58 Matching Annotations
  1. Nov 2019
    1. We assessed species interaction patterns via complex network analyses and used four complementary metrics known to vary geographically and reflect community-level responses to major drivers of biodiversity patterns, such as productivity, climatic seasonality, and historical climatic stability [e.g., (14–16)]

      Differences in geography affects the interaction patterns developed between species. Climate change, differences in species richness, and human impact was shown to dictate the types of networks that dominated those areas

    2. modular [subsets of species interacting preferentially with each other, forming modules of highly connected species

      Modular networks are groups of species that preferentially interact with each other. In Figure 1B, each module is represented by a distinct color.

      Connectance measures the proportion of interactions taking place in a network out of the total amount of possible interactions. The authors calculated a high connectance within each module, meaning the bird and plants species utilizing the majority of available interactions.

    3. The novel network was nested [specialist species interacting with proper subsets of partners of the most generalist species

      Networks such as seed dispersion networks consists of specialist species (which interacts with only a few, select species) and generalist species (which interacts with a broad range of other species). When a specialist interacts with one of the same species that a generalists interacts with, it is called a nested network.

      In Figure 1A, the specialists species are depicted as very thin rectangles to represent the few interactions they have with other species, whereas the generalist species are bigger rectangles to encompass the many interactions they have with other species. One example of a nested network is shown between the specialist animal at the bottom of the animal column interacting with the same plant that a generalist animal species, like the top rectangle of the animal column, also interacts with.

    4. Thus, although introduced birds are critical for seed dispersal in the ecosystem, they are primarily dispersing introduced plants (only 6.7% of interactions involved native plants).

      The authors concluded that the majority of plants and animals involved in the seed dispersion networks of O'ahu are introduced species, and that the majority of seeds being dispersed by these birds are from introduced plant species.

    5. Oʻahu, in particular, is among the areas most affected by extinctions and biological invasions in the world (12)

      In a 2010 Hawaii statewide assessment of forest conditions and trends, a map illustrated that major vegetation types for multiple islands , especially O'au, experienced severe changes in comparison to before the arrival of humans.

    6. By contrast, the architecture and stability of novel interaction networks across spatial scales and how they compare to native-dominated communities remain virtually unknown. This knowledge gap hampers our ability to forecast and mitigate the impacts of extinctions and invasions on ecosystem functions

      The authors note that research in the field has been limited to interactions between local species, neglecting the networks involving new, introduced species. Understanding the latter point will aid in efforts combating negative effects on ecosystems.

    7. Previous studies have focused on native-dominated communities in which few or no invasive species occur and mutualistic partners have interacted for prolonged periods of time, developing complex and often coevolved interactions (8, 9).

      Bascompte, Jordano, ant Olsen investigated coevolutionary interactions across a wide range of locations, measuring the levels of dependence between various species of plants and animals.They showed that most of these interactions are asymmetric- meaning that one species depends more heavily on the relationship than the other. This asymmetry supports the growing diversity and coexistence of multiple species in an ecosystem.

    8. As a result, “novel communities” have emerged, characterized by a reshuffling of species, changes in species interactions, and, in some cases, alteration or disruption of ecosystem services maintained by these interactions (3, 4)

      Brodie et. al reviews the concept of secondary extinction, the idea that the extinction of a species, caused by human activity, can lead to the loss of additional species.

      Below is a diagram from the review depicting different types of secondary extinctions. Co-extinction is when the direct impact of humans (red arrow) leads to the loss of one species, causing the loss of another species, which can then cascade into a series of extinctions. Human activity (yellow arrows) also affects interactions between species (grey arrows).

    9. multiscale analyses

      Studying a subject at both the local and regional levels

  2. Jul 2019
    1. This would include outplanting commonly consumed native plants (e.g., Pipturus albidus) within plant restoration areas, removing commonly consumed introduced plants in sites with high densities of native fruits, and attracting (e.g., via playback) specific frugivores to restoration sites

      Researcher Sean McDonald placed speakers playing non-native bird calls near native plants in danger for extinction in hopes of attracting these birds to these plants and increasing seed dispersal.

      Read more in Inside Science: https://www.insidescience.org/news/playing-birdsongs-save-trees

    2. For example, in Hawai‘i, large frugivorous birds are absent, resulting in a lack of dispersal of large native fruits (38)

      Islands suffer significant losses of large frugivorous birds due to their small size, isolation from mainlands, limited amount of species. These large birds tend to be flightless (making them an easy target for predation) and make it possible for large seeded plants, particularly trees, to be dispersed throughout the island.

