Chaz Hyseni, Research Assistant, collected genotype information from 8 loci for over 200 individual Great Tinamous, Tinamus major, a species of ground bird native to Central and South America. A project collaboration with Yale post-doctoral fellow, Patricia Brennan. The project aimed at measuring the levels of extra-pair paternity (EPP) in the nests of this elusive species. Results suggest that rates of EPP are high in this species, despite the fact that males provide all the parental care and would be expected to have high levels of paternity assurance.
Evolutionary genetics of CT populations of Alewife, Alosa pseudoharengus
|Alewife, Alosa pseudoharengus, populations occur in two discrete life
history variants, an anadromous form and a landlocked (freshwater
resident) form. Landlocked populations display a consistent
pattern of life history divergence from anadromous populations,
including earlier age at maturity, smaller adult body size, and reduced
fecundity. The project sought to answer
whether coastal Connecticut landlocked alewife populations are
independently evolved from anadromous populations or whether they share
a common freshwater ancestor, using mtDNA sequence and microsatellites. Further questions were directed at timing
the divergence between anadromous and landlocked populations, using microsatellite data to calculate the rate of evolution for foraging traits. This is part of a large long-term research project coordinated by David Post, and was part of Eric Palkovacs, Ph.D. thesis. Kirstin Dion, Yale Research Assistant, assisted with data collection and analysis.
Publication: Palkovacs, EP, KB Dion, DM Post, and A. CACCONE. 2008. Independent evolution of landlocked alewife populations and rapid, parallel evolution of phenotypic traits. Molecular Ecology, Volume 17: 582-597.
Genetic diversity of goldenrod as a potential determinant of insect community structure
Kelsey Kidd, Yale Forestry and Environmental Studies Master Student
Kelsey explored the relationship between dominant plant genetic diversity and insect species diversity in New England old-fields. For the project she sampled several old-fields in northeast Connecticut for leaves from the dominant plant goldenrod (Solidago rugosa) as well as insects. She found a significant negative correlation between S. rugosa genetic diversity and insect species diversity in the old-fields. This is somewhat contrary to current published literature on the topic of community genetics. These results give us some insight into how dominant plant genetic diversity may be shaping natural communities, as opposed to the manipulated communities used for previous studies in community genetics.
Molecular evolution of equine encephalitis virus and of the Lyme disease agent Borrellia burgdorferi
Annie Gatewood, Yale EPH graduate student
Annie Gatewood and another EPH student collecting ticks using a drag cloth
The projects aims to use molecular techniques to study the ecology and epidemiology of vector-borne and zoonotic disease agents. A rotation was completed in the MSCG Lab during Anne's first semester at Yale, where she worked with a dataset of eastern equine encephalitis virus sequences to learn techniques in sequence alignment and phylogenetic analysis. The training in the MSCG lab ultimately gave her tools and perspective that were not available in her own department and which valuable to her interdisciplinary PhD thesis on the molecular evolution and ecology of the Lyme disease agent Borrelia burgdorferi. She applied for a US Centers for Disease Control and Prevention grant for public health dissertation research in which the MSCG lab was included as a resource (“Landscape Genetics of Borrelia burgdorferi and Implications for Lyme Disease Emergence in Eastern North America”). Throughout her PhD at Yale, she continued to interact and draw on the lab’s unique expertise and resources for both formal training and informal feedback and brainstorming.
Genetic evidence supports song learning in the three-wattled bellbird Procnias tricarunculata (Cotingidae)
Vinod Saranathan, Yale EEB graduate student
Behavioural data indicate that, unlike other suboscine passerines, the three-wattled bellbird Procnias tricarunculata (Cotingidae) is capable of vocal learning. Procnias tricarunculata shows conspicuous vocal ontogeny, striking geographical variation in song, and rapid temporal change in song within a population. Based on analyses of mitochondrial DNA sequences and nuclear microsatellite loci, we conclude that genetic variation within and among the four allopatric breeding populations of P. tricarunculata is not congruent with variation in vocal behaviour.
Sequences of mitochondrial DNA control region document extensive haplotype sharing among localities and song types, and no phylogenetic resolution of geographical populations or behavioural groups, while microsatellite data document small but significant correlation with geographical distance, but no significant residual variation by song type. Estimates of the strength of selection that would be needed to maintain the observed geographical pattern in vocal differentiation if songs were genetically based are unreasonably high, further discrediting the hypothesis of a genetic origin of vocal variation. These data support a fourth, phylogenetically independent origin of avian vocal learning in the threatened Neotropical endemic, Procnias tricarunculata.
Publication: Saranathan, V., Hamilton, D., Powell, G.V.N., Kroodsma, D.E. & Prum, R.O. 2007. Genetic evidence supports song learning in the three-wattled bellbird Procnias tricarunculata (Cotingidae). Molecular Ecology, 16, 3689-3702.
