Dispersal Mode Research Articles

Untangling the roles of centrality and environmental contribution in diversity patterns across spatial scales

AbstractThe application of graph theory to metacommunity ecology allows a deeper analysis of the effect of network structure on diversity patterns. Here, we set out to test the role of network centrality metrics and environmental characteristics in diversity patterns of pond macroinvertebrate metacommunities. We tested two approaches to construct the networks: one used the percolation distance, whereas the other was based on a community‐contingent distance. The role of each patch within the network was then analyzed using its centrality value. Later, we analyzed the relationships between the macroinvertebrate diversity and centrality metrics for four study sites. The calculated diversity metrics cover different facets of biodiversity at two scales: pond and pondscape. Environmental characteristics of the studied ponds were also included. All relationships were tested considering the entire macroinvertebrate dataset, but also differentiated by dispersal mode (i.e., active vs. passive) and considering the two types of network approaches analyzed. The results were mostly consistent when comparing the network approaches used. Centrality metrics tended to be positively related to alpha and negatively to beta diversity. Environmental uniqueness showed a positive effect on beta diversity metrics, regardless of the dispersal mode. We only observed a weak negative relationship between eutrophication and species richness of active dispersers. Pond size showed a positive effect on both alpha and beta diversity, but was detected more frequently on alpha diversity metrics. We could not find evidence for a clear negative effect of habitat degradation on diversity. We found a greater importance of environmental characteristics versus the centrality metrics for both alpha and beta diversity of active dispersers, while a combination of their contributions for passive dispersers. An unexpected importance of centrality was observed for alpha diversity of passive dispersers. Using empirical data, we demonstrate that the centrality of a patch in an undirected network affects diversity regardless of the approach used to construct the networks, with a higher influence at local scale regardless of the dispersal mode. This study broadens knowledge of the relationships between environmental features and network centrality, demonstrating the important role of centrality as a determinant of diversity in metacommunities.

Systematic reduction in seed rain of large‐seeded and endozoochorous species in pastures compared to forests along a tropical elevational gradient

AbstractQuestionsHow do seed rain biomass and richness change from old‐growth tropical forests to pastures at different elevations? How do seed mass and seed dispersal mode change from forests to pastures across these elevations? What implications do these changes have for the recovery of deforested areas in tropical mountains?LocationOld‐growth montane forests and livestock pastures along an elevational gradient (1,000–3,000 m a.s.l.), located at Podocarpus National Park, San Francisco Reserve and surrounding agricultural lands, Andes of southern Ecuador.MethodsWe collected seed rain for a 3‐month period using 324 traps installed at eighteen 1‐ha plots across elevations. Half of the traps were installed in nine 1‐ha forest plots, and the other half in nine 1‐ha pasture plots. For each trap, we identified the seeds and measured seed rain biomass and richness. We also recorded seed traits and calculated community‐weighted means of seed mass and seed dispersal mode (proportion of endozoochory).ResultsForests received a higher seed rain biomass than pastures, but only at the lowest elevation. Seed rain richness did not differ between habitat types at all elevations. Community‐weighted means of seed mass and the proportion of endozoochorous species declined from forests to pastures, especially at the lower elevations.ConclusionsAlthough seed rain biomass and richness were overall similar between forests and pastures, large‐seeded and endozoochorous species were generally poorly represented in the seed rain of pastures compared with that of forests. These findings show that biomass and richness of seed rain may be insufficient to quantify the restoration potential of natural seed rain in deforested areas. Information on seed traits, such as seed mass and seed dispersal mode, is important to optimize restoration efforts towards the regeneration of diverse old‐growth forests along elevational gradients in tropical mountains.

