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Papers by patricia delgado

International Journal of Plant Sciences, 2007

Pinus pseudostrobus and Pinus montezumae are closely related species. They belong to the subsecti... more Pinus pseudostrobus and Pinus montezumae are closely related species. They belong to the subsection Ponderosae, with a wide geographical distribution in Mexico and Central America. Morphological, biochemical, and anatomical information suggests that these species can form hybrids in natural populations. In this study, molecular (chloroplast microsatellites) and morphological markers were studied in 13 natural populations of these species to test the existence of introgressive hybridization, infer its dynamics, and describe the phylogeographic structure of the populations. Using analytical methods of population genetics, as well as Bayesian inference and coalescent approach, we show that putative hybrid populations are more similar to P. pseudostrobus than to P. montezumae and that these populations had the highest estimates of morphological and genetic variation. Furthermore, a greater introgression rate was observed from P. montezumae to putative hybrid and P. pseudostrobus populations. We showed that genetic structure as well as introgression dynamics of populations could be the result of colonization events, historical expansion, and isolation by distance. Our results suggest the existence of three independent lineages (P. pseudostrobus, P. montezumae, and putative hybrid) that have coexisted and diversified during the past 11-27 million years as well as the possible origin of evolutionary new lineages through repeated introgressive hybridization combined with lineage sorting of ancestral polymorphisms.

American Journal of Botany, 1999

Pinus rzedowskii is an endangered pine species from Michoacán (central México), which has been pr... more Pinus rzedowskii is an endangered pine species from Michoacán (central México), which has been previously reported from only three localities. Classified within the subgenus Strobus, it exhibits intermediate morphological characters between subgenera Strobus and Pinus. We analyzed genetic aspects that could shed light on the evolution and conservation of this species. The genetic structure of nine populations was examined using 14 isozyme loci. Pinus rzedowskii has a relatively high level of genetic variation with 46.8% of the loci assayed being polymorphic, a total of 35 alleles, and a mean heterozygosity per population of 0.219. We calculated Wright's F ST statistic to estimate gene flow indirectly and to evaluate whether or not there was genetic structuring among populations. We found a marked differentiation among populations (F ST ϭ 0.175) and significant inbreeding (F IS ϭ 0.247). No pattern of isolation by distance was found. We also constructed a dendrogram based on a genetic distance matrix to obtain an overview of the possible historical relationships among populations. Finally, we found a convex relationship between the genetic distance among populations and the number of ancestral lineages, suggesting that demographically this species has not been at risk recently. Although endangered, with small and fragmented populations, P. rzedowskii shows higher levels of genetic variation than other conifer species with larger populations or similar conservation status.

Canadian Journal of Botany-revue Canadienne De Botanique, 2001

Mexico is a major center of diversity for the genus Pinus as it has the greatest number of specie... more Mexico is a major center of diversity for the genus Pinus as it has the greatest number of species in the world. Many species are now restricted to Mexico, and some are represented by very small populations and are in danger of extinction. In this study we examined allozyme variation in three rare species of Mexican pines: Pinus pinceana Gord., Pinus lagunae M.F. Passini, and Pinus muricata D. Don, with the objective of providing conservation guidelines. The three species had relatively high levels of genetic variation with mean expected heterozygosities of 0.373, 0.386, and 0.346 for P. pinceana, P. lagunae, and P. muricata, respectively. We found marked differentiation among populations and significant inbreeding within populations of the three species. These values are larger than the range reported for most conifers and suggest that conservation strategies of these rare pines require focusing on the viability of several populations. Given that our knowledge about the demographic status of the three species is scarce, we propose a mixed strategy of conservation. For P. lagunae, we propose an in situ strategy, whereas for P. pinceana and P. muricata we propose an ex situ strategy of conservation until permanent protection can be provided for several of their populations.

Revista Chilena De Historia Natural, 2002

Pines have been the focus of several studies that estimate population genetic parameters using bo... more Pines have been the focus of several studies that estimate population genetic parameters using both allozymes and chloroplast single sequence repeats (SSRs). Also, the genus has also been recently studied using molecular systematics so that we now have a more clear understanding of their evolutionary history. With this background we studied comparatively the genetic structure in pines. Expected heterozygosity is particularly constant with a 99 % confidence interval between 0.19 and 0.23 in species that have been studied until now using allozymes. There is a significant proportion of species (9/41) that show high population differentiation estimates (F ST = or larger than 0.15) and five of these have large and wingless seeds probably associated with low densities, bird dispersal mechanisms and resistance to water stress. These species include the North American pinyon pines. Outcrossing rates are also constant among species from both subgenus Pinus and subgenus Strobus, which probably reflects a selective limit to the amount of deleterious alleles that can be maintained in pine species and this also affects inbreeding levels. We also explored the data published using microsatellites in pines and conclude that these markers uncover a higher proportion of variation and genetic differentiation as expected and that the evolutionary models that are used to derive the population genetic structure estimators should take into account other sources of mutation (point mutations, larger insertions and or deletions and duplications) to better understand the comparative applications of these molecular markers.

