Fate Of Seeds Research Articles

Effects of dung beetles (Scarabaeidae) on seeds dispersed by howler monkeys (Alouatta seniculus) in the French Guianan rain forest

The dispersal of seeds by howler monkeys (Alouatta seniculus) and the role of dung beetles in determining the fate of the dispersed seeds were studied at Nouragues Station, French Guiana, during three 2-mo periods (April–May, 1995–97). Howler monkeys were observed to disperse seeds of 47 plant species. Monkey dung attracted 57 species of dung beetles (Scarabaeidae), including tunnellers (maximum size 37 mm) and ball rollers (12.6 mm). The rate of seed burial was negatively correlated with seed size (10 plant species) and positively correlated with dung beetle size (six species of tunnellers). More than 80% of small seeds (< 5 mm) and 30% of large seeds (22 mm), were buried by the largest tunnellers. Dung beetles buried 13 to 23% of seeds ranging 8–13 mm in width. The maximum average depth of burial was 28 cm and varied according to the species of dung beetle. The rate of disappearance of large dung clumps varied during the day and was completed by nocturnal dung beetles. Seeds of Chrysophyllum lucentifolium (Sapotaceae) buried at 5 and 10 cm depths did not suffer predation, but showed low germination success compared to seeds left at the soil surface. Dung beetles affected the survival and distribution of a portion of the seeds dispersed by monkeys, and their relative importance in shaping seed fate depended on seed and beetle size.

Seed and seedling ecology of piñon and juniper species in the pygmy woodlands of western North America

Knowledge of the seed and seedling ecology of the pinon and juniper woodlands of western North America is essential for understanding both the northward migration and expansion of the woodlands during the Holocene (< 11,500 B.P.), and the accelerated expansion of the woodlands since settlement of the West by Anglo-Americans around 200 years ago. We follow the fates of seeds and seedlings of the different pinon and juniper species within the woodlands from seed development to seedling establishment, and discuss the implications of this information for the past and present expansion of the woodlands. While seed development requires about two and one-half years in pinons, it is species-dependent in junipers and can take one, two, or even three years. Substantial seed losses can occur during seed development due to developmental constraints, and before or after seed maturation as a result of insects, pathogens, or predatory animals. In pinon pines, the primary seed dispersers are scatterhoarding birds (corvids) and rodents that harvest seeds from the trees or after seed fall and cache them in the soil. In contrast, most junipers appear to be dispersed primarily by frugivorous birds and mammals that ingest the seeds and defecate them onto the soil surface. We have recently documented that scatter-hoarding rodents also disperse juniper seeds. Disperser effectiveness, or the contribution a disperser makes to the future reproduction of a plant population, may vary among species of pinons and especially junipers. Pinon seeds are short-lived and exhibit little dormancy, and they probably only germinate the spring following dispersal. Juniper seeds are long-lived and seed dispersal can occur over one or more years. Seed germination can be delayed for several years due to impermeable seed coats, embryo dormancy, or the presence of inhibitors. Seedling establishment of pinon pines is facilitated by nurse plants but, while junipers often establish beneath nurse plants, they are capable of establishing in open environments. In the southwestern United States, higher establishment of juniper occurs in open environments due to more favorable precipitation, and competition may be more important than facilitation in determining establishment. When considering the mechanisms involved in the past and present expansion of the woodlands, short-distance dispersal, local population growth, and long-distance dispersal are all important. Different classes of dispersers, some of which appear to have coevolved with the tree species, appear to be responsible for local (short-distance) vs. long-distance dispersal in pinons and junipers. Because ecotones form the interface between the woodlands and adjacent communities, they can provide valuable information on both the seed dispersal and seedling establishment processes responsible for tree expansion. Disturbance regimes and, recently, the effects of humans on those regimes have major effects on the expansion and contraction of the woodlands. Before Anglo-American settlement, fires occurred as frequently as every 50–100 years throughout much of the woodlands. During this century, fire frequencies have been reduced due to the indirect effects of livestock grazing and the direct effects of removing Native Americans from the ecosystem and implementing active fire-prevention programs. The result has been an increase in tree-dominated successional stages at the expense of grass-dominated stages. Various management techniques, including controlled burning and chaining, have been implemented to reduce tree dominance, but their effects depend largely on the life histories of the tree species and the disturbance characteristics. Several areas relating to the seed and seedling ecology of the pinon and juniper require additional research if we are to truly understand the dynamics of the woodlands.

