First day: Friday, Sept 1st
Last day: Friday, Dec 8th
Holiday: No seminar Thanksgiving week (Friday, Nov 24th)
Discussion Leader: S. Blair Hedges
Title: Is forest disturbance a problem for biodiversity?
Articles to be discussed:
Summary:
There are different viewpoints about whether forest disturbance is a problem for biodiversity. These two articles are not completely at odds but provide some contrast. Lugo argues that forest change and alien invasion is well underway and we should embrace it, because… it is not so bad after all. Alroy provides evidence that any disturbance of the original forest will lead to reduction in species diversity, and ultimately it is looking really, really bad.
Discussion Leader: Mark Walker
Title: Biodiversity patterns from a deep time perspective
Articles to be discussed:
Summary:
For this weeks seminar I would like to lead a discussion on biodiversity patterns from a deep time perspective. I've attached two short papers which look at patterns biodiversity across multi-million year long time scales; one focused on marine animals throughout the Phanerozoic and one on the Cretaceous radiation of epiphytic liverworts. Both attribute biodiversity increases in their respective taxa to different causes: using paleontological data Zaffos, Finnegan and Peters show that biodiversity in marine animals is correlated with continent fragmentation. Taking a phylogenetic approach, Feldberg et. al. attribute the rapid diversification of epiphytic liverworts during the late Cretaceous to biotic factors, specifically the creation of new ecological spaces by angiosperm trees.
The Cretaceous Terrestrial Revolution (KTR) and the Mesozoic Marine Revolution (MMR) witnessed a significant increase in global biodiversity. This pattern is well recorded across many taxa, including mammals, dinosaurs, marine reptiles, fishes, insects and flowering plants. Both papers present ostensibly different mechanisms to explain historical patterns of biodiversity, using different methodologies and from different ecosystems.
I’d like to discuss the results of both these papers in the context of drivers of global biodiversity- comparing and contrasting the evolution of angiosperm-dominated forests and continental fragmentation as engines of niche formation. Similarly, the converse would also be interesting to discuss- continental coalescence and forest disturbance as negative correlates in biodiversity. Is there anything inevitable about the upward trend in planetary biodiversity, or do we happen to live in (or close to) a biodiversity optimum? I’d also be interested in discussing the methods used in these papers, particularly those of Feldberg et. al., and the application of phylogenetic methods in understanding patterns of biodiversity.
Discussion Leader: JJ Smith
Title: Pyrodiversity
Articles to be discussed:
Summary:
Wildfires and planned fires swiftly and severely change the landscapes they burn. Fire is a fundamental component of certain types of ecosystems that rely on it as a predictable disturbance which renews the landscape. Many species have evolved strategies to cope with, or utilize the fire regime of habitats with periodic burns. Furthermore, a new area of study called pyrodiversity focuses on how the variation in intensity and occurrence of fires can spur biodiversity. However, large wildfires still pose a major threat to ecosystems, and there is discussion of how to best preserve the species affected. Human development has changed the fire regime of many areas: people are generally adverse to fires, but are responsible for the vast majority of wildfires. My three readings discuss some of the positive and negative impacts fires have on biodiversity.
Discussion Leader: Nick Huron
Title: What on Earth is Environmental Filtering and How Can it be Measured?
Articles to be discussed:
Summary:
Ecologists have long sought to understand the drivers of patterns of biodiversity across space and time. One popular approach for characterizing biodiversity at the ecological community level is known as community assembly. Traditionally, the factors that determine the structure of a community have been split into two categories: abiotic and biotic (sometimes further split into abiotic, biotic, and dispersal). These factors are described as filters that explain how species from a larger pool of potential colonizers are distilled down to those in a particular community. However, determining what factors drive community structure in empirical systems can be complicated.
I would like to discuss two papers (Cadotte and Tucker 2017; Carvajal-Endara et al. 2017) that examine one of these categories of factors, abiotic (or “environmental”). Please read Cadotte and Tucker 2017 first, as this paper outlines the problem of confirming that “environmental factors” drive community assembly in empirical systems. They offer a distillation of the definition of “environmental factors” that is truer to abiotic factors (environmental factors sensu stricto). Furthermore, they offer a framework for identifying cases of environmental factors (possibly both sensu lato and true abiotic factors) in empirical systems.
