Dispersal Syndromes (dispersal + syndrome)

Distribution by Scientific Domains


Selected Abstracts


Spatial patterns of recruitment in Mediterranean plant species: linking the fate of seeds, seedlings and saplings in heterogeneous landscapes at different scales

JOURNAL OF ECOLOGY, Issue 6 2008
Lorena Gómez-Aparicio
Summary 1Plant recruitment is a multiphase process that takes place in environments that are heterogeneous in space and time. In this work, I analyse how environmental heterogeneity in Mediterranean forests affects dynamics of early recruitment at different scales, using the wind-dispersed tree Acer opalus subsp. granatense as a case study. 2Seed dispersal and viability, post-dispersal predation, seedling emergence and seedling and sapling survival were evaluated in different habitats (regional scale) and microhabitats (local scale). Simultaneously, a review of the literature on spatial dynamics of plant recruitment in Mediterranean systems was conducted to look for general patterns and investigate their fit to the Acer system. Nineteen woody and herbaceous species were included in the review. 3At the regional scale, Acer recruitment dynamics strongly converged among sites of the same habitat. This was mainly due to large seedling emergence and survival differences among habitats. Although most of the studies reviewed analyzed only one site per habitat type, they also support strong regional variation (either site- or habitat-specific) in recruitment patterns. 4At the local scale, Acer recruitment was microhabitat-specific, a result shared by almost all the reviewed species independently of their life form and dispersal syndrome. This was mostly due to spatial differences in seed arrival (higher under conspecifics) and seedling survival (higher under nurse shrubs). 5Spatial discordance among seed rain and recruitment was found in 60% of the reviewed species at the regional scale, and in 67% at the local scale. Acer results supported this predominant lack of concordance. Discordance among seed rain and recruitment suggests that regeneration is largely limited by safe sites than by seed availability. Because seedling survival was the limiting process with a larger impact on the magnitude and spatial pattern of recruitment, safe sites might be defined as those where seedlings have a higher survival probability. 6Synthesis: This study indicates that the influence of seed dispersal on the spatial patterns and demography of plant species could be limited in heterogeneous and stressful environments (as are found in the Mediterranean), where recruitment is restricted to a small fraction of the landscape. If we are to preserve the distribution and abundance of Mediterranean species in the face of environmental changes, we need to explicitly consider the strong patch-specificity that characterizes their recruitment process at all scales. [source]


Interspecific variation in primary seed dispersal in a tropical forest

JOURNAL OF ECOLOGY, Issue 4 2008
Helene C. Muller-Landau
Summary 1We investigated the relationships of seed size, dispersal mode and other species characteristics to interspecific variation in mean primary seed dispersal distances, mean annual seed production per unit basal area, and clumping of seed deposition among 41 tropical tree species on Barro Colorado Island, Panama. 2A hierarchical Bayesian model incorporating interannual variation in seed production was used to estimate seed dispersal, seed production, and clumping of seed rain for each species from 19 years of data for 188 seed traps on a 50-ha plot in which all adult trees were censused every 5 years. 3Seed dispersal was modelled as a two-dimensional Student's T distribution with the degrees of freedom parameter fixed at 3, interannual variation in seed production per basal area was modelled as a lognormal, and the clumping of seed rain around its expected value was modelled as a negative binomial distribution. 4There was wide variation in seed dispersal distances among species sharing the same mode of seed dispersal. Seed dispersal mode did not explain significant variation in seed dispersal distances, but did explain significant variation in clumping: animal-dispersed species showed higher clumping of seed deposition. 5Among nine wind-dispersed species, the combination of diaspore terminal velocity, tree height and wind speed in the season of peak dispersal explained 40% of variation in dispersal distances. Among 31 animal-dispersed species, 20% of interspecific variation in dispersal distances was explained by seed mass (a negative effect) and tree height (a positive effect). 6Among all species, seed mass, tree height and dispersal syndrome explained 28% of the variation in mean dispersal distance and seed mass alone explained 45% of the variation in estimated seed production per basal area. 7Synthesis. There is wide variation in patterns of primary seed rain among tropical tree species. Substantial proportions of interspecific variation in seed production, seed dispersal distances, and clumping of seed deposition are explained by relatively easily measured plant traits, especially dispersal mode, seed mass, and tree height. This provides hope for trait-based generalization and modelling of seed dispersal in tropical forests. [source]