      More information about the causes and consequences of large frugivorous bird extinction can be found in the Forbes article: https://www.forbes.com/sites/grrlscientist/2018/10/13/does-it-really-matter-if-just-one-species-goes-extinct/#48e3b358610b

    3. Therefore, functional characteristics (e.g., beak, seed, and fruit sizes) and species abundance (39) may be more important in the structure of mutualistic networks than species identity, supporting the role of ecological fitting (40)

      This study found that phenotypical traits such as the size of a bird's beak and the fruit's diameter, were strong factors that determined the likelihood of different pairwise interactions, along with species abundance.

    4. We found that specialization, modularity, nestedness, and the simulated robustness in all scenarios to species loss of the O‘ahu networks overlapped with the range of values observed in other networks.

      The results from the simulated extinction, along with the measurement of network factors (modularity, nestedness, and specialization) were all similar between Ohau and other tropical or non-tropical locations.

    5. We assembled and analyzed a dataset of 42 avian SDNs encompassing a broad geographical range, with data from islands (n = 17) and continents (n = 25) in tropical (n = 18) and nontropical (n = 24) areas (table S12). Although some of the other SDNs in the analyses included introduced species [e.g., (7, 34)], SDNs on O‘ahu present an extreme case of dominance by introduced species (>50%), coupled with extinction of all native frugivorous birds

      The authors surveyed data from seed dispersal networks across a variety of habitats, noting that the O'ahu was unique with the majority of its population being mostly made up of introduced species, with the original bird species of the island going extinct.

    6. High interaction dissimilarity has also been reported in specialized, native-dominated pollination networks, even between spatially close networks (33)

      D. Carstensen and others quantified the variability of interactions between plants and pollinators across different spaces. They found that these interactions vary greatly between different locations due to the abundance of species, which determined the likelihood of partners interacting with each other.

  3. Jun 2019
    1. Thus, plant-animal networks appear to have distinct links (high interaction rewiring) even when the same species are present in both sites, irrespective of whether networks are dominated by native or introduced species

      The authors conclude that plant and animals at different sites across the island develop their own unique pattern of interactions, even if the sites populated mostly of native or novel species.

    2. We decomposed this metric into two components: species turnover (βST—the proportion of interactions that are not shared owing to differences in species composition between two networks) and linkage turnover [βOS, also called rewiring—the proportion of interactions unique to a single network despite the occurrence of both partners in both networks (30)

      The authors measured the overall dissimilarity between different locations by two factors:

      species turnover- when two locations do not share similar networks because they are inhabited by different species,

      and linkage turnover- when species found in both locations develop different interactions specific to their site

    3. The wider variety of partners used at the larger scale (regional network) corresponds to the “fundamental niche,” whereas the subset of partners found at local scales indicates that local populations have much more restricted “realized niches” (27, 28).

      A species' fundamental niche encompasses all of the possible roles it has in its environment, whereas the realized niche are the actual roles that a species plays in its environment, taking into account competition, predation, and other interactions with neighboring species.

      The video below further explains this.

    4. Here we show that the interaction patterns recurrently identified in native-dominated networks also emerge in novel mutualistic networks composed of species with little or no shared evolutionary history. This result indicates that prolonged shared evolutionary history is not necessary for the emergence of complex network structure

      The authors concluded that species do not necessarily have to be evolutionary related to form a mutual relationship. This conclusion was based on their results demonstrating that introduced species on the island successfully formed beneficial interactions with native and other species that shared little phylogenetic similarities.

    5. Several studies suggest that the phylogenetic relationships of species contribute to structuring mutualistic networks

      Normally depicted as the "tree of life" (shown below), the phylogenetic tree traces the genetic lineage of organisms over time. Two species share a phylogenetic relationship when they share a common ancestor.

      The authors of the cited paper found that phylogenetic relationships can influence the type of networks species build and explain the type of species involved in these interactions.

    6. Furthermore, partner sharing (how distinct species share resources) in SDNs on Oʻahu is structured in a complementary way among bird and plant species, giving rise to distinct modules in which certain birds and plants interact preferentially. The emergence of such structures indicates that these novel SDNs largely reproduce the well-known patterns exhibited in mutualistic networks (18) and that SDN structure is highly conserved, regardless of variation in plant and bird communities.

      The reason the introduced birds and plants integrate successfully into the ecosystem of O'ahu is because they follow the same strategies that the native plants and birds developed: creating beneficial relationships with specific species, and carefully sharing the resources of the island with other organisms.

    7. Consequently, high connectance and nonmodular structures are expected, because both are linked to low specialization [e.g., (14, 23)]

      Dalsgaard and colleagues found that tropical areas have a lot of bird species that are obligate frugivores, meaning that they only eat fruited plants. Because fruit is there sole diet, these birds interact with a large variety of plants to ensure that they're consuming enough food to live.