On the heels of the first paper is Carvajal-Endara et al. 2017, in which the authors suggest that Galapagos flora are more closely related than expected under null models and that this pattern is best explained by abiotic factors. In particular, they argue that abiotic factors have a stronger impact than dispersal capabilities. As you read this second paper, consider how closely the authors follow (or fail to follow) Cadotte and Tucker’s framework.
Lastly, come prepared to discuss how researchers might more accurately characterize ecological communities and the drivers that shape them!
Discussion Leader: Diana Lopez
Title: Assisted long range dispersal and its consequences to species biogeography
Articles to be discussed:
Summary:
Deforestation, habitat fragmentation, and climate change are some of the causes that are changing the distribution of species. However, have you ever considered how plastic and its non-biodegradable properties can directly influence the movement of species over long distances? We will discuss two papers that show how plastic marine debris are vectors for long-range dispersal of marine organisms and the consequences for species biogeography.
Discussion Leader: Michele Repetto
Title: Contribution of citizen science to biodiversity research
Articles to be discussed:
Summary:
Citizen science is a growing field that has received much attention as of late, however peer-reviewed articles utilizing volunteer collected data to address rigorous research questions are scarce. While numerous studies have shown that data from volunteers can be as reliable as from professionals, there remains stark skepticism of citizen science as science in ecology and other related fields. Public engagement can benefit science in a number of ways, such as cutting costs and stretching project funding further, in the sense of both time and effort. In tandem, the engagement of non-scientists in the scientific process serves to promote desirable societal outcomes such as scientific literacy, positive attitudes towards science, and buy-in for conservation objectives. Despite the potential benefits to both the scientific community and the general public, citizen science seems to still be lacking broad support and is perceived as a great outreach tool that is less useful for actually doing high-quality science.
In reading these articles, consider some of the barriers that exist for using data obtained through citizen science initiatives in high impact publications and how these may be overcome.
Discussion Leader: Mariana Bonfim
Title: Extinction and biodiversity: considering a sixth mass extinction event
Articles to be discussed:
Summary:
Global mass extinction events have historically reshaped ecosystems and biogeographical patterns. Historical evidence shows that mass extinction has led to increased cosmopolitanism in world’s biota that resulted in a “post-disaster” homogeneous characteristic fauna. These mass extinction events were, however, fundamental for determining patterns of macroevolution and speciation. Biologists now suggest that a sixth mass extinction may be under way in the Holocene, given the rate of species loss mostly as a consequence of anthropogenic impacts. In this week’s discussion, we will be considering two recent publication that contrasts evidence of past mass extinction impact and consequences to biodiversity, and future predictions that point to a “biological annihilation”. Has the Earth’s sixth mass extinction already arrived? What actions may we take to reduce or contain species loss on the long term?
Discussion Leader: Nick Huron
Title: Arguments and Clever Titles with Colons: Endeavors in Scale-Independent Functional Diversity (FD) Frameworks
Articles to be discussed:
Summary:
Firstly, I want to apologize for being the discussion leader that assigns three papers, but I assure you that the second two amount to five pages together (plus it is worth it). At the “request” of members of the biodiversity seminar (or natural stopping point in discussion today), I would like to look at ecological functional diversity.
Broadly speaking, functional diversity (FD) measures the breadth of trait states present across taxa at a particular ecological scale (often species in a community). FD metrics take advantage of morphological, physiological, and other measured traits that confer fitness differences among taxa and are associated with abiotic and biotic drivers of ecological structure. As such, FD can characterize biodiversity in light of trait differences and associated determinants of ecological organization. Most proposed FD metrics, however, fail to transfer well across different ecological scales. Carmona and colleagues propose a novel FD framework that is scale-independent, trait probability density (TBD). However, Blonder responds with a few considerations that were not addressed in the original paper. Carmona and colleagues get a chance to clarify their intentions in the third paper.
After the dust settles regarding the viability of TBD, are we confident in it as a FD metric? It is my hope that we will discuss the necessary components of any FD measurement to capture biodiversity and ascertain whether it is appropriate to use metrics like TBD to do so.
Discussion Leader: Diana Lopez
Title: Relationships between biodiversity loss and economic development
Articles to be discussed:
Summary:
Previously, we have touched the issue of biodiversity loss at a global scale. These two papers provide a few different perspectives on understanding whether biodiversity loss results from economic growth in terms of trade, land use, and greenhouse gas emissions at a global scale. The diversity in our class should spark some interesting conversation about per-capita expenditures and biodiversity footprints from different regions of the world!
