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.     

Seed Predation by Rodents and Implications for Plant Recruitment in Defaunated Atlantic Forests

Rodents are known to perform post‐dispersal seed predation in tropical rain forest, but there is little information on the identity of these seed predators and how they select their seeds. Using cafeteria experiments, we found that seed mass, rodent body mass, and the ratio of seed/rodent mass were determinants of seed consumption.     

Leaf-cutting ant nests support less dense and impoverished seed assemblages in a human-modified Caatinga dry forest

Regenerating forests make up an increasingly large portion of tropical landscapes worldwide and regeneration dynamics may be influenced by leaf-cutting ants (LCA), which proliferate in disturbed areas and collect seeds for fungus culturing. Here, we investigate how LCA influences seed fate in human-modified areas of Caatinga dry forest. We evaluate the seed deposition and predation on Atta opaciceps nests, foraging habitat surrounding nest and control habitat away of nest influence of 15 colonies located along a forest cover gradient during the rainy and dry seasons. For each habitat, four 50-cm² plots were established and all seeds on the soil surface were collected along 1 year. We recorded 13,628 seeds distributed among 47 species and 36.57% of the total seeds did not show any sign of predation. Nest mound habitats supported low-density and species-poor seed assemblages, which were taxonomically distinct from the control habitats. These effects only occurred in the rainy season. The proportion of undamaged seeds were similar across the habitats. While forest cover did not influence seed assemblage in terms of species richness or seed predation, it did interact with habitat type via increments in seed abundance as forest cover increased across the nests. Forest cover also affected seed composition, but only in the rainy season. These results indicate that LCA decrease seed deposition in areas under their influence, particularly on the nest mounds. As LCA profit from human disturbance in the Caatinga, their role as seed ‘sinks’ should be enhanced in disturbed Caatinga patches, particularly during the rainy season, when most of the plant recruitment occurs. Our findings reinforce the importance of LCA as drivers of forest dynamics and resilience in human-modified landscapes.     

Bushmeat Hunting Alters Recruitment of Large-seeded Plant Species in Central Africa

We investigated the effect of local hunting on plant recruitment at the community level in the Ngotto Forest, Central African Republic. It is the first study of this kind in the afrotropics. To compare our results with previous studies conducted in the neotropics, we used the protocol proposed byNuñez-Iturri and Howe. We compared animal relative abundances and seed length, density and diversity of seedlings at two sites with contrasting anthropogenic pressures: one with low hunting pressure (LH) and one with high hunting pressure (HH). Furthermore, we investigated how density and diversity of recruitment vary with seed length in the two sites. Both sites exhibit similar soil, climate and tree species composition, and have never been logged. Large mammals (frugivores and herbivores) were extirpated from HH and relative abundance of medium-sized frugivores drastically decreased in HH compared with LH. In HH, diversity of seedlings was reduced compared with LH, especially for large-seeded plant species dispersed by large game mammals. The approach used in this study shows promising perspectives to investigate the effects of human disturbances on the regeneration of tropical forests. Furthermore, in the afrotropical context of a lack of data on plant–animal ecological relationships, seed length appears to be a good predictor of the strength of the deficit of plant recruitment due to large mammal extirpation because of hunting. Thus, more efforts are needed to study the ecological roles of large-seeded plants in order to better understand the effects of their disappearance on tropical forest resilience.     

Multiscale drivers of restoration outcomes for an imperiled songbird

Habitat restoration is a cornerstone of conservation, particularly for habitat‐limited species. However, restoration efforts are seldom rigorously monitored at meaningful spatial scales. Poor understanding of how species respond to habitat restoration programs limits conservation efficacy for habitat‐restricted species like the Golden‐winged Warbler (Vermivora chrysoptera, GWWA). We provide one of the first concerted assessments of a national conservation program aimed at restoring songbird habitat across its breeding range. We studied GWWA response to forest habitat restoration across two broad regions with opposing population trajectories and assessed factors driving species use of restored habitats across multiple spatial scales. From 2015 to 2017, we conducted 1,145 (n = 457 locations) and 519 point counts (n = 215 locations) across the Appalachian Mountains and Great Lakes (respectively) within restored habitats. Warbler abundance within restored habitats across the Great Lakes varied with latitude, longitude, elevation, forest type, and number of growing seasons. In the Appalachian Mountains, occupancy () varied with longitude, elevation, forest type, and number of growing seasons. Detections were restricted to areas within close proximity to population centers (usually <24 km) in the Appalachian Mountains, where GWWAs are rare ( = 0.22, 95% confidence interval [CI]: 0.20–0.25), but not in the Great Lakes, where GWWAs remain common ( = 0.87, 95% CI: 0.84–0.90). Our study suggests that, even when best management practices are carefully implemented, restoration outcomes vary within/across regions and with multiscale habitat attributes. Although assessments of concerted habitat restoration efforts remain uncommon, our study demonstrates the value of monitoring data in the adaptive management process for imperiled species.     