Effects of Ant Species Composition on Seed Removal in Deciduous Forest in Eastern Europe

Ant species contribute differently to the removal of elaiosome-bearing seeds. Microhabitats on the deciduous forest floor differ in the composition of ant species; these differences may influence the dispersal of myrmecochorous plants. This study examined removal rates of Viola odorata seeds which were dispersed by foragers of four ant species Formica polyctena (FP), Lasius fuliginosus (LF), Myrmica rubra (MR). and Leptothorax nylanderi (LN). We observed (I) the visit rates of ants and removal rates of seeds at three microhabitats with different ant species composition: FP territory with MR and LN. LF territory with AIR and LN, AIR territory with LN; (2) the contribution of different ant species to the seed removal rates; (3) effects of microsite type on the duration of seed manipulation by ant workers; (4) number of seeds handled by workers of different ant species: (5) effects of learning and recruitment on seed removal rates in three ant species FP. LF, and MR. At each territory the main contribution to visit rates and to seed removal rates was made by the most dominant ant species. The duration of seed manipulation by AIR ants at both FP and LF territories was significantly shorter than that by FP and LF ants. Under the pressure of large LF and FP, the AIR workers left the seed depot twice as quickly as in the absence of other ant species. Thus, duration of seed manipulation by MR was significantly shorter at FP, and especially, at LF territories than at MR territory. In all territories the duration of seed manipulation by LN was significantly longer than by other ant species. Learning (MR) or recruitment (FP) took place during seed removal. There were no differences in the duration of seed manipulation between experienced and inexperienced ants of both LF and FP. Inexperienced individuals of MR manipulated seeds twice as long as experienced ones. Experienced ants removed seeds with higher frequency than inexperienced ones regardless of ant species. It is concluded that ant species composition strongly influences the removal rates of seeds and potentially the fate of seeds of a myrmecochore. FP territory, providing the fastest removal of the fruit content, is presumably the most advantageous for the myrmecochore.

Experimental demography of the rareGentianella germanica: seed bank formation and microsite effects on seedling establishment

The persistence of populations of short‐lived species requires regular reproduction and seedling establishment. A persistent seed bank can buffer populations against extinction in unfavourable years. We experimentally investigated seed fate inGentianella germanica, an endangered biennial species characteristic for species‐rich nutrient‐poor calcareous grasslands in central Europe. We studied the effect of experimental gaps on seedling establishment from sown seeds and the fate of seeds buried in bags over two years. In December 1993 experiments were established at seven calcareous grassland sites in the Swiss Jura mountains. In spring 1994 seedlings emerged in all plots where seeds had been sown, including previously unoccupied patches. This suggests that limited dispersal within sites contributes to small population sizes. Significantly more seedlings emerged at sites with current populations of G.germanicathan at unoccupied sites (5.95% vs 3.40%). Because this difference was not explained by germinations from the natural seed bank it indicates differences in habitat quality. Clipping of the vegetation and disturbance of the soil reduced vegetation cover in the following spring and enhanced seedling emergence. In undisturbed plots 4.5% of seeds sown produced a seedling in spring 1994, whereas in plots with clipped vegetation 9.9% and in disturbed plots 12.7% produced seedlings (p&gt;0.01). This suggests that management measures which create gaps in the vegetation (e.g. grazing) could positively influence population size and persistence ofG. geymanica.On average, we recovered 7.55% viable seeds after one year of burial in bags, and 4.05% after two years, indicating thatG. geymanicahas a persistent seed bank. The demographic data indicate that the number of viable seeds in the seed bank exceeds the number of established plants in a population at least by a factor of 20. Restoration of extinct populations of the species from the seed bank may thus be possible if appropriate management measures are taken within a few years.

