Figure 1.
Relationships between fundamental niches, realized niches, potential niches and geographic distributions as (a) a Venn diagram (after [36], [157]); (b) in climatic niche space (E-space); and (c) in geographic space (G-space).
A species' realized niche (R) is the intersection of its fundamental niche (F), its accessible climate or territory (A), and the climate and territory not barred by biotic interactions (B). Its potential niche (P) is the subset of the fundamental niche for which there is available climate (A), and its potential distribution is the territory with climate tolerable to the species. (F ∩ P) is the range of climate or geography that is climatically tolerable to a species but which is not accessible because of the lack of climate availability (E-space) or geographic barriers (G-space). A fossil may occur in E-space within the species' potential distribution (1), outside the range of available paleoclimate (2), or in paleoclimates which are available but actually not suitable (3). See text for details.
Table 1.
Comprehensive overview of phylogeographic and morphometric analyses of North American turtle species.
Figure 2.
Predicted current species richness according to 100% and 90% environmental envelopes (A) as well as historic fluctuations as projected for the last glacial maximum 21 ky BP (B) and the last interglacial (C) according to palaeophylogeographic models of 59 Nearctic chelonians.
Dispersal capacities per species were restricted to the corresponding watersheds (D). For full videos see Appendix S4 in Material S1.
Figure 3.
Relationships between pairwise changes in mean annual temperatures (MAT) and pairwise changes in potential distribution range sizes as well as between MAT and pairwise changes in geographic centers of potential distributions in 59 Nearctic chelonians during the last 320 ky.
Warmer colors reflect higher point densities considering both climate and phylogenetic effects (top panel), only climate (middle panel) and only phylogeny (bottom).
Figure 4.
Historic niche dynamics in Nearctic chelonians based on 141 fossils and the five most proximal (SIM5) 50 km2 points in climate space in those cases where species find no analogous climates to their past potential niche.
Positive MESS scores indicate conditions within the species' modern potential niche and negative MESS scores indicate bioclimatic conditions outside of the modern potential niche. Solid lines refer to the complete set of fossils (black) and SIM5 points (gray), wherein dotted lines refer to subsets nested across all variables within the species' potential niche. Percentages provided in each subplot refer to the proportion of records within the species' current realizable niche and the respective subsets (total/within potential niche/outside of potential niche) for fossils (F) and SIM5 (S). Dashed lines refer to subsets of exeeding those conditions currently available to the species in at least one predictor. Abbreviations are: BIO1 = annual mean temperature; BIO2 = mean diurnal range; BIO3 = isothermality; BIO4 = temperature seasonality; BIO5 = max temperature of warmest month; BIO6 = min temperature of coldest month; BIO7 = temperature annual range; BIO8 = mean temperature of wettest quarter; BIO9 = mean temperature of driest quarter; BIO10 = mean temperature of warmest quarter; BIO11 = mean temperature of coldest quarter; BIO12 = annual precipitation; BIO13 = precipitation of wettest month; BIO14 = precipitation of driest month; BIO15 = precipitation seasonality; BIO16 = precipitation of wettest quarter; BIO17 = precipitation of driest quarter; BIO18 = precipitation of warmest quarter; BIO19 = precipitation of coldest quarter; MESS: Multivariate Environmental Similarity Score.
Table 2.
Summary statistics for fossil occurrences in Nearctic chelonians in terms of availability and niche position relative to the species' modern niches (for more details see Appendix S3 in Material S1).
Table 3.
Multivariate environmental similarity scores (MESS) for fossils that fell outside the potential distribution of their species. Negative scores indicate the distance outside the potential niche as a percentage of the niche's size.