Hunting and Plant Community Dynamics in Tropical Forests: A Synthesis and Future Directions

This synthesis builds on the preceding articles of this Special Section and has three goals. We first review the nascent literature that addresses indirect effects of hunting for tropical forest plant communities. Next, we highlight the potential indirect effects of hunting for other groups of organisms. Our final goal is to consider what could be done to ameliorate the demographic threats to harvest-sensitive game species caused by unsustainable hunting. Three conclusions are possible at this time concerning the impact of hunting for tropical forest plant communities: (1) Hunting tends to reduce seed movement for animal-dispersed species with very large diaspores; (2) Hunting reduces seed predation by granivorous vertebrates for species with large seeds; and (3) Hunting alters the species composition of the seedling and sapling layers. The cascading effects of hunting are already known to affect bruchid beetles and dung beetles and are likely to affect other, nongame taxa. To ameliorate these problems, several lines of research should be further explored to facilitate the development of game management plans including: (1) alternative use of sources of animal protein; (2) income supplementation for local people from sources other than wild meat; (3) outreach and extension activities for communities; (4) recognition and facilitation of the shifting of attitudes towards hunting; (5) implementation of community-based wildlife management programs in regulated-use areas such as extractive reserves; and (6) landscape-scale conservation planning that maximizes the source-sink dynamics of harvested and unharvested game populations and enforces game regulations in strictly protected areas.     

食种子动物对三种锦鸡儿属植物繁殖更新的影响

锦鸡儿属(Caragana)植物是黄土高原植被的重要组分,具有固氮、耐旱的特性,对黄土丘陵沟壑区的植被恢复具有重要意义。作者于2002–2003年对该属本地种白毛锦鸡儿(C.licentiana)和甘蒙锦鸡儿(C.opulens)及外来种中间锦鸡儿(C.intermedia)种子被动物取食情况进行了比较研究。2003年白毛锦鸡儿种子散落前的虫害率为88.2%,甘蒙锦鸡儿为29.7%±1.7%,中间锦鸡儿为43.2%±4.8%。种子落地后,白毛锦鸡儿和甘蒙锦鸡儿的种子被小啮齿动物取食的比例在各种微生境下均为100%,且取食速度很快,在种子放置后4d内即全部被取食。中间锦鸡儿种子被取食率则因微生境的不同而不同:在灌丛下被取食率为100%,在半阳坡的开阔草地上为85.0%±10.0%,在种植植物未成功的水平阶地上为31.0%±8.7%,且取食速度相对较慢。研究结果表明,食种子动物的取食大大减少了白毛锦鸡儿和甘蒙锦鸡儿的种子量以及种子传播萌发的机会。但食种子动物可能充当了白毛锦鸡儿4.0%硬实种子的传播者,从而有助于白毛锦鸡儿实现种子途径的更新;中间锦鸡儿种子无论在散落前还是散落后受食种子动物的影响均很小。     

Mammal Abundances and Seed Traits Control the Seed Dispersal and Predation Roles of Terrestrial Mammals in a Costa Rican Forest

In Neotropical forests, mammals act as seed dispersers and predators. To prevent seed predation and promote dispersal, seeds exhibit physical or chemical defenses. Collared peccaries (Pecari tajacu) cannot eat some hard seeds, but can digest chemically defended seeds. Central American agoutis (Dasyprocta punctata) gnaw through hard‐walled seeds, but cannot consume chemically defended seeds. The objectives of this study were to determine relative peccary and agouti abundances within a lowland forest in Costa Rica and to assess how these two mammals affect the survival of large seeds that have no defenses (Iriartea deltoidea, Socratea exorrhiza), physical defenses (Astrocaryum alatum, Dipteryx panamensis), or chemical defenses (Mucuna holtonii) against seed predators. Mammal abundances were determined over 3 yrs from open‐access motion‐detecting camera trap photos. Using semi‐permeable mammal exclosures and thread‐marked seeds, predation and dispersal by mammals for each seed species were quantified. Abundances of peccaries were up to six times higher than those of agoutis over 3 yrs, but neither peccary nor agouti abundances differed across years. Seeds of A. alatum were predominantly dispersed by peccaries, which did not eat A. alatum seeds, whereas non‐defended and chemically defended seeds suffered high levels of predation, mostly by peccaries. Agoutis did not eat M. holtonii seeds. Peccaries and agoutis did not differ in the distances they dispersed seeds. This study shows that seed fates are contingent upon many factors such as seed defenses, frugivore–granivore abundances, and seed‐handling capabilities. Mammal–seed interactions are complex; the outcomes of these interactions depend on the inherent characteristics of seeds and their potential dispersers.     