Interaction between ants and seeds of a nonmyrmecochorous neotropical tree, Cabralea canjerana (Meliaceae), in the Atlantic forest of southeast Brazil

On the forest floor of two Atlantic forest sites in southeast Brazil, we recorded 26 ant species (12 genera) interacting with the seeds of Cabralea canjerana (Meliaceae), a typical ornithochorous tree whose seeds are covered by a lipid-rich aril. The ants treat the arillate seeds in three different ways: (1) the large ponerine ants Pachycondyla striata and Odontomachus chelifer individually remove the seeds to their nests, (2) many species (Pheidole spp.) recruit workers to remove the aril on the spot, or (3) Solenopsis spp. recruit nestmates and cover the seeds with soil before removing the aril on the spot. The ants remove the aril exceptionally rapidly, and removal greatly facilitates seed germination. Seed predation by insects below fruiting trees is severe, and field experiments using vertebrate exclosures showed that rodents also prey heavily upon seeds found near parent trees. Ponerine ants actively remove seeds from this predation-prone zone. By removing bird-manipulated and naturally fallen seeds, ants can play a key role in the fate of medium-sized seeds like those of C. canjerana.

DISPERSAL PATTERNS AND SEED BANK DYNAMICS OF PIONEER TREES IN MOIST TROPICAL FOREST

Seed dispersal patterns and seed persistence in the soil should strongly influence the distribution of pioneer tree recruits in gaps. Nonetheless, seed distribution patterns for pioneers are poorly known, and processes controlling the fate of seeds in the soil have been little explored. We examined patterns of seed rain, seed abundance in the soil, and seed mortality of two common pioneer trees, Miconia argentea (Melastomataceae) and Cecropia insignis (Moraceae), on Barro Colorado Island, Panama. For each species, we selected four isolated, reproductive trees within a 50-ha forest dynamics plot. Seed rain and soil seed bank samples were collected, respectively, in mesh traps and from soil cores sampled along transects radiating away from the tree crowns. At below-crown sites, seed rain inputs far exceeded soil seed bank densities measured at the end of the fruiting season. For Miconia, the below-crown seed bank in the surface 3 cm of soil accounted for only 23% of seed rain, and for Cecropia, only 2%. However for Miconia, at distances >5 m from the crown seed bank densities exceeded the annual seed rain input. For both species log seed densities in the seed bank declined linearly with log distance from the crown and also decreased dramatically through the year. The annual loss rate of Miconia seeds was >90% below the crown and declined to 65% at 30 m from the crown. The annual loss rate for Cecropia was >90% at all distances. Seed losses in the seed bank could be largely attributed to mortality from pathogenic fungi. Fungicide treatment significantly increased seed survival in the soil for both species. For these two gap-dependent pioneer species, rapid seed-bank turnover rates and logarithmic declines in soil seed density with distance from adults suggested that both the spatial distribution and timing of gap formation may have influenced their chances of successful gap colonization. Recruitment from distant seed sources, or from seeds surviving in the soil after the death of the parent tree, may be relatively rare for these species.