Conspecific cues mediate habitat selection and reproductive performance in a haplodiploid spider mite

Abstract Selection of a suitable habitat by animals before settlement is critical for their survival and reproduction. In silk-spinning arthropods like spider mites, denser webs offer protection from predation and serve as a dispersal mode. Settling in habitats with the presence of conspecifics and silk webs can benefit the habitat-searching females. Silk and conspecifics usually coexist, but their distinct effects on female colonization have received little attention. In this study, we used a haplodiploid spider mite, Tetranychus ludeni Zacher (Acari: Tetranychidae), to examine the impact of conspecific cues, including cues from ovipositing conspecifics and silk, on habitat selection and subsequent reproductive performance of females. Results show that females significantly preferred habitats with cues from neighboring conspecifics and silk and neighboring conspecifics induced additive effect to that of silk on habitat selection. Conspecific cues did not boost female reproduction but facilitated females laying larger eggs that were more likely to be fertilized and to develop into daughters. When given a choice between silk-covered and clean habitats, females preferred silk-covered habitats, laid a similar number of eggs with similar size, but produced more daughters, suggesting that T. ludeni females can adjust the size threshold for fertilization in response to the current social environment. Knowledge of this study improves our understanding of spider mite habitat selection and post-settlement reproductive performance behaviors.

The role of dispersal limitation in the forest biome shifts of Europe in the last 18,000 years

AbstractAimHow the ability of plants to move towards newly favourable habitats (dispersal limitation) impacts the change of biome distribution and transition under fast climate warming is still debated. Analysing vegetation change in the past may help to clarify the relative importance of underlying ecological processes such as climate, biotic interactions, and dispersal. In this study, we investigated how dispersal limitation affected the distribution of European forests in the last 18,000 years.LocationSouthern and Central Europe.TaxonSpermatophyta.MethodsUsing the LPJ‐GM 2.0 model (an extension of LPJ‐GUESS), we simulated European vegetation from the end of the Last Glacial Maximum (18.5 ka) to the current time (0 ka). Using biome reconstructions from pollen data as reference, we compared the performance of two dispersal modes: with no migration constraints or seed limitation (free dispersal mode), and with plant establishment depending on seed dynamics and dispersal (dispersal limitation mode).ResultsThe model run, including migration processes, was better at capturing the post‐glacial expansion of European temperate forests (and the longer persistence of boreal forests) than the setting assuming free dispersal, especially during periods of rapid warming. This suggests that a number of (temperate) tree taxa experienced delayed occupancy of climatically suitable habitats due to a limited dispersal capacity, i.e., post‐glacial migration lags.Main ConclusionsOur results show that including migration processes in model simulations allows for more realistic reconstructions of forest patterns under rapid climate change, with consequences for future projections of carbon sequestration and climate reconstructions with vegetation feedback, assisted migration and forest conservation.

Overlooked seed‐dispersal modes and underestimated distances

AbstractLong‐distance seed dispersal is a crucial process determining the distribution of plant biodiversity and, therefore, of major interest in biogeography and macroecology. A recent data article on Global Ecology and Biogeography presented a database of estimated seed‐dispersal distance classes for the European flora, where the classes are defined by the morphological dispersal syndrome of species associated with a single dispersal mode. We explain how this article overlooks literature on the unreliable capacity of dispersal syndromes for predicting key dispersal modes involved in long‐distance seed dispersal. Consequently, the published database does not consider the possibility that individual species can naturally be dispersed through multiple modes (polychory). Most importantly, the database consistently omits seed‐dispersal modes that can mediate dispersal distances several orders of magnitude longer than the mode predicted by the syndromes. This is the case of many terrestrial and aquatic plants dispersed by animals, notably ungulates and waterbirds, and that of coastal plants dispersed by the sea. We thus urge caution when using this database to model potential plant dispersal because long‐distance seed dispersal is underestimated in many species.

