Abstract The new species Dioon stevensonii, from the Rio Balsas basin spanning the states of Mich... more Abstract The new species Dioon stevensonii, from the Rio Balsas basin spanning the states of Michoacan and Guerrero, Mexico, is described and illustrated. The de-scription of this species implies a recircumscription of the populations of Dioonthat constitute the previously ...
Canthon cyanellus is a roller dung beetle with a wide distribution range in the tropical forests ... more Canthon cyanellus is a roller dung beetle with a wide distribution range in the tropical forests of the New World. In Mexico, it inhabits the Pacific and the Gulf coasts, the Yucatan Peninsula and the south mainly in the State of Chiapas. This species shows a wide geographical variation in cuticle color, which has been used as defining trait for subspecies. In this study we analyzed the phylogeographic and demographic history of the Mexican populations of C. cyanellus using DNA sequences of the nuclear ITS2, and the mitochondrial COI and 16S genes. We found that not all the current valid subspecies are supported by the molecular analysis. The populations are genetically and geographically structured in five lineages. The diversification events that gave origin to the main lineages within this species complex occurred during the Pleistocine in a time range of 1.63-0.91Myr. The demographic history of these lineages suggests post-glacial expansions toward the middle and the end of the Pleistocene. The combined data of mitochondrial and nuclear DNA suggest that the phylogeographic structure and demographic history of the C. cyanellus populations are the result of: the geological and volcanic activity that occurred from the end of the Pliocene to the Pleistocene; and the contraction and expansion of tropical forests due to the glacial and inter-glacial cycles during the Pleistocene. Landscape changes derived from historical events have affected the demographic history of the populations of this species. The results presented here point to the need to review the taxonomic status and delimitation of the lineages encompassed in the Canthon cyanellus complex.
The study of morphological variation in heterogeneous environments provides evidence for understa... more The study of morphological variation in heterogeneous environments provides evidence for understanding processes that determine the differences between species and interspecific adaptive strategies. In 14 populations of two closely related cycads from the genus Zamia (Zamia loddigesii and Z. prasina), the phenotypic variation was analyzed based on 17 morphological traits, and this variability was correlated with environmental conditions across the populations. Despite the significant inter-population variation observed in the two species, greater inter-specific differences were observed based on generalized linear models. Individuals of all populations except for the Macuspana (Tabasco) population of Z. prasina were separated into two discrete groups in a multivariate space (non-metric multidimensional scaling). Macuspana plants overlapped marginally with the multivariate space defined by plants in the four Z. loddigesii populations. Remarkably, Macuspana is geographically located at the distribution limits of both species that occur in close proximity expressing traits that resemble either of the two species. The heterogeneous environment seems to play a determining role in the phenotypic expression of both species. The variation found could be related to the local ecological adaptions that tend to maximize the populations adaptation. Keywords Co-inertia and multivariate analysis Á Mexico Á Phenotype and environmental variation Á Yucatan peninsula Á Zamia
Dioon angustifolium was considered within D. edule. Recent morphometric and allozyme studies on D... more Dioon angustifolium was considered within D. edule. Recent morphometric and allozyme studies on D. edule have shown that D. angustifolium has originated from geographic isolation and is therefore considered to be a separate species. This cycad is endemic to north-eastern Mexico and is known only from three populations in the Sierra Madre Oriental mountain chain. Its populations are small when compared with its southern relative D. edule. In this study, genetic variation was determined within and between populations of D. angustifolium and the genetic consequences of habitat fragmentation and isolation of populations of this species were assessed. Allozyme electrophoresis of 14 presumptive loci was used. The data were analysed with statistical approximations for estimating genetic diversity, structure, gene flow and recent genetic bottlenecks. Means and standard deviations of genetic diversity estimators were: number of alleles per locus (A = 1.67 +/- 0.23), percentage of polymorphic...
