Availability of Wild Edible Fungi in La Malinche National Park, Mexico

2.1. Study Area

La Malinche National Park is located between northern latitudes 97° 55′ and 98° 08′ and between western longitudes 19° 20′ and 19° 08′. The local climate is temperate subhumid with a rainy season in the summer [C(w₂)(w)]; the pressure/temperature ratio is 41.9 and there is little annual variation in average monthly temperatures, with fluctuations between 5° and 7°. The annual mean temperature is 15.3°C. May is the hottest month (mean temperature = 17.7°C) and January is the coldest (mean temperature = 11°C). Over 4000 m, weather tends to be very cold, type E (T) H, with temperatures under 0°C in the coldest month [9].

There are three main vegetation kinds: a forest dominated by P. hartwegii in higher altitudes; a forest dominated by Pinus montezumae and P. teocote mixed with Alnus jorullensis, Quercus laurina, and Q. crassifolia in lower altitudes; and an Abies religiosa forest sometimes mixed with individuals of P. montezumae, P. hartwegii, Salix cana, S. paradoxa, and Juniperus monticola in some gullies.

2.2. Sampling

Eight sample units (SUs) were established for this study (Table 1). Four SUs (1–4) were placed in Southeast slope (4–7 km west of Francisco Javier Mina) and the other four (5–8) in the Southwest slope (6-7 km north of San Isidro Buensuceso) (Figure 1). SUs were placed in locations usually visited by mushroom collectors. This had the purpose to reproduce not the natural production of mushrooms but their real availability, since there is a strong competition among mushroom collectors. To reduce the impact of mushroom collection in our data, transects were always visited as early as possible.

The SUs were sampled at one week intervals during the rainy seasons (July to October). Both areas were visited during three years, from 1998 to 2000; SUs 1–4 (Southeast slope) were visited 40 times, and SUs 5–8 (Southwest slope) were visited 37 times. At each visit, all fruit bodies were counted, picked up, and weighed, to avoid double counting at the next visit. At least one sample of each species was taken to the laboratory, processed as a voucher specimen for identification, and deposited at TLXM herbarium.

Each SU was composed of two parallel transects of 250 m each. Both transects were separated by a 50 m distance. Transects were permanently marked every 5 m, using sticks surrounded by black pieces of plastic on one side. We had a total of 100 sampling plots on each SU. Each plot had a radio of 1.13 m and a total area of 4.011 m² [10]. The total area sampled each year was of 3,200 m².

Edibility of each species was determined through local information, literature from the area [3], literature from México [11], and literature from other parts of the world [12]. The complete list of the material reviewed was published previously by Montoya et al. [3].

2.3. Data Analysis

Species richness was determined by the number of species registered in each SU. Abundance of fruit bodies was defined as the number of fruit bodies of each species in each SU during the three-year period. Production was calculated as the total fresh weight of each species. Biomass was calculated by measuring the dry weight of each species (fruit bodies were dehydrated at least 24 h at 105°C). Spatiotemporal frequency was calculated as the sum of the number of sampling plots where a species was found in each sampling date. Spatial frequency is the number of different plots in which a species was found during the three-year period in each SU. Spatial frequency was categorized in exponential classes: very infrequent (1–3), infrequent (4–9), frequent (10–21), very frequent (22–45), and extremely frequent (46–100). We looked for statistical differences in fruit body abundance and fruit body production between the two slopes. For this purpose, either the total number of fruit bodies or the total fresh weight in each SU (8) was considered as independent observations, while the data in each SU along the years (3) were considered as repeated measures, having twelve observations per slope. Means were compared by a bifactorial ANOVA for mixed designs in STATISTICA10 [13]. Availability of each species was determined by means of its ecological importance value, which equals the sum of its relative abundance, relative spatiotemporal frequency, and relative production [14].

