands out by its glandular structures in stipules, bracts, and sepals. The new species differs from other species of this subsection in the indumentum on branches and leaves, which consists of subentire lepidote trichomes, and in the sepals of staminate and pistillate flowers that have stipitate glands. An identification key to the new species and closely related taxa in southern Brazil is provided, as well as a preliminary conservation status.
Keywords: Croton sect. Barhamia subsect. Medea, Crotoneae, Neotropics, Southern Cone, Taxonomy
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| Croton guaritensis: d inflorescence with flower buds and two open flowers: the top one staminate and the lower one pistillate; e top view of a staminate flower; f side view of a staminate flower showing the stipitate, green glands along the sepal margins; g detail of a pistillate flower showing the tetrafid styles; h sepals of a pistillate flower showing the green stipitate glands on the outer surface; i young fruit with persistent, accrescent sepals; note that the marginal glands are more noticeably compared to the younger flower (see h); j verruculose seed with cream-colored caruncle. Scale bar: 1 mm. Photos by A.P.N. Pereira |
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| Croton guaritensis a a typical rocky outcrop of the Guaritas area; the new species grows on the slopes and tops of these outcrops (“cerros”); b subshrub habit; c branches showing yellowish fruits. Photos by A.P.N. Pereira |
Croton guaritensis A.P.N.Pereira & Caruzo, sp. nov.
Etymology: The specific epithet refers to the “Guaritas do Camaquã” rock formations in southern Brazil (see Fig. 2a), and is a reference to the type locality.
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| Comparison of morphology of pistillate and staminate flowers between Croton guaritensis and C. helichrysum: a pistillate flower of C. guaritensis showing entire sepals with conspicuous glands; b pistillate flower of C. helichrysum showing the serrate sepals with inconspicuous glands (on teeth apices); c staminate flower of C. guaritensis showing sepals with marginal glands; d staminate flower of C. helichrysum showing sepals without glands. Photos by A.P.N. Pereira |
Amanda da Paixão Noronha Pereira, Ricarda Riina, Eduardo Valduga and Maria Beatriz Rossi Caruzo. 2022. A New Species of Croton (Euphorbiaceae) endemic to the Brazilian Pampa and its Phylogenetic Affinities. Plant Systematics and Evolution. 308, 14. DOI: 10.1007/s00606-021-01803-x [18 March 2022]