**Abstract**

The distribution of the endangered species *Dioon edule* is in populations scattered throughout the Sierra Madre Oriental in San Luis Potosí, Mexico. Its habitat is tropical dry forests at lower elevations and oak forests at higher elevations, mainly disturbed by anthropic activities. We determined and analyzed nine populations' demographic structure and explored the genetic diversity of five using SSR markers. The population density averaged 2050 individuals ha-1 and have an aggregated distribution pattern. Differences in the plants' size among localities are due to site quality, based on their adaptation capacity and response to climate and soil traits. Most populations have the highest mortality in the early stages of life, with a low mortality rate for those who survive this bottleneck. Two populations have a relatively constant mortality rate, attributed to disturbance of the habitat. The populations show low genetic diversity and an excess of homozygotes. Their similarity is probably related to the formation of natural corridors favoring connectivity between populations. The deterioration and fragmentation of the habitat have severe effects on the populations' viability, like reducing gene flow, which has led to inbreeding and genetic drift.

**Keywords:** Zamiaceae, cycads, gymnosperms, ecotone, dioecious, habitat disturbance, inbreeding, Mexico, population, gene flow

## **1. Introduction**

The relevance of the species *Dioon edule* (Zamiaceae) is evolutive because it belongs to a group of plants whose origin can be traced back to 250 million years ago, allowing us to understand the adaptations developed to survive the present day. It is also ecologically relevant as it is scattered in a wide range of ecosystems, from coastal dunes in the Gulf of Mexico's coastal plain to pine forest in the Sierra Madre Oriental, and its interactions with symbiotic micro-organisms, pollinating insects, and predator-dispersing wild and domestic fauna. The region's cultural relevance is defined by the Xi'iuy ethnic group in San Luis Potosí, collecting the seeds for food and the leaves for ceremonies [1].

This species is distributed in the Sierra Madre Oriental (SMO), within the geographic-cultural region known as La Huasteca, including the south of Tamaulipas, east of San Luis Potosi, Hidalgo, Queretaro, and Veracruz. The elevation goes from sea level to 1525 meters above sea level (m.a.s.l.) [2, 3]. It has stems up to 6 m high in some occasions semi-prostrated, presenting reproductive events with an interval of 10 to 52 years in female individuals and 2.8 to 8.8 in male individuals [4]. Its strobilus is pollinated only by specialist insects (beetles) associated with them [5].

The species is currently classified as near threatened (NT) by International Union for Conservation of Nature and endangered by the NOM-059-SEMARNAT-2010 in Mexico. This category is mainly because of land-use change to agriculture and livestock, causing habitat fragmentation that adversely affects population dynamics and a possible reduction in gene flow among populations [4, 6].

It is necessary to integrate information from different areas, mainly demography and population genetics, to develop and implement effective conservation strategies [6] to build general conclusions from the observations derived from each of these areas.

Demographic studies provide the basis for knowledge of populations and allow us to assess populations' viability, identify factors that reduce the population, and predict the persistence of small, isolated populations and evaluate alternative conservation scenarios [7]. Population genetics allows us to describe the genetic composition of natural populations and predict their changes in response to various evolutionary forces operating on them, allowing us to identify some risks of a genetic nature that affect the persistence of species such as habitat fragmentation and loss of adaptive potential associated with the decline of genetic diversity and inbreeding [8, 9]. Diverse studies related to population genetics and genomics of cycads have been published based on molecular markers such as Aloenzymes, RADseq, chloroplast markers, ISSR [4, 10–15].

The objective of this research was to study the demographic and genetic status of *Dioon edule* Lindl. (Zamiaceae) in representative natural populations of the Sierra Madre Oriental in the state of San Luis Potosi, analyzing their population structure concerning their density, age structure, sex ratio, as well as genetic diversity.