Seed‐dispersal mode and habitat connectivity underpin variation in carbon stocking between Brazilian biomes

Abstract In tropical forests, about 60%–80% of woody plant species depend on animal–plant interactions for dispersal. The dependence on animal species for dispersal makes this interaction very fragile in the face of anthropogenic changes in land use. Disrupting seed‐dispersal processes, principally zoochoric dispersal, could significantly alter the long‐term carbon storage potential of tropical forests. An important question is how landscape structure changes tree carbon stocks in different types of tropical vegetation and how variation is mediated by the dispersal mode of animal (zoochoric) or abiotic (non‐zoochoric) seeds. We focused on tree plots at 126 sites in Brazil spanning four types of forest and savanna vegetation, and calculated carbon stored in zoochoric, non‐zoochoric, and large frugivore‐dispersed species. Our results showed that carbon stocks in zoochoric species and non‐zoochoric species differ significantly among vegetation types, with rainforests having higher stocks in zoochoric species and deciduous seasonally dry tropical forests having higher values in non‐zoochoric species. A greater area of native vegetation promotes higher proportions of carbon stocks dispersed by large frugivore species, whereas a higher mean shape index reduces this proportion. Synthesis. This study highlights that seed‐dispersal type underpins the variation in carbon stocks between vegetation types and that the maintenance of habitat of large dispersers and connectivity are key for retaining carbon stocks in zoochoric species, particularly in rainforest and cerrado sensu stricto.

Time since first naturalization is key to explaining non‐native plant invasions on islands

AbstractAimInvestigating the extent of insular invasions by non‐native species (i.e., the number of islands they occupy) is central to island conservation. However, interrelationships among plant life history traits, naturalization histories, and island characteristics in determining island occupancy by non‐native plant species are poorly understood. We investigated whether island occupancy by different non‐native plant species declines in relation to their year of first naturalization and whether periods of first naturalization differ among growth forms, dispersal modes, and biogeographic origins. Then, we asked if non‐native plants that naturalized more recently occur more frequently on islands that are large, less isolated, and close to urban areas. We contrasted trends across growth forms, dispersal modes, and biogeographic origins.Location264 offshore islands in northern Aotearoa New Zealand.TaxaVascular plant species.MethodsWe combined field surveys and published data for 767 non‐native plant species on the islands. We categorized each species according to its growth form (n = 3), dispersal mode (n = 4) and biogeographic origin (n = 5) and identified its year of first naturalization in Aotearoa New Zealand. We tested our hypotheses using ANCOVA and generalized linear models (GLMs).ResultsThere were similar declines in island occupancy in relation to the year of first naturalization in Aotearoa New Zealand across all trait and biogeographic origin categories. First naturalization times of herbaceous species, those with unspecialized dispersal modes, and those originating from Eurasia and the Mediterranean basin were disproportionately earlier than other categories. Non‐native plants with more recent first naturalization occur more frequently on large islands close to urban areas, but not on less isolated ones. Relationships with island characteristics did not differ among trait and biogeographic origin categories.Main ConclusionsOverall, time of first naturalization was more important than trait and biogeographic origin categories in explaining non‐native plant invasion patterns on islands. Since there were similar relationships between island occupancy and the year of first naturalization in Aotearoa New Zealand for all categories, management bodies should focus on non‐native plant species of trait and biogeographic origin categories that have naturalized recently (e.g., woody species from other regions within Oceania), and on large islands close to urban areas. Introduction and naturalization histories provide essential context for interpreting the role of plant traits and biogeographic origin in understanding plant invasions on islands.

Temperature-dependent dispersal and ectotherm species' distributions in a warming world.

