Responses of seed size, ant worker size, and seed removal rate to elevation in Mediterranean grasslands

Vertebrate seed dispersers could impact the evolution of seed size or alter the pattern of seedling recruitment if they responded differently to seeds of varying size (Jordano 1995). For example, models of seed caching by birds and mammals predict that seeds of higher nutritive value should be placed farther from parent trees and in lower densities than lower quality seeds (Clarkson et al. 1986, Stapanian & Smith 1978, Tamura et al. 1999). Comparisons of seed removal rates among tropical tree species in South-East Asia (Blate et al. 1998) and Australia (Osunkoya 1994) failed to show a relationship between seed size and removal rate, although the probability that a seed was scatterhoarded by agoutis (Dasyprocta punctata) in a neotropical rain forest increased with interspecific seed size (Forget et al. 1998).

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Effects of microhabitat on rodent-mediated seed removal of endangered Kmeria septentrionalis in the karst habitat

PeerJ ◽

10.7717/peerj.10378 ◽

2020 ◽

Vol 8 ◽

pp. e10378

Author(s):

Guohai Wang ◽

Yang Pan ◽

Guole Qin ◽

Weining Tan ◽

Changhu Lu

Keyword(s):

Predation Risk ◽

Rattus Norvegicus ◽

Removal Rate ◽

Soil Surface ◽

Predation Rate ◽

Seed Removal ◽

Seed Type ◽

Stone Surface ◽

Broad Variety ◽

High Removal Rate

Seed removal behaviors of rodents are largely influenced by microhabitat. Although the karst ecosystem is composed of a broad variety of microhabitats, we have no information on how they affect such behaviors. We investigated rodents’ seed removal behaviors in four karst microhabitats (stone cavern, stone groove, stone surface, and soil surface) using three types of Kmeria septentrionalis seeds: fresh, black (intact seeds with black aril that dehydrates and darkens), and exposed (clean seeds without the aril). We show that Rattus norvegicus, Leopoldamys edwardsi and Rattus flavipectus were the predominant seed predators. Even though all seed types experienced a high removal rate in all four microhabitats, but rodents preferentially removed seeds from the three stone microhabitats (stone caves: 69.71 ± 2.74%; stone surface: 60.53 ± 2.90%; stone groove: 56.94 ± 2.91%) compared to the soil surface (53.90 ± 2.92%). Seeds that had been altered by being exposed to the environment were more attractive to rodents than fresh seeds (76.25 ± 2.20% versus 36.18 ± 2.29%). The seed removal behavior of rodents was significantly affected by the microhabitat and seed type. Finally, seeds that had fallen on the soil surface microhabitat incurred a lower predation risk than seeds fallen on other microhabitats, which increased their probability to germinate. Our results indicate that the lower predation rate of seeds from the endangered K. septentrionalis dropped on the soil surface increases trees’ likelihood of survival.

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Seed Removal Rates in Forest Remnants Respond to Forest Loss at the Landscape Scale

Forests ◽

10.3390/f11111144 ◽

2020 ◽

Vol 11 (11) ◽

pp. 1144

Author(s):

Alain Hambuckers ◽

Franck Trolliet ◽

Astrid Simon ◽

Eliana Cazetta ◽

Larissa Rocha-Santos

Keyword(s):

