Predicting the distribution of a novel bark beetle and its pine hosts under future climate conditions

Abstract

Understanding the distribution of key biotic elements of forest ecosystems is essential in contemporary forest management and in planning to meet future management needs. Habitat distribution (niche) models based on known occurrences provide geographical structure for such management as the environmental factors change. Bark beetles play critical roles in coniferous forest dynamics in western North America. Among these insects, Dendroctonus rhizophagus Thomas and Bright, which occurs in the Sierra Madre Occidental in Mexico, is unique in that it attacks only immature trees (Pinus spp.) and therefore represents a threat to forest regeneration. We developed current habitat distribution models for D. rhizophagus and its Pinus hosts and projected these to future climate scenarios. Predicted suitable habitat of D. rhizophagus currently covers approximately 119 000 km2 of which approximately 11% is occupied, and overlap with suitable habitat for all Pinus hosts exceeds 99.5%. Some suitable habitat occurs isolated from known D. rhizophagus occurrences in Mexico and the south‐western U.S.A. Habitat distribution models were projected to four potential climate scenarios for the period 2040–2060 and this predicted the gains and losses of suitable D. rhizophagus habitat throughout the region. Areas of north‐western Mexico maintain large areas of suitable D. rhizophagus and Pinus host habitat in all scenarios. Dispersal to isolated areas of D. rhizophagus habitat appears unlikely. The results of the present study can be used to target D. rhizophagus monitoring and management activities and may serve as a model for the management of other invasive species.

Forest Insects and Climate Change

“…Two native species feeding on seedlings, one scolytine beetle [64] and one weevil [65], have been considered in climatematching studies, and in both cases, there is potential for range expansion with increasing temperature under different scenarios of climate and host plants. Similarly, climate-matching provides estimates of range expansion for a few species of non-native gall makers, such as cynipid gall wasps [66,67] and sap suckers.…”

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

“…Low suitability for D. mexicanus (Figure 3a) and P. devoniana (Figure 3d) is observed only at higher latitudes and almost never at lower latitudes, challenging distributional ecology where maximum suitability of the species occurs toward the center of spaces E and G [24]. Analogously, it has been found [13] that greater suitability of D. mexicanus is registered in small portions of the TMVB and the SMOc at higher altitudes and where Pinus-Dendroctonus host diversity is high but discontinuous [14,49]. For Pinus, suitability also occurs at higher altitudes [42], possibly following regimes of higher moisture and lower temperatures.…”

“…The best fit model was selected according to: (1) the statistic partial ROC (Receptor Operated Curve) [47], (2) the rate of omission <0.05%, (3) the lowest value of the Akaike Information Criterion (AICc) [19,48,49], (4) species response curves to the environmental gradients [37], and (5) statistical significance of the model, p-values [19]. Here, the partial ROC was used instead of the area under the ROC curve (AUC) because the latter is not a good measure of fit in ENM [47,50].…”

“…The binary maps were manipulated using 'raster algebra' of each pair of species (Pinus-D. mexicanus), and SAP free of SAD were calculated. The procedures based on spatial predictions of climate suitability (also called ENMs), besides estimating SAP-SAD [49], allow quantifying changes and niche overlap of two or more species in G space [20]. [55] D and a measure derived from Hellinger's distance called I using ordination methods (PCA) and the 15 bioclimatic variables for each species [20] (Table 1).…”

Current and Potential Spatial Distribution of Six Endangered Pine Species of Mexico: Towards a Conservation Strategy

“…It is imperative to consider land use change and land cover dynamics to promote conservation strategies for each species. The Mexican territory suffers fragmentation, disturbances, and some degradation processes [59][60][61], causing changes in the structure, function, composition, productivity, and extent of forests that may contribute to the diminishing of forest species [62,63].…”