Similarity between the SUs, according to their species composition, was computed using the species spatiotemporal frequency. A distance matrix was built, where rows corresponded to the species and columns to the eight SUs. The correlation index (Pearson product moment) was computed and SUs were clustered with the UPGMA method; then, the cophenetic value was computed. An ordination of the eight OTUs (=SUs) in a multidimensional space of characters was made by means of a Principal Component Analysis (PCA). Analyses were done in NTSYS-pc [15]. The diversity was calculated by using the Shannon-Wiener index. Since it is not possible to know the number of individuals, fruit bodies were counted and, instead of using abundance rates, spatiotemporal frequency was used. These analyses were done in the past software, version 2.16 [16].

3.1. Species Richness

During the three sampling years, 61 edible mushroom species were found (Table 2): 48 species in the Southeast slope and 49 in Southwest slope. The species belonged to 37 genera. Fifty-one species were Basidiomycetes and the best represented families were Russulaceae with 9 species and Amanitaceae with 5 species. We identified 9 Ascomycetes, the family Helvellaceae being the best represented, with 4 species. 44 species were mycorrhizal, 15 were saprotrophs, and 2 were parasitic.

During the three years of sampling, the highest species richness was found in the Pinus-Abies forest (SU2 and SU6) and the lowest value was observed in the Pinus forest (SU7) of the Southwest slope. Despite the sampling year, the highest species richness was always observed in the Pinus-Abies forests (in 1998 at SU6; in 1999 at SU1 and SU5; in 2000 at SU5, SU6, and SU8). In 1999, a Pinus forest (SU3) located in the Southeast slope also showed a high species richness. The presence of different tree host species offers more possibilities to find a higher diversity of ectomycorrhizal mushrooms and more substrates for saprotrophic mushrooms. Likewise, microhabitats, produced by the soil humidity and mosses associated to Abies, produce several differences for the mushroom community.

Species exclusive to the Southeast slope were Amanita basii, Amanita vaginata, Armillaria aff. mellea, Cantharellus cibarius, Laccaria amethystina, Lyophyllum sp. 1, Ramaria sp. 1, Ramaria sp. 2, Ramaria sp. 3, Russula integra, and Russula olivacea. Species exclusive to the Southwest slope were Agaricus augustus, Amanita fulva, Boletus luridus, Clavulina cinerea, Clavulina coralloides, Geopora sp., Turbinellus floccosus, Helvella acetabula, Russula albonigra, Hygrophoropsis aurantiaca, Hygrophorus hypothejus, and Sarcosphaera coronaria.

3.2. Abundance of Fruit Bodies

During the three sampling years, the highest number of fruit bodies (1,319) was found in the SU4, in a Pinus forest on Southeast slope. This means that they were 5.6 times more than those recorded at SU1, where the less number of fruit bodies was found (230). The lowest abundance was observed in the Pinus-Abies forest (SU1) of the same area. More fruit bodies were found in the year 2000 than in the two previous years. Southeast slope produced almost twice as many fruit bodies as the Southwest slope (Table 2). The most abundant species in the three years were L. trichodermophora, Hebeloma mesophaeum, Clitocybe gibba, Helvella lacunosa, Morchella elata, Suillus pseudobrevipes, Helvella crispa, and S. coronaria.

Although the mean of fruit bodies produced in the Southeast slope (256.83 fruit bodies/SU year) doubled those produced in the Southwest slope (114.42 fruit bodies/SU year), no statistical differences were found between slopes (F_(1,18) = 3.77, P = 0.06), nor between years (F_(2,18) = 0.291, P = 0.750), because of the high standard deviation in the data of Southeast slope (233.882). The interaction between slopes and years also showed any difference (F_(2,18) = 1.034, P = 0.375).

3.3. Production

Comparing the values obtained for the two areas, higher values (16.10 Kg/3200 m²) were found on the Southeast slope, L. trichodermophora being the most productive species, whereas, on the Southwest slope (13.44 Kg/3200 m²), S. coronaria showed the highest values. The total fresh weight recorded at the SUs during the three-year period was 29.54 Kg/3200 m² (Table 2). This amount means 92.10 Kg/ha/3 years of edible wild mushrooms. SU3, located in a Pinus forest, had the highest values of fresh weight. Year 2000 had the greatest production of edible mushroom fresh weight.

