Evolutionary and Behavioral Ecology
Our lab is involved in a series of projects in collaboration with PI’s from other laboratories working on evolutionary ecology projects. Our main input is to provide support for the collection and analyses of genetic data.
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 frogs (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 D. Skelly (Yale Forestry School) and his group.
Phylogeography and Phylogenetics
Our lab continues to be involved in a variety of projects aimed at understanding the evolutionary patterns underlying the spatial and temporal structuring of genetic variation, especially in recently diverged taxa from insular systems, including islands and other isolated system such as caves. We are integrating genetic studies with morphological data, life history traits, and data from recently extinct taxa. The selection below shows a partial list of the projects in this area.
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. We are using mtDNA sequence and microsatellites to ask
whether coastal Connecticut landlocked alewife populations are
independently evolved from anadromous populations or whether they share
a common freshwater ancestor. We are also interested in timing
the divergence between anadromous and landlocked populations using
microsatellite data to calculate to calculate the rate of evolution for
foraging traits. This project is part of a large long-term research
project coordinated by David Post, it was part of Eric Palkovacs, Ph.D. thesis. Kirstin Dion (EEB) collected data for this project.
Molecular phylogeny and historical biogeography of the land snail genus Solatopupa (Pulmonata) in the peri-Tyrrhenian area
The land snail genus Solatopupa consists of six species and has a peri-Tyrrhenian distribution; most of the species have a very narrow range and all of them except one (Solatopupa cianensis, which inhabits porphyritic rocks) are strictly bound to calcareous substrates. One species (Solatopupa guidoni) is limited to Sardinia, Corsica, and Elba Island. Because the potential for dispersal of these snails is low, the insular range of this species has been traditionally related to the Oligocenic detachment of the Sardinia–Corsica microplate from the Iberian plate and its subsequent rotation towards the Italian peninsula. In this study, we used sequences of three mitochondrial and one nuclear gene to reconstruct the evolutionary history of the genus. Our phylogenetic results are consistent with the genetic relationships found using allozymes, but contrast with the phylogenetic hypotheses based on karyology and morphology. Molecular clock estimates indicate that the main cladogenetic events in the genus occurred between the middle Miocene and the middle-late Pliocene. Patterns of phylogenetic relationships and geological considerations suggest that the cladogenesis of the genus can be explained by vicariant (tectonic) processes. Our datings do not support a causal relation between the split of S. guidoni from its continental sister taxon and the initial phases of the detachment of the Corsica–Sardinia microplate from the mainland. On the contrary, time estimates coincide with the very last phase of detachment of the microplate (from 5 to 3 Myrs ago). Overall, our molecular clock estimates are in good agreement with the latest geological views on the tectonic evolution of the peri-Tyrrhenian area. (pdf)
The genus Triturus is a problem for taxonomists. One member, the Southern Crested Newt, has been classified eighteen different ways. The monophyletic origin of European newts within this genus, family Salamandridae, has for decades rested on presumably homologous characters from behavior and morphology. Molecular data challenge this hypothesis, but the phylogenetic position of Triturus newts within the Salamandridae has not yet been convincingly resolved. We addressed this issue and that of the temporal divergence of Triturus within the Salamandridae with novel Bayesian approaches applied to DNA sequence data from three mitochondrial genes (12S, 16S and cytb). Using the molecular phylogeny we map the evolution of life history and courtship traits displayed by Triturus species. Given that their evolution is best explained by multiple independent evolutionary gains, we suggest that new conceptual and experimental approaches are required to explain how complex courtship traits, for a long time assumed to be homologous, might have evolved in parallel. This work is in collaboration with Saverio Vicario and Sebastian Steinfartz, former members of the lab.
Connecticut is home to two species of Bufo toads: Bufo americanus and Bufo fowleri. Bufo species are found throughout North America and commonly hybridize in nature. Our study aims at understanding the molecular phylogenetic relationships among Bufo americanus and Bufo fowleri in Connecticut. How does their mtDNA compare to their morphology with respect to phylogenetic inference? What is the phylogenetic relationship between Bufo toads in Connecticut to Bufo toads in the rest of their United States range? This project is in collaboration with Greogory Watkins-Colwell, of the Yale Peabody Museum.
Twenty years ago the field of ancient DNA was launched with the publication of two short mitochondrial (mt) DNA sequences from a single quagga (Equus quagga) museum skin, an extinct South African equid (Higuchi et al. 1984). This was the first extinct species from which genetic information was retrieved. We have isolated DNA from eight quaggas and an extinct population of the plains zebra (Equus burchelli burchelli). We show that the quagga displayed little genetic diversity and very recently diverged from the plains zebra, probably during the penultimate glacial maximum. This emphasizes the importance of Pleistocene climate changes for phylogeographic patterns in African as well as Holarctic fauna. This work is in collaboration with Scott Glaberman (Graduate Student EEB) and many US and international scientists.
Extinct dwarf elephants from the Mediterranean islands
Extinct giant and dwarf deer of Crete
One of the most interesting problems in paleontology is the occurrence in the Quaternary of a rich fauna of endemic dwarf and giant species of vertebrates on several Mediterranean islands, including Sicily, Sardinia, Malta, Tilos, Cyprus, and Crete. In Crete, elephants, hippos, cervids and murids changed; generally, smaller animals increased in size whereas larger animals decreased in size. This project focuses on one of these groups, the deer. Their evolution on Crete is more complex, with greater variation in size and morphology than in any other vertebrates that made it to the island. Different named taxa (5-8 different species) ranged in size from animals as large as a caribou or a small elk to specimens similar in size to a dik-dik or a muntjac. We are proposing to take advantage of the ability to of extract DNA from dated dental and bone remains to produce a molecular phylogeny of the extinct cervids of Crete. For comparative purposes, we also will include DNA sequences of several mainland extinct and extant species. This phylogenetic approach will help us address a series of questions regarding their phyletic relations with the mainland fauna, and the patterns and timing of colonization of Crete (i.e., Are the different named taxa distinct phyletic lineages? Which colonization model do the genetic data support? Did the lineage(s) of Cretan deer originate from one or several mainland species? This work is in collaboration with Nikos Poulakakis, D. Reese (Yale Peabody Museum) and the group of R. Fleischer from the Smithsonian Museum of Natural History.