RESUMEN
AFLP markers are often used to study patterns of population genetic variation and gene flow because they offer a good coverage of the nuclear genome, but the reliability of AFLP scoring is critical. To assess interspecific gene flow in two African rainforest liana species (Haumania danckelmaniana, H. liebrechtsiana) where previous evidence of chloroplast captures questioned the importance of hybridization and species boundaries, we developed new AFLP markers and a novel approach to select reliable bands from their degree of reproducibility. The latter is based on the estimation of the broad-sense heritability of AFLP phenotypes, an improvement over classical scoring error rates, which showed that the polymorphism of most AFLP bands was affected by a substantial nongenetic component. Therefore, using a quantitative genetics framework, we also modified an existing estimator of pairwise kinship coefficient between individuals correcting for the limited heritability of markers. Bayesian clustering confirms the recognition of the two Haumania species. Nevertheless, the decay of the relatedness between individuals of distinct species with geographic distance demonstrates that hybridization affects the nuclear genome. In conclusion, although we showed that AFLP markers might be substantially affected by nongenetic factors, their analysis using the new methods developed considerably advanced our understanding of the pattern of gene flow in our model species.
Asunto(s)
Análisis del Polimorfismo de Longitud de Fragmentos Amplificados/métodos , Flujo Génico , Variación Genética , Marantaceae/genética , África Central , Teorema de Bayes , ADN de Plantas/genética , Marcadores Genéticos , Haplotipos , Hibridación Genética , Marantaceae/clasificación , Filogenia , Filogeografía , Reproducibilidad de los ResultadosRESUMEN
Species delimitation is a fundamental biological concept which is frequently discussed and altered to integrate new insights. These revealed that speciation is not a one step phenomenon but an ongoing process and morphological characters alone are not sufficient anymore to properly describe the results of this process. Here we want to assess the degree of speciation in two closely related lianescent taxa from the tropical African genus Haumania which display distinct vegetative traits despite a high similarity in reproductive traits and a partial overlap in distribution area which might facilitate gene flow. To this end, we combined phylogenetic and phylogeographic analyses using nuclear (nr) and chloroplast (cp) DNA sequences in comparison to morphological species descriptions. The nuclear dataset unambiguously supports the morphological species concept in Haumania. However, the main chloroplastic haplotypes are shared between species and, although a geographic analysis of cpDNA diversity confirms that individuals from the same taxon are more related than individuals from distinct taxa, cp-haplotypes display correlated geographic distributions between species. Hybridization is the most plausible reason for this pattern. A scenario involving speciation in geographic isolation followed by range expansion is outlined. The study highlights the gain of information on the speciation process in Haumania by adding georeferenced molecular data to the morphological characteristics. It also shows that nr and cp sequence data might provide different but complementary information, questioning the reliability of the unique use of chloroplast data for species recognition by DNA barcoding.
Asunto(s)
ADN de Cloroplastos/genética , ADN de Plantas/genética , Marantaceae/clasificación , Marantaceae/genética , Filogenia , África Central , Código de Barras del ADN Taxonómico , Flujo Génico/genética , Filogeografía , Especificidad de la EspecieRESUMEN
O objetivo do trabalho foi avaliar a capacidade produtiva da araruta (Maranta arundinaceae) Comum, da alface Grand Rapids e da cenoura Brasília, em cultivos solteiros e os consórcios araruta-alface e araruta-cenoura, em Dourados- MS. Para a alface e a cenoura constatou-se efeito significativo do tipo de cultivo, com os maiores valores nas plantas sob cultivo solteiro. Não houve produção de alface comercial. As características das plantas de cenoura solteiras foram aumentadas de 7,46 cm de altura; 5,36 Mg ha-¹ de massa fresca de folhas; 12,13 Mg ha-¹ de total de raízes; 11,23 Mg ha-¹ de raízes comerciais e 4,18 Mg ha-¹ de raízes não-comerciais, em relação às plantas consorciadas com a araruta. A altura das plantas da araruta variou entre 99,14 cm nas solteiras e 99,84 cm nas consorciadas com alface. As menores massas frescas dos rizomas e de raízes (19,87 Mg ha-¹ e 9,91 Mg ha-¹) foram das consorciadas com alface e as maiores (20,21 Mg ha-¹ e 11,96 Mg ha-¹) foram nas solteiras. Não obstante, a razão de área equivalente (RAE), para o consórcio araruta-alface foi de 0,98 e para o consórcio araruta-cenoura foi de 1,28. Como o valor da RAE do consórcio araruta-cenoura superou 1,0, concluiu-se que foi efetivo e que pode ser recomendado.
The objective of this work was to evaluate yield capacity of Comum arrowroot (Maranta arundinaceae), of Grand Rapids lettuce and of Brasilia carrot, in monocrop system and in arrowroot-lettuce and arrowroot-carrot intercrops, in Dourados- MS. For lettuce and carrot, it was established a significative effect of cultivation type with the highest values in plants under monocrop system. There was not yield of commercial lettuce. The characteristict of the carrot plants in monocrop system were increased of 7.46 cm of height; 5.36 Mg ha-¹ of fresh mass of leaves; 12.13 Mg ha-¹ of total roots; 11.23 Mg ha-¹ of commercial roots and 4.18 Mg ha-¹ of non-commercial roots in relation to plants intercropped with arrowroot. Height of arrowroot plants varied between 99.14 cm in monocrop system and 99.84 cm intercropped with lettuce. The smallest fresh masses of rhizomes and roots (19.87 Mg ha-¹ and 9.91 Mg ha-¹) were from those intercropped with lettuce and the highest (20.21 Mg ha-¹ and 11.96 Mg ha-¹) were in monocrop system. However, the Land Equivalent Ratio - LER for arrowroot-lettuce intercrop was of 0.98 and for arrowroot-carrot intercrop was of 1.28. As the value of LER of arrowroot-carrot was superior to 1.0, it was conclude that it was effective and it can be recommended.
El objetivo del trabajo fue evaluar la capacidad productiva de la yuquilla (Maranta arundinaceae) Comun, de la lechuga Grand Rapids y de la zanahoria Brasília, en monocultivo y en las asociaciones yuquilla-lechuga y yuquilla-zanahoria, en Dourados-MS. Para la lechuga y la zanahoria se constató efecto significativo del tipo de cultivo, con los mayores valores en las plantas en monocultivo. No hubo producción de lechuga comercial. Las características de las plantas de zanahoria en monocultivo fueron aumentadas de 7,46 cm de altura; 5,36 Mg ha-¹ de masa fresca de hojas; 12,13 Mg ha-¹ de total de raíces; 11,23 Mg ha-¹ de raíces comerciales e 4,18 Mg ha-¹ de raíces no comerciales, en relación a las plantas asociadas con la yuquilla. La altura de las plantas de yuquilla varió entre 99,14 cm en las en monocultivo y 99,84 cm en las asociadas con la lechuga. Las menores masas frescas de los rizomas y de las raíces (19,87 Mg ha-¹ y 9,91 Mg ha-¹) fueron de las asociadas con lechuga y las mayores (20,21 Mg ha-¹ y 11,96 Mg ha-¹) fueron de las en monocultivo. No obstante, la relación de área equivalente (RAE) para la asociación yuquilla-lechuga fue de 0,98 y para la asociación yuquilla-zanahoria fue de 1,28. Como el valor de la RAE de la asociación yuquilla-zanahoria superó a 1,0, se concluyó que fue efectivo y que puede ser recomendado.