Dispersal is a crucial component of species' responses to climate warming. Warming-induced changes in species' distributions are the outcome of how temperature affects dispersal at the individual level. Yet, there is little or no theory that considers the temperature dependence of dispersal when investigating the impacts of warming on species' distributions. Here I take a first step towards filling this key gap in our knowledge. I focus on ectotherms, species whose body temperature depends on the environmental temperature, not least because they constitute the majority of biodiversity on the planet. I develop a mathematical model of spatial population dynamics that explicitly incorporates mechanistic descriptions of ectotherm life history trait responses to temperature. A novel feature of this framework is the explicit temperature dependence of all phases of dispersal: emigration, transfer and settlement. I report three key findings. First, dispersal, regardless of whether it is random or temperature-dependent, allows both tropical and temperate ectotherms to track warming-induced changes in their thermal environments and to expand their distributions beyond the lower and upper thermal limits of their respective climate envelopes. In the absence of dispersal mortality, warming does not alter these new distributional limits. Second, an analysis based solely on trait response data predicts that tropical ectotherms should be able to expand their distributions polewards to a greater degree than temperate ectotherms. Analysis of the dynamical model confirms this prediction. Tropical ectotherms have an advantage when moving to cooler climates because they experience lower within-patch and dispersal mortality, and their higher thermal optima and maximal birth rates allow them to take advantage of the warmer parts of the year. Previous theory has shown that tropical ectotherms are more successful in invading and adapting the temperate climates than vice versa. This study provides the key missing piece, by showing how temperature-dependent dispersal could facilitate both invasion and adaptation. Third, dispersal mortality does not affect the poleward expansion of ectotherm distributions. But, it prevents both tropical and temperate ectotherms from maintaining sink populations in localities that are too warm to be viable in the absence of dispersal. Dispersal mortality also affects species' abundance patterns, causing a larger decline in abundance throughout the range when species disperse randomly rather than in response to thermal habitat suitability. In this way, dispersal mortality can facilitate the evolution of dispersal modes that maximize fitness in warmer thermal environments.

REPRODUCTIVE ECOLOGY OF AN EVERGREEN DRY SEASON-BLOOMING TREE SPECIES, WALSURA TRIFOLIATA (A. JUSS.) HARMS (MELIACEAE)

Walsura trifoliata is an evergreen dry season-blooming hermaphroditic tree species. The flowers are nectariferous and characterized by urceolate androecium, strong protandry and secondary pollination mechanism, protruded bifid stigma displaying receptivity, self-compatibility and facultative xenogamy without the function of spontaneous autogamy. The floral traits indicate generalist pollination syndrome and adaptation for entomophily, with bees effecting mostly geitonogamy and wasps and butterflies effecting mostly xenogamy. Fruit-set is highest in xenogamy. Fruit is a globular drupe with 1-2 seeds embedded in fleshy aril. Seed dispersal modes include zoochory, barochory and hydrochory. The study shows that the function of generalist pollination syndrome, entomophily, facultative xenogamy and polychory enable this tree species to achieve highest fruit-set, maintain genetic variation through cross-pollination, and disperse its seeds to different distances in the forest ecosystem.

Seed flotation in some widespread, oceanic‐dispersed trees and their island‐endemic congeners

AbstractVariation in plant dispersal capabilities strongly influences the assembly of island plant communities. Many tropical plants have seeds capable of long‐distance, often oceanic, dispersal; in some cases, these taxa speciate into island interior endemics with reduced dispersal capabilities, though whether this is a general pattern is debated. Flotation times are highly variable among plants with oceanic dispersal and between such plants and their inland congeners. Here, we experimentally compared salt‐water flotation in three woody plant genera in Palau, Micronesia, comparing broadly distributed and island endemic species within each genus. The widespread Calophyllum inophyllum (with oceanic and vertebrate dispersal), C. soulattri (vertebrate dispersal), and Terminalia catappa had substantially longer flotation than their inland endemic relatives C. pelewense and T. crassipes. This supports the “Loss of dispersal ability” hypothesis for Calophyllum though, for Terminalia, additional phylogenetic information is needed to determine T. crassipes' sister species. Seed flotation in the widespread, oceanic dispersed Pandanus tectorius did not significantly differ from that of the Palau endemics P. palawensis and P. aimiriikensis. Our results highlight that differences among taxa in dispersal modes, speciation modes, and their interactions may influence the assembly of island floras.

