Twenty-one traditional taxa were mentioned in all free lists, which correspond to 37 scientific taxa (Table 3) [24]. Amanita caesarea complex, Ramaria spp., Neolentinus lepideus and Agaricus pampeanus were recognized by more than 50% of informants (Figure 6). If we group the two Cantharellus cibarius taxa, commonly considered as the single folk species "Beshia de", they had 89 mentions. Tricholoma magnivelare,Hypomyces lactifluorum,Hydnum repandum s.l. and Lactarius volemus s.l. were recognized between 50% and 20% of informants. Species known by less than five informants were Austroboletus betula, Lactarius deliciosus s.l., Laccaria vinaceobrunnea s.l., Hygrophoropsis aurantiaca, Pleurotus sp. and Gomphus clavatus. In Table 4 we show the values of every CS sub index for each taxa.
Cultural variables (sub indexes)
Perceived abundance index
Species with perceived abundance values of 7.5 or more were Cantharellus cibarius sp.1, C. cibarius sp.2, Pleurotus sp. and Laccaria laccata var. pallidifolia; and those perceived as rare (PAI ≤ 2.5) were Gomphus clavatus and Sparassis crispa. Certainly L. laccata var. pallidifolia is the most abundant mushroom in Ixtlan woods [23]. Previous research [38] has shown that C. cibarius sp.2 scores as common, but not abundant. Perhaps this can be explained by the fact that people think it is abundant by association with C. cibarius sp.1 that is sold copiously in the village market. We do not have data about Pleurotus sp. abundance, however forest employees reported that it is scarce near town, and abundant in wet faraway forests. Our data shows that G. clavatus and S. crispa are very uncommon and restricted to particular habitats. Perceived abundance index is the only EMCSI sub index that is not eminently cultural, because it is derived from the perception of an ecological aspect. The relation between real abundance and perceived abundance is not clear and needs further research. A clear understanding of this is fundamental to know how people appreciate and use their natural resources.
Frequency of use index
Only Cantharellus cibarius sp.1, C. cibarius sp.2 and the Amanita caesarea complex were used more than one time a year (FUI > 5). Those used in occasional years (FUI ≤ 2.5) were Pleurotus sp., Tricholoma magnivelare and Lactarius deliciosus s.l. The formers are species much appreciated and easy to obtain (by collect or commerce). The latter are mushrooms with regular abundances known only by restricted social groups.
Taste score appreciation index
According to informants, fifteen species can be cataloged as good tasting (TSAI ≥ 6.67). The most palatable were Gomphus clavatus, Sparassis crispa, Neolentinus lepideus, Cantharellus cibarius sp.2, the Amanita caesarea complex and C. cibarius sp.1. Those with simple taste (3.33 6.67) were Austroboletus betula, Laccaria laccata var. pallidifolia, Hygrophorus russula s.l., Agaricus pampeanus, Cortinarius secc. Malacii sp. and Lactarius volemus s.l. No mushroom scored as bad tasting. Because personal evaluations of taste are strongly influenced by the idiosyncrasy [39], cultural domains as "good taste" are only explicable by intracultural perspectives. As an example, Ruán et al. [40,41] discuss that the high CS of Schizophyllum commune as food in the tropics, particularly in Southwest Mexico, is not affected by its corky or rubbery consistence. In Ixtlan, between those species highly valued by their taste, we found: worldwide fungal delicatessen's as C. cibarius s.l. and the A. caesarea complex; species valued by local people because its similar to meat consistency (S. crispa, N. lepideus), a very common phenomenon in Mexico; and G. clavatus, a mushroom without previous reports of edibility in Mexico. The taste of some species was defined as simple (L. laccata var. pallidifolia), not consistent (A. betula) or bitter H. russula s.l. The last example is interesting because this taxon in fact are two species H. russula and H. purpurascens that people recognize as one "Beshia biarida". People commonly reported on the bitterness of this mushroom, relating it to either age of mushroom, or to its cuticle. Both species are edible, although locally one of them has a bitter taste. The lack of deep local folk taxonomic detail affects the use of these resources by not being able to tell them apart.