ABSTRACT We have investigated the phylogeographic structure and demographic history of Zamia pauc... more ABSTRACT We have investigated the phylogeographic structure and demographic history of Zamia paucijuga, based on 120 ITS2 and 117 psbK/I sequences from 13 populations distributed along the entire distribution range of the species. We have detected 15 ITS2 and four psbK/I haplotypes, for a total of 19. The genetic diversity estimated for psbK/I was relatively lower than the ITS2 diversity. These results imply that the average genetic diversity in Z. paucijuga is lower in comparison with other cycad species, but relatively higher than the diversity found in conifers. Non-hierarchical and hierarchical AMOVAs for ITS2 and psbK/I showed both low and high levels of genetic structure. This discrepancy likely reflects a decrease in gene flow intensity for seeds but high pollen gene flow, which correlates with the divergent inheritance processes in nuclear vis-à-vis organellar DNAs. SAMOVA tests for both loci (ITS2 and psbK/I) showed high correspondence with the regional geographic structure defined a priori, indicating that the use of both nuclear and chloroplast gene regions improves inferences concerning the evolutionary processes that affect population dynamics in Z. paucijuga. Furthermore, our results are consistent with the conclusions of other studies on the origin of the genus Zamia, which support locating the diversification times of Z. paucijuga populations in the Pleistocene.
Observaciones generales. El orden Cycadales, división Cycadophyta, es un taxón perteneciente al g... more Observaciones generales. El orden Cycadales, división Cycadophyta, es un taxón perteneciente al grupo informal de las gimnospermas dentro de la superdivisión Spermatophyta-reino Plantae, subreino Tracheobionta-. Comprende 10 géneros modernos: Bowenia Hook.
The new species Dioon stevensonii, from the Rio Balsas basin spanning the states of Michoacán and... more The new species Dioon stevensonii, from the Rio Balsas basin spanning the states of Michoacán and Guerrero, Mexico, is described and illustrated. The description of this species implies a recircumscription of the populations of Dioon that constitute the previously characterised D. tomasellii, which also includes populations located in Durango, Nayarit and Jalisco. Dioon stevensonii differs from its congeners in characters of both vegetative and reproductive structures -namely, leaflet contour shape, leaflet curvature and reflection of the megasporophyll tips. Despite its morphological affinities with D. tomasellii, complementary cladistic analyses of molecular matrices indicate that D. stevensonii has closer phylogenetic affinities with the D. edule and D. spinulosum species groups, which are distributed along the Gulf of Mexico and Caribbean seaboards. The proposal of D. stevensonii rests on the reevaluation of overlooked differences in morphological character states in herbarium material, corresponding to populations previously identified as D. tomasellii, which were confirmed after ex profeso field collections. The fact that such re-evaluation was prompted by a hypothesis of relationships based on molecular data for the entire genus Dioon, establishes the proposal of D. stevensonii as an unusual case of reciprocal illumination, where the morphological evidence provided confirmation of a molecular hypothesis, and not vice versa.
The cycad Ceratozamia mirandae is endemic to Chiapas, Mexico. Demographic studies were made in tw... more The cycad Ceratozamia mirandae is endemic to Chiapas, Mexico. Demographic studies were made in two of its populations in the Sepultura Biosphere Reserve under different conservation conditions; in the nucleus zone ''Tres Picos'' (conserved) and buffer zone ''La Sombra'' (disturbed and under management). Spatial distribution of C. mirandae was aggregated, showed a clumped local distribution on shallow soils on steep slopes and male and female cones appear to be synchronous in both populations. The population structure was of type I (Bongers) for both sites. Individuals between the sites showed differences in growth pattern. The oldest plants (80-90 cm tall) were estimated to be about 490 years at ''La Sombra''. The finite growth rate (k) in the buffer zone population showed a tendency for decrease whilst in the nucleus zone this estimate remained stable. The highest elasticity values lied in the transition of the first three classes of the ''La Sombra'' population, in ''Tres Picos'' this corresponded to adult plants between 20 and 30 cm tall. Given the above, it is proposed that in the nucleus zone, reproductive adults should be of highest conservation priority, whereas in the buffer zone seedling reintroduction should be carried out regularly until the population increases. We recommend an IUCN Red List category of Vulnerable (VU C, 2a), largely due to difficult-to-control destructive annual forest fires that occur in this Reserve.
Ceratozamia decumbens (Zamiaceae, Cycadales) is newly described and illustrated. This species, en... more Ceratozamia decumbens (Zamiaceae, Cycadales) is newly described and illustrated. This species, endemic to Veracruz, has affinity with C. morettii Vázquez Torres & Vovides, but differs in leaf morphology and leaflet habit as well as in the microsporangiate and megasporangiate strobili and trunk. Ceratozamia decumbens is considered part of the C. latifolia species complex, which includes C.
