• Lush vegetation on the top of Spectacle Island's North drumlin dominates the foreground. Boston's skyline can be seen in the distance.  The park's logo with tag line minutes away, worlds apart empashises the stark contrast between the city and islands.

    Boston Harbor Islands

    National Recreation Area Massachusetts

Island Biogeography & Population Genetics of Ground Beetles

Stephanie Madden
Stephanie Madden
Harvard College
e-mail author
 
Delivered at 2008 Boston Harbor Islands Science Symposium.

This study tested the hypothesis that dispersal capability influences colonization rates and patterns of diversity on islands, in accordance with MacArthur and Wilson's theory of island biogeography (1967). Ground beetles (Coleoptera: Carabidae) were collected on 7 islands and one mainland site at Boston Harbor Islands in the summers of 2005, 2006, and 2007 as part of the All-Taxa Biodiversity Inventory of the park. In total, we collected 98 species of carabid beetles in 39 genera.

Species richness increased with increasing island area, but was not associated with island distance from the mainland or level of habitat disturbance on the islands. Flight ability was associated with increased representation of carabids on more distant islands, but flight-capable species were no more widely distributed overall than flightless species. Overall, 14.3% of carabid species collected were non-native to North America.

Non-native species were no more widely distributed than native species, but were proportionally more abundant. A genetic analysis of 3 species on multiple islands revealed very homogeneous populations, suggesting that carabid beetles are fairly recent immigrants to all the islands. Habitat instability on the islands and low island carabid populations may cause repeated cycles of extinction and recolonization, resulting in a continuous turnover of populations.

Did You Know?

Sunset at the Boston Harbor Islands National Recreation Area

In the 1800s, when the Great Famine drove a million or more Irish citizens to immigrate to the United States, Deer Island was the landing point for thousands of refugees, many sick and poverty-stricken, hoping to reach the Port of Boston. More...