Wood Density and Dispersal Modes of Trees Regenerating in Disturbed Forests and Agroforests in Indonesia

Natural regeneration depends on surviving propagules in the soil, seed sources from a surrounding landscape mosaic, and dispersal agents. We compiled and analyzed four sets of case studies varying in degree of disturbance, for secondary forests recovering from logging, fire, and conversion to agroforest in Sumatra or Kalimantan (Indonesia) on mineral and peat soils. Data on tree species diversity, wood density frequency distribution (indicative of successional status, databases with over 6000 species exist), and dispersal modes were compared with those for less disturbed comparator forests for the same landscapes. Undisturbed lowland dipterocarp forest in Kalimantan had close to 200 species of trees of more than 10 cm diameter at a 1 ha sample scale (and 450 at a 10-ha scale), regulation-based logging had little impact. Still, after the repeated fire a sample area of 2 ha was needed to reach the same species numbers. After forest conversion to low-management-intensity rubber agroforest, 50 tree species were found at a ha scale and close to 100 species in 3 ha. Peat swamp forest in Kalimantan and the Sumatra forest samples had close to 100 species in 1 to 2 ha. The Kalimantan forest after a repeated fire had a markedly higher fraction of low-wood-density trees (40%), but otherwise, all forests sampled were similar in overall wood density profiles. Logged-over forest managed by community (village forest) and rubber agroforest in Sumatra contained larger fractions of heavy-wood-density trees (including rubber). The majority of trees (50-70%) had birds, bats, and primates as dispersal agents in all sites. Logged-over forests on mineral soil had higher fractions of autochorous species (15%) compared to other sites. Anemochorous (wind-dispersed) species were most common (20%) in undisturbed lowland Dipterocarp forest and peat swamp forest recovering after logging and fire. Comparison between secondary forests and agroforests showed the influence of farmer selection regarding what is allowed to grow beyond the pole stage. Wood density and seed dispersal profile can be used as degradation indicators of species assemblages across various disturbance levels and types. They can also reflect the habitat quality of the surrounding forming restoration options.

Expansión de Ludwigia helminthorrhiza (Onagraceae) en Cuba

The introduction of Ludwigia helminthorrhiza (Mart.) H.Hara (Onagraceae) into Cuba, by an unknown route, as well as its successful naturalization and sustained increase in its area of occupation for over 40 years is here confirmed. The importance of the quantity and quality of its diasporas for dispersal and establishment in new territories is discussed, as well as the effectiveness of the dispersal agents. The negative impacts (difficulties in the management of aquariums, sedimentation, blocking of light entry, reduction of oxygen exchange, and displacement of native species) and the positive impacts (food for fauna and bacteria housing that reduce pollution) of the introduction of this species were identified. An alert is issued regarding the possible expansion of this species to new freshwater reservoirs in the country.

Microarthropod contributions to fitness variation in the common moss Ceratodon purpureus

The evolution of mutualism depends critically upon genetic variation in the fitness benefit to both partners. Estimates of these quantities are rare, however, because genetic variation for the interaction may be absent, aspects of the interaction may not be amenable to experimental manipulation, or the benefits to one partner may be unknown. In vitro experiments show that female mosses produce odors which attract sperm-dispersing microarthropods, but the fitness consequences of this interaction for either partner are unknown. Here we established experimental mesocosms to test for a commensal effect of sperm-dispersing microarthropods on moss reproduction. We found that of moss grown with microarthropods showed increased moss reproductive rates by five times, relative to control mesocosms, but remarkably also increased the number of reproducing genotypes, and changed the rank-order of fitness for both male and female genotypes. These results provide an estimate of the fitness benefit for mosses in the presence of microarthropods, and highlight the potential for biotic dispersal agents to alter fitness among moss genotypes in this relationship.

Rauvolfia caffra (quinine tree).

R. caffra is a tree native to Africa, where it is commonly used in traditional medicine (PROTA, 2016). This tree species has an attractive appearance and is often planted as an ornamental and shade tree. Until now, R. caffra has been listed as invasive only in Cuba, where it has escaped from cultivation and can be found growing in ruderal areas and abandoned farms (Granda and Fuentes, 1987; Oviedo Prieto et al., 2012). Its high growth rate, wide environmental tolerance, prolific seed production, shade tolerant seedlings, and the attraction of biotic dispersal agents are all factors contributing to the likelihood of this species becoming naturalized and invasive into new habitats. Consequently, this species should be monitored where introduced but not yet regarded as generally invasive.

