Lambert Sabrina Mota, Borba Eduardo Leite, Machado Marlon Câmara, Da Silva Andrade Sónia Cristina
Universidade Estadual de Feira de Santana, Departamento de Ciências Biológicas, Laboratório de Sistemática Molecular de Plantas, Rodovia BR 116, Km 03, Feira de Santana, Bahia, CEP 44.130-460, Brazil.
Ann Bot. 2006 Mar;97(3):389-403. doi: 10.1093/aob/mcj052. Epub 2006 Jan 19.
Melocacatus paucispinus (Cactaceae) is endemic to the state of Bahia, Brazil, and due to its rarity and desirability to collectors it has been considered threatened with extinction. This species is usually sympatric and inter-fertile with M. concinnus, and morphological evidence for hybridization between them is present in some populations. Levels of genetic and morphological variation and sub-structuring in populations of these species were assessed and an attempt was made to verify the occurrence of natural hybridization between them.
Genetic variability was surveyed using allozymes (12 loci) and morphological variability using multivariate morphometric analyses (17 vegetative characters) in ten populations of M. paucispinus and three of M. concinnus occurring in the Chapada Diamantina, Bahia.
Genetic variability was low in both species (P = 0.0-33.3, A = 1.0-1.6, H(e) = 0.000-0.123 in M. paucispinus; P = 0.0-25.0, A = 1.0-1.4, H(e) = 0.000-0.104 in M. concinnus). Deficit of heterozygotes within the populations was detected in both species, with high values of F(IS) (0.732 and 0.901 in M. paucispinus and M. concinnus, respectively). Evidence of hybridization was detected by the relative allele frequency in the two diaphorase loci. High levels of genetic (F(ST) = 0.504 in M. paucispinus and 0.349 in M. concinnus) and morphological (A = 0.20 in M. paucispinus and 0.17 in M. concinnus) structuring among populations were found.
The Melocactus spp. displayed levels of genetic variability lower than the values reported for other cactus species. The evidence indicates the occurrence of introgression in both species at two sites. The high F(ST) values cannot be explained by geographical substructuring, but are consistent with hybridization. Conversely, morphological differentiation in M. paucispinus, but not in M. concinnus, is probably due to isolation by distance.
少刺花座球（仙人掌科）是巴西巴伊亚州的特有物种，因其稀有性且受收藏家青睐，被视为有灭绝威胁。该物种通常与优美花座球同域分布且可杂交，在一些种群中存在它们之间杂交的形态学证据。评估了这些物种种群的遗传和形态变异水平以及亚结构，并试图验证它们之间自然杂交的发生情况。
在巴伊亚州钻石山的10个少刺花座球种群和3个优美花座球种群中，使用等位酶（12个位点）调查遗传变异性，使用多变量形态计量分析（17个营养性状）调查形态变异性。
两个物种的遗传变异性均较低（少刺花座球中P = 0.0 - 33.3，A = 1.0 - 1.6，H(e) = 0.000 - 0.123；优美花座球中P = 0.0 - 25.0，A = 1.0 - 1.4，H(e) = 0.000 - 0.104）。在两个物种的种群中均检测到杂合子缺失，F(IS)值较高（少刺花座球和优美花座球中分别为0.732和0.901）。通过两个心肌黄酶位点的相对等位基因频率检测到杂交证据。在种群之间发现了高水平的遗传（少刺花座球中F(ST) = 0.504，优美花座球中F(ST) = 0.349）和形态（少刺花座球中A = 0.20，优美花座球中A = 0.17）结构。
花座球属物种的遗传变异水平低于其他仙人掌物种报道的值。证据表明在两个地点的两个物种中都发生了渐渗。高F(ST)值不能用地理亚结构来解释，但与杂交一致。相反，少刺花座球的形态分化可能是由于距离隔离，而优美花座球并非如此。