Background and aims: With the recent proposal of matK and rbcL as core plant DNA barcoding region... more Background and aims: With the recent proposal of matK and rbcL as core plant DNA barcoding regions by the Consortium for the Barcoding of Life Plant Working Group, the construction of reference libraries in the botanical DNA barcoding initiative has entered a new phase. However, in a recent DNA barcoding study in the three Mexican genera of the gymnosperm order Cycadales, we found that neither matK nor rbcL allow high levels of molecular identification of previously established species. Materials and methods: Our data analysis in that study rested on the "Characteristic Attributes Organization System" (CAOS), a character-based algorithm for the definition of "DNA diagnostics." Here, we use CAOS to analyze a population-level molecular data set in Zamia, one of the three cycad genera occurring in Mexico, whose populations display contrasting biogeographic patterns. Our population-level study, which includes all species in the region formally known as Megamexico, is restricted to the genome region, which showed the best single-locus molecular identification performance in our previous study-namely, the noncoding intergenic chloroplast spacer psbK-I. Results: Our comparison of single-individual vs. population-level psbK-I datasets in Zamia indicates that CAOS analyses are sensitive to slight alignment changes, which in turn derive from the different amounts of molecular variation present in each matrix type. Conclusion: We, therefore, suggest that character-based studies that involve population-level data should contemplate this type of comparison between data matrices, before a set of DNA diagnostics in a given DNA barcoding reference library is considered definitive.
A DNA barcoding study was conducted to determine the optimal combination of loci needed for succe... more A DNA barcoding study was conducted to determine the optimal combination of loci needed for successful species-level molecular identification in three extant cycad genera-Ceratozamia, Dioon, and Zamia-that occur in Mexico. Based on conclusions of a previous multigene study in representative species of all genera in the Cycadales, we tested the DNA barcoding performance of seven chloroplast coding (matK, rpoB, rpoC1, and rbcL) and non-coding (atpF ⁄ H, psbK ⁄ I, and trnH-psbA) regions, plus sequences of the nuclear internal transcribed spacer. We analysed data under the assumptions of the ''character attributes organization system'' (CAOS), a character-based approach in which species are identified through the presence of ÔDNA diagnosticsÕ. In Ceratozamia, four chloroplast regions and one nuclear region were needed to achieve > 70% unique species identification. In contrast, the two-gene combination atpF ⁄ H + psbK ⁄ I and the four-gene combination atpF ⁄ H + psbK ⁄ I + rpoC1 + ITS2 were needed to reach 79% and 75% unique species identification in Dioon and Zamia, respectively. The combinations atpF ⁄ H + psbK ⁄ I and atpF ⁄ H + psbK ⁄ I + rpoC1 + ITS2 include loci previously considered by the international DNA barcoding community. However, none of the three combinations of potential DNA barcoding loci found to be optimal with a character-based approach in the Mexican cycads coincides with the Ôcore barcodeÕ of chloroplast markers (matK + rbcL) recently proposed for universal use in the plant kingdom.
The new species Ceratozamia vovidesii from a Pleistocene floristic refuge in southern Mexico is d... more The new species Ceratozamia vovidesii from a Pleistocene floristic refuge in southern Mexico is described and illustrated. It show an affinity with C. matudae Lundell and C. mirandae Vovides, Pérez-Farrera & Iglesias from Chiapas, but it differs from them in leaf, male and female cones, and trunk morphology.
The genetic diversity and structure of four populations of the cycad Zamia loddigesii were studie... more The genetic diversity and structure of four populations of the cycad Zamia loddigesii were studied throughout its range in Mexico. Allozyme electrophoresis of 15 loci was conducted. The mean number of alleles per locus was 1.80 ± 0.09, the percentage of polymorphic loci was 66.6 ...
Ceratozamia chimalapensis sp. nov. is described and illustrated. It is related to C. mirandae Vov... more Ceratozamia chimalapensis sp. nov. is described and illustrated. It is related to C. mirandae Vovides, Pérez-Farrera & Iglesias from Chiapas, but differs in trunk and peduncle size as well as in diameter of both megastrobili and microstrobili. Petiole, megasporophyll and indument colour also differ from that of C. mirandae. Ceratozamia chimalapensis forms part of the C. norstogii D.W.Stev. species complex, a group of ceratozamias with narrow leaflets growing in the herbaceous layer of oak forests in southern Mexico. These forests were severely affected by forest fires during 1998 and we recommend an IUCN Red List Category of CR B.1. Speciation in Ceratozamia has been discussed in the light of floristic refugia.