Effect of seed passage through vertebrate frugivores' guts on germination: a review

Abstract The capacity of seeds to germinate after ingestion by frugivores is important for the population dynamics of some plant species and significant for the evolution of plant-frugivore interactions. In this paper the effects of different vertebrates on seed germination of nearly 200 plant species are reviewed, searching for patterns that predict the circumstances in which germination of seeds is enhanced, inhibited, or unaffected by the passage through the digestive tract of a seed disperser. It was found that seed dispersers commonly have an effect on the germinability of seeds, or on the rate of germination, or both, in about 50% of the plants they consume, although the diversity of animal species tested so far is still rather low (42 bird species, 28 non-flying mammals, 10–15 bats, 12 reptiles, 2 fishes). Enhancement of germination occurred about twice as often as inhibition. In spite of the morphological and physiological differences in their digestive tracts, the different animal groups tested have similar effects on seed germination, although non-flying mammals tend to influence germination slightly more often than the other groups. Data on fishes are still too scarce for any generalization. Seed retention time in the dispersers' digestive tract is one factor affecting germination, and helps to explain the variation in seed responses observed among plant species, and even within a species. However other factors are also important; for example, the type of food ingested along with the fruits may affect germination through its influence on chemical or mechanical abrasion of the seed coat. Seed traits such as coat structure or thickness may themselves be responsible for some of the variation in seed retention times. Seeds of different sizes, which usually have different transit times through frugivores, and seeds of either fleshy or dry fruits, show often similar germination response to gut passage. Seeds of different plants species differ strongly in their germination response after ingestion, even by the same frugivore species. Congeneric plants often show little consistency in their response. Even within a species variation is found which can be related to factors such as the environmental conditions under which germination takes place, seed morphology, seed age, and the season when the seeds are produced. The effect of gut passage on germination differs between tropical and temperate zones. Seed germination of both shrubs and trees (data on herbaceous species are still scarce) in the temperate zone is more frequently enhanced than in the tropics. This result supports the hypothesis that enhanced germination may be more advantageous in unpredictable or less constant environments. Significant differences in frugivore-mediated germination are also found among different life forms. In both tropical and temperate zones, trees appear to be consistently more affected than shrubs or herbs. This might be due to an overall higher thickness of the seed coats, or to a higher frequency of seed-coat dormancy in tree species. The influence of frugivory upon the population dynamics of a species has to be evaluated relative to other factors that influence germination and seedling recruitment at a particular site. Whether seed ingestion by dispersers is really advantageous to a plant (as has commonly been assumed) can only be assessed if we also determine the fate of the ingested seeds under natural conditions, and compare it to the fate of seeds that have not been ingested.

Effect of Microhabitat on Seed Fate and Seedling Performance in Two Rodent- Dispersed Tree Species in Rain Forest in French Guiana

1 The establishment probabilities, short-term survival, growth rates and biomass allocation patterns of seedlings in two large-seeded tree species, Carapa procera (Meliaceae) and Vouacapoua americana (Caesalpiniaceae), were studied in contrasting microhabitats at Paracou, French Guiana. 2 Seeds (100 per habitat per species) were buried to simulate rodent caches into gap and understorey microhabitats (n = 20 of each) surrounding mature parent trees. The experiment was replicated in Carapa procera (in early March and May) to investigate the effect of temporal variation in seed dispersal on the establishment process. 3 Surviving seeds and sprouting seedlings were repeatedly censused during 2 years after establishment, and the causes of mortality determined. Growth and biomass parameters were calculated for surviving seedlings after 2.5 years. 4 A greater proportion of seeds and germinating seedlings were dug up but less seedlings suffered from damping-off in C. procera than in V. americana. For both species, short-term survival of seedlings was lower in the understorey where predation by mammals and damping-off occured more frequently than in gaps. 5 Damping off killed more Carapa procera seedlings when buried in March than in May, whereas mammal predation caused more deaths in May planted seeds. 6 Although survival and growth were enhanced in gaps for both species, seeds and seedlings were much more intolerant to the understorey microhabitat in Carapa procera (almost 100% mortality in shaded habitat) than in Vouacapoua americana. 7 Seedling biomass allocation was consistent with previous data for large-seeded species but differed markedly between the two study species.