A Host Creates an Enemy‐free Space for Mistletoes by Reducing Seed Predation Caused by a Woodboring Beetle: A Hypothesis

Parasitic plants rely on host plants for nutrition. The number of host species varies largely between groups, from single species or genus to hundreds of species. Relative abundance of the host and evolutionary history are the main requisites for parasitic plants to develop specificity to abundant hosts. In the present study, we suggest a novel mechanism by which a hemiparasitic mistletoe can develop local specificity mediated by its host. First, we describe a novel interaction in which a woodboring beetle (Hypothenemus obscurus) preys on mistletoe seeds (Psittacanthus plagiophyllus) attached to tree branches. This beetle preys more frequently on seeds deposited on branches of non‐host species than on branches of its unique local host species (53 percent on average vs. 26 percent respectively). We hypothesize that local host specificity for this mistletoe could be partly mediated by beetle‐host incompatibility, since the host offers a predation‐free space in which mistletoes have better chances to grow. Furthermore, that the exceptional gum exudates produced by this unique host species minimize beetle attacks on branches, thus reducing predation of mistletoe seeds. This novel tritrophic interaction opens an avenue for research on macroscopic host‐specificity mechanisms that occur at the level of the host bark and that have been poorly studied by plant ecologists.     

Increased Productivity and Reduced Seed Predation Favor a Large‐seeded Palm in Small Atlantic Forest Fragments

Large‐seeded plants are especially vulnerable to the loss of seed dispersers in small forest fragments. The palm Attalea humilis goes against this trend by reaching high abundances in small remnants. Productivity, seed dispersal and seed predation of A. humilis were investigated in two large (2400 and 3500 ha) and three small (19, 26 and 57 ha) Atlantic Forest fragments in southeastern Brazil. Palms in the small fragments produced more female inflorescences, resulting in a higher fruit production in these places. Seed dispersal rates were higher in the large fragments, where scatter hoarding was more frequent. Scolytine beetles were the main seed predators and damaged a larger number of seeds in small fragments, but predation by rodents and bruchine beetles was low irrespective of fragment size. As scolytines do not necessarily kill the seeds, low predation by bruchines and rodents, together with its own high productivity, allow A. humilis to be more abundant in small fragments despite the scarcity of its main dispersers. This increased abundance, by its turn, can increase competitive interactions between A. humilis and other plants in small fragments. Thus, abundance patterns of A. humilis are a good example of fragmentation affecting the balance of ecological interactions in a complex way, emphasizing the role of preserving ecological processes for conserving biodiversity in fragmented tropical landscapes. Abstract in Portuguese is available at http://www.blackwell‐synergy.com/loi/btp .     

Role of small rodents in the seed dispersal process: Microcavia australis consuming Prosopis flexuosa fruits

Understanding the functional role of animal species in seed dispersal is central to determining how biotic interactions could be affected by anthropogenic drivers. In the Monte Desert, mammals play different functional roles in Prosopis flexuosa seed dispersal, acting as opportunistic frugivores (endozoochorous medium‐sized and large mammals) or seed hoarders (some small sigmodontine rodents). Our objective was assessing the functional role of Microcavia australis, a small hystricognathi rodent, in the fruit removal and seed deposition stages of P. flexuosa seed dispersal, compared to sympatric sigmodontine rodents. In situ, we quantified fruit removal by small rodents during non‐fruiting and fruiting periods, and determined the distance seeds were transported, particularly by M. australis. In laboratory experiments, we analysed how M. australis stores seeds (through scatter‐ or larder‐hoarding) and how many seeds are left in caches as living seeds, relative to previous data on sigmodontine rodents. To conduct field studies, we established sampling stations under randomly chosen P. flexuosa trees at the Ñacuñán Man and Biosphere Reserve. We analysed fruit removal by small rodents and seed dispersal distance by M. australis using camera traps focused on P. flexuosa fruits covered with wire screen, which only allowed entry of small animals. In laboratory trials, we provided animals with a known number of fruits and assessed seed conditions after removal. Small rodents removed 75.7% of fruit supplied during the non‐fruiting period and 53.2% during the fruiting period. Microcavia australis and Graomys griseoflavus were the main fruit removers. Microcavia australis transported seeds to a mean distance of 462 cm and cached seeds mainly in scatter‐hoards, similarly as Eligmodontia typus. All transported seeds were left in fruit segments or covered only by the endocarp, never as predated seeds. Microcavia australis disperses P. flexuosa seeds by carrying fruits away from a source to consume them and then by scatter‐hoarding fruits and seeds.     