The demographic dynamics of three populations of Dioon edule Lindl. (Zamiaceae) were studied in a... more The demographic dynamics of three populations of Dioon edule Lindl. (Zamiaceae) were studied in a fragmented landscape using projection matrix modelling. Compared with other plant species, D. edule behaves like a tree life-form species. Density and spatial distribution patterns varied among populations according to models for animal-dispersed tree species. In all scenarios, l was most sensitive to changes in abundance of adult plants. The elasticity reproductive component (F) for the three populations was zero and stasis values (L) were higher, this being a function of the permanence of non-reproductive individuals. It was detected that disturbance influences the population dynamics of D. edule as a function of adult plant persistence. This observation suggests that the conservation of adult plants is critical for D. edule and perhaps for all cycads species. Adult plant decapitation should be halted at the 'Monte Oscuro' population, subjected to sustainable management since 1990, if higher seed production is needed in rural nurseries.
Dioon edule Lindl. (Zamiaceae) is a cycad endemic to Mexico, that occurs as one species D. edule ... more Dioon edule Lindl. (Zamiaceae) is a cycad endemic to Mexico, that occurs as one species D. edule and the geographical variety D. edule var. angustifolium (Miq.) Miq. Dioon edule has a north to south distribution in eastern Mexico. In this study, we analysed 14 allozymic loci in eight populations of D. edule from its total distribution range by sampling all known populations. Patterns of diversity and genetic variability, within and among populations, were obtained. The mean number of alleles per locus (A) was 1.44 and the percentage of polymorphic loci was relatively high (P = 54.78). The mean observed (H O) and expected heterozygosity (H E) were 0.27 and 0.24, respectively. F-statistics revealed an excess of heterozygous genotypes, locally and globally (F =-0.17 and f =-0.27, respectively). The genetic variation explained by differences among populations was only 7.5%. We also detected a negative relationship between genetic diversity and latitude. On average, the gene flow between population pairs was relatively high (Nm = 2.98); furthermore, gene flow between population pairs was significantly correlated with geographical distances (r =-0.38, P = 0.025). Therefore, patterns of genetic diversity in D. edule appear to be associated with the post-Pleistocene spread of the species, from its southerly (origin) to its northerly range (derived populations, including its central distribution). The biogeographical and evolutionary aspects of the results of this study are discussed. We recognize Dioon angustifolium Miq. for the northernmost disjunct populations.
Page 1. Diversity and genetic structure of three species of Dioon Lindl. (Zamiaceae, Cycadales) f... more Page 1. Diversity and genetic structure of three species of Dioon Lindl. (Zamiaceae, Cycadales) from the Pacific seaboard of Mexico JORGE GONZÁLEZ-ASTORGA1*, FRANCISCO VERGARA-SILVA1,3, ANDREW P. VOVIDES2 ...
... conservation implications. Jorge González-Astorga a , Corresponding Author Contact Informatio... more ... conservation implications. Jorge González-Astorga a , Corresponding Author Contact Information , E-mail The Corresponding Author , Andrew P. Vovides b , Dánae Cabrera-Toledo a and Fernando Nicolalde-Morejón b. a Laboratorio ...
The diversity and genetic structure of seven populations of Microcycas calocoma (Miq.) A. DC, wer... more The diversity and genetic structure of seven populations of Microcycas calocoma (Miq.) A. DC, were analyzed by gel electrophoresis using 19 allozymes. The mean number of alleles per locus (A) was 1.49 and the percentage of polymorphic loci was relatively high (P ¼ 48.09). The mean observed (H o) and expected heterozygosity (H e) were 0.20 and 0.17, respectively. The F-statistics revealed a high population structure (F ST ¼ 0.34). Mean gene flow between population pairs was Nm ¼ 0.96. Results were compared with those of other cycad species, and indicate that M. calocoma populations have become fragmented due to increasing pressures of habitat conversion and disturbance. Also, geographical isolation among populations has generated allele loss in relation to altitude. The establishment and maintenance of protected areas for in situ conservation is critical to preserve the high genetic diversity of M. calocoma. Conservation strategy guidelines have been specified.
