Genetic diversity of Bemisia tabaci cryptic species in Nigeria and their relationships with endosymbionts and acquired begomoviruses

Bemisia tabaci is a species complex of at least 44 cryptic species with a worldwide distribution. It is a serious pest of many crop plants as well as a successful vector of at least 100 begomoviruses. Using B. tabaci collected from cassava and tomato fields in the southwestern and north central regions of Nigeria, we determined nucleotide sequences from the mitochondrial cytochrome c oxidase subunit I (COI) of 23 B. tabaci samples, the 16S and 23S ribosomal DNA of endosymbionts, and the coat protein gene of geminiviruses ingested by the whiteflies. The COI analysis identified three different genetic groups including the indigenous Sub-Saharan Africa 1 subgroup 1 (SSA1-SG1) and 5 (SSA1-SG5, which was most prevalent), and an invasive cryptic species (Mediterranean). SSA1 was infected by five known secondary endosymbionts, Arsenophonus, Cardinium, Hamiltonella, Rickettsia, and Wolbachia, and co-infections with two or three endosymbionts were common. Five begomoviruses, okra enation leaf curl virus, squash leaf curl China virus, tobacco curly shoot virus, tomato leaf curl New Delhi virus, and tomato yellow leaf curl virus, were detected from 43.5% of the B. tabaci samples. However, cassava mosaic disease that causes devastating cassava yield losses was not detected in this study. This study improves the current understanding of the genetic diversity of B. tabaci cryptic species, and it reveals their relationships with endosymbionts and geminiviruses in the cassava and tomato fields of Nigeria.     

Genetic diversity and geographic distribution of Bemisia tabaci and Trialeurodes vaporariorum in Costa Rica

The tobacco whitefly Bemisia tabaci (Gennadius) cryptic species complex and of the greenhouse whitefly Trialeurodes vaporariorum (Westwood) are extensively reported as destructive pests in vegetable crops worldwide. A survey was conducted in 2011 and 2012 to determine the occurrence and genetic diversity present in the populations of these whiteflies in the major vegetable production areas of Costa Rica. Insect samples were collected from sweet pepper (Capsicum annuum L.), tomato (Solanum lycopersicum L.), common bean (Phaseolus vulgaris L.) and weeds present in commercial crops either in open field or greenhouse conditions. PCR‐RFLP analysis of mitochondrial cytochrome c oxidase subunit 1 gene (mtCOI) sequences of 621 whitefly individuals confirmed the presence of the Mediterranean (MED) type of the B. tabaci and of T. vaporariorum in most sampled regions. Also, individuals of the Middle East‐Asia Minor 1 (MEAM1) type of the B. tabaci were observed in low numbers. Contingency analyses based on type of crop, geographical region, whitefly species, year of collection and production system confirmed that T. vaporariorum was the most frequent species in vegetable production areas in Costa Rica, both in greenhouses and in open fields. B. tabaci MED is likely spreading to new areas of the country, whereas B. tabaci MEAM1 was mostly absent or rarely found. Comparisons of mtCOI sequences from B. tabaci individuals revealed the presence of four B. tabaci sequence haplotypes (named MED‐i, MED‐ii, MEAM1‐i, MEAM1‐xviii) in Costa Rica, three of them identical to B. tabaci haplotypes previously reported in the Western Hemisphere and other parts of the world. Analysis of sequences of T. vaporariorum individuals revealed a more complex population with the presence of 11 haplotypes, two of which were identical to T. vaporariorum sequences reported from other countries.     

