Research

Conservation Genetics

Students interested in Conservation Genetics should contact me to discuss Independent Study Opportunities.bt-lily-pad-2

The focus of my research is the conservation of threatened and endangered tern species.  As a conservation geneticist I have employed molecular techniques to address ecological and behavioral questions pertinent to the conservation of Roseate Terns (Sterna dougallii)and Common Terns (Sterna hirundo).  My current work focuses on the Black Tern (Chlidonias niger) with the objective of elucidating population connectivity throughout the vast range of this species in North America and Eurasia.  Additionally we I am studying the mating system of Whiskered Terns (Chlidonias hybrida) in Poland.

Black Terns

Black Terns are members of the Family Laridae (gulls and terns) that breed in wetlands across significant portions of the United States, Canada, Europe and Asia.  Concern over widespread and significant declines in population size during the last century has inspired efforts to understand the cause of these declines.  While progress has been made in some areas, such as understanding the role of habitat quality and disturbance in population declines, important questions remain.

Dispersal rate and flyway definition are essential aspects of understanding population dynamics, and are pertinent to basic population biology, conservation planning, and to the recent concerns of human disease transmission by avian species.  Traditionally, dispersal rates of avian species have been estimated using mark-recapture techniques.  DNA techniques allow us to quantify the genetic variability within populations, which can then be used to estimate genetic exchange between those populations, sidestepping some of the difficulties of mark-recapture studies.

Black Tern incubating eggs at Smith Lake, Crescent Lake NWR, Nebraska 2006

Studies of North American Black Terns using mark-recapture methods have indicated these birds exhibit low site tenacity.  Because of their extensive distribution in North America, it is difficult to determine if the low rates of re-sighting are due to mortality or to dispersal of birds to other regions.  Analysis of genetic variability and dispersal patterns between Nebraska and Wisconsin are underway to determine levels of  differentiation between the two regions (Szczys & Shealer, in progress).

In contrast to the North American studies, anecdotal information from banded birds in Europe indicates there may be little dispersal between populations.  Knowledge of the degree of population subdivision in Eurasia is urgent as the populations are declining.  It is also vital to determine if these subpopulations use the same migration stopover sites or wintering areas along the African west coast.   These questions have direct conservation implications.  If dispersal rates are indeed low (population subdivisions are evident), park managers have a greater responsibility for protection of specific breeding sites, important stopover sites, and wintering areas.  Population size estimates also have direct consequences for the identification of Wetlands of International Importance under the Ramsar Convention on Wetlands.

In order to address these issues of population connectivity and wetland use in Europe, I initiated a collaborative effort with Dr. Jan van der Winden of The Netherlands.  Over the course of three to four years, we will sample birds from important regions in Eurasia.  Black Terns breeding in The Netherlands were sampled during the first year of the study.  Analysis of this population was essential because of the severe population reduction over the past 50 years.  Birds utilizing the large post-breeding staging site at Lake IJsselmeer (Netherlands) were also sampled in year one.  In year two of the study, we sampled birds breeding in Ukraine, situated at the southern border of the eastern edge of the Black Tern distribution in Europe.  The Ukrainian breeding population is declining, however, it is uncertain if this decline is local or part of a general decline in Eurasia. In year three of the study we sampled terns at the northern edge of the breeding range in Eastern Europe.  A visit (2009) to these wetlands was of utmost importance as we know little about current Black Tern population sizes and the threats they face in Eastern Europe. The breeding population in Lativa will serve as an important comparison with The Netherlands and Ukraine populations because Lativa still harbors extensive high quality wetland habitat as Ukraine does, but this is in direct contrast with the severely degraded wetland habitat in The Netherlands.  It is also likely that the Latvian birds utilize the Lake IJsselmeer stopover while  Ukrainian birds do not.p6130052

Common Terns: The objective of this project is to study the demographic and genetic consequences of a catastrophic event on a small, isolated population of the Common Tern (Sterna hirundo) on the island of Bermuda.

This population is isolated by 1,000-2,000 km from other populations of the species and comprised 15-20 pairs until 2003, when a hurricane eliminated all the adult males. A few young males have subsequently returned to the island and have started to breed. This event offers an exceptional opportunity to study the consequences of a genetic “bottleneck” from its outset, in a population that is effectively closed to immigration. The small size of the population, its location on small islets, and the tolerance of the species to intensive study, will allow the entire population to be studied in each year to determine social and genetic relationships among parents and offspring. This population had already been monitored for more than 30 years by my collaborator, providing a unique baseline data set.

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Previous studies revealed distinctive ecological features of the Bermudian population of Common Terns, including solitary nesting and unusual migratory habits. Preliminary studies in 2006 suggested that Bermudian Common Terns also differed in structural size from North American birds. This study will investigate whether the population also differs genetically, which might merit classification as a new subspecies and intensified conservation actions.

We are also conducting related ecological and genetic studies of the mainland population. If differences from the mainland population are found, this work will investigate relationships with other potential source populations, including those of the Azores Islands (Portugal) and Aruba (Netherlands Antilles).


Roseate Terns:

Common Tern pair copulating at Bird Island, MA 2005

Results from my dissertation work indicated that the endangered North American Roseate Tern population indeed has reduced genetic diversity when compared to a much larger breeding population in Western Australia. Roseate Tern The Harvard Museum of Comparative Zoology is home to approximately 30 Roseate Tern specimens

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collected in the Northeast Atlantic prior to a major population bottleneck in the late 1800s. I recently acquired toe pad skin from five of those individuals to determine if DNA extraction and PCR amplification are possible from museum specimens of this type and age. This study proposes to quantify the genetic diversity of this population prior to the population crash. If DNA isolation from these samples is adequate for microsatellite analysis, this could be a landmark study quantifying pre- and post-bottleneck genetic diversity and in fact implicating human persecution of a species directly with the loss of genetic diversity.