There are two main hypotheses describing tree grass coexistence in savanna. The first of these was proposed by Walter (1970) suggesting that trees obtain their resources from deep soil layers while grasses are more shallow rooted. The second hypothesis was proposed by Higgins et al (2000) suggesting that trees are prevented from reaching mature size classes through insufficient rainfall or alternatively through fire and herbivory. Our research in the Kruger National park has allowed us to examine these two hypotheses more closely giving us a much broader mechanistic understanding of savanna systems. We now believe that the availability of water and nutrients not only determine grass biomass but also grass species composition. Whether these are in South America, Australia or in southern Africa savanna soils are limiting in nitrogen and phosphorous and this means that both grasses and trees are rooted in the same soil horizons where nutrients are highest.
Grasses rather than trees are superior competitors for these resources and grasses are not affected by fire frequency but fire frequency does control tree biomass. How then do trees survive among competitively superior grasses? Trees avoid competition with grasses by leafing out early and taking up nutrients before grasses are able. Trees are able to establish when grass biomass is low through drought or intense grazing. Funding for the manipulative experiments necessary to develop this understanding was not possible without the Mellon Foundation and here I reflect on how this understanding was achieved over the last 15 years.

Predators impact prey populations not only by consuming individuals, but also by altering their behaviours. These non-lethal effects can influence food web properties as much as lethal effects. We studied the interaction between three ungulate prey species and gray wolves (Canis lupus) at multiple scales. First we found that bison (Bison bison) did not avoid areas where wolves spend most of their time, but instead, adjust their foraging behaviour to the level of risk. Second we evaluated the spatial game between radio-collared caribou (Rangifer tarandus), moose (Alces alces) and wolves. Both caribou and moose use several responses to the passage of wolves, including an increase in selection for food-rich forest stands. For example, caribou selected conifer stands with lichen more strongly for nearly 10 days following the passage of a wolf. We also showed how spatial patterns in predation risk, experienced by prey in a human-altered landscape, depend on how the other prey species respond to the same disturbance. Overall, our analyses demonstrate how the predator-prey game involves behavioural adjustments to the expectation of what the other player is most likely to do in a heterogeneous habitat.

It is a great pleasure to invite you for photography exhibition at CES where we will display pictures taken by Ecology students during their field work.
Please visit and enjoy beautiful pictures with sips of tea/coffee. You are welcome to have discussions with photographers and listen to the stories behind these pictures, straight from the horse's mouth.

Will be uploaded shortly

Recent mass livestock mortality, known as dzud, have called into question
the sustainability of pastoral nomadic herding, the cornerstone of
Mongolian culture. A total of 20 million head of livestock perished in the
mortality events of 2000-2002, and 2009-2010. We examine mortality in 21
Mongolian aimags (provinces) between 1955-2013 to explain its density
independent cause(s) related to climate variability. We show that
livestock mortality is most strongly linked to winter (November-February)
temperatures. Additionally, we find prior summer (July-September) drought
and precipitation deficit to be an important trigger for mortality that
intensifies the effect of upcoming winter temperatures. Our density
independent mortality model explains 48.4% of the total variability in the
mortality dataset.

Volcanic eruptions have global climate impacts, but their effect on the
hydrologic cycle is poorly understood. We use a modified version of
superposed epoch analysis, an eruption year list collated from multiple
datasets, and seasonal paleoclimate reconstructions (soil moisture,
precipitation, and temperature) to investigate volcanic forcing of spring
and summer hydroclimate over Europe and the Mediterranean over the last
millennium. In the western Mediterranean, wet conditions occur in the
eruption year and the following 3 years. Conversely, northwestern Europe
and the British Isles experience dry conditions in response to volcanic
eruptions, with the largest moisture deficits in post-eruption years 2 and
3. The precipitation response strongly resembles the negative phase of the
East Atlantic Pattern. Modulated through this mode of climate variability,
eruptions force significant, widespread, and heterogeneous hydroclimate
responses across regions of Europe with diverse precipitation
seasonalities.

We present a tree-ring reconstruction of Upper Indus River watershed flow
using hierarchical Bayesian regression (HBR). One distinct advantage of
HBR is that we can use partial pooling of information across multiple
streamflow gauges allowing us to reconstruct streamflow across a watershed
network (seven gauges), including at stations where streamflow records are
too short to reconstruct using traditional methods. We do this by
explicitly modelling the covariance structure of streamflow residuals and
regression coefficients across different gauges. Additionally, using
Bayesian methods we can develop reconstructions for gauge records with
missing data, which may be interspersed through the length of the record.
Consistent with a prior study we find that current flows since the 1980s
are higher than average for past five centuries, but may be comparable to
streamflow during the mid 1500s and late 1600s.

