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Evaluating the factors influencing the patterns of female dispersal in mammals is critical to understanding its importance for male and female reproductive strategies and the evolution of social systems. In western lowland gorillas, females emigrate from their natal group (natal dispersal) but also disperse between groups multiple times in their life (secondary dispersal). This strategy is uncommon in primates and may reflect females seeking to reduce feeding competition or female choice for males that can provide protection against infanticide. In this study, we test how inbreeding avoidance, group size, and male competitive ability could influence female dispersal in western gorillas, using 25 natal and 285 secondary dispersal events collected over 20 years at Mbeli Bai. We found that while all females dispersed out of their natal group, presumably to avoid inbreeding, females also left their group before having their first offspring when the dominant male was not their father, pointing towards unconditional dispersal by nulliparous females. Regarding secondary dispersal, we found that females were more likely to stay with males that were at the beginning of their tenure than transfer and more likely to disperse away from (presumably old) males that were near the end of their tenure or closer to their death. Females were also more likely to leave larger groups for smaller ones suggesting a potential effect of within-group feeding competition or avoidance of outsider males or predators. This study highlights the intersexual conflict found in gorillas: while female choice for high-quality males may influence the formation of their relatively rare social system, smaller group size may be more important for females than previously thought, which runs counter to the males’interest of having a high number of females.

Animals play an important role in the seed dispersal of many plants. It is increasingly recognized, however, that the actions of a single disperser rarely determine a seed's fate and final location; rather, multiple abiotic or animal dispersal vectors are involved. Some carnivores act as secondary dispersers by preying on primary seed dispersers or seed predators, inadvertently consuming seeds contained in their prey's digestive tracts and later depositing viable seeds, a process known as diploendozoochory. Carnivores occupy an array of ecological niches and thus range broadly on the landscape. Consequently, secondary seed dispersal by carnivores could have important consequences for plant dispersal outcomes, with implications for ecosystem functioning under a changing climate and across disturbed landscapes where dispersal may be otherwise limited. For example, trophic downgrading through the loss of carnivores may reduce or eliminate diploendozoochory and thus compromise population connectivity for lower trophic levels. We review the literature on diploendozoochory and conclude that the ecological impact of a secondary vs. primary seed disperser depends on the relative dispersal distances, germination success, and the proportion of seeds exposed to secondary dispersal by carnivores. None of the studies up to present day have been able to rigorously assess the ecological significance of this process. We provide a framework of the components that determine the significance of diploendozoochory across systems and identify the components that must be addressed in future studies attempting to assess the ecological importance of diploendozoochory.

Seed dispersal may involve different vectors of dispersal in two or more sequential phases (i.e., diplochory). However, contributions of each phase to the overall seed dispersal effectiveness (SDE) are poorly understood and hard to evaluate due to post-dispersal processes that affect seed and seedling survival. We investigated the simultaneous bird (phase 1, in plant canopy) and ant (phase 2, on the floor) contributions to SDE with the ornithochoric shrub Erythroxylum ambiguum in a Brazilian Atlantic forest. Twelve species of birds fed on fruit and dispersed approximately 26 % of the seed crop. The remaining seed crop, 90 % of which contained viable seeds, fell to the ground beneath the parental plant. Ants either cleaned seeds in fruits or carried fallen fruit and seeds from bird feces to their nests. Although E. ambiguum has no adaptation for ant dispersal, ants were as quantitatively important as birds. Birds and ants equally increased germination rates compared to controls. However, birds deposited seeds farther from the parent, where seedling survival was higher (78 %) than it was beneath the parent (44 %), whereas ants carried seeds to their nests, where seedling survival was higher (83 %) than in controls away from their nests (63 %). Diplochory allowed a 42 % increase in SDE compared to dispersal in phase 1 alone. High lipid content in the fruit pulp of E. ambiguum may facilitate the inclusion of ants in a second step of dispersal after diaspores reach the floor. Ants can also buffer the dispersal of diplochorous plants against decreases in phase 1 dispersers.

To assess the potential of domestic traffic for the regional spread of nonindigenous species (NIS), we surveyed the hull of an oceanographic vessel serving routes in the southwestern Atlantic and Southern Ocean. Sampling was performed while the vessel was in the water and in dry-dock in the Port of Mar del Plata, Argentina. We found 120 taxa belonging to 14 different invertebrate groups, including 53 species, 47 morphospecies, and 20 taxa identified at higher taxonomic levels. Ten of these species have not been reported for the Port of Mar del Plata and adjacent areas prior to the present study, and eight are new records for the entire Argentine coast. While both in-water and dry-dock sampling allowed for the detection of native, non-native, and cryptogenic fauna, more samples and species were obtained in dry-dock. Dry-dock richness estimates amounted to up to ~ 110 hull fouling species. Despite specific logistic challenges, dry-dock sampling should be considered by managers assessing vector strength due to its greater species detection power. The present results highlight the potential for domestic vessel spread of hull fouling marine NIS, and pinpoint likely future additions to the non-native fauna inventory in the southwestern Atlantic.