Theoretical and Applied Genetics, 1998

In the genus Pinus the internal transcribed spacers (ITS1 and ITS2) and the 5.8s region of the nu... more In the genus Pinus the internal transcribed spacers (ITS1 and ITS2) and the 5.8s region of the nuclear ribosomal DNA are approximately 3000 bp in length. ITS1 is considerably longer than ITS2 and partial sequences of ITS1 indicate that this region is evolving rapidly and exhibits intraspecific variation. The ITS2 and 5.8s regions are relatively conserved. We surveyed restriction fragment length variability of PCR-amplified fragments (PCR-RFLP) of the ITS region in four populations (86 individuals) of Pinus rzedowskii, a pine endemic to western Michoacán, Mexico. Five of the restriction endonucleases assayed revealed variation, with a total of 13 variants, most of which were length mutations of 300–900 bp. A moderate degree of population differentiation was detected. The average diversity (Shannon’s index) of ITS fragment size patterns was 1.19, with 34% of the variation due to differences among populations and 66% due to differences among individuals within populations. The same individuals were assayed for nine polymorphic isozymes, which gave diversity measures similar to those of each restriction endonuclease.

Biodiversity and Conservation, 2008

Phylogenetic, genetic and demographic information are key issues for establishing priorities for ... more Phylogenetic, genetic and demographic information are key issues for establishing priorities for conservation. In this study we explored the Vane-Wrigth measure of phylogenetic diversity for establishing criteria for conservation, when intra as well as interpopulation level demographic (population size) and genetic (heterozygosity, inbreeding and genetic distances among populations) parameters are taken into consideration. The data were standardized and analyzed independently and integratively enabling the calculation of indices or criteria for conservation priorities. We illustrate the application of this approach in populations of four Mexican pine species that have been considered rare and endangered, Pinus rzedowzkii, P. pinceana, P. lagunae and P. muricata. The application of several independent diversity indices did not allow us to resolve prioritization. However, the integration of all indices generated different values of importance to conservation, and suggested that the populations with the highest priorities for conservation are: two for Pinus rzedowskii, P. pinceana, and P. lagunae, and one for P. muricata. These populations have intermediate sizes, are the most divergent in the phylogeny and contain genetic variation that is representative of the gene pool of each species. Finally, we demonstrated the functionality of some genetic and demographic parameters; the genetic structure, recruitment rate, geographic distribution and demographic stochasticity, as complementary indicators for evaluating the conservation priority among populations and species.

International Journal of Plant Sciences, 2007

Pinus pseudostrobus and Pinus montezumae are closely related species. They belong to the subsecti... more Pinus pseudostrobus and Pinus montezumae are closely related species. They belong to the subsection Ponderosae, with a wide geographical distribution in Mexico and Central America. Morphological, biochemical, and anatomical information suggests that these species can form hybrids in natural populations. In this study, molecular (chloroplast microsatellites) and morphological markers were studied in 13 natural populations of these species to test the existence of introgressive hybridization, infer its dynamics, and describe the phylogeographic structure of the populations. Using analytical methods of population genetics, as well as Bayesian inference and coalescent approach, we show that putative hybrid populations are more similar to P. pseudostrobus than to P. montezumae and that these populations had the highest estimates of morphological and genetic variation. Furthermore, a greater introgression rate was observed from P. montezumae to putative hybrid and P. pseudostrobus populations. We showed that genetic structure as well as introgression dynamics of populations could be the result of colonization events, historical expansion, and isolation by distance. Our results suggest the existence of three independent lineages (P. pseudostrobus, P. montezumae, and putative hybrid) that have coexisted and diversified during the past 11-27 million years as well as the possible origin of evolutionary new lineages through repeated introgressive hybridization combined with lineage sorting of ancestral polymorphisms.

American Journal of Botany, 1999

Pinus rzedowskii is an endangered pine species from Michoacán (central México), which has been pr... more Pinus rzedowskii is an endangered pine species from Michoacán (central México), which has been previously reported from only three localities. Classified within the subgenus Strobus, it exhibits intermediate morphological characters between subgenera Strobus and Pinus. We analyzed genetic aspects that could shed light on the evolution and conservation of this species. The genetic structure of nine populations was examined using 14 isozyme loci. Pinus rzedowskii has a relatively high level of genetic variation with 46.8% of the loci assayed being polymorphic, a total of 35 alleles, and a mean heterozygosity per population of 0.219. We calculated Wright's F ST statistic to estimate gene flow indirectly and to evaluate whether or not there was genetic structuring among populations. We found a marked differentiation among populations (F ST ϭ 0.175) and significant inbreeding (F IS ϭ 0.247). No pattern of isolation by distance was found. We also constructed a dendrogram based on a genetic distance matrix to obtain an overview of the possible historical relationships among populations. Finally, we found a convex relationship between the genetic distance among populations and the number of ancestral lineages, suggesting that demographically this species has not been at risk recently. Although endangered, with small and fragmented populations, P. rzedowskii shows higher levels of genetic variation than other conifer species with larger populations or similar conservation status.