Using DNA to understand the importance of mycorrhizal networks for the maintenance of species diversity
Michael Booth, Yale Forestry and Environmental Studies graduate student
Mycorrhizal fungi are obligatory plant symbionts of trees in forests with networks that connect the roots of trees and seedlings. These networks are thought to mediate overstorey-understorey competition and influence the rate and trajectory of forest succession. There are several different hypothesized mechanisms by which these networks might influence tree-seedling interactions, one of which hinges on the ideas that, A) seedlings that are networked are able to form symbioses with species of fungi that they would not be able to sustain on their own in the absence of overstorey trees, and B) fungal species associating with networked seedlings confer different growth and survival benefits relative to the ones that seedlings host without overstorey networks.
In the context of a large-scale manipulative experiment at Great Mountain Forest in NW Connecticut, we sequenced the ITS regions of fungi DNAs extracted from ectomycorrhizal root tips of naturally recruiting seedlings that were allowed to network with they mycorrhizas of overstorey trees or were prevented from networking with them.
Results of this work confirm the idea that networked seedlings host mycorrhizal fungi that are distinct from those hosted by non-networked seedlings but are similar to the mycorrhizal fungi on surrounding trees. Results also support the notion that as forests age from stand initiation through old-growth phases, mycorrhizal fungal communities undergo a succession of their own, presumably to changes in ecological selection pressures accompanying changes in tree demography.
The research project was performed in collaboration with Oswald Schmitz and Michael Booth who is now at the Institute of Arctic Biology at the University of Alaska, Fairbanks. This project gave rise to follow-up field projects in the Santa Cruz mountains and Interior Alaska and to growth-chamber experiments at the University of Mississippi.
Booth, M.G. 2004. Mycorrhizal networks mediate overstorey-understorey competition in a temperate forest. Ecology Letters, 7: 538-546.
Booth, M.G. & Horton, T.R. (in review) Mycorrhizal networks determine mycobiont diversity and composition on seedlings in a New England forest. Journal of Ecology.
Molecular techniques such as microsatellite analysis make it possible
to identify individual organisms and infer relatedness. We used these
techniques to evaluate the importance of kin level structure and
variation on the population ecology of wood frog, Rana sylvatica, in
the wild. Wood frogs are ideal organisms in which to conduct this
research because of the discrete nature of the breeding ponds and
larval habitat, the relatively brief generation time, and the fact that
many influential studies in population and community ecology have
already been conducted on these and similar pond-breeding amphibians.
This project is in collaboration with David Skelly (Yale Forestry School) and his group.
Halverson, M.A., D.K. Skelly, and A. CACCONE. 2006. Inbreeding linked to amphibian survival in the wild but not in the laboratory. J. of Heredity 97: 499-507.
Halverson, M.A., D.K. Skelly, and A. CACCONE. 2006. Kin Distribution among wood frog (Rana sylvatica) larvae in the wild. Molecular Ecology 15: 1139-1146.
Patterns of reproduction in a wild population of lemur Verreaux’s sifaka (Propithecus verreauxi verreauxi)
in southwest Madagascar
Richard R. Lawler, Yale Anthropology graduate student
Rich rotated through the MSCG Lab as part of his graduate training. During this time he learned various techniques pertaining to the study of “molecular ecology” including molecular cloning, nucleic acid extraction, PCR optimization for microsatellite loci, and automated sequencing.
His dissertation research focused on determining patterns of reproduction in a wild population of lemur Verreaux’s sifaka (Propithecus verreauxi verreauxi) in southwest Madagascar (see photo, below). His research combined genetic parentage analyses with information on anatomy, behavior, and demography, in order to discern the causes and consequences of differential reproductive success in a wild primate population. Dr Lawler is now an Assistant professor at Boston University. A complete description of Richard's research program can be found at: http://www.propithecus-verreauxi.com
Lawler RR. 2007. Fitness and extra-group reproduction in male Verreaux’s sifaka (Propithecus v. verreauxi). American Journal of Physical Anthropology 132: 267-277.
Lawler RR, Richard AF, Riley MA. 2005. Intrasexual selection in Verreaux’s sifaka (Propithecus v. verreauxi). Journal of Human Evolution. 48: 259-277.
Lawler RR, Richard AF, Riley MA. 2003. Genetic population structure of the white sifaka (Propithecus v. verreauxi) in southwest Madagascar. Molecular Ecology 12: 2307-2317.
Lawler RR, Richard AF, Riley MA. 2001. Isolation and screening of microsatellite loci in a wild lemur population (Propithecus v. verreauxi). American Journal of Primatology. 55: 253-259.