### **2. Materials and methods**

#### **2.1 Study area**

The Sierra Madre Oriental is fundamentally a group of minor mountain ranges formed by marine sedimentary rocks, mainly limestone, sandstone, and shales. The maximum elevations are up to 3180 m.a.s.l., with small intermontane valleys limited by high mountain ranges with steep slopes (**Figure 1**). In this region, there are soils of alluvial origin formed in the great plains with sediments mostly coming from limestone and lutites and residual and colluvial origin in the high and lower parts of the mountain ranges constituted by the same type of rock. In general, the soil is medium texture, shallow, and rich in organic matter and nutrients depending on the climate and vegetation [16]. The area's climate is semi-warm, characterized by average annual temperatures above 18 °C and 600 mm of rainfall, mostly during the summer [16].

In the state of San Luis Potosi, three important vegetation regions for cycads stand out [16]: Tamasopo with tropical rain forest and oak forest (*Quercus* spp.); Aquismón with tropical rain forest; and, Rayón and Santa Catarina with oak forest, and piedmont scrub.

**97**

**2.2 Demography**

**Figure 1.**

*The Endangered Species* Dioon edule *in the Sierra Madre Oriental in San Luis Potosí…*

The study of demography was conducted in nine populations of *Dioon edule* distributed in the sub-province of Carso Huasteco (**Figure 1**) that covers 15.52% of the total surface of San Luis Potosi. It is formed almost exclusively by mountain ranges with soils of residual origin, shallow (less than 10 cm), with abundant rocky outcrops and Lithic phase. We do not provide detailed information on populations'

The sampling consists of modifying the line interception method [17] and used by [18] in transects of 30 m long and 10 m wide. Rectangular units provide the advantage of evaluating variables by walking in a straight line without moving

locations to avoid possible looting, so each one has a key with two letters.

*Study area in the Sierra Madre oriental of San Luis Potosí, Mexico.*

*DOI: http://dx.doi.org/10.5772/intechopen.96372*

*The Endangered Species* Dioon edule *in the Sierra Madre Oriental in San Luis Potosí… DOI: http://dx.doi.org/10.5772/intechopen.96372*

**Figure 1.** *Study area in the Sierra Madre oriental of San Luis Potosí, Mexico.*

#### **2.2 Demography**

The study of demography was conducted in nine populations of *Dioon edule* distributed in the sub-province of Carso Huasteco (**Figure 1**) that covers 15.52% of the total surface of San Luis Potosi. It is formed almost exclusively by mountain ranges with soils of residual origin, shallow (less than 10 cm), with abundant rocky outcrops and Lithic phase. We do not provide detailed information on populations' locations to avoid possible looting, so each one has a key with two letters.

The sampling consists of modifying the line interception method [17] and used by [18] in transects of 30 m long and 10 m wide. Rectangular units provide the advantage of evaluating variables by walking in a straight line without moving

*Natural History and Ecology of Mexico and Central America*

This species is distributed in the Sierra Madre Oriental (SMO), within the geographic-cultural region known as La Huasteca, including the south of Tamaulipas, east of San Luis Potosi, Hidalgo, Queretaro, and Veracruz. The elevation goes from sea level to 1525 meters above sea level (m.a.s.l.) [2, 3]. It has stems up to 6 m high in some occasions semi-prostrated, presenting reproductive events with an interval of 10 to 52 years in female individuals and 2.8 to 8.8 in male individuals [4]. Its strobilus is pollinated only by specialist insects (beetles) associated with them [5].

The species is currently classified as near threatened (NT) by International Union

It is necessary to integrate information from different areas, mainly demography and population genetics, to develop and implement effective conservation strategies [6] to build general conclusions from the observations derived from each of

Demographic studies provide the basis for knowledge of populations and allow

The objective of this research was to study the demographic and genetic status of *Dioon edule* Lindl. (Zamiaceae) in representative natural populations of the Sierra Madre Oriental in the state of San Luis Potosi, analyzing their population structure concerning their density, age structure, sex ratio, as well as genetic diversity.