Collective behaviour is a commonly observed phenomena which
encompasses a wide range of organisms – from swarming microbes to insects
to aggregation of whales. These groups which from through individual level
interactions exhibit interesting features like shifting from one form of
organization (for example a swarm) to the another (highly polarized). These
shifts are analogous to phase transitions in physical systems, and have
implications in ecology.

Phase transitions (shifts from one state to another) have been studied to a
great deal in physics and various fields of ecology, from lakes to corals
to semi-arid ecosystems. Scientists have developed statistical methods to
recognize and anticipate such shifts. Here we employ some of these methods
to check whether these generic statistical indicators of transitions which
sense shifts between ecological states, also capture signals in behavioural
transitions from one type of collective movement to another (e.g. swarm to
polarised group motion).

We discuss some possible biological motivations to investigate indicators
of transitions. Mass migration of animals is a process where some abiotic
factor (decrease in resources, change in climatic conditions, et cetera)
causes sedentary organisms to disperse to other parts of the world. This
process involves the movement of multiple individuals from a certain point
in space to another and also shift in the form of organization of migrating
animal societies (less polarized/random movement direction of individuals
in swarms to highly coordinated individual movement in groups).

Motivated by the above considerations, here, we simulate a simple agent
based model of the collective movement which generates a number of
biologically realistic grouping patterns through very simple local
interaction rules. We generate time series data of the group alignment by
varying the key local interaction parameters. We then generate a phase
diagram which shows how the state of the collective motion changes across
the key parameter value which we changed. Then, we use the time series data
which exhibit collective behaviour movement transitions to check for
distinct changes in the values of the statistical indicators. Based on the
change in the value of the indicator parameters prior to the shift in the
organizational pattern, we claim whether using these tools we can sense
imminent transitions or not in the time series data.

The time series that we had generated and used for the analysis, have shown
mixed results. We find changes in the values of the statistical measures
prior to the shift in states which inform us about the transition before
its onset. There were also scenarios where we obtained peculiar and also,
failed signals. Hence, these tools have some importance in their ability to
capture systemic changes prior to transitions in the states of collective
motion of animals but they are also not predictive of such events. Our
study suggests that it is worthwhile to test if these signals show similar
or some characteristic patterns before transitions in real animal group
movement data.

The terrestrial biogeochemical processes are perhaps the most dynamic and complex
component of the Earth’s Climate system. In order to better understand this complex system, the
integrated use of process-based modeling, remote sensing (RS) and measurements at multiple scales
(with an ecohydrological spirit) is proposed.
At the outset, a process-based ecohydrological model (BEPS-TerrainLab V2.0) that has tight
coupling of water (W), energy (E), carbon (C) and nitrogen (N) cycles is discussed as applied to a
forested ecosystem in boreal Canada. The potential errors in the simulated C fluxes under abstracted
hydrology are presented using a numerical experiment. Further, an improved and generic model
(STEPS) is presented as applied to a patchy-landscape in southern France. Improvements made
towards the modeling of canopy radiative transfer mechanism, in addition to some issues that are
pertinent to agro-ecosystems (C4 photosynthesis, irrigation, fertilizer N etc.) are presented. In the
second part of the presentation, long-term modeling of C in the soil and vegetation is discussed from
the lessons learnt from various projects in the Canadian C Program and the AmeriFlux programs.
Some studies on the long term ecohydrological responses under climate change in the lower
Himalayas are also discussed.
Finally, large-scale ecohydrological interactions are discussed. An analysis of the recent trends
in the global vegetation is explored using long-term RS data (AVHRR). Because of the importance of
soil water in governing the global vegetation, I hypothesize a major limitation in the widely used
global estimate of terrestrial photosynthesis (MOD17A2). A modeling strategy that is being developed
to improve the MOD17A2 by incorporating soil moisture data is briefly explained. In this regard, I
also present an analysis of some global soil moisture products obtained from microwave RS (SMOSL3
and AMSRE-LPRM) with respect to a reanalysis product (ECMWF).

The 90 My-old obligate and mutualistic fig–pollinator wasp system is exploited by parasitic non-pollinating fig wasps that are fig-species specific and oviposit into their hosts from the exterior of the fig which serves as a wasp nursery. Using Ficus racemosa as the study system, we investigated the underlying mechanisms employed by parasitic wasps to locate hidden hosts, where only cues from the exterior surface or from the interior of the fig could guide this search. We also determined the preference of different parasitic wasps for oviposition sites and hosts within the fig. We show, for the first time, that the fig wasp ovipositor is an olfactory sensor that responds to host volatiles and gaseous CO2. This sensor could be used by the parasitic wasps to evaluate ecologically relevant cues for oviposition. Chemical footprints left by previously ovipositing wasps also influenced oviposition choice. We found that physiological factors such as ageing and egg load greatly influenced oviposition behavior. These findings reveal the different ways in which parasitic wasps exploit their hosts but also have bearing on the survival of a plant–pollinator mutualism in such a complex and multiply-parasitized system.