The species with the highest values of fresh weight were in 1998 L. ovispora, R. acrifolia, R. brevipes, H. mesophaeum, and L. trichodermophora; in 1999 L. trichodermophora, R. brevipes, R. acrifolia, and A. rubescens; and in year 2000 S. coronaria, L. trichodermophora, S. pseudobrevipes, R. acrifolia, C. glaucopus, and B. pinophilus. No statistical differences were found between the means of fresh weight of edible mushrooms produced in each slope (F_(1,18) = 0.417, P = 0.526) nor between the years (F_(2,18) = 2.24, P = 0.135). The interaction between mushrooms abundance by slopes and years did not show any difference (F_(2,18) = 1.19, P = 0.325).

3.4. Biomass

The highest biomass production (1.59 Kg/3200 m²/3 years) was recorded in the SUs located in Southeast slope, while 1.25 Kg/3200 m²/3 years was produced in the Southwest slope. L. trichodermophora and L. ovispora were the species with the highest biomass production values in the Southeast slope and S. coronaria and R. brevipes in the Southwest slope. The total biomass was 2.84 Kg/3200 m²/3 years, which would mean 8.87 kg/ha. SU3 had the highest values. The highest values were recorded in year 2000 (Table 2).

3.5. Spatiotemporal Frequency

Southeast slope had a higher spatiotemporal frequency (STF), presenting 905 plots with mushrooms, while Southwest slope had 590 plots with mushrooms. SU4, located in a Pinus forest, had the highest overall STF with 371, while SU7, also in a Pinus forest, had the lowest with 96. Year 2000 had the highest overall STF with 642 plots. The species observed in the biggest number of sampling plots were L. trichodermophora, H. mesophaeum, H. lacunosa, H. crispa, S. pseudobrevipes, and C. gibba; then, they were the species most widely distributed in the study area (Table 3).

3.6. Spatial Frequency

Southeast slope had the highest spatial frequency (SF) (471 plots) and Southwest slope showed a relative SF of 389 plots. The SUs with the highest values of frequency were SU4, SU3, SU6, and SU5. SU7 presented the lowest SF. Species with the highest percentage of SF throughout all the sampled area were L. trichodermophora (17.75%), H. mesophaeum (9.00%), H. lacunosa (8.00%), H. crispa (6.38%), M. melaleuca (4.38%), S. pseudobrevipes (4.25%), and C. gibba (4.13%) (Table 3).

The SF values for A. basii, A. rubescens, B. pinophilus, H. mesophaeum, L. trichodermophora, and L. decastes were higher in the Southeast slope, while, for T. floccosus, H. crispa, H. lacunosa, M. elata, and M. esculenta, higher SFs were registered in the Southwest slope. In both cases, those species have been determined to be the most important from a cultural perspective [5].

3.7. Availability

Values obtained as the availability index for each species are showed in Table 3. Species with the highest values in this study were L. trichodermophora, S. coronaria, H. lacunosa, H. crispa, M. elata, C. gibba, M. melaleuca, R. acrifolia, R. brevipes, and S. pseudobrevipes. The information obtained from the availability index shows the presence of several different environments adequate for the fruiting of mushrooms. In the Southwest slope, Abies forests are located in a lower altitude than those in the Southeast slope, where Pinus forests are predominant, so there are differences in species between the two sites.

L. trichodermophora, H. mesophaeum, E. clypeatum, and S. pseudobrevipes had the highest values in the Southeast slope, while L. trichodermophora, S. coronaria, H. lacunosa, C. gibba, and H. crispa had the highest values on the Southwest slope. As for the Southwest slope, Figure 2 shows a greater diversity of species with considerable availability. These were present in space and time in a differential way. As well as in the Southeast slope (Figure 3), the significance of L. trichodermophora stands out. In this case, S. coronaria, because of its consistency, showed high production values considering its low abundance.

