Cecilia F. Bessega

Bio: Cecilia F. Bessega is an academic researcher from Facultad de Ciencias Exactas y Naturales. The author has contributed to research in topics: Genetic structure & Genetic variability. The author has an hindex of 4, co-authored 7 publications receiving 67 citations.

Genetic relationships among American species of Prosopis (Leguminosae) based on enzyme markers

Abstract: In the present work, isoenzyme electrophoresis was used to analyze the variability and phenetic relationships among seven American species of genus Prosopis belonging to three different sections: P. argentina (Monilicarpa), P. glandulosa, P. velutina, P. flexuosa, P. ruscifolia, P. kuntzei (Algarobia), and P. reptans (Strombocarpa). The genetic variability in P. argentina, P. reptans, and P. kuntzei was significantly lower than in the rest of the species analyzed. The species belonging to different sections are highly differentiated, but the relationships retrieved among species belonging to the section Algarobia suggested that the series of this section are not natural groups. P. kuntzei is as differentiated from the remaining species of Algarobia as from P. reptans or P. argentina, suggesting that this species might be included in a different section. The series within section Algarobia are not supported by the clusters retrieved in the phenogram based on isoenzymatic data. The results suggest that the two North American species (P. velutina and P. glandulosa) would have originated in different founder events.

First report on RAPDs patterns able to differentiate some Argentinean species of section Algarobia (Prosopis, Leguminosae).

Abstract: Prosopis species constitute a very important resource in arid and semiarid regions. Some species of section Algarobia hybridise and introgress naturally in areas of sympatry. According to previous isoenzymatic studies these species have high variability within populations. However, the genetic differentiation among species was very low, and these markers failed to provide diagnostic loci for species recognition. Here we analysed by the RAPD technique natural populations of Prosopis alba, P. ruscifolia, P. nigra, P. flexuosa ,a ndP. vinalillo with the purpose of obtaining markers for species and hybrid identification, by analysing the distribution of genetic diversity within and among species. Genetic variability (H = 0.12–0.26) was similar in all populations. Genetic differentiation among populations (FST = 0.39) was highly significant. Hierarchical analysis of genetic structure performed by Wright (1978) method and analysis of molecular variance (AMOVA) indicated that the diversity among populations within species is low (4–13%) and most genetic diversity (54–61%) occurs within populations. The differentiation among species is intermediate (26–42%) between the previous components but highly significant. Five bands provided a tool for identifying any of the species studied, with the exception of P. vinalillo .T he difficulty in diagnosing this species is discussed in reference to the hypothesis of its hybrid origin.

Fine-scale spatial genetic structure analysis in two Argentine populations of Prosopis alba (Mimosoideae) with different levels of ecological disturbance

Abstract: Spatial genetic structure (SGS) in plants is primarily determined by the interaction between pollen and seed dispersal, but it is strongly affected by both evolutionary and ecological processes. SGS studies in forest species also allow evaluating the consequences of human-mediated disturbance on pollen and seed movement and designing strategies of sustainable use of native forest resources. The present paper compares fine-scale SGS between two populations of Prosopis alba: Fernandez-Forres (FF) and Campo Duran (CD), based on the variation of 12 SSR markers. Populations show different history, management, and levels of disturbance. FF is highly disturbed and fragmented by agricultural activity and stock-breeding. Although no significant differences were observed in genetic variability parameters, highly significant genetic differentiation was detected with virtually no admixture between populations. SGS was positive and significant at short distances only in the non-disturbed population of CD. Accordingly, estimated neighborhood size and effective gene dispersal are higher in FF than in CD. This result might be explained by the higher incidence of livestock in seed dispersal and the patchy structure favoring longer pollen movement and artificial thinning and selection in FF. The results are relevant to conservation and breeding programs, suggesting that the distance between seed trees to be sampled should be larger than 22 m, the estimated distance of significant SGS in P. alba.

Quantifying connectivity between local Plasmodium falciparum malaria parasite populations using identity by descent.

Abstract: With the rapidly increasing abundance and accessibility of genomic data, there is a growing interest in using population genetic approaches to characterize fine-scale dispersal of organisms, providing insight into biological processes across a broad range of fields including ecology, evolution and epidemiology. For sexually recombining haploid organisms such as the human malaria parasite P. falciparum, however, there have been no systematic assessments of the type of data and methods required to resolve fine scale connectivity. This analytical gap hinders the use of genomics for understanding local transmission patterns, a crucial goal for policy makers charged with eliminating this important human pathogen. Here we use data collected from four clinics with a catchment area spanning approximately 120 km of the Thai-Myanmar border to compare the ability of divergence (FST) and relatedness based on identity by descent (IBD) to resolve spatial connectivity between malaria parasites collected from proximal clinics. We found no relationship between inter-clinic distance and FST, likely due to sampling of highly related parasites within clinics, but a significant decline in IBD-based relatedness with increasing inter-clinic distance. This association was contingent upon the data set type and size. We estimated that approximately 147 single-infection whole genome sequenced parasite samples or 222 single-infection parasite samples genotyped at 93 single nucleotide polymorphisms (SNPs) were sufficient to recover a robust spatial trend estimate at this scale. In summary, surveillance efforts cannot rely on classical measures of genetic divergence to measure P. falciparum transmission on a local scale. Given adequate sampling, IBD-based relatedness provides a useful alternative, and robust trends can be obtained from parasite samples genotyped at approximately 100 SNPs.