      This type of behavior is commonly associated with a low specialized network because the birds are not displaying any preference towards any particular plant(s). When the obligate frugivores eat from a wide variety of plants, they are utilizing the majority of interactions available in their ecosystem- demonstrating high connectance. There are also no particular groups of plants that the frugivores specifically associate with, an example of a nonmodular structure.

    8. niche broadening

      A niche is an organism's role in its ecosystem, describing how it utilizes the resources and interacts with living and nonliving factors of its environment.

      Niche broadening is when a species expands its roles in its habitat, as a tool for survival.

    9. For example, both fleshy-fruited plants and frugivores on islands tend to have wide niches owing to resource limitation

      Traveset and colleagues observed that bird-plant interactions on the Galápagos islands are highly generalized, meaning the birds developed relationships with a wide variety of plants, and vice versa. These broad interactions offer more opportunities for species to gain food. However, the authors also warn that these additional interactions promote the reproduction and survival of invasive plant species, at the cost of native species.

    10. interaction release

      In response to lack of food and increased populations, animals broaden the scope of species they interact with beyond their original interactions.

    11. The statistical significance of the observed topological patterns was assessed by contrasting observed values for each metric with the confidence interval from null models (13)

      To determine if an observation is a consequence of a measured phenomena, and not by chance, researchers must test (and reject) the null hypothesis. A null hypothesis states that a result or observation is due by chance, and so should be disregarded as insignificant.

      In this case, the authors test the significance of the identified patterns in the network by comparing these values to a null model, a generated collection of values randomized to produce a pattern based on no ecological mechanism (Gotelli and Graves, 1996). If the observed values differ from the range of null values defined by the null model's confidence interval, they are considered significant.

    12. To what extent are introduced species integrated into seed dispersal networks (SDNs), and do introduced dispersers replace extinct native animals? To investigate these questions, we examined interactions based on 3278 fecal samples from 21 bird species [tables S1 to S3 and (13)] collected over 3 years at seven sites encompassing broad environmental variation across Oʻahu (fig. S1 and table S1).

      The authors wanted to figure out how many new plant/animal species are being incorporated into O'ahu's ecosystem through the dispersion of plants' seeds by animals. They also wanted to determine if non-native animals are responsible for this distribution.

      Over the course of 3 years they collected poop samples from 21 different birds found in 7 different locations across the island of O'ahu. The supplemental figure 1 and table 1 describe the 7 locations' average rainfall, coordinates, and elevation to demonstrate the diversity of these areas. Another set of tables listed the different species and plants (introduced and native) found at each site.

    13. frugivores

      An animal that eats primarily fruit

    14. Most native Hawaiian forest plants are bird-dispersed, yet no native dispersers remain in most ecosystems (10, 11). Thus, seed dispersal is almost entirely dependent on a handful of introduced vertebrate dispersers, nearly all of which are birds (10, 11).

      The introduction of novel seed dispensers (aka birds) is an important factor regarding the survival of native Hawaiian plant species. One study showed that the distribution of seeds from native plants are becoming increasingly dependent on not native, but foreign birds. C. Chimera and D. Drake also found that these introduced birds tended to spread more seeds from non-native plants rather than native plants.

    15. Mutualistic plant-animal networks are particularly susceptible to species loss (5) and invasions (4, 6, 7)

      A mutualistic network is a beneficial partnership between organisms. Disturbances to that relationship, like from one of the organisms becoming extinct, or by the intrusion of another species, can be harmful for the original partners of that relationship.

    16. interaction dissimilarity

      When the behavior between species in one area differs from the behaviors between species in another location.

    17. introduced species

      Plants or animals not originally from that area

    18. novel interactions

      A new relationship or pattern of behavior between plants and animals.

    19. seed dispersal

      The distribution or spreading of seeds throughout an area

    20. This high degree of similarity between novel and native-dominated networks suggests that the processes that structure interactions in such communities are largely independent of species identity and that ecological filtering occurs over relatively short (ecological) time, leading to functionally similar sets of players as compared with systems that have long evolutionary histories

      The authors concluded that novel species' interactions, developed over a relatively short period of time, still resemble much older interactions between native species.

    21. We estimated robustness of animals to the extirpation of plants (assuming bottom-up control) and robustness of plants to the extirpation of animals (top-down control). We simulated two scenarios, one in which order of extirpation was random and another—more extreme—scenario in which order was from the most generalist to the most specialist species. After using a null model correction on each metric to account for variation in sampling intensity and network dimensions across studies (14), we compared the 95% confidence intervals for the O‘ahu networks with the global dataset.