Dynamics of the seedling shadow of a frugivore-dispersed tree species in French Guiana

In neotropical forests, a wide range of tree species depend on effective seed dispersal by primates for successful seedling establishment and recruitment (Howe 1986,Janzen 1970). In Guianan rainforests, for instance, a community of up to eight primates ranging from 0.4 to 13 kg (Emmons & Feer 1990) consume fruits and defecate seeds of at least 180 plant species belonging to more than 50 families (Guillotin et al. 1994, Julliot & Sabatier 1993, Mittermeier & van Roosmalen 1981, Simmen & Sabatier 1996, van Roosmalen 1985). Although there is an abundant literature on fruit consumption, ingestion, dispersal and predation of primate-dispersed tree species, almost nothing is known about the final fate of naturally-dispersed seeds throughout the seedling and juvenile stages (see Howe 1990, 1993; Howe et al. 1985). In this paper, the seedling shadow of a frugivore-dispersed tree species in French Guiana is illustrated and data on 4 y of seedling dynamics are presented. The species will be described by D. Sabatier elsewhere (pers. comm.) as a new taxon of Virola; the type voucher number is Daniel Sabatier 931, from tree B in this study, and is deposited at the herbarium collections of Cayenne, Paris, Utrecht, New York and Kew). This study is the first report to date on the consequences of seed dispersal by a neotropical rain forest monkey. This study was carried out at the Nouragues Biological Reserve, near to the Arataye River at the Saut Parare waterfall area (52?40'W, 4?02'N) (Dubost

Effect of seed predation on seed bank size and seedling recruitment of bush lupine (Lupinus arboreus).

Whether seed consumers affect plant establishment is an important unresolved question in plant population biology. Seed consumption is ubiquitous; at issue is whether seedling recruitment is limited by safe-sites or seeds. If most seeds inhabit sites unsuitable for germination, post-dispersal seed consumption primarily removes seeds that would otherwise never contribute to the population and granivory has minimal impacts on plant abundance. Alternatively, if most seeds ultimately germinate before they lose viability, there is greater potential for seed consumption to affect plant recruitment. Of the many studies on seed consumption, few ask how seed loss affects seedling recruitment for species with long-lived seed banks. We examined post-dispersal seed predation and seedling emergence in bush lupine (Lupinus arboreus), a woody leguminous shrub of coastal grasslands and dunes in California. We followed the fate of seeds in paired experimental seed plots that were either protected or exposed to rodent granivores in grassland and dune habitats. Significantly more seeds were removed by rodents in dunes than grasslands. In dunes, where rodent granivory was greatest (65% and 86% of seeds removed from plots by rodents in two successive years), there is a sparse seed bank (6.6 seeds m-2), and granivory significantly reduced seedling emergence (in the same two years, 18% and 19.4% fewer seedlings emerged from exposed versus protected plots), suggesting seed rather than safe-site limited seedling recruitment. In contrast, rodents removed an average of 6% and 56% of seeds from grassland plots during the same two years, and the grassland seed bank is 43-fold that of the dunes (288 seeds m-2). Even high seed consumption in the second year of the study only marginally influenced recruitment because seeds that escaped predation remained dormant. Burial of seeds in both habitats significantly reduced the percentage of seeds removed by rodents. Results suggest that granivores exert strong but habitat-dependent effects on lupine seed survival and seedling emergence.

Post-dispersal seed predation and the establishment of vertebrate dispersed plants in Mediterranean scrublands.