Spatial and host-plant partitioning between coexisting Bemisia tabaci cryptic species in Tunisia

The whitefly Bemisia tabaci is a species complex including at least 24 morphologically indistinguishable species among which the Mediterranean (Med) and Middle East-Asia Minor I (MEAMI) species containing the biotypes commonly known as Q and B, respectively. These B and Q biotypes (hereafter referred to as MEAMI and Med species) are the most invasive agricultural pests of the B. tabaci complex worldwide. The spread of MEAMI and more recently of Med species into regions already invaded by other B. tabaci populations has been frequently seen to lead to their displacement by Med species. In Tunisia, in contrast to usual observations in the Mediterranean basin, Med and MEAMI species have been seen to co-occur in the main crop producing regions. Based on fine population genetics and field spatial distribution analyses, we found that the co-existence of these two interacting species was based on habitat partitioning including spatial and host-plant partitioning. Although they co-occurred at larger spatial scales, they excluded one another at sample scale. We observed neither spatial overlapping nor hybridization between MEAMI and Med B. tabaci. Vegetable crops were the main hosts for MEAMI specimens while 99.1% of the B. tabaci collected on the ornamental, Lantana camara, were Med specimens. Different patterns of genetic diversity were observed between the two species, as well as among Med specimens sampled on the ornamental versus vegetables, with the highest genetic diversity found in Med B. tabaci sampled on L. camara. These findings lead us to focus our discussion on the role played by lantana, human pressure, and competition, in the spatial and genetic patterns observed in the whitefly B. tabaci.     

Bemisia tabaci in Iraq: Population structure,endosymbiont diversity and putative species

Whiteflies (Hemiptera: Aleyrodidae) are major pests of many crops worldwide. Bemisia tabaci is a cryptic species complex composed of more than 39 putative species. Understanding which putative species of B. tabaci are predominant in an area is vital for effective pest management since they may vary considerably with respect to insecticide resistance, host plant range and virus transmission. Here, for the first time, the genetic diversity, the symbiont diversity and population structure of B. tabaci in Iraq were studied. Fourteen populations were analysed using mitochondrial cytochrome C oxidase subunit 1 (mtCO1) sequencing and microsatellite genotyping. Symbiotic bacteria were identified using 16S rRNA and 23S rRNA sequencing. MtCO1 sequencing detected two putative species of B. tabaci. The predominant putative species in Iraq was Middle East-Asia Minor (MEAM) 1 subcladeB2. In addition, one individual was MEAM1-subcladeB. The second putative species was a single individual of MEAM2. The microsatellite data indicated low genetic diversity, with no biologically informative clustering. All MEAM1 individuals harboured one primary symbiont, Portiera aleyrodidarum, and most (96%) have two secondary symbionts: Hamiltonella sp. and Rickettsia sp. This study has identified the genetic diversity and population structure of B. tabaci in Iraq. Further investigation is needed to update the pest status of B. tabaci in this region. The current data, combined with investigations into the capacity of the various putative species to transmit plant viruses, especially tomato yellow leaf curl virus, will aid pest management and horticultural production.     

Genetic diversity and phylogenetic relationships among five endemic Pinus taxa (Pinaceae) of China as revealed by SRAP markers

The genetic diversity and phylogenetic relationships among five endemic Pinus taxa of China (Pinus tabulaeformis, P. tabulaeformis var. mukdensis, P. tabulaeformis f. shekanensis, Pinus massoniana and Pinus henryi) were studied by SRAP markers. Using 10 SRAP primer pairs, 247 bands were generated. The percent of polymorphic bands (94.8%), Nei's genetic diversity (0.2134), and Shannon's information index (0.3426) revealed a high level of genetic diversity at the genus-level. At the taxon level, P. tabulaeformis f. shekanensis and P. henryi showed a higher genetic diversity than the others. The coefficient of genetic differentiation among taxa (0.3332) indicated a higher level of genetic diversity within taxon, rather than among taxa. An estimate of gene flow among taxa was 1.0004 and implied a certain amount of gene exchange among taxa. The results of neighbor-joining cluster analysis and principal co-ordinate analysis revealed that P. tabulaeformis, P. tabulaeformis var. mukdensis and P. tabulaeformis f. shekanensis were conspecific, which was in agreement with the traditional classification. Phylogenetic relationships analysis also indicated that P. henryi might be a distinct species closely related to P. tabulaeformis.     

