Foliage Chemistry Influences Tree Choice and Landscape Use of a Gliding Marsupial Folivore

Abstract

The chemical quality of forage may determine landscape use and habitat quality for some herbivorous species. However, studies that investigate the relationship between foliar chemistry and foraging choices in wild vertebrates are rare. Petauroides volans (the greater glider) is unique among Australian marsupial folivores because it glides. It also frequently consumes foliage from both major Eucalyptus subgenera, Eucalyptus (common name "monocalypt") and Symphyomyrtus (common name "symphyomyrtle"), which differ markedly in their foliar chemistry. Such differences are thought to be a product of co-evolution that also led to guild-specific plant secondary metabolite (PSM) specialization among other marsupial eucalypt folivores. To explore whether foliar chemistry influences tree use, we analyzed foliage from eucalypt trees in which we observed P. volans during a radio tracking study and from eucalypt trees in which animals were never observed. We used a combination of chemical assays and near infrared spectrophotometry (NIRS) to determine concentrations of nitrogen (N), in vitro available nitrogen (AvailN), and in vitro digestible dry matter (DDM) from foliage sampled from the monocalypt and symphyomyrtle species, and total formylated phloroglucinol compounds (FPCs) and sideroxylonals (a class of FPCs) from the symphyomyrtle species (FPCs do not occur in monocalypts). Tree size and spatially-dependent, intraspecific variations in sideroxylonals and DDM concentrations in the symphyomyrtle foliage and of N, AvailN, and DDM in the monocalypt species were important indicators of tree use and habitat suitability for P. volans. The results i) demonstrate that guild-specific PSMs do not always lead to guild-specific foraging; ii) provide a compelling co-evolutionary case for the development of gliding in P. volans; and iii) have implications for the management and conservation of this and other folivorous species.

Where the wild things are: using remotely sensed forest productivity to assess arboreal marsupial species richness and abundance

“…In support of optimal foraging theory (Stephens & Krebs, 1986), we found a strong relationship between NDVI and (1) the relative abundance and likelihood of observing P. volans among eucalypt forest sites, (2) the location of P. volans within eucalypt forest transects and (3) the overall abundance of the P. volans in five eucalypt forest remnants. Studies of captive and wild populations suggest that P. volans is limited by the low concentrations of foliar nitrogen in eucalypts (typically 1-2 percentage, Foley & Hume, 1987;Kavanagh & Lambert, 1990;Youngentob et al, 2011). Notably, nitrogen is believed to be less of a limiting factor for the other, more generalist marsupial folivores, and in particular P. peregrinus, which uses cacophony and has a specialized caecum to overcome potential nitrogen limitations (McArthur & Sanson, 1991;Moore et al, 2004).…”

Improving biodiversity monitoring

“…Some of these new technologies will facilitate connections between on-ground monitoring methods and data collection with other large-scaled approaches like remote sensing (e.g. Youngentob et al 2011). In addition, genomic analysis of floral, faunal and environmental samples (soils and water) are also rapidly developing and have the capacity to use surrogate species to rapidly monitor ecosystem health (e.g.…”

Comparative dietary ecology of two congeneric marsupial folivores

“…In Australia, marsupial arboreal folivores have evolved a diverse set of behavioural, morphological and physiological adaptations (see Hume 2004;Wiggins et al 2006b) to cope with the nutrient-poor, sclerophyllous and highly toxic foliage characteristic of native flora (Noble 1989;Specht & Rundel 1990;Irlbeck & Hume 2003;Wallis et al 2010). Recently, our understanding of the interactions between the genus Eucalyptus and the suite of marsupial folivores specialized to feed on it (the koala, Phascolarctos cinereus; greater glider, Petauroides volans; common ringtail possum, Pseudocheirus peregrinus; and common brushtail possum, Trichosurus vulpecula) has increased dramatically (Moore & Foley 2000Wallis et al 2010;Youngentob et al 2011), resulting in a major change in our understanding of the variation in dietary physiology between these species. Captive trials have demonstrated that eucalypt folivores display differential susceptibility to co-occurring plant defence chemicals, with different folivore species being specialized to cope with different suites of plant secondary metabolites (Marsh et al 2003).…”