RESUMO
Loasaceae subfam. Loasoideae are a nearly exclusively American plant group with a center of diversity in Peru. Numerous new taxa have been described over the past decades; one of the most striking discoveries was that of the narrowly endemic Xylopodia with the single species Xylopodiaklaprothioides in Peru, Dpto. Cajamarca in 1997. Surprisingly, field studies in the past years have resulted in the discovery of material clearly belonging to the same genus in both Bolivia and northern Argentina, approximately 1500 km SE of the next known population of Xylopodia in Contumazá, Peru. A closer examination shows that Argentinian and Bolivian material belongs to a single species, clearly different from Xylopodiaklaprothioides. We here describe Xylopodialaurensis and the entire genus is revised. Both species are illustrated, all aspects of their biology and ecology are portrayed and their threat status is discussed.
RESUMO
Spikelet structure and grouping are key characters to identify grasses. Here we tested the possibility that spikelet pairs, a distinctive morphological structure of many Andropogoneae and Paniceae, are the starting point for a secondary single spikelet condition that can also explain the change of spikelet orientation among Paniceae genera. As a first approach, we studied the inflorescence development of Paspalum simplex, P. stellatum, and Axonopus sufultus to clarify the origin of the spikelet orientation and other basic homologies. The results support that solitary spikelets of A. suffultus are homologous to the subsessile spikelets of P. simplex and that solitary spikelets of P. stellatum are homologous to the pedicellate spikelet of P. simplex. This last homology supports that spikelet orientation results from a differential reduction/abortion of either the pedicellate or the subsessile spikelet primordia. We also discuss the possibility that the RAMOSA and polar auxin pathways could play a role in the abortion of the lateral subsessile spikelets in P. stellatum. However, the apical meristem inhibition observed in A. suffultus and P. stellatum seems to depend on a very different genetic control, suggesting that the single spikelet condition is homoplasic within Paniceae and derived from at least two different genetic mechanisms.