634 Y. Liu et al.
et al., 2006). Following examination of the correlation coef- ficients and the contributions of the 19 bioclimatic variables, we selected four to predict the potential distribution of the species (Fig. 3): temperature seasonality (Bio_4), min- imum temperature of coldest month (Bio_6), temperature annual range (Bio_7) and precipitation of wettest month (Bio_13). In the MaxEnt simulation the two highest- contributing factors were Bio_4 (57.1%) and Bio_7 (19.1%), which together accounted for 76.2%of the total contribution (Table 1).
Potential distribution under current and future climate conditions
FIG. 2 The (a) height and (b) diameter at breast height of all 53 individuals of M. lacei found during our surveys in China.
Hu; Sun et al., 2019a, 2019b; Linsky & Sun, 2022). In 1987, Kunming Botanical Garden planted 12 M. lacei individuals, all of which have grown into trees .10 m tall and are in good condition. Four have flowered, and two have also fruited.
Model performance and the importance of environmental variables
The AUC values of the ROC curve were .0.9 in all pre- dicted future periods, indicating that the simulation of the area potentially suitable for M. lacei is credible (Phillips
In addition to the known current distribution in Yunnan, our model suggests areas of suitable habitat in Xizang, Sichuan, Guizhou, Guangxi, Guangdong, Fujian, Taiwan and Hainan (Fig. 4a). However, during our literature searches, we found no record of M. lacei in China beyond Yunnan Province. Within Yunnan, predicted suitable habitat under current conditions is mainly in the west and south-east (Fig. 4b). In western Yunnan, the moderately and highly suitable areas are predominantly in Dehong, and in south-eastern Yunnan these areas are predominantly in Wenshan and Honghe. Of the potentially suitable habitat in Yunnan, 59%(19.38 × 105 km2) had only low suitability, 33%(10.87 × 105 km2) was moderately suitable and 8% (2.70 × 105 km2) was highly suitable. Of the total habitat in Yunnan Province, 16% is unsuitable for M. lacei (6.46 × 105 km2; Table 2). For each future period we predicted habitat suitability in
Yunnan for the four Shared Socioeconomic Pathways (Fig. 5; Table 2). The largest areas of unsuitable and low suit- ability habitat were both predicted under the worst-case scenario (SSP585), with unsuitable habitat of 8.66 × 105 km2 predicted during 2061–2080, and low suitability habitat of 28.06 × 105 km2 predicted during 2081–2100. We pre- dicted areas of moderately and highly suitable habitat to be greatest under the SSP126 scenario during 2041-2060, at 18.05 × 105 and 2.81 × 105 km2, respectively. Figure 6 shows the changes in the future potential distri-
PLATE 1 (a) The largest Michelia lacei individual on record, found during our surveys in Yunnan Province, China, in 2022, and (b) flower bud, (c) flower and (d) fruit.
bution of M. lacei compared to that under current condi- tions, showing areas of expansion, areas with no change in suitability (the areas are suitable neither in the future nor at present), areas of stability (the areas are suitable during both periods) and areas of contraction. The highest increase in area of suitable habitat is 1.58 × 105 km2 under SSP585 during 2081–2100. Under the SSP585 scenario during 2061–2080 the area suitable for M. lacei decreased by 2.62 × 105 km2 compared to the present. Based on current and future cli- mate data, we predict that as climate conditions change in the future an increasingly large area will be transformed into habitat with low suitability for M. lacei.
Oryx, 2024, 58(5), 631–640 © The Author(s), 2024. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605323001783
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