Lianas as a food resource for herbivorous insects: a comparison with trees

Abstract

Woody climbers or, 'lianas', are one of the features that characterise rainforests. They contribute substantially to plant diversity and leaf biomass which makes them a potentially important food source for herbivores. Here, we focus on insect herbivores, folivores in particular, to show how disparities in the quantitative and qualitative availability of leaves between lianas and trees may differentially influence insect folivory and the herbivore communities themselves. We develop a conceptual model and show that lianas in general have lower structural and chemical defences, a greater nutritional profile and a preferable phenology in comparison with trees, which, contrary to our expectations, has led to assemblages of more-specialised insects. The impacts this has on higher trophic levels and broader ecological networks, however, are poorly known. We show through a study of four tropical floras from different biogeographic realms that lianas are likely to be a target for a wide range of insect herbivore taxa as they are a phylogenetically diverse group and increase diversity of higher taxa at local scales. This, in combination with their highly palatable leaves, may also make them a suitable temporary food source for insects during times when preferred host plants are scarce. This phenomenon has been observed in mammalian herbivores but awaits investigation in insects as does the effects this may have on survival and fitness. Apparent recent increases in liana abundances in some forests, likely due to climate change, makes understanding their role in supporting and maintaining biodiversity an increasingly important and necessary challenge. Since trees or saplings have usually been the subject of studies on insect herbivory, major knowledge gaps remain about the ways in which lianas contribute to, support and maintain the ecosystems in which they exist. We use our conceptual model to guide future research directions and express the necessity for caution when extrapolating explanations of herbivory derived from data on trees to growth forms with fundamentally different ecologies.

Conceptualising the Global Forest Response to Liana Proliferation

“…important for maintaining biodiversity (Schnitzer and Carson, 2001). Accordingly, lianas may enhance recovery from disturbance, including soil (Tang et al, 2012), seed diversity (César et al, 2017) and fauna (Ødegaard, 2000;Arroyo-Rodríguez et al, 2015), and may provide protection from fire (Uhl et al, 1988), lightning (Yanoviak, 2013), wind (Putz, 1984b), cyclones (Unwin et al, 1986), weeds (Goosem and Tucker, 2013) and herbivory (Odell et al, 2019). We collectively refer to these protective influences of lianas as their "bandage effect".…”

Lianas maintain insectivorous bird abundance and diversity in a neotropical forest

“…Lianas may generally benefit insectivorous birds by increasing the abundance of arthropods (Ødegaard 2000, Yanoviak and Schnitzer 2013, Adams et al 2019, Odell et al 2019. Lianas add a complex array of stems to the forest understory, which provide food sources for herbivorous insects (i.e., liana leaves and stems).…”

“…Liana fruits, flowers, leaves, and stems are also valuable food resources to the animal community. Thus, lianas increase heterogeneity throughout the vertical profile of tropical forests, which can provide myriad habitat and food resources that maintain animal abundance and diversity (Yanoviak and Schnitzer 2013, Arroyo‐Rodriguez et al 2015, Lambert and Halsey 2015, Adams et al 2017, Odell et al 2019).…”

Environmental filtering and spatial processes shape the beta diversity of liana communities in a valley savanna in southwest China

“…Lianas are one of the key growth forms in tropical and subtropical forests (Schnitzer & Bongers, 2002), which are important for providing canopy connectivity, food sources, and habitats for animals (Schnitzer & Bongers, 2002; Odell et al. , 2019). Previous studies have shown that lianas employ acquisitive strategies, i.e.…”