Conservation Biology of Lycaenidae (Butterflies) - IUCN

Conservation of North American lycaenids – an overview
J. HALL CUSHMAN and Dennis D. MURPHY
Center for Conservation Biology, Department of Biological Sciences, Stanford University, Stanford, California 94305-5020,
U.S.A.
Introduction
Two distinct patterns emerge when one examines the United
States' Endangered Species List. First, although butterflies
probably constitute less than 1 % of global insect species richness,
they are disproportionately represented on the list: 53% (14 of
26) of the insects currently afforded federal protection are
butterflies. Second, members of the Lycaenidae (including the
blues, coppers, hairstreaks and metalmarks) are
disproportionately represented: the family comprises only 21%
of the species-level butterfly fauna of North America (Scott
1986), but constitutes 50% of the listed butterfly taxa: see
Table 1, (Federal Register 1991a).
This over-representation of lycaenids also extends to the list
of candidate species awaiting protection, including some taxa
at risk of imminent extinction (see Table 2). For the U.S. as a
whole, lycaenids comprise 37% of all butterflies that are
candidates for listing as endangered species, and this number
rises to 49% if skippers (a group currently treated as a superfamily
distinct from the 'true butterflies') are excluded (Federal Register
1991b). In California, lycaenids are substantially overrepresented
among those taxa listed as candidates for federal
protection or known to be at particular risk, making up 10 of
those 20 taxa, whereas the state contains only a third of the
nation's lycaenid fauna (Murphy 1987a). In addition, the
candidates list is dominated by taxa from California and/or
Nevada, making up 71% of the candidates (20 of 28; Table 2).
They include a subspecies of Plebejus saepiolus (Boisduval)
(soon to be described) that is probably already extinct. Another
undescribed subspecies of hairstreak, Incisalia mossii (Edwards),
has been pushed towards extinction by overzealous collectors
who have removed hostplants and larvae. Also included is a
copper, Lycaena hermes (Edwards), that may be differentiated
sufficiently from all known relatives to warrant its recognition
as a monotypic genus. It has been extirpated in significant
portions of its historical range on both sides of the California-
Mexico border.
There are two opposing ways of viewing the lycaenid
dominance of endangered and threatened species, and the list of
candidates for this status. The first interpretation of this pattern
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is that it results from the biased study of U.S. butterfly families.
It may be that non-lycaenid butterflies are just as endangered as
lycaenids, but the latter have received more attention from
biologists, and thus more is known about their imperilled state.
While it is difficult to evaluate this contention, there are no
obvious reasons why lycaenids should have received more
attention than other families, given that they are small in size
and not nearly as showy. We favour a second interpretation,
which is that the patterns reflect ecological differences among
the butterfly families.
Here, we first provide a brief overview of the taxonomic and
geographic distributions of North American lycaenids. We then
discuss five interrelated characteristics of lycaenids that we
suspect are responsible for, or at least contribute to, the group's
extreme susceptibility to endangerment and extinction. We
conclude by summarising the ongoing efforts to conserve North
American lycaenids. Throughout the chapter, we focus primarily
on lycaenids and conservation programmes in the U.S. In part
this is a reflection of our experience with lycaenids in this
region. However, our restricted emphasis also occurs because
insect conservation in Canada and Mexico is far less developed
(see review by Opler 1991). Particularly in Mexico, a great
number of insect taxa are at risk, but specific details are lacking.
Taxonomic and geographic distributions
Lycaenids are somewhat under-represented in North America
and many of them just barely enter the United States from
Mexico. The subfamily Riodininae (the metalmarks) is especially
under-represented when compared to the equatorial latitudes in
the New World, with just 20 species (14%) in North America.
By comparison, riodinines make up about two-thirds of the
local lycaenid fauna in equatorial lowland communities of
South America. Indeed, the genera that include all but three of
the North American species – Apodemia Felder & Felder,
Calephelis Grote & Robinson, and Emesis F. – reach much
greater species richness to the south of the United States.
The subfamily Lycaeninae (the harvesters, hairstreaks,
coppers, and blues) is represented by more than 120 species,