The availability of species measured by the ecological importance value did show remarkable differences between the two slopes. The Southeast slope has two dominant species: L. trichodermophora and H. mesophaeum. The other species registered on this area showed low values, suggesting their scarce availability in the three sampling years. L. trichodermophora was very abundant; it was widely distributed in the said space and time. In contrast, its production was not very high because of the size of its fruit bodies. It is interesting to notice that mushrooms as B. pinophilus have relatively high values of production due to the consistence and size of their fruit bodies, despite their low abundance and distribution in time and space. These characteristics contribute to the increase of the high production values in the Southeast slope.

3.8. Similarity

The cluster analysis (Figure 4) shows the similarity between SUs based on the values of the spatiotemporal frequency of species. Two main clusters can be observed. The first is composed of three SUs, two from the Southwest slope (SU6, SU8) and one from the Southeast slope (SU1). The two most similar SUs of this group are SU1 and SU6 and are related to SU8; half of SU1 and all SU6 are located in an Abies forest and SU8 which is the most different SU is in a mixed forest. The second cluster includes SU2, SU4, SU7, and SU3, three of them from the Southeast slope, and SU7 is from the Southwest slope, all of which are set up on Pinus forests. SU2 and SU4 are the two most similar. SU3 is the most different within this group. SU5 is the most different of all SUs.

As shown in Figure 5, the results of PCA provide a sharper definition of the different clusters described above. The results of PCA indicate that the species that contributed to cluster formation (which have a loading >0.7 on the first two PCs) were M. aff. melaleuca, L. trichodermophora, A. basii, H. mesophaeum, C. cibarius, and C. amianthinum in PC1. A. vaginata, Geopora sp., G. dryophilus, G. infula, M. elata, and S. coronaria in PC2 are all absent from SU3. The first two Principal Components explain cumulatively 44.9% of data variation.

The representation of the OTUs in a three-dimensional space of characters (Figure 5) shows that SUs studied are closer to one another by vegetation type. In the clusters formed by these SUs, it is possible to identify subgroups, according to the species of edible mushrooms present or absent. Sampling units 1 and 6 showed 17 species in common, some are characteristic of Abies forests, for example, C. gibba, C. odora, H. crispa, H. elastica, H. lacunosa, L. salmonicolor, and M. esculenta. And some others also grow in Pinus forests, for example, A. rubescens and E. clypeatum. SU8 presented six exclusive species, which had the highest values in the analysis of PCA. Conforming a subgroup distinct from the previous, SUs 2 and 4 presented 19 species in common, most of them are mushrooms associated with Pinus forests (e.g., A. basii, A. franchetii, H. mesophaeum, L. trichodermophora, and S. pseudobrevipes, among others), and SUs 3 and 7 share 16 species which are mushrooms associated with Pinus forests (e.g., A. franchetii and B. pinophilus). SU 5 was the most different; it had two exclusive species (Geopora sp. and S. coronaria) and is located higher in altitude than other SUs.

Comparing information obtained for both slopes of La Malinche National Park, the highest values, in all parameters considered, were observed in the Southeast slope. However, we did not find statistical differences.

3.9. Diversity

Based on the abundance of fruit bodies, the Shannon-Wiener diversity index (H^′) in the Southeast slope was 1.78, with a max H^′ of 3.87. H^′ in Southwest slope was 3.00, with a max 3.89 H^′. Based on the abundance of plots, H^′ was 2.53 for Southeast slope and 3.26 for Southwest slope. In summary, considering the abundance of fruit bodies or plots, the greatest diversity values were found in the Southwest. The calculation of the weighted diversity index (H_p) showed that both slopes are statistically different with respect to one another (Table 4).

The highest value for the Shannon-Wiener diversity index was obtained in SU7 (H^′ = 3.43) located in the Southwest slope, with 21 species. The lowest value of diversity was obtained in SU4 (H^′ = 1.81) located in the Southeast slope, with 25 species. The evenness ranged from 0.88 in SU1 (Pinus-Abies forest) to 0.78 in SU8 (mixed forest dominated by Pinus) (Table 4).