The Sierra Madre Oriental is fundamentally a group of minor mountain ranges formed by marine sedimentary rocks, mainly limestone, sandstone, and shales. The maximum elevations are up to 3180 m.a.s.l., with small intermontane valleys limited by high mountain ranges with steep slopes (**Figure 1**). In this region, there are soils of alluvial origin formed in the great plains with sediments mostly coming from limestone and lutites and residual and colluvial origin in the high and lower parts of the mountain ranges constituted by the same type of rock. In general, the soil is medium texture, shallow, and rich in organic matter and nutrients depending on the climate and vegetation [16]. The area's climate is semi-warm, characterized by average annual temperatures above 18 °C and 600 mm of rainfall, mostly during

In the state of San Luis Potosi, three important vegetation regions for cycads stand out [16]: Tamasopo with tropical rain forest and oak forest (*Quercus* spp.); Aquismón with tropical rain forest; and, Rayón and Santa Catarina with oak forest,

us to assess populations' viability, identify factors that reduce the population, and predict the persistence of small, isolated populations and evaluate alternative conservation scenarios [7]. Population genetics allows us to describe the genetic composition of natural populations and predict their changes in response to various evolutionary forces operating on them, allowing us to identify some risks of a genetic nature that affect the persistence of species such as habitat fragmentation and loss of adaptive potential associated with the decline of genetic diversity and inbreeding [8, 9]. Diverse studies related to population genetics and genomics of cycads have been published based on molecular markers such as Aloenzymes,

for Conservation of Nature and endangered by the NOM-059-SEMARNAT-2010 in Mexico. This category is mainly because of land-use change to agriculture and livestock, causing habitat fragmentation that adversely affects population dynamics

and a possible reduction in gene flow among populations [4, 6].

RADseq, chloroplast markers, ISSR [4, 10–15].

**2. Materials and methods**

**2.1 Study area**

the summer [16].

and piedmont scrub.

**96**

these areas.

sideways, starting at one end of the line, and considering only those plants within the plot [19]. Due to the harsh characteristics of the area with rocky slopes of up to 70°, we traced two linear transects 100 m long by 2 m wide, parallel to the slope, locating them where the most significant number of individuals were concentrated, considering that *D. edule* populations present an aggregate distribution [18]. Each transect was divided into four 25 m long subunits to carry out the plants' counts and measurements.

The different stages of the cycads' life cycle were defined according to the number of leaves, the number of leaflets and stem height [7] because it has not yet been possible to define the age of the cycads due to their growth characteristics [18]. Therefore, individuals were classified as follows: seedlings, individuals that present one or more leaves without these forming a crown; juveniles, individuals that present one or more crowns, but with a non-visible stem; adults, individuals that present one or more crowns and have a visible stem. Adults were classified as male, female, or non-reproductive according to the presence of reproductive structures.

Once the cycads' life cycle stages were defined, each stage's survival probabilities calculation as the proportion of individuals that survived to enter the next category, relative to the initial number of seeds (lx = nx/n0) [20]. A survival curve describes the survival pattern of individuals in a population over time, plotting the lx on the y-axis, in logarithmic scale, with life cycle stages on the x-axis There are three basic survival curves, the survival curve type I represents a population in which most of the organisms die in the older age categories. The type II curve represents a population in which the mortality rate is almost constant, and type III represents a population in which most individuals die during the first stages of the life cycle, and very few reach the intermediate and late age categories [20].

The stem's diameter and the plant's total height were measured, the total number of leaves was counted, and the length of those on the last crown was measured.

Considering that the species *D. edule* is dioecious and produce only one cone per reproductive event, we evaluated the number of plants with male and female cones present as a measure of the potential reproductive capacity of the population per reproductive event [21].

The data on population density and potential reproductive capacity was analyzed using a one-way Analysis of Variance (ANOVA) to determine the statistical difference among the nine populations studied (localities) with two transects in each (n = 18).

Data on plant size and number of leaves of individuals in reproductive and nonreproductive states were analyzed through a nested ANOVA (random-effects model II) to determine the statistical difference among localities and categories of plants' reproductive states in all localities and each location. When statistically significant differences between means occurred, a Tukey multiple comparison test was applied (p < 0.05). All analyzes were performed with XLSTAT software (Addinsoft Inc., Paris, France).