      The authors designed hypothetical scenarios where generalist or specialist species in a network went extinct, then determined the severity of these extinctions by measuring the amount of additional species that would (theoretically) go extinct as a consequence.

      The use of a null model ensures that the results found by these simulations are not a coincidence, that is, not due by chance.

    22. binary

      Binary calculations are a straightforward form of measurement that states the presence or absence of an interaction.

    23. weighted

      Weighted networks assign some form of quantitative value, in this case frequency, as a measure of the interaction in a network.

    24. However, the lack of association between rewiring and examined factors indicates that birds and plants in the system are highly flexible and can switch partners, irrespective of abiotic conditions and the identity of species in the community.

      The authors found that neither abiotic (rainfall and elevation) nor biotic (invasive species) factors influenced the variations in plant and animal interactions measured from different sites with similar species populations.

    25. pecifically, interaction dissimilarity and the dissimilarity caused by species turnover were influenced by elevation and rainfall, but not by percent of introduced plant species (tables S6 to S9). This suggests that the environment indirectly influences interactions via effects on species distributions, including the distribution of introduced species.

      Results in the supplement section show that abiotic factors (rainfall and elevation) affected the composition of species found at a site, thereby creating different network interactions between sites.

    26. biotic factors

      Living parts of an ecosystem, in this case, invasive species on the island

    27. Abiotic factors

      Non-living parts of an ecosystem, such as elevation of rainfall

    28. Surprisingly, only 53% of the interaction dissimilarity was due to differences in species composition among sites (βST = 0.30 ± 0.09), whereas 47% was because pairs of species that interacted in one site did not interact in another site where they co-occurred (βOS = 0.27 ± 0.07; fig. S4

      Referring to figure 3, the majority of dissimilarity across sites was due to linkage turnover, represented as the grey bars. This means that even though the sites shared similar species, the interactions were different.

    29. [interaction dissimilarity (βWN) = 0.57 ± 0.11, mean ± SE; n = 21 pairwise sites; Fig. 3 and table S5], indicating that, on average, only 43% of interactions were shared between sites despite the most common bird and plant species occurring at all sites (tables S2 and S3)

      The authors measured high levels of dissimilarity across various sites of the island, depicted as the black/gray bars in the graph of Figure 3

    30. To examine interaction dynamics across sites and to test their association with environmental variables, we calculated the dissimilarity (interaction turnover) between pairs of networks, using data limited to species present in the networks.

      The authors compared the similarities and differences between species' interactions across different locations around the island, taking into account the unique environments of each site.

    31. Beckett’s algorithm
    32. We found that despite all interactions being novel and primarily involving introduced species, networks were structurally complex and notably similar between scales (local versus regional) and across sites.

      The authors concluded that overall, the complex network structures of island's ecosystem on both the local and regional scale remained the same, even though these networks were now infiltrated with invading plant and animal species.

    33. At the local scale, networks had low to intermediate connectance and, unlike the regional network, were not nested. Similar to the regional network, six of seven local networks were specialized and modular, presenting three or four modules (Fig. 2, fig. S3, and table S4)

      At individual sites, the authors again saw species mostly interact with only a subset of the total interactions available, with instances of specialized species interacting with birds/plants also found in networks of more generalized species.

  4. May 2019
    1. niche broadening

      A niche is an organism's functional role in its ecosystem. Niche broadening is when an organism expands this role to encompass more interactions, behaviors, and food sources to promote their survival.

    2. Oʻahu’s SDN included 15 bird and 44 plant species connected by 112 distinct links (Fig. 1)

      The authors identified 44 different plant species and 25 different birds in O'ahu. Figure 1 depicts each bird (left column) and each plant (right column) as rectangles. The lines connecting a bird to a plant represents a seed dispersal event.

    3. seed dispersal events

      The distribution of a seed by being eaten by an animal and later excreted in its waste.

    4. Hawaiʻi provides an opportunity to investigate the consequences of an extreme scenario of loss of native species and their replacement by non-native species.

      The survival of native plants on the Hawaiian island of Kauai are threatened from changing climate, invasive species, and destruction by feral pigs. Efforts led by the Plant Extinction Prevention Program (PEPP) are working towards saving these endangered species and preventing the loss of further species.

      Read more in the grist: https://grist.org/article/hawaiis-rarest-plants-are-in-crisis-meet-the-people-fighting-to-save-them/

    5. modular

      Organized into distinct, independent groups

    6. perturbations

      A deviation or disturbance from the norm.

    7. supergeneralist

      A species that interacts with multiple groups of species in ecological networks

    8. insular

      From an island

    9. archipelago

      A group of islands

    10. Anthropocene

      The current geological age where human activity is the dominant influence on climate change and the environment.