Molecular phylogeny and diversification history of Prosopis (Fabaceae: Mimosoideae)

Abstract: The genus Prosopis is an important member of arid and semiarid environments around the world. To study Prosopis diversification and evolution, a combined approach including molecular phylogeny, molecular dating, and character optimization analysis was applied. Phylogenetic relationships were inferred from five different molecular markers (matK-trnK, trnL-trnF, trnS-psbC, G3pdh, NIA). Taxon sampling involved a total of 30 Prosopis species that represented all Sections and Series and the complete geographical range of the genus. The results suggest that Prosopis is not a natural group. Molecular dating analysis indicates that the divergence between Section Strombocarpa and Section Algarobia plus Section Monilicarpa occurred in the Oligocene, contrasting with a much recent diversification (Late Miocene) within each of these groups. The diversification of the group formed by species of Series Chilenses, Pallidae, and Ruscifoliae is inferred to have started in the Pliocene, showing a high diversification rate. The moment of diversification within the major lineages of American species of Prosopis is coincident with the spreading of arid areas in the Americas, suggesting a climatic control for diversification of the group. Optimization of habitat parameters suggests an ancient occupation of arid environments by Prosopis species. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 93, 621–640.

Single primer amplification reaction (SPAR) reveals intra-specific natural variation in Prosopis cineraria (L.) Druce

Abstract: Prosopis cineraria, an important multipurpose tree and vital component of the otherwise fragile ecosystem of arid and semiarid regions of India. It is highly drought tolerant and sprouts profusely during the extreme dry summer months when most other trees are leafless. P. cineraria is known to exhibit comparable genetic variations at intra-specific and inter-population levels reflected through morphological and cytogenetical diversity in regions, where this plant grows naturally. In the present study, single primer amplification reaction (SPAR) methods have been used for determination of diversity at DNA level in 30 accessions of P. cineraria collected from different districts of Rajasthan. The analyses include the use of six minisatellite core sequence primers for direct amplification of minisatellite DNA (DAMD), eight inter simple sequence repeats (ISSR) and 20 arbitrary primed decamer sequences for random amplification (RAPD) reactions. Upon analysis of the data generated, all the three SPAR methods, either independently and/or in combination, revealed wide range of genetic variation among accessions. Comparison of matrix of individual SPAR method using MxComp component of NTSYS-pc 2.02 K software proving that analysis of natural genetic variation using combination of SPAR methods particularly ISSR and DAMD, rather than an isolated approach, is very effective. Such an approach also yields better information and reflection of the relatedness and affinities at intra-species and inter-population levels. Therefore, it is opined that in order to reveal the intrinsic intra-specific variation, SPAR approaches involving more than one DNA marker may reveal more authentic genetic variation in tropical tree species like P. cineraria.

Genetic relationships among American species of the genus Prosopis (Mimosoideae, Leguminosae) inferred from ITS sequences: evidence for long-distance dispersal

Abstract: Aim The genus Prosopis includes 44 species and has a pseudoamphitropical, disjunct distribution. We aimed to determine whether American Prosopis sections arose in North or South America, and to explain the current distribution of their species on the basis of their genetic relationships. Location South-western USA, Mexico, Caribbean Antilles, Peru–Ecuador, central and northern Argentina, south-western Argentina (Patagonia) and Cuyo, south-western Asia and northern Africa. Methods Internal transcribed spacer fragments from 21 species of Prosopis were sequenced and the data were used to analyse the phylogenetic relationships using Microlobius and Mimosa as outgroups. Genetic distances were calculated to estimate the degree of divergence. Dispersal–vicariance (DIVA) analysis was conducted to help understand the biogeographical history of the genus. Main conclusions The sections Strombocarpa and Algarobia are not monophyletic. Prosopis argentina (section Monilicarpa) and the species of Algarobia are included in single clade. The phylogeny, DIVA analysis, and the pattern of genetic distances indicate that the ancestral area for the American species was wide, from south-western USA to Central and northern Argentina. Successive vicariance events split this area, and long-distance dispersal episodes (perhaps mediated by birds) led to recolonizations from North to South America, and vice versa.

The pre-Columbian introduction and dispersal of Algarrobo (Prosopis, Section Algarobia) in the Atacama Desert of northern Chile

Abstract: Archaeological and palaeoecological studies throughout the Americas have documented widespread landscape and environmental transformation during the pre-Columbian era. The highly dynamic Formative (or Neolithic) period in northern Chile (ca. 3700-1550 yr BP) brought about the local establishment of agriculture, introduction of new crops (maize, quinoa, manioc, beans, etc.) along with a major population increase, new emergent villages and technological innovations. Even trees such as the Algarrobos (Prosopis section Algarobia) may have been part of this transformation. Here, we provide evidence that these species were not native to the Atacama Desert of Chile (18-27°S), appearing only in the late Holocene and most likely due to human actions. We assembled a database composed of 41 taxon specific AMS radiocarbon dates from archaeobotanical and palaeoecological records (rodent middens, leaf litter deposits), as well an extensive bibliographical review comprising archaeobotanical, paleoecological, phylogenetic and taxonomic data to evaluate the chronology of introduction and dispersal of these trees. Although Algarrobos could have appeared as early as 4200 yr BP in northernmost Chile, they only became common throughout the Atacama over a thousand years later, during and after the Formative period. Cultural and natural factors likely contributed to its spread and consolidation as a major silvicultural resource.