Linking ecological niche models and common garden experiments to predict phenotypic differentiation in stressful environments: Assessing the adaptive value of marginal populations in an alpine plant.

Environmental variation within a species' range can create contrasting selective pressures, leading to divergent selection and novel adaptations. The conservation value of populations inhabiting environmentally marginal areas remains in debate and is closely related to the adaptive potential in changing environments. Strong selection caused by stressful conditions may generate novel adaptations, conferring these populations distinct evolutionary potential and high conservation value under climate change. On the other hand, environmentally marginal populations may be genetically depauperate, with little potential for new adaptations to emerge. Here, we explored the use of ecological niche models (ENMs) linked with common garden experiments to predict and test for genetically determined phenotypic differentiation related to contrasting environmental conditions. To do so, we built an ENM for the alpine plant Silene ciliata in central Spain and conducted common garden experiments, assessing flowering phenology changes and differences in leaf cell resistance to extreme temperatures. The suitability patterns and response curves of the ENM led to the predictions that: (1) the environmentally marginal populations experiencing less snowpack and higher minimum temperatures would have delayed flowering to avoid risks of late-spring frosts and (2) those with higher minimum temperatures and greater potential evapotranspiration would show enhanced cell resistance to high temperatures to deal with physiological stress related to desiccation and heat. The common garden experiments revealed the expected genetically based phenotypic differentiation in flowering phenology. In contrast, they did not show the expected differentiation for cell resistance, but these latter experiments had high variance and hence lower statistical power. The results highlight ENMs as useful tools to identify contrasting putative selective pressures across species ranges. Linking ENMs with common garden experiments provides a theoretically justified and practical way to study adaptive processes, including insights regarding the conservation value of populations inhabiting environmentally marginal areas under ongoing climate change.

Abundancia altitudinal de Dendroctonus frontalis (Coleoptera: Curculionidae) en relación a variables climáticas en Hidalgo, México

Los descortezadores Dendroctonus frontalis (Coleoptera: Scolytidae) son un grupo de coleópteros estrechamente ligado a las masas forestales y son una de las plagas más dañinas en México, ocasionando que la cobertura forestal se reduzca considerablemente. Adicionalmente factores como el cambio climático, favorecen el aumento en las poblaciones de escarabajos descortezadores del género Dendroctonus. Por lo anterior es conveniente conocer la variación poblacional de descortezadores, particularmente de Dendroctonus frontalis, cuyas poblaciones dependen de la variabilidad climática que influye en su abundancia. Teniendo como hipótesis que la altitud y las variables ambientales afectan el comportamiento en la abundancia de D. frontalis, se planteó como objetivo estimar la variación espacio-temporal de poblaciones de D. frontalis en bosques de pino a diferentes altitudes. El estudio se realizó en la comunidad de Durango, Zimapán, Hidalgo, México. Se utilizó un diseño experimental de parcelas apareadas con dos tratamientos, de feromona y testigo. Se colocaron siete trampas con ambos tratamientos en un rango de 1 568 a 2 117 m.s.n.m. para determinar la abundancia altitudinal de D. frontalis. El muestreo se llevó a cabo de enero a diciembre 2015. Se obtuvo una relación positiva entre la abundancia de D. frontalis y el gradiente altitudinal y respecto a la abundancia de D. frontalis y la temperatura se observó una relación moderada, pero no significativa; de la misma forma para la precipitación media anual. La relación con la temperatura media máxima y el balance de precipitación de primavera/verano fueron estadísticamente significativos. Se presentó una tendencia positiva en la abundancia de D. frontalis de acuerdo al índice anual de aridez, por lo cual se espera que con el aumento de las temperaturas el estrés en la vegetación de los bosques sea mayor, favoreciendo el incremento de las poblaciones de escarabajos descortezadores.

The bark beetles Dendroctonus frontalis (Coleoptera: Scolytidae) are a group of coleoptera closely linked to forest masses, and one of the most harmful pests in Mexico, causing the forest cover to be considerably reduced. Additionally factors such as climate change, favor the increase in populations of bark beetles of the genus Dendroctonus. Taking as a hypothesis that altitude and environmental variables affect the behavior in the abundance of D. frontalis, the objective was to estimate the temporary-spatial variation of D. frontalis populations in pine forests at different altitudes. The study was conducted in the community of Durango, Zimapán, Hidalgo, Mexico. An experimental design of paired plots with two treatments was used, pheromone and control. Seven traps were placed with both treatments in a range of 1 568 to 2 117 m.a.s.l. to determine the altitudinal abundance of D. frontalis. The sampling was realized from January to December 2015. A positive relationship was observed between the abundance of D. frontalis and the altitudinal gradient. About the abundance of D. frontalis and the temperature, a moderate but not significant relationship was observed in the same way for the average annual precipitation. The relation with the maximum average temperature and the spring summer precipitation balance were statistically significant. There was a positive trend on the abundance of D. frontalis according to the annual aridity index, which is why it is expected that the increase of temperatures the stress in the vegetation of the forests will be greater, favoring the increase of bark beetles populations.