• 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

Linking Invasions and Biogeography

Dr. Jeremy Long
Dr. Jeremy Long
Northeastern University
Marine Science Center
430 Nahant Road
Nahant MA 01908
(781) 581-7370
e-mail author
 
Delivered at 2008 Boston Harbor Islands Science Symposium.

The role of native species diversity in providing biotic resistance to invasion remains controversial, with evidence supporting both negative and positive relationships that are often scale-dependent. Across larger spatial scales, positive relationships suggest that exotic and native species respond similarly to factors other than diversity such as island size and isolation. However, previous island studies examined only a few islands or islands separated by extreme distances. We surveyed exotic and native plant diversity on 23 islands separated by < 15 km in Boston Harbor. Exotic and native species richness were positively correlated. Consistent with island biogeography theory, species richness of both groups was positively related to area and negatively related to isolation. However, the isolation effect was significantly stronger for native species. This differential effect of isolation translated into exotic species representing a higher proportion of all plant species on more distant islands. The community similarity of inner harbor islands versus outer harbor islands was greater for exotic species, indicating that isolation had a weaker influence on individual exotic species. These results contrast with recent reports focusing on similarities between exotic and native species and highlight the importance of studies that examine invasion ecology using an island biogeographic approach.

Did You Know?

Soldiers of the 54th Massachusetts Infantry

The 54th Massachusetts Volunteer Regiment, depicted in the movie “Glory,” made a heroic return to Massachusetts via their discharge station at Gallops Island, part of Boston Harbor Islands National Recreation Area. More...