Considering that their distribution is limited to altitudinal gradients along mountains that are likely to become warmer and drier, climate change poses an increased threat to temperate forest species from tropical regions. We studied whether the understorey shrub Lupinus elegans, endemic to temperate forests of west-central Mexico, will be able to withstand the projected temperature increase under seven climate change scenarios. Seeds were collected along an altitudinal gradient and grown in a shade-house over 7 months before determining their temperature tolerance as electrolyte leakage. The plants from colder sites tolerated lower temperatures, i.e. the temperature at which half of the maximum electrolyte leakage occurred (LT50), ranged from −6.4 ± 0.7 to −2.4 ± 0.3 °C. In contrast, no pattern was found for tolerance to high temperature (LT50 average 42.8 ± 0.3 °C). The climate change scenarios considered here consistently estimated an increase in air temperature during the present century that was higher for the maximum air temperature than for the mean or minimum. In particular, the anomaly from the normal maximum air temperature at the study region ranged from 2.8 °C by 2030 to 5.8 °C by 2090. In this respect, the inability of L. elegans to adapt to increasingly higher temperatures found here, in addition to a possible inhibition of reproduction caused by warmer winters, may limit its future distribution.

Pinus pseudostrobus Lindl. is the forest species most important economically in the state of Michoacán, at central-west México. We investigated genetic variation among P. pseudostrobus populations along an altitudinal gradient in the native indian community of Nuevo San Juan Parangaricutiro, Michoacán, México. Cones were collected from eight populations at 100 m of altitudinal intervals between 2200 m and 2900 m. Seedlings were grown for approximately two years in two shadehouse environments at Morelia, Michoacán, México and at Moscow, Idaho, USA. Total height was periodically measured during the second growing season to estimate a series of growth indexes for both locations, and dry weights were obtained only for the Morelia test. For the Moscow test there were significant differences (P < 0.05) among populations for cessation of growth, duration of the growth period, and final height. For the Morelia tests there were differences among populations for foliage, shoot and total dry weight (P < 0.025), and significant differences for stem dry weight at P = 0.055 level. There was a strong altitudinal cline for dry weight variables, with seedlings originated from populations from the lowest altitudes having more biomass (r2 = 0.80, P = 0.003). Populations separated altitudinally by about 295 m are likely to be genetically different. We suggest delineation of three altitudinal seed zones (Zone I: 2100 m to 2400 m; Zone II: 2400 m to 2700 m; Zone III: 2700 m to 3000 m), that can be translated into climatic zones delimited according to mean annual temperatures or by degree days > 5 °C. To accommodate climate change we suggest implementing assisted migration programs by transferring populations 300 m upwards to maintain adaptiveness of populations for future climates.

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.

En México fueron afectadas alrededor de 17,900 ha de bosques de coníferas en 2016 a causa de los brotes de insectos descortezadores. Se ha observado que el aumento en las temperaturas ocasionadas por el cambio climático afecta directamente a los bosques de pino y favorece el desarrollo de insectos plaga. Los gradientes altitudinales generan gradientes climáticos, por lo cual, son buenos modelos de estudio en un contexto de cambio climático. El objetivo del estudio fue determinar el efecto de la temperatura y la abundancia de Dendroctonus frontalis y Dendroctonus mexicanus a lo largo del rango de distribución altitudinal, así como determinar un posible cambio en la abundancia para 2030 bajo un escenario de cambio climático. Los resultados evidenciaron que la mayor abundancia de D. frontalis y D. mexicanus se encuentra en altitudes entre los 1,589 y 1,716 msnm, donde ocurren temperaturas superiores a 16 °C, y en altitudes mayores a los 2,393 msnm la abundancia de ambas especies es menor, correspondiendo a temperaturas menores a 13°C. El escenario A1B de cambio climático predice que la temperatura aumentará del 2015-2016 al año 2030 3.9 °C en promedio.

Geographically disparate populations within a species’ range may show important differences including variation in ecological, demographic, genetic and phenotypic characteristics. Based on the Center-Periphery Hypothesis, it is often assumed that environmental conditions are optimal in the geographic center of the range and stressful or suboptimal at the periphery, implying ecological marginality is concordant with geographic periphery. But this assumption has been challenged as geographical and ecological gradients are not necessarily concordant. The conservation value of populations inhabiting environmentally marginal areas is still under debate and is closely related with their evolutionary potential. Strong selective pressures caused by stressful conditions may generate novel adaptations in marginal areas, conferring these populations distinct evolutionary potential. But populations inhabiting marginal areas may also show reductions in neutral and adaptive genetic diversity via drift and inbreeding.In this work we explore the potential of ecological niche models (ENMs) to identify environmentally optimal and marginal areas, as well as the principal putative selective pressures likely to act. To do so, we built a carefully parameterized ENM of Silene ciliata, a dominant plant species of Mediterranean alpine habitats. Complementarily, we selected wild populations inhabiting contrasting environmental conditions and carried out common garden experiments to detect genetic differentiation among populations associated with functional traits. With the resulting information, we tested whether environmentally marginal populations defined by the ENM had genetically differentiated phenotypes that are potentially adaptive and, thus, of conservation value.We found genetically based phenotypic differentiation of phenological traits between populations inhabiting areas identified by the ENM as marginal and optimal, as well as between populations with different habitat suitability values. Results supported ENMs as powerful tools for determining environmental marginality and identifying selection pressures, and thus also as hypothesis generators for divergent selection. Furthermore, genetically based phenotypic differentiation found underlines the potential adaptive value of populations inhabiting marginal areas. The approach developed here provides a theoretically justified and practical way to study adaptive processes and provide insights about the conservation value of marginal populations.