Dispersal limitation may result in the unimodal productivity-diversity relationship: a new explanation for a general pattern

JOURNAL OF ECOLOGY, Issue 1 2007
MEELIS PÄRTEL
Summary 1Variation in diversity with habitat productivity has long been a central ecological topic. Plant diversity is mostly highest at intermediate productivity, exhibiting the unimodal (so-called ,hump-back') relationship. This relationship has been explained by both evolutionary and ecological processes, but the potential role of dispersal limitation has not been considered. 2We used European flora data to show that dispersal limitation may contribute to the unimodal productivity-diversity relationship. Species were characterized by their habitat productivity preference and dispersal probability (determined by the number of seeds and the presence of a dispersal syndrome). We calculated average relative dispersal probabilities for species assemblages occurring preferentially in different habitat productivity levels. 3At low productivity levels, species without dispersal syndromes predominate (R2 = 0.89), but at high productivity levels, species with a low number of seeds are common (R2 = 0.89). The total relative dispersal probability, combining both the dispersal probabilities attributable to the number of seeds and to the presence of dispersal syndrome, had a unimodal relationship with habitat productivity (R2 = 0.86). Thus, the unimodal productivity-diversity relationship may arise due to the minimal dispersal limitation of local richness in conditions of moderately low productivity. At very low productivity, the lack of dispersal syndromes may limit dispersal. At high productivity, the low number of seeds may limit dispersal. 4Consequently, in conditions where species pool size and biotic interactions do not vary along productivity gradients, the variation in dispersal probabilities with productivity alone can produce unimodal relationships between diversity and productivity. Thus, dispersal limitation may contribute to the observed diversity pattern and ecosystem functioning to a greater extent than usually assumed. [source]


Informed dispersal, heterogeneity in animal dispersal syndromes and the dynamics of spatially structured populations

ECOLOGY LETTERS, Issue 3 2009
Jean Clobert
Abstract There is accumulating evidence that individuals leave their natal area and select a breeding habitat non-randomly by relying upon information about their natal and future breeding environments. This variation in dispersal is not only based on external information (condition dependence) but also depends upon the internal state of individuals (phenotype dependence). As a consequence, not all dispersers are of the same quality or search for the same habitats. In addition, the individual's state is characterized by morphological, physiological or behavioural attributes that might themselves serve as a cue altering the habitat choice of conspecifics. These combined effects of internal and external information have the potential to generate complex movement patterns and could influence population dynamics and colonization processes. Here, we highlight three particular processes that link condition-dependent dispersal, phenotype-dependent dispersal and habitat choice strategies: (1) the relationship between the cause of departure and the dispersers' phenotype; (2) the relationship between the cause of departure and the settlement behaviour and (3) the concept of informed dispersal, where individuals gather and transfer information before and during their movements through the landscape. We review the empirical evidence for these processes with a special emphasis on vertebrate and arthropod model systems, and present case studies that have quantified the impacts of these processes on spatially structured population dynamics. We also discuss recent literature providing strong evidence that individual variation in dispersal has an important impact on both reinforcement and colonization success and therefore must be taken into account when predicting ecological responses to global warming and habitat fragmentation. [source]


What determines the relationship between plant diversity and habitat productivity?