#### **2.3 Genetic diversity**

The genetic diversity was studied in five populations (**Figure 1**), covering an altitudinal gradient from 388 to 1050 m.a.s.l. In each population, leaf tissue was collected from 21 individuals (seven from each age category). The DNA extraction was done with the DNeasy Plant minikit® Kit (Quiagen, Valencia, California, USA), following the kit's protocol and using approximately 100 mg of leaf tissue from which the cuticle was previously detached. A total of seven microsatellite markers designed by [22] (**Table 1**) labeled M-13 (−21pb) to obtain fluorescent products [23, 24], and PCR products were separated and genotyped with the LI-COR 4300 DNA analyzer

**99**

**3. Results**

**Table 1.**

P > 0.05).

almost half of the population.

**3.1 Demography**

*The Endangered Species* Dioon edule *in the Sierra Madre Oriental in San Luis Potosí…*

**Locus Primer sequences (5**′**–3**′**) Repeat N Size** ED3 F: GCATGAGGAGCTTGTTCCGT (CT)19 2 123–127

ED5 F: AGGCATAAATGGCTAAGCATAC (AG)16 5 136–148

ED6 F: ATGCAGATGAAACACACCC (TGG)8 2 239–242

ED9 F: CCTTGTGTTACTTTGAGCACC (CAT)9int 5 244–268

CAP5 F: CACTACCACCCCTATACCAC (CT)23 3 225–241

TOM5 F: CGTTTCCATTGGAGAGACAAG (TC)10 2 224–226

1660 F: GGTGCTGAAGAGGAAGAAGAA (GAA)16 4 194–230

(LI-COR Biosciences, Lincoln, Nebraska, USA) in a 6.5% polyacrylamide gel (LI-COR Biosciences, Lincoln, Nebraska, USA), at a wavelength of 700 nm.

It was calculated the average number of alleles per locus, percentage of polymorphic locus, the expected and observed heterozygosity, the fixation index and it was estimated the deviation of the Hardy–Weinberg Equilibrium using the GenAlex software [17], for all the samples and grouping the individuals according to their life stage. An Analysis of Molecular Variance (AMOVA) was performed on genetic distances. Wright's F statistics (Fis, Fst, Fit) was calculated for the whole set of populations and each age category with the GenAlex software [25], and also the degree of genetic differentiation between pairs of populations (Fst) was estimated

The density of the nine locations averaged 2050 individuals ha−1 ± 293.36. Density ranges from 3775 individuals ha−1 in SA to 775 individuals ha−1 in MO. The populations with the highest density of individuals are the localities of SA and GA, and the lowest density is MO, although there are no differences between localities in the number of individuals ha−1 of the populations (ANOVA, df = 8; F = 2.287;

The stages of the life cycle (**Table 2**) showed that seedlings were the most abundant, with an average of 49.27% ± 5.00, varying from the lowest in RN to the highest in SA. The proportion of young plants averaged 23.05% ± 2.62, with CH standing out with the lowest proportion and RN with the highest. The proportion of non-reproductive adults was 11.39% ± 3.12, being absent in SA and RN localities, unlike CH, where they represent a third of the population. Reproductive adults represented 16.29% ± 4.48, being scarce in SA and RN, but in the last, they are

*DOI: http://dx.doi.org/10.5772/intechopen.96372*

R: CTGTGAACTCCTGAAAGCATC

R: GCATTTCTAGTGGACAAACCAG

R: TCCTAACCATCCATCACTACC

R: CAACAATGTAAGTGATGATGCC

R: GACTTGAGCTTGTCTTTGTTG

R: CCATCCAAGTGAGTGATACAAG

*SSR primers used. N, number of alleles; size, allele size range (bp).*

for all the samples and grouped by life stage.


*The Endangered Species* Dioon edule *in the Sierra Madre Oriental in San Luis Potosí… DOI: http://dx.doi.org/10.5772/intechopen.96372*

#### **Table 1.**

*Natural History and Ecology of Mexico and Central America*

few reach the intermediate and late age categories [20].

measurements.

reproductive event [21].

each (n = 18).