Conservation in the crossroads of history

The first six chapters of this book describe the range of historical and contemporary processes that underlie the wealth, diversity, and divergence of natural populations and species in the Mediterranean flora. The processes of species divergence, adaptive trait variation along ecological transitions, interactions with pollinators and dispersal agents, and ongoing hybridization are, however, barely treated in conservation policy and action. After a presentation of the traditional approach to conservation based on rare species protection and the identification and conservation management of protected areas, this chapter presents arguments for a complementary approach based on the processes of plant evolution. Its primary proposal is that preventing further loss of evolutionary potential should become a major target of contemporary conservation strategies for the Mediterranean flora.

Endozoochory of Chrysobalanus icaco (Cocoplum) by Gopherus polyphemus (Gopher Tortoise) facilitates rapid germination and colonization in a suburban nature preserve

Some large-seeded plants lack effective seed dispersal agents when they are introduced as ornamental plants to new areas, but can rapidly colonize a landscape if seed dispersal functions are restored. We examined whether Gopherus polyphemus (Gopher Tortoise) facilitated the spread of Chrysobalanus icaco (Cocoplum; Chrysobalanaceae) over a 14-year period in a suburban nature preserve (in Jupiter, FL, USA) by: (i) comparing germination patterns among gut-passed, hand-depulped and whole fruit treatments, and (ii) testing hypotheses about environmental predictors of the spatial distribution of C. icaco, including information about G. polyphemus movement pathways and burrow locations. While we did not find a significant difference in the total proportion of C. icaco seeds that germinated in each treatment, time to event analysis revealed that seeds that were found in faeces germinated significantly earlier than seeds that were hand-depulped or that were planted as whole fruits, supporting a lone scarification effect. Point process modeling revealed that the density of C. icaco bushes was higher near G. polyphemus movement pathways and was lower inside Serenoa repens (Saw Palmetto) patches, supporting a positive effect of tortoise movement patterns on plant distributions. The density of C. icaco increased from west to east, consistent with westward dispersal from the four founder bushes on the east side of the study area. After removal of outliers, we also detected a negative association between C. icaco spatial density and G. polyphemus burrow density that was presumably explained by the fact that seeds defecated deep within burrows were unlikely to germinate and establish without secondary movement. The results suggest that G. polyphemus contributed to the rapid dispersal of C. icaco by scatter dispersal of seeds (via faeces) in areas where tortoises were active and that movement pathways provided suitable conditions for colonization. The spread of C. icaco by G. polyphemus over a relatively short period of time provides a valuable window into the earliest stages of the colonization process and further supports the role of Chelonians as effective seed dispersal agents for large-seeded plants.

Functional channels in mature E. coli colonies

Biofilms are important in medicine, industry and the natural environment, however their structure is largely unexplored across multiple spatial scales. We have studied the architecture of mature Escherichia coli macro-colony biofilms by means of the Mesolens, an optical system which uniquely allows simultaneous imaging of individual bacteria and over one hundred cubic millimetres of its biofilm milieu. Our chief finding is the presence of intra-colony channels on the order of 10 μm in diameter in E. coli biofilms. These channels have a characteristic structure and reform after total mechanical disaggregation of the colony. We present evidence that the channels transport particles and function to assist the absorption of nutrients. These channels potentially offer a new route for the delivery of dispersal agents or antimicrobial drugs to biofilms, ultimately lowering their impact on public health and industry.

Mapping the Flow of Forest Migration through the City under Climate Change

Rapid climate change will create extreme problems for the biota of the planet. Much of it will have to migrate towards the poles at a rate far beyond normal speeds. In this context, the concept of assisted migration has been proposed to facilitate the migration of trees. Yet current practices of assisted migration focus on “where tree species should be in the future” and thus have many uncertainties. We suggest that more attention should be paid on the flow of forest migration. Therefore, this study develops a three-step methodology for mapping the flow of forest migration under climate change. Since the migration of trees depends on the activities of their seed dispersal agents, the accessibility of landscapes for dispersal agents is mainly considered in this study. The developed method combines a least-cost path model, a graph-based approach, and a circuit theory-based model. The least-cost path model is applied to map the movement of dispersal agents, based on which graph-based indices are used to evaluate the accessibility of landscapes for dispersal agents, which in turn is used as the basis for circuit theory-based modelling to map the flow of forest migration. The proposed method is demonstrated by a case study in the Greater Manchester area, UK. The resulting maps identify areas with high probability of climate-driven migration of trees.