4.1 The variables selected for the MaxEnt model
Table S1 shows seven environmental
and human population densities and eight bioclimatic variables were
selected to establish MaxEnt models describing macaques’ evolutionary
changes and future distribution profiles. Three of them, the
precipitation of the warmest quarter (var8), the mean
temperature of the driest quarter
(var5), and the human population density (var16), are those playing a
decisive role in setting up the models for the current (1970-2000) and
future (the 2050s) distribution profiles (Figure S5).
Rainfall
and other water sources are crucial
for animals’ survival, which can constrain their geographical
environment and habitat selections; such as, elephants’ movement closely
tracks precipitation-driven vegetation dynamics in a Kenyan
forest-savanna landscape (Bohrer et al.,
2014). One of the main reasons causing many mammal species to become
extinct is the drought in the Later Pleistocene and the early Holocene
(Jukar et al., 2021), such as that
occurred in some macaque species, Macaca sylvanus in Norfolk
(Elton and O’Regan, 2014) and Greece
(Konidaris et al., 2022), Macaca
majori in Italy (Zoboli et al., 2016),Macaca cf. M. cyclopis and Macaca anderssoni in
China (Chang et al., 2012;
Ito et al., 2014). Studies of climate
impacts on the distribution of extant non-human primates have been few
(Bernard and Marshall, 2020;
Stewart et al., 2020); regarding that
related to the taxa in China, it is reported that isothermality and
temperature of the driest quarter are critically affecting the
distribution of the gray-white snub-nosed monkey (Rhinopithecus
bieti ) – temperature might act as a reproductive regulator for the
onset of estrus and mating season (Zhao
et al., 2019).
The extant macaque taxa now primarily reside in tropic-subtropic and
temperate regions in North Africa and Asia
(Mittermeier et al., 2013;
Galán-Acedo et al., 2019), less
tolerating droughty climates (Fleagle and
Gilbert, 2006). A positive relationship between habitat suitability and
precipitation for Macaca (Figure S6) is like what was described
in primate species in Southeast Asia (Wang
et al., 2013); less rainfall would
limit their access to food sources due to poor leaf and fruit production
(Rosenzweig, 1968;
Wang’ondu et al., 2013). This study
implies that climatic conditions or fluctuation would continue to be
essential in driving macaques’ diversity and distribution.
Unsurprisingly, the human population density variable is the primary
driving force shaping macaques’ future geographical changes by reducing
habitat suitability (Figure S6). Intensified anthropogenic activities
have also followed human population growth, leading to significant
increases in cropland, pasture, and rangeland since the 1950s in China
– the human population size increased from 540 million in 1949 to 1.4
billion in 2020
(Jo Huth, 1990) in which, cropland
increased by 2549.2×104 hm2 from
1949 to 2003, increasing 47.2×104hm2/year (Bi and Zheng,
2000; Feng et al., 2005). Pastures and
croplands have separated suitable distributions and migration paths,
which have blocked genetic
exchanges and caused population
reduction and extinction (Forman and
Alexander, 1998; Saxena et al., 2020).
Such a scenario applies explicitly to some macaque populations in Shanxi
(Zhou, 2014).