Seed dynamics of resprouting shrubs in grassy woodlands: Seed rain,predators and seed loss constrain recruitment potential

Abstract Measuring the fate of seeds between seed production and seedling establishment is critical in understanding mechanisms of recruitment limitation of plants. We examined seed fates to better understand the recruitment dynamics of four resprouting shrubs from two families (Fabaceae and Epacridaceae) in temperate grassy woodlands. We tested whether: (i) pre‐dispersal seed predation affected seed rain; (ii) post‐dispersal seed predation limited seed bank accumulation; (iii) the size of the seed bank was related to seed size; and (iv) viable seeds accumulated in the soil after seed rain. There was a distinct difference in seed production per plant between plant families with the legumes producing significantly more seeds per individual than the epacrids. Seed viability ranged from 43% to 81% and all viable had seed or fruit coat dormancy broken by heat or scarification. Pre‐dispersal predation by Lepidopteran larvae removed a large proportion of seed from the legume seed rain but not the epacrids. Four species of ants (Notoncus ectatomoides, Pheidole sp., Rhytidoponera tasmaniensis and Iridomyrmex purpureus) were major post‐dispersal seed removers. Overall, a greater percentage of Hardenbergia (38%) and Pultenaea (59%) seeds were removed than the fleshy fruits of Lissanthe (14%) or Melichrus (0%). Seed bank sizes were small (<15 seeds m^?2) relative to the seed rain and no significant accumulation of seed in the soil was detected. Lack of accumulation was attributed to seed predation as seed decay was considered unlikely and no seed germination was observed in our study sites. Our study suggests that seed predation is a key factor contributing to seed‐limited recruitment in grassy woodland shrubs by reducing the number of seeds stored in the soil.     

Seed Availability as a Limiting Factor in Forest Recovery Processes in Costa Rica

Abandoned pastures and secondary forests are increasingly prominent features of tropical landscapes. Forest regrowth on abandoned pastures is generally slow and virtually limited to regeneration from seeds from external sources, since agricultural activities alter site conditions. We hypothesize that seed availability is a major limiting factor in forest recovery on abandoned pastures. This hypothesis was tested by studying the seed bank, seed rain, and seed predation in a small pasture (1 ha) situated in a forest‐pasture mosaic in northwestern Costa Rica. The tree seed density in the pasture seed bank was much lower (21/m²) than the density in the seed bank of a neighboring secondary forest (402/m²). Within a period of five weeks, 23 tree seeds entered the pasture by seed rain. This number is low compared to densities found in closed forests but higher than densities reported in other studies where virtually no seeds were found beyond 20 m from the forest edge. Possibly the small size of the pasture with seed sources nearby and the small‐scale landscape mosaic enhance seed dispersal. Predation limits the seed density in pastures, with 42% of the woody species consumed by predators. The low seed density in the seed bank, and hampered recruitment combined with significant losses, pose severe restrictions to forest recovery on abandoned pastures. Moderate land use, and small sized clearings with seed sources nearby may increase the pace of recovery. Nevertheless, forest establishment may still take a considerable time. Thus, enlarging the available pool of species may be a worthwhile management strategy.     

The ecophysiology of seed persistence: a mechanistic view of the journey to germination or demise

Seed persistence is the survival of seeds in the environment once they have reached maturity. Seed persistence allows a species, population or genotype to survive long after the death of parent plants, thus distributing genetic diversity through time. The ability to predict seed persistence accurately is critical to inform long‐term weed management and flora rehabilitation programs, as well as to allow a greater understanding of plant community dynamics. Indeed, each of the 420000 seed‐bearing plant species has a unique set of seed characteristics that determine its propensity to develop a persistent soil seed bank. The duration of seed persistence varies among species and populations, and depends on the physical and physiological characteristics of seeds and how they are affected by the biotic and abiotic environment. An integrated understanding of the ecophysiological mechanisms of seed persistence is essential if we are to improve our ability to predict how long seeds can survive in soils, both now and under future climatic conditions. In this review we present an holistic overview of the seed, species, climate, soil, and other site factors that contribute mechanistically to seed persistence, incorporating physiological, biochemical and ecological perspectives. We focus on current knowledge of the seed and species traits that influence seed longevity under ex situ controlled storage conditions, and explore how this inherent longevity is moderated by changeable biotic and abiotic conditions in situ, both before and after seeds are dispersed. We argue that the persistence of a given seed population in any environment depends on its resistance to exiting the seed bank via germination or death, and on its exposure to environmental conditions that are conducive to those fates. By synthesising knowledge of how the environment affects seeds to determine when and how they leave the soil seed bank into a resistance–exposure model, we provide a new framework for developing experimental and modelling approaches to predict how long seeds will persist in a range of environments.     

