1. Introduction
Over the years, global ecological changes and environmental devastation triggered by human-induced activities and climate alteration have increased globally (Ofori et al., 2017; Measey et al., 2019). We are now facing enormous pressures that are driving geographic distribution patterns of plants and animals (Behroozian et al., 2020; Gainsbury, 2020), altering ecological community structure (Zhou et al., 2017), and impacting ecosystem stability (Karimi et al., 2021). Such threats have led to significant animal migration, extinction, and population reduction in the Quaternary (Chen et al., 2011; Hoffmann and Sgrò, 2011), resulting in more than 75% alteration in contemporary terrestrial ecosystems (Venter et al., 2016), following extensive agricultural changes and deforestation (Gries et al., 2019), and accelerated expansion of urbanization (Eötvös et al., 2018; Duncan et al., 2020).
Thus, ecological changes and human-induced activities during the Quaternary, which have remarkably caused climate changes and faunal and floral geographic alterations, have created unprecedented biodiversity diminishing and conservation pressures (Worm et al., 2006; D’Agata et al., 2016). Changes in species’ geographical range result in compelled migration towards suitable habitats, while some species that cannot respond rapidly are pushed to extinction (Radchuk et al., 2019; Doherty et al., 2021). Such as, mountain lions (Puma concolor ) exhibited significant antipredatory behavior changes in response to habitat alteration, resulting in a 34% reduction in their distribution (Suraci et al., 2019), forcing them to abandon high-risk home ranges (Schuette et al., 2013). Following global warming, glaciers, and sea ice melting rapidly, the population of polar bears (Ursus maritimus ) at the southernmost end of the Arctic region has declined sharply (Derocher et al., 2004). Such combined impacts in the 21st century and beyond will further alter animals’ distribution, causing the extinction of many wildlife species in the Sixth Mass Extinction (Struebig et al., 2015; Gouveia et al., 2016). Such phenomenon especially applies to non-human primates, who are more sensitive to those changes and entirely dependent on forested ecosystems (Estrada et al., 2017; Zhang et al., 2019b). That is why over 60% of extant global species are on the edge of extinction (Estrada et al., 2017; Carvalho et al., 2019). Regarding the situation in mainland East Asia, such a scenario is even more gloomy – approximately 80% of the 28 primate species are threatened (Li et al., 2018).
The macaques (Macaca ) in the subfamily Cercopithecinae have 23 species in Africa and Asia (Roos et al., 2019). Their dispersal scenarios from Africa to Asia were driven by the environmental changes in the Miocene (Zinner et al., 2013; Roos et al., 2014; Zhang et al., 2022): they originated in Africa and started the migration to Europe and Asia following the collision of the Afro-Arabian plate with Eurasia during the Oligocene-Miocene (23.8-18 Mya), which created a land connection between Arabia and Southwest Asia, making many animal taxa migrated from Africa, via Europe, to Asia since the Miocene (Roos and Zinner, 2015), including macaques. In other words, macaques’ evolutionary development and distribution patterns have been remarkably driven by climate, ecological, and geographic changes since the Miocene, except for the Barbary macaques (Macaca sylvanus) left in North Africa. The other macaque taxa finally settled down in Southwest China during the Pliocene. They continued distributing to East and South Asia through alternative dispersal paths during the Quaternary (Li et al., 2020; Zhang et al., 2022). Eight extant species are now distributed in mainland East Asia: rhesus macaques (Macaca mulatta ), the northern pig-tailed macaque (M. leonina ), the stump-tailed macaque (M. arctoides ), Formosan rock macaque (M. cyclopis ) in Taiwan, Assamese macaque(M. assamensis ), the Tibetan macaque (M .thibetana ), the Arunachal macaque (M. munzala ), and the white-cheeked macaque (M. leucogenys ). They are classified as Class Ⅱ or Ⅰ of Nationally Protected Wildlife in China and are included on the IUCN Red List of threatened species (IUCN, 2022). Over the past two millennia, global climate change and human activities (including dramatic population explosion and resource depletion, agricultural expansion, overexploitation, etc.) have led to severe fragmentation of suitable habitats and gradual habitat degradation of suitable habitats for macaque species, resulting in a progressive decline in population size (Li et al., 2015; Zhao et al., 2021). Although some macaque species have experienced population growth due to effective conservation measures, others are still on the verge of extinction, with meager numbers of individuals in the wild and a lack of systematic and comprehensive data on their status and distribution. Thus, the conservation of macaques in China faces a significant challenge (Li et al., 2020; Huang et al., 2021). It is necessary to perform further studies on these species to provide scientific and practical conservation measures referring to their geographical changes during the Quaternary.
Species Distribution Models (SDMs) are statistical tools based on environmental and species distribution data to estimate species preferences for habitat, which are widely used to explore the trajectories of geographic changes (Guisan et al., 2013). Some studies based on a few environmental and ecological variables were made on M. assamensis(Regmi et al., 2018; Khanal et al., 2019), M .leonina and M . mulatta(Sun et al., 2020). However, using only current occurrence data to train SDM may reflect incomplete species ecological niches that cannot match past climatic environments, likely offering limited information to dynamically identify the drivers of their early declines leading to their current reduced population status (Scheele et al., 2017). Paleontological fossils provide unique perspectives for exploring the past existence of species in time and space (Lentini et al., 2018). Until now, relatively few studies have combined fossil data with SDM to provide a longer time-scale perspective for geographic changes and management of threatened animals due to difficulties in data collection and quantification of long-time-scale ecology (Nogués-Bravo et al., 2016; Gibson et al., 2019). Establishing dynamic spatial-temporal distribution models, referring to the alterations of climate, vegetation types, geological features, anthropogenic activities, and evolutionary changes, is demanded to make a tangible conservation strategy, especially in expecting their shifting direction and survival prospects. Such a model allows us to identify appropriate possible geographic changes, which can be referred to conservation measurements in advance. Macaque (Macaca) in mainland East Asia, including fossil and extant taxa, and their distribution profiles from the beginning of the Quaternary (Late Pleistocene) to the present can provide ideal materials for such an endeavor. Thus, this study’s aims: 1) with the variables relevant to the changes in the environment, climate, ecology, geography, and human-induced activities to establish the models reconstructing macaques’ past, current, and future distributions patterns of suitable habitats during the Quaternary; 2) identify the significant factors driving such changes; and 3) establish a database-driven geographic model for macaques.