At least two indigenous species of the Bemisia tabaci complex are present in Brazil

Bemisia tabaci is one of the most important global agricultural insect pests, being a vector of emerging plant viruses such as begomoviruses and criniviruses that cause serious problems in many countries. Although knowledge of the genetic diversity of B. tabaci populations is important for controlling this pest and understanding viral epidemics, limited information is available on this pest in Brazil. A survey was conducted in different locations of São Paulo and Mato Grosso states, and the phylogenetic relationships of B. tabaci individuals from 43 populations sampled from different hosts were analysed based on partial mitochondrial cytochrome oxidase 1 gene (mtCOI) sequences. According to the recently proposed classification of the B. tabaci complex, which employs the 3.5% mtCOI sequence divergence threshold for species demarcation, most of the specimens collected were found to belong to the Middle East‐Asia Minor 1 species, which includes the invasive populations of the commonly known B biotype, within the Africa/Middle East/Asia Minor high‐level group. Three specimens collected from Solanun gilo and Ipomoea sp. were grouped together and could be classified in the New World species that includes the commonly known A biotype. However, six specimens collected from Euphorbia heterophylla, Xanthium cavanillesii and Glycine maxima could not be classified into any of the 28 previously proposed species, although according to the 11% mtCOI sequence divergence threshold, they belong to the New World high‐level group. These specimens were classified into a new recently proposed species named New World 2 that includes populations from Argentina. Middle East‐Asia Minor 1, New World and New World 2 were differentiated by RFLP analysis of the mtCOI gene using TaqI enzyme. Taq I analysis in silico also differentiates these from Mediterranean species, thus making this method a convenient tool to determine population dynamics, especially critical for monitoring the presence of this exotic pest in Brazil.     

Genetic diversity and geographic distribution of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) genotypes associated with cassava in East Africa

The genetic variability of whitefly (Bemisia tabaci) species, the vectors of cassava mosaic begomoviruses (CMBs) in cassava growing areas of Kenya, Tanzania, and Uganda, was investigated through comparison of partial sequences of the mitochondria cytochrome oxidase I (mtCOI) DNA in 2010/11. Two distinct species were obtained including sub‐Saharan Africa 1 (SSA1), comprising of two sub‐clades (I and II), and a South West Indian Ocean Islands (SWIO) species. Among the SSA1, sub‐clade I sequences shared a similarity of 97.8–99.7% with the published Uganda 1 genotypes, and diverged by 0.3–2.2%. A pairwise comparison of SSA1 sub‐clade II sequences revealed a similarity of 97.2–99.5% with reference southern Africa genotypes, and diverged by 0.5–2.8%. The SSA1 sub‐clade I whiteflies were widely distributed in East Africa (EA). In comparison, the SSA1 sub‐clade II whiteflies were detected for the first time in the EA region, and occurred predominantly in the coast regions of Kenya, southern and coast Tanzania. They occurred in low abundance in the Lake Victoria Basin of Tanzania and were widespread in all four regions in Uganda. The SWIO species had a sequence similarity of 97.2–97.7% with the published Reunion sequence and diverged by 2.3–2.8%. The SWIO whiteflies occurred in coast Kenya only. The sub‐Saharan Africa 2 whitefly species (Ug2) that was associated with the severe CMD pandemic in Uganda was not detected in our study.     

Genetic diversity of two endemic and endangered Plantago species

Plantago algarbiensis and Plantago almogravensis are two endangered and endemic species from Portugal. Due to the rarity and endangered nature of these species as well as the lack of molecular data, their genetic variation was evaluated using ISSR and RAPD markers. P. algarbiensis species showed higher genetic variability (73.9% of polymorphism) than P. almogravensis (61.2%). The two species revealed a high level of genetic diversity, with a Nei's genetic diversity of 0.1965 and 0.2309 and a Shannon's diversity index of 0.2975 and 0.3520, for P. almogravensis and P. algarbiensis, respectively. A low level of genetic differentiation was observed (Gst = 0.1873) among the species. However, the cluster and PCA analyses, based on genetic similarity, revealed two main, clearly separate clusters, which directly corresponded to the plants isolated from each species. In situ and ex situ measures should be applied in order to preserve both species but, based on these results, P. almogravensis population should be a priority for conservation.     