Multifunctional food index
Six species were consumed as principal stew elements (MFFI ≥ 7.5) and those occasionally consumed on their own (MFFI ≥ 8.25) were Gomphus clavatus, the Amanita caesarea complex and Lactarius deliciosus s.l. Mushrooms which are always consumed mixed with other mushrooms and meat (2.5 5) were Hygrophoropsis aurantiaca, Hygrophorus russula s.l. and Laccaria spp. A series of practical factors take place in the decision of how to cook fungi: how many mushrooms of each species are available; the economic status, since poorer people substitute meat with fungi; how much time they have to prepare mushrooms; and how hungry they are. Other factors are cultural and idiosyncratic: the culinary background of the culture, family traditions and recipes, and the individual tastes. Gomphus clavatus and L. deliciosus s.l. are consumed on their own in Ixtlan by the few people that know them and appreciate their flavor. The Amanita caesarea complex species are an interesting case, they are eaten alone by almost all the interviewees, because of flavor, size and easiness to be cooked. The extreme of this culinary value takes place inside the woods with forest employees. When they camp for several days, they complement their diet by eating wild fungi, and these mushrooms go from the ground to the campfire to the mouth quickly and pleasantly. On the other hand, species that are always mixed with other mushrooms and meat have several characteristics. They are very abundant, small and simple in flavor (Laccaria laccata var. pallidifolia); abundant and big but not very tasty (Hygrophorus russula s.l.); and common, small and simple tasting (Hygrophoropsis aurantiaca). There is a group of species (Hydnum repandum s.l., Cantharellus spp. and Ramaria spp.) commonly cooked mixed or alone in "amarillito", a kind of yellow chili sauce "mole" with ritual and festive implications. Lactarius volemus s.l. was reported to be consumed raw by two informants. Cantharellus cibarius spp., L. volemus s.l. and Neolentinus lepideus were dried up. This practice is more important in N. lepideus because: it is a rare mushroom, found by few people; commonly sold, given as gifts or bought as something special; specimens can reach almost 30 cm; and due to its phenology (April and May) it can only be enjoyed during a short period.
Knowledge transmission index
According the KTI, eighteen folk species are part of the mycological traditional knowledge of the people of Ixtlan (KTI ≥ 5). The most deep-rooted were Cortinarius secc. Malacii sp., Hydnum repandum s.l., Laccaria vinaceobrunnea s.l., Cantharellus cibarius sp.2, Hypomyces lactifluorum, Agaricus pampeanus, C. cibarius sp.1 and the Amanita caesarea complex. One can usually trace the knowledge of these mushrooms in up to six generations in one family, although there is a tendency of not teaching children the traditional knowledge about mushrooms. This is evident in C. secc. Malacii sp. that nowadays is known just by 14 informants of which only two were young people. This can be illustrated also with the case of L. vinaceobrunnea s.l. since although previous generations knew it well (KTI = 8.750), today only 4.21% of informants are familiar with it. Those mushrooms with less traditional importance (KTI Sparassis crispa, Tricholoma magnivelare and Pleurotus sp. These data corroborate previous observations about the intense cultural exchange and incorporation of new species to the traditional mycological knowledge of the town [24]. In our observations, Ixtlan inhabitants apparently did not originally know S. crispa, but have learned to consume it from sellers from neighboring towns. In fact, T. magnivelare (American matsutake) is a recent (10–15 years ago) incorporation to Ixtlan' culture. Today Ixtlan' people use this mushroom with their own new ideas and myths in their cultural context. This evidence shows the relevance of this variable to understand the dynamic and adaptive nature of traditional knowledge.
Health index
Tricholoma magnivelare (HI > 8.336) was the only mushroom believed to have health enhancing properties, including "strength", "virility" and "intelligence". Other mushrooms were also believed to be health related by classifying them as "nutritious" or "good for the body", such as Neolentinus lepideus, Hydnum repandum s.l., Cantharellus cibarius spp., Ramaria spp. and Lactarius volemus s.l. (HI > 6.670). Species avoided because of their resemblance to toxic ones (HI Agaricus pampeanus, the Amanita caesarea complex and Cortinarius secc. Malacii sp. When people where questioned about the special health properties of T. magnivelare, in general they follow a similar logical path: "Japanese companies buy this mushroom at prices never seen for mushrooms"; so, "they have to extract something special from this mushroom"; "as Japanese are very smart and healthy"; "those extracts must be medicines or vitamins". In fact, some informants assured feeling healthier, or reported that their children get better grades in school since they eat them. Species considered as more than healthy, according informants, are "special", "very consistent" or have nutritional and metaphysical properties, such as "full with vitamins", "almost as medicine", "relaxing", "it fills the tummy", "is better than meat". Taxa avoided by certain people can be truly confused with toxic ones present in Ixtlan' woods. White Agaricus like A. pampeanus can be confused with Amanita virosa buttons [42]; in fact, one mortal intoxication in Ixtlan was due to this last species. Old or washed A. muscaria specimens could be mistaken for A. caesarea s.l. [43] and Cortinarius secc. Malacii sp. is inside a genus with very similar toxic species [44].
