Corresponding author: José Luis Villaseñor (
Academic editor: Anatoliy Khapugin
Little attention has been paid in Mexico to species’ geographical distribution, particularly documenting geographic ranges, as a tool to estimate their conservation status. The objective of this study was to review known species distribution and propose potential and conservation status for
National Autonomous University of Mexico, Mexico, City.
The authors declare that there is no conflict of interest regarding the publication of this manuscript.
Numerous studies document species richness in several regions all over the world; unfortunately, knowledge on the geographic ranges for most of these species is lacking. The few existing reports are often biased by collecting at easily-accessible regions, whereas remote areas are under-sampled. Incomplete sampling has a direct effect on spatial distribution conceptions and negatively influence biogeographic interpretations (
Although much effort has been made to assess species geographic distribution in Mexico, nonetheless, documenting geographical ranges occupied by plants species has been sparse (
The genus' taxonomy has been adequately studied for the western Mexican State of Michoacán.
The State of Michoacán is amongst the top five most
Despite extensive research on the taxonomy of
The present research aims to better characterise the distribution of
We reviewed the most relevant
Given the taxonomic complexities of the group, with frequent synonymy changes, we only considered the species that were reported in at least two of those studies and that could be corroborated with herbarium specimens. Discrepancies in the
The database was corrected following the recommendations by
Pattern analysis was applied to the data for all species using the Ilwis v.3.4 programme (
In addition to the review of the specimens in the herbarium, specimens cited in taxonomic works of the study group were also considered. For the species and specimens with taxonomic circumscription issues, the specimens were individually evaluated to determine whether or not to include them in the analyses. The outliers identified in the pattern analysis were reviewed to confirm the identity from a genus specialist; the specimens that were not approved by the specialist, were excluded from the database.
The polygon for the state of Michoacán was divided into 118 grid-squares of 15' latitude and 15' longitude; a finer scale grid would have resulted in no species being represented. Thus 15' x 15' grid was a compromise between the distribution, collection effort and the number of grids. Geographic information was analysed in ArcGIS 10.2 (
Fifty eight environmental variables were considered, with a resolution of 30 arc seconds, a pixel size of about 1 km2 (Table
Species distribution result from several factors; amongst the most important ones are environmental variables (A), biotic component (B) and the set of sites that has been accessible to the species (M).
Evaluating models using spatially independent data improves model configurations and balances their complexity. There are several methods for identifying optimal model configuration (
Maxent 3.4.1 software (
Results from Maxent were then processed in ArcGIS 10.2 (
We partitioned the data into training and testing groups (k-fold cross validation), allowing us to evaluate models’ performance (
The models were evaluated using the AUC, a value that is part of Maxent's results. AUC values range from 0 to 1, where values close to 1 indicate models with perfect discrimination ability and values less than 0.5 indicate that the model is no better than a randomly-generated model (
To assess the conservation status of the genus
A list of 66 species was obtained for the Mexican State of Michoacán (Suppl. material
The political territory of Michoacán comprise five ecoregions;
The
Individual models for
The known richness in Michoacán, depicted in 15' x 15' grids (Fig.
Niche models are here reported for four
The altitude for these species is variable, although 81% of them are distributed between 2000 and 2500 m a.s.l. The number of species decreases, both at lower (< 500 m) and higher altitudes (> 3000 m).
A total of 26 uncorrelated variables (of the initial 58) were considered to run the ENMs for each
We obtained 42 ENMs of
All models (made by default setting and configured) showed good performance, AUC values above 0.84 were considered good, 19% (AUC > 0.8) and 81% excellent (AUC > 0.9, Table
The geographic area obtained with the assembly of models for the
Ten Protected areas in Michoacán harbour potential distribution areas of
The
Undoubtedly, 1,925 records representing 66 of the 69 species occurring in the State (
Our results indicate that
The majority of
Rare species (< 3 records), although not modelled, show a preference for similar environmental conditions as compared to modelled species or widely-distributed species (> 3 records). For example, the mean temperature of rare species (18°C) is slightly higher than that of widely-distributed species (15.7°C), while in precipitation, the mean values are very similar, 1,057 mm for rare species and 1,058 mm for widely-distributed species. Furthermore, several state endemic
Environmental suitability is indicated for the genus along the SMS (Fig.