Genetic diversity and phylogenetic relationship of kenaf (Hibiscus cannabinus L.) accessions evaluated by SRAP and ISSR

Understanding genetic diversity and phylogenetic relationships is useful for plant breeding. In this study, we assessed the genetic diversity in a panel of 84 accessions of kenaf from 26 countries using SRAP and ISSR markers. The kenaf accessions could be divided into L1 (60 cultivated varieties) and L2 (24 wild accessions) at the level of 0.145 genetic dissimilarity coefficient by UPGMA. The L₂ group was further divided into two subgroups (16 relative-wide and 9 origin wide accessions) at the level of 0.207 genetic dissimilarity. Out of the 9 wild accessions in the L₂ group, 6 were from Tanzania and the remaining 3 lines were from Kenya. These results suggest that the center of origin for kenaf might be Tanzania and Kenya.     

喜马拉雅旱獭线粒体DNA控制区遗传多样性及系统发育

喜马拉雅旱獭是青藏高原的优势种,数量多、分布广,全面了解其遗传背景对该地区旱獭资源的保护与合理利用具有重要的意义。本研究以青藏高原云南、西藏和青海三省区共13个地理种群计258只旱獭为研究对象,PCR扩增获得线粒体DNA控制区基因部分序列(887 bp),并运用种群遗传学方法进行遗传多样性分析。结果显示:258份样品共发现了84个变异位点(9.40%),定义了68种单倍型,其单倍型多样性(h)平均值为0.968±0.003、核苷酸多样性(π)平均值为0.017 25±0.016 37,种群总体遗传多样性较高。AMOVA方差分析显示13个地理种群间存在着明显的遗传分化(Fst=0.620 67,P<0.001),种群间基因交流多数较低(Nm<1)。基于单倍型构建的系统发育树中13个地理种群的喜马拉雅旱獭聚为两支,其中来自青藏高原西南地区(西藏安多、青海格尔木、青海囊谦、云南迪庆)的18个单倍型聚成一个大的分支(A支),其余50个单倍型聚为一个大的分支(B支),在NETWORK网络图中也可见到相似网络拓扑结构。研究结果显示青藏高原喜马拉雅旱獭种群以唐古拉山脉为界分为两个大的种群,说明地理隔离是影响喜马拉雅旱獭种群动态变化的主要因素。     

Analysis of the genetic diversity of Bemisia tabaci populations in Shanxi province, China☆

Five different primer combinations were used for the analysis of 152 B biotype Bemisia tabaci (Gennadius) individuals and five Trialeurodes vaporairiorum individuals collected from 19 counties and seven host plants in Shanxi province in China, respectively. The main objective of the present study was to use AFLP markers to determine the genetic diversity of B. tabaci populations collected from Shanxi Province. The use of these primer combinations allowed the identification of 127 polymorphic bands (52.26%) from 60 to 500 bp. The average number of polymorphic bands per primer was 25.4 while the range for the five primers was 20–32. The average degree of heterozygosity was 0.251, while the range for the five primers was 0.204–0.289. The results suggested definite genetic diversity among different B. tabaci populations. Cluster analysis showed that B. tabaci populations were firstly scattered to three genetic groups according to the regions, then every genetic group was scattered to several subgroups according to the host plants, which revealed the genetic variability of B biotype B. tabaci populations has been not only among different regions, but also among different host plants in Shanxi Province.     