Phylogeny And Historical Biogeography Of The Order Pandanales

Reconstruction of the dispersal history and formation of modern ranges of various taxa is one of the actual problems of modern biogeography. Molecular genetic biogeography based on the analysis of phylogenetic relationships of taxa of different levels began to develop actively at the end of the XX century. Currently, this method is the most objective and represents the basis for reconstruction of scenarios of the origin and dispersal of various groups of plants. Due to recent transformation of views on the phylogenetic relationships of Pandanales, the reconstruction of tracks and modes of dispersal of representatives of the order Pandanales becomes an actual task. Representatives of all 5 families of Pandanales sensu APG IV were selected for the study and two cladograms were constructed. Based on the molecular-genetic cladistic method the region of hypothetical origin and probable dispersal scenarios of the families of the order Pandanales were determined. The order Pandanales is treated as originated in Laurasia and its differentiation began on the territory of Tibet. Dispersal of the representatives of the basal family Velloziaceae took place by long-distance transport via the Bering Land Bridge to South America (approximately 115 Mya). Velloziaceae dispersed in the New World vicariously in South America, then it was distributed to sub-Atlantic Africa by long-distance transport, and finally also vicariously to the east, south and north of the continent. It is shown, that the modern range of the representatives of rest Pandanales is the result of both types of dispersal – vicariously and long-distance transport.

A transoceanic journey: Melanochlamys diomedea's first report in the North Atlantic

Abstract Egg masses from an unknown mollusc have been found in South-West Iceland since 2020, but it was not until September 2023 that the adult organism was collected. Morphological analysis of both adults and egg masses pointed towards the identification of the species as Melanochlamys diomedea. This was further confirmed through DNA analyses using COI, H3, and 16S rRNA markers, which established the presence of a new non-indigenous species in the North Atlantic. Members of the genus Melanochlamys have predominantly been found in the Indo-Pacific basin and the Pacific Ocean, with only one species known to exist across the Madeira Islands, Canary Islands, and Cape Verde in the Atlantic. The known distribution range of M. diomedea extends from Alaska to California on the Pacific side of North America, where it typically inhabits sandy-muddy areas of the littoral in the tidal zone and below. It is not known how the species arrived in Iceland. However, maritime transport through either ballast water or biofouling is being considered as the most likely mode of dispersal.

The dispersal potential of endangered plants versus non‐native garden escapees

Abstract Amidst climate change, enhancing plant dispersal pathways is crucial for adapting ecosystems and preserving biodiversity. In our human‐dominated landscapes, urban and rural green spaces, especially gardens, are promising conduits for plant dispersal. Non‐native plants are known to benefit from these spaces, yet the potential benefits for at‐risk native plants remain unclear. Here, I synthesized data on dispersal traits, comparing endangered native plants with non‐endangered and non‐native species in Germany. To make my analysis pertinent to understanding the potential role of gardens in aiding the dispersal of at‐risk native plants, I further contrasted the dispersal ecology of garden‐friendly endangered plants with non‐native plants known to escape gardens. I analysed several traits including seed weight, terminal velocity, dispersal distance, germination rate, dispersal mode, seed structures and seedbank type. Overall, dispersal traits between native and non‐native plants showed minor, but in some cases statistically significant differences. Endangered plants were more often wind‐dispersed and more frequently had seed appendages conducive to a wider range of dispersal vectors. Conversely, non‐native plants leaned more towards non‐assisted local dispersal, heavier seeds and more persistent seed banks. Other traits were largely consistent across groups. This research shows that endangered native plants possess a dispersal ecology similar to non‐native species, which frequently spread from green spaces like gardens. Thus, integrating endangered flora into our green spaces could help to promote an essential aspect of species survival: dispersal.

Biomorphological traits and leaf dry matter content are important to plant persistence in a highly unstable volcanic ground