Discussion Leader: Michele Repetto
Title: Hypotheses related to the latitudinal diversity gradient
Articles to be discussed:
Summary:
Lingering questions in global ecology and biogeography relate to patterns of species distribution and coexistence, particularly the pervasive latitudinal diversity gradient (LDG). Even if evolution produces more species in the tropics compared to the temperate zone (e.g., due to higher speciation rates and/or a longer evolutionary history), unless interspecific competition is always weak and communities are unsaturated, the question still remains: how can more species coexist at low latitudes than high?
These two papers investigate links between speciation and the latitudinal diversity gradient, and draw somewhat different conclusions. Hanley et al. find a strong and independent effect of latitude on the probably of in situ speciation and on the extent of diversification in freshwater endemic fish, while Schluter and Pennell found speciation rates to be highest where biodiversity is low and suggest that the biodiversity gradient was causing a gradient in speciation rates rather than vice versa.
Discussion Leader: JJ Smith
Title: Ecological Intensification of Agriculture
Articles to be discussed:
Summary:
Land used for agriculture has become increasingly intensified to meet the demands of the global human population. Both large and small-scale farms are pressed to produce more yield per area to extract the most value from their land. Further conversion of arable lands to agriculture and the intensification of existing farms have negative consequence for global biodiversity.
An alternative plan involving the intelligent management of natural resources to best support agricultural production is branded as “ecological intensification”. Proponents suggest that ecological intensification can combine beneficial conventional farming technologies and techniques with targeted conservation efforts to make farms sustainable and productive.
Kovsác-Hostyánszki et al. (2017) offer an review of the successes and shortcomings of ecological intensification efforts. Garabaldi et al. (2016) gives an example of how the support of local plant-pollinator communities can help close yield gaps between low and high productivity farms.
Discussion Leader: Mariana Bonfim
Title: Richness trends vs. Temporal turnover: exploring global homogenization
Articles to be discussed:
Summary:
Biotic homogenization is one of the dominant processes re-shaping global biota. Mostly in ecology, biotic homogenization at first referred essentially to the replacement of native by non-native species, or “increasing a few winners and reducing many losers” (McKinney and Lockwood 1999). This phenomenon is now more broadly recognized as the process by which ecosystems lose biological uniqueness, and it has been de-associated from only the limited measurement of species richness. Recalling to seminar discussions, this premise arouse many times, where we agreed in multiple occasions that richness itself might not be the best choice when assessing species loss and homogenization patterns. This week, I propose that we discuss two papers that focus on how to better measure that by focusing on species compositional changes temporally, and how a set of species turnover indices provide more information content regarding temporal trends in biodiversity. For discussion keep in mind how have you applied, have seen the application and/or could use these metrics to explore trends in biodiversity at different scales.
Discussion Leader: Mark Walker
Articles to be discussed:
Summary:
Oxygen is crucial for all animal life*, and it’s long been known that the diversity and evolution of animals closely mirrors the evolution of atmospheric and marine oxygen concentrations. Despite this, reconciling atmospheric oxygen with the paleontological record has been difficult compared to other molecules such as carbon or sulfur, owing to a distinct lack of temporal resolution in isotopic samples.
To remedy this situation, Edwards and colleagues (2017) have developed a more accurate way to measure atmospheric oxygen levels across deep time by utilizing the isotopic signature of photosynthesized carbon. Their results correlate the timing of a burst of atmospheric O2 to the Great Ordovician Biodiversification Event (GOBE). The GOBE is widely recognized as being the genesis of many of the most important marine families and genera from the Paleozoic to the present day, thereby suggesting a crucial role for atmospheric O2 fluxes in the development of Phanerozoic biodiversity.
The mid-Ordovician experienced a chill, as an ice age, comparable to that of the Quaternary, gripped the Earth. Using more conventional methods, Rasmussen et al. (2016) find evidence that this age ice started abruptly during the GOBE. They argue that changes in ocean circulation, and the development of upwelling zones and climate gradients, rather than atmospheric O2, triggered the radiation of marine taxa.
Do these hypotheses adequately describes the GOBE? Do rapid climate change and changes in O2 concentration describe other patterns of biodiversity throughout the Phanerozoic? Finally, the Ordovician ended with one of the greatest mass extinctions in the history of life- partially a consequence of carbon drawdown by plants. This would be a good place to discuss biotic drivers of biodiversity and biodiversity loss across deep time.
*There are a handful of bizarre amitochondriate animals which primarily inhabit deep sea, anoxic environments.