ABSTRACT Parasitic plant genus Cuscuta is important both economically and ecologically. This study is the result of more than fifteen years of herbarium and field studies in preparation for the floristic account of the genus in Nueva Flora de Chile. Eleven species that belong to three sections of subgenus Grammica were confirmed from Chile. Two historically reported species, C. epithymum and C. grandiflora, were not corroborated by the existing evidence. An identification key, typification, detailed descriptions and illustrations were provided to facilitate the identification of species, and their taxonomy was discussed, outlining remaining problems. Geographical distribution, ecology and host range of species were detailed. Results strongly suggested that several species are likely rare (e.g., C. andina, C. rustica, C. pauciflora) or even extinct (C. werdermannii), emphasizing the need for concerted efforts to locate these species in the wild and establish their conservation status.

RESUMEN El género de plantas parásitas Cuscuta es importante tanto desde el punto de vista económico como ecológico. Este estudio es el resultado de más de quince años de estudios de herbario y de campo en preparación del tratamiento del género en la Nueva Flora de Chile. Para Chile se confirmaron once especies pertenecientes a tres secciones del subgénero Grammica. Dos especies reportadas históricamente de la flora, C. epithymum y C. grandiflora, no fueron corroboradas por la evidencia existente. Se proporcionan, una clave de identificación, tipificaciones, descripciones detalladas e ilustraciones para facilitar la identificación de las especies, y se discutió la taxonomía, delineando los problemas restantes. Se detallaron la distribución geográfica, la ecología y la diversidad de huéspedes. Los resultados sugieren claramente que algunas especies son naturalmente escasas (raras) como, por ejemplo, C. andina, C. rustica, C. pauciflora o incluso ya están posiblemente extintas tal como C. werdermannii; esto subraya la necesidad de hacer esfuerzos concertados para localizar estas especies en la naturaleza y establecer su actual estado de conservación.

Resumo Plantas parasitas são frequentemente associadas a perdas agrícolas e silvo pastoris. Entretanto, elas são espécies chave na dinâmica dos ecossistemas. Os gêneros Cuscuta (Convolvulaceae) e Cassytha (Lauraceae) são ambos parasitas filiformes que têm evoluído em habitats similares, sendo a morfologia dos seus ramos notavelmente similar durante sua fase vegetativa. Devido ao fato de ambos os gêneros serem comuns nos trópicos, erros de identificação são frequentes, o que prejudica a compreensão de suas distribuições geográficas, biologia, e ecologia, bem como o desenvolvimento de medidas de controle ou práticas de manejo e conservação adequadas. Esse estudo oferece um detalhado guia de identificação para taxonomistas e cientistas agrários, usando ramos vegetativos e estruturas reprodutivas de representantes dos dois gêneros, tanto de coleções vivas como herborizadas. Estão incluídas uma chave de identificação, uma tabela comparativa, descrições detalhadas, fotografias e ilustrações como subsídio para as identificações. A atual prática de observação macroscópica dos ramos filiformes, na qual muitos profissionais se apoiam, mostra-se insuficiente para distinguir os dois gêneros. A análise micro morfológica dos ramos e/ ou das flores ou frutos é necessária para uma identificação conclusiva.

Abstract Parasitic plants are often associated with agricultural, forestry and grassland economic losses, but they are also keystone species in their natural ecosystems. Cuscuta (Convolvulaceae) and Cassytha (Lauraceae) are parasitic plants which have evolved similar stem habit and morphology, rendering them remarkably similar during the vegetative stage. Since both genera are common in the tropics, misidentifications are frequent, which is detrimental for understanding their geographical distribution, biology and ecology, as well as to the development of adequate control or conservation practices. We here present a practical identification guide for a clear and accurate distinction between Cuscuta and Cassytha, using stems and reproductive structures of both fresh plants and herbarium specimens, aimed at taxonomists and agricultural experts. An identification key, a comparative table, detailed descriptions and illustrations are included to facilitate genus recognition. The current practice of macroscopic observation of the filiform stems, on which many professionals rely, may not be enough to distinguish the two genera. The analysis of stem micromorphology, and/or of the flower or fruit morphology, are necessary for a conclusive identification.

Abstract The genome size varies widely among angiosperms but only a few clades present huge variation at a low phylogenetic level. Among diploid species of the genus Cuscuta the genome size increased enormously in at least two independent lineages: in species of subgenus Monogynella and in at least one species (C. indecora) of the subgenus Grammica. Curiously, the independent events lead to similar karyotypes, with 2n = 30 mostly metacentric chromosomes. In this paper we compared the patterns of heterochromatic bands and rDNA sites of C. indecora and C. monogyna, aiming to evaluate the role of these repetitive fractions in these karyotypes. We found out that the large genomes of these species were incremented by a huge number of small heterochromatic CMA+ and DAPI+ bands and 5S and 35 rDNA sites, most of them clearly colocalized with CMA+ bands. Silver nitrate impregnation revealed that the maximum number of nucleoli per nucleus was low in both species, suggesting that some of these sites may be inactive. Noteworthy, the tandem repeats did not generate large bands or sites but rather dozens of small blocks dispersed throughout the chromosomes, apparently contributing to conserve the original karyotype symmetry.