Paris, France).

**2.3 Genetic diversity**

sideways, starting at one end of the line, and considering only those plants within the plot [19]. Due to the harsh characteristics of the area with rocky slopes of up to 70°, we traced two linear transects 100 m long by 2 m wide, parallel to the slope, locating them where the most significant number of individuals were concentrated, considering that *D. edule* populations present an aggregate distribution [18]. Each transect was divided into four 25 m long subunits to carry out the plants' counts and

The different stages of the cycads' life cycle were defined according to the number of leaves, the number of leaflets and stem height [7] because it has not yet been possible to define the age of the cycads due to their growth characteristics [18]. Therefore, individuals were classified as follows: seedlings, individuals that present one or more leaves without these forming a crown; juveniles, individuals that present one or more crowns, but with a non-visible stem; adults, individuals that present one or more crowns and have a visible stem. Adults were classified as male, female, or non-reproductive according to the presence of reproductive structures. Once the cycads' life cycle stages were defined, each stage's survival probabilities calculation as the proportion of individuals that survived to enter the next category, relative to the initial number of seeds (lx = nx/n0) [20]. A survival curve describes the survival pattern of individuals in a population over time, plotting the lx on the y-axis, in logarithmic scale, with life cycle stages on the x-axis There are three basic survival curves, the survival curve type I represents a population in which most of the organisms die in the older age categories. The type II curve represents a population in which the mortality rate is almost constant, and type III represents a population in which most individuals die during the first stages of the life cycle, and very

The stem's diameter and the plant's total height were measured, the total number

Considering that the species *D. edule* is dioecious and produce only one cone per reproductive event, we evaluated the number of plants with male and female cones present as a measure of the potential reproductive capacity of the population per

The data on population density and potential reproductive capacity was analyzed using a one-way Analysis of Variance (ANOVA) to determine the statistical difference among the nine populations studied (localities) with two transects in

Data on plant size and number of leaves of individuals in reproductive and nonreproductive states were analyzed through a nested ANOVA (random-effects model II) to determine the statistical difference among localities and categories of plants' reproductive states in all localities and each location. When statistically significant differences between means occurred, a Tukey multiple comparison test was applied (p < 0.05). All analyzes were performed with XLSTAT software (Addinsoft Inc.,

The genetic diversity was studied in five populations (**Figure 1**), covering an altitudinal gradient from 388 to 1050 m.a.s.l. In each population, leaf tissue was collected from 21 individuals (seven from each age category). The DNA extraction was done with the DNeasy Plant minikit® Kit (Quiagen, Valencia, California, USA), following the kit's protocol and using approximately 100 mg of leaf tissue from which the cuticle was previously detached. A total of seven microsatellite markers designed by [22] (**Table 1**) labeled M-13 (−21pb) to obtain fluorescent products [23, 24], and PCR products were separated and genotyped with the LI-COR 4300 DNA analyzer

of leaves was counted, and the length of those on the last crown was measured.

**98**

*SSR primers used. N, number of alleles; size, allele size range (bp).*

(LI-COR Biosciences, Lincoln, Nebraska, USA) in a 6.5% polyacrylamide gel (LI-COR Biosciences, Lincoln, Nebraska, USA), at a wavelength of 700 nm.

It was calculated the average number of alleles per locus, percentage of polymorphic locus, the expected and observed heterozygosity, the fixation index and it was estimated the deviation of the Hardy–Weinberg Equilibrium using the GenAlex software [17], for all the samples and grouping the individuals according to their life stage. An Analysis of Molecular Variance (AMOVA) was performed on genetic distances. Wright's F statistics (Fis, Fst, Fit) was calculated for the whole set of populations and each age category with the GenAlex software [25], and also the degree of genetic differentiation between pairs of populations (Fst) was estimated for all the samples and grouped by life stage.