The post-dispersal fate of seeds and fruit (diaspores) of three vertebrate-dispersed trees, Crataegus monogyna, Prunus mahaleb and Taxus baccata, was studied in the Andalusian highlands, south-eastern Spain. Exclosures were used to quantify separately the impact of vertebrates and invertebrates on seed removal in relation to diaspore density and microhabitat. The three plant species showed marked differences in the percentage of diaspores removed, ranging from only 5% for C. monogyna to 87% for T. baccata. Although chaffinches (Fringilla coelebs) fed on diaspores, rodents (Apodemus sylvaticus) were the main vertebrate removers of seed and fruit. Two species of ant (Cataglyphis velox and Aphaenogaster iberica) were the only invertebrates observed to remove diaspores. However, the impact of ants was strongly seasonal and they only removed P. mahaleb fruit to any significant extent. While removal of seed by rodents was equivalent to predation, ants were responsible for secondary dispersal. However, their role was limited to infrequent, small-scale redistribution of fruit in the vicinity of parent trees. Rodents and ants differed in their use of different microhabitats. Rodents foraged mostly beneath trees and low shrubs and avoided open areas while the reverse was true of ants. Thus, patterns of post-dispersal seed removal will be contigent on the relative abundance and distribution of ants and rodents. Studies which neglect to quantify separately the impacts of these two guilds of seed removers may fail to elucidate the mechanisms underlying patterns of post-dispersal seed removal. The coincidence of both increased seed deposition by the main avian dispersers (Turdus spp.) and increased seed predation with increasing vegetation height suggested that selection pressures other than post-dispersal seed predation shape the spatial pattern of seed dispersal. Rather than providing a means of escaping post-dispersal seed predators, dispersal appears to direct seeds to microhabitats most suitable for seedling survival. Nevertheless, the reliance of most vertebrate-dispersed trees on regeneration by seed and the absence of persistent soil seed banks imply that post-dispersal seed predators may exert a strong influence on the demography of the plants whose seeds they consume. Even where microsites are limited, the coincidence of the most suitable microhabitats for seedling establishment with those where seed predation is highest provide a means by which selective seed predators can influence community composition.

Micro‐site influence on seed longevity and seedling emergence of a bunchgrass (Themeda triandra) in a semi‐arid savanna

The influence of micro‐site (shaded, exposed, buried) on the seed longevity and seedling emergence of Themeda triandra was tested using experimental seed banks. Deep shade considerably reduced soil surface temperature. Seeds did not persist in any micro‐site for longer than one year. The fate of most seeds in the first year was to germinate but most buried seeds died before emergence; <20% of seed decayed. Greatest seedling emergence occurred with seed on the surface, particularly if shaded. The temporal pattern of emergence depended on micro‐site, with implications for seedling risk. Limited seed longevity may render T. triandra, an obligate seed‐reproducing species, vulnerable to failure of seedling recruitment.

Seed viability of Afromontane tree species in forest soils

ABSTRACTThe fate of seeds of eight tree species was followed during 4 y of storage in the soil of an Afromontane forest at Gara Ades in the eastern highlands of Ethiopia. Seeds were enclosed in nylon mesh bags and buried at 5 cm soil depth. The bags were exhumed at intervals and the viability of the seeds was assessed by germination and cutting tests. Seeds of Bersama abyssinica and Ekebergia capensis germinated in the soil almost completely within a year after burial. The seeds of Juniperus procera, Olea europaea and Podocarpus falcatus also germinated to a substantial degree in the soil but with a distribution over several years, and some seeds of these species remained viable at the end of the 4-y period. Germination in the soil was very low in seeds of Acacia abyssinica and Croton macrostachyus throughout the whole burial period and the seeds kept their viability. In C. macrostachyus fresh seeds were highly dormant, but after 3 y or more in the soil they germinated readily in the laboratory suggesting an altered dormancy with time in the soil. Dormancy in seeds of A. abyssinica and Indigofera rothii was not altered throughout the study period as evidenced by marginal or no germination during incubation in the laboratory. The differential seed behaviour observed during storage in the soil can be an indicator of the regeneration strategy of the species studied. B. abyssinica, E. capensis, J. procera, O. europaea and P. falcatus form seedling banks on the forest floor and lack persistent soil seed reserves in contrast to A. abyssinica, C. macrostachyus and I. rothii which accumulate reserves of long-lived seeds in the soil. The generally high levels of dormancy and somewhat extended viability in the soil, even in several of the species producing seedlings in undisturbed forest, may have been selected for under a climate of seasonal drought and unreliable rainfall that characterizes this region.

