From ratites to rats: the size of fleshy fruits shapes species' distributions and continental rainforest assembly

Abstract

ResearchCite this article: Rossetto M, Kooyman R, Yap J-YS, Laffan SW. 2015 From ratites to rats: the size of fleshy fruits shapes species' distributions and continental rainforest assembly. Seed dispersal is a key process in plant spatial dynamics. However, consistently applicable generalizations about dispersal across scales are mostly absent because of the constraints on measuring propagule dispersal distances for many species. Here, we focus on fleshy-fruited taxa, specifically taxa with large fleshy fruits and their dispersers across an entire continental rainforest biome. We compare species-level results of whole-chloroplast DNA analyses in sister taxa with large and small fruits, to regional plot-based samples (310 plots), and whole-continent patterns for the distribution of woody species with either large (more than 30 mm) or smaller fleshy fruits (1093 taxa). The pairwise genomic comparison found higher genetic distances between populations and between regions in the large-fruited species (Endiandra globosa), but higher overall diversity within the small-fruited species (Endiandra discolor). Floristic comparisons among plots confirmed lower numbers of large-fruited species in areas where more extreme rainforest contraction occurred, and recolonization by small-fruited species readily dispersed by the available fauna. Species' distribution patterns showed that larger-fruited species had smaller geographical ranges than smaller-fruited species and locations with stable refugia (and high endemism) aligned with concentrations of large fleshy-fruited taxa, making them a potentially valuable conservation-planning indicator.

Filters of floristic exchange: How traits and climate shape the rain forest invasion of Sahul from Sunda

“…We confirmed that despite broad‐scale functional commonalities with Sahul lineages, on average, Sunda species display characteristics that suggest more effective dispersal and more rapid growth (Figure ). The Sunda element of the flora has significantly more animal‐dispersed (zoochorous) lineages than the Sahul element, with the majority (81.95%) of Sunda species having small fruits that allow for easier and less specialized dispersal across water barriers (Crayn et al., ; Rossetto, Kooyman, et al., ) and the vegetation mosaics (e.g. dryland to wetland; sclerophyll to rain forest) characteristic of Australian landscapes (Wilson, Irvine, & Walsh, ).…”

“…For a comparative analysis of functional traits, we investigated if there were any characteristics common to Australian woody species with Sunda ancestry, and any differences between species with Sunda versus Sahul ancestry. We used continuous trait‐measures for leaf size (surface area), fruit size, wood density and maximum height at maturity, as well as categorical data from dispersal (mode) and persistence (resprouting) traits, all previously used in Australian rain forest studies (Kooyman et al., , , ; Rossetto & Kooyman, ; Rossetto et al., ; Rossetto, McPherson, et al., ; Rossetto, Kooyman, et al., ). Both the continuous and categorical traits were taken from published floras and other sources for all species (references listed in Appendix S2).…”

“…Fleshy fruits were then further partitioned into size classes (≤30 mm, and >30 mm in width) consistent with Rossetto, Kooyman, et al. (). Resprouting was the trait selected to describe a species’ ability to self‐replace (representing in situ persistence of individuals) and survive disturbance (Rossetto & Kooyman, ).…”

“…In combination, these same factors shape community assembly (Kooyman, Rossetto, Allen, & Cornwell, ; Kooyman, Rossetto, Cornwell, & Westoby, ; Kooyman, Rossetto, Sauquet, & Laffan, ). In light of those factors, and in relation to traits that enhance migration, we expected Sunda species to have larger leaves (reflecting tropical origins, Wright et al., ), lighter wood and shorter stature (reflecting faster growth; Moles et al., ), and smaller seeds particularly in fleshy, palatable fruits (enabling wider dispersal) (Rossetto, Crayn, Ford, Mellick, & Sommerville, ; Rossetto, Kooyman, Sherwin, & Jones, ; Rossetto, Kooyman, Yap, & Laffan, ). Here, we investigate relative dispersal potential, as well as differences in growth characteristics such as wood density, maximum height and leaf area that are associated with growth rates and relative competitiveness in different environments (Kunstler et al., ).…”

Saving rainforests in the South Pacific: challenges in ex situ conservation

“…Loss of dispersal agents, or large distances between fragments, can limit opportunities for regeneration, particularly for larger-seeded species (Meehan et al 2002;McConkey and Drake 2006;Rossetto et al 2015;Goosem et al 2016). Regeneration can also be limited by the activities of pest or agricultural animals.…”