Dispersal is a key ecological process that influences plant community assembly. Therefore, understanding whether dispersal strategies are associated with climate is of utmost importance, particularly in areas greatly exposed to climate change. We examined alpine plant communities located in the mountain summits of the tropical Andes across a 4,000‐km latitudinal gradient. We investigated species dispersal strategies and tested their association with climatic conditions and their evolutionary history. We used dispersal‐related traits (dispersal mode and growth form) to characterize dispersal strategies for 486 species recorded on 49 mountain summits. Then we analysed the phylogenetic signal of traits and investigated the association between dispersal traits, phylogeny, climate and space using structural equation modelling and fourth‐corner analysis together with RLQ ordination. A median of 36% species in the communities was anemochorous (wind‐dispersed) and herbaceous. This dispersal strategy was followed by the barochory‐herb combination (herbaceous with unspecialized seeds, dispersed by gravity) with a median of 26.3% species in the communities. The latter strategy was common among species with distributions restricted to alpine environments. While trait states were phylogenetically conserved, they were significantly associated with a temperature gradient. Low minimum air temperatures, found at higher latitudes/elevations, were correlated with the prevalence of barochory and the herb growth form, traits that are common among Caryophyllales, Brassicaceae and Poaceae. Milder temperatures, found at lower latitudes/elevations, were associated with endozoochorous, shrub species mostly from the Ericaceae family. Anemochorous species were found all along the temperature gradient, possibly due to the success of anemochorous Compositae species in alpine regions. We also found that trait state dominance was more associated with the climatic conditions of the summit than with community phylogenetic structure. Although the evolutionary history of the tropical Andean flora has also shaped dispersal strategies, our results suggest that the environment had a more predominant role. Synthesis. We showed that dispersal‐related traits are strongly associated with a gradient of minimum air temperatures in the Andes. Global warming may weaken this key filter at tropical alpine summits, potentially altering community dispersal strategies in this region and thus, plant community structure and composition.

On the basis of a recent checklist of plant diversity in páramos, diaspores collected from herbaria were studied for adaptations to dispersal on animals and by water. This study shows that the páramo flora has a relatively high percentage of genera with morphological adaptations to epizoochorous and to hydrochorous diaspore dispersal. Genera with hooked and straight appendages are present throughout the páramo belt, while their number decreases in the higher páramo zones. About half of the hydrochorous genera and one‐third of the epizoochorous ones can be found throughout all páramo zones. The contribution of holarctic epizoochorous genera to the páramo flora seems to be greater than that of austral‐antarctic genera, whereas in hydrochorous genera it is the reverse.

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Summary The synthesis of homoserine has been studied in pea seedlings (Pisum sativum L. cv. Rondo) supplied with l‐[U‐14C]amino acids. The results demonstrate that both labelled aspartate and glutamate produce similarly large quantities of labelled homoserine. It is suggested that, in addition to asparagine and glutamine, homoserine also has an important function as a transport metabolite.

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Background and aims Understanding diaspore morphology and how much a species invests on dispersal appendages is key for improving our knowledge of dispersal in fragmented habitats. We investigate diaspore morphological traits in high-Andean Compositae, their main abiotic and biotic drivers and test whether they play a role in species distribution patterns across the naturally fragmented high-Andean grasslands. Methods We collected diaspore trait data for 125 Compositae species across 47 tropical high-Andean summits, focusing on achene length and pappus-to-achene length ratio, the latter as a proxy of dispersal investment. We analysed the role of abiotic (temperature, elevation and latitude) and biotic factors (phylogenetic signal and differences between tribes) on diaspore traits and whether they are related to distribution patterns across the Andes using phylogenomics, distribution modelling, and community ecology analyses. Key results Seventy-five percent of the studied species show small achenes (length < 3.3 mm) while 67% have high dispersal investment (pappus length at least double or more the achene length). Dispersal investment increases with elevation, possibly to compensate for lower air density, while achene length increased towards the equator where non-seasonal climate prevails. Diaspore traits showed significant phylogenetic signal, and higher dispersal investment is observed in Gnaphalieae, Astereae and Senecioneae which together represent 72% of our species. High Andean restricted species found across the tropical Andes have in average pappus four times longer than the achene length, a significantly higher dispersal investment than species present only in the northern or only in the central Andes. Conclusions Small achenes and high diaspore dispersal investment dominates among high-Andean Compositae, traits typical of mostly three tribes of African origin; but traits also correlate with the environmental gradients within the high-Andean grasslands. Our results also suggest that diaspore dispersal investment likely shapes species distribution patterns in naturally fragmented habitats.

SUMMARYGlutamate metabolism in intact cotyledons of pea seedlings {Pisum sativum L.) differs considerably from that in cotyledon slices. No decarboxylation of glutamate was found in intact cotyledons, whereas the decarboxylation in sliced cotyledons was so large that y-aminobutyric acid (yAbu) was by far the predominant metabolic product of glutamate. A number of mechanisms that could trigger glutamate decarboxylase activity are discussed.