--

The Northwest Atlantic has become a notorious example of fishing down
marine food webs. It is also an uncontrolled experiment testing the
performances of marine populations under extremes of abundance. In this
talk I draw upon field experiments and long-term monitoring of two of the
region’s iconic commercial species - sea urchins and lobsters - to
illustrate how an altered food web is testing species performance under
demographic extremes. On one hand, depleted sea urchin populations have
failed to recover likely because they need large spawning aggregations to
reproduce, and the dense kelp beds that have resurged in the absence of
these grazers further inhibit larval recruitment. In contrast, the collapse
of top predatory fish, such as cod, has allowed lobsters to increase to
historic highs, such that crowding is evident from changes in habitat use,
shelter competition and heightened intra-specific predation. As conservation
measures are implemented in the region, fishery scientists
must seize upon these opportunities to understand population dynamics at
the poorly studied extremes of abundance.

The ocean is the largest living space in the world and covers at present 70.8% of the surface of the Earth. But we should really think of the ocean in terms of volume – around 1,370 million km3. Biodiversity cannot be likened to a simple list of species that inhabit a particular ecosystem. It is considerably more than a catalog or inventory, and in fact includes the entire set of relationships between living beings among themselves and with their environment. The physical consequences of osmotic flux (water and electrolytes) in the marine environment led living organisms to different strategies. The recognized species diversity in the ocean does not exceed 13% of all living species currently described – less than 250 000. This is very little, and may be explained for two reasons.
The first is that our knowledge, especially for deep zones and for microorganisms, various bacteria and protists is still only very partial, so we significantly underestimate oceanic diversity. New techniques, such as coupling between flow cytometry and molecular probes, are allowing us to discover extraordinary biological diversity. At present, widespread sequencing of the ocean water mass, "random genome sequencing" provides data that seems to be mostly unknown. The very recent Tara Oceans expedition's circumnavigation of the world's ocean provides us with valuable information on the abundance and variety of viruses, bacteria and mainly protists. For all prokaryotes and very small eukaryotes, molecular approaches (sequencing of 16S or 18S ribosomal RNA among others) bring surprising new information every day.

Schedule of the CES In-House Symposium

Abstract

Discerning spatial patterns of biodiversity and understanding their proximate and ultimate causes is central to biogeography and one of the key concepts in macroecology. Two of the best-documented spatial patterns of biodiversity are the latitudinal and elevational gradients in species richness. After more than a century of research on species richness along both gradients, we know that both ecological and evolutionary factors may drive the distribution of species along these gradients. While the influence of these factors on overall richness has been studied, their effect on the distribution of species as mediated by species-specific traits has received far less attention.

Different groups with varying life histories, traits and adaptations are likely to behave differently in response to their environment. For my study, I will examine the distribution patterns of different functional types of plants along elevational gradients. I will further examine how these patterns contribute to the plant species richness along the gradient. Species traits have also been shown to influence the geographic range size of a species. However, our understanding of how plant traits influence species elevational range size is still very poor. Hence, I will examine how plant traits interact with an environmental gradient to influence species range sizes. Such studies involving species range limits are important in the context of rapid climate change.

Theory posits that growth rate, fecundity and survival decrease towards range margins due to change in environmental conditions. But how these changes in environmental conditions towards the edges affect functional traits of species and how both factors together impose limitations on elevational range expansion is not well known.

Overall, my study will focus on both the patterns as well as the processes of distribution and diversity along elevational gradients.

--

--

This will be hands on informal workshop/practical on analyzing CTFS (Centre for Tropical Forest Science) data. Read the paper Chisholm et al., 2014, Temporal variability of forest communities: empirical estimates of population change in 4000 tree species, Ecology Letters, before coming to the workshop.

Large-scale data sets and sophisticated quantitative techniques are improving our understanding of forest dynamics globally. This talk will focus on the results of two Center for Tropical Forest Science cross-site analyses addressing two key questions: (1) What drives variation in tree species diversity in time and space? and (2) How does tree species diversity relate to ecosystem function? I will then continue on the species diversity theme by giving an overview of two new theoretical models we are developing: the first seeks to explain plant species diversity on small islands; the second provides estimates of undetected species extinction rates in Singapore and across the world in recent centuries. I will conclude with a discussion of the future of quantitative ecology research in Asia.

Darwin was troubled by elaborate male traits observed in many species that are seemingly maladaptive for survival, the peacock's tail being the most iconic of all. He wrote "The sight of a feather in a peacock's tail, whenever I gaze at it, makes me sick" because it challenged his theory of evolution by natural selection for adaptive traits. The extreme length of the tail may render a peacock more vulnerable to predation and therefore maladaptive for survival. He hypothesized that peahens may find the tail attractive thus enhancing male mating success. This idea led to the theory of sexual selection, wherein, traits that directly enhance mating success may be selected for, either through male-male competition for mates or through female-mate preference for elaborate male traits.

Male and female elephants in the proboscidean evolutionary radiation have had tusks and show extreme exaggeration in size and form. However, tusk in the Asian elephant (Elephas maximus) is sexually dimorphic as it is expressed only in the males, hinting at a possibility that opposing selection (sexual selection advantage to males and natural selection disadvantage to females) may have been the processes behind this pattern of tusk expression. Intriguingly, tuskless males (male dimorphism with respect to tusk) also occur at fairly high frequencies in some Asian elephant populations.

I hypothesized that sexual selection and artificial selection
(selective removal of tusked males from wild populations) on elephant tusks as possible mechanisms leading to the observed patterns of tusk dimorphism. I used mathematical models of population genetics, population dynamics, demography data and behavioural observations of wild Asian elephants in Kaziranga National Park, Assam, in an attempt to understand the evolution of tusk dimorphism in elephants.