Economic index
Eleven folk taxa had zero EI values, these were species never sold in Ixtlan. Hypomyces lactifluorum, Ramaria spp., Cantharellus cibarius sp.2, Hydnum repandum s.l., the Amanita caesarea complex and Lactarius volemus s.l. had 0 1), Neolentinus lepideus and Sparassis crispa had values between, 1 and 3.33. The former, is found occasionally by forest employees and people buy it from them at any price. The latter is a mushroom not common in Ixtlan woods, so it only can be bough from other town sellers. Cantharellus cibarius sp.1 is the sole mushroom regularly sold in Ixtlan' market (IE = 3.641). Every Monday from July until October its possible to buy 1/2 kg of these mushrooms from $1.5 to $2 USD (11.5 pesos/dollar). Tricholoma magnivelare had the highest EI value (IE = 4.565), although people do not sell it anymore to Japanese companies. This is very significant because it means that the economic importance is not tied only to income or expenses, it is also related to its potential economic value.
Edible mushrooms cultural significance index
The EMCSI values varied from 399.430 for the A. caesarea complex to 4.018 for G. clavatus. Species with highest scores were the A. caesarea complex, Ramaria spp., N. lepideus, C. cibarius sp.1 and C. cibarius sp.2. The "Beshia de" folk taxa in conjunct reached 440.660 points, which is more than any other fungi. Species with less CS (EMCSI Laccaria vinaceobrunnea s.l., Pleurotus sp., A. betula, H. aurantiaca and G. clavatus. Because EMCSI is pondered by the mentions relative value, it must be considered a sample CS estimate. Thus, species with more mentions count higher than those with fewer mentions.
Interestingly, Montoya et al. [45], although using a free listing technique, found that Amanita caesarea s.l. and Cantharellus cibarius s.l. are among the three most cultural significant mushrooms to the nahua communities inhabiting the Malinche National Park in Tlaxcala, center of Mexico. These two taxa are indeed very appreciated thru the world; however, if they are the most cultural important species in Mexico is an answer waiting for cross-cultural studies achievable by techniques as the proposed in this paper. Other important question to deal in the future is if data from a free list and from a compound index could be comparable and which of these techniques is better to deal with the CS phenomenon.
For mushrooms, other cultural domains to include in a compound index could be the parts used, its medicinal role, its religious or ritual use and several economic related issues like volumes of sell or collect, average prices, commercialization process, etc. Because the ethnomycologic study in Ixtlan has been done for several years, it is very likely that any of these variables affect locally the CS of mushrooms. In order to choose the variables that will be included in a compound CS index, it is imperative to have a previous scheme of the local traditional knowledge. A very interesting approach to do this accurately and time saving is to perform a preliminary inquiry about the causes of CS by the informant point of view. This is done by the question: what (mushroom, plant, etc.) is most important to you? Followed by: which criteria do you used to define the importance? By these way the own people is going to show the cultural domains locally relevant, and then their responses can be summarized into concrete cultural domains to include in the compound index [46].
Multivariate analysis
The tree diagram of Euclidean distances (ED) (Figure 7) showed three mayor groups of species. From right to left, the first group (A) is separated from the other groups at a ED of 12.62. It is conformed by the ten most culturally significant species except Tricholoma magnivelare. The second (B) and the third (C) major groups are separated at an ED of 9.63. Nine species with little CS integrate "B" group. The "C" group has three very particular species with variable CS (Gomphus clavatus, Sparassis crispa and T. magnivelare). The closest species were Hypomyces lactifluorum and Hydnum repandum s.l (ED = 1.40); Lactarius volemus s.l. joins these two species at a ED of 1.67. Other pairs of close species were Laccaria laccata var. pallidifolia and Hygrophorus russula, Laccaria vinaceobrunnea s.l. and Cortinarius secc. Malacii sp., Lactarius deliciosus s.l. and Cantharellus cinnabarinus, C. cibarius sp.1 and sp.2, Ramaria spp. and the A. caesarea complex. There were also three minor groups of species, H. lactifluorum, H. repandum s.l., L. volemus s.l., Agaricus pampeanus and N. lepideus which were clustered as group "d" at a ED of 4.53. Lactarius deliciosus s.l., C. cinnabarinus and Austroboletus betula conformed group "e", which was joined at a ED of 5.78. Laccaria laccata var. pallidifolia, H. russula, Hygrophoropsis aurantiaca, L. vinaceobrunnea s.l. and Cortinarius secc. Malacii sp. integrated group "f", which couples at a ED of 6.21.