Abstract The new species Dioon stevensonii, from the Rio Balsas basin spanning the states of Mich... more Abstract The new species Dioon stevensonii, from the Rio Balsas basin spanning the states of Michoacan and Guerrero, Mexico, is described and illustrated. The de-scription of this species implies a recircumscription of the populations of Dioonthat constitute the previously ...
Canthon cyanellus is a roller dung beetle with a wide distribution range in the tropical forests ... more Canthon cyanellus is a roller dung beetle with a wide distribution range in the tropical forests of the New World. In Mexico, it inhabits the Pacific and the Gulf coasts, the Yucatan Peninsula and the south mainly in the State of Chiapas. This species shows a wide geographical variation in cuticle color, which has been used as defining trait for subspecies. In this study we analyzed the phylogeographic and demographic history of the Mexican populations of C. cyanellus using DNA sequences of the nuclear ITS2, and the mitochondrial COI and 16S genes. We found that not all the current valid subspecies are supported by the molecular analysis. The populations are genetically and geographically structured in five lineages. The diversification events that gave origin to the main lineages within this species complex occurred during the Pleistocine in a time range of 1.63-0.91Myr. The demographic history of these lineages suggests post-glacial expansions toward the middle and the end of the Pleistocene. The combined data of mitochondrial and nuclear DNA suggest that the phylogeographic structure and demographic history of the C. cyanellus populations are the result of: the geological and volcanic activity that occurred from the end of the Pliocene to the Pleistocene; and the contraction and expansion of tropical forests due to the glacial and inter-glacial cycles during the Pleistocene. Landscape changes derived from historical events have affected the demographic history of the populations of this species. The results presented here point to the need to review the taxonomic status and delimitation of the lineages encompassed in the Canthon cyanellus complex.
The study of morphological variation in heterogeneous environments provides evidence for understa... more The study of morphological variation in heterogeneous environments provides evidence for understanding processes that determine the differences between species and interspecific adaptive strategies. In 14 populations of two closely related cycads from the genus Zamia (Zamia loddigesii and Z. prasina), the phenotypic variation was analyzed based on 17 morphological traits, and this variability was correlated with environmental conditions across the populations. Despite the significant inter-population variation observed in the two species, greater inter-specific differences were observed based on generalized linear models. Individuals of all populations except for the Macuspana (Tabasco) population of Z. prasina were separated into two discrete groups in a multivariate space (non-metric multidimensional scaling). Macuspana plants overlapped marginally with the multivariate space defined by plants in the four Z. loddigesii populations. Remarkably, Macuspana is geographically located at the distribution limits of both species that occur in close proximity expressing traits that resemble either of the two species. The heterogeneous environment seems to play a determining role in the phenotypic expression of both species. The variation found could be related to the local ecological adaptions that tend to maximize the populations adaptation. Keywords Co-inertia and multivariate analysis Á Mexico Á Phenotype and environmental variation Á Yucatan peninsula Á Zamia
Dioon angustifolium was considered within D. edule. Recent morphometric and allozyme studies on D... more Dioon angustifolium was considered within D. edule. Recent morphometric and allozyme studies on D. edule have shown that D. angustifolium has originated from geographic isolation and is therefore considered to be a separate species. This cycad is endemic to north-eastern Mexico and is known only from three populations in the Sierra Madre Oriental mountain chain. Its populations are small when compared with its southern relative D. edule. In this study, genetic variation was determined within and between populations of D. angustifolium and the genetic consequences of habitat fragmentation and isolation of populations of this species were assessed. Allozyme electrophoresis of 14 presumptive loci was used. The data were analysed with statistical approximations for estimating genetic diversity, structure, gene flow and recent genetic bottlenecks. Means and standard deviations of genetic diversity estimators were: number of alleles per locus (A = 1.67 +/- 0.23), percentage of polymorphic...
