BackgroundProsopis rubriflora and Prosopis ruscifolia are important species in the Chaquenian regions of Brazil. Because of the restriction and frequency of their physiognomy, they are excellent models for conservation genetics studies. The use of microsatellite markers (Simple Sequence Repeats, SSRs) has become increasingly important in recent years and has proven to be a powerful tool for both ecological and molecular studies.FindingsIn this study, we present the development and characterization of 10 new markers for P. rubriflora and 13 new markers for P. ruscifolia. The genotyping was performed using 40 P. rubriflora samples and 48 P. ruscifolia samples from the Chaquenian remnants in Brazil. The polymorphism information content (PIC) of the P. rubriflora markers ranged from 0.073 to 0.791, and no null alleles or deviation from Hardy-Weinberg equilibrium (HW) were detected. The PIC values for the P. ruscifolia markers ranged from 0.289 to 0.883, but a departure from HW and null alleles were detected for certain loci; however, this departure may have resulted from anthropic activities, such as the presence of livestock, which is very common in the remnant areas.ConclusionsIn this study, we describe novel SSR polymorphic markers that may be helpful in future genetic studies of P. rubriflora and P. ruscifolia.

The Gran Chaco is the largest continuous region of the South American dry forest, spanning Argentina, Paraguay, Bolivia, and Brazil. Prosopis rubriflora and Prosopis ruscifolia are typical tree species of chaquenian area forests, which have been subjected to continuous fragmentation caused by cattle raising. This study evaluated P. rubriflora and P. ruscifolia in areas with varying levels of disturbance. We investigated the contemporary genetic diversities of both species in areas with distinct anthropogenic disturbances. Even with a lower heterozygote frequency, disturbed areas can provide important storage for alleles, allowing the maintenance of diversity. The genetic diversity of P. rubriflora was surprisingly similar to that of P. ruscifolia (H e = 0.59 and H e = 0.60, respectively) even with very different distribution ranges of both species. However, P. ruscifolia exhibited a higher intrapopulation fixation index than P. rubriflora. P. rubriflora showed evidence of bottlenecking in 64% of the sampled areas, while P. ruscifolia showed such evidence in 36% of the sampled areas. Additionally, P. rubriflora had two distinct populations due to its disjunctive geographic distribution, whereas P. ruscifolia had a single population that exhibited few signs of population structure in some areas, possibly due to the main pollinators presenting a short range of dispersion. Our results suggest that 42 Chaco areas should be conserved to retain the minimum of 500 individuals necessary to maintain genetic diversity for 100–1,000 generations. This study improves our understanding of these two Prosopis species and provides information for the conservation of their genetic diversities.

Prosopis rubriflora Hassl. is a tree species typically found in chaquenian areas, mainly with an arborised phytophysiognomy in the southern region of the Pantanal wetland. This species has become vulnerable in recent decades as a result of considerable increases in anthropogenic activities such as cattle breeding, and this vulnerability has also been observed in several other native species. The goal of this study was to estimate the mating system of P. rubriflora in a Chaco remnant by analysing 10 microsatellite markers. Samples were collected over 2 years (2010–213 seedlings and 2011–180 seedlings), and the results suggest that the mating system of P. rubriflora is preferably allogamous. A progeny array was predominantly composed of half-sibs (from 76 to 79%), full-sibs (from 15%) and self-half-sibs (from 6 to 9%). The outcrossing rate between related individuals was significant in 2011 but not in 2010. The average co-ancestry coefficient () ranged from 0.158 to 0.162, and the variance effective size (Ne) ranged from 3.05 to 3.13. The number of seed trees required for seed collection (m) to retain an effective size of 150 in progeny array samples was 48–49. The high levels of outcrossing of P. rubriflora appear to be related to several mechanisms that avoid selfing and due to the behaviour of native pollinators, which clearly contribute to the gene flow of the species.