#### **3. Results**

#### **3.1 Demography**

The density of the nine locations averaged 2050 individuals ha−1 ± 293.36. Density ranges from 3775 individuals ha−1 in SA to 775 individuals ha−1 in MO. The populations with the highest density of individuals are the localities of SA and GA, and the lowest density is MO, although there are no differences between localities in the number of individuals ha−1 of the populations (ANOVA, df = 8; F = 2.287; P > 0.05).

The stages of the life cycle (**Table 2**) showed that seedlings were the most abundant, with an average of 49.27% ± 5.00, varying from the lowest in RN to the highest in SA. The proportion of young plants averaged 23.05% ± 2.62, with CH standing out with the lowest proportion and RN with the highest. The proportion of non-reproductive adults was 11.39% ± 3.12, being absent in SA and RN localities, unlike CH, where they represent a third of the population. Reproductive adults represented 16.29% ± 4.48, being scarce in SA and RN, but in the last, they are almost half of the population.

#### *Natural History and Ecology of Mexico and Central America*


**Table 2.**

*Frequency of plants per stage of their life cycle in the locations.*

**Figure 2.**

*Survival curves according to the life cycle stages of the nine populations of* Dioon edule*. (A) SA, (B) GA, (C) AN, (D) CH, (E) PO, (F) AB, (G) EJ, (H) RN, (I) MO.*

**101**

**Figure 3.**

*The Endangered Species* Dioon edule *in the Sierra Madre Oriental in San Luis Potosí…*

structure were GA and RN, and with the lowest number was SA (**Figure 3A**).

The survival curve based on the states of the life cycle of the populations is an inverted "J" (type III), well defined in most locations (**Figure 2F, G, H, I**), and scarcely defined in other localities (**Figure 2D, E**). The localities of SA (**Figure 2A**), GA (**Figure 2B**) and AN (**Figure 2C**) showed a curve like type II in the populations. The population's potential reproductive capacity was 250 ha−1 ± 45.26 individuals in the localities with reproductive structures, of which 158 ha−1 ± 35.36 were male and 92 ha−1 ± 17.18 female. The highest number of male individuals with the reproductive

Likewise, the localities with the highest number of female individuals were RN and CH, and those with the lowest number were MO and AN (**Figure 3A**). The average sex ratio for the locations was 2: 1 (male: female), with the highest ratio of 4: 1 in GA and the lowest of 0.5: 1 in CH (**Figure 3B**). The ANOVA showed that there are no differences between mean localities in the number of female individuals ha−1 (n = 18; df = 8; F = 1.234; P > 0.05) and male individuals ha-1 (n = 18; df = 8;

An average of 35.70% ±2.79 of individuals was found in the transect up to 25 m, mainly seedlings and juveniles in the localities. From 25 to 50 m was found on average 34.39% ± 5.60, in the 50 to 75 m 19.89% ± 3.41 and in the 75 to 100 m, 10.02% ± 2.44. The 70% of the individuals were concentrated in the first 50 m from the transect's starting point and particularly in RN 100%. At sites with a steeper slope, there were plants widely dispersed, while at sites with flatter slope (less than 20%, e.g. SA), there were large groups of individuals aggregated around adult plants

Considering the plants' size and the number of leaves as parameters associated with the cycads' age, the longest and largest plants are in the communities of PO,

*Ratio of (A) the density of male (solid) and female (hollow)* Dioon edule *plants (± SE) and (B) the sex ratio* 

*in each location. Different letters mean significant differences (Tukey <0.05).*

or in the shade of oaks (*Quercus laeta*) and palms (*Brahea dulcis*).

*DOI: http://dx.doi.org/10.5772/intechopen.96372*

F = 1.006; P > 0.05) of the populations.

*The Endangered Species* Dioon edule *in the Sierra Madre Oriental in San Luis Potosí… DOI: http://dx.doi.org/10.5772/intechopen.96372*

The survival curve based on the states of the life cycle of the populations is an inverted "J" (type III), well defined in most locations (**Figure 2F, G, H, I**), and scarcely defined in other localities (**Figure 2D, E**). The localities of SA (**Figure 2A**), GA (**Figure 2B**) and AN (**Figure 2C**) showed a curve like type II in the populations.