The colonisation of newly formed territories by plants during primary succession is a crucial stage in the formation of ecosystems. Adaptations of species to withstand harsh environment allow them to survive and form pioneer communities. We analysed ten categorical and quantitative plant traits to examine their role in plant resistance to substrate instability in primary volcanic habitats. The research questions were: 1) which plant traits enable plants to persist under the most unstable ground conditions?; 2) what are the ecological strategies of species that grow under the condition of stress, such as low mineral nutrition, coupled with intense disturbance, such as unstable ground? The research was conducted on the Tolbachinsky Dol plateau in Kamchatka, Russia, on loose volcanic sediments of the 1975 eruption. At altitudes ranging from 700 m a.s.l. to 1000 m a.s.l., 40 sample plots were established along the gradients of altitude and degrees of ground instability. The species composition of vascular plants and the percentage cover of species, as well as other habitat characteristics, were assessed. Linear models were used to investigate the relationship between traits and ground instability. The principal component analysis was used to identify groups of characteristic traits. Leaf dry matter content (LDMC) had the largest explained variance. The LDMC community weighted means decreased with increasing disturbance (ground instability). A whole set of categorical traits, i.e. plant functional types, characterised the adaptation of plants to unstable ground. These characteristics include life-form (according to Serebryakov classification), density of shoots arrangement, morphology of underground organs, and, to a lesser extent, dispersal mode. The study analysed 45 species, and it was found that only four of them were adapted to perform under conditions of high substrate instability. The study showed that the mutual interaction of a suite of biomorphological traits and leaf density characteristics formed a syndrome of pioneer species adapted to unstable ground. The ecological strategies of the majority of species in the studied communities were characterised by the predominance of the stress-tolerant strategy, explained by the extremely poor mineral nutrition in the primary habitats. Under conditions of both low nutrient availability and high disturbance intensity, species with a mixed stress-tolerant-ruderal strategy are favoured. In the gradient of increasing disturbance, the role of the ruderal axis increased while stress tolerance decreased. However, the role of ecological strategy may be weakened by the presence of other important adaptive traits.

Spider and vascular plant assemblages in subarctic peat bogs are complementary ecological indicators of variation in local and landscape factors

Despite their specific biodiversity and the ecosystem services they furnish, peat bogs remain poorly understood, especially in terms of their responses to changes at multiple spatial scales. Many subarctic peat systems face acute risks, due to current global change. In this study, using a multi-metric approach, we assessed the relative value of plants and spiders as ecological indicators in contrasted peat bogs of a French archipelago (St. Pierre-et-Miquelon), located in the North Atlantic. In 2021, pitfall trapping and suction sampling collected spiders while phytosociological relevés were used to document vascular plants. A total of 69 species of spiders and 38 species of vascular plants were identified, and both taxonomic (TD) and functional (FD, based on traits related to dispersal, size and ecosystem functioning) diversity were then estimated for three levels of species relative abundance (Hill numbers q = 0, 1 and 2) using the iNEXT 3D package for alpha diversity as well as iNEXT beta3D for beta diversity. As expected, patterns of TD and FD were highly correlated for each Hill number, but also between Hill numbers for spiders, indicating a surprisingly low effect of species abundance on (spider) diversity patterns. On the contrary, differences between sites were more visible for plants species when species coverage was considered (q = 1 and q = 2), for both TD and FD, and for alpha and beta diversity. RLQ and Fourth corner analyses indicated differences based on functional traits between sites which were significantly associated with relationships between dispersal modes and mostly local factors for plant assemblages. Finally, variance partitioning on assemblage composition showed the importance of an interaction between local and landscape factors for both plants and spiders, with a relatively high importance of local factors alone for plants. Our study thus revealed the high complementary of spider vs. plant assemblage-based metrics as indicators of changing local conditions in peat bogs, confirming these both experience rapid change in subarctic climates.

Climate and dispersal limitation drive tree species range shifts in post-glacial Europe: results from dynamic simulations

