Secondary Dispersal Research Articles

Evaluating dispersal potential of an invasive fish by the use of aerobic scope and osmoregulation capacity.

Non-indigenous species (NIS) can impact marine biodiversity and ecosystem structure and function. Once introduced into a new region, secondary dispersal is limited by the physiology of the organism in relation to the ambient environment and by complex interactions between a suite of ecological factors such as presence of predators, competitors, and parasites. Early prediction of dispersal potential and future ‘area of impact’ is challenging, but also a great asset in taking appropriate management actions. Aerobic scope (AS) in fish has been linked to various fitness-related parameters, and may be valuable in determining dispersal potential of aquatic invasive species in novel environments. Round goby, Neogobius melanostomus, one of the most wide-ranging invasive fish species in Europe and North America, currently thrives in brackish and fresh water, but its ability to survive in high salinity waters is unknown to date. We show that AS in round goby is reduced by 30% and blood plasma osmolality increased (indicating reduced capacity for osmoregulation) at salinities approaching oceanic conditions, following slow ramping (5 PSU per week) and subsequent long-term acclimation to salinities ranging between 0 and 30 PSU (8 days at final treatment salinities before blood plasma osmolality measurements, 12–20 additional days before respirometry). Survival was also reduced at the highest salinities yet a significant proportion (61%) of the fish survived at 30 PSU. Reduced physiological performance at the highest salinities may affect growth and competitive ability under oceanic conditions, but to what extent reduced AS and osmoregulatory capacity will slow the current 30 km year-1 rate of advance of the species through the steep salinity gradient from the brackish Baltic Sea and into the oceanic North Sea remains speculative. An unintended natural experiment is in progress to test whether the rate of advance slows down. At the current rate of advance the species will reach the oceanic North Sea by 2018/2019, therefore time for taking preventative action is short.

App Factory: A flexible approach to rehabilitation engineering in an era of rapid technology advancement

ABSTRACTThis article describes a flexible and effective approach to research and development in an era of rapid technological advancement. The approach relies on secondary dispersal of grant funds to commercial developers through a competitive selection process. This “App Factory” model balances the practical reliance on multi-year funding needed to sustain a rehabilitation engineering research center (RERC), with the need for agility and adaptability of development efforts undertaken in a rapidly changing technology environment. This approach also allows us to take advantage of technical expertise needed to accomplish a particular development task, and provides incentives to deliver successful products in a cost-effective manner. In this article, we describe the App Factory structure, process, and results achieved to date; and we discuss the lessons learned and the potential relevance of this approach for other grant-funded research and development efforts. Data presented on the direct costs and number of downloads of the 16 app development projects funded in the App Factory’s first 3 years show that it can be an effective means for supporting focused, short-term assistive technology development projects.

Shear dispersion in the turbulent atmospheric boundary layer

The problem of shear dispersion in the atmospheric boundary layer (ABL) is revisited. The aim is to improve understanding of how and why the behaviour of state‐of‐the‐art ‘random flight’ Lagrangian particle dispersion models (RFMs) can differ from that of simpler ‘random displacement’ models (RDMs or eddy diffusivity models). First an asymptotic analysis is used to obtain a formula, valid for quite general profiles of turbulent statistics and the mean wind, for the effective horizontal diffusivity of a tracer in the ABL. Second, with ‘poison gas release’ problems in mind, a large‐deviation approach is used to understand in greater detail the behaviour of the concentration in the tails of the distribution. Results are verified by solving the RFM equations numerically for a large ensemble of particles. Turbulent statistics relevant to stable and neutral boundary‐layer conditions are considered, as is the effect of non‐uniqueness in the RFM equations. The importance of three‐dimensional effects such as the effect of an Ekman spiral in the mean wind are then considered, and criteria determining whether plume widths are controlled by direct horizontal diffusion or by secondary shear dispersion effects are obtained. Finally, a quantitative account of ‘plume bending’ in the stable ABL is presented.