Forest Cover ◽

Removal Rate ◽

Supply And Demand ◽

Landscape Scale ◽

Fast Method ◽

Seed Removal ◽

Removal Rates ◽

Forest Remnants ◽

Forested Landscapes ◽

Plant Animal Interactions

Seed removal is a key component of seed dispersal and may be influenced by both landscape-scale and local attributes, and it has been used as an indicator of the intensity of interactions between ecosystem components. We examined how the seed removal rates, which integrate the activity of seed dispersers and seed predators, vary with landscape-scale forest cover. We collected data under 34 trees belonging to two zoochoric species (Helicostylis tomentosa (Poepp. and Endl.) J. F. Macbr. and Inga vera Willd.) in 17 remnants in the Brazilian Atlantic forest, with different percentages of forest cover. The seed removal rate was estimated using a fast method based on the abundance of intact fruits and fruit scraps on the ground. The amount of forest cover affected the rate of seed removal in a humpbacked shape, with a maximum seed removal rate at intermediate forest cover. Seed removal rates must be related to the amount of food resources offered and diversity of dispersers and predators in the region. In landscapes with intermediate forest amount, there is a better balance between supply and demand for fruits, leading to a higher seed removal rate than more deforested or forested landscape. Our results also show that local factors, such as crop size and canopy surface, together with forest cover amount, are also important to the removal rate, depending on the species. In addition, our results showed that plant–animal interactions are occurring in all fragments, but the health status of these forests is similar to disturbed forests, even in sites immersed in forested landscapes.

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The effect of forest successional stage on seed removal of tropical rain forest tree species

Journal of Tropical Ecology ◽

10.1017/s0266467402002171 ◽

2002 ◽

Vol 18 (2) ◽

pp. 261-274 ◽

Cited By ~ 32

Author(s):

Marielos Peña-Claros ◽

Henneleen De Boo

Keyword(s):

Tree Species ◽

Removal Rate ◽

Forest Tree ◽

Primary Forest ◽

Secondary Forests ◽

Seed Removal ◽

Successional Stage ◽

Successional Stages ◽

Agricultural Areas ◽

Number Of Seeds

Seed removal was evaluated at the macro- and micro-habitat level in areas differing in successional stage in the Bolivian Amazon. The successional stages consisted of secondary forests of 2, 10 and 20 years old and primary forest. Seeds of nine tree species were artificially dispersed and the number of seeds removed was evaluated over 7 weeks. Several stand characteristics were measured at the sites where seeds were dispersed. Seed removal at the end of the experiment varied from 50 to 100% depending on the species, and from 74 to 90% depending on successional stage. In general, the removal rate decreased with an increase in age of successional stage. The seed removal rate was related to liana density and not to litter thickness. Different microhabitat characteristics explained the seed removal rate of four species but microhabitat characteristics did not explain the decrease in seed removal rate with an increase in forest age. The results support the idea that post-dispersal seed removal reduces the number of seeds available for germination, consequently playing an important role in the regeneration of abandoned agricultural areas.

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Remoción de Semillas en Hábitats Transformados: Pogonomyrmex barbatus (Hymenoptera: Formicidae) y Cinco Especies de Cactáceas del Centro de México

Sociobiology ◽

10.13102/sociobiology.v59i1.666 ◽

2014 ◽

Vol 59 (1) ◽

pp. 49

Author(s):

Leticia Ríos-Casanova ◽

Héctor Godínez-Álvarez ◽

Gabriala Martínez Morales

Keyword(s):

Human Activities ◽

Removal Rate ◽

Seed Removal ◽

Foraging Activity ◽

Harvester Ants ◽

Pogonomyrmex Barbatus ◽

Intermediate Transformation ◽

Crop Field ◽

A Site ◽

Harsh Conditions

One of the main consequences of human activities in semiarid zones is the transformation of habitats. In this work we studied the effect of this transformation on seed removal of five cacti species by the harvester ant Pogonomyrmex barbatus in the Tehuacán-Cuicatlán valley, a semiarid zone in central Mexico. Seed removal was quantified at three sites which have been under the effect of human activities: an abandoned crop field (CCA), a site with evidence of current human activities (TAH), and a site inside a botanic garden ( JB). We hypothesized that sites which have been under intense human activities would have low rates of seed removal because they offer harsh conditions for harvester ants, reducing their foraging activity. Results showed that vegetation and surface soil characteristics of the sites studied are affecting the rates of seed removal of the five cacti species studied. The lowest seed removal rate was found at CCA, the most transformed site. In contrast with our hypothesis the highest seed removal was found at TAH, the site which represents the intermediate transformation condition, because this site still conserves some characteristics which permit intense foraging activity by harvester ants. We also found that the seed removal rate varied among the different cacti species studied. Seed of E. chiotilla had the highest removal rate, whereas O. decumbens had the lowest. Differences in seed removal rate could be associated with the high heterogeneity found in sites with intermediate levels of transformation. Another factor that must be considered is the external morphology of seeds since smaller seeds presented highest removal rates.