ABSTRACT We have investigated the phylogeographic structure and demographic history of Zamia pauc... more ABSTRACT We have investigated the phylogeographic structure and demographic history of Zamia paucijuga, based on 120 ITS2 and 117 psbK/I sequences from 13 populations distributed along the entire distribution range of the species. We have detected 15 ITS2 and four psbK/I haplotypes, for a total of 19. The genetic diversity estimated for psbK/I was relatively lower than the ITS2 diversity. These results imply that the average genetic diversity in Z. paucijuga is lower in comparison with other cycad species, but relatively higher than the diversity found in conifers. Non-hierarchical and hierarchical AMOVAs for ITS2 and psbK/I showed both low and high levels of genetic structure. This discrepancy likely reflects a decrease in gene flow intensity for seeds but high pollen gene flow, which correlates with the divergent inheritance processes in nuclear vis-à-vis organellar DNAs. SAMOVA tests for both loci (ITS2 and psbK/I) showed high correspondence with the regional geographic structure defined a priori, indicating that the use of both nuclear and chloroplast gene regions improves inferences concerning the evolutionary processes that affect population dynamics in Z. paucijuga. Furthermore, our results are consistent with the conclusions of other studies on the origin of the genus Zamia, which support locating the diversification times of Z. paucijuga populations in the Pleistocene.
Observaciones generales. El orden Cycadales, división Cycadophyta, es un taxón perteneciente al g... more Observaciones generales. El orden Cycadales, división Cycadophyta, es un taxón perteneciente al grupo informal de las gimnospermas dentro de la superdivisión Spermatophyta-reino Plantae, subreino Tracheobionta-. Comprende 10 géneros modernos: Bowenia Hook.
The new species Dioon stevensonii, from the Rio Balsas basin spanning the states of Michoacán and... more The new species Dioon stevensonii, from the Rio Balsas basin spanning the states of Michoacán and Guerrero, Mexico, is described and illustrated. The description of this species implies a recircumscription of the populations of Dioon that constitute the previously characterised D. tomasellii, which also includes populations located in Durango, Nayarit and Jalisco. Dioon stevensonii differs from its congeners in characters of both vegetative and reproductive structures -namely, leaflet contour shape, leaflet curvature and reflection of the megasporophyll tips. Despite its morphological affinities with D. tomasellii, complementary cladistic analyses of molecular matrices indicate that D. stevensonii has closer phylogenetic affinities with the D. edule and D. spinulosum species groups, which are distributed along the Gulf of Mexico and Caribbean seaboards. The proposal of D. stevensonii rests on the reevaluation of overlooked differences in morphological character states in herbarium material, corresponding to populations previously identified as D. tomasellii, which were confirmed after ex profeso field collections. The fact that such re-evaluation was prompted by a hypothesis of relationships based on molecular data for the entire genus Dioon, establishes the proposal of D. stevensonii as an unusual case of reciprocal illumination, where the morphological evidence provided confirmation of a molecular hypothesis, and not vice versa.
The cycad Ceratozamia mirandae is endemic to Chiapas, Mexico. Demographic studies were made in tw... more The cycad Ceratozamia mirandae is endemic to Chiapas, Mexico. Demographic studies were made in two of its populations in the Sepultura Biosphere Reserve under different conservation conditions; in the nucleus zone ''Tres Picos'' (conserved) and buffer zone ''La Sombra'' (disturbed and under management). Spatial distribution of C. mirandae was aggregated, showed a clumped local distribution on shallow soils on steep slopes and male and female cones appear to be synchronous in both populations. The population structure was of type I (Bongers) for both sites. Individuals between the sites showed differences in growth pattern. The oldest plants (80-90 cm tall) were estimated to be about 490 years at ''La Sombra''. The finite growth rate (k) in the buffer zone population showed a tendency for decrease whilst in the nucleus zone this estimate remained stable. The highest elasticity values lied in the transition of the first three classes of the ''La Sombra'' population, in ''Tres Picos'' this corresponded to adult plants between 20 and 30 cm tall. Given the above, it is proposed that in the nucleus zone, reproductive adults should be of highest conservation priority, whereas in the buffer zone seedling reintroduction should be carried out regularly until the population increases. We recommend an IUCN Red List category of Vulnerable (VU C, 2a), largely due to difficult-to-control destructive annual forest fires that occur in this Reserve.
Ceratozamia decumbens (Zamiaceae, Cycadales) is newly described and illustrated. This species, en... more Ceratozamia decumbens (Zamiaceae, Cycadales) is newly described and illustrated. This species, endemic to Veracruz, has affinity with C. morettii Vázquez Torres & Vovides, but differs in leaf morphology and leaflet habit as well as in the microsporangiate and megasporangiate strobili and trunk. Ceratozamia decumbens is considered part of the C. latifolia species complex, which includes C.