Canadian Journal of Botany-revue Canadienne De Botanique, 2001

Mexico is a major center of diversity for the genus Pinus as it has the greatest number of specie... more Mexico is a major center of diversity for the genus Pinus as it has the greatest number of species in the world. Many species are now restricted to Mexico, and some are represented by very small populations and are in danger of extinction. In this study we examined allozyme variation in three rare species of Mexican pines: Pinus pinceana Gord., Pinus lagunae M.F. Passini, and Pinus muricata D. Don, with the objective of providing conservation guidelines. The three species had relatively high levels of genetic variation with mean expected heterozygosities of 0.373, 0.386, and 0.346 for P. pinceana, P. lagunae, and P. muricata, respectively. We found marked differentiation among populations and significant inbreeding within populations of the three species. These values are larger than the range reported for most conifers and suggest that conservation strategies of these rare pines require focusing on the viability of several populations. Given that our knowledge about the demographic status of the three species is scarce, we propose a mixed strategy of conservation. For P. lagunae, we propose an in situ strategy, whereas for P. pinceana and P. muricata we propose an ex situ strategy of conservation until permanent protection can be provided for several of their populations.

Revista Chilena De Historia Natural, 2002

Pines have been the focus of several studies that estimate population genetic parameters using bo... more Pines have been the focus of several studies that estimate population genetic parameters using both allozymes and chloroplast single sequence repeats (SSRs). Also, the genus has also been recently studied using molecular systematics so that we now have a more clear understanding of their evolutionary history. With this background we studied comparatively the genetic structure in pines. Expected heterozygosity is particularly constant with a 99 % confidence interval between 0.19 and 0.23 in species that have been studied until now using allozymes. There is a significant proportion of species (9/41) that show high population differentiation estimates (F ST = or larger than 0.15) and five of these have large and wingless seeds probably associated with low densities, bird dispersal mechanisms and resistance to water stress. These species include the North American pinyon pines. Outcrossing rates are also constant among species from both subgenus Pinus and subgenus Strobus, which probably reflects a selective limit to the amount of deleterious alleles that can be maintained in pine species and this also affects inbreeding levels. We also explored the data published using microsatellites in pines and conclude that these markers uncover a higher proportion of variation and genetic differentiation as expected and that the evolutionary models that are used to derive the population genetic structure estimators should take into account other sources of mutation (point mutations, larger insertions and or deletions and duplications) to better understand the comparative applications of these molecular markers.

Theoretical and Applied Genetics, 1998

In the genus Pinus the internal transcribed spacers (ITS1 and ITS2) and the 5.8s region of the nu... more In the genus Pinus the internal transcribed spacers (ITS1 and ITS2) and the 5.8s region of the nuclear ribosomal DNA are approximately 3000 bp in length. ITS1 is considerably longer than ITS2 and partial sequences of ITS1 indicate that this region is evolving rapidly and exhibits intraspecific variation. The ITS2 and 5.8s regions are relatively conserved. We surveyed restriction fragment length variability of PCR-amplified fragments (PCR-RFLP) of the ITS region in four populations (86 individuals) of Pinus rzedowskii, a pine endemic to western Michoacán, Mexico. Five of the restriction endonucleases assayed revealed variation, with a total of 13 variants, most of which were length mutations of 300–900 bp. A moderate degree of population differentiation was detected. The average diversity (Shannon’s index) of ITS fragment size patterns was 1.19, with 34% of the variation due to differences among populations and 66% due to differences among individuals within populations. The same individuals were assayed for nine polymorphic isozymes, which gave diversity measures similar to those of each restriction endonuclease.

Biodiversity and Conservation, 2008

Phylogenetic, genetic and demographic information are key issues for establishing priorities for ... more Phylogenetic, genetic and demographic information are key issues for establishing priorities for conservation. In this study we explored the Vane-Wrigth measure of phylogenetic diversity for establishing criteria for conservation, when intra as well as interpopulation level demographic (population size) and genetic (heterozygosity, inbreeding and genetic distances among populations) parameters are taken into consideration. The data were standardized and analyzed independently and integratively enabling the calculation of indices or criteria for conservation priorities. We illustrate the application of this approach in populations of four Mexican pine species that have been considered rare and endangered, Pinus rzedowzkii, P. pinceana, P. lagunae and P. muricata. The application of several independent diversity indices did not allow us to resolve prioritization. However, the integration of all indices generated different values of importance to conservation, and suggested that the populations with the highest priorities for conservation are: two for Pinus rzedowskii, P. pinceana, and P. lagunae, and one for P. muricata. These populations have intermediate sizes, are the most divergent in the phylogeny and contain genetic variation that is representative of the gene pool of each species. Finally, we demonstrated the functionality of some genetic and demographic parameters; the genetic structure, recruitment rate, geographic distribution and demographic stochasticity, as complementary indicators for evaluating the conservation priority among populations and species.