Fates of Weed Seeds in Soil: A Seeded Core Method of Study

1. A method is described for the study of the fates of unprotected seeds in soil. Its key features include: (i) selection of seeds on the basis of anticipated high viability; (ii) placement of unprotected seeds in known positions in the soil; (iii) extraction of soil cores containing the seeds several times each year; (iv) elutriation of these cores and recovery of the seeds; (v) germination and viability testing of the recovered seeds. 2. Initial results for an experiment conducted with seeds of four weed species in an agricultural field in the midwestern USA are used to demonstrate the soundness of the method. 3. The strengths, weaknesses and assumptions of the method are discussed.

Frugivory and the fate of dispersed and non-dispersed seeds of six African tree species

ABSTRACTThe relationship between seedling recruitment (under and away from parent trees) and the behaviour of seed dispersers and predators, was explored in a three-year study in Kibale National Park, Uganda. On the basis of 1261 hours of observation, the foraging activity of the diurnal frugivores which fed on fruit from six tree species was quantified. The fate of dispersed and non-dispersed seeds and seedlings was examined experimentally. The findings suggest that a trade-off exists between factors that promote seedling growth in areas with high seedling density and factors that promote dispersal by frugivores. For example, dispersal ofMimusops bagshaweiincreases both seed and seedling survival; seeds placed away from adult conspecifics had a 8% lower probability of disappearing than seeds placed under adults and seedlings away from adults had a 30% greater probability of surviving than seedlings grown under adults. In contrast, forUvariopsis congensis, dispersed seeds had a 56% greater probability of disappearing than seeds directly under a parent tree, while the survival of dispersed and non-dispersed seedlings was similar. Non-dispersed seed and seedling disappearance were correlated with the percentage of the fruit crop removed from focal trees, suggesting that the ability to survive under an adult maybe related to other aspects of the tree's life history.

Germination and seedling growth of an endangered native broom,Chordospartium muritaiA.W.Purdie (Fabaceae), found in Marlborough, South Island, New Zealand

Abstract In the wild, adult Chordospartium muritai shrubs and trees up to 6 m tall are confined to a single population in the northern South Island. There are few juveniles and seedlings have only recently been recorded. Seed viability, germination requirements, fate of seeds in the soil seed bank, and seedling growth were investigated. Seeds required scarification, after which a high proportion germinated over a wide range of temperatures, but particularly between 20°C and 24°C. The few seeds that survived a year's burial were still viable, suggesting the effects of soil scarification. Seedling growth was very slow and 65% of seedlings that survived the first 2 years reached a height of only 12 cm. Site factors including past grazing, competition from herbs, and lack of suitable substrates, are considered largely responsible for the failure of C. muritai regeneration. The management implications of the results are discussed.

Seed production, predation and dispersal in the Mediterranean myrmecochore Euphorbia characias (Euphorbiaceae)

Seed production or a population of 193 reproductive individuals of Euphorbia characias from the north‐east Iberian peninsula was estimated at 155000 seeds per year. The dehiscence period lasts for four weeks. The timing of ballistic dispersal is uniformly distributed throughout the day. Seeds remain on the surface a mean time (±SE) of 52.3 ± 6.7 min. Several ant species take the seeds in varying proportions: Messor barbarus (0.225), a granivorous ant which eats the seeds; Aphaenogaster senilis (0.313), Pheidole pallidula (0.296) and Tapinoma nigerrimum (0.162) which take the seeds to their nests but do not eat them. Half a million ant foraging trips per day indicate a very strong short term influence of ants on fate of Euphorbia seeds. Ants as a group have a dual role of predation and dispersal of Euphorbia characias seeds. The characteristics of this Euphorbia (sclerophylly, diplochory, firmness of elaiosome, absence of subsidiary myrmecochorous features) better fit the syndrome described for Australian myrmecochores than the one proposed for European and North American myrmecochores.