Key messageFor the first time the interaction of vegetation structure, wind speed and seed attributes on seed suspension on the plants was quantified by means of wind tunnel experiments.The seed hanging above ground, a part of the vertical distribution and a determinant of seed fate, may be affected by vegetation structure. However, how seed hanging on vegetation layers during secondary wind dispersal is linked to vegetation feature has rarely been studied. We investigated the effect of vegetation structure on seed hanging in a wind tunnel. The number of hanging seeds during secondary dispersal of 30 species with various attributes (mass, height, width, length, shape, projected area, wing loading, terminal velocity) was measured in four vegetation structures (pure herb one-layer vegetation, pure shrub one-layer vegetation, herb + shrub uniform two-layer vegetation, and herb + shrub aggregated two-layer vegetation). The proportions of seeds on vegetation layer in one-layer vegetation were significantly more than in two-layer vegetation. The correlation between seed morphological attributes (mass, height, width, length, shape index, and projected area) and the proportion of hanging seeds on vegetation layers differed between the herb and shrub layer but was not affected by vegetation's horizontal and vertical distribution. Our study indicates that the complexity of vegetation structure decreases the seed hanging on the vegetation layer, and the role of seed attributes in determining seed hanging on vegetation layer is modified more largely by the life-form rather than by the spatial structure of vegetation. It is the first systematical study on how vegetation structure affects seed hanging, deeply enhancing our understanding of the effects of vegetation structure on vertical seed distribution.

Fil: Gorne, Lucas Damián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina

Biosecurity protocols designed to prevent invader spread have become integral to invasive species management strategies. However, application of many proposed spread-prevention practices is inhibited due to low practicality, high expense, undesirable non-target effects and a lack of known efficacy. Here, we examine the use of direct steam exposure to induce substantial fragment (i.e. propagule stage) degradation of seven invasive macrophytes: Ceratophyllum demersum, Crassula helmsii, Egeria densa, Elodea canadensis, Elodea nuttallii, Lagarosiphon major and Potamogeton crispus. Each species was independently exposed to steam treatments in loose clumps of three fragments, steamed at a distance of 2–3 cm from the source, for varied exposure times: 10 s, 30 s, 1 min, 2 min, and 5 min. Furthermore, we develop and apply a novel degradation scale describing visual tissue biodegradation stages and/or resumption of growth for fragmentary propagules. Steam treatments were observed to be highly efficacious, with total degradation being induced by 10 s of direct steam exposure. This was apparent for all species following a seven day recovery period, except C. demersum, which took until 21 days. Conversely, control specimens displayed excellent survival and/or viability (i.e. resumption of growth). Therefore, we argue that this innovative, yet simple technique can be used to improve biosecurity practices to inhibit the spread of invasive macrophytes.

Plant migration is a multi-stage process often driven by multiple dispersal vector systems. Water-mediated dispersal (hydrochory) is known to move propagules of nonaquatic species over long distances, but whether propagule morphology affects floating processes is an open question. We used a multi-species approach to assess the role of propagule morphology in the dispersal of primarily wind-dispersed tree species in different urban rivers; the impact of hydraulic structures (locks, spillways) on floating was also considered. We released tagged propagules of eight tree species (Acer platanoides, Acer negundo, Acer saccharinum, Ailanthus altissima, Fraxinus excelsior, Robinia pseudoacacia, Tilia platyphyllos, Ulmus glabra) in the main lowland Spree River and in the small tributary Panke River (Berlin, Germany) and directly observed the fate of the floating propagules over river sections of 1,200 m. Our results demonstrate the following: (1) Water is an effective dispersal agent for wind-dispersed tree species, extending typical wind-related transport distances by several times. (2) Interspecific differences in transport distances reflect propagule characteristics (dry weight, maximum wing width) and river system. (3) Propagule morphology also affects deposition patterns as it was generally the large propagules that were trapped along semi-natural embankments in slow flow areas. (4) Hydraulic structures hampered but did not entirely stop water-mediated dispersal and diminished the effects of propagule morphology on floating processes. These results provide novel insights into the functioning of hydrochory as an important dispersal vector of tree species in river systems and as a driver of plant invasions.

Large frugivores play an important role as seed dispersers and their extinction may affect plant regeneration. The consequences of such extinctions depend on the likelihood of other species being functionally redundant and on how post-dispersal events are affected. We assess the functional redundancy of two seed dispersers of the Atlantic Forest, the muriqui (Brachyteles arachnoides) and the tapir (Tapirus terrestris) through the comparison of their seed dispersal quality, taking into account post-dispersal events. We compare tapirs and muriquis for: (1) the dung beetle community associated with their feces; (2) the seed burial probability and burial depth by dung beetles; and (3) the seed mortality due to predators or other causes according to burial depth. We determine how seed burial affects seed dispersal effectiveness (SDE) and compare the dispersal quality of four plant species dispersed by these frugivores. Muriqui feces attract 16-fold more dung beetles per gram of fecal matter and seeds experience 10.5-fold more burial than seeds in tapir feces. In both feces types, seed mortality due to predation decreases with burial depth but seed mortality due to other causes increases. Total seed mortality differ within plant species according to the primary disperser. Therefore, the effect of seed burial on SDE varies according to the plant species, burial depth, and primary disperser. As tapirs and muriquis differently affect the seed fate, they are not functionally redundant. Since the effect of the primary disperser persists into the post-dispersal events, we should consider the cascading effects of these processes when assessing functional redundancy.

— The migration activity of ammocoetes of the European river lamprey Lampetra fluviatilis does not decline following the primary dispersal from the nest, but continues throughout the larval stage, ensuring the redistribution of juveniles along the river channel . The mechanisms of their diurnal and seasonal dynamics are determined both by the anatomical and physiological development of individuals and by external factors (illumination, water level, availability of sediments and food particles suitable for a particular developmental stage). The generalization of our own long-term studies and literature data shows that larvae are mobile and move mainly downstream, and the migration aspect of this part of the life cycle should be divided into phases: primary dispersal of early larvae, secondary redistribution of ammocoetes, downstream migration of smolts to the sea.