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Kooyman, Robert [1], Ivory, Sarah J. [2], Benfield, Adam J. [2], Wilf, Peter [2].

Living Paleo-Antarctic Rainforest Genera in Southeast Asia: Community Assembly, Potential Future Ranges, and Paleo-Conservation.

The Southeast Asian rainforest region is extremely complex and biodiverse, stretching from continental Asia through the Malay Archipelago to New Guinea and northern Australia. Across vast expanses of time and geography, fossils and their living relatives show that paleo-Antarctic rainforest lineages (PARLs) that now inhabit Asia tracked the ever-wet, mesic conditions needed to survive and diversify. The deep-time fossil history of the PARLs highlights their persistence in the face of major Cenozoic climate shifts, moving continents, and extinction events. Today, the PARLs remain important to the diversity and ecological function of many rainforest areas, including refugia in the modern Asian tropics. However, on the geologically instantaneous timescale of human disturbance, much of the remaining rainforest in southeast Asia is now highly threatened. Despite their historical and contemporary role in rainforest community assembly, the contributions of PARLs have rarely been quantified ecologically and are often overlooked in molecular biogeographic studies. To quantify and visualize the floristic relationships of Island Groups in the Southeast Asian region and the contributions to community assembly of woody fossil lineages, we used recent compilations of bioregional species data consolidated to genus level, analyzed using multivariate methods (nMDS). Island Group relationships to environmental gradients were evaluated based on centroid means, with key environmental vectors plotted in nMDS. Distributions of abundant and informative woody Gondwanan fossil lineages, including two angiosperms (Castanopsis – Fagaceae; Gymnostoma – Casuarinaceae) and two gymnosperms (Agathis – Araucariaceae; Dacrycarpus – Podocarpaceae) were explored at fine scale to identify how key survivor lineages are distributed relative to climate variables. We used generalized linear models of genus occurrences and gridded climate information to project both current and 2100 CE distributions under an RCP 8.5 trajectory, which assumes no reduction in CO2 emissions. The coarse-scale (nMDS) analyses showed strong similarity among Island Groups in the core ever-wet forest area of Malesia where PARLs are often concentrated, and several outliers represented more seasonal locations. Increasing seasonality of rainfall and higher seasonal temperatures constrained the potential future distributions of ancient lineages, with significant differences among the exemplar genera apparent in the models. The potential distributions of the selected genera often mapped onto areas where current clearing and dispersal barriers seem likely to inhibit the capacity of lineages to relocate. Our results highlight the profound combined impacts of rapid climate change, habitat destruction, and natural, especially marine barriers on paleo-conservation values and contemporary rainforest community assembly processes in Southeast Asia.

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1 - Department of Biological Sciences, Macquarie University, Sydney, New South Wales, 2109, Australia
2 - Pennsylvania State University, Dept. of Geosciences, University Park, PA, 16802, USA
3 - Pennsylvania State University, Dept. of Geosciences, University Park, PA, 16802, USA

Distribution models
Communiy assembly
climate change
Dispersal barriers.

Presentation Type: Oral Paper
Session: PL8, Paleobotany: Patterns & Trends
Location: /
Date: Thursday, July 22nd, 2021
Time: 3:30 PM(EDT)
Number: PL8003
Abstract ID:585
Candidate for Awards:None

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