Research devoted to investigating the relationship between elevation and seed size in alpine plants gives contradictory results. Some studies document a positive correlation between seed size and elevation, whereas in others a negative correlation is reported. We propose a novel approach to the problem by looking at the whole strategy of seed production, including seed number, and by focusing on a range of environmental variables. In the Tatra Mountains (southern Poland), we selected 73 sites at which seeds of six widely occurring mountain herbaceous species were collected. Each site was characterized by 13 parameters that included climatic and physicochemical soil variables. For each parameter, residuals from a linear regression against elevation were calculated and the residuals were used in a factor analysis. The obtained factors, together with elevation, were used as independent variables in a multiple regression analysis. Elevation affected seed size in four species: in two species the correlation was positive, and in two others it was negative. In three species seed number was related to elevation, and the correlation was negative in all cases. Our results indicate that elevation-dependence of seed production is specific to the species and reflects different resource allocation strategies. Diverse correlations of plant characteristics with elevation may also result from area-specific patterns, because different mountain ranges may exhibit different correlations between elevation and environmental factors. Only by attaining a reproductive allocation perspective and thorough assessment of environmental factors, a full understanding of elevational variation in seed size is possible.

No abstract

The regeneration of many climax species in tropical forest critically depends on adequate seed dispersal and seedling establishment. Here, we report the decreased abundance and increased spatial aggregation of younger trees of the Borneo ironwood (Eusideroxylon zwageri) in a protected forest in Sabah Malaysia. We observed a high level of seedling herbivory with strong density dependence, likely exacerbated by local aggregation and contributing to the progressively shrinking size distribution. We also note the largely undocumented selective herbivory by sambar deer on E. zwageri seedlings. This study highlights the combined impact of altered megafauna community on a tree population through interlinked ecological processes and the need for targeted conservation intervention for this iconic tropical tree species.

Assessing the heat tolerance (CTmax) of organisms is central to understand the impact of climate change on biodiversity. While both environment and evolutionary history affect CTmax, it remains unclear how these factors and their interplay influence ecological interactions, communities and ecosystems under climate change. We collected and reared caterpillars and parasitoids from canopy and ground layers in different seasons in a tropical rainforest. We tested the CTmax and Thermal Safety Margins (TSM) of these food webs with implications for how species interactions could shift under climate change. We identified strong influence of phylogeny in herbivore–parasitoid community heat tolerance. The TSM of all insects were narrower in the canopy and parasitoids had lower heat tolerance compared to their hosts. Our CTmax‐based simulation showed higher herbivore–parasitoid food web instability under climate change than previously assumed, highlighting the vulnerability of parasitoids and related herbivore control in tropical rainforests, particularly in the forest canopy.

No abstract