My multidisciplinary research program integrates field, laboratory and museum work to understand the evolutionary processes shaping the origin, maintenance, and distribution of biodiversity. I am particularly interested in the role thattemporal and spatial environmental change play in shaping mammalian diversity. This encompasses a nuanced understanding of patterns of divergence and ecological adaptation across environmental gradients, and assessing how distinct traits can lead to diverse evolutionary paths under similar environmental conditions. Understanding the intricate interplay between environmental change and species traits in shaping natural populations is fundamental for predicting their responses to different aspects of ongoing global change. Additionally, I am interested in species delimitation, particularly within contexts of morphological conservatism or high ecophenotypic variation. Species delimitation is a cornerstone in evolutionary biology, playing a crucial role in advancing our understanding of spatial patterns of species richness and endemicity. This knowledge provides valuable insights for those designating areas of conservation priority. Furthermore, better understanding the diversity of tropical mammalian reservoir hosts is essential to identifying the sources of emerging zoonotic diseases.
Study system
Most of my research is focused on small mammals, an evolutionarily heterogeneous group including non-volant species belonging to the orders Rodentia (rodents), Eulipotyphla (shrews, moles, hedgehogs and solenodons) and Scandentia (treeshrews) that usually weight less than 1 kg. The small size of these mammals has also led to ecological specialization, a relatively low vagility, fast generation times, and consequently, generally high speciation rates, making them an excellent group to test evolutionary and biogeographic hypotheses (Camacho-Sánchez, 2017). The high speciation rate of different small mammal lineages has contributed to high levels of diversity (Burguin et al., 2018). High levels of diversity generally imply high levels of undescribed diversity (Moura et al., 2021). The two most species-rich mammalian orders (Rodentia and Chiroptera) have experienced the most species additions since 2005: 371 and 304 species, respectively (Burguin et al., 2018). Thus, small mammals represent an exciting and promising study system for species discovery. Recently, I have broadened my research scope to two additional mammalian orders: Chiroptera and Pholidota.
In the figure, major mammalian lineages are delineated based on my research contributions. Those lineages for which I have published research are denoted by an orange highlight, while lineages with taxa currently under investigation, yet to be published, are distinguished by a blue highlight.
Understanding drivers and patterns of mammalian diversification in Southeast Asia
Southeast Asia (SEA) comprises the biogeographical subregions of Indochina, Sundaland, the Philippines, and Wallacea, which are among the hottest global hotspots, considering their high numbers of endemics and high habitat loss. Yet these regions still hold significant potential for future species discoveries. This regions intricate geological and climatic history, coupled with its complex topography also offers an ideal setting to investigate evolutionary processes that contribute to high biodiversity levels. However, the geographical and political complexity of SEA poses great challenges, leading to limitations in sampling and often constraining the geographical scope of regional studies. Such studies hinder a comprehensive understanding of the drivers shaping diversification of this region's rich mammalian fauna. The advent of Next Generation Sequencing (NGS) technology has transformed our field, making it possible to accomplish these research goals. NGS complements traditional field surveys and transcends historical sampling limitations through the application of museum genomics. This technology leap enables researchers to contribute to more robust phylogenomicinferences and precise divergence dating in this highly complex and dynamic region.
My research has brought light to an emerging paradigm shift regarding the factors driving mammalian diversification in SEA. Contrary to the conventional view of allopatric diversification mediated by Pleistocene eustatic sea level changes in Sundaland, my findings unveil a substantial role played by ecological barriers and/or adaptation in steering diversification processes across the region (Hinckley et al. 2020, 2021, 2023a, 2023b). It supports ancient environmental-driven diversification in Indochina during the Miocene-Pliocene (Hinckley et al. 2023a, 2023b), highlights Borneo and Sumatra as centers of in situ diversification (Hinckley et al. 2020, 2021, 2023b), and indicates disparate evolutionary histories in taxa co-distributed across the Isthmus of Kra environmental transition (Hinckley et al. 2023a, 2023b, in preparation). My studies underscore the crucial role that SEA mountains have played and can continue to play as habitat refugia amid past and future climate-change-induced aridification (Hinckley et al. 2023a).
Species tree of Sundaland and Sulawesi Crocidura as estimated from 13 nuclear loci using *BEAST. (Hinckley et al. 2021).
Relief map of tropical east Asia showing the Isthmus of Kra (IOK), Kangar-Pattani Line (KPL), a major transition of mammal species distributions (MTMS), and names of various geographic places (a), and localities of samples used (points) and distributions (darker grey areas) of the study species of Hinckley et al. (2023a)
My research seeks to further understand the mechanisms that have shaped the origin, maintenance, and distribution of SEA mammalian diversity: a) adaptation to varied climates; b) the role mountains play, leading to local adaptation and divergence, or serving as habitat refugia/vicariant barriers during climate shifts; c) connections and disconnections of Sundaland's landmasses driven by eustatic sea level fluctuations; d) alterations in major Indochinese river basins' paths and flows potentially acting as physical barriers, leading to isolation.
Species delimitation and integrative taxonomy using genomic and morphological approaches
Understanding species limits is fundamental to biology, ecology, and conservation. Both species delimitation and integrative taxonomy contribute to our understanding of evolutionary processes, including speciation, adaptation, the development of biodiversity over time, and biodiversity distribution patterns. I approach species delimitation through an integrative framework including museum genomics, qualitative morphological analyses, craniodental linear morphometrics, baculamicro CT scanning, citizen science, bioacoustics, and environmental niche modeling. The consistency observed among various lines of evidence and analytical methods enables me to thoroughly assess species hypotheses across a diversity of mammalian orders in Asia and Africa’s tropics.This concerted effort contributes not only to the identification of new species but also to a better understanding of the evolutionary dynamics within hyperdiverse mammalian orders, such as Rodentia and Eulipotyphla.
By combining museum and field sampling efforts, my research has highlighted an important species-level diversity underestimation in Lesser Gymnures, Crocidurashrews, and squirrels (Callosciurus, Dremomys, Sundasciurus, and Tamiops). These studies have led to the elevation of nine subspecies to specific status (Hinckley et al. 2020; Hinckley et al. 2023b; Hinckley et al. in review) and to the formal description of two new species of gymnures (Hinckley et al. 2023b). Simultaneously, my research has also synonymized /ID isolated and narrow-ranged shrew species/populations that are nested within the diversity of widely distributed species (Hinckley & Leonard, 2020; Hinckley et al. 2021). Overall, my studies highlight emerging patterns of localized endemicity in N Sumatra, S Annamites, NE India, and the Natunas.
Higher-level phylogenomics: Insights from small mammal genomes
Exciting updates coming soon! This section is under construction.