The MDS analysis two-dimensional solution (stress = .00048) is displayed in Figure 8. The species configuration was similar to the grouping in the cluster technique. Some species pairs disappeared like Ramaria spp.-A. caesarea complex and L. vinaceobrunnea s.l.-Cortinarius secc. Malacii sp. In minor group "d", N. lepideus was far away from the rest of the species and the two C. cibarius species were closely related to this group. Cortinarius secc. Malacii sp. was far away from the rest of "f" species and Pleurotus sp. joined them. The two first axes separated quite well between the major groups. Species in group "A" always had values over 0.2 in dimension 1, species in group "B" always had values under 0.2 in dimension 1 and lesser than 0.6 in dimension 2, while "C" group species were always over 0.6 in dimension 2 (Figure 8). These three major groups were also supported by the PCA (Figure 9). In it, the first three principal components (PC) explain cumulatively 71.67% of data variation. The most important variables in PC1 were the economic index, taste score appreciation index and health index (eigenvalues 0.52, 0.49, 0.46 respectively). In PC2, most important variables were the knowledge transmission index, frequency of use index and mention index (eigenvalues 0.50, 0.49, 0.44 respectively). Then, the species on group "A" (nine of the most culturally significant) in general are characterized by: have being used by more than three generations, are consumed frequently (except Neolentinus lepideus) and because they are the best known species; they also have some economic importance (particularly N. lepideus, the Amanita caesarea complex and Cantharellus cibarius sp.1), pleasant tastes, and are considered health enhancing (except the A. caesarea complex). The species on group "B" have zero economic importance, have mediocre to appreciable tastes, are not traditionally relevant (except Cortinarius secc. Malacii sp. and Laccaria vinaceobrunnea s.l.), are consumed infrequently and are known by less than 50% of informants. The three species in "C" in general are not consumed traditionally in Ixtlan, are used infrequently and are known by few informants (except Tricholoma magnivelare); on the other hand, they have a combination of high economic importance, pleasant tastes and health promoting properties.
In the PCA between sub indexes, the first three components explain 89.92% of data variation. There were not sub index groupings; just MFFI and TSAI were related. The HI was near these and the rest were isolated in the extremes (Figure 10).
The EI was the most correlated variable; it had positive correlations with the mention index, health index and taste score appreciation index (rs = 0.651, P = 001; rs = 0.638, P = 0.002; rs = 0.546, P = 0.011 respectively). People obtain edible mushrooms in Ixtlan easily; there are several acquisition mechanisms such as collect, reciprocal gifting and buying, thus almost every person have access to this resource [24]. Then, these correlations are logic because the prices of mushrooms are low with the exception of those having very good tastes or considered as "specials", "like meat" "very consistent" or with health enhancing properties. Sold species had high mentions because people knowing just few species always mentioned them [46]. There was also a correlation between the multifunctional food index and the taste score appreciation index (rs = 0.451, P = 0.040). Since mushrooms tasting better are coked in ways to conserve their flavor and thus they are not mixed with many other elements.
The rest of the possible correlations (24/28) were not significant, this and data from PCA between sub indexes, are relevant because they showed that different cultural domains evaluated behaved in different directions and, with some exceptions, were independent. Methodologically this must be expected because a cultural domain is defined as "... an organized set of words, concepts or sentences, all of the same level of contrast, that jointly refer to a single conceptual sphere" [47] thus our variables were defined accurately and did not represented unbound elements that could cause confusion between interviewees.
Implications for further ethnobiological studies
The model proposed here is based on the fact that CS of resources is determined by a wide number of variables or cultural domains. To propose an index that includes all possible cultural domains is not feasible since cultures around the world value different resources attributes; its better to develop indexes composed by cultural domains locally important and relevant to the studied organisms. If a core of main cultural domains is used, some of them can be added or removed and the opportunity of cross-cultural analysis remains. This is possible by contrasting the relative positions of species in several compound indexes (also possible for individual variables) using rank correlations. Rank correlations allow the comparison of the species among cultural significance gradients and are not affected by scale or methodological differences between studies. Some subjects that could be assessed with this approach are: the relative position of species within the whole CS estimates, the relative position of species within each cultural domain and the relative weight of each variable determining de CS of species in different cultural contexts. These data are necessary to answer why cultures use some resources from their surroundings and no others? Why different societies use different species even if they are exposed to similar environments? How does human societies structure their subsistence strategies in function of what they have and what they believe? In sum, to give a step forward to a more integrative and explicative ethnobiology.
Caution must be taken when using compound indexes; as they imply a question for every variable for each species known by an informant, wise informants have to deal with a huge number of questions. In our case knowledgeable ones answered 7 questions by 21 species; that was a questionnaire of 147 questions that toke at least 3–4 hours. This spent much time and disposition from the interviewee or two or three sessions to complete the task. Furthermore, if more variables, more species or bigger informant samples are to be included, serious logistic efforts as long field journeys, enough resources and interviewees time must be considered.
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