Low availability of functional seed trait data from the tropics could negatively affect global macroecological studies, predictive models and plant conservation

Abstract

Background Plant seeds have many traits that influence ecological functions, ex situ conservation, restoration success and their sustainable use. Several seed traits are already known to vary significantly between tropical and temperate regions. Here we present three additional traits for which existing data indicate differences between geographical zones. We discuss evidence for geographical bias in availability of data for these traits, as well as negative consequences of this bias. Scope We reviewed the literature on seed desiccation sensitivity studies that compare predictive models to experimental data and show how a lack of data on populations and species from tropical regions could reduce the predictive power of global models. In addition, we compiled existing data on relative embryo size and post-dispersal embryo growth and found that relative embryo size was significantly larger, and embryo growth limited, in tropical species. The available data showed strong biases towards non-tropical species and certain families, indicating that these need to be corrected to perform truly global analyses. Furthermore, we argue that the low number of seed germination studies on tropical high-mountain species makes it difficult to compare across geographical regions and predict the effects of climate change in these highly specialized tropical ecosystems. In particular, we show that seed traits of geographically restricted páramo species are studied less than those more widely distributed, with most publications unavailable in English or in the peer-reviewed literature. Conclusions The low availability of functional seed trait data from populations and species in the tropics can have negative consequences for macroecological studies, predictive models and their application in plant conservation. We propose that global analyses of seed traits with evidence for geographical variation prioritise generation of new data from tropical regions as well as multi-lingual searches of both grey- and peer-reviewed literature in order to fill geographical and taxonomical gaps.

Global seed dormancy patterns are driven by macroclimate but not fire regime

“…Thus, more work is needed to study and measure seed traits, including dormancy, in the world's flora, especially in the understudied regions, such as the tropics and the Arctic (e.g. Visscher et al ., 2022).…”

SeedArc, a global archive of primary seed germination data

“…Despite these advances, current efforts are biased to specific floras or habitats of mid-latitude temperate biomes, with the major exception of Brazil (Ord oñez-Parra et al, 2023). Large amounts of the Earth's biodiversity hotspots remain unexplored by global-scale germination analyses, especially in tropical areas and continents such as Africa or parts of Asia (Hughes et al, 2021;Visscher et al, 2022).…”

In Site Soil Seed-Banks: Size, Composition and Persistence across Tropical Successional Stages

“…Many species of plants rely on regeneration from seed-banks (dormant seeds in the soil). Seed-banks are a major factor in the persistence of certain species [3,[7][8][9][10][11] and are particularly important in plant communities that are subjected to extreme environmental events or frequent disturbances such as: fire, seasonal drought, periodically flooded areas or agricultural fields [5,6,[10][11][12][13][14]. Furthermore, seed-banks play a vital role in the regeneration of tropical rainforests by maintaining the ecological and genetic diversity of populations and communities [14][15][16].…”

“…In general, the seeds of pioneer tree species tend to dominate soil seed-banks [10,13] and seeds from these species are the first to germinate following disturbances [2,10,13]. Factors that influence the abundance and species composition of soil seed-banks in tropical rainforests include the following: land use history, landscape composition and configuration, floristic composition of current and past standing vegetation, phenology, seed physiology and dispersal mode [5,6,8,10,12,13,17,18]. Contemporary land use in tropical areas has strong and long-term lasting effects on the density of seeds stored in the soil, in their germination capacity and on their persistence [5,6,[8][9][10]12,13,19].…”

“…Factors that influence the abundance and species composition of soil seed-banks in tropical rainforests include the following: land use history, landscape composition and configuration, floristic composition of current and past standing vegetation, phenology, seed physiology and dispersal mode [5,6,8,10,12,13,17,18]. Contemporary land use in tropical areas has strong and long-term lasting effects on the density of seeds stored in the soil, in their germination capacity and on their persistence [5,6,[8][9][10]12,13,19]. Persistent seed-banks are particularly important for species with life spans shorter than the average perturbation cycle (e.g., recurrent fires) in order to counter local extinction in areas that have been subjected to slash and burn agriculture and/or severe management for the growth of cattle pastures [5,[8][9][10]13].…”