The population's potential reproductive capacity was 250 ha−1 ± 45.26 individuals in the localities with reproductive structures, of which 158 ha−1 ± 35.36 were male and 92 ha−1 ± 17.18 female. The highest number of male individuals with the reproductive structure were GA and RN, and with the lowest number was SA (**Figure 3A**).

Likewise, the localities with the highest number of female individuals were RN and CH, and those with the lowest number were MO and AN (**Figure 3A**). The average sex ratio for the locations was 2: 1 (male: female), with the highest ratio of 4: 1 in GA and the lowest of 0.5: 1 in CH (**Figure 3B**). The ANOVA showed that there are no differences between mean localities in the number of female individuals ha−1 (n = 18; df = 8; F = 1.234; P > 0.05) and male individuals ha-1 (n = 18; df = 8; F = 1.006; P > 0.05) of the populations.

An average of 35.70% ±2.79 of individuals was found in the transect up to 25 m, mainly seedlings and juveniles in the localities. From 25 to 50 m was found on average 34.39% ± 5.60, in the 50 to 75 m 19.89% ± 3.41 and in the 75 to 100 m, 10.02% ± 2.44. The 70% of the individuals were concentrated in the first 50 m from the transect's starting point and particularly in RN 100%. At sites with a steeper slope, there were plants widely dispersed, while at sites with flatter slope (less than 20%, e.g. SA), there were large groups of individuals aggregated around adult plants or in the shade of oaks (*Quercus laeta*) and palms (*Brahea dulcis*).

Considering the plants' size and the number of leaves as parameters associated with the cycads' age, the longest and largest plants are in the communities of PO,

*Natural History and Ecology of Mexico and Central America*

**Juvenile (%)**

SA 70.20 26.49 0.00 3.31 GA 57.89 19.55 10.53 12.03 AN 50.93 28.70 16.67 3.70 CH 53.49 6.98 30.23 .30 PO 43.37 28.92 14.46 13.25 AB 46.55 25.86 8.62 18.97 EJ 35.56 22.22 15.56 26.67 RN 20.93 32.56 0.00 46.51 MO 64.52 16.13 6.45 12.90 Average 49.27 23.05 11.39 16.29

*Survival curves according to the life cycle stages of the nine populations of* Dioon edule*. (A) SA, (B) GA, (C)* 

**Adult**

**Reproductive (%)**

**Non- reproductive (%)**

**(%)**

*Frequency of plants per stage of their life cycle in the locations.*

**Location Seedling**

**Table 2.**

**100**

**Figure 2.**

*AN, (D) CH, (E) PO, (F) AB, (G) EJ, (H) RN, (I) MO.*

*Ratio of (A) the density of male (solid) and female (hollow)* Dioon edule *plants (± SE) and (B) the sex ratio in each location. Different letters mean significant differences (Tukey <0.05).*

CH, GA, AN, and SA. If it was impossible to measure the adult plants' height and diameter because they had a subterranean stem, only the number of leaves was considered, obtaining similar results.

The average height for non-reproductive individuals was 23.4 cm ± 3.4, with a maximum average height of 52.2 cm and the lowest of 14.5 cm. For reproductive plants, the maximum recorded height was 56.3 cm, and the lowest was 9.5 cm, with an average of 28.8 cm ± 8.3. However, the ANOVA showed that there are differences among means in plant height between localities (df = 8; F = 5.428; P < 0.001) and between categories of reproductive status in localities (df = 8; F = 4.992; P < 0.05), but not between categories of reproductive status in each locality (df = 1; F = 2.633; P > 0.05) (**Figure 4**).

The average stem diameter was 12.2 cm ± 2.5 in non-breeding individuals, with a width of 23.6 cm to 15.0 cm (**Figure 4A**), and in reproductive individuals, the average was 16.5 cm ± 4.4 with a maximum of 31.2 cm and a minimum of 5.5 cm. The ANOVA showed that there are no differences in the mean diameter between localities (df = 8; F = 1627; P > 0.05) or between categories of reproductive status in each locality (df = 1; F = 2848; P > 0.05), but there are differences between the categories of reproductive status of individuals in the localities (df = 8; F = 4034; P < 0.05) (**Figure 4**).