Birds as key vectors for the dispersal of some alien species: Further thoughts

AbstractW. Solarz, K. Najberek, A. Pociecha & E. Wilk‐Woźniak (, Diversity and Distributions, 23, 113–117) published a letter in Diversity and Distributions debating our view that waterbirds are important vectors of alien species (C. Reynolds, N. A. F. Miranda & G. S. Cumming, Diversity and Distributions, 21, 744–754; A. J. Green, Diversity and Distributions, 22, 239–247) and question whether future research into the mechanisms under‐pinning this phenomenon can be advantageous for the practical management of alien species. Additionally, Solarz et al. suggest that human activities are the primary source of all alien species introductions and that waterbirds may only act as vectors of secondary dispersal. In this letter, we respond to several arguments raised by the authors surrounding the relevance of waterbird‐mediated dispersal in the introduction and spread of alien species. We emphasize the partly deterministic nature of waterbird dispersal and the significance of long‐distance dispersal events (and hence the potential for primary introductions of new alien species across political boundaries). Finally, we reaffirm the importance of further research into dispersal by birds to improve our capacity to foresee and manage invasions of those alien species with strong capacity to spread via avian vectors.

The ecological significance of secondary seed dispersal by carnivores

AbstractAnimals 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.

Phylogenetic position of the disjunct species Musa ornata (Musaceae): first approach to understand its distribution

Musa L. commonly known as the banana group is one of the most important and oldest food crops of humankind. Among the wild relatives with ornamental interest in the genus, Musa ornata Roxb. shows a disjunct distribution between Asia and North America (Mexico). The wild occurrence of this species in Mexico has led to speculation about the evolutionary relationships with its Asian relatives. This study examined the phylogenetic relationships between intercontinental specimens of this species and, based on registered evidence, explored the more likely hypothesis about the origins of its distribution. The phylogeny of intercontinental specimens, along with other representatives of the same genus, was carried out using three molecular markers (ITS, trnL-F, and atpB-rbcL) and applying three phylogenetic reconstruction methods: maximum parsimony, maximum likelihood, and Bayesian inference. The genetic analysis of the combined dataset grouped together all the Mexican and most Asian specimens, but the monophyly of the species was not supported. The relationships suggest that Mexican populations may have originated from an Asian invasion. However, several studies and historical documents suggest the presence of Musa in America long before the arrival of Europeans. Based on its current distribution, phylogenetic evidence, and fossil record, this species’ disjunct distribution could be explained in terms of an ancestral distribution range that encompassed America and Asia, followed by its subsequent restriction to the Old World and a secondary dispersal by humans. However, further studies are necessary to shed more light on the origins of this disjunct distribution.

Features of the geological structure and gold mineralization of the ore occurrence Yuzhnoe (the Yenisei Ridge)

The relevance of the discussed issue is caused by the need to detect new gold ore deposits within the Yenisei ridge to replenish mineral resources of gold ore in Russia. The main aim of the study is to explore the features of geological structure and gold ore mineralized zones of ore occurrence Yuzhnoe in order to forecast gold ore bodies, and to substantiate the continuation of geological exploration. The methods used in the study. The exploration is implemented by the express method of prospecting gold ore deposits in difficult mountain-taiga landscapes using a complex of lithogeochemical sampling for secondary dispersion halos, schlich, point and trench sampling; spectrochemical analysis for determining gold content, ICP-MS, atomic-and-absorption, X-ray phase analysis and isotope-geochemical methods were used. The results. The complex of prospecting methods allowed the author to reveal ore-controlling zone of fold-discontinuous deformations and localize within it the ore occurrence Yuzhnoe. The latter is located in the south-eastern part of Sredne-Ishimbinskaya area in the zone of dynamic influence of Ishimbinskiy deep fault system. The gold ore mineralized zones were revealed within the ore occurrence. They are presented by a series of lode gold stockwork subparallel bedding zones with low average gold content. A detection of gold ore bodies is forecasted within the most wide and lengthy zone Centralnaya, where the geological exploration is recommended to be continued. The author hascompared the ore occurrence with model objects and determined a set of common criteria and indicators of the ore occurrence with lode gold-sulfide deposits of the Yenisei ridge - Olimpiadninskoye, Veduginskoye, etc. and with «carlin» type deposits. Conclusions. For the first time in the region the gold ore mineralized zones in carbonate-terrigenous carbonaceous sediments of kartochki and aladyinskaya series of the Middle Riphean were detected. The perspectives of gold-bearing mineralization of the eastern slope of the Yenisei ridge are defined.

