3.12 Insects
Teir presence on this monadnock landscape is indicative not only of the high quality of the habitats that currently exist, but of the continuity of those habitats and the ecologi- cal processes maintaining them throughout that immense span of time. Tis ability to maintain relict populations is shared with many rare plant species but is less typical for vertebrates. For these reasons, the presence of healthy populations of rare or habitat-specialist species of insects and other invertebrates is invariably an indication of a high degree of native eco- system integrity. Where high-quality natural areas exist and have maintained their quality through time, a signifcant diversity of insects and other invertebrates—containing both rare species and a high proportion of habitat specialists—should be expected. Although some species of invertebrates, like some plants, can maintain small relict popu- lations over large spans of time, most invertebrates require a distribution of habitats spread out over an entire landscape. Tis is especially the case for species prone to local extirpa- tion and that depend on a metapopulation structure for survival within a region. • A metapopulation is composed of a number of subpopulations, each of which may be relatively unstable, some increasing in a given year, others declining to the point of extirpation. As long as movement is possible between the sub-populations, declining populations can be “rescued” by immigration from increasing populations elsewhere within the metapopulation.
• A metapopulation can therefore be much more stable than its parts, at least as long as not all subpopulations are afected by the same set of events.
• Metapopulations are most stable when they are spread over a signifcant area of the landscape.
Conservation biologists are just beginning to realize how important metapopulations are for animals in general (for vertebrate examples, see McCullough 1996) . Due to the greater fuctuations their subpopulations experience within a given year or season, invertebrates are often dependent on metapopulation structures. Tis is especially true of species associated with ecosystems maintained by frequent disturbances, such as fre, storms, or foods. While vertebrates (and many plants) often have escape mechanisms for coping with unpredict- able ecological disruptions, invertebrates typically do not. Te only way many insects spe- cies survive in habitats maintained by frequent fre, for instance, is through recolonization of recently burned areas from unburned patches of habitat (Hall and Schweitzer 1993) . While recognizing that insects and other invertebrates may never be studied as fully as other species groups by preserve managers, Hall (1999a) makes the point that some atten- tion must be given toward their proper management if an ecosystem-based approach is the
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2015 NC Wildlife Action Plan
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