Research Article
Interactions between ants and non-myrmecochorous diaspores in a West African montane landscape
- Jennifer A. Agaldo, Alexander V. Christianini, Hazel M. Chapman
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- Published online by Cambridge University Press:
- 28 April 2021, pp. 1-9
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Myrmecochory, the dispersal of seeds with lipid-rich appendages by ants, is a significant ant–plant interaction. Less well understood is the potential for ant dispersal of non-myrmecochorous seeds. Here we investigate ant–diaspore interactions in a West African montane habitat. We combine observation with depot experiments to determine ant species that move diaspores and distance moved across a forest-edge-grassland gradient. We recorded seed cleaning by ants using a bird/mammal dispersed Paullinia pinnata to determine whether seed cleaning improved plant fitness. We found that two out of a total of 17 ant species (Pheidole sp. 1 and Myrmicaria opaciventris) interacted with 10 species of non-myrmecochorous diaspores across nine plant families. Diaspores were from large canopy trees, understorey trees and vines. Both ant species interacted with small (≤0.24 g) and large (≥0.24 g) diaspores. Ants individually moved small diaspores up to 1.2 m and worked together to clean larger ones. Our experiments with P. pinnata showed that ants removed the pulp of 70% of fruit over 5 days. Cleaned seeds germinated significantly faster and produced seedlings with significantly longer shoot length and higher fresh weight than seedlings from intact seeds. Together our results suggest that ant dispersal may be less significant than seed cleaning in Afromontane forests. However, given the decline in vertebrate frugivores across Africa, a small dispersal advantage may become increasingly important to plant fitness.
Sex ratio and life history traits at reaching sexual maturity in the dioecious shrub Fuchsia parviflora: field and common garden experiments
- Jessica S. Ambriz, Clementina González, Eduardo Cuevas
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- Published online by Cambridge University Press:
- 08 April 2021, pp. 10-15
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Fuchsia parviflora is a dioecious shrub that depends on biotic pollination for reproduction. Previous studies suggest that the male plants produce more flowers, and male-biased sex ratios have been found in some natural populations. To assess whether the biased sex ratios found between genders in natural populations are present at the point at which plants reach sexual maturity, and to identify possible trade-offs between growth and reproduction, we performed a common garden experiment. Finally, to complement the information of the common garden experiment, we estimated the reproductive biomass allocation between genders in one natural population. Sex ratios at reaching sexual maturity in F. parviflora did not differ from 0.5, except in one population, which was the smallest seedling population. We found no differences between genders in terms of the probability of germination or flowering. When flowering began, female plants were taller than males and the tallest plants of both genders required more time to reach sexual maturity. Males produced significantly more flowers than females, and the number of flowers increased with plant height in both genders. Finally, in the natural population studied, the investment in reproductive biomass was seven-fold greater in female plants than in male plants. Our results showed no evidence of possible trade-offs between growth and reproduction. Despite the fact that female plants invest more in reproductive biomass, they were taller than the males after flowering, possibly at the expense of herbivory defence.
A half-day flowering pattern helps plants sharing pollinators in an oceanic island community
- Xiangping Wang, Tong Zeng, Mingsong Wu, Dianxiang Zhang
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- Published online by Cambridge University Press:
- 08 April 2021, pp. 16-25
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The temporal pattern of flower opening and closure is a feature of the biology of many plant species, particularly those inhabiting oceanic islands where flowering generally lasts for only a few hours per day. Additionally, flower visitors often seek different floral sources on a timely basis, thus the relative timing of interactions is central to their status in pollination competition, or in the facilitation of pollination among co-flowering plants sharing pollinators. However, few studies have examined the impacts of daily temporal variation in flowering patterns on the pollinator network and competition on a community scale. In order to examine whether the daily pattern of flower opening and closure can impose temporal dynamics on interspecific interactions within a single day, plant–pollinator interaction networks (AM subweb and PM subweb) were quantified, and the relevant interactions between the two subwebs were compared using the Bray–Curtis dissimilarity of visitation frequencies in an oceanic island community (Paracel Islands, South China Sea). The role of species within networks and its variation between two subwebs were assessed by calculating the species-level specialization and species strength of each plant and pollinator species. The quantitative plant–pollinator interaction dissimilarity between morning and afternoon subsets was 0.69, and this value dropped to 0.58 when considering plant species flowering throughout the day. In our study, this dissimilarity between the two subwebs might be explained by the morning peak activity rather than a preference for morning flowers. No significant differences were detected in the species-level specialization and species strength of plants flowering all day from morning to afternoon at the community level. The flower visitation rates of native honeybee Apis cerana were not significantly different between morning and afternoon for most of the whole-day flowering plants. However, plant species only flowering either in the morning or the afternoon differed in the rate of visitation by A. cerana. The analyses of variation in the visitation rates of pollinators shared by plants within a single day in the studied community suggest that daily structuring at a community level and half-day staggered flowering during the morning or afternoon might reduce competitive interactions in oceanic insular habitats.