The Bemisia tabaci species complex: Additions from different parts of the world

Bemisia tabaci is one of the most threatening pests in many crops. We sequenced part of the mitochondrial cytochrome oxidase I gene from fifty whitefly populations collected in Indonesia, Thailand, India and China. Nineteen unique sequences (haplotypes) of the cytochrome oxidase I were identified in these populations. They were combined with sequences available in databases, resulting in a total of 407 haplotypes and analyzed together with nine outgroup accessions. A phylogenetic tree was calculated using the maximum likelihood method. The tree showed that all groups that were found in previous studies were also present in our study. Additionally, seven new groups were identified based on the new haplotypes. Most B. tabaci haplotypes grouped based on their geographical origin. Two groups were found to have a worldwide distribution. Our results indicate that our knowledge on the species complex around B. tabaci is still far from complete.     

Genetic diversity vs geographic distribution of five congeneric caddisflies

We compared the genetic structure and diversity offive Cheumatopsyche (Trichoptera:Hydropsychidae) species from Upper Three Runs Creek inSouth Carolina to analyze the relationship betweengenetic variability and potential gene flow (i.e.,geographic distribution) in a group of loticmacroinvertebrates. Among these species is an endemicto the stream (Cheumatopsyche richardsoni), asoutheastern U.S.A. endemic (C. edista), andthree widely distributed species (C. pasella,C. pettiti, and C. pinaca). Usingcellulose acetate plates, we reliably scored 19presumptive allozyme loci for each species. C. richardsoni and C. pettiti were the leastgenetically variable taxa, C. pasella and C. pinaca the most, and C. edista fell inbetween. Therefore, unless this C. pettitipopulation is not representative of the species ingeneral, the genetic diversity of C. richardsoniand C. edista fall within the range exhibited byother congeners. In turn, each species’ geneticdiversity is evidently not correlated to its relativegeographic distribution. Four species (all but C. pettiti) had moderate to high proportions ofpolymorphic loci in Hardy-Weinberg disequilibria, thecause of which is likely one of three factors: (1) eachspecies experiences disruptive selection, (2) weinadvertently sampled adults from more than onegenetically distinct stream population, or (3) eachspecies is divided into partially reproductivelyisolated subpopulations within the stream. This revised version was published online in July 2006 with corrections to the Cover Date.     

Analysis of the genetic diversity of Bemisia tabaci populations in Shanxi province, China

Five different primer combinations were used for the analysis of 152 B biotype Bemisia tabaci (Gennadius) individuals and five Trialeurodes vaporairiorum individuals collected from 19 counties and seven host plants in Shanxi province in China, respectively. The main objective of the present study was to use AFLP markers to determine the genetic diversity of B. tabaci populations collected from Shanxi Province. The use of these primer combinations allowed the identification of 127 polymorphic bands (52.26%) from 60 to 500 bp. The average number of polymorphic bands per primer was 25.4 while the range for the five primers was 20–32. The average degree of heterozygosity was 0.251, while the range for the five primers was 0.204–0.289. The results suggested definite genetic diversity among different B. tabaci populations. Cluster analysis showed that B. tabaci populations were firstly scattered to three genetic groups according to the regions, then every genetic group was scattered to several subgroups according to the host plants, which revealed the genetic variability of B biotype B. tabaci populations has been not only among different regions, but also among different host plants in Shanxi Province.     

Genetic identification of members of the Bemisia tabaci cryptic species complex from South Africa reveals native and introduced haplotypes

