10/25/12

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I have investigated the metapopulation dynamics of ants and plants inhabiting four archipelagos of small islands in the Bahamas (encompassing >200 islands overall), documenting patterns of immigrations and extinctions and elucidating factors underlying turnover events.  I have studied this insular system since 1990.  Such long-term data sets are rare, yet extremely valuable, as some patterns in nature are only discernable over decadal time scales.

Over the first decade of this study, immigrations outnumbered extinctions, and species numbers slowly increased. This trend was reversed in the second decade, as extinctions outnumbered immigrations (although to a much greater degree) and species numbers decreased more rapidly than they increased in the first decade.  Similar patterns were observed for ants and plants.  Thus, these insular communities, when viewed over two decades, were in a disequilibrial state.  Five major hurricanes have affected one or more of my study areas over this period, most in the second decade of the study. Direct effects of hurricanes, however, do not appear to be responsible for the observed patterns.  Indirect effects of hurricanes, along with a long-term (quarter-century) increase in temperature in the region, may be the primary driving factors.
 

I am also interested in very small islands, which lack terrestrial vegetation entirely.  I have introduced two plant species to these islands, and found some introduced populations have persisted for over 15 years (and counting).  This demonstrates that such islands are not physically incapable of supporting plant life, but have no vegetation apparently due to barriers to colonization.

I have also studied the terrestrial invertebrates occupying very small islands lacking terrestrial vegetation.  Perhaps surprisingly, such islands contain relatively diverse arthropod faunas, encompassing several trophic levels.  These communities are entirely dependent upon the marine environment for energy inputs.  These very small islands hold insights into early successional processes, the base of insular food webs, and life in extreme environments.
 

Schoener, T.W., D.A. Spiller, and L.W. Morrison. 1995. Variation in the hymenopteran parasitoid fraction on Bahamian islands. Acta Oecologica, 16: 103-121.

Morrison, L.W. 1997. The insular biogeography of small Bahamian cays. Journal of Ecology, 85: 441-454.

Morrison, L.W. 1998. The spatiotemporal dynamics of insular ant metapopulations. Ecology, 79: 1135-1146.

Morrison, L.W. 1998. A review of Bahamian ant (Hymenoptera: Formicidae) biogeography. Journal of Biogeography, 25: 561-571. <PDF available> "This is an electronic version of an Article published in Journal of Biogeography, 25, 561-571"

Morrison, L.W. 2002. The geographic distribution of pubescence in the sea daisy, Borrichia arborescens, on Bahamian islands. Global Ecology and Biogeography, 11: 247-252. <PDF available>

Morrison, L.W. 2002. Island biogeography and metapopulation dynamics of Bahamian ants. Journal of Biogeography, 29: 387-394.<PDF available>

Morrison, L.W. 2002. Determinants of plant species richness on small Bahamian islands. Journal of Biogeography, 29: 931-941. <PDF available>

Morrison, L.W. 2002. Interspecific competition and coexistence between ants and land hermit crabs on small Bahamian islands. Acta Oecologica, 23: 223-229.

Morrison, L.W. 2003. Plant species persistence and turnover on small Bahamian Cays. Oecologia, 136: 51-62.

Morrison, L. W. 2005. Arthropod diversity and allochthonous-based food webs on tiny oceanic islands.  Diversity and Distributions, 11:517-524.

Morrison, L. W. and D. A. Spiller. 2006. Land hermit crab (Coenobita clypeatus) densities and patterns of gastropod shell use on small Bahamian islands.  Journal of Biogeography, 33:314-322. <PDF available>

Morrison, L. W. 2006.  Mechanisms of coexistence and competition between ants and land hermit crabs in a Bahamian archipelago. Acta Oecologica, 29:1-8.

Morrison, L. W. 2006.  The ants of small Bahamian cays.  Bahamas Naturalist and Journal of Science, 1(2):27-32. <PDF available>

Morrison, L. W. and D. A. Spiller. 2008. Patterns and processes in insular floras affected by hurricanes. Journal of Biogeography, 35:1701-1710. <PDF available>

Morrison, L. W.  2010.  Long-term non-equilibrium dynamics of insular floras: A 17-year record.  Global Ecology and Biogeography, 19:663-672.

Morrison, L. W.  2010. Disequilibrial island turnover dynamics: A 17-year record of Bahamian ants.  Journal of Biogeography, 37:2148-2157.

Morrison, L. W.  2011. Why do some small islands lack vegetation? Evidence from long-term introduction experiments.  Ecography, 33:384-391. <PDF available>

Morrison, L. W.  2012. Island flora and fauna: equilibrium and nonequilibrium. In: The Balance of Nature and Human Impact, K. Rohde (ed.), Cambridge University Press, in press.

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