No abstract

Lupinus elegans is a species used in ecological restoration and agroforestry programs, because it is tolerant to stress and fixes nitrogen. Genetic variation in quantitative traits was studied in six populations of L. elegans collected along an altitudinal gradient (2312 to 2885 m) in the Mil Cumbres region, east-central Michoacán state, México. Provenance tests were planted at 2600 and 2800 m altitude in two common garden field trials. Tests aimed to evaluate the performance at a different altitude than the site of the seed source, simulating an altitudinal-assisted migration. Survival, plant height growth and aerial biomass were measured. For each provenance and experimental sites, climatic variables were estimated for contemporary climate (average 1961-1990) and future climate (decade centered in 2030, by averaging six model scenarios). It was estimated that by the year 2030 there will be, on average, an increment of 1.4 °C in mean annual temperature, an increase of 518 degree-days > 5 °C (DD5), a 90 mm decrease in mean annual precipitation (MAP) (-7.3 % of contemporary MAP), and a 0.0077 increase in an aridity index (DD50.5/MAP). An ANOVA for each site revealed that in the higher altitude site (2800 m) populations exhibited a pronounced pattern of genetic differentiation (P = 0.0001), in which plant height and biomass are associated with the transfer distance between their place of origin and the experimental site. This distance can be expressed in difference in altitude, mean annual temperature, or aridity index. At the site at higher altitude, plants originated from populations growing at higher altitudes were taller and had more biomass than those originated grown at lower altitudes (R2 ≥ 0.85, P ≤ 0.0302). In contrast, in the lower altitude site (2600 m), although there were nearly significant differences (P ≤ 0.0615) between populations for all of the variables, there was no clinal pattern. In general, the populations grew less when they were moved away from their original climate: those from the higher altitudes grew less in the 2600 m site, and those from the lower altitudes grew less in the 2800 m site. This indicates that climate change will likely induce less growth in several populations, thus it is recommended to promote gradual assisted migration.

The response of plants to altitudinal gradients depends on several factors and might differ among life strategies. Understanding these responses is highly relevant for management of forest species, particularly under climate change scenarios. We explored the response to drought of different provenances of Lupinus elegans, obtained from an altitudinal gradient. This species is a shrub that acts as a nurse plant in temperate forests in its geographical range. Seeds were collected from five natural provenances across an altitudinal gradient (2312 m to 2885 m a.s.l.). A common-garden experiment was conducted with four drought treatments (irrigation at every 3, 7, 15 and 21 days) in a shade-house located at 1972 m a.s.l. All provenances presented reduced heights and numbers of leaves with increased drought intensity, regardless of site of origin. Survival among provenances presented an altitudinal pattern, where those belonging to higher sites exhibited greater survival. Provenances from lower altitudes, coming from drier and warmer sites, exhibited poorer survival against drought stress. Overall, our results indicate that there are differences among provenances, but since this species is a short lived perennial (five years on average), it is more sensitive to microclimate than to conditions determined for large scale patterns such as altitudinal gradients. This should be considered for management practices such as ecological restoration.Estrés por sequía en Lupinus elegans procedentes de diferentes altitudesLa respuesta de las plantas a los gradientes altitudinales depende de varios factores y puede variar entre estrategias de vida. Entender esta respuesta es relevante para el manejo de especies forestales, en particular ante los efectos esperados del cambio climático. En este trabajo se exploró la respuesta a la sequía de diferentes procedencias de Lupinus elegans, obtenidas de un gradiente altitudinal. Esta especie es un arbusto que actúa como planta nodriza en bosques templados a lo largo de su área de distribución geográfica. Se colectaron semillas de cinco procedencias a los largo de un gradiente altitudinal (2312 m a 2885 m snm). Se llevó a cabo un experimento de jardín común con cuatro tratamientos de sequía (riego cada 3, 7, 15 y 21 días) en una casa de sombra localizada a 1972 m snm. Las plantas de todas las procedencias mostraron un menor tamaño y número de hojas conforme aumentó el grado de sequía, independientemente de la procedencia. La supervivencia entre las procedencias mostró una relación con el gradiente altitudinal de origen, pues aquellas procedentes de sitios a mayor altitud mostraron mayor supervivencia. Las procedencias de altitudes menores, que en principio son de lugares más secos y cálidos, mostraron baja supervivencia en respuesta a la sequía. Los resultados indican que hay una diferenciación entre procedencias, pero que siendo esta especie perenne de vida corta (5 años), es más sensible a las condiciones microclimáticas que a las condiciones determinadas por patrones a escalas mayores como son los gradientes altitudinales. Esto debe de ser considerado para prácticas de manejo como la restauración ecológica.