The whitefly Bemisia tabaci cryptic species complex contains some important agricultural pest and virus vectors. Members of the complex have become serious pests in South Africa (SA) because of their feeding habit and their ability to transmit begomovirus species. Despite their economic importance, studies on the biology and distribution of B. tabaci in SA are limited. To this end, a survey was made to investigate the diversity and distribution of B. tabaci cryptic species in eight geographical locations (provinces) in SA, between 2002 and 2009, using the mitochondrial cytochrome oxidase I (mtCOI) sequences. Phylogenetic analysis revealed the presence of members from two endemic sub‐Saharan Africa (SSAF) subclades coexisting with two introduced putative species. The SSAF‐1 subclade includes cassava host‐adapted B. tabaci populations, whereas the whiteflies collected from cassava and non‐cassava hosts formed a distinct subclade, referred to as SSAF‐5, and represent a new subclade among previously recognized southern Africa clades. Two introduced cryptic species, belonging to the Mediterranean and Middle East–Asia minor 1 clades, were identified and include the B and Q types. The B type showed the widest distribution, being present in five of the eight provinces explored in SA, infesting several host plants and predominating over the indigenous haplotypes. This is the first report of the occurrence of the exotic Q type in SA alongside the more widely distributed B type. Furthermore, mtCOI PCR‐RFLP was developed for the SA context to allow rapid discrimination between the B, Q and SSAF putative species. The capacity to manage pests and disease effectively relies on knowledge of the identity of the agents causing the damage. Therefore, this study contributes to the understanding of South African B. tabaci species diversity, information needed for the development of knowledge‐based disease management practices.     

Abundance,diversity and geographic distribution of cassava mosaic disease pandemic‐associated Bemisia tabaci in Tanzania

Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae), one of the most economically important agricultural pests worldwide, is the vector of cassava mosaic geminiviruses that cause cassava mosaic disease (CMD). In East and Central Africa, a severe CMD pandemic that spread from Uganda in the late 1980s still continues to devastate cassava crops. To assess the association of distinct B. tabaci genetic groups with the CMD pandemic, mitochondrial cytochrome oxidase I gene sequences were analysed from whiteflies collected during surveys conducted from 2010 to 2013 in Tanzania. Four genetic groups – Sub‐Saharan Africa 1 (SSA1), Mediterranean, Indian Ocean and East Africa 1, and a group of unknown whitefly species were identified. SSA1 comprised four subgroups: SSA1‐SG1, SSA1‐SG2, SSA1‐SG1/2 and SSA1‐SG3. SSA1‐SG1 was confined to the pandemic‐affected north‐western parts of Tanzania whilst SSA1‐SG2 and SSA1‐SG3 were found in the central and eastern parts not yet affected by the pandemic. The CMD pandemic front was estimated to lie in Geita Region, north‐western Tanzania, and to be spreading south‐east at a rate of ca 26 km/year. The pandemic‐associated B. tabaci SSA1‐SG1 predominated up to 180 km ahead of the CMD front indicating that changes in whitefly population characteristics precede changes in disease characteristics.     

Genetic groups and endosymbiotic microbiota of the Bemisia tabaci species complex in Japanese agricultural sites

The whitefly Bemisia tabaci is a cryptic species complex of at least 24 genetically distinct species. Thus far, one obligate and seven facultative symbiotic bacteria have been reported from the B. tabaci species complex. Both genetic groups and infected symbionts are extremely important to estimate the pest status of B. tabaci. In this study, we collected 340 whiteflies from 39 agricultural sites, covering an entire region of the B. tabaci habitat in Japan, and examined the genotypes and symbiont community composition at subspecies level. Use of the cleaved amplified polymorphic sequence technique and mitochondrial cytochrome oxidase subunit I gene sequencing detected five genetic groups: indigenous species JpL and Asia II 6, invasive species Middle East‐Asia Minor 1 (MEAM1) and Mediterranean Subclade Q1 (MED Q1), and a genetic group previously undetected in Asia, Mediterranean Subclade Q2 (MED Q2). The genetic groups exhibited characteristic infection statuses with regard to their facultative symbionts, as observed in other countries. The endosymbiotic microbiota of the Japanese MED Q1 was different from that in neighbouring countries, but similar to that in the French or Uruguayan MED Q1. These results may indicate that Japanese MED Q1 species have not invaded from neighbouring countries, but from distant countries by international transportation. All Japanese MED Q2 species were infected with Rickettsia, some of which are regarded as conferring a female‐biased sex ratio and fitness benefit on B. tabaci. The results suggest that MED Q2 may be prevalent in Japan and neighbouring countries.     