Although the large amount of information in the databases would seem sufficient for ENMs and thus inferring many species distribution, this was not always the case. When performing statistical analyses to develop more robust and precise models, such as eliminating spatial autocorrelation of points to reduce sampling
The AUC has been criticised as a tool to evaluate only the performance of presence models, because of its dependence on prevalence; therefore, it is not considered a precise performance index (
High deforestation rates in the north-central region of Michoacán, is the main cause of habitat loss. The most vulnerable vegetation types are temperate forests, constantly being replaced by avocado orchards (
Protected areas represent a key strategy for biodiversity preservation (
The results point to the TMVB, the SMS and the JDF as priority ecoregions for
We are grateful to CONABIO and the Instituto de Biología, UNAM, for access to the information stored in the SNIB-REMIB and UNIBIO databases, respectively, which constituted a fundamental part of the analyses presented here. Thanks to Enrique Ortiz and Joselin Cadena Rodriguez for reviewing a draft of the manuscript and two anonymous reviewers; their assistance improved substantially the document. In addition, Enrique Ortiz helped in several facets of the study with his technical assistance. We appreciate Lynna Kiere’s editing of the English version.
M.F.T. and J.L.V., conceived the project, designed the methods, conducted the statistical analysis and species distribution modelling. M.F.T., J.L.V and S.I.L.C interpreted the results, authored the writing and approved the final draft.
The authors declare that there is no conflict of interest regarding the publication of this manuscript.
Known distribution of the genus
Known and potential distribution of the genus
Examples of potential distribution areas of species of
Floristic and taxonomic studies accounting for species diversity of
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4 | 52 | 52 |
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64 | 493 | 439 |
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3 | 5 | 1 |
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14 | 189 | 97 |
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62 | 695 | 479 |
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69 | None | None |
|
3 | 19 | 6 |
70 | 768 | 1,925 |
Variables used to estimate the ecological niche models of
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bio02 (Average daytime variation) | |
bio03 (Isothermality) | |
bio14 (Precipitation of driest month) | |
bio15 (Seasonality of precipitation) | |
bio18 (Precipitation of the warmest quarter) | |
bio19 (Precipitation of the coldest quarter) | |
evaanual (Annual real evapotranspiration) | |
|
aspect (Orientation 0° to 90°) |
convrgin (Convergence index) | |
dah (Diurnal anisotropic heating) | |
mexslope (Slope) | |
runoff (Flow) | |
twi (Topographic moisture index) | |
vrm (Vector rugosity measure) | |
|
mexca (Calcium) |
mexce (Electrical conductivity) | |
mexco (Organic carbon) | |
mexk (Potassium) | |
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|
mexmo (Organic material) | |
mexna (Sodium) | |
mexras (Sodium absorption radius) | |
* |
modismar (Normalised index of vegetation March) |
modissep (Normalised index of vegetation September) | |
hummodis2009 (Normalised index of vegetation humid months) |
Species of
Species | Total records/records |
Potential area |
AUC | Partial ROC | Binomial test |
