The neotropical genus Calliandra is of great importance to ecology and agroforestry, but little is known about its nodulation or its rhizobia. The nodulation of several species from two restricted diversity centres with native/endemic species (Eastern Brazil and North-Central America) and species widespread in South America, as well as their nodule structure and the molecular characterization of their rhizobial symbionts based on phylogeny of the 16S rRNA, recA and nodC gene, is reported herein. Species representative of different regions were grown in Brazilian soil, their nodulation observed, and their symbionts characterized. Calliandra nodules have anatomy that is typical of mimosoid nodules regardless of the microsymbiont type. The rhizobial symbionts differed according to the geographical origin of the species, i.e. Alphaproteobacteria (Rhizobium) were the exclusive symbionts from North-Central America, Betaproteobacteria (Paraburkholderia) from Eastern Brazil, and a mixture of both nodulated the widespread species. The symbiont preferences of Calliandra species are the result of the host co-evolving with the “local” symbiotic bacteria that thrive in the different edaphoclimatic conditions, e.g. the acidic soils of NE Brazil are rich in acid-tolerant Paraburkholderia, whereas those of North-Central America are typically neutral-alkaline and harbour Rhizobium. It is hypothesized that the flexibility of widespread species in symbiont choice has assisted in their wider dispersal across the neotropics.

新热带马蹄莲属 对 生态学和农林业具有重要意义，但对其结瘤或根瘤菌知之甚少。来自两个受限多样性中心的几个物种的结瘤，包括本地/特有物种（巴西东部和中美洲北部）和南美洲广泛分布的物种，以及它们的根瘤结构和基于系统发育的根瘤菌共生体的分子特征本文报道了16S rRNA、recA和nodC基因。代表不同地区的物种在巴西土壤中生长，观察它们的结瘤，并表征它们的共生体。 卡利亚德拉 无论微共生体类型如何，结节的解剖结构都是含羞草样结节的典型解剖结构。根瘤菌共生体根据物种的地理起源而有所不同，即 Alphaproteobacteria ( Rhizobium ) 是来自北中美洲的独有共生体， Betaproteobacteria ( Paraburkholderia ) 来自巴西东部，两者的混合物使分布广泛的物种结瘤。Calliandra物种的共生偏好是 宿主与在不同土壤气候条件下茁壮成长的“本地”共生细菌共同进化的结果，例如巴西东北部的酸性土壤富含耐酸的 Paraburkholderia，而北部的那些中美洲通常是中性碱性和港口 根瘤菌。据推测，广泛物种在共生选择中的灵活性有助于它们在新热带地区更广泛地传播。