Mobile forms of gold and pathfinder elements in secondary dispersion halo of Novye Pesky gold ore occurrence (South Karelia)

We investigated podzolic soil, which is formed above the host rock of Novye Pesky gold ore occurrence. Mobile forms of Au, As, Cu, Ni, Zn, Se, Ag, Te, Sb, Pb, Mo and Bi were identified with a sequential extraction method and migration form calculation by Geochemist’s Workbench in secondary dispersion halo. The gold has characteristics different from other elements: the main mobile forms of gold are water-soluble, bound to organic matter, bound to Fe and Mn-(oxy)hydroxides. The main forms of gold are AuCl2– and Au+ in the aqueous phase. Refs 42. Figs 3. Tables 5.

Seed dispersal for the unusual inflated berries of Burmeistera (Campanulaceae)

Examining dispersal is critical for understanding the diversity of Andean-centered plant lineages, like Burmeistera (Campanulaceae). One-third of its species present an unusual inflated berry. Unlike the bright colors of non-inflated fruits in the genus, these fruits are typically dull-green; however, the fact that the seeds are loosely held in the placenta and easily removed when touched seems to suggest adaptation to animal dispersal. We studied two inflated-baccate species, Burmeistera glabrata and B. borjensis, with the aim of testing the non-exclusive hypotheses that their seeds are dispersed by (1) small mammals, (2) slugs, or (3) adult flies that develop inside the fruits. In two sites in the Ecuadorian Andes, we performed observations at dusk and dawn to examine the fate of fruits and seeds; recording fruit fall, formation of holes in the fruits, and seed loss from the placenta. We documented fruit visitors with cameras, and surveyed unopened fruits for the presence of insect larvae and seed condition. Finally, we performed an experiment to examine the effect of holes and rain in germination, in order to evaluate if holes are required for seeds to leave the fruits and subsequently germinate. For both species, most fruits fell and decomposed beneath the mother plant. However, we found limited support for small mammal dispersal; videos and observations revealed that mice and squirrels are potential, but rare, seed dispersers. We found no evidence for slug or fly dispersal; fly larvae were common inside fruits, but acted exclusively as seed predators. Crickets often chewed holes in fruits on plants and on the ground. Holes did not have an effect on germination, which was induced only by rain. Hence, the majority of seeds end up under the mother plant, with rare but potentially important events of primary or secondary dispersal by small mammals. The combination of limited dispersal due to gravity and rare events of mammal dispersal may have played a critical role in the rapid diversification of Burmeistera.

The value of trophic interactions for ecosystem function: dung beetle communities influence seed burial and seedling recruitment in tropical forests.

Anthropogenic activities are causing species extinctions, raising concerns about the consequences of changing biological communities for ecosystem functioning. To address this, we investigated how dung beetle communities influence seed burial and seedling recruitment in the Brazilian Amazon. First, we conducted a burial and retrieval experiment using seed mimics. We found that dung beetle biomass had a stronger positive effect on the burial of large than small beads, suggesting that anthropogenic reductions in large-bodied beetles will have the greatest effect on the secondary dispersal of large-seeded plant species. Second, we established mesocosm experiments in which dung beetle communities buried Myrciaria dubia seeds to examine plant emergence and survival. Contrary to expectations, we found that beetle diversity and biomass negatively influenced seedling emergence, but positively affected the survival of seedlings that emerged. Finally, we conducted germination trials to establish the optimum burial depth of experimental seeds, revealing a negative relationship between burial depth and seedling emergence success. Our results provide novel evidence that seed burial by dung beetles may be detrimental for the emergence of some seed species. However, we also detected positive impacts of beetle activity on seedling recruitment, which are probably because of their influence on soil properties. Overall, this study provides new evidence that anthropogenic impacts on dung beetle communities could influence the structure of tropical forests; in particular, their capacity to regenerate and continue to provide valuable functions and services.

