Epiphyte sensitivity to a cross-scale interaction between habitat quality and macroclimate: an opportunity for range-edge conservation

Abstract

Bioclimatic envelope models are frequently used to project the species response to climate change scenarios. Development and improvement of bioclimatic models has focussed on data properties and statistical tools, while significant criticism continues to challenge the ecological framework of model assumptions. We hypothesised that a potential for model improvement emerges from linkage across scales, between macroclimate and variation in local habitat quality: i.e. a species' habitat specificity may shift along macroclimatic gradients. We first sampled two test-case epiphytic lichen species across a steep climatic gradient, and second developed standard bioclimatic models accompanied by a threshold likelihood value for discriminating presences and absences. We used the difference between predicted model values and the threshold as a response variable (D thr ): we show that values for D thr are explained by an interaction between the climatic setting and habitat quality. A potential error in bioclimatic models is then quantified as the region of false absences or presences, which would be incurred as a consequence of sensitivity to variable habitat. This signature habitat effect occurs at a species' range-edge, and, as a corollary, provides quantification in support of conservation: i.e. information is provided on how a habitat may be managed in marginal climatic regions (leading or trailing range-edge boundaries) in order to promote species protection.

Trait‐dependent distributional shifts in fruiting of common British fungi

“…Combining the annual temperature and precipitation with the temperature difference between coldest and warmest month, we calculated a hygrothermic index (HT) reflecting the transition from continental (low values) to oceanic climate conditions (Lisewski and Ellis 2010): For each VC and year, we calculated each species' average geographical position, measured by latitude and longitude.…”

“…While we appreciate that higher resolution data may have provided more accurate representations of climate, such data were not available for the time period covered by this study. Combining the annual temperature and precipitation with the temperature difference between coldest and warmest month, we calculated a hygrothermic index (HT) reflecting the transition from continental (low values) to oceanic climate conditions (Lisewski and Ellis 2010):…”

Climate Change, Bioclimatic Models and the Risk to Lichen Diversity

“…Species local distribution, with respect to the breadth of forest/woodland habitats occupied, can change across their geographic range [186,187]. Thus, increased microhabitat sensitivity at range-edges [188] can explain the association of certain species with 'old-growth' stands in suboptimal climates [189,190]. For example, oceanic lichen species may become associated with old-growth stands that are relatively more humid for a suboptimal climatic regime and which maintain greater structural diversity [191,192] providing greater availability of microclimatic refugia.…”

Response of epiphytic lichens to 21st Century climate change and tree disease scenarios

“…There is tentative evidence that this may the case, because the area with lowest values for assemblage turnover relevant to the ash-alder stand occur inland and are positioned at the point of maximum orographic rainfall over the western Scottish mountains, matching therefore the occurrence of oligotrophic and moisture-demanding species such as Micarea stipitata or Sphaerophorus globosus. Alternatively, previous work has indicated the importance of shifts in microhabitat specificity along the west-east climatic gradient in Scotland Lisewski and Ellis, 2010). It is possible therefore that oceanic species occurring with high environmental suitability in western Scotland have weakly structured association values Table 1 Values of D L envS (mean and 1 SD for 11 variants in a climate model ensemble) for upland mixed ash wood qualifying as Special Areas of Conservation (NVC stand-type W9), given the effect of (i) climate change (2050s and 2080s medium and high emissions scenarios, respectively), (ii) climate change and ash dieback, and the effect of (iii) ash replacement with sycamore, or (iv) succession to birch.…”