Relationships between Seed Fates and Seedling Establishment in an Alpine Ecosystem

On exposed soils relationships between soil surface characteristics and seed morphological attributes the microsites of seed entrapment and influence patterns of seedling establishment. I examined seed and seedling fates of alpine species with varying morphology over a range of uniform— and mixed—particle—size soils on the Beartooth Plateau, Montana. Physical relationships between seeds and surface soils determined entrapment and retention within the zone of potential emergence (0—1 cm depth). Seed size (length or mass), the presence or absence of specialized appendages or seed coats, and the nature of the appendage or seed coat influenced numbers of seeds trapped and seed distributions among the particle sizes. Antrorse hairs, hygroscopic awns, pappuses, and mucilaginous seed coats all resulted in higher entrapment over the range of particle sizes. The effectiveness of different seed morphologies was decreased by prolonged exposure (1 yr) to the environment. In contrast to seed entrapment and retention, seedling emergence and survival depended on the ability of the different particle—size soils to meet the biological requirements of the species. Although some seedling emergence occurred in particle sizes that ranged from &lt; 0.5 to 4—8 mm, almost no seedlings survived in particle sizes larger than 1—2 mm. In particle sizes in which emergence occurred, a higher percentage of the total seeds trapped survived the first growing season as seedlings for large—seeded than for small—seeded species. For most species, the highest entrapment and retention occurred in particle sizes in which there was little or no emergence. Seedling emergence and survival were related to seed entrapment only for species with reasonably high emergence, and the R2 values were often low. Understanding seedling establishment patterns in different—particle—size soils requires knowledge of how relationships between seed morphology and soil characteristics affect entrapment patterns, and knowledge of soil particle size thresholds for seedling establishment.

PAPERS FROM A SYMPOSIUM, BOTANICAL SOCIETY OF AMERICA MEETING, HONOLULU, HAWAII, AUGUST 1992 SEED FATES: IMPORTANCE FOR STRUCTURING PLANT POPULATIONS AND COMMUNITIES

American Journal of BotanyVolume 82, Issue 3 p. 376-376 Article PAPERS FROM A SYMPOSIUM, BOTANICAL SOCIETY OF AMERICA MEETING, HONOLULU, HAWAII, AUGUST 1992 SEED FATES: IMPORTANCE FOR STRUCTURING PLANT POPULATIONS AND COMMUNITIES First published: 01 March 1995 https://doi.org/10.1002/j.1537-2197.1995.tb12642.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume82, Issue3March 1995Pages 376-376 RelatedInformation

Predation by Rodents and Bruchid Beetles on Seeds of Scheelea Palms on Barro Colorado Island, Panama

Predation by rodents on seeds of Scheelea zonensis was studied on Barro Colorado Island, Panama, during the latter half of this palm's fruiting season. The number of Scheelea bearing fruit declined steadily during this period. The proportion of both intact and bruchid-infested seeds among those accumulated under fruiting Scheelea declined, while the proportion of gnawed seeds increased. By early October, 87 percent of the Scheelea seeds sampled had been gnawed by rodents, and few intact or bruchid-infested seeds remained below parent palms. From August through October, agoutis, Dasyprocta punctata, visited Scheelea less and less frequently, while visits by squirrels, Sciurus granatensis, did not dedine. To learn the fate of late-falling Scheelea seeds, we placed small piles of thread-marked seeds, each similar to a small Scheelea fruit crop, in the forest during three successive months, a total of 400 seed each month. Of these 1200 thread-marked seeds, 57.2 percent were retrieved within 20 m of their piles 7 days after placement. Of the retrieved seeds, 22.2 percent were gnawed within 1 m of their pile, 70.6 percent were carried between 1 and 20 m before gnawing, and 7.2 percent were cached (not gnawed, but buried in the ground or covered with litter). More seeds were gnawed, and fewer cached, in September and October than in August. On Barro Colorado Island, intense seed predation by rodents on Scheelea correlates with a previously documented forestwide low in availability of fruits of all kinds, and with a decline in egg laying by bruchids.