Intrapopulational chromosome number variation in Zephyranthes sylvatica Baker (Amaryllidaceae: Hippeastreae) from Northeast Brazil

Abstract

-(Intrapopulational chromosome number variation in Zephyranthes sylvatica Baker (Amaryllidaceae: Hippeastreae) from Northeast Brazil). Zephyranthes Herb. is a taxonomically complex and cytologically variable group, with about 65 species of Neotropical distribution. Chromosome number variability in 32 individuals of a Zephyranthes sylvatica population from Northeast Brazil was investigated. Three cytotypes were found: 2n = 12 (one metacentric, four submetacentric and one acrocentric pairs), in 24 individuals; 2n = 12 + 1B, in five and three individuals with 2n = 18, a triploid cytotype. All diploid individuals showed chromosomes with polymorphism in pair one and two, while in triploids this polymorphism was observed in all chromosome triplets, generally with two homomorphic chromosomes and a higher or lower heteromorphic chromosome. All individuals had reticulated interfasic nucleus and a slightly asymmetric chromosome complement, with one metacentric chromosome pair and the others more submetacentric to acrocentric. These data confirm the cytological variability previously registered for the genus. Mechanisms involved in karyotypic evolution in this population are discussed.Key words -Amaryllidaceae, B chromosomes, chromosome variability, triploid, Zephyranthes RESUMO -(Variação cromossômica numérica intrapopulacional em Zephyranthes sylvatica Baker (Amaryllidaceae: Hippeastreae) no Nordeste do Brasil). O gênero Zephyranthes Herb. é um grupo taxonômicamente complexo e cariologicamente variável, compreende cerca de 65 espécies de distribuição predominantemente neotropical. O presente trabalho aborda a variabilidade cariológica em um total de 32 indivíduos de Z. sylvatica obtidas em uma única população do Nordeste do Brasil. Todos os indivíduos apresentaram núcleo interfásico reticulado e complemento cromossômico bimodal, pela ocorrência de um par cromossômico metacêntrico e os demais submetacêntricos. Foram observados três citotipos: 2n = 12 (um par metacêntrico, quatro submetacêntricos e um acrocêntricos) em 24 indivíduos; 2n = 12 + 1B, em cinco, além de um citotipo triplóide com 2n = 18 em três indivíduos. Todos os citotipos diplóides exibiram polimorfismo cromossômico para os pares um e dois, enquanto nos triplóides esse mesmo polimorfismo foi observado nas trincas correspondente aos pares cromossômicos diplóides, geralmente com dois cromossomos homórficos e um cromossomo heteromórfico maior que os dois anteriores. Esses dados confirmam a variabilidade cariológica anteriormente registrada para o gênero. São discutidos os mecanismos de evolução cariotípica envolvidos nessa variabilidade.

Revision ofZephyranthes andina (Amaryllidaceae)including five new synonyms

“…The same numbers of x = 6 and 7, as well as 11 and 13 are recorded in many Habranthus species (Naranjo 1969). Chromosome polymorphisms, as well as numerical alterations, such as aneuploidy, disploidy and polyploidy and occurrence of supernumerary chromosomes were already reported by Felix & al. (2008) based on other authors as well as their detailed study of Z. sylvatica Baker in NE Brazil.…”

Intra- and interspecific karyotypic variations of the genus Senna Mill. (Fabaceae, Caesalpinioideae)

“…Additionally, polysomy and aneusomy (intra-individual variations in somatic chromosome numbers caused by polyploidy or aneuploidy respectively [Nirmala & Rao 1996;Rodrigues et al 2009]) have likely occurred in certain species of Senna (Chaulagain & Sakya 2002;Matos et al 2011), contributing to chromosome number variability in the genus. Intraspecific variations in chromosome numbers are quite common in other plant groups, such as Epidendrum secundum (Orchidaceae) (Assis et al 2013), Rutidosis leptorrhynchoides (Asteraceae) (Murray & Young 2001) and Zephyranthes sylvatica (Amaryllidaceae) (Felix et al 2008). In those cases, intraspecific variations could be related to factors such as distance or geographic isolation, together with hybridization in natural populations.…”

Karyotype variability in species of the genus Zephyranthes Herb. (Amaryllidaceae–Hippeastreae)

“…Species such as Z. candida with 2n = 38, 40, and 41 (Raina and Khoshoo 1971) and Zephyranthes selberti from Argentina with 2n = 10, 20, 30, and 40 (Daviña and Fernández 1989) exemplify this variability. Moreover, in several species, it is common to find chromosomal heteromorphisms in karyotypes resulting from structural changes (Raina and Khoshoo 1971;Felix et al 2008). The cytological variability in the genus has suggested the existence of three primary base numbers: x = 5, x = 6, and x = 7 (Naranjo 1974;Daviña and Fernández 1989).…”

“…The genus is represented in northeastern Brazil by a single species, Z. sylvatica, in addition to Habranthus bahiensis Ravenna and H. itaobinus Ravenna (Dutilh 2006;Oliveira 2006;Alves-Araújo et al 2007); these latter two are usually included in the generic limits of Zephyranthes (Dutilh, personal communication). No previous karyological records are known for H. bahiensis and H. itaobinus, while recently a karyotypic study was performed for Z. sylvatica, observing the occurrence of cytotypes with 2n = 12, 13, and 18 in a single population (Felix et al 2008).…”