Figura 2 - uploaded by Carlos Avila-Bello
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a. Valor reproductivo de los diferentes estadios de Abies hickelii (escala logarítmica) en el Pico de Orizaba, Veracruz, México. Obsérvese la baja contribución de las plántulas y árboles jóvenes al valor reproductivo debido a la ausencia de transición a la etapa adulta.
Source publication
Abies hickelii is an endangered fir species, restricted to Chiapas, Oaxaca and Veracruz, Mexico; on the ear of Orizaba Mountain, Veracruz, its area of distribution is used for grazing and logging. Stands of A. hickelii protect the upper Jamapa River basin in Veracruz. In order to assess whether the species is in danger we performed a quantitative d...
Citations
Interacting stochastic and selective forces drive population and species divergence. Such interaction may generate contrasting clines between genetic and phenotypic factors, which can be related to either geographical or environmental variation depending on the predominant evolutionary force (which in its turn is partly determined by population size). Here, we investigated whether the morphological and genetic differentiation across a species complex in Abies in central Mexico fits isolation by distance (IBD) or isolation-by-adaptation (IBA) frameworks. This complex includes two species (A. religiosa and A. flinckii) with discernible morphological and environmental differences and dissimilar range sizes. After comparing variation at nuclear SSR loci and diagnostic morphological traits of needles with the climate variables contributing to ecological differentiation, we found that the widely distributed A. religiosa has more genetic diversity and is morphologically more heterogeneous than the geographically restricted A. flinckii. Morphological differentiation at three physiologically important traits (needle thickness, number of stomata rows and location of the resin duct) is significantly correlated with geography in A. flinckii (indicative of IBD), but is significantly associated with climate variation in A. religiosa (suggesting IBA). In agreement with quantitative genetics theory, PST (phenotypic differentiation)-G’ST (genetic differentiation) comparisons indicate contrasting contributions of putatively adaptive (A. religiosa) and stochastic (A. flinckii) factors to the morphological differentiation of species related to their population size. The integration of such quantitative genetic/evolutionary aspects may reinforce species descriptions and help in disentangling resilient taxonomic discordance.