Life span, dispersal and age of nesting Great Grey Owls Strix nebulosa lapponica in Sweden

3,073 Great Grey Owls were banded in Sweden in 1955–2012. 416 were controlled at least once (54.6%) or recovered dead (45.4%). Three birds banded as nestlings were recovered in their 17th calendar year. Most birds were recovered during first year of life. Only 4 females were controlled breeding as 2CY birds. 91.3% of birds controlled as first time breeders were at least 4CY. Birds banded as nestlings and recovered dead between September and July moved 100.8 km (mean) with a median distance of 64 km. Juveniles controlled alive moved 45.9 km (mean) with a median distance of 23 km during first year of life. Maximum natal dispersal was 650 km. Median natal dispersal for females was 40 km, between 7 km and 115 km depending on longevity from hatching to control. Females at ages 2CY, 5CY, 8CY and 11CY had the lowest median natal dispersals. Median secondary dispersal distances (from one nest to a later nestsite) for females lay between 0 km and 9 km. For males both mean and median secondary dispersal distances were less than 3 km.

Geology, geochemistry and gold-ore potential assessment within Akimov ore-bearing zone (the Altai Territory)

The article considers the geological setting of ore-bearing zone. Geochemical zoning of secondary dispersion haloes within Akimov ore-bearing zone was analyzed. Based on analytical data, distribution of gold mineralization trace-elements was examined. Geochemical associations were identified, analyzed and geometrized. The structure of abnormal geochemical field associated with gold-silver mineralization was determined. Three promising areas for exploration activities were identified.

Intertidal invasion patterns in Canadian ports

The establishment of non-indigenous species (NIS) in natural ecosystems is a growing concern for preserving biodiversity at global, national, and regional scales. Due to commercial shipping activities, international ports serve as critical entry points for NIS and a source for secondary dispersal. Sixteen international ports in Canada representing both the Pacific and Atlantic coasts were surveyed to characterize intertidal NIS distributions. Intertidal species diversity of both NIS and native species were significantly different between the Pacific and Atlantic coasts, with higher NIS and native species diversity on the Pacific coast. However, our newly developed Invasive Species Index (a measure of the degree of invasion based on NIS and native species relative abundance) suggested that the Atlantic coast was comparatively more impacted by invasion. No direct link was found between commercial shipping activities (number of ship visits or total tonnage) and the distribution patterns of intertidal NIS in these ports. Instead, NIS distributions in port ecosystems were strongly related to latitude, salinity, sediment type, and human population size. In addition to commercial shipping, future research in conservation and management of invaded communities should consider environmental conditions and the risk posed by local anthropogenic activities (i.e. cumulative vector effects) when characterizing invasion dynamics.

Nuclear magnetic relaxation by the dipolar EMOR mechanism: Three-spin systems.

In aqueous systems with immobilized macromolecules, including biological tissue, the longitudinal spin relaxation of water protons is primarily induced by exchange-mediated orientational randomization (EMOR) of intra- and intermolecular magnetic dipole-dipole couplings. Starting from the stochastic Liouville equation, we have developed a non-perturbative theory that can describe relaxation by the dipolar EMOR mechanism over the full range of exchange rates, dipole couplings, and Larmor frequencies. Here, we implement the general dipolar EMOR theory for a macromolecule-bound three-spin system, where one, two, or all three spins exchange with the bulk solution phase. In contrast to the previously studied two-spin system with a single dipole coupling, there are now three dipole couplings, so relaxation is affected by distinct correlations as well as by self-correlations. Moreover, relaxation can now couple the magnetizations with three-spin modes and, in the presence of a static dipole coupling, with two-spin modes. As a result of this complexity, three secondary dispersion steps with different physical origins can appear in the longitudinal relaxation dispersion profile, in addition to the primary dispersion step at the Larmor frequency matching the exchange rate. Furthermore, and in contrast to the two-spin system, longitudinal relaxation can be significantly affected by chemical shifts and by the odd-valued ("imaginary") part of the spectral density function. We anticipate that the detailed studies of two-spin and three-spin systems that have now been completed will provide the foundation for developing an approximate multi-spin dipolar EMOR theory sufficiently accurate and computationally efficient to allow quantitative molecular-level interpretation of frequency-dependent water-proton longitudinal relaxation data from biophysical model systems and soft biological tissue.