IntroductionThe ability of species to colonize newly suitable habitats under rapid climate change can be constrained by migration processes, resulting in a shift of the leading edge lagging behind the ameliorating climate, i.e. migration lag. The importance and extent of such migration lags during the forest expansion after the Last Glacial Maximum (LGM) are still debated. Similarly, the relative importance of the main drivers of post-glacial vegetation dynamics (temperature, dispersal limitation, and competition) is still discussed in the literature.MethodsWe used the dynamic global vegetation model LPJ-GM 2.0 to reconstruct the range shifts of 16 competing major European tree species after the LGM (18.5 ka BP) until recent times (0 ka BP). We simulated two dispersal modes by allowing free establishment whenever the climatic conditions suited the species (free dispersal), or by accounting for migration processes in the simulated vegetation dynamics (dispersal limitation). We then calculated thermal and range shift velocities, competition at establishment, thermal and dispersal lags for each species and dispersal mode. Finally, we compared our simulated range shift velocities with pollen-derived migration rates.ResultsThe simulation assuming limited dispersal resulted in more accurate migration rates as compared to pollen-derived migration rates and spreading patterns. We found no marked migration lags in the post-glacial establishment of pioneer species (Pinus sylvestris and Betula pubescens). Under the free dispersal mode, the remaining temperate species expanded rapidly and almost synchronously across central Europe upon climate warming (Bølling-Allerød interstadial). Differently, the northward spread of temperate species simulated under dispersal limitation happened mainly during the Holocene and in successive waves, with late spreaders (e.g. Fraxinus excelsior) experiencing multi-millennial dispersal lags and higher competition.DiscussionOur simulation under dispersal constraints suggests that the post-glacial tree expansion in Europe was mainly driven by species-specific thermal requirements and dispersal capacity, which in turn affected the order of taxa establishment and thus the degree of competition. Namely, taxa with less cold-tolerance and relatively low dispersal ability experienced the highest migration lags, whereas the establishment of pioneer species was mostly in equilibrium with the climate.

Ancestral state reconstruction reveals extensive homoplasy in nutlet characters of Cynoglossinae (Boraginaceae, subfam. Cynoglossoideae, tribe Cynoglosseae)

Recent phylogenetic studies have challenged the traditional classification of the subtribe Cynoglossinae, which was based on nutlet characteristics. To investigate the evolution of fruit traits related to dispersal modes in this complex group, we conducted a study using scanning electron microscopy to examine 28 taxa representing all previously recognized lineages of the subtribe. Cynoglossinae displays four main types of nutlets: marginate, emarginate, flat wing, and incurved wing. Our findings reveal the arrangement of glochids and their structure, including the number of apical hooks, and their surface ornamentation is highly variable both across and within these four main types. We reconstructed the phylogenetic tree with four main clades (i.e., Clades I–IV) using Maximum likelihood analysis. In addition, we mapped four nutlet traits (i.e., nutlet margin, nutlet glochid, glochid sculpture, and glochid hooks) associated with different dispersal modes using ancestral state reconstruction analysis. The ancestor of subtribe Cynoglossinae was inferred to have marginate and glochidiate nutlets, with glochids externally provided with complex spiny tubercles and bearing at least four hooks at the tip as well as epizoochory dispersal mode. These ancestral states have been retained in Clade II (East Asian-Australian-African Cynoglossum-Lindelofia clade) and Clade III (Mediterranean-Asian Cynoglossum-Solenanthus-Trachelanthus clade), with several independent shifts to emarginate fruits. Transitions from marginate to wide-winged nutlets have occurred at least four independent times, facilitating wind-assisted dispersal in Clade I (Microparacaryum clade), Clade IV (Paracaryum-Mattiastrum-Rindera clade), Rindera tetraspis, and Mattiastrum crista-galli (both belonging to Clade III), where a transition from tuberculate to papillate surface has also occurred.

Evolution of Seed Dispersal Modes in the Orchidaceae: Has the Vanilla Mystery Been Solved?

Orchid seeds are predominantly wind-dispersed, often developed within dry, dehiscent fruits that typically release millions of dust-like seeds into the air. Animal-mediated seed dispersal is a lesser-known phenomenon in the family and predominantly occurs in groups belonging to early-diverging lineages bearing indehiscent, fleshy fruits with hard, rounded, dark seeds. In this review, we explore the evolutionary trends of seed dispersal mechanisms in Orchidaceae, focusing on the pantropical genus Vanilla. Notably, certain Neotropical species of Vanilla produce vanillin-aromatic compounds synthesized naturally in their fruits, which plays a pivotal role in seed dispersal. Ectozoochory occurs in dry, dehiscent fruits, whose seeds are dispersed by (i) male euglossine bees collecting the fruit’s vanillin aromatic compounds and (ii) female stingless bees collecting the fruit’s mesocarp. Endozoochory occurs in (iii) highly nutritious, indehiscent fruits consumed by terrestrial mammals or (iv) fleshy, dehiscent fruits whose mesocarp is consumed by arboreal mammals. Wind dispersal appears to be a derived state in Orchidaceae and, given its predominance, a trait likely associated with enhanced speciation rates. Zoochory primarily occurs in groups derived from early-diverging lineages; occasional reversions suggest a link between dispersal mode and fruit and seed traits. Interestingly, fruit dehiscence and fleshiness in Vanilla lack phylogenetic signal despite their role in determining dispersal modes, suggesting potential environmental adaptability.

