Reminder!!!
For YETI
Debabrata Phukon
---------- Forwarded message ---------
From: Madhavi Latha <madhavi@xxxxxxxxx>
Date: Sun, 22 Jul 2018, 1:06 pm
Subject: REMINDER: Open defense of PhD thesis by Aniruddha Marathe on July
23, 2018 (Monday) 11:30 AM
To: Madhavi Latha <madhavi@xxxxxxxxx>
You are cordially invited to an open defense of PhD thesis
*Species richness and distribution of ants (Hymenoptera: Formicidae) along
an elevational gradient in the Eaglenest Wildlife Sanctuary (Arunachal
Pradesh, India)*
By
*Aniruddha Marathe*
*PhD Scholar, ATREE *
Date & Time: July 23, 2018 (Monday) at 11:30 AM
Venue: ATREE auditorium
------------------------------
*Abstract*
Some of the most basic questions in ecology are 'How are ecological
communities assembled and maintained?' and 'Why are there more species in
some communities than others?'. Elevational gradients offer interesting
opportunities for answering these questions due to highly heterogeneous
environmental conditions across small geographic extent. The magnitude of
variation across elevations, in climate as well as species communities,
parallels that across latitudes, but lends itself more easily to studies
using primary data. Therefore, elevation becomes a proxy variable for a
large number of potential mechanisms driving ecological patterns. This
makes understanding patterns in species communities across elevations an
important objective in ecology.
My work attempts to understand patterns of ant species richness and
composition across an elevational gradient in the Eastern Himalaya. This
study is one of the first structured inventories of ants from the region.
The study contributes to growing literature on elevational patterns in ant
communities by filling a geographic void in the data. To explain the
variation in ant community properties, I compare the effects of climatic
gradients and other processes that potentially limit species pools across
entire elevation zones, with more local scale effects of habitat complexity
and micro-climate such as soil temperature, leaf litter volume, and canopy
cover. The analysis proceeds by explaining patterns in different properties
of the community such as species richness, elevational extents and species
composition.
Species richness decreased from 84 species at the lowest elevation to only
six species at the highest elevation. Most of the variation in species
richness was explained by climatic trends across elevation rather than
changes in local habitat conditions. Using a combination of simulation
models and GLMs, I show that the effects of climate were sufficient to
explain limits on species richness at higher elevation but not at low
elevations. Species richness at low elevations is most likely result of the
continuity between mountains and plains resulting in a mixture of species
from both zones. As this geographic transition is a common feature for most
of Eastern Himalaya, the result could be more widely applicable.
Variation in species composition between sites was due to combined effect
of three different properties of community, species richness, local
individual density, and biological properties of species. I arrive at this
conclusion by revisiting the relationship between species richness,
individual density, and beta diversity. This analysis suggests that the
mean of abundance distributions is an important variable, which has so far
been largely overlooked.
Patterns in elevational extents of species can arise in two different ways;
one, all the species respond to the environmental changes along elevation
in similar ways and the lowest elevation forms an important component of
the regional species pool. Alternatively, a competing hypothesis –the
‘climatic variability hypothesis’ or Steven's mechanism – suggests that
species with small and large ranges respond in different ways to
environmental variation. Between the two hypotheses, Steven’s mechanism has
so far been the focus of attention. However, both hypotheses generate
increase in elevational extents with elevation or the Rapoport's pattern.
Using a conceptual model, I show that the magnitude of the relationship
should be different among the two hypotheses. Further, the two models make
opposite predictions about nestedness where species composition at higher
elevations are subsets of lower elevations. I use the observed patterns in
ants to test both hypotheses. I point out that Rapoport's pattern cannot
reliably link the pattern with process, while nestedness is a much better
measure.
In the last chapter, I analyze changes in species composition across
elevations. I grouped ecologically similar species into functional groups
such as habitat specialists, generalists, and specialist predators. Here, I
discuss how the relative contribution of each group changes with elevation
and whether the distribution of species along the gradient is different
between groups
In this work, I identify effects of climatic gradients along with local
individual densities on ant communities, and segregation of species within
each local community driven by biological properties of ants. Based on the
elevational distribution data, range restricted tropical specialist species
form the most diverse ant communities in the Eastern Himalaya, which are
likely the most affected by rising temperatures due to climate change. The
results of this study along with other studies in future will help to
predict extinction threats, range shifts, and changes in community
composition.
------------------------------
*Tea/coffee will be served downstairs at 10:30 AM*
--
__________________________________________________________________
Madhavi Latha G
The Academy for Conservation Science and Sustainability Studies
Ashoka Trust for Research in Ecology and the Environment (ATREE),
Royal Enclave, Srirampura, Jakkur PO
Bangalore 560064, India
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Phone: +91-80-23635555 Extn: 121
Fax: +91-80-23530070
E-mail: madhavi@xxxxxxxxx
_________________________________________________________________
--
__________________________________________________________________
Madhavi Latha G
The Academy for Conservation Science and Sustainability Studies
Ashoka Trust for Research in Ecology and the Environment (ATREE),
Royal Enclave, Srirampura, Jakkur PO
Bangalore 560064, India
-----------------------------------------------------------------
Phone: +91-80-23635555 Extn: 121
Fax: +91-80-23530070
E-mail: madhavi@xxxxxxxxx
_________________________________________________________________