Molecular phylogeny, biogeography and chromosome evolution of Malagasy dwarf geckos of the genus Lygodactylus (Squamata, Gekkonidae)

We performed a phylogenetic analysis using nuclear (RAG‐1, RAG‐2) and mitochondrial (16S) markers, a statistical Bayesian reconstruction of ancestral distribution areas and a karyological analysis on most Malagasy species of the gekkonid genus Lygodactylus. The phylogenetic analysis largely confirms major basal branching pattern of previous molecular studies, but highlights significant differences concerning both the relationships between different species groups as well as those within groups. The biogeographic analysis supports a Malagasy origin of Lygodactylus, an oversea dispersal to continental Africa and a return to Madagascar. The L. madagascariensis group (also including a new candidate species identified herein) is the most basal clade in Lygodactylus, and the sister group of a clade with all the remaining species. The second most basal clade is the L. verticillatus group, placed as the sister group of a clade comprising African and Malagasy species. The sister lineage of the L. verticillatus group originated the African radiation through an oversea dispersal out of Madagascar. Eventually, the sister lineage of the L. capensis group originated secondary dispersals from Africa to Madagascar. In Madagascar, lineage diversification in different species groups mainly occurred from southern to northern and eastern regions. Dispersal, vicariance and paleoclimatic refugia probably played a relevant role in the evolutionary history of closely related taxa and in speciation mechanisms. The cytogenetic analysis evidenced a high karyotypic variability in Lygodactylus (from 2n = 34 to 2n = 40), which is at least partly consistent with the phylogenetic relationships and the composition of the various species group. Chromosome evolution occurred independently in different lineages, mainly through a reduction in the chromosome number and starting from a putative primitive karyotype of 2n = 40 with all telocentric elements.

Diaspore heteromorphism in the invasive Bromus tectorum L. (Poaceae): Sterile florets increase dispersal propensity and distance

Within a species, the distance travelled by a particular diaspore depends on its morphology. In Poaceae, the presence of terminal sterile florets can lead to diaspore heteromorphism, which may influence dispersal. We tested the hypothesis that the presence of sterile florets favored dispersal in Bromus tectorum L., an invasive grass in the Western US.We used field and controlled experiments to study the dispersal of caryopses with and without sterile florets attached (respectively complex and simple diaspores), as well as pieces of inflorescence that detached from the mother plants. We considered both primary and secondary dispersal, as well as abiotic and biotic dispersal agents. The distance travelled by the diaspores and their attachment to animal fur were related to the presence and number of sterile florets.Abiotic agents moved diaspores over relatively short distances, both in terms of primary and secondary dispersal. A significant proportion of diaspores attached to fur, suggesting a potential for dispersal over long distances. Complex diaspores were better dispersers than simple ones (and pieces of inflorescence), and this pattern was consistent across the study. However, among complex diaspores, the number of sterile florets had little or no influence.Considering primary and secondary dispersal by abiotic and biotic agents provided a general picture of the dispersal ecology of B. tectorum. For all the dispersal steps and dispersal agents we studied, the presence of sterile florets favored dispersal. These results highlight the functional significance of diaspore heteromorphism induced by floret sterility in the dispersal of Poaceae.

Studying exotics in their native range: Can introduced fouling amphipods expand beyond artificial habitats?

Knowledge of the habitat use patterns of introduced species in their native or naturalized range can provide unique insights into processes of secondary dispersal and colonization of natural habitats. Caprellid amphipods are small mobile marine epibionts with limited natural dispersal. The global distribution of some caprellid species is mostly the result of anthropogenic transport; however, their subsequent spread beyond artificial habitats is poorly understood. A biogeographic approach, mainly focused on the native-range ecology of introduced and common fouling caprellid amphipods of southern Europe, was used to understand the implications of habitat use patterns for predicting their spread in the introduced regions. Specifically, abundance and composition of caprellid populations were compared among different primary habitats including artificial (floating pontoons), sheltered and wave-exposed rocky shores along the southern and southeastern coasts of Brazil. The findings indicated that artificial habitats act as reservoirs for globally distributed species in both their native and introduced ranges, while endemic species are more scarcely represented. Environmental conditions provided by primary habitats appear important in structuring caprellid assemblages on secondary substrata (basibiont species). Most wide-ranging caprellids were negatively correlated with the level of wave exposure, being more abundant in sheltered (artificial or natural) than in exposed habitats. In this context, Caprella scaura and Paracaprella pusilla, the two introduced caprellids recorded in the Mediterranean, where they are virtually restricted to artificial habitats, may become established in sheltered and even highly polluted natural habitats but hardly colonize wave-exposed rocky shores.