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Seed type, habitat and time of day influence post-dispersal seed removal in temperate ecosystems

PeerJ ◽

10.7717/peerj.8769 ◽

2020 ◽

Vol 8 ◽

pp. e8769

Author(s):

Katja Wehner ◽

Lea Schäfer ◽

Nico Blüthgen ◽

Karsten Mody

Keyword(s):

Plant Species ◽

Removal Rate ◽

Experimental Studies ◽

Time Of Day ◽

Seed Removal ◽

Chelidonium Majus ◽

Natural Form ◽

Seed Dispersion ◽

Removal Experiments ◽

The Impact

Seed survival is of great importance for the performance of plant species and it is strongly affected by post-dispersal seed removal by either different animals such as granivorous species and secondary dispersers or abiotic conditions such as wind or water. The success of post-dispersal seed removal depends on seed specific traits including seed size, the presence of coats or elaiosomes, the mode of seed dispersion, and on the habitat in which seeds happen to arrive. In the present study we asked how seed traits (dehulled vs. intact; size; dispersal mode), habitat (forest vs. grassland), and time of day (night vs. day) influence post-dispersal seed removal of the four plant species Chelidonium majus, Lotus corniculatus, Tragopogon pratensis and Helianthus annuus. Seed removal experiments were performed in three regions in Hesse, Germany. The results showed different, inconsistent influences of time of day, depending on habitat and region, but consistent variation across seed types. C. majus and dehulled H. annuus seeds had the fastest removal rates. The impact of the habitat on post-dispersal seed removal was very low, only intact H. annuus seeds were removed at significantly higher rates in grasslands than in forests. Our study demonstrates consistent differences across seed types across different habitats and time: smaller seeds and those dispersed by animals had a faster removal rate. It further highlights that experimental studies need to consider seeds in their natural form to be most realistic.

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Post-dispersal seed predation and seed bank persistence

Seed Science Research ◽

10.1017/s0960258500004487 ◽

1998 ◽

Vol 8 (4) ◽

pp. 513-519 ◽

Cited By ~ 72

Author(s):

P. E. Hulme

Keyword(s):

Seed Size ◽

Seed Bank ◽

Seed Predation ◽

Negative Relationship ◽

Seed Mass ◽

Seed Banks ◽

Seed Removal ◽

Seed Predators ◽

Grassland Plants ◽

Buried Seeds

AbstractThis study examines whether post-dispersal seed predators could be an important selective force in determining the seed bank strategies of grassland plants. It tests the hypothesis that species with persistent seed banks should sustain proportionally less predation of buried seeds than species which have transient seed banks and that this should be true irrespective of seed size. Results are drawn from a field experiment examining the relative susceptibility of surface versus buried seeds for 19 herbaceous taxa exhibiting different degrees of seed bank persistence. The data were consistent with the hypothesis that seed predators (rodents) influence the seed bank characteristics of seeds. Rodents removed proportionally more large seeds than small seeds and removed a smaller proportion of seeds with persistent rather than transient seed banks, independently of seed size. On average, burial reduced seed removal by almost 50%. The decrease in rates of seed removal following burial was marked for seeds with persistent seed banks but negligible for seeds with transient seed banks. Herbaceous plants with relatively large seeds (seed mass > 1 mg) that form persistent seed banks were either completely avoided or only consumed in small quantities by rodents. In contrast, large-seeded species with transient seed banks suffer high rates of seed predation. Models of life-history evolution predict trade-offs between seed dormancy and seed mass since dormancy and seed size are correlated traits that both reduce risk in variable environments and thus will show patterns of negative covariation. This paper presents an alternative explanation for this trade-off based on experimental evidence of a negative relationship between seed bank persistence and predation risk.

