Environment‐dependent influence of fruit size upon the distribution of the Malesian archipelagic flora

Abstract

Societal Impact StatementWe found evidence that larger fruited plant species are more likely to be found in aseasonal wet areas of Malesia. These areas are likely to be impacted by increasing human encroachment, which threatens both large‐fruited species and the large fauna that are most likely responsible for their dispersal. This synergistic threat could drive the loss of fruit‐crop relatives that potentially have key traits for resilient fruit crops of the future.Summary It is unclear how fruit size determines distributions of megadiverse tropical flora. Energetic constraints of ecosystems suggest plant species with larger fruit should be found in the higher productivity, aseasonal wet tropics. However, the probability of seed dispersal over large scales should be increased by fruits being smaller, due to being available to a greater number of dispersal agents. We use a Bayesian phylogenetic model of species occurrence for >3400 species in Malesia to test how fruit size and environment interact to determine species distributions across the archipelago. We show that larger fruited species are more likely to occur in aseasonal wet areas. We also found that smaller fruit size was associated with species occurrence in more mountainous areas. Fruit size interacts with environmental variables to shape plant distributions across the megadiverse Malesian islands. The evolutionary processes that influence the patterns we have observed require further examination.

From earthquakes to island area: multi‐scale effects upon local diversity

“…Likewise, the overall dispersal capacity of pools should shape how many species can disperse into and occur at sites (Xie et al 2023). Exploration of these potential patterns would require the collation and analysis of trait data linked to dispersal and adaptation to environment, such as height, leaf and fruit size (Wright et al 2017, Olson et al 2018, Brodie et al 2022, Trethowan et al 2022, 2023a).…”

“…The determinants of local species diversity are scale dependent (Willis and Whittaker 2002). Thus, local conditions interplay with large‐scale speciation and extinction that controls the number of species that can disperse and persist in a community (Ricklefs and Schluter 1993, Zobel 1997, Spasojevic et al 2018, Brodie et al 2022, Trethowan et al 2023a). In Indonesia and neighbouring countries, we find high plant species richness unmatched in other archipelagoes (Joyce et al 2020).…”

Biogeographic affiliation and centers of richness as predictors of elevational range‐size patterns for Malesian flora

“…edaphic conditions) or essential services (e.g. seed dispersal) provided by another species with limited geographic distributions (Russo et al 2007, Doughty et al 2023, Trethowan et al 2023a). A potential practical application of this finding is that ERR slopes may provide a broad‐scale quantitative metric of a taxonomic groups' potential response to climate change, which could be used to focus limited resources for more intensive conservation of particularly vulnerable species.…”

“…The oldest Gondwanan clades can occur on both western and eastern sides of Malesia (Hall 1998, Richardson et al 2012, Wilf and Kooyman 2023), as can taxa with long‐distance or stochastic seed dispersal abilities (Baker and Couvreur 2012, Webb and Ree 2012). Species with larger fruit or seeds tend to have limited distribution ranges if reliant on animal‐mediated dispersal, especially within aseasonal wet habitats relative to other biomes (Ashton and Lee 2022, Trethowan et al 2023a). Even if habitat conditions are suitable, taxa originating from outside a given region can have limited establishment success if communities are already saturated (Yap et al 2018).…”

Fruit in focus: A sampler platter of research

“…By linking measurements such as fruit length or width with species occurrence and environmental data, including temperature, precipitation, and soil composition, we can begin to unravel the role of the environment in shaping fruit size and distribution. Trethowan et al (2022) explore this relationship for over 3400 species in Malesia, determining that larger‐fruited species occur more frequently in wet areas, while more mountainous areas are associated with smaller fruit size. Knowledge about how environmental factors impact the number of fruits present can inform cultivation and production practices.…”