Drivers of Spatial Variation in the Role of Ants as Secondary Seed Dispersers.

The spatial variation in the outcome of the interaction between secondary dispersers and seeds is superimposed upon the variation produced by primary dispersers. Investigating the factors that drive the outcome of the interactions with secondary seed dispersers thus represents an essential refinement to our understanding of the complete seed dispersal process. We studied the interactions between two ponerine ants (Pachycondyla striata Smith, 1858 and Odontomachus chelifer (Latreille, 1802)) with fruits experimentally set on the ground, and estimated the effects of ants on seedling establishment in three areas distributed along a 2-km stretch of a Brazilian Atlantic rainforest that differ in soil properties and vegetation physiognomies. We tested the hypothesis that interactions are more frequent, resulting in greater seedling establishment at the site with harsher abiotic and biotic conditions. Both ant species removed fruits frequently and have a positive effect on seedling establishment in all study areas, but fruit removal did not differ among areas, while seedling establishment was more pronounced at the site with stressful abiotic conditions. The two ant species differed in important aspects of their seed dispersal services, including the propensity to interact with seeds. As a result, both the species of ant and abiotic conditions interact at the scale of 2 km to determine the fate of seeds interacting with ants, thus creating a mosaic of outcomes with variable benefits to plants.

Seed handling by primary frugivores differentially influence post-dispersal seed removal of Chinese yew by ground-dwelling animals.

Seed handling by primary frugivores can influence secondary dispersal and/or predation of post-dispersal seeds by attracting different guilds of ground-dwelling animals. Many studies have focused on seeds embedded in feces of mammals or birds; however, less is known about how ground-dwelling animals treat seeds regurgitated by birds (without pulp and not embedded in feces). To compare the effect of differential seed handling by primary dispersers on secondary seed removal of Chinese yew (Taxus chinensis var. mairei), we conducted a series of exclosure experiments to determine the relative impact of animals on the removal of defecated seeds (handled by masked palm civet), regurgitated seeds (handled by birds) and intact fruits. All types of yew seeds were consistently removed at a higher rate by rodents than by ants. Regurgitated seeds had the highest removal percentage and were only removed by rodents. These seeds were probably eaten in situ without being secondarily dispersed. Defecated seeds were removed by both rodents and ants; only ants might act as secondary dispersers of defecated seeds, whereas rodents ate most of them. We inferred that seeds regurgitated by birds were subjected to the highest rates of predation, whereas those dispersed in the feces of masked palm civets probably had a higher likelihood of secondary dispersal. Seeds from feces attracted ants, which were likely to transport seeds and potentially provided a means by which the seeds could escape predation by rodents. Our study highlighted that primary dispersal by birds might not always facilitate secondary dispersal and establishment of plant populations.

Explanations for water whitening in secondary dispersion and emulsion polymer films

ABSTRACTThe loss of optical transparency when polymer films are immersed in water, which is called “water whitening,” severely limits their use as clear barrier coatings. It is found that this problem is particularly acute in films deposited from polymers synthesized via emulsion polymerization using surfactants. Water whitening is less severe in secondary dispersion (SD) polymers, which are made by dispersing solution polymers in water without the use of surfactants. NMR relaxometry in combination with optical transmission analysis and electron microscopy reveal that some of the water sorbed in emulsion polymer films is contained within nanosized “pockets” or bubbles that scatter light. In contrast, the water in SD polymer films is mainly confined at particle interfaces, where it scatters light less strongly and its molecular mobility is reduced. The addition of surfactant to a SD creates a periodic structure that displays a stop band in the optical transmission. The total amount of sorbed water is not a good indicator of polymers prone to water whitening. Instead, the particular locations of the water within the film must be considered. Both the amount of water and the size of the local water regions (as are probed by NMR relaxometry) are found to determine water whitening. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 1658–1674