Background and aims: With the recent proposal of matK and rbcL as core plant DNA barcoding region... more Background and aims: With the recent proposal of matK and rbcL as core plant DNA barcoding regions by the Consortium for the Barcoding of Life Plant Working Group, the construction of reference libraries in the botanical DNA barcoding initiative has entered a new phase. However, in a recent DNA barcoding study in the three Mexican genera of the gymnosperm order Cycadales, we found that neither matK nor rbcL allow high levels of molecular identification of previously established species. Materials and methods: Our data analysis in that study rested on the "Characteristic Attributes Organization System" (CAOS), a character-based algorithm for the definition of "DNA diagnostics." Here, we use CAOS to analyze a population-level molecular data set in Zamia, one of the three cycad genera occurring in Mexico, whose populations display contrasting biogeographic patterns. Our population-level study, which includes all species in the region formally known as Megamexico, is restricted to the genome region, which showed the best single-locus molecular identification performance in our previous study-namely, the noncoding intergenic chloroplast spacer psbK-I. Results: Our comparison of single-individual vs. population-level psbK-I datasets in Zamia indicates that CAOS analyses are sensitive to slight alignment changes, which in turn derive from the different amounts of molecular variation present in each matrix type. Conclusion: We, therefore, suggest that character-based studies that involve population-level data should contemplate this type of comparison between data matrices, before a set of DNA diagnostics in a given DNA barcoding reference library is considered definitive.
A DNA barcoding study was conducted to determine the optimal combination of loci needed for succe... more A DNA barcoding study was conducted to determine the optimal combination of loci needed for successful species-level molecular identification in three extant cycad genera-Ceratozamia, Dioon, and Zamia-that occur in Mexico. Based on conclusions of a previous multigene study in representative species of all genera in the Cycadales, we tested the DNA barcoding performance of seven chloroplast coding (matK, rpoB, rpoC1, and rbcL) and non-coding (atpF ⁄ H, psbK ⁄ I, and trnH-psbA) regions, plus sequences of the nuclear internal transcribed spacer. We analysed data under the assumptions of the ''character attributes organization system'' (CAOS), a character-based approach in which species are identified through the presence of ÔDNA diagnosticsÕ. In Ceratozamia, four chloroplast regions and one nuclear region were needed to achieve > 70% unique species identification. In contrast, the two-gene combination atpF ⁄ H + psbK ⁄ I and the four-gene combination atpF ⁄ H + psbK ⁄ I + rpoC1 + ITS2 were needed to reach 79% and 75% unique species identification in Dioon and Zamia, respectively. The combinations atpF ⁄ H + psbK ⁄ I and atpF ⁄ H + psbK ⁄ I + rpoC1 + ITS2 include loci previously considered by the international DNA barcoding community. However, none of the three combinations of potential DNA barcoding loci found to be optimal with a character-based approach in the Mexican cycads coincides with the Ôcore barcodeÕ of chloroplast markers (matK + rbcL) recently proposed for universal use in the plant kingdom.
The new species Ceratozamia vovidesii from a Pleistocene floristic refuge in southern Mexico is d... more The new species Ceratozamia vovidesii from a Pleistocene floristic refuge in southern Mexico is described and illustrated. It show an affinity with C. matudae Lundell and C. mirandae Vovides, Pérez-Farrera & Iglesias from Chiapas, but it differs from them in leaf, male and female cones, and trunk morphology.
The genetic diversity and structure of four populations of the cycad Zamia loddigesii were studie... more The genetic diversity and structure of four populations of the cycad Zamia loddigesii were studied throughout its range in Mexico. Allozyme electrophoresis of 15 loci was conducted. The mean number of alleles per locus was 1.80 ± 0.09, the percentage of polymorphic loci was 66.6 ...
Ceratozamia chimalapensis sp. nov. is described and illustrated. It is related to C. mirandae Vov... more Ceratozamia chimalapensis sp. nov. is described and illustrated. It is related to C. mirandae Vovides, Pérez-Farrera & Iglesias from Chiapas, but differs in trunk and peduncle size as well as in diameter of both megastrobili and microstrobili. Petiole, megasporophyll and indument colour also differ from that of C. mirandae. Ceratozamia chimalapensis forms part of the C. norstogii D.W.Stev. species complex, a group of ceratozamias with narrow leaflets growing in the herbaceous layer of oak forests in southern Mexico. These forests were severely affected by forest fires during 1998 and we recommend an IUCN Red List Category of CR B.1. Speciation in Ceratozamia has been discussed in the light of floristic refugia.