**Figure 4.**

*Size of* Dioon edule *plants (± SE) in each location. (A) Non reproductive and, (B) reproductive. Different letters mean significant differences (Tukey <0.05).*

**103**

**Table 3.**

*The Endangered Species* Dioon edule *in the Sierra Madre Oriental in San Luis Potosí…*

viduals in the localities (df = 8; F = 1.381; P > 0.05) (**Figure 4**).

The average number of leaves was 17.69 ± 2.18 in all individuals. The average number of leaves was 17.69 ± 2.18 in all individuals. In nonreproductive adults it was 14.3 with a maximum of 21 and a minimum of 3.5 (**Figure 4A**), for reproductive adults it was 15 with a maximum of 22.5 leaves. The ANOVA showed that there are differences in the mean number of leaves between localities (df = 8; F = 3.166; P < 0.05) and between categories of reproductive status in each locality (df = 1; F = 7.312; P < 0.05) but not between the categories of reproductive status of indi-

Only three of the first seven proposed were amplified, ED9, TOM5, and CAP5. All the loci were polymorphic, but the population AN have the lowest proportion of polymorphic loci (33.33%) in the seedlings (**Table 3**). The average number of alleles per locus was 3.66; in the seedling stage, the lowest value corresponds to Los AN (1.33) (**Table 3**). There were no unique alleles within the adult stage. However, in the juvenile and seedling, four and three unique alleles were found, respectively, and ED9 was the locus that presented the highest number of unique

**N Na Polymorphic** 

SA Seedling 6.33 2.67 100 0.111 0.464 0.795

AN Seedling 3 1.33 33.33 0.000 0.163 1.000

CH Seedling 6.67 3.33 100 0.167 0.613 0.786

PO Seedling 7 3 66.67 0.333 0.429 0.239

RN Seedling 6.67 2.67 100 0.325 0.334 0.197

*Genetic diversity index for five* Dioon edule *populations in San Luis Potosi, Mexico.*

**Loci (%)**

Juvenile 6.33 3 66.67 0.167 0.355 0.695 Adult 6 2.67 100 0.133 0.489 0.810 Total 18.67 3.67 100 0.137 0.496 0.817

Juvenile 5 3.33 100 0.333 0.634 0.556 Adult 6.67 3 100 0.143 0.511 0.791 Total 14.67 4 100 0.194 0.583 0.741

Juvenile 6.33 3.33 100 0.222 0.543 0.636 Adult 7 2.67 100 0.048 0.541 0.934 Total 20 4 100 0.139 0.600 0.811

Juvenile 7 2.33 100 0.238 0.446 0.605 Adult 7 2.67 100 0.238 0.418 0.605 Total 21 3.33 100 0.270 0.446 0.572

Juvenile 6.67 2.67 66.67 0.278 0.445 0.423 Adult 7 2.33 66.67 0.286 0.303 0.354 Total 20.33 3.33 100 0.297 0.394 0.260

**Ho He F**

*DOI: http://dx.doi.org/10.5772/intechopen.96372*

**3.2 Genetic diversity**

**Location Life cycle** 

**stage**

alleles.

*The Endangered Species* Dioon edule *in the Sierra Madre Oriental in San Luis Potosí… DOI: http://dx.doi.org/10.5772/intechopen.96372*

The average number of leaves was 17.69 ± 2.18 in all individuals. The average number of leaves was 17.69 ± 2.18 in all individuals. In nonreproductive adults it was 14.3 with a maximum of 21 and a minimum of 3.5 (**Figure 4A**), for reproductive adults it was 15 with a maximum of 22.5 leaves. The ANOVA showed that there are differences in the mean number of leaves between localities (df = 8; F = 3.166; P < 0.05) and between categories of reproductive status in each locality (df = 1; F = 7.312; P < 0.05) but not between the categories of reproductive status of individuals in the localities (df = 8; F = 1.381; P > 0.05) (**Figure 4**).