14/5 | 3286.3 | 0.972 | 1.7 |
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15/7 | 8281.8 | 0.934 | 1.90 |
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* |
44/4 | 3727.1 | 0.962 | 1.38 |
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* |
6/4 | 1576.0 | 0.986 | 1.83 |
|
47/12 | 19895.3 | 0.837 | 1.56 | 0.913 (1.16 x 10-10) | |
8/5 | 3388.1 | 0.971 | 1.91 |
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32/15 | 11831.4 | 0.89 | 1.29 |
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130/25 | 11912.2 | 0.874 | 1.56 | 0.795 (3.46 x 10-13) | |
95/10 | 9306.3 | 0.909 | 1.67 | 0.770 (1.36 x 10-11) | |
* |
8/3 | 1982.4 | 0.988 | 1.97 | 0.607 (0.02) |
57/17 | 3516.7 | 0.985 | 1.59 | 0.575 (0.006) | |
48/7 | 2873.0 | 0.979 | 1.93 | 0.930 (4.55 x 10-13) | |
* |
23/4 | 1853.2 | 0.974 | 1.23 |
|
138/20 | 7989.4 | 0.896 | 1.49 | 0.556 (0.002) | |
57/18 | 12436.1 | 0.932 | 1.59 | 0.887 (3.73 x 10-11) | |
* |
9/4 | 291.8 | 0.995 | 1.85 |
|
34/14 | 8340.8 | 0.934 | 1.17 |
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102/15 | 16136.8 | 0.883 | 1.25 | 0.647 (6.33 x 10-6) | |
16/5 | 2505.2 | 0.987 | 1.46 |
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76/13 | 12802.5 | 0.928 | 1.41 | 0.578 (0.003) | |
37/8 | 18161.9 | 0.926 | 1.45 | 0.712 (5.19 x 10-5) | |
* |
4/3 | 16.8 | 1 | 1.99 |
|
11/5 | 2705.5 | 0.972 | 1.61 |
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206/24 | 7161.9 | 0.861 | 1.51 | 0.508 (0.03) | |
38/6 | 12920.7 | 0.9 | 1.31 | 0.521 (0.03) | |
55/19 | 10142.5 | 0.854 | 1.23 |
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35/14 | 10954.4 | 0.925 | 1.71 | 0.793 (1.05 x 10-5) | |
20/12 | 2008.3 | 0.981 | 1.94 | 0.529 (0.04) | |
55/13 | 6165.0 | 0.963 | 1.69 | 0.663 (0.0003) | |
96/11 | 18053.7 | 0.838 | 1.39 | 0.768 (2.31 x 10-11) | |
* |
4/3 | 171.0 | 0.997 | 1.99 |
|
13/5 | 707.6 | 0.993 | 1.71 |
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62/10 | 9902.8 | 0.899 | 1.32 |
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* |
4/4 | 5217.0 | 0.948 | 1.87 |
|
55/12 | 7664.7 | 0.952 | 1.47 | 0.577 (0.004) | |
* |
6/4 | 2073.6 | 0.985 | 1.95 |
|
34/6 | 16430.3 | 0.877 | 1.32 |
|
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* |
6/4 | 912.5 | 0.99 | 1.97 |
|
* |
11/4 | 2404.5 | 0.976 | 1.66 |
|
70/15 | 6612.8 | 0.882 | 1.13 |
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40/7 | 12192.5 | 0.913 | 1.25 |
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15/8 | 7186.5 | 0.933 | 1.21 |
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List of specimens of
Specimens
Each record is made up of the collector’s last name and collecting number; in parentheses the herbaria where the specimen is stored, followed by the coordinates in decimal degrees. In brackets, the publications in which the records are cited is indicated. 1: Espejo-Serna and Ramamoorthy (1993); 2: Cornejo-Tenorio and Ibarra Manríquez (2011); 3: Iltis et al. (2012); 4: González-Gallegos et al. (2014); 5: González-Gallegos et al. (2016); 6: Lara-Cabrera et al. (2016); 7: recorded in SNIB-REMIB and/or MEXU-UNIBIO databases.
File: oo_464475.docx
Species of
List of species
The number of records obtained for each species after cleaning the data from the SNIB-REMIB and MEXU-UNIBIO databases are indicated.
File: oo_464477.pdf
Ecological niche models of 42
Images
Ecological niche models of 42
File: oo_464478.pdf
Configuration of Maxent
Evaluation metrics
Evaluation metrics of Maxent ENMs generated with the ENMeval programme for the three species of
File: oo_433111.doc