Jen Tinsman
(co-advised by George Amato, AMNH)
Dissertation abstract:
MadagascarŐs lemurs are the most endangered group of mammals in the
world, with 94% of species threatened with extinction. Forest loss is
one the greatest threat to these arboreal primates, but hunting,
habitat degradation, and climate change also threaten their survival.
Lemurs are a diverse group of more than 100 species; and their
ecological traits shape how species respond to anthropogenic pressure.
Incorporating knowledge of speciesŐ ecological niches and evolutionary
histories can contextualize threats and improve conservation
assessments. In this dissertation, I investigate what constitutes
suitable habitat for lemurs in light of the threats present, their
sensitivity to forest fragmentation, their dispersal ability, and their
ecological uniqueness.
I obtained data about lemur distributions in two ways. First, I
conducted field surveys of the Critically Endangered blue-eyed black
lemur (Eulemur flavifrons), which only occurs in the ecotone between
eastern rainforest and western dry forest in the Sahamalaza region. I
also surveyed the range of sister species, the black lemur (E. macaco),
which inhabits nearby eastern rainforest in the Manogarivo region. I
focused on areas that have not been surveyed recently and on the poorly
studied boundary between the species to collect observations from the
breadth of these speciesŐ ecological ranges. I also documented threats,
including incursions into protected areas, and collected fecal samples
to test whether whole genomes could be obtained noninvasively for
analyses of local adaptation in these species.
Second, I searched online databases and published literature for GPS
localities for all species of lemur. I used these records, along with
the ones collected in the field, to construct ecological niche models
for nearly all species of lemur using Maxent. For the blue-eyed black
lemur and the black lemur, I estimated the remaining area they can
occupy based on these models and the threat survey data. Next, I
examined the role of not just forest loss, but forest degradation, in
determining where lemur species occur. I used high-resolution forest
cover maps to determine lemursŐ tolerance for characteristics of
degraded forest, including distance to the edge and mean patch size. I
then limited species niche model to only intact, forested habitat.
Lastly, using the sportive lemurs (genus Lepilemur) as an example, I
evaluate how the inability to disperse across large rivers has
influenced ecological niche diversity. I also examine what limited
dispersal ability will mean for these species as climate change causes
their ranges to shift.
Field surveys in the Sahamalaza and Manongarivo regions revealed
extensive threats to blue-eyed black lemurs, from traps to cattle
incursions and fire. I found no evidence of sympatry, but did locate an
undocumented population of E. flavifrons north of the Andranomalaza
River. Madagascar National Parks (MNP) managed protected areas appear
to have less human incursion than NGO-managed protected areas. Further
investigation of the ecological distinctiveness of these species is
possible via non-invasive methods: I sequenced whole genomes at 2.3x
coverage from eight of the fecal samples collected during this study.
While SNPs indicating a loss of function did not reveal any patterns,
sequencing additional samples could make studies of local adaptation
and population genetic diversity possible.
At the regional scale, forest conversion is a grave threat to lemurs.
When forest loss and degradation are considered in habitat models,
lemur species have lost 51% of their habitat in the last 30 years.
Proximity to a forest edge rendered more forested areas too degraded
for lemurs than did mean patch size. This result is likely the
influence of human contact nearer the forest edge. I recommend urgent
support for reserves like Beanka, Tsimembo Forest, Ranobe PK 32, and
AmoronŐi Onilahy, which have highly suitable, intact forest for many
lemur species. Spaces like these will be important for conserving the
remarkable diversity within the sportive lemur clade. Though their
distribution is largely explained by riverine barriers, I show a role
for ecological niche divergence and local adaptation in accelerating
allopatric speciation. These same rivers will limit their ability to
track climatically suitable areas as climate change progresses:
sportive lemurs as a group will lose nearly a quarter of their
accessible habitat to climate change by the 2070s.
While my results are focused on the particulars of lemur conservation
in Madagascar, the methods I have presented here are broadly applicable
to other threatened species. Piggybacking fecal sample collection onto
rapid field surveys is straightforward. The possibility of obtaining
whole genomes from non-invasive samples presents a new way to answer
questions about local adaptation without risking injury to other
arboreal study subjects, like Neotropical monkeys, or for elusive
species like big cats. For threatened species, their climatic niche
only dictates part of their distribution. The habitat quantification
pipeline presented here takes advantage of thirty-five years of
research in Madagascar to estimate speciesŐ tolerance for forest
fragmentation. While these records are impressive for primates, they
are dwarfed by those available for passerines, through scientific
literature and online repositories like eBird. By integrating field
surveys, ecological niche modeling, and non-invasive genomics, we can
begin to understand the complex threats facing species like lemurs and
the options for ensuring their survival.
Jen's website: http://www.jentinsman.com/