Tropical fruit production depends on wild insect communities: bees and lychees in Thailand
- Khwankhao Sinhaseni, Carla P. Catterall
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- Published online by Cambridge University Press:
- 21 May 2021, pp. 26-34
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The importance of wild insects as pollinators of tropical tree crops has rarely been tested. Across 18 small-scale lychee orchards in northern Thailand, we evaluated the roles of different wild insects as pollinators and predators of pests in fruit production. Quantitative assessments showed that bees (Family Apidae) were strongly dominant (83%) among insect flower visitors, comprising four species in tribes Apini and four in Meliponini. Experimental manipulations of inflorescences showed that fruit production in these orchards was: (1) dependent on flower visits by wild insects because enclosure of inflorescences in mesh bags decreased fruit set (to one-fifth) and (2) not greatly limited by pollinator deficiencies, because hand pollination of unbagged flowers did not enhance fruit set. Pollination success, as indicated by the proportion of unmanipulated flowers setting fruit, correlated positively across orchards with the abundance of large-bodied Apidae (>7 mm; most were Apis species) and of Apini, and negatively with abundance of small-bodied Apidae and of all Meliponini, despite the latter being the commonest flower visitors. We conclude that larger-bodied bees are most likely to travel sufficiently far to import genetically diverse pollen, in this landscape-scale mosaic where non-orchard habitats (both agriculture and treed patches) were sufficient to sustain wild pollinators.
Extensive clonal propagation and resprouting drive the regeneration of a Brazilian dry forest
- Renato Soares Vanderlei, Maria Fabíola Barros, Arthur Domingos-Melo, Gilberto Dias Alves, Ana Beatriz Silva, Marcelo Tabarelli
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- Published online by Cambridge University Press:
- 10 May 2021, pp. 35-42
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Woody plant resprouting has received considerable attention in the last two decades as human disturbances continue to encroach on terrestrial ecosystems globally. We examined the regeneration mechanisms of a Caatinga dry forest in the context of slash-and-burn agriculture and resprouting ability of the local flora. We excavated two old fields (from 32) experiencing early forest regeneration dominated by the tree Pityrocarpa moniliformis (Fabaceae) to map clonal propagation and, in parallel, submitted 260 seedlings from 13 woody plant species to experimental clipping. What seemed to be ‘seedlings’ popping up around P. moniliformis stumps and remaining adults actually were condensed sets of root suckers connected via complex networks of long, ramified shallow horizontal roots without taproots. We mapped respectively 39 and 783 connected root suckers, which summed 96 m and 910 m in root length. Regarding the seedlings, 33% resprouted across nine species with resprouting rates varying between 5–100%. Seedling height before clipping positively influenced resprouting vigour. Our preliminary results suggest that the Caatinga dry forest supports a relatively high proportion of resprouting species, some of them able to clonally propagate and playing an ecosystem-level role by responding to early forest regeneration and high abundance/biomass across both regenerating and old-growth forests.
Selective logging does not alter termite response to soil gradients in Amazonia
- Renato Almeida de Azevedo, Quézia Cristina Lima Santos, Isadora Essig Fluck, Domingos J. Rodrigues, Leandro D. Battirola, Cristian de Sales Dambros
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- Published online by Cambridge University Press:
- 06 May 2021, pp. 43-49
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Selective logging has been widely employed as a management practice in tropical forests due to its reduced impact on biodiversity. However, by altering microclimatic conditions, logging could affect soil fauna responsible for nutrient cycling and the long-term dynamic of the forest. We investigated how selective logging affected termite species richness, composition, and the distribution of species in trophic groups, as well as the natural response of termites to gradients of soil conditions. Termites and edaphic variables were sampled in 32 permanent plots in southern Amazonia. Plots were subject to selective logging for 10–31 years before termite sampling. Time post-management was associated with changes in termite species composition, and wood-feeding termites were more abundant in recently logged areas. Nevertheless, most of the variation in termite species richness and composition can be attributed to the natural variation in soil clay content. Moreover, soil-dweller species, a vulnerable group strongly linked to soil decomposition, were present in all plots. These results suggest that the impact of selective logging on termite communities might be milder compared with other types of disturbance. It is likely that the decomposition process performed by termites, and consequently long-term ecosystem functioning, is preserved under selective logging.