烟粉虱内共生菌16S rDNA的变异与系统发生

对 5年连续饲养在不同种寄主植物上的B型烟粉虱北京种群的内共生菌 1 6SrDNA基因进行了PCR扩增和测序。结合已知序列 ,构建了不同寄主植物烟粉虱初生内共生菌约 1 0 0 0bp的 1 6SrDNA及次生内共生菌约1 2 5 0bp的 1 6SrDNA的分子系统树。结果表明 ,中国北京不同寄主植物的B型烟粉虱内共生菌及世界其它地区烟粉虱内共生菌可能是同一种的不同生态型 ,内共生菌在其宿主分化后进行了选择 ,之后与其宿主长期共同进化、共同适应 ,为宿主对不同生境的适应提供了一定的基础     

Genetic networking of the Bemisia tabaci cryptic species complex reveals pattern of biological invasions

Background

A challenge within the context of cryptic species is the delimitation of individual species within the complex. Statistical parsimony network analytics offers the opportunity to explore limits in situations where there are insufficient species-specific morphological characters to separate taxa. The results also enable us to explore the spread in taxa that have invaded globally.

Methodology/Principal Findings

Using a 657 bp portion of mitochondrial cytochrome oxidase 1 from 352 unique haplotypes belonging to the Bemisia tabaci cryptic species complex, the analysis revealed 28 networks plus 7 unconnected individual haplotypes. Of the networks, 24 corresponded to the putative species identified using the rule set devised by Dinsdale et al. (2010). Only two species proposed in Dinsdale et al. (2010) departed substantially from the structure suggested by the analysis. The analysis of the two invasive members of the complex, Mediterranean (MED) and Middle East – Asia Minor 1 (MEAM1), showed that in both cases only a small number of haplotypes represent the majority that have spread beyond the home range; one MEAM1 and three MED haplotypes account for >80% of the GenBank records. Israel is a possible source of the globally invasive MEAM1 whereas MED has two possible sources. The first is the eastern Mediterranean which has invaded only the USA, primarily Florida and to a lesser extent California. The second are western Mediterranean haplotypes that have spread to the USA, Asia and South America. The structure for MED supports two home range distributions, a Sub-Saharan range and a Mediterranean range. The MEAM1 network supports the Middle East - Asia Minor region.

Conclusion/Significance

The network analyses show a high level of congruence with the species identified in a previous phylogenetic analysis. The analysis of the two globally invasive members of the complex support the view that global invasion often involve very small portions of the available genetic diversity.     

Genetic diversity and relationships among Canavalia ensiformis (L.) DC. Accessions as revealed by sequence-related amplified polymorphism markers

Canavalia ensiformis is an under-exploited legume that has been used as forage, green manure, and a cover crop. Thus far, studies of the C. ensiformis germplasm have focused on morphological traits, which cannot be used to distinguish all known accessions or to evaluate their genetic diversity precisely. In this study, sequence-related amplified polymorphism (SRAP) markers were used to assess the genetic diversity and relationships among 29 C. ensiformis accessions originating from 16 countries. In total, 274 clear bands were amplified and 144 of them (52.6%) were polymorphic. The polymorphism information content values (PIC) ranged from 0.10 to 0.43, with an average of 0.27. An analysis of molecular variance (AMOVA) revealed that the most significant variation (92.0% of the total) occurred among accessions; the remaining 8.0% was attributed to variation within accessions. A cluster analysis and principal coordinates (PCoA) analysis produced similar results, whereby the 29 C. ensiformis accessions were divided into 5 clusters, each of which was composed of different accessions with different phenotypic traits. This study provides the theoretical basis for future biodiversity studies and breeding programs.