Plants show more flesh in the tropics: variation in fruit type along latitudinal and climatic gradients

Fruit type has a major impact on seed dispersal, seed predation and energy allocation, but our understanding of large-scale patterns in fruit type variation is weak. We used a dataset of 4008 Australian species to provide the first continental-scale tests of a series of hypotheses about the factors that might affect fruit type. We found a significant latitudinal gradient in the proportion of fleshy-fruited species, with the percentage of fleshy-fruited species rising from 19% at 43.75°S to 49% at 9.25°S. Species bearing fleshy fruits were more frequent on the coastal fringes of Australia, while species bearing non-fleshy fruits became more frequent toward the arid centre. Wet, warm and stable climates favoured fleshy-fruited species, with the two best predictors of the proportion of fleshy-fruited species being maximum precipitation over five days (R² = 0.40), and precipitation in the wettest month (R² = 0.25). These results remained consistent after accounting for phylogenetic correlation among species. A combined model including variables of precipitation, temperature, and climatic variation explained 67% of the variation in the proportion of fleshy-fruited species. Our results are consistent with the idea that plant reproductive strategies are more often tied to conditions during the parts of the year in which they grow than to conditions during the harsh parts of the year. Overall, our findings demonstrate strong relationships between plant reproductive traits and environmental gradients, and improve our understanding of the factors that shape large-scale patterns in plant ecological strategies.