Linking scorpion (Arachnida: Scorpiones) assemblage with fragment restoration in the Brazilian Atlantic Forest

Habitat loss due to forest degradation can induce changes in species richness due to variation in species susceptibility to environmental stress. This is particularly important for species with highly specific microhabitats, such as scorpions that inhabit forest habitats. In this study, the richness and abundance of these arachnids were compared between an old-growth (mature) and secondary (65 years under natural restoration) forests. Seasonal influence was also evaluated by comparing diversity between dry and wet seasons. The animals were collected through nocturnal active search using UV lamps and pitfall traps in both areas (old-growth and secondary). Both environments showed similar breast heights of trees, litter depth, litter dry mass, and understory density, indicating a high level of restoration. Scorpion diversity (characterized by Tityus pusillus, T. neglectus, T. brazilae, Bothriurus asper, and Ananteris mauryi) and abundance were not influenced by the different historical usage of both areas. In contrast, the abundance of these arachnids was highly affected by rain regimes, and increased during the dry season. These results suggest that 65 years was a sufficient time period for restoration, making it possible to maintain similar scorpion assemblages in both environments.     

中国东部常绿阔叶林退化群落分析及恢复重建研究的一些问题

人类干扰活动导致常绿阔叶林的类型和数量减少,替而代之的是大面积处于不同退化程度的次生林、次生灌丛等,因此加大对其退化特征以及恢复重建的研究已是非常必要而迫切的任务。在对此类植被进行广泛调查基础上,结合数量分类法(在区域尺度上)对退化常绿阔叶林进行类型划分和群落特征的界定,并对一些影响群落恢复和改造的问题进行了讨论。这些问题是(1)不同的人类干扰方式对常绿阔叶林退化群落的形成发生深刻的影响,因此关注人类干扰方式,尤其是土地利用方式的变化和常绿阔叶林退化群落形成之间的关系应当进行重点研究;(2)退化群落的种类组成具有自身的特征,同样具有较高的物种多样性,对维持整个地区的物种多样性具有独特的贡献;(3)萌枝更新对退化群落的结构和动态起着重要作用,加强这方面的研究有助于探讨群落退化的机制和植被恢复途径;(4)种子传播方式、传播距离对于退化群落的种类组成具有重要影响,并影响到群落结构、动态和物种多样性,也应是进一步加强的研究领域。希望通过这些问题的研究,有助于明了群落的退化机理,并为其恢复改造提供依据。     

Phoresy in animals: review and synthesis of a common but understudied mode of dispersal

Phoresy is a type of interaction in which one species, the phoront, uses another species, the dispersal host, for transportation to new habitats or resources. Despite being a widespread behaviour, little is known about the ecology and evolution of phoresy. Our goal is to provide a comprehensive review of phoretic dispersal in animals and to bring renewed attention to this subject. We surveyed literature published between 1900 and 2020 to understand the extent of known higher-level taxonomic diversity (phyla, classes, and orders) and functional aspects of animals that use phoretic dispersal. Species dispersing phoretically have been observed in at least 13 animal phyla, 25 classes, and 60 orders. The majority of known phoronts are arthropods (Phylum Euarthropoda) in terrestrial habitats, but phoronts also occur in freshwater and marine environments. Marine phoronts may be severely under-represented in the literature due to the relative difficulty of studying these systems. Phoronts are generally small with low mobility and use habitats or resources that are ephemeral and/or widely dispersed. Many phoronts are also parasites. In general, animals that engage in phoresy use a wide variety of morphological and behavioural traits for locating, attaching to, and detaching from dispersal hosts, but the exact mechanisms behind these activities are largely unknown. In addition to diversity, we discuss the evolution of phoresy including the long-standing idea that it can be a precursor to parasitism and other forms of symbioses. Finally, we suggest several areas of future research to improve our understanding of phoresy and its ecological and evolutionary significance.