INSECTOS DESCORTEZADORES (COLEOPTERA: CURCULIONIDAE) Y CAMBIO CLIMÁTICO: PROBLEMÁTICA ACTUAL Y PERSPECTIVAS EN LOS BOSQUES TEMPLADOS

Ecological Niches and Suitability Areas of Three Host Pine Species of Bark Beetle Dendroctonus mexicanus Hopkins

Bark beetles are a natural part of coniferous forests. Dendroctonus mexicanus Hopkins is the most widely distributed and most destructive bark beetle in Mexico, colonizing more than 21 pine species. The objectives of this study were to generate ecological niche models for D. mexicanus and three of its most important host species, to evaluate the overlap of climate suitability of the association Dendroctonus–Pinus, and to determine the possible expansion of the bark beetle. We used meticulously cleaned species occurrence records, 15 bioclimatic variables and ‘kuenm’, an R package that uses Maxent as a modeling algorithm. The Dendroctonus–Pinus ecological niches were compared using ordination methods and the kernel density function. We generated 1392 candidate models; not all were statistically significant (α = 0.05). The response type was quadratic; there is a positive correlation between suitability and precipitation, and negative with temperature, the latter determining climatic suitability of the studied species. Indeed, a single variable (Bio 1) contributed 93.9% to the model (Pinus leiophylla Schl. & Cham). The overlap of suitable areas for Dendroctonus–Pinus is 74.95% (P. leiophylla) and on average of 46.66% in ecological niches. It is observed that D. mexicanus begins to expand towards climates not currently occupied by the studied pine species.

Reciprocal Common Garden Altitudinal Transplants Reveal Potential Negative Impacts of Climate Change on Abies religiosa Populations in the Monarch Butterfly Biosphere Reserve Overwintering Sites

Research Highlights: Reciprocal altitudinal transplants of Abies religiosa seedlings within the Monarch Butterfly Biosphere Reserve (MBBR) allow prediction of the impacts of climatic change, because they grow in sites with a climate that differs from that of their origin. Background and Objectives: Climatic change is generating a mismatch between the sites currently occupied by forest populations and the climate to which they have adapted. This study determined the effect on the survival and growth of A. religiosa seedlings of transfer to sites that were warmer or colder than that of the origin of their seeds. Materials and Methods: Eleven provenances of A. religiosa, collected along an altitudinal gradient (3000 to 3550 m a.s.l.), were assayed in common gardens in three sites of contrasting altitude: 3400, 3000 and 2600 m a.s.l. The results were evaluated by fitting a response curve with a mixed model. Results: The climate transfer distance for the seasonal balance between the temperature conducive to growth (degree days above 5 °C) and the available precipitation (a ratio expressed as dryness index) dominated the shape of the response function curve. The rainy season (June–October) dryness index transfer distance was critical for survival, while that of the cold and dry season (November–February) was critical for aerial biomass, and the annual index was critical for the increase in basal diameter. The effect of climatic transfer distance is much more negative (triggering about 45% mortality) when transfer is toward warmer and dryer sites (at 400 m lower in altitude, +1.9 °C warmer and 16% less precipitation), than when shifting toward colder and wetter sites (400 m higher in altitude, resulting in 95% survival). Conclusions: The projected higher temperatures and lower precipitation due to climatic change will undoubtedly cause severe mortality in young A. religiosa seedlings. A 400 m shift upwards in altitude to compensate for climatic change (assisted migration) appears to be a feasible management action.