The demographic dynamics of three populations of Dioon edule Lindl. (Zamiaceae) were studied in a... more The demographic dynamics of three populations of Dioon edule Lindl. (Zamiaceae) were studied in a fragmented landscape using projection matrix modelling. Compared with other plant species, D. edule behaves like a tree life-form species. Density and spatial distribution patterns varied among populations according to models for animal-dispersed tree species. In all scenarios, l was most sensitive to changes in abundance of adult plants. The elasticity reproductive component (F) for the three populations was zero and stasis values (L) were higher, this being a function of the permanence of non-reproductive individuals. It was detected that disturbance influences the population dynamics of D. edule as a function of adult plant persistence. This observation suggests that the conservation of adult plants is critical for D. edule and perhaps for all cycads species. Adult plant decapitation should be halted at the 'Monte Oscuro' population, subjected to sustainable management since 1990, if higher seed production is needed in rural nurseries.
Dioon edule Lindl. (Zamiaceae) is a cycad endemic to Mexico, that occurs as one species D. edule ... more Dioon edule Lindl. (Zamiaceae) is a cycad endemic to Mexico, that occurs as one species D. edule and the geographical variety D. edule var. angustifolium (Miq.) Miq. Dioon edule has a north to south distribution in eastern Mexico. In this study, we analysed 14 allozymic loci in eight populations of D. edule from its total distribution range by sampling all known populations. Patterns of diversity and genetic variability, within and among populations, were obtained. The mean number of alleles per locus (A) was 1.44 and the percentage of polymorphic loci was relatively high (P = 54.78). The mean observed (H O) and expected heterozygosity (H E) were 0.27 and 0.24, respectively. F-statistics revealed an excess of heterozygous genotypes, locally and globally (F =-0.17 and f =-0.27, respectively). The genetic variation explained by differences among populations was only 7.5%. We also detected a negative relationship between genetic diversity and latitude. On average, the gene flow between population pairs was relatively high (Nm = 2.98); furthermore, gene flow between population pairs was significantly correlated with geographical distances (r =-0.38, P = 0.025). Therefore, patterns of genetic diversity in D. edule appear to be associated with the post-Pleistocene spread of the species, from its southerly (origin) to its northerly range (derived populations, including its central distribution). The biogeographical and evolutionary aspects of the results of this study are discussed. We recognize Dioon angustifolium Miq. for the northernmost disjunct populations.
Page 1. Diversity and genetic structure of three species of Dioon Lindl. (Zamiaceae, Cycadales) f... more Page 1. Diversity and genetic structure of three species of Dioon Lindl. (Zamiaceae, Cycadales) from the Pacific seaboard of Mexico JORGE GONZÁLEZ-ASTORGA1*, FRANCISCO VERGARA-SILVA1,3, ANDREW P. VOVIDES2 ...
... conservation implications. Jorge González-Astorga a , Corresponding Author Contact Informatio... more ... conservation implications. Jorge González-Astorga a , Corresponding Author Contact Information , E-mail The Corresponding Author , Andrew P. Vovides b , Dánae Cabrera-Toledo a and Fernando Nicolalde-Morejón b. a Laboratorio ...
The diversity and genetic structure of seven populations of Microcycas calocoma (Miq.) A. DC, wer... more The diversity and genetic structure of seven populations of Microcycas calocoma (Miq.) A. DC, were analyzed by gel electrophoresis using 19 allozymes. The mean number of alleles per locus (A) was 1.49 and the percentage of polymorphic loci was relatively high (P ¼ 48.09). The mean observed (H o) and expected heterozygosity (H e) were 0.20 and 0.17, respectively. The F-statistics revealed a high population structure (F ST ¼ 0.34). Mean gene flow between population pairs was Nm ¼ 0.96. Results were compared with those of other cycad species, and indicate that M. calocoma populations have become fragmented due to increasing pressures of habitat conversion and disturbance. Also, geographical isolation among populations has generated allele loss in relation to altitude. The establishment and maintenance of protected areas for in situ conservation is critical to preserve the high genetic diversity of M. calocoma. Conservation strategy guidelines have been specified.
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