Speakers

Prof. William Brown, SUNY Fredonia, USA 3-3:50 p.m. (including discussion)
Diptarup Nandi, CES 4:10-4:35 p.m. (including discussion)
Manvi Sharma, CES 4:35-5 p.m (including discussion)

Talk 1: The behavioral ecology of sexual cannibalism in praying mantids
William D. Brown, Department of Biology, State University of New York at
Fredonia
I will present work that my students and I have doing on sexual
cannibalism in the praying mantid Tenodera sinensis. Sexual cannibalism in
most predatory arthropods occurs when the female kills and consumes the
male before, during, or after copulation. The act obviously has strong
potential for generating sexual conflict but evolutionary models suggest
that degree of conflict over cannibalism will depend on the expected
mating frequency of males and additional offspring produced from the
resources obtain by cannibalism. Thus males are predicted to alter their
risk-taking during approach of females depending on perception of mate
availability and the fecundity benefits of cannibalism. I will present the
results of a series of experiments in which we examine the effect of (1)
level of predatory risk, (2) frequency of mating opportunities for males,
and (3) use of male soma for offspring production by females. I will also
discuss our current work assessing mating opportunities in the field, and
our future plans to measure natural mating frequencies and patterns of
paternity to more accurately assess the costs and benefits of falling prey
to a mate.

Talk 2
A sensory ecological perspective on mate sampling strategies: Models and
an empirical test
Speaker: Diptarup Nandi, CES
Abstract
Mating behaviour in animals often involves communication, wherein signals
are produced by individuals of one sex to attract members of the opposite
sex from a distance. Long-range communication signals thus play a central
role in mate search and mate choice in such systems. Among the different
aspects of mate choice, mate sampling has been less explored despite its
significance. Though analytical models of mate sampling have demonstrated
significant differences in individual fitness returns for different
sampling strategies, these models have rarely incorporated relevant
information on the ecology of signalers and sensory physiology of
receivers, both of which can profoundly influence the optimal performance
of a sampling strategy. In this study, we used simulation models to
compare the costs and benefits of different female mate sampling
strategies in an acoustically communicating field cricket (Plebeiogryllus
guttiventris), by incorporating information on relative spacing of callers
in natural choruses, their signal intensity and the effect of signal
intensity on female phonotaxis behaviour. The optimal strategy that
emerged reflected the physiological mechanisms of sound signal
localization (“passive attraction”) rather than active sampling. When
tested empirically in the field, female behaviour was also consistent with
the optimal strategy predicted.

Talk 3
Title: Oviposition site selection response to larval predation risk in
Aedes aegypti
Speaker: Manvi Sharma
Abstract
Animals ovipositing in discrete aquatic patches avoid patches with high
predation risk on their offspring. In nature, magnitude of larval
predation risk varies across patches yet this risk has mostly been studied
at one level of magnitude. We tested how a females of a mosquito species
Aedes aegypti assess a gradient in larval predation risk across
oviposition sites. To understand underlying trade-offs associated with
patch-selection decisions, we quantified consequences of possible patch
selection decisions by measuring larval survivorship across a predation
risk gradient. We find larval survivorship reduced drastically with
increasing predator density. Surprisingly, adult females did not reject
predator pools altogether, but reduced oviposition in “unfavourable”
pools. We suggest that larval predators may provide a release from intense
larval competition and that the interplay between larval predation and
competition may influence the nature of female-avoidance response to
larval predator densities. We also suggest that females make oviposition
decisions at pool network scale.

The film is about multi modal communication found among some rare &
endemic species of frogs found in “Western ghats”, India.
From time immemorial the graceful courtship behaviour of a peafowl has
inspired reams of poetic verses, some one with a sweet voice is always
compared to Indian Koel (a song bird) or perhaps the royal bengal tiger
represents everything that is majestic!
In this film the call of a frog is modelled in to syllables (known as
konnakol) used in the percussion instruments of Indian classical music.
That makes frogs as percussionists!
Equally fascinating is another weird behaviour - foot flagging found among
a certain species of frogs commonly known as dancing frogs. The film
throws some new light on to this behaviour buttressed by solid research.
The behaviour is similar to foot stomping among Sumo wrestlers.
Through “Wrestlers of western ghats”, the producer intends to encourage
the audience to develop fresh perspectives about the wonderful natural
world of which we are an inseparable part. The film is expected to fire up
the imagination of viewers - scientists and general audience alike.

All are cordially invited to watch the documentary and we will be having a
discussion session right after the movie screening.