are unimportant in the determination of the species geographic ranges 8-10. However, several studies have demonstrated that the inclusion of biotic interactions in ENMs improves the performance of these models, both at local and regional scales 1,9,11-13. Epiphyte plants are a group that exemplifies the importance of biotic interactions. Such species establish and complete their entire life cycle on the bark of trees, and therefore the distribution of their host tree species strongly influence the distribution of these plants 8,14. However, despite the essential role that biotic interactions play in determining the distribution of some species, very little is known about the functioning of these ecological relationships 5,8,15. Moreover, the importance of the interactions that occur among species at the macro-scale is still subject of debate 8,16. It is expected that climate change will modify the range of an important number of species 17-20 , which may modify the composition of local communities, and may create transient communities that could be dominated by generalists species 21-23. To understand the possible effects of climate change on species distributions and ecosystem relationships, and to promote biodiversity conservation, it is essential to consider all the important drivers of the distribution of species when projecting future changes 24. For species that are highly dependent on biotic interactions, it is necessary to understand the effect of these interactions on their distributions 25,26. For example, currently interacting species may no longer occupy the same areas in the future as a result of climate change, because they could migrate at either different speeds or directions 26-28. Some biotic interactions, such as predation, competition and mutualism, are especially important for the maintenance of biodiversity 29,30 , and they can be decisive in determining the response of interacting species to climate change 11. Biotic interactions are key for evolutionary and ecological processes and mediate the responses of some species to climate 21. Similarly, climate can affect the direction, frequency and intensity of the interactions. Thus, understanding the complexity of the relationship between climate and biotic interactions is essential in order to predict the future habitat distribution of some species, especially those strongly dependent on these interactions. The establishment and abundance of epiphytic plants is largely determined by the microclimatic conditions provided by their host tree, like a protecting shadow and support well above the ground 31,32. This host-guest relationship therefore largely determines the distribution of these epiphyte species 32. Future changes in the distribution of host species due to climate change may thus act to reduce the distribution of epiphytes 11,33. Moreover, these species live in tropical forests, a habitat under particular threat due to changes in both climate and land use 34. Finally, these species are very sensitive to variations in temperature and pr...

Ecological niche models as a tool for estimating the distribution of plant communities Modelos de nicho ecológico como herramienta para estimar la distribución de comunidades vegetales

Con base en trabajo de campo realizado entre 2007 y 2010 en el cerro El Águila, la montaña más alta localizada en los municipios de Lagunillas y Morelia, Michoacán, se registraron 105 familias, 343 géneros, 633 especies y 42 taxa infraespecíficos. Las familias más diversas fueron Asteraceae (153 especies), Fabaceae (53) y Poaceae (34). Los géneros con mayor riqueza de especies fueron Salvia (17), Stevia (12) y Verbesina (11). Las especies de hierbas conforman el 72.4% del total de la flora. Se describe la fisonomía y las especies más abundantes de cinco tipos de vegetación. Los bosques de Pinus-Quercus y Quercus son los tipos de vegetación con mayor número de especies (286 y 383, respectivamente). De acuerdo con la NOM-059-ECOL-2010 se consideran cinco Especies Sujetas a Protección Especial (Cedrela dugesii, Cupressus lusitanica, Dahlia scapigera, Gentiana spathacea y Laelia speciosa) y una en Peligro de Extinción (Tilia americana var. mexicana). Se enfatiza la importancia de coordinar esfuerzos hacia la conservación del cerro El Águila, cuya flora y vegetación se encuentran amenazadas por los cambios de uso de suelo.

Regionalization through the analysis of species groups offers important advantages in conservation biology, compared to the single taxon approach in areas of high species richness. We use a systematic framework for biogeographic regionalization at a regional scale based on species turnover and environmental drivers (climate variables and soil properties) mainly of herbaceous plant species richness. To identify phytogeographic regions in the Balsas Depression (BD), we use Asteraceae species, a family widely distributed in Seasonally Dry Tropical Forest (SDTF) and the most diverse of the vascular plants in Mexico. Occurrence records of 571 species were used to apply a quantitative analysis based on the species turnover, the rate of changes in their composition between sites (β-Simpson index) and the analysis of the identified environmental drivers. Also, the environmental predictors that influence species richness in the SDTF were determined with a redundancy analysis. We identified and named two phytogeographic districts within the SDTF of the BD (Upper Balsas and Lower Balsas). According to the multi-response permutation procedure, floristic composition of the two districts differs significantly, and the richness of exclusive species in Upper Balsas was higher (292 species) than in the Lower Balsas (32 species). The proportion of Mg and Ca in the soil and the precipitation of the driest three-month period were the environmental factors with greatest positive influence on species richness. The division of geographic districts subordinated to the province level, based on diverse families such as Asteraceae, proved to be appropriate to set up strategies for the conservation of the regional flora, since at this scale, variation in species richness is more evident. Our findings are consistent with a growing body of biogeographic literature that indicates that the identification of smaller biotic districts is more efficient for the conservation of biodiversity, particularly of endemic or rare plants, whose distribution responds more to microhabitats variation.

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 Salvia species in Michoacán sState using Ecological Niche Models (ENM). We reviewed taxonomic studies for Salvia in Michoacán to compile an initial species checklist, built upon with recently-described species; all the specimens deposited in the National Herbarium were reviewed. The collection data allowed us to build niche models of Salvia species reported for Michoacán. ENM were generated for the species listed using Maxent. In order to minimise collinearity, environmental variables were selected using a Pearson correlation test. Individual models were statistically evaluated and the potential distribution models for each individual species were stacked to obtain the map of richness potential distribution in the State. A total of 66 species of Salvia are listed for Michoacán; however, ENM could only be constructed for 42 of those with ≥ 5 specimens. The environmental variable that most strongly contributed to the models was annual average temperature. The models estimated that Salvia species occupy an area of 23,541 km2 in the State, 72% in the Trans-Mexican Volcanic Belt and a second richest ecoregion is the Sierra Madre del Sur. Although only 3% of the potential distribution area for Salvia in Michoacán is within Protected Areas (PAs), nonetheless, no PA includes rare species. It will therefore be necessary to consider new protection areas or expand existing ones in order to adequately conserve Salvia richness and rarity in the State.