Cytological studies onPrimulinataxa (Gesneriaceae) from limestone karsts in Guangxi province, China

Abstract

Primulina, a large genus restricted mainly to limestone karst areas, was chosen as a suitable subject for the study of speciation patterns in its center of diversity and endemism at the chromosomal level. We investigated the chromosome numbers and chromosome morphology for 39 species, three varieties and 11 undescribed taxa of Primulina collected from limestone karsts in Guangxi province, China, half of which are known so far to be endemics. The chromosome numbers for the taxa examined were found to be highly constant, all being diploid with 2n = 36. The previously reported basic chromosome number x = 18 was confirmed, as were eight counts; the counts for the remaining taxa reported for the first time except for one gave different numbers from previously published counts. The chromosomes in Primulina are relatively small in size and slight variation occurs among taxa. One or two satellites were encountered in 18 taxa. The relative uniformity in chromosome numbers indicates that variation at the diploid level seems to be the principal feature of chromosomal evolution in this genus and it seems that polyploidization has played a minor role in the diversification and speciation of genus Primulina in limestone areas of SW China.

Adaptive and nonadaptive genome size evolution in Karst endemic flora of China

“…S2), which is consistent with that reported by Liu et al . (), but different from the report of Christie et al . (), suggesting intraspecific variation of ploidy levels in the species.…”

“…(), suggesting intraspecific variation of ploidy levels in the species. Our results confirmed that chromosome numbers in Primulina are uniform, as reported before (Christie et al ., ; Liu et al ., ). The flow cytometry analysis yielded high‐resolution histograms with coefficient of variance (CV) < 5% for the majority of measurements (Table S1).…”

“…Chromosome number was reported for 60 species of Primulina (11 were new and unpublished) in two recent studies. All the species examined were 2 n = 36 except Primulina longgangensis , which was either 2 n = 36 (Liu et al ., ) or 2 n = 72 (Christie et al ., ). Chromosome numbers for the other 66 species included in this study are, however, unknown.…”

Primulina melanofilamenta sp. nov. (Gesneriaceae) from Guangxi, China

“…Chromosomes of Primulina have been studied, measured and found to be small in size according to the classification of Lima‐de‐faria (), within the range 0.6–2.4 μm (Liu et al ). The somatic chromosomes of P. melanofilamenta at metaphase are illustrated in Fig.…”

Primulina cardaminifolia (Gesneriaceae), a rare new species from limestone areas in Guangxi, China

“…Although the new generic circumscription reflects better the evolutionary relationships and ecological preferences of the genus, diagnostic characters of Primulina , such as perennial habit and acaulescent rosette (2011) and the basic chromosome number, x = 18 (Christie et al 2012; Liu et al 2012), are not exclusive to the genus. The lack of strong morphological synapomorphies to distinguish it from related genera in the region necessitates molecular data in ascertaining generic placements (Xu et al 2012ab).…”