Climate change, lemurs and recent megafaunal extinctions
Creators: name: University Of California Office Of The President
Publisher: name: University of California Office of the President
publisherIdentifier: https://ror.org/00dmfq477
publisherIdentifierScheme: ROR
Year: 2024

description: Lemurs, a unique adaptive radiation of primates, have been evolutionarily isolated on the island of Madagascar for nearly 50 million years. At least 15 additional species, some of which were gorilla-sized, succumbed to extinction during the past 2,000 years. Their existence is recorded predominantly in the Holocene subfossil record. We have employed the use of stable carbon and nitrogen isotopic analysis to better understand the ecology of these extinct species, and to compare the isotopic ecologies of extinct and extant subfossil to those of modern lemur taxa. Relative to modern trends, subfossil localities show a large amount of isotopic variation, with an overall tendency towards lower carbon and nitrogen isotopic values in all modern specimens. Additionally, there is a substantial amount of isotopic overlap between specimens from different ecoregions. Climatic shifts could be responsible for the observed isotopic variation. Alternatively, if surviving lemurs have shifted their residence to more closed forests in response to habitat loss and direct hunting pressure, a change in lemur behavior could be the reason for lower isotopic values in modern lemurs. Due to climatic shifts and anthropogenic disturbances, Madagascar has undergone dramatic changes over the last 5,000 years. For example, landscape transformations related to slash and burn agriculture, charcoal production, and introduced livestock have all likely contributed to the demise of the extinct megafanua. Yet despite an overarching trend towards gradual aridification, palynological data and the co-occurrence in subfossil localities of extant species that are typically only found in allopatric populations today suggest that Madagascar has experienced intermittent periods of low and high aridity throughout the Pleistocene and Holocene. The result of these climatic cycles is that localities typified by one type of habitat today (e.g. succulent woodland) may have been dominated by other habitat types in the past (e.g. wooded savanna or moist forest). To validate our isotopic analyses, it is necessary to place our data in a firm temporal framework. Without reliable and accurate chronological information, we cannot assess if isotopic variability within paleo-communities is real, or merely an artifact of time averaging. Published data do not provide detailed temporal resolution and stratigraphic information was not recorded for most specimens. Additionally, over half of the published dates are not accompanied by any information about how the specimens were cleaned or prepared, making many of the existing dates suspect. Constructing a detailed chronology of our subfossil specimens will allow us to 1) control for specimen age in our comparisons, and 2) address important questions about the timing and implications of ecological shifts, (e.g. the co-occurrence of “sympatric” taxa at subfossil sites). Accordingly, we propose to radiocarbon date each specimen at the Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory. This collaboration between UCSC faculty, a UCSC graduate student, and an LLNL staff scientist will mutually benefit the missions of LLNL and the University of California. Results are expected to further elucidate the regional timing of faunal extinctions and the effects of climate versus behavioral shifts in lemurs. Additionally, results will have a broad impact on the field of evolutionary biology and will lay the groundwork for future paleoecological work in Madagascar.