Identifying long-term stable refugia for relict plant species in East Asia

Abstract

Today East Asia harbors many "relict" plant species whose ranges were much larger during the Paleogene-Neogene and earlier. The ecological and climatic conditions suitable for these relict species have not been identified. Here, we map the abundance and distribution patterns of relict species, showing high abundance in the humid subtropical/warm-temperate forest regions. We further use Ecological Niche Modeling to show that these patterns align with maps of climate refugia, and we predict species' chances of persistence given the future climatic changes expected for East Asia. By 2070, potentially suitable areas with high richness of relict species will decrease, although the areas as a whole will probably expand. We identify areas in southwestern China and northern Vietnam as long-term climatically stable refugia likely to preserve ancient lineages, highlighting areas that could be prioritized for conservation of such species.

Fig. 1

Relict species richness and rarity-weighted richness. a Relict species richness of genera endemic to East Asia. b Rarity-weighted richness of relict species of genera endemic to East Asia. c Relict species richness of genera having disjunct distributions between East Asia and other parts of the world. d Rarity-weighted richness of relict species of genera having disjunct distributions between East Asia and other parts of the world. The summer monsoon limit line adapted from Chen et al., showing the approximate limit of modern summer monsoon precipitation. For the national boundary between China and India, please see Supplementary Fig. 2A and Methods. Maps were generated using the software ArcGIS v. 10.5 (ESRI, Redlands, CA, USA) and modified using Canvas 12 (ACD Systems of America, Inc., Seattle, WA, USA). Map layers were obtained from site www.gadm.org

Fig. 2

Distribution of relict forest stands in East Asia. a Relict forest stands overlaid on a potential forest vegetation zone model and mountain profile of East Asia. The potential forest vegetation zone model is modified from Ohsawa. b–d Latitudinal and longitudinal distribution of relict forest stands in East Asia. For the national boundary between China and India, please see Supplementary Fig. 2A and Methods. Maps were generated using the software ArcGIS v. 10.5 (ESRI, Redlands, CA, USA) and modified using Canvas 12 (ACD Systems of America, Inc., Seattle, WA, USA). Map layers were obtained from site www.gadm.org

Fig. 3

A comparison of potential richness of relict species under the present climate and climatic scenarios in the past. a–g For potential richness of relict species of genera endemic to East Asia: a under the present climate; b–d under scenarios mid-Holocene-CCSM4, mid-Holocene-MIROC-ESM, mid-Holocene-MPI, respectively; e–g under scenarios LGM-CCSM4, LGM-MIROC-ESM, LGM-MPI, respectively. h–n For potential richness of relict species of genera having disjunct distributions: h under the present climate; i–k under scenarios mid-Holocene-CCSM4, mid-Holocene-MIROC-ESM, mid-Holocene-MPI, respectively; l–n under scenarios LGM-CCSM4, LGM-MIROC-ESM, LGM-MPI, respectively. For the national boundary between China and India, please see Supplementary Fig. 2A and Methods. Maps were generated using the software ArcGIS v. 10.5 (ESRI, Redlands, CA, USA) and modified using Canvas 12 (ACD Systems of America, Inc., Seattle, WA, USA). Map layers were obtained from site www.gadm.org

Fig. 4

A comparison of potential richness of relict species under the present climate and climatic scenarios in the future (2070). a–g For potential richness of relict species of genera endemic to East Asia: a under the present climate; b–d under scenarios 2070-CCSM RCP 2.6, 2070-GFDL RCP 2.6, 2070-MPI RCP 2.6, respectively; e–g under scenario 2070-CCSM RCP 8.5, 2070-GFDL RCP 8.5, 2070-MPI RCP 8.5, respectively; h–n For potential richness of relict species of genera having disjunct distributions: h under the present climate; i–k under scenarios under scenarios 2070-CCSM RCP 2.6, 2070-GFDL RCP 2.6, 2070-MPI RCP 2.6, respectively; l–n under scenarios 2070-CCSM RCP 8.5, 2070-GFDL RCP 8.5, 2070-MPI RCP 8.5, respectively. For the national boundary between China and India, please see Supplementary Fig. 2A and Methods. Maps were generated using the software ArcGIS v. 10.5 (ESRI, Redlands, CA, USA) and modified using Canvas 12 (ACD Systems of America, Inc., Seattle, WA, USA). Map layers were obtained from site www.gadm.org

Fig. 5

Overlap of potential richness of relict species of the four time frames climatic scenarios. a–e For relict species of genera endemic to East Asia: a Overlap of the present and the past (LGM, mid-Holocene); b, c Overlap of the present and the future (2070) (under scenarios of RCP 2.6 for b, RCP 8.5 for c); d, e Overlap of the present, the past and the future (under scenarios of RCP 2.6 for d, RCP 8.5 for e). f–j For relict species of genera having disjunct distributions: f Overlap of the present and the past; g, h Overlap of the present and the future (under scenarios of RCP 2.6 for g, RCP 8.5 for h); i, j Overlap of the present, the past and the future (under scenarios of RCP 2.6 for i, RCP 8.5 for j). For the national boundary between China and India, please see Supplementary Fig. 2A and Methods. Maps were generated using the software ArcGIS v. 10.5 (ESRI, Redlands, CA, USA) and modified using Canvas 12 (ACD Systems of America, Inc., Seattle, WA, USA). Map layers were obtained from site www.gadm.org

Fig. 6

Climatic variables in different categories of suitable areas of relict species. a Long-term stable refugia (red areas) of relict species of genera endemic to East Asia under scenarios Present-Past-Future RCP 2.6. Maps were generated using the software ArcGIS v. 10.5 (ESRI, Redlands, CA, USA) and modified using Canvas 12 (ACD Systems of America, Inc., Seattle, WA, USA). Map layers were obtained from site www.gadm.org. b–f Five climatic variables in different categories of suitable areas of relict species of genera endemic to East Asia in four time frames. g–k Value range of the standard deviation (SD) of each climatic variable in different categories of suitable areas. LGM, Last glacial maximum; M-Hol, Mid-Holocene; Pres, Present; Fut, Future (2070). b–k Boxplot representation: center line (median), upper end line whisker (maximum value), upper box bound (75th percentile), lower box bound (25th percentile), lower end line whisker (minimum value)