Spatial structures strongly influence ecological processes. Connectivity is known to positively influence metapopulation demography and genetics by increasing the rescue effect and thus favoring individual and gene flow between populations. This result has not been tested in the special case of dendritic networks, which encompass stream and cave ecosystem for instance. We propose a first approach using an individual based model to explore the population demography and genetics in various dendritic networks. To do so, we first generate a large number of different networks, and we analyze the relationship between their hydrographical characteristics and connectivity. We show that connectivity mean and variance of connectivity are strongly correlated in dendritic networks. Connectivity segregates two types of networks: Hortonian and non-Hortonian networks. We then simulate the population dynamics for a simple life cycle in each of the generated networks, and we analyze persistence time as well as populations structure at quasi-stationary state. Our main results show that connectivity in dendritic networks can promote local extinction and genetic isolation by distance at low dispersal and diminish the size of the metapopulation at high dispersal. We discuss these unexpected findings in the light of connectivity spatial distribution in dendritic networks in the case of our model.

No abstract

Current potato breeding approaches are hampered by several factors including costly seed tubers, tetrasomic inheritance and inbreeding depression. Genomic selection (GS) demonstrated interesting results regardless of the ploidy level, and can be harnessed to circumvent these problems. In this work, three GS models were evaluated using 50,107 informative SilicoDArT markers and 11 traits in two values for cultivation and use (VCU) potato trials. Two key breeding problems modelled included predicting the performance of (i) new and unphenotyped clones (cross‐validation) and (ii) a VCU using another as training set (TS). GS models performed comparably. Cross‐validation accuracy was high for D35, D45, DMW and BVAL, in ascending order. Prediction accuracies of the VCUs were highly correlated, but the best prediction was obtained for the smaller VCU using the bigger as TS. Cross‐validation and VCU prediction accuracies were higher when bigger TSs were used. The findings herein indicate that GS can be attractively integrated in potato breeding, particularly in early clonal generations to predict and select for traits with low heritability which would otherwise require more testing years, environments and resources.

A DNA polymerase has been extracted from spinach chloroplasts and purified by chromatography on DEAE-cellulose and hydroxyapatite. A great similarity between the purified chloroplast polymerase and the mammalian mitochondrial DNA polymerase y was found by several criteria :preference for the synthetic primer-template (dT)lz -18 . poly(rA), optimal requirement for Mn2+ (0.1 -1.0 mM), KCl(lO0 mM) and pH (8 -9), high relative molecular mass (approximately 105 000), resistance to aphidicolin and inhibition by N-ethylmaleimide. Some peculiar features of the chloroplast DNA polymerase have, however, been noticed.The mammalian DNA polymerase y has been suggested to be responsible for the replication of mitochondrial DNA. Thus, both the presence of a y-like DNA polymerase in chloroplasts and the similarities between the chloroplast and the mitochondrial DNA (absence of a nucleosomal structure and presence of displacement loops) lead to the suggestion that chloroplast DNA is also replicated by a y-like DNA polymerase and that the y polymerases present in eukaryotes are, therefore, involved in a strand-displacement DNA synthesis.An a-like DNA polymerase activity, present and predominant in crude leaf extracts, was practically absent from purified chloroplast preparations.Developed chloroplasts contain multiple copies (up to 50) of possibly identical supertwisted circular DNA molecules, one circle thus constituting the entire chloroplast genome [l-31. ctDNA resembles mtDNA and bacterial DNA in several aspects, among them the absence of supromolecular organization in chromatin structures, and is thus substantially different from the chromosomal DNA present in nuclei [2,4,5].Recent data indicate that animal mitochondria contain a unique DNA polymerase (DNA polymerase y) [6 -81, which is responsible for the replication of mtDNA [9,10]. On the other hand, no information is available on the enzyme(s) involved in the replication of ctDNA [2,5]. Chloroplasts isolated from tobacco [ l l ] and spinach [12] are capable of incorporating deoxynucleotides into chloroplast DNA. However, this activity was not purified and characterized.In this work we show that spinach leaves contain at least two DNA polymerases and that only one of them is localized in the chloroplast. The properties of the partially purified chloroplast enzyme are similar in many aspects to those of DNA polymerase y, the replicative enzyme of animal mtDNA. Some peculiarities have, however, been noticed. MATERIALS AND METHODS MaterialsN-Ethylmaleimide was from Sigma Chemicals Corp. ; p-toluenesulfonyl fluoride (TosF) was from Aldrich; poly(rA), poly(dA), poly(rC) and poly(dC) from Miles Laboratories; (dT)1Z -18 and (dG)12 -18 were from PL-Biochemicals ; [3H]dTTP was from Amersham; Teepol 610 was from BDH Chemicals; D-mannitol was from Carlo Erba; sucrose was from Merck; DEAE-cellulose (DE-52) and phosphocellulose (Pll) were from Whatman; hydroxyapatite was prepared according to Bernardi [13].Ahbreviutions. ctDNA, chloroplast DNA; mtDNA, mitochondrial DNA; TosF, p-tolue...

No abstract