Comparing the effect of larval dispersal strategies on morphological versus genetic differentiation in two neotropical fiddler crabs

AbstractThe dispersal mode of estuarine invertebrates has a strong effect on genetic variability and phenotypic expression, potentially maintaining gene flow among widely separated populations or limiting connectivity among close ones. Understanding the dispersal strategies effects can support adequate strategies for environment management and understand the evolutionary history of the studied species. A comparative study on the effect of larval dispersal strategies (export vs retention) along the overall geographic distribution ranges of adult populations of two co‐distributed fiddler crab species was performed. Geometric morphometric techniques were used to evaluate morphological differentiation in the shape of the carapace and major cheliped propodus in 10 populations of Minuca mordax and five populations of Leptuca leptodactyla. Potential genetic differentiation was assessed using DNA sequence data from up to 170 fiddler crab specimens, corresponding to the mitochondrial gene cytochrome c oxidase subunit 1 (COX1). Patterns of genetic and morphological characteristics diverged among populations of both species. In terms of morphology, populations of both species showed intraspecific variation in the shape of the carapace and, to a lesser extent, in the major cheliped propodus. This observed intraspecific variation followed a clear geographic pattern of morphometric differentiation, in which the geographic origin is associated with a phenotypic response to the environmental diversity along the extended Brazilian coast. In contrast, there are shared haplotypes in populations separated by more than 4000 km, but with significant ΦST values among most populations of L. leptodactyla and M. mordax, suggesting a moderate to high level of gene flow. Therefore, it can be concluded that the split of the Central South Equatorial Current has not acted as an efficient long‐term barrier to the dispersal of larvae in both species. In M. mordax, a slight limitation of genetic exchange can be observed between the southernmost populations and the remaining ones. This first evidence of genetic structuring within this widely distributed species is consistent with its documented strategy to retain larvae in the estuarine environments. However, occasional transport of larvae to more open coastal waters seems to maintain stepwise gene flow between neighboring populations. Overall, our results still provide evidence of more pronounced genetic homogeneity in a species with a larval export strategy (L. leptodactyla) compared to a species with a larval retention strategy (M. mordax). This suggests that larval dispersal strategies, coupled with the microhabitat in which the respective species occur, have a noticeable effect on the degree of gene flow. Most likely, these biological aspects are further influenced by the estuarine and coastline geomorphology.

Dispersal modes affect Rhamnaceae diversification rates in a differentiated manner.

The evolution of dispersal modes has been proposed to promote the diversification of angiosperms. However, little is known about the relative impact of different dispersal modes on plant diversification. We test the association between dispersal modes and diversification rates using Rhamnaceae, the cosmopolitan buckthorn family, as a model. We found that species with diplochory have the highest diversification rates followed by those with myrmecochory and ballistic dispersal, while lineages dispersed by vertebrates and wind have relatively low diversification rates. The difference in diversification rates may be closely linked to the difference in dispersal distance and ecological interactions implied by each dispersal mode. Species which disperse over larger geographical distances may have much higher speciation rates due to the increased chance of establishing isolated populations due to geological barriers or habitat fragmentation. However, long-distance dispersal may also increase the chance of extinction. By contrast, species with short-distance dispersal modes may have low speciation rates. Complex interactions with the surrounding environment may, however, impact diversification rates positively by increasing plant survival and reproductive success.