GLOBAL ECOLOGY, Issue 6 2008
Martin Zobel
ABSTRACT The relationship between biodiversity and habitat productivity has been a fundamental topic in ecology. Although the relationship between these parameters may exhibit different shapes, the unimodal shape has been frequently encountered. The decrease in diversity at high productivity has usually been attributed to competitive exclusion. We suggest that evolutionary history and dispersal limitation may be even more important in shaping the diversity,productivity relationship. On a global scale, unimodal diversity,productivity relationships dominate in temperate regions, whereas positive relationships are more common in the tropics. This difference can be accounted for by contrasting evolutionary history. Temperate regions have smaller species pools for productive habitats since these habitats have been scarce historically for speciation, while the opposite is true for the tropics. In addition, dispersal within a region may limit diversity either due to the lack of dispersal syndromes at low productivity or the low number of diaspores at high productivity. Thereafter, biotic interactions (competition and facilitation) can shape the relationship. All these processes can act independently or concurrently. We recommend that the common approach to examining empirical diversity,environmental relationships should start with the role of large-scale processes such as evolutionary history and dispersal limitation, followed by influences associated with ecological interactions. [source]


Colonization of an island volcano, Long Island, Papua New Guinea, and an emergent island, Motmot, in its caldera lake.

JOURNAL OF BIOGEOGRAPHY, Issue 11-12 2001

Abstract Aim Long Island erupted catastrophically in c. 1645 with the probable destruction of its entire biota. While several expeditions have visited the island since, no survey of its flora has been published. In 1968 a small island, Motmot, emerged from its caldera lake. Motmot has been surveyed several times but not since 1988. The aim of this study was to investigate the colonization by vascular plants of this interesting nested pair of islands. Location Long Island is 55 km off the northeast coast of Papua New Guinea (PNG) and Motmot lies in its fresh water caldera lake, Lake Wisdom, c. 4 km from the rim of the surrounding volcano. Methods We conducted a complete survey of the vascular plants on Motmot and made ad hoc collections on Long Island, including surveying three small plots, over 15 days in 1999. In addition, we incorporated data from several collections lodged at the regional herbarium in Lae. Data on seed dispersal syndromes and plant habit were obtained from the literature. Results We recorded 305 species of vascular plants from Long Island, but most trees were small and the species diversity was low. Motmot was still very sparsely vegetated and only forty-five species of vascular plants were found. Communities on Motmot were unspecialized and common species widespread. The flora of Motmot was not significantly different from that on Long Island in terms of the number of species amongst higher taxa, seed dispersal syndromes or plant habits. Main conclusions Low rainfall combined with very porous soils may be responsible for the small stature and low diversity of the forest on Long Island's caldera rim. The absence of specialist littoral species on Motmot, as a result of its landlocked situation, is probably responsible for the very slow species recruitment on the island. This community appears to be functionally important for colonization by comparison with other small volcanic islands in a marine situation. [source]


Dispersal limitation may result in the unimodal productivity-diversity relationship: a new explanation for a general pattern

JOURNAL OF ECOLOGY, Issue 1 2007
MEELIS PÄRTEL
Summary 1Variation in diversity with habitat productivity has long been a central ecological topic. Plant diversity is mostly highest at intermediate productivity, exhibiting the unimodal (so-called ,hump-back') relationship. This relationship has been explained by both evolutionary and ecological processes, but the potential role of dispersal limitation has not been considered. 2We used European flora data to show that dispersal limitation may contribute to the unimodal productivity-diversity relationship. Species were characterized by their habitat productivity preference and dispersal probability (determined by the number of seeds and the presence of a dispersal syndrome). We calculated average relative dispersal probabilities for species assemblages occurring preferentially in different habitat productivity levels. 3At low productivity levels, species without dispersal syndromes predominate (R2 = 0.89), but at high productivity levels, species with a low number of seeds are common (R2 = 0.89). The total relative dispersal probability, combining both the dispersal probabilities attributable to the number of seeds and to the presence of dispersal syndrome, had a unimodal relationship with habitat productivity (R2 = 0.86). Thus, the unimodal productivity-diversity relationship may arise due to the minimal dispersal limitation of local richness in conditions of moderately low productivity. At very low productivity, the lack of dispersal syndromes may limit dispersal. At high productivity, the low number of seeds may limit dispersal. 4Consequently, in conditions where species pool size and biotic interactions do not vary along productivity gradients, the variation in dispersal probabilities with productivity alone can produce unimodal relationships between diversity and productivity. Thus, dispersal limitation may contribute to the observed diversity pattern and ecosystem functioning to a greater extent than usually assumed. [source]