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Seed removal in two coexisting oak species: ecological consequences of seed size, plant cover and seed-drop timing

Oikos ◽

10.1111/j.0030-1299.2008.16370.x ◽

2008 ◽

Vol 117 (9) ◽

pp. 1386-1396 ◽

Cited By ~ 44

Author(s):

Ignacio M. Pérez-Ramos ◽

Itziar R. Urbieta ◽

Teodoro Marañón ◽

M. A. Zavala ◽

Richard K. Kobe

Keyword(s):

Seed Size ◽

Plant Cover ◽

Seed Removal ◽

Ecological Consequences

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Invasive acacias experience higher ant seed removal rates at the invasion edges

Web Ecology ◽

10.5194/we-12-33-2012 ◽

2012 ◽

Vol 12 (1) ◽

pp. 33-37 ◽

Cited By ~ 9

Author(s):

D. Montesinos ◽

S. Castro ◽

S. Rodríguez-Echeverría

Keyword(s):

Removal Rate ◽

European Population ◽

High Density ◽

Low Density ◽

Seed Removal ◽

Native Range ◽

Ant Communities ◽

Acacia Dealbata ◽

Introduced Plants

Abstract. Seed dispersal is a key process for the invasion of new areas by exotic species. Introduced plants often take advantage of native generalist dispersers. Australian acacias are primarily dispersed by ants in their native range and produce seeds bearing a protein and lipid rich reward for ant mutualists (elaiosome). Nevertheless, the role of myrmecochory in the expansion of Australian acacias in European invaded areas is still not clear. We selected one European population of Acacia dealbata and another of A. longifolia and offered elaiosome-bearing and elaiosome-removed seeds to local ant communities. For each species, seeds were offered both in high-density acacia stands and in low-density invasion edges. For both acacia species, seed removal was significantly higher at the low-density edges. For A. longifolia, manual elimination of elaiosomes reduced the chance of seed removal by 80% in the low-density edges, whereas it made no difference on the high-density stands. For A. dealbata, the absence of elaiosome reduced seed removal rate by 52%, independently of the acacia density. Our data suggests that invasive acacias have found effective ant seed dispersers in Europe and that the importance of such dispersers is higher at the invasion edges.

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Testing seed-size predictions in Mediterranean annual grasslands

Seed Science Research ◽

10.1017/s0960258510000176 ◽

2010 ◽

Vol 20 (3) ◽

pp. 179-188 ◽

Cited By ~ 8

Author(s):

Francisco M. Azcárate ◽

Pablo Manzano ◽

Begoña Peco

Keyword(s):

Seed Size ◽

Seed Predation ◽

Seed Mass ◽

Grazing Pressure ◽

Community Level ◽

Mean Annual Precipitation ◽

Mean Annual Temperature ◽

Summer Drought ◽

Mediterranean Grasslands ◽

Species Frequencies

AbstractOn the basis of previous research, we predict that Mediterranean grasslands should show larger-seeded annuals in: (1) more-arid grasslands; (2) more-fertile soils; (3) less-grazed grasslands; and (4) grasslands with lower intensities of seed predation by ants. To test these predictions, we set 29 sampling units of 50 m × 50 m in a 1000 km2 grassland area in Central Spain, and characterized them according to the former factors. We then recorded annual vegetation using ten quadrats of 20 cm × 20 cm in each sampling unit. Seed size at the community level was described using six variables: (1) mean seed mass; (2) standard deviation of seed mass; (3) weighted mean seed mass (by species frequencies); (4) proportion of small-seeded annuals; (5) proportion of medium-seeded annuals; and (6) proportion of large-seeded annuals. Most climate variables (mean annual temperature, length of the summer drought, water balance and mean annual precipitation) correlated with seed-size descriptors, showing that large-seeded annuals increase in warmer and more-arid communities. Mean seed size was modelled as a function of mean annual temperature and grazing pressure. According to this model, warmer and less-grazed communities tend to show a smaller mean seed size. These results confirm the importance of seed-size descriptors at the community level in Mediterranean grasslands, and the role of climate and grazing as major drivers in these communities. Conversely, hypotheses about soil fertility and seed predation by ants were not supported by our results.

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